]> wimlib.net Git - wimlib/blobdiff - src/write.c
write_stream_list(): Write streams uncompressed when advantageous
[wimlib] / src / write.c
index 706d70ec823baf1823a4ead33f6dbab99651ae6d..0aacdf13e04fc57e5abd3574c7321a929201c99c 100644 (file)
@@ -34,7 +34,7 @@
 #  include <sys/file.h>
 #endif
 
-#include "wimlib/compress_chunks.h"
+#include "wimlib/chunk_compressor.h"
 #include "wimlib/endianness.h"
 #include "wimlib/error.h"
 #include "wimlib/file_io.h"
 #  include <alloca.h>
 #endif
 
+/* wimlib internal flags used when writing resources.  */
+#define WRITE_RESOURCE_FLAG_RECOMPRESS         0x00000001
+#define WRITE_RESOURCE_FLAG_PIPABLE            0x00000002
+#define WRITE_RESOURCE_FLAG_PACK_STREAMS       0x00000004
+
 static inline int
 write_flags_to_resource_flags(int write_flags)
 {
        int write_resource_flags = 0;
 
        if (write_flags & WIMLIB_WRITE_FLAG_RECOMPRESS)
-               write_resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS;
+               write_resource_flags |= WRITE_RESOURCE_FLAG_RECOMPRESS;
        if (write_flags & WIMLIB_WRITE_FLAG_PIPABLE)
-               write_resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE;
+               write_resource_flags |= WRITE_RESOURCE_FLAG_PIPABLE;
        if (write_flags & WIMLIB_WRITE_FLAG_PACK_STREAMS)
-               write_resource_flags |= WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS;
+               write_resource_flags |= WRITE_RESOURCE_FLAG_PACK_STREAMS;
        return write_resource_flags;
 }
 
@@ -149,7 +154,7 @@ can_raw_copy(const struct wim_lookup_table_entry *lte,
 {
        const struct wim_resource_spec *rspec;
 
-       if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_RECOMPRESS)
+       if (write_resource_flags & WRITE_RESOURCE_FLAG_RECOMPRESS)
                return false;
 
        if (out_ctype == WIMLIB_COMPRESSION_TYPE_NONE)
@@ -160,7 +165,7 @@ can_raw_copy(const struct wim_lookup_table_entry *lte,
 
        rspec = lte->rspec;
 
-       if (rspec->is_pipable != !!(write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE))
+       if (rspec->is_pipable != !!(write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE))
                return false;
 
 
@@ -172,7 +177,7 @@ can_raw_copy(const struct wim_lookup_table_entry *lte,
        }
 
        if ((rspec->flags & WIM_RESHDR_FLAG_PACKED_STREAMS) &&
-           (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS))
+           (write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS))
        {
                /* Packed resource: Such resources may contain multiple streams,
                 * and in general only a subset of them need to be written.  As
@@ -263,20 +268,6 @@ write_pwm_stream_header(const struct wim_lookup_table_entry *lte,
        return ret;
 }
 
-#if 0
-static int
-seek_and_truncate(struct filedes *out_fd, off_t offset)
-{
-       if (filedes_seek(out_fd, offset) == -1 ||
-           ftruncate(out_fd->fd, offset))
-       {
-               ERROR_WITH_ERRNO("Failed to truncate output WIM file");
-               return WIMLIB_ERR_WRITE;
-       }
-       return 0;
-}
-#endif
-
 struct write_streams_progress_data {
        wimlib_progress_func_t progress_func;
        union wimlib_progress_info progress;
@@ -286,31 +277,32 @@ struct write_streams_progress_data {
 
 static void
 do_write_streams_progress(struct write_streams_progress_data *progress_data,
-                         struct wim_lookup_table_entry *lte,
-                         bool stream_discarded)
+                         u64 size,
+                         bool discarded,
+                         struct wim_lookup_table_entry *cur_stream)
 {
        union wimlib_progress_info *progress = &progress_data->progress;
        bool new_wim_part;
 
-       if (stream_discarded) {
-               progress->write_streams.total_bytes -= lte->size;
+       if (discarded) {
+               progress->write_streams.total_bytes -= size;
                if (progress_data->next_progress != ~(uint64_t)0 &&
                    progress_data->next_progress > progress->write_streams.total_bytes)
                {
                        progress_data->next_progress = progress->write_streams.total_bytes;
                }
        } else {
-               progress->write_streams.completed_bytes += lte->size;
+               progress->write_streams.completed_bytes += size;
        }
        new_wim_part = false;
-       if (lte->resource_location == RESOURCE_IN_WIM &&
-           lte->rspec->wim != progress_data->prev_wim_part)
+       if (cur_stream->resource_location == RESOURCE_IN_WIM &&
+           cur_stream->rspec->wim != progress_data->prev_wim_part)
        {
                if (progress_data->prev_wim_part) {
                        new_wim_part = true;
                        progress->write_streams.completed_parts++;
                }
-               progress_data->prev_wim_part = lte->rspec->wim;
+               progress_data->prev_wim_part = cur_stream->rspec->wim;
        }
        progress->write_streams.completed_streams++;
        if (progress_data->progress_func
@@ -431,7 +423,7 @@ begin_chunk_table(struct write_streams_ctx *ctx, u64 res_expected_size)
         * potentially decreasing the number of chunk entries needed.  */
        expected_num_chunks = DIV_ROUND_UP(res_expected_size, ctx->out_chunk_size);
        expected_num_chunk_entries = expected_num_chunks;
-       if (!(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS))
+       if (!(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS))
                expected_num_chunk_entries--;
 
        /* Make sure the chunk_csizes array is long enough to store the
@@ -456,7 +448,7 @@ begin_chunk_table(struct write_streams_ctx *ctx, u64 res_expected_size)
 
        ctx->chunk_index = 0;
 
-       if (!(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE)) {
+       if (!(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE)) {
                /* Reserve space for the chunk table in the output file.  In the
                 * case of packed resources this reserves the upper bound for
                 * the needed space, not necessarily the exact space which will
@@ -466,7 +458,7 @@ begin_chunk_table(struct write_streams_ctx *ctx, u64 res_expected_size)
                reserve_size = expected_num_chunk_entries *
                               get_chunk_entry_size(res_expected_size,
                                                    ctx->write_resource_flags);
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS)
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS)
                        reserve_size += sizeof(struct alt_chunk_table_header_disk);
                memset(ctx->chunk_csizes, 0, reserve_size);
                ret = full_write(ctx->out_fd, ctx->chunk_csizes, reserve_size);
@@ -508,7 +500,7 @@ end_chunk_table(struct write_streams_ctx *ctx, u64 res_actual_size,
 
        actual_num_chunks = ctx->chunk_index;
        actual_num_chunk_entries = actual_num_chunks;
-       if (!(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS))
+       if (!(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS))
                actual_num_chunk_entries--;
 
        chunk_entry_size = get_chunk_entry_size(res_actual_size,
@@ -520,7 +512,7 @@ end_chunk_table(struct write_streams_ctx *ctx, u64 res_actual_size,
        if (chunk_entry_size == 4) {
                aliased_le32_t *entries = (aliased_le32_t*)ctx->chunk_csizes;
 
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                        for (size_t i = 0; i < actual_num_chunk_entries; i++)
                                entries[i] = cpu_to_le32(ctx->chunk_csizes[i]);
                } else {
@@ -534,7 +526,7 @@ end_chunk_table(struct write_streams_ctx *ctx, u64 res_actual_size,
        } else {
                aliased_le64_t *entries = (aliased_le64_t*)ctx->chunk_csizes;
 
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                        for (size_t i = 0; i < actual_num_chunk_entries; i++)
                                entries[i] = cpu_to_le64(ctx->chunk_csizes[i]);
                } else {
@@ -549,9 +541,9 @@ end_chunk_table(struct write_streams_ctx *ctx, u64 res_actual_size,
 
        size_t chunk_table_size = actual_num_chunk_entries * chunk_entry_size;
        u64 res_start_offset;
-       u64 res_end_offset = ctx->out_fd->offset;
+       u64 res_end_offset;
 
-       if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE) {
+       if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE) {
                ret = full_write(ctx->out_fd, ctx->chunk_csizes, chunk_table_size);
                if (ret)
                        goto error;
@@ -564,7 +556,7 @@ end_chunk_table(struct write_streams_ctx *ctx, u64 res_actual_size,
 
                chunk_table_offset = ctx->chunks_start_offset - chunk_table_size;
 
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                        struct alt_chunk_table_header_disk hdr;
 
                        hdr.res_usize = cpu_to_le64(res_actual_size);
@@ -658,7 +650,6 @@ write_stream_begin_read(struct wim_lookup_table_entry *lte,
        if (ctx->lookup_table != NULL && lte->unhashed && !lte->unique_size) {
 
                wimlib_assert(!is_partial_res);
-               wimlib_assert(ctx->lookup_table != NULL);
 
                struct wim_lookup_table_entry *lte_new;
 
@@ -680,12 +671,12 @@ write_stream_begin_read(struct wim_lookup_table_entry *lte,
                                DEBUG("Discarding duplicate stream of "
                                      "length %"PRIu64, lte->size);
                                do_write_streams_progress(&ctx->progress_data,
-                                                         lte, true);
+                                                         lte->size, true, lte);
                                list_del(&lte->write_streams_list);
                                list_del(&lte->lookup_table_list);
                                if (lte_new->will_be_in_output_wim)
                                        lte_new->out_refcnt += lte->out_refcnt;
-                               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS)
+                               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS)
                                        ctx->cur_write_res_size -= lte->size;
                                free_lookup_table_entry(lte);
                                return BEGIN_STREAM_STATUS_SKIP_STREAM;
@@ -713,6 +704,33 @@ write_stream_begin_read(struct wim_lookup_table_entry *lte,
        return 0;
 }
 
+static int
+write_stream_uncompressed(struct wim_lookup_table_entry *lte,
+                         struct filedes *out_fd)
+{
+       int ret;
+
+       if (-1 == lseek(out_fd->fd, lte->out_reshdr.offset_in_wim, SEEK_SET) ||
+           0 != ftruncate(out_fd->fd, lte->out_reshdr.offset_in_wim))
+       {
+               ERROR_WITH_ERRNO("Can't truncate output file to "
+                                "offset %"PRIu64, lte->out_reshdr.offset_in_wim);
+               return WIMLIB_ERR_WRITE;
+       }
+
+       out_fd->offset = lte->out_reshdr.offset_in_wim;
+
+       ret = extract_stream_to_fd(lte, out_fd, lte->size);
+       if (ret)
+               return ret;
+
+       wimlib_assert(out_fd->offset - lte->out_reshdr.offset_in_wim == lte->size);
+       lte->out_reshdr.size_in_wim = lte->size;
+       lte->out_reshdr.flags &= ~(WIM_RESHDR_FLAG_COMPRESSED |
+                                  WIM_RESHDR_FLAG_PACKED_STREAMS);
+       return 0;
+}
+
 /* Write the next chunk of (typically compressed) data to the output WIM,
  * handling the writing of the chunk table.  */
 static int
@@ -721,17 +739,17 @@ write_chunk(struct write_streams_ctx *ctx, const void *cchunk,
 {
        int ret;
 
+       struct wim_lookup_table_entry *lte;
+
+       lte = list_entry(ctx->pending_streams.next,
+                        struct wim_lookup_table_entry, write_streams_list);
+
        if (ctx->cur_write_res_offset == 0 &&
-           !(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS))
+           !(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS))
        {
                /* Starting to write a new stream in non-packed mode.  */
 
-               struct wim_lookup_table_entry *lte;
-
-               lte = list_entry(ctx->pending_streams.next,
-                                struct wim_lookup_table_entry, write_streams_list);
-
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE) {
                        int additional_reshdr_flags = 0;
                        if (ctx->compressor != NULL)
                                additional_reshdr_flags |= WIM_RESHDR_FLAG_COMPRESSED;
@@ -757,7 +775,7 @@ write_chunk(struct write_streams_ctx *ctx, const void *cchunk,
 
               /* If writing a pipable WIM, before the chunk data write a chunk
                * header that provides the compressed chunk size.  */
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE) {
                        struct pwm_chunk_hdr chunk_hdr = {
                                .compressed_size = cpu_to_le32(csize),
                        };
@@ -775,8 +793,11 @@ write_chunk(struct write_streams_ctx *ctx, const void *cchunk,
 
        ctx->cur_write_res_offset += usize;
 
+       do_write_streams_progress(&ctx->progress_data,
+                                 usize, false, lte);
+
        if (ctx->cur_write_res_offset == ctx->cur_write_res_size &&
-           !(ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS))
+           !(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS))
        {
                struct wim_lookup_table_entry *lte;
 
@@ -786,18 +807,36 @@ write_chunk(struct write_streams_ctx *ctx, const void *cchunk,
 
                /* Finished writing a stream in non-packed mode.  */
 
-               do_write_streams_progress(&ctx->progress_data, lte, false);
-
                ret = end_write_resource(ctx, &lte->out_reshdr);
                if (ret)
                        return ret;
 
-               wimlib_assert(lte->out_reshdr.uncompressed_size == lte->size);
-
                lte->out_reshdr.flags = filter_resource_flags(lte->flags);
                if (ctx->compressor != NULL)
                        lte->out_reshdr.flags |= WIM_RESHDR_FLAG_COMPRESSED;
 
+               if (ctx->compressor != NULL &&
+                   lte->out_reshdr.size_in_wim >= lte->out_reshdr.uncompressed_size &&
+                   !(ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE) &&
+                   !(lte->flags & WIM_RESHDR_FLAG_PACKED_STREAMS))
+               {
+                       /* Stream did not compress to less than its original
+                        * size.  If we're not writing a pipable WIM (which
+                        * could mean the output file descriptor is
+                        * non-seekable), and the stream isn't located in a
+                        * resource pack (which would make reading it again
+                        * costly), truncate the file to the start of the stream
+                        * and write it uncompressed instead.  */
+                       DEBUG("Stream of size %"PRIu64" did not compress to "
+                             "less than original size; writing uncompressed.",
+                             lte->size);
+                       ret = write_stream_uncompressed(lte, ctx->out_fd);
+                       if (ret)
+                               return ret;
+               }
+
+               wimlib_assert(lte->out_reshdr.uncompressed_size == lte->size);
+
                list_del(&lte->write_streams_list);
                ctx->cur_write_res_offset = 0;
        }
@@ -863,7 +902,7 @@ write_stream_process_chunk(const void *chunk, size_t size, void *_ctx)
                const u8 *resized_chunk;
                size_t needed_chunk_size;
 
-               if (ctx->write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+               if (ctx->write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                        needed_chunk_size = ctx->out_chunk_size;
                } else {
                        u64 res_bytes_remaining;
@@ -1041,7 +1080,8 @@ write_raw_copy_resource(struct wim_resource_spec *in_rspec,
                out_offset_in_wim += sizeof(struct pwm_stream_hdr);
        }
        in_fd = &in_rspec->wim->in_fd;
-       while (cur_read_offset != end_read_offset) {
+       wimlib_assert(cur_read_offset != end_read_offset);
+       do {
 
                bytes_to_read = min(sizeof(buf), end_read_offset - cur_read_offset);
 
@@ -1054,7 +1094,8 @@ write_raw_copy_resource(struct wim_resource_spec *in_rspec,
                        return ret;
 
                cur_read_offset += bytes_to_read;
-       }
+
+       } while (cur_read_offset != end_read_offset);
 
        list_for_each_entry(lte, &in_rspec->stream_list, rspec_node) {
                if (lte->will_be_in_output_wim) {
@@ -1073,7 +1114,8 @@ write_raw_copy_resource(struct wim_resource_spec *in_rspec,
  * file being written.  */
 static int
 write_raw_copy_resources(struct list_head *raw_copy_resources,
-                        struct filedes *out_fd)
+                        struct filedes *out_fd,
+                        struct write_streams_progress_data *progress_data)
 {
        struct wim_lookup_table_entry *lte;
        int ret;
@@ -1082,6 +1124,7 @@ write_raw_copy_resources(struct list_head *raw_copy_resources,
                ret = write_raw_copy_resource(lte->rspec, out_fd);
                if (ret)
                        return ret;
+               do_write_streams_progress(progress_data, lte->size, false, lte);
        }
        return 0;
 }
@@ -1130,6 +1173,120 @@ remove_zero_length_streams(struct list_head *stream_list)
        }
 }
 
+/*
+ * Write a list of streams to the output WIM file.
+ *
+ * @stream_list
+ *     The list of streams to write, specifies a list of `struct
+ *     wim_lookup_table_entry's linked by the 'write_streams_list' member.
+ *
+ * @out_fd
+ *     The file descriptor, opened for writing, to which to write the streams.
+ *
+ * @write_resource_flags
+ *     Flags to modify how the streams are written:
+ *
+ *     WRITE_RESOURCE_FLAG_RECOMPRESS:
+ *             Force compression of all resources, even if they could otherwise
+ *             be re-used by caping the raw data, due to being located in a WIM
+ *             file with compatible compression parameters.
+ *
+ *     WRITE_RESOURCE_FLAG_PIPABLE:
+ *             Write the resources in the wimlib-specific pipable format, and
+ *             furthermore do so in such a way that no seeking backwards in
+ *             @out_fd will be performed (so it may be a pipe, contrary to the
+ *             default behavior).
+ *
+ *     WRITE_RESOURCE_FLAG_PACK_STREAMS:
+ *             Pack all the streams into a single resource rather than writing
+ *             them in separate resources.  This format is only valid if the
+ *             WIM version number is WIM_VERSION_PACKED_STREAMS.  This flag
+ *             currently may not be combined with WRITE_RESOURCE_FLAG_PIPABLE.
+ *
+ * @out_ctype
+ *     Compression format to use to write the output streams, specified as one
+ *     of the WIMLIB_COMPRESSION_TYPE_* constants, excepting
+ *     WIMLIB_COMPRESSION_TYPE_INVALID but including
+ *     WIMLIB_COMPRESSION_TYPE_NONE.
+ *
+ * @out_chunk_size
+ *     Chunk size to use to write the streams.  It must be a valid chunk size
+ *     for the specified compression format @out_ctype, unless @out_ctype is
+ *     WIMLIB_COMPRESSION_TYPE_NONE, in which case this parameter is ignored.
+ *
+ * @num_threads
+ *     Number of threads to use to compress data.  If 0, a default number of
+ *     threads will be chosen.  The number of threads still may be decreased
+ *     from the specified value if insufficient memory is detected.
+ *
+ * @lookup_table
+ *     If on-the-fly deduplication of unhashed streams is desired, this
+ *     parameter must be pointer to the lookup table for the WIMStruct on whose
+ *     behalf the streams are being written.  Otherwise, this parameter can be
+ *     NULL.
+ *
+ * @filter_ctx
+ *     If on-the-fly deduplication of unhashed streams is desired, this
+ *     parameter can be a pointer to a context for stream filtering used to
+ *     detect whether the duplicate stream has been hard-filtered or not.  If
+ *     no streams are hard-filtered or no streams are unhashed, this parameter
+ *     can be NULL.
+ *
+ * @progress_func
+ *     If non-NULL, a progress function that will be called periodically with
+ *     WIMLIB_PROGRESS_MSG_WRITE_STREAMS messages.  Note that on-the-fly
+ *     deduplication of unhashed streams may result in the total bytes provided
+ *     in the progress data to decrease from one message to the next.
+ *
+ * This function will write the streams in @stream_list to resources in
+ * consecutive positions in the output WIM file, or to a single packed resource
+ * if WRITE_RESOURCE_FLAG_PACK_STREAMS was specified in @write_resource_flags.
+ * In both cases, the @out_reshdr of the `struct wim_lookup_table_entry' for
+ * each stream written will be updated to specify its location, size, and flags
+ * in the output WIM.  In the packed resource case,
+ * WIM_RESHDR_FLAG_PACKED_STREAMS shall be set in the @flags field of the
+ * @out_reshdr, and @out_res_offset_in_wim and @out_res_size_in_wim will also
+ * be set to the offset and size, respectively, in the output WIM of the full
+ * packed resource containing the corresponding stream.
+ *
+ * Each of the streams to write may be in any location supported by the
+ * resource-handling code (specifically, read_stream_list()), such as the
+ * contents of external file that has been logically added to the output WIM, or
+ * a stream in another WIM file that has been imported, or even stream in the
+ * "same" WIM file of which a modified copy is being written.  In the case that
+ * a stream is already in a WIM file and uses compatible compression parameters,
+ * by default this function will re-use the raw data instead of decompressing
+ * it, then recompressing it; however, with WRITE_RESOURCE_FLAG_RECOMPRESS
+ * specified in @write_resource_flags, this is not done.
+ *
+ * As a further requirement, this function requires that the
+ * @will_be_in_output_wim member be set on all streams in @stream_list as well
+ * as any other streams not in @stream_list that will be in the output WIM file,
+ * but not on any other streams in the output WIM's lookup table or sharing a
+ * packed resource with a stream in @stream_list.  Still furthermore, if
+ * on-the-fly deduplication of streams is possible, then all streams in
+ * @stream_list must also be linked by @lookup_table_list along with any other
+ * streams that have @will_be_in_output_wim set.
+ *
+ * This function handles on-the-fly deduplication of streams for which SHA1
+ * message digests have not yet been calculated and it is therefore known
+ * whether such streams are already in @stream_list or in the WIM's lookup table
+ * at all.  If @lookup_table is non-NULL, then each stream in @stream_list that
+ * has @unhashed set but not @unique_size set is checksummed immediately before
+ * it would otherwise be read for writing in order to determine if it is
+ * identical to another stream already being written or one that would be
+ * filtered out of the output WIM using stream_filtered() with the context
+ * @filter_ctx.  Each such duplicate stream will be removed from @stream_list, its
+ * reference count transfered to the pre-existing duplicate stream, its memory
+ * freed, and will not be written.  Alternatively, if a stream in @stream_list
+ * is a duplicate with any stream in @lookup_table that has not been marked for
+ * writing or would not be hard-filtered, it is freed and the pre-existing
+ * duplicate is written instead, taking ownership of the reference count and
+ * slot in the @lookup_table_list.
+ *
+ * Returns 0 if all streams were written successfully (or did not need to be
+ * written); otherwise a non-zero error code.
+ */
 static int
 write_stream_list(struct list_head *stream_list,
                  struct filedes *out_fd,
@@ -1139,13 +1296,18 @@ write_stream_list(struct list_head *stream_list,
                  unsigned num_threads,
                  struct wim_lookup_table *lookup_table,
                  struct filter_context *filter_ctx,
-                 struct wimlib_lzx_context **comp_ctx,
                  wimlib_progress_func_t progress_func)
 {
        int ret;
        struct write_streams_ctx ctx;
        struct list_head raw_copy_resources;
 
+       wimlib_assert((write_resource_flags &
+                      (WRITE_RESOURCE_FLAG_PACK_STREAMS |
+                       WRITE_RESOURCE_FLAG_PIPABLE)) !=
+                               (WRITE_RESOURCE_FLAG_PACK_STREAMS |
+                                WRITE_RESOURCE_FLAG_PIPABLE));
+
        remove_zero_length_streams(stream_list);
 
        if (list_empty(stream_list)) {
@@ -1170,13 +1332,15 @@ write_stream_list(struct list_head *stream_list,
        ctx.write_resource_flags = write_resource_flags;
        ctx.filter_ctx = filter_ctx;
 
-       if (out_chunk_size <= STACK_MAX) {
-               ctx.chunk_buf = alloca(out_chunk_size);
-       } else {
-               ctx.chunk_buf = MALLOC(out_chunk_size);
-               if (ctx.chunk_buf == NULL) {
-                       ret = WIMLIB_ERR_NOMEM;
-                       goto out_destroy_context;
+       if (out_chunk_size != 0) {
+               if (out_chunk_size <= STACK_MAX) {
+                       ctx.chunk_buf = alloca(out_chunk_size);
+               } else {
+                       ctx.chunk_buf = MALLOC(out_chunk_size);
+                       if (ctx.chunk_buf == NULL) {
+                               ret = WIMLIB_ERR_NOMEM;
+                               goto out_destroy_context;
+                       }
                }
        }
        ctx.chunk_buf_filled = 0;
@@ -1212,6 +1376,13 @@ write_stream_list(struct list_head *stream_list,
         * bytes needing to be compressed is less 2000000 (heuristic value).  */
        if (out_ctype != WIMLIB_COMPRESSION_TYPE_NONE) {
 
+               if (out_ctype == WIMLIB_COMPRESSION_TYPE_LZMS &&
+                   ctx.lookup_table != NULL) {
+                       WARNING("LZMS compression not implemented; data will "
+                               "actually be written uncompressed.");
+               }
+
+       #ifdef ENABLE_MULTITHREADED_COMPRESSION
                if (ctx.num_bytes_to_compress >= 2000000) {
                        ret = new_parallel_chunk_compressor(out_ctype,
                                                            out_chunk_size,
@@ -1222,17 +1393,11 @@ write_stream_list(struct list_head *stream_list,
                                      "(status %d)", ret);
                        }
                }
+       #endif
 
                if (ctx.compressor == NULL) {
-                       if (out_ctype == WIMLIB_COMPRESSION_TYPE_LZX) {
-                               ret = wimlib_lzx_alloc_context(out_chunk_size,
-                                                              NULL,
-                                                              comp_ctx);
-                               if (ret)
-                                       goto out_destroy_context;
-                       }
                        ret = new_serial_chunk_compressor(out_ctype, out_chunk_size,
-                                                         *comp_ctx, &ctx.compressor);
+                                                         &ctx.compressor);
                        if (ret)
                                goto out_destroy_context;
                }
@@ -1248,7 +1413,12 @@ write_stream_list(struct list_head *stream_list,
 
        INIT_LIST_HEAD(&ctx.pending_streams);
 
-       if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+       if (ctx.progress_data.progress_func) {
+               (*ctx.progress_data.progress_func)(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
+                                                  &ctx.progress_data.progress);
+       }
+
+       if (write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                ret = begin_write_resource(&ctx, ctx.num_bytes_to_compress);
                if (ret)
                        goto out_destroy_context;
@@ -1280,7 +1450,7 @@ write_stream_list(struct list_head *stream_list,
        if (ret)
                goto out_destroy_context;
 
-       if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS) {
+       if (write_resource_flags & WRITE_RESOURCE_FLAG_PACK_STREAMS) {
                struct wim_reshdr reshdr;
                struct wim_lookup_table_entry *lte;
                u64 offset_in_res;
@@ -1312,7 +1482,8 @@ write_stream_list(struct list_head *stream_list,
 out_write_raw_copy_resources:
        /* Copy any compressed resources for which the raw data can be reused
         * without decompression.  */
-       ret = write_raw_copy_resources(&raw_copy_resources, ctx.out_fd);
+       ret = write_raw_copy_resources(&raw_copy_resources, ctx.out_fd,
+                                      &ctx.progress_data);
 
 out_destroy_context:
        if (out_chunk_size > STACK_MAX)
@@ -1329,21 +1500,19 @@ write_wim_resource(struct wim_lookup_table_entry *lte,
                   struct filedes *out_fd,
                   int out_ctype,
                   u32 out_chunk_size,
-                  int write_resource_flags,
-                  struct wimlib_lzx_context **comp_ctx)
+                  int write_resource_flags)
 {
        LIST_HEAD(stream_list);
        list_add(&lte->write_streams_list, &stream_list);
        lte->will_be_in_output_wim = 1;
        return write_stream_list(&stream_list,
                                 out_fd,
-                                write_resource_flags & ~WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS,
+                                write_resource_flags & ~WRITE_RESOURCE_FLAG_PACK_STREAMS,
                                 out_ctype,
                                 out_chunk_size,
                                 1,
                                 NULL,
                                 NULL,
-                                comp_ctx,
                                 NULL);
 }
 
@@ -1354,8 +1523,7 @@ write_wim_resource_from_buffer(const void *buf, size_t buf_size,
                               u32 out_chunk_size,
                               struct wim_reshdr *out_reshdr,
                               u8 *hash,
-                              int write_resource_flags,
-                              struct wimlib_lzx_context **comp_ctx)
+                              int write_resource_flags)
 {
        int ret;
        struct wim_lookup_table_entry *lte;
@@ -1372,7 +1540,7 @@ write_wim_resource_from_buffer(const void *buf, size_t buf_size,
        lte->size               = buf_size;
        lte->flags              = reshdr_flags;
 
-       if (write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE) {
+       if (write_resource_flags & WRITE_RESOURCE_FLAG_PIPABLE) {
                sha1_buffer(buf, buf_size, lte->hash);
                lte->unhashed = 0;
        } else {
@@ -1380,7 +1548,7 @@ write_wim_resource_from_buffer(const void *buf, size_t buf_size,
        }
 
        ret = write_wim_resource(lte, out_fd, out_ctype, out_chunk_size,
-                                write_resource_flags, comp_ctx);
+                                write_resource_flags);
        if (ret)
                goto out_free_lte;
 
@@ -1787,7 +1955,6 @@ write_wim_streams(WIMStruct *wim, int image, int write_flags,
                                 num_threads,
                                 wim->lookup_table,
                                 filter_ctx,
-                                &wim->lzx_context,
                                 progress_func);
 }
 
@@ -1807,7 +1974,7 @@ write_wim_metadata_resources(WIMStruct *wim, int image, int write_flags,
 
        write_resource_flags = write_flags_to_resource_flags(write_flags);
 
-       write_resource_flags &= ~WIMLIB_WRITE_RESOURCE_FLAG_PACK_STREAMS;
+       write_resource_flags &= ~WRITE_RESOURCE_FLAG_PACK_STREAMS;
 
        DEBUG("Writing metadata resources (offset=%"PRIu64")",
              wim->out_fd.offset);
@@ -1847,8 +2014,7 @@ write_wim_metadata_resources(WIMStruct *wim, int image, int write_flags,
                                                 &wim->out_fd,
                                                 wim->out_compression_type,
                                                 wim->out_chunk_size,
-                                                write_resource_flags,
-                                                &wim->lzx_context);
+                                                write_resource_flags);
                }
                if (ret)
                        return ret;
@@ -1968,8 +2134,7 @@ write_wim_lookup_table(WIMStruct *wim, int image, int write_flags,
                                                       &wim->out_fd,
                                                       wim->hdr.part_number,
                                                       out_reshdr,
-                                                      write_flags_to_resource_flags(write_flags),
-                                                      &wim->lzx_context);
+                                                      write_flags_to_resource_flags(write_flags));
 }
 
 /*
@@ -2268,7 +2433,7 @@ write_pipable_wim(WIMStruct *wim, int image, int write_flags,
        /* Write extra copy of the XML data.  */
        ret = write_wim_xml_data(wim, image, WIM_TOTALBYTES_OMIT,
                                 &xml_reshdr,
-                                WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE);
+                                WRITE_RESOURCE_FLAG_PIPABLE);
        if (ret)
                return ret;
 
@@ -2434,7 +2599,10 @@ write_wim_part(WIMStruct *wim,
                            WIMLIB_WRITE_FLAG_PACK_STREAMS))
                                    == (WIMLIB_WRITE_FLAG_PIPABLE |
                                        WIMLIB_WRITE_FLAG_PACK_STREAMS))
+       {
+               ERROR("Cannot specify both PIPABLE and PACK_STREAMS!");
                return WIMLIB_ERR_INVALID_PARAM;
+       }
 
        /* Set appropriate magic number.  */
        if (write_flags & WIMLIB_WRITE_FLAG_PIPABLE)
@@ -2724,6 +2892,9 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
 
        DEBUG("Overwriting `%"TS"' in-place", wim->filename);
 
+       /* Save original header so it can be restored in case of error  */
+       memcpy(&hdr_save, &wim->hdr, sizeof(struct wim_header));
+
        /* Set default integrity flag.  */
        if (!(write_flags & (WIMLIB_WRITE_FLAG_CHECK_INTEGRITY |
                             WIMLIB_WRITE_FLAG_NO_CHECK_INTEGRITY)))
@@ -2733,8 +2904,17 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
        /* Set default packed flag.  */
        if (!(write_flags & (WIMLIB_WRITE_FLAG_PACK_STREAMS |
                             WIMLIB_WRITE_FLAG_NO_PACK_STREAMS)))
+       {
+       #if 0
                if (wim->hdr.wim_version == WIM_VERSION_PACKED_STREAMS)
                        write_flags |= WIMLIB_WRITE_FLAG_PACK_STREAMS;
+       #endif
+               /* wimlib allows multiple packs in a single WIM, but they don't
+                * seem to be compatible with WIMGAPI.  Write new streams
+                * unpacked.  */
+       } else if (write_flags & WIMLIB_WRITE_FLAG_PACK_STREAMS) {
+               wim->hdr.wim_version = WIM_VERSION_PACKED_STREAMS;
+       }
 
        /* Set additional flags for overwrite.  */
        write_flags |= WIMLIB_WRITE_FLAG_OVERWRITE |
@@ -2751,12 +2931,14 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
        if (wim->hdr.integrity_table_reshdr.offset_in_wim != 0 &&
            wim->hdr.integrity_table_reshdr.offset_in_wim < old_xml_end) {
                WARNING("Didn't expect the integrity table to be before the XML data");
-               return WIMLIB_ERR_RESOURCE_ORDER;
+               ret = WIMLIB_ERR_RESOURCE_ORDER;
+               goto out_restore_memory_hdr;
        }
 
        if (old_lookup_table_end > old_xml_begin) {
                WARNING("Didn't expect the lookup table to be after the XML data");
-               return WIMLIB_ERR_RESOURCE_ORDER;
+               ret = WIMLIB_ERR_RESOURCE_ORDER;
+               goto out_restore_memory_hdr;
        }
 
        /* Set @old_wim_end, which indicates the point beyond which we don't
@@ -2787,31 +2969,28 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
 
        ret = check_resource_offsets(wim, old_wim_end);
        if (ret)
-               return ret;
+               goto out_restore_memory_hdr;
 
        ret = prepare_stream_list_for_write(wim, WIMLIB_ALL_IMAGES, write_flags,
                                            &stream_list, &lookup_table_list,
                                            &filter_ctx);
        if (ret)
-               return ret;
+               goto out_restore_memory_hdr;
 
        ret = open_wim_writable(wim, wim->filename, O_RDWR);
        if (ret)
-               return ret;
+               goto out_restore_memory_hdr;
 
        ret = lock_wim(wim, wim->out_fd.fd);
        if (ret)
                goto out_close_wim;
 
-       /* Save original header so it can be restored in case of error  */
-       memcpy(&hdr_save, &wim->hdr, sizeof(struct wim_header));
-
        /* Set WIM_HDR_FLAG_WRITE_IN_PROGRESS flag in header. */
        wim->hdr.flags |= WIM_HDR_FLAG_WRITE_IN_PROGRESS;
        ret = write_wim_header_flags(wim->hdr.flags, &wim->out_fd);
        if (ret) {
                ERROR_WITH_ERRNO("Error updating WIM header flags");
-               goto out_restore_memory_hdr;
+               goto out_unlock_wim;
        }
 
        if (filedes_seek(&wim->out_fd, old_wim_end) == -1) {
@@ -2828,7 +3007,6 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
                                num_threads,
                                wim->lookup_table,
                                &filter_ctx,
-                               &wim->lzx_context,
                                progress_func);
        if (ret)
                goto out_truncate;
@@ -2844,7 +3022,8 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
        if (ret)
                goto out_truncate;
 
-       goto out_unlock_wim;
+       wim->wim_locked = 0;
+       return 0;
 
 out_truncate:
        if (!(write_flags & WIMLIB_WRITE_FLAG_NO_LOOKUP_TABLE)) {
@@ -2856,12 +3035,12 @@ out_truncate:
        }
 out_restore_physical_hdr:
        (void)write_wim_header_flags(hdr_save.flags, &wim->out_fd);
-out_restore_memory_hdr:
-       memcpy(&wim->hdr, &hdr_save, sizeof(struct wim_header));
-out_close_wim:
-       (void)close_wim_writable(wim, write_flags);
 out_unlock_wim:
        wim->wim_locked = 0;
+out_close_wim:
+       (void)close_wim_writable(wim, write_flags);
+out_restore_memory_hdr:
+       memcpy(&wim->hdr, &hdr_save, sizeof(struct wim_header));
        return ret;
 }
 
@@ -2919,27 +3098,39 @@ overwrite_wim_via_tmpfile(WIMStruct *wim, int write_flags,
        return 0;
 }
 
+/* Determine if the specified WIM file may be updated by appending in-place
+ * rather than writing and replacing it with an entirely new file.  */
 static bool
 can_overwrite_wim_inplace(const WIMStruct *wim, int write_flags)
 {
+       /* REBUILD flag forces full rebuild.  */
        if (write_flags & WIMLIB_WRITE_FLAG_REBUILD)
                return false;
 
+       /* Deletions cause full rebuild by default.  */
        if (wim->deletion_occurred && !(write_flags & WIMLIB_WRITE_FLAG_SOFT_DELETE))
                return false;
 
+       /* Pipable WIMs cannot be updated in place, nor can a non-pipable WIM be
+        * turned into a pipable WIM in-place.  */
        if (wim_is_pipable(wim) || (write_flags & WIMLIB_WRITE_FLAG_PIPABLE))
                return false;
 
-       if (wim->hdr.wim_version != WIM_VERSION_PACKED_STREAMS) {
-               if (wim->compression_type != wim->out_compression_type)
-                       return false;
-               if (wim->chunk_size != wim->out_chunk_size)
-                       return false;
-       } else {
-               if (write_flags & WIMLIB_WRITE_FLAG_NO_PACK_STREAMS)
-                       return false;
-       }
+       /* wimlib allows multiple packs in a single WIM, but they don't seem to
+        * be compatible with WIMGAPI, so force all streams to be repacked if
+        * the WIM already may have contained a pack and PACK_STREAMS was
+        * requested.  */
+       if (write_flags & WIMLIB_WRITE_FLAG_PACK_STREAMS &&
+           wim->hdr.wim_version == WIM_VERSION_PACKED_STREAMS)
+               return false;
+
+       /* The default compression type and compression chunk size selected for
+        * the output WIM must be the same as those currently used for the WIM.
+        */
+       if (wim->compression_type != wim->out_compression_type)
+               return false;
+       if (wim->chunk_size != wim->out_chunk_size)
+               return false;
 
        return true;
 }