streamifier_cb(): Fix update of cur_stream_offset
[wimlib] / src / resource.c
index 49f37a3..192ffb2 100644 (file)
@@ -1,7 +1,7 @@
 /*
  * resource.c
  *
- * Read uncompressed and compressed metadata and file resources from a WIM file.
+ * Code for reading streams and resources, including compressed WIM resources.
  */
 
 /*
@@ -31,7 +31,6 @@
 #include "wimlib/error.h"
 #include "wimlib/file_io.h"
 #include "wimlib/lookup_table.h"
-#include "wimlib/lzms.h"
 #include "wimlib/resource.h"
 #include "wimlib/sha1.h"
 
  */
 
 
-/* Decompress the specified chunk that uses the specified compression type
- * @ctype, part of a WIM with default chunk size @wim_chunk_size.  For LZX the
- * separate @wim_chunk_size is needed because it determines the window size used
- * for LZX compression.  */
-static int
-decompress(const void *cchunk, unsigned clen, void *uchunk, unsigned ulen,
-          int ctype, u32 wim_chunk_size)
-{
-       switch (ctype) {
-       case WIMLIB_COMPRESSION_TYPE_LZX:
-               return wimlib_lzx_decompress2(cchunk, clen,
-                                             uchunk, ulen, wim_chunk_size);
-       case WIMLIB_COMPRESSION_TYPE_XPRESS:
-               return wimlib_xpress_decompress(cchunk, clen,
-                                               uchunk, ulen);
-       case WIMLIB_COMPRESSION_TYPE_LZMS:
-               return lzms_decompress(cchunk, clen,
-                                      uchunk, ulen, wim_chunk_size);
-       default:
-               wimlib_assert(0);
-               return -1;
-       }
-}
+struct data_range {
+       u64 offset;
+       u64 size;
+};
 
-/* Read data from a compressed WIM resource.  Assumes parameters were already
- * verified by read_partial_wim_resource().  */
+/*
+ * read_compressed_wim_resource() -
+ *
+ * Read data from a compressed WIM resource.
+ *
+ * @rspec
+ *     Specification of the compressed WIM resource to read from.
+ * @ranges
+ *     Nonoverlapping, nonempty ranges of the uncompressed resource data to
+ *     read, sorted by increasing offset.
+ * @num_ranges
+ *     Number of ranges in @ranges; must be at least 1.
+ * @cb
+ *     Callback function to feed the data being read.  Each call provides the
+ *     next chunk of the requested data, uncompressed.  Each chunk will be of
+ *     nonzero size and will not cross range boundaries, but otherwise will be
+ *     of unspecified size.
+ * @cb_ctx
+ *     Parameter to pass to @cb_ctx.
+ *
+ * Possible return values:
+ *
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_READ                   (errno set)
+ *     WIMLIB_ERR_UNEXPECTED_END_OF_FILE (errno set to 0)
+ *     WIMLIB_ERR_NOMEM                  (errno set to ENOMEM)
+ *     WIMLIB_ERR_DECOMPRESSION          (errno set to EINVAL)
+ *
+ *     or other error code returned by the @cb function.
+ */
 static int
 read_compressed_wim_resource(const struct wim_resource_spec * const rspec,
-                            const u64 size, const consume_data_callback_t cb,
-                            const u32 cb_chunk_size, void * const ctx_or_buf,
-                            const int flags, const u64 offset)
+                            const struct data_range * const ranges,
+                            const size_t num_ranges,
+                            const consume_data_callback_t cb,
+                            void * const cb_ctx)
 {
        int ret;
        int errno_save;
 
-       const u32 orig_chunk_size = rspec->cchunk_size;
-       const u32 orig_chunk_order = bsr32(orig_chunk_size);
+       u64 *chunk_offsets = NULL;
+       u8 *ubuf = NULL;
+       void *cbuf = NULL;
+       bool chunk_offsets_malloced = false;
+       bool ubuf_malloced = false;
+       bool cbuf_malloced = false;
+       struct wimlib_decompressor *decompressor = NULL;
+
+       /* Sanity checks  */
+       wimlib_assert(rspec != NULL);
+       wimlib_assert(resource_is_compressed(rspec));
+       wimlib_assert(cb != NULL);
+       wimlib_assert(num_ranges != 0);
+       for (size_t i = 0; i < num_ranges; i++) {
+               DEBUG("Range %zu/%zu: %"PRIu64"@+%"PRIu64" / %"PRIu64,
+                     i + 1, num_ranges, ranges[i].size, ranges[i].offset,
+                     rspec->uncompressed_size);
+               wimlib_assert(ranges[i].size != 0);
+               wimlib_assert(ranges[i].offset + ranges[i].size >= ranges[i].size);
+               wimlib_assert(ranges[i].offset + ranges[i].size <= rspec->uncompressed_size);
+       }
+       for (size_t i = 0; i < num_ranges - 1; i++)
+               wimlib_assert(ranges[i].offset + ranges[i].size <= ranges[i + 1].offset);
 
-       wimlib_assert(is_power_of_2(orig_chunk_size));
+       /* Get the offsets of the first and last bytes of the read.  */
+       const u64 first_offset = ranges[0].offset;
+       const u64 last_offset = ranges[num_ranges - 1].offset + ranges[num_ranges - 1].size - 1;
 
-       /* Handle the trivial case.  */
-       if (size == 0)
-               return 0;
+       /* Get the file descriptor for the WIM.  */
+       struct filedes * const in_fd = &rspec->wim->in_fd;
 
-       if (rspec->ctype == WIMLIB_COMPRESSION_TYPE_LZMS) {
-               /* TODO */
+       /* Determine if we're reading a pipable resource from a pipe or not.  */
+       const bool is_pipe_read = !filedes_is_seekable(in_fd);
 
-               unsigned clen = rspec->size_in_wim;
-               unsigned ulen = rspec->uncompressed_size;
+       /* Determine if the chunk table is in an altenate format.  */
+       const bool alt_chunk_table = (rspec->flags & WIM_RESHDR_FLAG_PACKED_STREAMS)
+                                       && !is_pipe_read;
 
-               fprintf(stderr, "clen=%u, ulen=%u, offset=%lu\n", clen, ulen,
-                       rspec->offset_in_wim);
+       /* Get the maximum size of uncompressed chunks in this resource, which
+        * we require be a power of 2.  */
+       u32 chunk_size;
+       u64 cur_read_offset = rspec->offset_in_wim;
+       int ctype;
+       if (alt_chunk_table) {
+               /* Alternate chunk table format.  Its header specifies the chunk
+                * size and compression format.  */
+               struct alt_chunk_table_header_disk hdr;
 
-               u8 *cbuf = MALLOC(clen);
-               u8 *ubuf = MALLOC(ulen);
+               ret = full_pread(in_fd, &hdr, sizeof(hdr), cur_read_offset);
+               if (ret)
+                       goto read_error;
+               cur_read_offset += sizeof(hdr);
 
-               ret = full_pread(&rspec->wim->in_fd,
-                                cbuf, clen, rspec->offset_in_wim);
-               if (ret) {
-                       ERROR_WITH_ERRNO("Can't read compressed data");
-                       goto out_free_bufs;
-               }
+               chunk_size = le32_to_cpu(hdr.chunk_size);
+               ctype = le32_to_cpu(hdr.compression_format);
 
-               ret = lzms_decompress(cbuf, clen, ubuf, ulen,
-                                     orig_chunk_size);
-               if (ret) {
-                       ERROR("LZMS decompression error.");
-                       errno = EINVAL;
-                       ret = WIMLIB_ERR_DECOMPRESSION;
-                       goto out_free_bufs;
-               }
-               if (cb) {
-                       u32 chunk_size;
-                       for (u64 i = offset; i < offset + size; i += chunk_size) {
-                               chunk_size = min(offset + size - i, cb_chunk_size);
-                               ret = cb(&ubuf[i], chunk_size, ctx_or_buf);
-                               if (ret)
-                                       goto out_free_bufs;
-                       }
-               } else {
-                       memcpy(ctx_or_buf, &ubuf[offset], size);
-               }
-               ret = 0;
-       out_free_bufs:
-               FREE(ubuf);
-               FREE(cbuf);
-               return ret;
+               /* Format numbers must be the same as in WIMGAPI to be
+                * compatible.  */
+               BUILD_BUG_ON(WIMLIB_COMPRESSION_TYPE_NONE != 0);
+               BUILD_BUG_ON(WIMLIB_COMPRESSION_TYPE_LZX != 1);
+               BUILD_BUG_ON(WIMLIB_COMPRESSION_TYPE_XPRESS != 2);
+               BUILD_BUG_ON(WIMLIB_COMPRESSION_TYPE_LZMS != 3);
+       } else {
+               /* "Normal" format: the maximum uncompressed chunk size and the
+                * compression format default to those of the WIM itself.  */
+               chunk_size = rspec->wim->chunk_size;
+               ctype = rspec->wim->compression_type;
+       }
+       if (!is_power_of_2(chunk_size)) {
+               ERROR("Invalid compressed resource: "
+                     "expected power-of-2 chunk size (got %u)", chunk_size);
+               ret = WIMLIB_ERR_INVALID_CHUNK_SIZE;
+               goto out_free_memory;
        }
 
-       u64 *chunk_offsets = NULL;
-       u8 *out_buf = NULL;
-       u8 *tmp_buf = NULL;
-       void *compressed_buf = NULL;
-       bool chunk_offsets_malloced = false;
-       bool out_buf_malloced = false;
-       bool tmp_buf_malloced = false;
-       bool compressed_buf_malloced = false;
-
-       /* Get the file descriptor for the WIM.  */
-       struct filedes * const in_fd = &rspec->wim->in_fd;
-
-       /* Determine if we're reading a pipable resource from a pipe or not.  */
-       const bool is_pipe_read = !filedes_is_seekable(in_fd);
-
-       /* Calculate the number of chunks the resource is divided into.  */
-       const u64 num_chunks = (rspec->uncompressed_size + orig_chunk_size - 1) >> orig_chunk_order;
+       /* Get valid decompressor.  */
+       if (ctype == rspec->wim->decompressor_ctype &&
+           chunk_size == rspec->wim->decompressor_max_block_size)
+       {
+               /* Cached decompressor.  */
+               decompressor = rspec->wim->decompressor;
+               rspec->wim->decompressor_ctype = WIMLIB_COMPRESSION_TYPE_NONE;
+               rspec->wim->decompressor = NULL;
+       } else {
+               ret = wimlib_create_decompressor(ctype, chunk_size, NULL,
+                                                &decompressor);
+               if (ret)
+                       goto out_free_memory;
+       }
 
-       /* Calculate the 0-based index of the chunk at which the read starts.
-        */
-       const u64 start_chunk = offset >> orig_chunk_order;
+       const u32 chunk_order = bsr32(chunk_size);
 
-       /* For pipe reads, we always must start from the 0th chunk.  */
-       const u64 actual_start_chunk = (is_pipe_read ? 0 : start_chunk);
+       /* Calculate the total number of chunks the resource is divided into.  */
+       const u64 num_chunks = (rspec->uncompressed_size + chunk_size - 1) >> chunk_order;
 
-       /* Calculate the offset, within the start chunk, of the first byte of
-        * the read.  */
-       const u32 start_offset_in_chunk = offset & (orig_chunk_size - 1);
+       /* Calculate the 0-based indices of the first and last chunks containing
+        * data that needs to be passed to the callback.  */
+       const u64 first_needed_chunk = first_offset >> chunk_order;
+       const u64 last_needed_chunk = last_offset >> chunk_order;
 
-       /* Calculate the index of the chunk that contains the last byte of the
-        * read.  */
-       const u64 end_chunk = (offset + size - 1) >> orig_chunk_order;
+       /* Calculate the 0-based index of the first chunk that actually needs to
+        * be read.  This is normally first_needed_chunk, but for pipe reads we
+        * must always start from the 0th chunk.  */
+       const u64 read_start_chunk = (is_pipe_read ? 0 : first_needed_chunk);
 
-       /* Calculate the offset, within the end chunk, of the last byte of the
-        * read.  */
-       const u32 end_offset_in_chunk = (offset + size - 1) & (orig_chunk_size - 1);
+       /* Calculate the number of chunk offsets that are needed for the chunks
+        * being read.  */
+       const u64 num_needed_chunk_offsets =
+               last_needed_chunk - read_start_chunk + 1 +
+               (last_needed_chunk < num_chunks - 1);
 
-       /* Calculate the number of entries in the chunk table; it's one less
-        * than the number of chunks, since the first chunk has no entry.  */
-       const u64 num_chunk_entries = num_chunks - 1;
+       /* Calculate the number of entries in the chunk table.  Normally, it's
+        * one less than the number of chunks, since the first chunk has no
+        * entry.  But in the alternate chunk table format, the chunk entries
+        * contain chunk sizes, not offsets, and there is one per chunk.  */
+       const u64 num_chunk_entries = (alt_chunk_table ? num_chunks : num_chunks - 1);
 
        /* Set the size of each chunk table entry based on the resource's
-        * uncompressed size.  */
-       const u64 chunk_entry_size = (rspec->uncompressed_size > (1ULL << 32)) ? 8 : 4;
+        * uncompressed size.  XXX:  Does the alternate chunk table really
+        * always have 4-byte entries?  */
+       const u64 chunk_entry_size =
+               (rspec->uncompressed_size > (1ULL << 32) && !alt_chunk_table)
+                       ? 8 : 4;
 
-       /* Calculate the size, in bytes, of the full chunk table.  */
+       /* Calculate the size of the chunk table in bytes.  */
        const u64 chunk_table_size = num_chunk_entries * chunk_entry_size;
 
-       /* Current offset to read from.  */
-       u64 cur_read_offset = rspec->offset_in_wim;
+       /* Calculate the size of the chunk table in bytes, including the header
+        * in the case of the alternate chunk table format.  */
+       const u64 chunk_table_full_size =
+               (alt_chunk_table) ? chunk_table_size + sizeof(struct alt_chunk_table_header_disk)
+                                 : chunk_table_size;
+
        if (!is_pipe_read) {
-               /* Read the chunk table into memory.  */
-
-               /* Calculate the number of chunk entries are actually needed to
-                * read the requested part of the resource.  Include an entry
-                * for the first chunk even though that doesn't exist in the
-                * on-disk table, but take into account that if the last chunk
-                * required for the read is not the last chunk of the resource,
-                * an extra chunk entry is needed so that the compressed size of
-                * the last chunk of the read can be determined.  */
-               const u64 num_alloc_chunk_entries = end_chunk - start_chunk +
-                                                   1 + (end_chunk != num_chunks - 1);
-
-               /* Allocate a buffer to hold a subset of the chunk table.  It
-                * will only contain offsets for the chunks that are actually
-                * needed for this read.  For speed, allocate the buffer on the
-                * stack unless it's too large.  */
-               if ((size_t)(num_alloc_chunk_entries * sizeof(u64)) !=
-                           (num_alloc_chunk_entries * sizeof(u64)))
+               /* Read the needed chunk table entries into memory and use them
+                * to initialize the chunk_offsets array.  */
+
+               u64 first_chunk_entry_to_read;
+               u64 last_chunk_entry_to_read;
+
+               if (alt_chunk_table) {
+                       /* The alternate chunk table contains chunk sizes, not
+                        * offsets, so we always must read all preceding entries
+                        * in order to determine offsets.  */
+                       first_chunk_entry_to_read = 0;
+                       last_chunk_entry_to_read = last_needed_chunk;
+               } else {
+                       /* Here we must account for the fact that the first
+                        * chunk has no explicit chunk table entry.  */
+
+                       if (read_start_chunk == 0)
+                               first_chunk_entry_to_read = 0;
+                       else
+                               first_chunk_entry_to_read = read_start_chunk - 1;
+
+                       if (last_needed_chunk == 0)
+                               last_chunk_entry_to_read = 0;
+                       else
+                               last_chunk_entry_to_read = last_needed_chunk - 1;
+
+                       if (last_needed_chunk < num_chunks - 1)
+                               last_chunk_entry_to_read++;
+               }
+
+               const u64 num_chunk_entries_to_read =
+                       last_chunk_entry_to_read - first_chunk_entry_to_read + 1;
+
+               const u64 chunk_offsets_alloc_size =
+                       max(num_chunk_entries_to_read,
+                           num_needed_chunk_offsets) * sizeof(chunk_offsets[0]);
+
+               if ((size_t)chunk_offsets_alloc_size != chunk_offsets_alloc_size)
                        goto oom;
 
-               if (num_alloc_chunk_entries <= STACK_MAX / sizeof(u64)) {
-                       chunk_offsets = alloca(num_alloc_chunk_entries * sizeof(u64));
+               if (chunk_offsets_alloc_size <= STACK_MAX) {
+                       chunk_offsets = alloca(chunk_offsets_alloc_size);
                } else {
-                       chunk_offsets = MALLOC(num_alloc_chunk_entries * sizeof(u64));
+                       chunk_offsets = MALLOC(chunk_offsets_alloc_size);
                        if (chunk_offsets == NULL)
                                goto oom;
                        chunk_offsets_malloced = true;
                }
 
-               /* Set the implicit offset of the first chunk if it's included
-                * in the needed chunks.  */
-               if (start_chunk == 0)
-                       chunk_offsets[0] = 0;
-
-               /* Calculate the index of the first needed entry in the chunk
-                * table.  */
-               const u64 start_table_idx = (start_chunk == 0) ?
-                               0 : start_chunk - 1;
-
-               /* Calculate the number of entries that need to be read from the
-                * chunk table.  */
-               const u64 num_needed_chunk_entries = (start_chunk == 0) ?
-                               num_alloc_chunk_entries - 1 : num_alloc_chunk_entries;
-
-               /* Calculate the number of bytes of data that need to be read
-                * from the chunk table.  */
-               const size_t chunk_table_needed_size =
-                               num_needed_chunk_entries * chunk_entry_size;
-
-               /* Calculate the byte offset, in the WIM file, of the first
-                * chunk table entry to read.  Take into account that if the WIM
-                * file is in the special "pipable" format, then the chunk table
-                * is at the end of the resource, not the beginning.  */
+               const size_t chunk_table_size_to_read =
+                       num_chunk_entries_to_read * chunk_entry_size;
+
                const u64 file_offset_of_needed_chunk_entries =
-                       rspec->offset_in_wim
-                       + (start_table_idx * chunk_entry_size)
+                       cur_read_offset
+                       + (first_chunk_entry_to_read * chunk_entry_size)
                        + (rspec->is_pipable ? (rspec->size_in_wim - chunk_table_size) : 0);
 
-               /* Read the needed chunk table entries into the end of the
-                * chunk_offsets buffer.  */
-               void * const chunk_tab_data = (u8*)&chunk_offsets[num_alloc_chunk_entries] -
-                                             chunk_table_needed_size;
-               ret = full_pread(in_fd, chunk_tab_data, chunk_table_needed_size,
+               void * const chunk_table_data =
+                       (u8*)chunk_offsets +
+                       chunk_offsets_alloc_size -
+                       chunk_table_size_to_read;
+
+               ret = full_pread(in_fd, chunk_table_data, chunk_table_size_to_read,
                                 file_offset_of_needed_chunk_entries);
                if (ret)
                        goto read_error;
 
                /* Now fill in chunk_offsets from the entries we have read in
-                * chunk_tab_data.  Careful: chunk_offsets aliases
-                * chunk_tab_data, which breaks C's aliasing rules when we read
-                * 32-bit integers and store 64-bit integers.  But since the
-                * operations are safe as long as the compiler doesn't mess with
-                * their order, we use the gcc may_alias extension to tell the
-                * compiler that loads from the 32-bit integers may alias stores
-                * to the 64-bit integers.  */
-               {
-                       typedef le64 __attribute__((may_alias)) aliased_le64_t;
-                       typedef le32 __attribute__((may_alias)) aliased_le32_t;
-                       u64 * const chunk_offsets_p = chunk_offsets + (start_chunk == 0);
-                       u64 i;
+                * chunk_tab_data.  We break aliasing rules here to avoid having
+                * to allocate yet another array.  */
+               typedef le64 __attribute__((may_alias)) aliased_le64_t;
+               typedef le32 __attribute__((may_alias)) aliased_le32_t;
+               u64 * chunk_offsets_p = chunk_offsets;
+
+               if (alt_chunk_table) {
+                       u64 cur_offset = 0;
+                       aliased_le32_t *raw_entries = chunk_table_data;
+
+                       for (size_t i = 0; i < num_chunk_entries_to_read; i++) {
+                               u32 entry = le32_to_cpu(raw_entries[i]);
+                               if (i >= read_start_chunk)
+                                       *chunk_offsets_p++ = cur_offset;
+                               cur_offset += entry;
+                       }
+                       if (last_needed_chunk < num_chunks - 1)
+                               *chunk_offsets_p = cur_offset;
+               } else {
+                       if (read_start_chunk == 0)
+                               *chunk_offsets_p++ = 0;
 
                        if (chunk_entry_size == 4) {
-                               aliased_le32_t *raw_entries = (aliased_le32_t*)chunk_tab_data;
-                               for (i = 0; i < num_needed_chunk_entries; i++)
-                                       chunk_offsets_p[i] = le32_to_cpu(raw_entries[i]);
+                               aliased_le32_t *raw_entries = chunk_table_data;
+                               for (size_t i = 0; i < num_chunk_entries_to_read; i++)
+                                       *chunk_offsets_p++ = le32_to_cpu(raw_entries[i]);
                        } else {
-                               aliased_le64_t *raw_entries = (aliased_le64_t*)chunk_tab_data;
-                               for (i = 0; i < num_needed_chunk_entries; i++)
-                                       chunk_offsets_p[i] = le64_to_cpu(raw_entries[i]);
+                               aliased_le64_t *raw_entries = chunk_table_data;
+                               for (size_t i = 0; i < num_chunk_entries_to_read; i++)
+                                       *chunk_offsets_p++ = le64_to_cpu(raw_entries[i]);
                        }
                }
 
                /* Set offset to beginning of first chunk to read.  */
                cur_read_offset += chunk_offsets[0];
                if (rspec->is_pipable)
-                       cur_read_offset += start_chunk * sizeof(struct pwm_chunk_hdr);
+                       cur_read_offset += read_start_chunk * sizeof(struct pwm_chunk_hdr);
                else
                        cur_read_offset += chunk_table_size;
        }
 
-       /* If using a callback function, allocate a temporary buffer that will
-        * hold data being passed to it.  If writing directly to a buffer
-        * instead, arrange to write data directly into it.  */
-       size_t out_buf_size;
-       u8 *out_buf_end, *out_p;
-       if (cb) {
-               out_buf_size = max(cb_chunk_size, orig_chunk_size);
-               if (out_buf_size <= STACK_MAX) {
-                       out_buf = alloca(out_buf_size);
-               } else {
-                       out_buf = MALLOC(out_buf_size);
-                       if (out_buf == NULL)
-                               goto oom;
-                       out_buf_malloced = true;
-               }
+       /* Allocate buffer for holding the uncompressed data of each chunk.  */
+       if (chunk_size <= STACK_MAX) {
+               ubuf = alloca(chunk_size);
        } else {
-               out_buf_size = size;
-               out_buf = ctx_or_buf;
+               ubuf = MALLOC(chunk_size);
+               if (ubuf == NULL)
+                       goto oom;
+               ubuf_malloced = true;
        }
-       out_buf_end = out_buf + out_buf_size;
-       out_p = out_buf;
 
-       /* Unless the raw compressed data was requested, allocate a temporary
-        * buffer for reading compressed chunks, each of which can be at most
-        * @orig_chunk_size - 1 bytes.  This excludes compressed chunks that are
-        * a full @orig_chunk_size bytes, which are actually stored
+       /* Allocate a temporary buffer for reading compressed chunks, each of
+        * which can be at most @chunk_size - 1 bytes.  This excludes compressed
+        * chunks that are a full @chunk_size bytes, which are actually stored
         * uncompressed.  */
-       if (!(flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS)) {
-               if (orig_chunk_size - 1 <= STACK_MAX) {
-                       compressed_buf = alloca(orig_chunk_size - 1);
-               } else {
-                       compressed_buf = MALLOC(orig_chunk_size - 1);
-                       if (compressed_buf == NULL)
-                               goto oom;
-                       compressed_buf_malloced = true;
-               }
+       if (chunk_size - 1 <= STACK_MAX) {
+               cbuf = alloca(chunk_size - 1);
+       } else {
+               cbuf = MALLOC(chunk_size - 1);
+               if (cbuf == NULL)
+                       goto oom;
+               cbuf_malloced = true;
        }
 
-       /* Allocate yet another temporary buffer, this one for decompressing
-        * chunks for which only part of the data is needed.  */
-       if (start_offset_in_chunk != 0 ||
-           (end_offset_in_chunk != orig_chunk_size - 1 &&
-            offset + size != rspec->uncompressed_size))
-       {
-               if (orig_chunk_size <= STACK_MAX) {
-                       tmp_buf = alloca(orig_chunk_size);
-               } else {
-                       tmp_buf = MALLOC(orig_chunk_size);
-                       if (tmp_buf == NULL)
-                               goto oom;
-                       tmp_buf_malloced = true;
-               }
-       }
+       /* Set current data range.  */
+       const struct data_range *cur_range = ranges;
+       const struct data_range * const end_range = &ranges[num_ranges];
+       u64 cur_range_pos = cur_range->offset;
+       u64 cur_range_end = cur_range->offset + cur_range->size;
 
-       /* Read, and possibly decompress, each needed chunk, either writing the
-        * data directly into the @ctx_or_buf buffer or passing it to the @cb
-        * callback function.  */
-       for (u64 i = actual_start_chunk; i <= end_chunk; i++) {
+       /* Read and process each needed chunk.  */
+       for (u64 i = read_start_chunk; i <= last_needed_chunk; i++) {
 
                /* Calculate uncompressed size of next chunk.  */
                u32 chunk_usize;
-               if ((i == num_chunks - 1) && (rspec->uncompressed_size & (orig_chunk_size - 1)))
-                       chunk_usize = (rspec->uncompressed_size & (orig_chunk_size - 1));
+               if ((i == num_chunks - 1) && (rspec->uncompressed_size & (chunk_size - 1)))
+                       chunk_usize = (rspec->uncompressed_size & (chunk_size - 1));
                else
-                       chunk_usize = orig_chunk_size;
+                       chunk_usize = chunk_size;
 
                /* Calculate compressed size of next chunk.  */
                u32 chunk_csize;
@@ -410,13 +430,13 @@ read_compressed_wim_resource(const struct wim_resource_spec * const rspec,
                } else {
                        if (i == num_chunks - 1) {
                                chunk_csize = rspec->size_in_wim -
-                                             chunk_table_size -
-                                             chunk_offsets[i - start_chunk];
+                                             chunk_table_full_size -
+                                             chunk_offsets[i - read_start_chunk];
                                if (rspec->is_pipable)
                                        chunk_csize -= num_chunks * sizeof(struct pwm_chunk_hdr);
                        } else {
-                               chunk_csize = chunk_offsets[i + 1 - start_chunk] -
-                                             chunk_offsets[i - start_chunk];
+                               chunk_csize = chunk_offsets[i + 1 - read_start_chunk] -
+                                             chunk_offsets[i - read_start_chunk];
                        }
                }
                if (chunk_csize == 0 || chunk_csize > chunk_usize) {
@@ -428,214 +448,192 @@ read_compressed_wim_resource(const struct wim_resource_spec * const rspec,
                if (rspec->is_pipable)
                        cur_read_offset += sizeof(struct pwm_chunk_hdr);
 
-               if (i >= start_chunk) {
-                       /* Calculate how much of this chunk needs to be read.  */
-                       u32 chunk_needed_size;
-                       u32 start_offset = 0;
-                       u32 end_offset = orig_chunk_size - 1;
-
-                       if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS) {
-                               chunk_needed_size = chunk_csize;
-                       } else {
-                               if (i == start_chunk)
-                                       start_offset = start_offset_in_chunk;
-
-                               if (i == end_chunk)
-                                       end_offset = end_offset_in_chunk;
+               /* Offsets in the uncompressed resource at which this chunk
+                * starts and ends.  */
+               const u64 chunk_start_offset = i << chunk_order;
+               const u64 chunk_end_offset = chunk_start_offset + chunk_usize;
 
-                               chunk_needed_size = end_offset + 1 - start_offset;
-                       }
+               if (chunk_end_offset <= cur_range_pos) {
 
-                       if (chunk_csize == chunk_usize ||
-                           (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS))
-                       {
-                               /* Read the raw chunk data.  */
+                       /* The next range does not require data in this chunk,
+                        * so skip it.  */
+                       cur_read_offset += chunk_csize;
+                       if (is_pipe_read) {
+                               u8 dummy;
 
-                               ret = full_pread(in_fd,
-                                                out_p,
-                                                chunk_needed_size,
-                                                cur_read_offset + start_offset);
+                               ret = full_pread(in_fd, &dummy, 1, cur_read_offset - 1);
                                if (ret)
                                        goto read_error;
-                       } else {
-                               /* Read and decompress the chunk.  */
+                       }
+               } else {
 
-                               u8 *target;
+                       /* Read the chunk and feed data to the callback
+                        * function.  */
+                       u8 *read_buf;
 
-                               ret = full_pread(in_fd,
-                                                compressed_buf,
-                                                chunk_csize,
-                                                cur_read_offset);
-                               if (ret)
-                                       goto read_error;
+                       if (chunk_csize == chunk_usize)
+                               read_buf = ubuf;
+                       else
+                               read_buf = cbuf;
+
+                       ret = full_pread(in_fd,
+                                        read_buf,
+                                        chunk_csize,
+                                        cur_read_offset);
+                       if (ret)
+                               goto read_error;
 
-                               if (chunk_needed_size == chunk_usize)
-                                       target = out_p;
-                               else
-                                       target = tmp_buf;
-
-                               ret = decompress(compressed_buf,
-                                                chunk_csize,
-                                                target,
-                                                chunk_usize,
-                                                rspec->ctype,
-                                                orig_chunk_size);
+                       if (read_buf == cbuf) {
+                               DEBUG("Decompressing chunk %"PRIu64" "
+                                     "(csize=%"PRIu32" usize=%"PRIu32")",
+                                     i, chunk_csize, chunk_usize);
+                               ret = wimlib_decompress(cbuf,
+                                                       chunk_csize,
+                                                       ubuf,
+                                                       chunk_usize,
+                                                       decompressor);
                                if (ret) {
                                        ERROR("Failed to decompress data!");
                                        ret = WIMLIB_ERR_DECOMPRESSION;
                                        errno = EINVAL;
                                        goto out_free_memory;
                                }
-                               if (chunk_needed_size != chunk_usize)
-                                       memcpy(out_p, tmp_buf + start_offset,
-                                              chunk_needed_size);
                        }
+                       cur_read_offset += chunk_csize;
+
+                       /* At least one range requires data in this chunk.  */
+                       do {
+                               size_t start, end, size;
+
+                               /* Calculate how many bytes of data should be
+                                * sent to the callback function, taking into
+                                * account that data sent to the callback
+                                * function must not overlap range boundaries.
+                                */
+                               start = cur_range_pos - chunk_start_offset;
+                               end = min(cur_range_end, chunk_end_offset) - chunk_start_offset;
+                               size = end - start;
 
-                       out_p += chunk_needed_size;
-
-                       if (cb) {
-                               /* Feed the data to the callback function.  */
-
-                               if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS) {
-                                       ret = cb(out_buf, out_p - out_buf, ctx_or_buf);
-                                       if (ret)
-                                               goto out_free_memory;
-                                       out_p = out_buf;
-                               } else if (i == end_chunk || out_p == out_buf_end) {
-                                       size_t bytes_sent;
-                                       const u8 *p;
-
-                                       for (p = out_buf; p != out_p; p += bytes_sent) {
-                                               bytes_sent = min(cb_chunk_size, out_p - p);
-                                               ret = cb(p, bytes_sent, ctx_or_buf);
-                                               if (ret)
-                                                       goto out_free_memory;
+                               ret = (*cb)(&ubuf[start], size, cb_ctx);
+
+                               if (ret)
+                                       goto out_free_memory;
+
+                               cur_range_pos += size;
+                               if (cur_range_pos == cur_range_end) {
+                                       /* Advance to next range.  */
+                                       if (++cur_range == end_range) {
+                                               cur_range_pos = ~0ULL;
+                                       } else {
+                                               cur_range_pos = cur_range->offset;
+                                               cur_range_end = cur_range->offset + cur_range->size;
                                        }
-                                       out_p = out_buf;
                                }
-                       }
-                       cur_read_offset += chunk_csize;
-               } else {
-                       u8 dummy;
-
-                       /* Skip data only.  */
-                       cur_read_offset += chunk_csize;
-                       ret = full_pread(in_fd, &dummy, 1, cur_read_offset - 1);
-                       if (ret)
-                               goto read_error;
+                       } while (cur_range_pos < chunk_end_offset);
                }
        }
 
-       if (is_pipe_read
-           && size == rspec->uncompressed_size
-           && chunk_table_size)
+       if (is_pipe_read &&
+           last_offset == rspec->uncompressed_size - 1 &&
+           chunk_table_size)
        {
                u8 dummy;
-               /* Skip chunk table at end of pipable resource.  */
-
+               /* If reading a pipable resource from a pipe and the full data
+                * was requested, skip the chunk table at the end so that the
+                * file descriptor is fully clear of the resource after this
+                * returns.  */
                cur_read_offset += chunk_table_size;
                ret = full_pread(in_fd, &dummy, 1, cur_read_offset - 1);
                if (ret)
                        goto read_error;
        }
        ret = 0;
+
 out_free_memory:
        errno_save = errno;
+       if (decompressor) {
+               wimlib_free_decompressor(rspec->wim->decompressor);
+               rspec->wim->decompressor = decompressor;
+               rspec->wim->decompressor_ctype = ctype;
+               rspec->wim->decompressor_max_block_size = chunk_size;
+       }
        if (chunk_offsets_malloced)
                FREE(chunk_offsets);
-       if (out_buf_malloced)
-               FREE(out_buf);
-       if (compressed_buf_malloced)
-               FREE(compressed_buf);
-       if (tmp_buf_malloced)
-               FREE(tmp_buf);
+       if (ubuf_malloced)
+               FREE(ubuf);
+       if (cbuf_malloced)
+               FREE(cbuf);
        errno = errno_save;
        return ret;
 
 oom:
        ERROR("Not enough memory available to read size=%"PRIu64" bytes "
-             "from compressed resource!", size);
+             "from compressed WIM resource!", last_offset - first_offset + 1);
        errno = ENOMEM;
        ret = WIMLIB_ERR_NOMEM;
        goto out_free_memory;
 
 read_error:
-       ERROR_WITH_ERRNO("Error reading compressed file resource!");
+       ERROR_WITH_ERRNO("Error reading compressed WIM resource!");
        goto out_free_memory;
 }
 
-/* Read raw data from a file descriptor at the specified offset.  */
+/* Read raw data from a file descriptor at the specified offset, feeding the
+ * data it in chunks into the specified callback function.  */
 static int
-read_raw_file_data(struct filedes *in_fd, u64 size, consume_data_callback_t cb,
-                  u32 cb_chunk_size, void *ctx_or_buf, u64 offset)
+read_raw_file_data(struct filedes *in_fd, u64 offset, u64 size,
+                  consume_data_callback_t cb, void *cb_ctx)
 {
+       u8 buf[BUFFER_SIZE];
+       size_t bytes_to_read;
        int ret;
-       u8 *tmp_buf;
-       bool tmp_buf_malloced = false;
-
-       if (cb) {
-               /* Send data to callback function in chunks.  */
-               if (cb_chunk_size <= STACK_MAX) {
-                       tmp_buf = alloca(cb_chunk_size);
-               } else {
-                       tmp_buf = MALLOC(cb_chunk_size);
-                       if (tmp_buf == NULL) {
-                               ret = WIMLIB_ERR_NOMEM;
-                               goto out;
-                       }
-                       tmp_buf_malloced = true;
-               }
 
-               while (size) {
-                       size_t bytes_to_read = min(cb_chunk_size, size);
-                       ret = full_pread(in_fd, tmp_buf, bytes_to_read,
-                                        offset);
-                       if (ret)
-                               goto read_error;
-                       ret = cb(tmp_buf, bytes_to_read, ctx_or_buf);
-                       if (ret)
-                               goto out;
-                       size -= bytes_to_read;
-                       offset += bytes_to_read;
+       while (size) {
+               bytes_to_read = min(sizeof(buf), size);
+               ret = full_pread(in_fd, buf, bytes_to_read, offset);
+               if (ret) {
+                       ERROR_WITH_ERRNO("Read error");
+                       return ret;
                }
-       } else {
-               /* Read data directly into buffer.  */
-               ret = full_pread(in_fd, ctx_or_buf, size, offset);
+               ret = cb(buf, bytes_to_read, cb_ctx);
                if (ret)
-                       goto read_error;
+                       return ret;
+               size -= bytes_to_read;
+               offset += bytes_to_read;
        }
-       ret = 0;
-       goto out;
+       return 0;
+}
 
-read_error:
-       ERROR_WITH_ERRNO("Read error");
-out:
-       if (tmp_buf_malloced)
-               FREE(tmp_buf);
-       return ret;
+/* A consume_data_callback_t implementation that simply concatenates all chunks
+ * into a buffer.  */
+static int
+bufferer_cb(const void *chunk, size_t size, void *_ctx)
+{
+       u8 **buf_p = _ctx;
+
+       *buf_p = mempcpy(*buf_p, chunk, size);
+       return 0;
 }
 
 /*
  * read_partial_wim_resource()-
  *
  * Read a range of data from an uncompressed or compressed resource in a WIM
- * file.  Data is written into a buffer or fed into a callback function, as
- * documented in read_stream_prefix().
+ * file.
  *
- * By default, this function provides the uncompressed data of the resource, and
- * @size and @offset and interpreted relative to the uncompressed contents of
- * the resource.  This behavior can be modified by either of the following
- * flags:
- *
- * WIMLIB_READ_RESOURCE_FLAG_RAW_FULL:
- *     Read @size bytes at @offset of the raw contents of the compressed
- *     resource.  In the case of pipable resources, this excludes the stream
- *     header.  Exclusive with WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS.
- *
- * WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS:
- *     Read the raw compressed chunks of the compressed resource.  @size must
- *     be the full uncompressed size, @offset must be 0, and @cb_chunk_size
- *     must be the resource chunk size.
+ * @rspec
+ *     Specification of the WIM resource to read from.
+ * @offset
+ *     Offset within the uncompressed resource at which to start reading.
+ * @size
+ *     Number of bytes to read.
+ * @cb
+ *     Callback function to feed the data being read.  Each call provides the
+ *     next chunk of the requested data, uncompressed.  Each chunk will be of
+ *     nonzero size and will not cross range boundaries, but otherwise will be
+ *     of unspecified size.
+ * @cb_ctx
+ *     Parameter to pass to @cb_ctx.
  *
  * Return values:
  *     WIMLIB_ERR_SUCCESS (0)
@@ -646,79 +644,86 @@ out:
  *
  *     or other error code returned by the @cb function.
  */
-int
-read_partial_wim_resource(const struct wim_lookup_table_entry *lte,
-                         u64 size, consume_data_callback_t cb,
-                         u32 cb_chunk_size, void *ctx_or_buf,
-                         int flags, u64 offset)
+static int
+read_partial_wim_resource(const struct wim_resource_spec *rspec,
+                         u64 offset, u64 size,
+                         consume_data_callback_t cb, void *cb_ctx)
 {
-       const struct wim_resource_spec *rspec;
-       struct filedes *in_fd;
+       /* Sanity checks.  */
+       wimlib_assert(offset + size >= offset);
+       wimlib_assert(offset + size <= rspec->uncompressed_size);
 
-       /* Verify parameters.  */
-       wimlib_assert(lte->resource_location == RESOURCE_IN_WIM);
-       rspec = lte->rspec;
-       in_fd = &rspec->wim->in_fd;
-       if (cb)
-               wimlib_assert(is_power_of_2(cb_chunk_size));
-       if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_CHUNKS) {
-               /* Raw chunks mode is subject to the restrictions noted.  */
-               wimlib_assert(!lte_is_partial(lte));
-               wimlib_assert(!(flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL));
-               wimlib_assert(cb_chunk_size == rspec->cchunk_size);
-               wimlib_assert(size == rspec->uncompressed_size);
-               wimlib_assert(offset == 0);
-       } else if (flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL) {
-               /* Raw full mode:  read must not overrun end of store size.  */
-               wimlib_assert(!lte_is_partial(lte));
-               wimlib_assert(offset + size >= size &&
-                             offset + size <= rspec->size_in_wim);
-       } else {
-               /* Normal mode:  read must not overrun end of original size.  */
-               wimlib_assert(offset + size >= size &&
-                             lte->offset_in_res + offset + size <= rspec->uncompressed_size);
-       }
+       DEBUG("Reading %"PRIu64" @ %"PRIu64" from WIM resource  "
+             "%"PRIu64" => %"PRIu64" @ %"PRIu64,
+             size, offset, rspec->uncompressed_size,
+             rspec->size_in_wim, rspec->offset_in_wim);
 
-       DEBUG("Reading WIM resource: %"PRIu64" @ +%"PRIu64"[+%"PRIu64"] "
-             "from %"PRIu64"(%"PRIu64") @ +%"PRIu64" "
-             "(readflags 0x%08x, resflags 0x%02x%s)",
-             size, offset, lte->offset_in_res,
-             rspec->size_in_wim,
-             rspec->uncompressed_size,
-             rspec->offset_in_wim,
-             flags, lte->flags,
-             (rspec->is_pipable ? ", pipable" : ""));
-
-       if ((flags & WIMLIB_READ_RESOURCE_FLAG_RAW_FULL) ||
-           rspec->ctype == WIMLIB_COMPRESSION_TYPE_NONE)
-       {
-               return read_raw_file_data(in_fd,
+       /* Trivial case.  */
+       if (size == 0)
+               return 0;
+
+       if (resource_is_compressed(rspec)) {
+               struct data_range range = {
+                       .offset = offset,
+                       .size = size,
+               };
+               return read_compressed_wim_resource(rspec, &range, 1,
+                                                   cb, cb_ctx);
+       } else {
+               return read_raw_file_data(&rspec->wim->in_fd,
+                                         rspec->offset_in_wim + offset,
                                          size,
                                          cb,
-                                         cb_chunk_size,
-                                         ctx_or_buf,
-                                         offset + rspec->offset_in_wim);
-       } else {
-               return read_compressed_wim_resource(rspec, size, cb,
-                                                   cb_chunk_size,
-                                                   ctx_or_buf, flags, offset + lte->offset_in_res);
+                                         cb_ctx);
        }
 }
 
+/* Read the specified range of uncompressed data from the specified stream,
+ * which must be located into a WIM file, into the specified buffer.  */
 int
 read_partial_wim_stream_into_buf(const struct wim_lookup_table_entry *lte,
-                                size_t size, u64 offset, void *buf)
+                                size_t size, u64 offset, void *_buf)
 {
-       return read_partial_wim_resource(lte, size, NULL, 0, buf, 0, offset);
+       u8 *buf = _buf;
+
+       wimlib_assert(lte->resource_location == RESOURCE_IN_WIM);
+
+       return read_partial_wim_resource(lte->rspec,
+                                        lte->offset_in_res + offset,
+                                        size,
+                                        bufferer_cb,
+                                        &buf);
+}
+
+/* A consume_data_callback_t implementation that simply ignores the data
+ * received.  */
+static int
+skip_chunk_cb(const void *chunk, size_t size, void *_ctx)
+{
+       return 0;
+}
+
+/* Skip over the data of the specified stream, which must correspond to a full
+ * WIM resource.  */
+int
+skip_wim_stream(struct wim_lookup_table_entry *lte)
+{
+       wimlib_assert(lte->resource_location == RESOURCE_IN_WIM);
+       wimlib_assert(!(lte->flags & WIM_RESHDR_FLAG_PACKED_STREAMS));
+       DEBUG("Skipping stream (size=%"PRIu64")", lte->size);
+       return read_partial_wim_resource(lte->rspec,
+                                        0,
+                                        lte->rspec->uncompressed_size,
+                                        skip_chunk_cb,
+                                        NULL);
 }
 
 static int
 read_wim_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
-                      consume_data_callback_t cb, u32 cb_chunk_size,
-                      void *ctx_or_buf, int flags)
+                      consume_data_callback_t cb, void *cb_ctx)
 {
-       return read_partial_wim_resource(lte, size, cb, cb_chunk_size,
-                                        ctx_or_buf, flags, 0);
+       return read_partial_wim_resource(lte->rspec, lte->offset_in_res, size,
+                                        cb, cb_ctx);
 }
 
 #ifndef __WIN32__
@@ -729,18 +734,17 @@ read_wim_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
  * This assumes the file can be accessed using the standard POSIX open(),
  * read(), and close().  On Windows this will not necessarily be the case (since
  * the file may need FILE_FLAG_BACKUP_SEMANTICS to be opened, or the file may be
- * encrypted), so Windows uses its own code for its equivalent case.
- */
+ * encrypted), so Windows uses its own code for its equivalent case.  */
 static int
 read_file_on_disk_prefix(const struct wim_lookup_table_entry *lte, u64 size,
-                        consume_data_callback_t cb, u32 cb_chunk_size,
-                        void *ctx_or_buf, int _ignored_flags)
+                        consume_data_callback_t cb, void *cb_ctx)
 {
        int ret;
        int raw_fd;
        struct filedes fd;
 
        wimlib_assert(size <= lte->size);
+
        DEBUG("Reading %"PRIu64" bytes from \"%"TS"\"", size, lte->file_on_disk);
 
        raw_fd = open(lte->file_on_disk, O_BINARY | O_RDONLY);
@@ -749,7 +753,7 @@ read_file_on_disk_prefix(const struct wim_lookup_table_entry *lte, u64 size,
                return WIMLIB_ERR_OPEN;
        }
        filedes_init(&fd, raw_fd);
-       ret = read_raw_file_data(&fd, size, cb, cb_chunk_size, ctx_or_buf, 0);
+       ret = read_raw_file_data(&fd, 0, size, cb, cb_ctx);
        filedes_close(&fd);
        return ret;
 }
@@ -759,35 +763,16 @@ read_file_on_disk_prefix(const struct wim_lookup_table_entry *lte, u64 size,
  * fact, already located in an in-memory buffer.  */
 static int
 read_buffer_prefix(const struct wim_lookup_table_entry *lte,
-                  u64 size, consume_data_callback_t cb,
-                  u32 cb_chunk_size, void *ctx_or_buf, int _ignored_flags)
+                  u64 size, consume_data_callback_t cb, void *cb_ctx)
 {
        wimlib_assert(size <= lte->size);
-
-       if (cb) {
-               /* Feed the data into the callback function in
-                * appropriately-sized chunks.  */
-               int ret;
-               u32 chunk_size;
-
-               for (u64 offset = 0; offset < size; offset += chunk_size) {
-                       chunk_size = min(cb_chunk_size, size - offset);
-                       ret = cb((const u8*)lte->attached_buffer + offset,
-                                chunk_size, ctx_or_buf);
-                       if (ret)
-                               return ret;
-               }
-       } else {
-               /* Copy the data directly into the specified buffer.  */
-               memcpy(ctx_or_buf, lte->attached_buffer, size);
-       }
-       return 0;
+       return (*cb)(lte->attached_buffer, size, cb_ctx);
 }
 
 typedef int (*read_stream_prefix_handler_t)(const struct wim_lookup_table_entry *lte,
-                                           u64 size, consume_data_callback_t cb,
-                                           u32 cb_chunk_size, void *ctx_or_buf,
-                                           int flags);
+                                           u64 size,
+                                           consume_data_callback_t cb,
+                                           void *cb_ctx);
 
 /*
  * read_stream_prefix()-
@@ -796,33 +781,18 @@ typedef int (*read_stream_prefix_handler_t)(const struct wim_lookup_table_entry
  * any one of several locations, such as in a WIM file (compressed or
  * uncompressed), in an external file, or directly in an in-memory buffer.
  *
- * This function feeds the data either to a callback function (@cb != NULL,
- * passing it @ctx_or_buf), or write it directly into a buffer (@cb == NULL,
- * @ctx_or_buf specifies the buffer, which must have room for at least @size
- * bytes).
- *
- * When (@cb != NULL), @cb_chunk_size specifies the maximum size of data chunks
- * to feed the callback function.  @cb_chunk_size must be positive, and if the
- * stream is in a WIM file, must be a power of 2.  All chunks, except possibly
- * the last one, will be this size.  If (@cb == NULL), @cb_chunk_size is
- * ignored.
- *
- * If the stream is located in a WIM file, @flags can be set as documented in
- * read_partial_wim_resource().  Otherwise @flags are ignored.
+ * This function feeds the data to a callback function @cb in chunks of
+ * unspecified size.
  *
  * Returns 0 on success; nonzero on error.  A nonzero value will be returned if
  * the stream data cannot be successfully read (for a number of different
- * reasons, depending on the stream location), or if a callback function was
- * specified and it returned nonzero.
+ * reasons, depending on the stream location), or if @cb returned nonzero in
+ * which case that error code will be returned.
  */
-int
+static int
 read_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
-                  consume_data_callback_t cb, u32 cb_chunk_size,
-                  void *ctx_or_buf, int flags)
+                  consume_data_callback_t cb, void *cb_ctx)
 {
-       /* This function merely verifies several preconditions, then passes
-        * control to an appropriate function for understanding each possible
-        * stream location.  */
        static const read_stream_prefix_handler_t handlers[] = {
                [RESOURCE_IN_WIM]             = read_wim_stream_prefix,
        #ifdef __WIN32__
@@ -843,21 +813,20 @@ read_stream_prefix(const struct wim_lookup_table_entry *lte, u64 size,
        };
        wimlib_assert(lte->resource_location < ARRAY_LEN(handlers)
                      && handlers[lte->resource_location] != NULL);
-       wimlib_assert(cb == NULL || cb_chunk_size > 0);
-       return handlers[lte->resource_location](lte, size, cb, cb_chunk_size,
-                                               ctx_or_buf, flags);
+       return handlers[lte->resource_location](lte, size, cb, cb_ctx);
 }
 
 /* Read the full uncompressed data of the specified stream into the specified
  * buffer, which must have space for at least lte->size bytes.  */
 int
-read_full_stream_into_buf(const struct wim_lookup_table_entry *lte, void *buf)
+read_full_stream_into_buf(const struct wim_lookup_table_entry *lte, void *_buf)
 {
-       return read_stream_prefix(lte, lte->size, NULL, 0, buf, 0);
+       u8 *buf = _buf;
+       return read_stream_prefix(lte, lte->size, bufferer_cb, &buf);
 }
 
-/* Read the full uncompressed data of the specified stream.  A buffer sufficient
- * to hold the data is allocated and returned in @buf_ret.  */
+/* Retrieve the full uncompressed data of the specified stream.  A buffer large
+ * enough hold the data is allocated and returned in @buf_ret.  */
 int
 read_full_stream_into_alloc_buf(const struct wim_lookup_table_entry *lte,
                                void **buf_ret)
@@ -885,7 +854,8 @@ read_full_stream_into_alloc_buf(const struct wim_lookup_table_entry *lte,
        return 0;
 }
 
-/* Retrieve the full uncompressed data of the specified WIM resource.  */
+/* Retrieve the full uncompressed data of the specified WIM resource.  A buffer
+ * large enough hold the data is allocated and returned in @buf_ret.  */
 static int
 wim_resource_spec_to_data(struct wim_resource_spec *rspec, void **buf_ret)
 {
@@ -896,7 +866,6 @@ wim_resource_spec_to_data(struct wim_resource_spec *rspec, void **buf_ret)
        if (lte == NULL)
                return WIMLIB_ERR_NOMEM;
 
-       lte->unhashed = 1;
        lte_bind_wim_resource_spec(lte, rspec);
        lte->flags = rspec->flags;
        lte->size = rspec->uncompressed_size;
@@ -909,142 +878,474 @@ wim_resource_spec_to_data(struct wim_resource_spec *rspec, void **buf_ret)
        return ret;
 }
 
-/* Retrieve the full uncompressed data of the specified WIM resource.  */
+/* Retrieve the full uncompressed data of a WIM resource specified as a raw
+ * `wim_reshdr' and the corresponding WIM file.  A large enough hold the data is
+ * allocated and returned in @buf_ret.  */
 int
 wim_reshdr_to_data(const struct wim_reshdr *reshdr, WIMStruct *wim, void **buf_ret)
 {
        DEBUG("offset_in_wim=%"PRIu64", size_in_wim=%"PRIu64", "
              "uncompressed_size=%"PRIu64,
-             reshdr->offset_in_wim, reshdr->size_in_wim, reshdr->uncompressed_size);
+             reshdr->offset_in_wim, reshdr->size_in_wim,
+             reshdr->uncompressed_size);
 
        struct wim_resource_spec rspec;
        wim_res_hdr_to_spec(reshdr, wim, &rspec);
        return wim_resource_spec_to_data(&rspec, buf_ret);
 }
 
-struct extract_ctx {
+struct streamifier_context {
+       struct read_stream_list_callbacks cbs;
+       struct wim_lookup_table_entry *cur_stream;
+       struct wim_lookup_table_entry *next_stream;
+       u64 cur_stream_offset;
+       struct wim_lookup_table_entry *final_stream;
+       size_t list_head_offset;
+};
+
+static struct wim_lookup_table_entry *
+next_stream(struct wim_lookup_table_entry *lte, size_t list_head_offset)
+{
+       struct list_head *cur;
+
+       cur = (struct list_head*)((u8*)lte + list_head_offset);
+
+       return (struct wim_lookup_table_entry*)((u8*)cur->next - list_head_offset);
+}
+
+/* A consume_data_callback_t implementation that translates raw resource data
+ * into streams, calling the begin_stream, consume_chunk, and end_stream
+ * callback functions as appropriate.  */
+static int
+streamifier_cb(const void *chunk, size_t size, void *_ctx)
+{
+       struct streamifier_context *ctx = _ctx;
+       int ret;
+
+       DEBUG("%zu bytes passed to streamifier", size);
+
+       wimlib_assert(ctx->cur_stream != NULL);
+       wimlib_assert(size <= ctx->cur_stream->size - ctx->cur_stream_offset);
+
+       if (ctx->cur_stream_offset == 0) {
+               /* Starting a new stream.  */
+               DEBUG("Begin new stream (size=%"PRIu64").",
+                     ctx->cur_stream->size);
+               ret = (*ctx->cbs.begin_stream)(ctx->cur_stream, true,
+                                              ctx->cbs.begin_stream_ctx);
+               if (ret)
+                       return ret;
+       }
+
+       /* Consume the chunk.  */
+       ret = (*ctx->cbs.consume_chunk)(chunk, size,
+                                       ctx->cbs.consume_chunk_ctx);
+       if (ret)
+               return ret;
+       ctx->cur_stream_offset += size;
+
+       if (ctx->cur_stream_offset == ctx->cur_stream->size) {
+               /* Finished reading all the data for a stream.  */
+
+               ctx->cur_stream_offset = 0;
+
+               DEBUG("End stream (size=%"PRIu64").", ctx->cur_stream->size);
+               ret = (*ctx->cbs.end_stream)(ctx->cur_stream, 0,
+                                            ctx->cbs.end_stream_ctx);
+               if (ret)
+                       return ret;
+
+               /* Advance to next stream.  */
+               ctx->cur_stream = ctx->next_stream;
+               if (ctx->cur_stream != NULL) {
+                       if (ctx->cur_stream != ctx->final_stream)
+                               ctx->next_stream = next_stream(ctx->cur_stream,
+                                                              ctx->list_head_offset);
+                       else
+                               ctx->next_stream = NULL;
+               }
+       }
+       return 0;
+}
+
+struct hasher_context {
        SHA_CTX sha_ctx;
-       consume_data_callback_t extract_chunk;
-       void *extract_chunk_arg;
+       int flags;
+       struct read_stream_list_callbacks cbs;
 };
 
+/* Callback for starting to read a stream while calculating its SHA1 message
+ * digest.  */
 static int
-extract_chunk_sha1_wrapper(const void *chunk, size_t chunk_size, void *_ctx)
+hasher_begin_stream(struct wim_lookup_table_entry *lte, bool is_partial_res,
+                   void *_ctx)
 {
-       struct extract_ctx *ctx = _ctx;
+       struct hasher_context *ctx = _ctx;
+
+       sha1_init(&ctx->sha_ctx);
 
-       sha1_update(&ctx->sha_ctx, chunk, chunk_size);
-       return ctx->extract_chunk(chunk, chunk_size, ctx->extract_chunk_arg);
+       if (ctx->cbs.begin_stream == NULL)
+               return 0;
+       else
+               return (*ctx->cbs.begin_stream)(lte, is_partial_res,
+                                               ctx->cbs.begin_stream_ctx);
 }
 
-/* Extracts the first @size bytes of a stream to somewhere.  In the process, the
- * SHA1 message digest of the uncompressed stream is checked if the full stream
- * is being extracted.
- *
- * @extract_chunk is a function that will be called to extract each chunk of the
- * stream.  */
-int
-extract_stream(const struct wim_lookup_table_entry *lte, u64 size,
-              consume_data_callback_t extract_chunk, void *extract_chunk_arg)
+/* A consume_data_callback_t implementation that continues calculating the SHA1
+ * message digest of the stream being read, then optionally passes the data on
+ * to another consume_data_callback_t implementation.  This allows checking the
+ * SHA1 message digest of a stream being extracted, for example.  */
+static int
+hasher_consume_chunk(const void *chunk, size_t size, void *_ctx)
+{
+       struct hasher_context *ctx = _ctx;
+
+       sha1_update(&ctx->sha_ctx, chunk, size);
+       if (ctx->cbs.consume_chunk == NULL)
+               return 0;
+       else
+               return (*ctx->cbs.consume_chunk)(chunk, size, ctx->cbs.consume_chunk_ctx);
+}
+
+/* Callback for finishing reading a stream while calculating its SHA1 message
+ * digest.  */
+static int
+hasher_end_stream(struct wim_lookup_table_entry *lte, int status, void *_ctx)
 {
+       struct hasher_context *ctx = _ctx;
+       u8 hash[SHA1_HASH_SIZE];
        int ret;
-       if (size == lte->size) {
-               /* Do SHA1 */
-               struct extract_ctx ctx;
-               ctx.extract_chunk = extract_chunk;
-               ctx.extract_chunk_arg = extract_chunk_arg;
-               sha1_init(&ctx.sha_ctx);
-               ret = read_stream_prefix(lte, size,
-                                        extract_chunk_sha1_wrapper,
-                                        lte_cchunk_size(lte),
-                                        &ctx, 0);
-               if (ret == 0) {
-                       u8 hash[SHA1_HASH_SIZE];
-                       sha1_final(hash, &ctx.sha_ctx);
+
+       if (status) {
+               /* Error occurred; the full stream may not have been read.  */
+               ret = status;
+               goto out_next_cb;
+       }
+
+       /* Retrieve the final SHA1 message digest.  */
+       sha1_final(hash, &ctx->sha_ctx);
+
+       if (lte->unhashed) {
+               if (ctx->flags & COMPUTE_MISSING_STREAM_HASHES) {
+                       /* No SHA1 message digest was previously present for the
+                        * stream.  Set it to the one just calculated.  */
+                       DEBUG("Set SHA1 message digest for stream "
+                             "(size=%"PRIu64").", lte->size);
+                       copy_hash(lte->hash, hash);
+               }
+       } else {
+               if (ctx->flags & VERIFY_STREAM_HASHES) {
+                       /* The stream already had a SHA1 message digest present.  Verify
+                        * that it is the same as the calculated value.  */
                        if (!hashes_equal(hash, lte->hash)) {
                                if (wimlib_print_errors) {
                                        ERROR("Invalid SHA1 message digest "
                                              "on the following WIM stream:");
                                        print_lookup_table_entry(lte, stderr);
-                                       if (lte->resource_location == RESOURCE_IN_WIM)
-                                               ERROR("The WIM file appears to be corrupt!");
                                }
                                ret = WIMLIB_ERR_INVALID_RESOURCE_HASH;
+                               errno = EINVAL;
+                               goto out_next_cb;
                        }
+                       DEBUG("SHA1 message digest okay for "
+                             "stream (size=%"PRIu64").", lte->size);
                }
-       } else {
-               /* Don't do SHA1 */
-               ret = read_stream_prefix(lte, size, extract_chunk,
-                                        lte_cchunk_size(lte),
-                                        extract_chunk_arg, 0);
        }
-       return ret;
+       ret = 0;
+out_next_cb:
+       if (ctx->cbs.end_stream == NULL)
+               return ret;
+       else
+               return (*ctx->cbs.end_stream)(lte, ret, ctx->cbs.end_stream_ctx);
 }
 
 static int
-extract_wim_chunk_to_fd(const void *buf, size_t len, void *_fd_p)
+read_full_stream_with_cbs(struct wim_lookup_table_entry *lte,
+                         const struct read_stream_list_callbacks *cbs)
 {
-       struct filedes *fd = _fd_p;
-       int ret = full_write(fd, buf, len);
+       int ret;
+
+       ret = (*cbs->begin_stream)(lte, false, cbs->begin_stream_ctx);
        if (ret)
-               ERROR_WITH_ERRNO("Error writing to file descriptor");
-       return ret;
+               return ret;
+
+       ret = read_stream_prefix(lte, lte->size, cbs->consume_chunk,
+                                cbs->consume_chunk_ctx);
+
+       return (*cbs->end_stream)(lte, ret, cbs->end_stream_ctx);
 }
 
-/* Extract the first @size bytes of the specified stream to the specified file
- * descriptor.  If @size is the full size of the stream, its SHA1 message digest
- * is also checked.  */
+/* Read the full data of the specified stream, passing the data into the
+ * specified callbacks (all of which are optional) and either checking or
+ * computing the SHA1 message digest of the stream.  */
+static int
+read_full_stream_with_sha1(struct wim_lookup_table_entry *lte,
+                          const struct read_stream_list_callbacks *cbs)
+{
+       struct hasher_context hasher_ctx = {
+               .flags = VERIFY_STREAM_HASHES | COMPUTE_MISSING_STREAM_HASHES,
+               .cbs = *cbs,
+       };
+       struct read_stream_list_callbacks hasher_cbs = {
+               .begin_stream           = hasher_begin_stream,
+               .begin_stream_ctx       = &hasher_ctx,
+               .consume_chunk          = hasher_consume_chunk,
+               .consume_chunk_ctx      = &hasher_ctx,
+               .end_stream             = hasher_end_stream,
+               .end_stream_ctx         = &hasher_ctx,
+
+       };
+       return read_full_stream_with_cbs(lte, &hasher_cbs);
+}
+
+/*
+ * Read a list of streams, each of which may be in any supported location (e.g.
+ * in a WIM or in an external file).  Unlike read_stream_prefix() or the
+ * functions which call it, this function optimizes the case where multiple
+ * streams are packed into a single compressed WIM resource and reads them all
+ * consecutively, only decompressing the data one time.
+ *
+ * @stream_list
+ *     List of streams (represented as `struct wim_lookup_table_entry's) to
+ *     read.
+ * @list_head_offset
+ *     Offset of the `struct list_head' within each `struct
+ *     wim_lookup_table_entry' that makes up the @stream_list.
+ * @cbs
+ *     Callback functions to accept the stream data.
+ * @flags
+ *     Bitwise OR of zero or more of the following flags:
+ *
+ *     VERIFY_STREAM_HASHES:
+ *             For all streams being read that have already had SHA1 message
+ *             digests computed, calculate the SHA1 message digest of the read
+ *             data and compare it with the previously computed value.  If they
+ *             do not match, return WIMLIB_ERR_INVALID_RESOURCE_HASH.
+ *
+ *     COMPUTE_MISSING_STREAM_HASHES
+ *             For all streams being read that have not yet had their SHA1
+ *             message digests computed, calculate and save their SHA1 message
+ *             digests.
+ *
+ *     STREAM_LIST_ALREADY_SORTED
+ *             @stream_list is already sorted in sequential order for reading.
+ *
+ * The callback functions are allowed to delete the current stream from the list
+ * if necessary.
+ *
+ * Returns 0 on success; a nonzero error code on failure.  Failure can occur due
+ * to an error reading the data or due to an error status being returned by any
+ * of the callback functions.
+ */
 int
-extract_stream_to_fd(const struct wim_lookup_table_entry *lte,
-                    struct filedes *fd, u64 size)
+read_stream_list(struct list_head *stream_list,
+                size_t list_head_offset,
+                const struct read_stream_list_callbacks *cbs,
+                int flags)
 {
-       return extract_stream(lte, size, extract_wim_chunk_to_fd, fd);
+       int ret;
+       struct list_head *cur, *next;
+       struct wim_lookup_table_entry *lte;
+       struct hasher_context *hasher_ctx;
+       struct read_stream_list_callbacks *sink_cbs;
+
+       if (!(flags & STREAM_LIST_ALREADY_SORTED)) {
+               ret = sort_stream_list_by_sequential_order(stream_list, list_head_offset);
+               if (ret)
+                       return ret;
+       }
+
+       if (flags & (VERIFY_STREAM_HASHES | COMPUTE_MISSING_STREAM_HASHES)) {
+               hasher_ctx = alloca(sizeof(*hasher_ctx));
+               *hasher_ctx = (struct hasher_context) {
+                       .flags  = flags,
+                       .cbs    = *cbs,
+               };
+               sink_cbs = alloca(sizeof(*sink_cbs));
+               *sink_cbs = (struct read_stream_list_callbacks) {
+                       .begin_stream           = hasher_begin_stream,
+                       .begin_stream_ctx       = hasher_ctx,
+                       .consume_chunk          = hasher_consume_chunk,
+                       .consume_chunk_ctx      = hasher_ctx,
+                       .end_stream             = hasher_end_stream,
+                       .end_stream_ctx         = hasher_ctx,
+               };
+       } else {
+               sink_cbs = (struct read_stream_list_callbacks*)cbs;
+       }
+
+       for (cur = stream_list->next, next = cur->next;
+            cur != stream_list;
+            cur = next, next = cur->next)
+       {
+               lte = (struct wim_lookup_table_entry*)((u8*)cur - list_head_offset);
+
+               if (lte->flags & WIM_RESHDR_FLAG_PACKED_STREAMS &&
+                   lte->size != lte->rspec->uncompressed_size)
+               {
+
+                       struct wim_lookup_table_entry *lte_next, *lte_last;
+                       struct list_head *next2;
+                       size_t stream_count;
+
+                       /* The next stream is a proper sub-sequence of a WIM
+                        * resource.  See if there are other streams in the same
+                        * resource that need to be read.  Since
+                        * sort_stream_list_by_sequential_order() sorted the
+                        * streams by offset in the WIM, this can be determined
+                        * by simply scanning forward in the list.  */
+
+                       lte_last = lte;
+                       stream_count = 1;
+                       for (next2 = next;
+                            next2 != stream_list
+                            && (lte_next = (struct wim_lookup_table_entry*)
+                                               ((u8*)next2 - list_head_offset),
+                                lte_next->resource_location == RESOURCE_IN_WIM
+                                && lte_next->rspec == lte->rspec);
+                            next2 = next2->next)
+                       {
+                               lte_last = lte_next;
+                               stream_count++;
+                       }
+                       if (stream_count > 1) {
+                               /* Reading multiple streams combined into a
+                                * single WIM resource.  They are in the stream
+                                * list, sorted by offset; @lte specifies the
+                                * first stream in the resource that needs to be
+                                * read and @lte_last specifies the last stream
+                                * in the resource that needs to be read.  */
+
+                               DEBUG("Reading %zu streams combined in same "
+                                     "WIM resource", stream_count);
+
+                               next = next2;
+
+                               struct data_range ranges[stream_count];
+
+                               {
+                                       struct list_head *next3;
+                                       size_t i;
+                                       struct wim_lookup_table_entry *lte_cur;
+
+                                       next3 = cur;
+                                       for (i = 0; i < stream_count; i++) {
+                                               lte_cur = (struct wim_lookup_table_entry*)
+                                                       ((u8*)next3 - list_head_offset);
+                                               ranges[i].offset = lte_cur->offset_in_res;
+                                               ranges[i].size = lte_cur->size;
+                                               next3 = next3->next;
+                                       }
+                               }
+
+                               struct streamifier_context streamifier_ctx = {
+                                       .cbs                    = *sink_cbs,
+                                       .cur_stream             = lte,
+                                       .next_stream            = next_stream(lte, list_head_offset),
+                                       .cur_stream_offset      = 0,
+                                       .final_stream           = lte_last,
+                                       .list_head_offset       = list_head_offset,
+                               };
+
+                               ret = read_compressed_wim_resource(lte->rspec,
+                                                                  ranges,
+                                                                  stream_count,
+                                                                  streamifier_cb,
+                                                                  &streamifier_ctx);
+
+                               if (ret) {
+                                       if (streamifier_ctx.cur_stream_offset != 0) {
+                                               ret = (*streamifier_ctx.cbs.end_stream)
+                                                       (streamifier_ctx.cur_stream,
+                                                        ret,
+                                                        streamifier_ctx.cbs.end_stream_ctx);
+                                       }
+                                       return ret;
+                               }
+                               continue;
+                       }
+               }
+
+               ret = read_full_stream_with_cbs(lte, sink_cbs);
+               if (ret && ret != BEGIN_STREAM_STATUS_SKIP_STREAM)
+                       return ret;
+       }
+       return 0;
 }
 
+/* Extract the first @size bytes of the specified stream.
+ *
+ * If @size specifies the full uncompressed size of the stream, then the SHA1
+ * message digest of the uncompressed stream is checked while being extracted.
+ *
+ * The uncompressed data of the resource is passed in chunks of unspecified size
+ * to the @extract_chunk function, passing it @extract_chunk_arg.  */
+int
+extract_stream(struct wim_lookup_table_entry *lte, u64 size,
+              consume_data_callback_t extract_chunk, void *extract_chunk_arg)
+{
+       wimlib_assert(size <= lte->size);
+       if (size == lte->size) {
+               /* Do SHA1.  */
+               struct read_stream_list_callbacks cbs = {
+                       .consume_chunk          = extract_chunk,
+                       .consume_chunk_ctx      = extract_chunk_arg,
+               };
+               return read_full_stream_with_sha1(lte, &cbs);
+       } else {
+               /* Don't do SHA1.  */
+               return read_stream_prefix(lte, size, extract_chunk,
+                                         extract_chunk_arg);
+       }
+}
 
-static int
-sha1_chunk(const void *buf, size_t len, void *ctx)
+/* A consume_data_callback_t implementation that writes the chunk of data to a
+ * file descriptor.  */
+int
+extract_chunk_to_fd(const void *chunk, size_t size, void *_fd_p)
 {
-       sha1_update(ctx, buf, len);
+       struct filedes *fd = _fd_p;
+
+       int ret = full_write(fd, chunk, size);
+       if (ret) {
+               ERROR_WITH_ERRNO("Error writing to file descriptor");
+               return ret;
+       }
        return 0;
 }
 
-/* Calculate the SHA1 message digest of a stream, storing it in @lte->hash.  */
+/* Extract the first @size bytes of the specified stream to the specified file
+ * descriptor.  */
 int
-sha1_stream(struct wim_lookup_table_entry *lte)
+extract_stream_to_fd(struct wim_lookup_table_entry *lte,
+                    struct filedes *fd, u64 size)
 {
-       int ret;
-       SHA_CTX sha_ctx;
-
-       sha1_init(&sha_ctx);
-       ret = read_stream_prefix(lte, lte->size,
-                                sha1_chunk, lte_cchunk_size(lte),
-                                &sha_ctx, 0);
-       if (ret == 0)
-               sha1_final(lte->hash, &sha_ctx);
+       return extract_stream(lte, size, extract_chunk_to_fd, fd);
+}
 
-       return ret;
+/* Calculate the SHA1 message digest of a stream and store it in @lte->hash.  */
+int
+sha1_stream(struct wim_lookup_table_entry *lte)
+{
+       wimlib_assert(lte->unhashed);
+       struct read_stream_list_callbacks cbs = {
+       };
+       return read_full_stream_with_sha1(lte, &cbs);
 }
 
-/* Convert a WIM resource header to a stand-alone resource specification.  */
+/* Convert a short WIM resource header to a stand-alone WIM resource
+ * specification.  */
 void
 wim_res_hdr_to_spec(const struct wim_reshdr *reshdr, WIMStruct *wim,
-                   struct wim_resource_spec *spec)
+                   struct wim_resource_spec *rspec)
 {
-       spec->wim = wim;
-       spec->offset_in_wim = reshdr->offset_in_wim;
-       spec->size_in_wim = reshdr->size_in_wim;
-       spec->uncompressed_size = reshdr->uncompressed_size;
-       INIT_LIST_HEAD(&spec->lte_list);
-       spec->flags = reshdr->flags;
-       spec->is_pipable = wim_is_pipable(wim);
-       if (spec->flags & (WIM_RESHDR_FLAG_COMPRESSED | WIM_RESHDR_FLAG_CONCAT)) {
-               spec->ctype = wim->compression_type;
-               spec->cchunk_size = wim->chunk_size;
-       } else {
-               spec->ctype = WIMLIB_COMPRESSION_TYPE_NONE;
-               spec->cchunk_size = 0;
-       }
+       rspec->wim = wim;
+       rspec->offset_in_wim = reshdr->offset_in_wim;
+       rspec->size_in_wim = reshdr->size_in_wim;
+       rspec->uncompressed_size = reshdr->uncompressed_size;
+       INIT_LIST_HEAD(&rspec->stream_list);
+       rspec->flags = reshdr->flags;
+       rspec->is_pipable = wim_is_pipable(wim);
 }
 
 /* Convert a stand-alone resource specification to a WIM resource header.  */
@@ -1060,29 +1361,20 @@ wim_res_spec_to_hdr(const struct wim_resource_spec *rspec,
 
 /* Translates a WIM resource header from the on-disk format into an in-memory
  * format.  */
-int
+void
 get_wim_reshdr(const struct wim_reshdr_disk *disk_reshdr,
               struct wim_reshdr *reshdr)
 {
        reshdr->offset_in_wim = le64_to_cpu(disk_reshdr->offset_in_wim);
        reshdr->size_in_wim = (((u64)disk_reshdr->size_in_wim[0] <<  0) |
-                             ((u64)disk_reshdr->size_in_wim[1] <<  8) |
-                             ((u64)disk_reshdr->size_in_wim[2] << 16) |
-                             ((u64)disk_reshdr->size_in_wim[3] << 24) |
-                             ((u64)disk_reshdr->size_in_wim[4] << 32) |
-                             ((u64)disk_reshdr->size_in_wim[5] << 40) |
-                             ((u64)disk_reshdr->size_in_wim[6] << 48));
+                              ((u64)disk_reshdr->size_in_wim[1] <<  8) |
+                              ((u64)disk_reshdr->size_in_wim[2] << 16) |
+                              ((u64)disk_reshdr->size_in_wim[3] << 24) |
+                              ((u64)disk_reshdr->size_in_wim[4] << 32) |
+                              ((u64)disk_reshdr->size_in_wim[5] << 40) |
+                              ((u64)disk_reshdr->size_in_wim[6] << 48));
        reshdr->uncompressed_size = le64_to_cpu(disk_reshdr->uncompressed_size);
        reshdr->flags = disk_reshdr->flags;
-
-       /* Truncate numbers to 62 bits to avoid possible overflows.  */
-       if (reshdr->offset_in_wim & 0xc000000000000000ULL)
-               return WIMLIB_ERR_INVALID_LOOKUP_TABLE_ENTRY;
-
-       if (reshdr->uncompressed_size & 0xc000000000000000ULL)
-               return WIMLIB_ERR_INVALID_LOOKUP_TABLE_ENTRY;
-
-       return 0;
 }
 
 /* Translates a WIM resource header from an in-memory format into the on-disk