]> wimlib.net Git - wimlib/blobdiff - src/resource.c
Make different threads use different FILE*'s
[wimlib] / src / resource.c
index f7a7916e5f0cc0ed94bcae2b30673b500f80db4b..1871cfcccb8617ba005124652507c555f933f480 100644 (file)
@@ -27,6 +27,8 @@
 #include <stdlib.h>
 #include <stdarg.h>
 
+#include "dentry.h"
+
 #ifdef WITH_NTFS_3G
 #include <ntfs-3g/attrib.h>
 #include <ntfs-3g/inode.h>
@@ -39,7 +41,6 @@
 #include "lzx.h"
 #include "xpress.h"
 #include "sha1.h"
-#include "dentry.h"
 #include <unistd.h>
 #include <errno.h>
 #ifdef HAVE_ALLOCA_H
 #endif
 
 
-/* 
+/*
  * Reads all or part of a compressed resource into an in-memory buffer.
  *
  * @fp:                The FILE* for the WIM file.
- * @resource_compressed_size:           The compressed size of the resource.  
+ * @resource_compressed_size:           The compressed size of the resource.
  * @resource_uncompressed_size:  The uncompressed size of the resource.
  * @resource_offset:            The offset of the start of the resource from
  *                                     the start of the stream @fp.
- * @resource_ctype:    The compression type of the resource. 
+ * @resource_ctype:    The compression type of the resource.
  * @len:               The number of bytes of uncompressed data to read from
  *                             the resource.
  * @offset:            The offset of the bytes to read within the uncompressed
@@ -65,9 +66,9 @@
  *
  * Returns zero on success, nonzero on failure.
  */
-static int read_compressed_resource(FILE *fp, u64 resource_compressed_size, 
-                                   u64 resource_uncompressed_size, 
-                                   u64 resource_offset, int resource_ctype, 
+static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
+                                   u64 resource_uncompressed_size,
+                                   u64 resource_offset, int resource_ctype,
                                    u64 len, u64 offset, u8  contents_ret[])
 {
 
@@ -98,7 +99,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
         * The chunk offsets are measured relative to the end of the chunk
         * table.  The first chunk is omitted from the table in the WIM file
         * because its offset is implicitly given by the fact that it directly
-        * follows the chunk table and therefore must have an offset of 0. 
+        * follows the chunk table and therefore must have an offset of 0.
         */
 
        /* Calculate how many chunks the resource conists of in its entirety. */
@@ -146,7 +147,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        /* According to M$'s documentation, if the uncompressed size of
         * the file is greater than 4 GB, the chunk entries are 8-byte
         * integers.  Otherwise, they are 4-byte integers. */
-       u64 chunk_entry_size = (resource_uncompressed_size >= (u64)1 << 32) ? 
+       u64 chunk_entry_size = (resource_uncompressed_size >= (u64)1 << 32) ?
                                                                        8 : 4;
 
        /* Size of the full chunk table in the WIM file. */
@@ -160,11 +161,11 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
        /* Number of entries we need to actually read from the chunk
         * table (excludes the implicit first chunk). */
-       u64 num_needed_chunk_entries = (start_chunk == 0) ? 
+       u64 num_needed_chunk_entries = (start_chunk == 0) ?
                                num_needed_chunks - 1 : num_needed_chunks;
 
        /* Skip over unneeded chunk table entries. */
-       u64 file_offset_of_needed_chunk_entries = resource_offset + 
+       u64 file_offset_of_needed_chunk_entries = resource_offset +
                                start_table_idx * chunk_entry_size;
        if (fseeko(fp, file_offset_of_needed_chunk_entries, SEEK_SET) != 0) {
                ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" to read "
@@ -191,17 +192,17 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        if (chunk_entry_size == 4) {
                u32 *entries = (u32*)chunk_tab_buf;
                while (num_needed_chunk_entries--)
-                       *chunk_tab_p++ = to_le32(*entries++);
+                       *chunk_tab_p++ = le32_to_cpu(*entries++);
        } else {
                u64 *entries = (u64*)chunk_tab_buf;
                while (num_needed_chunk_entries--)
-                       *chunk_tab_p++ = to_le64(*entries++);
+                       *chunk_tab_p++ = le64_to_cpu(*entries++);
        }
 
        /* Done with the chunk table now.  We must now seek to the first chunk
         * that is needed for the read. */
 
-       u64 file_offset_of_first_needed_chunk = resource_offset + 
+       u64 file_offset_of_first_needed_chunk = resource_offset +
                                chunk_table_size + chunk_offsets[0];
        if (fseeko(fp, file_offset_of_first_needed_chunk, SEEK_SET) != 0) {
                ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" to read "
@@ -237,7 +238,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                         * expand to WIM_CHUNK_SIZE uncompressed, and the amount
                         * of compressed data for the chunk is given by the
                         * difference of offsets in the chunk offset table. */
-                       compressed_chunk_size = chunk_offsets[i + 1 - start_chunk] - 
+                       compressed_chunk_size = chunk_offsets[i + 1 - start_chunk] -
                                                chunk_offsets[i - start_chunk];
                        uncompressed_chunk_size = WIM_CHUNK_SIZE;
                } else {
@@ -245,15 +246,15 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                         * bytes in the file resource, and the last uncompressed
                         * chunk has size equal to however many bytes are left-
                         * that is, the remainder of the uncompressed size when
-                        * divided by WIM_CHUNK_SIZE. 
+                        * divided by WIM_CHUNK_SIZE.
                         *
                         * Note that the resource_compressed_size includes the
                         * chunk table, so the size of it must be subtracted. */
-                       compressed_chunk_size = resource_compressed_size - 
+                       compressed_chunk_size = resource_compressed_size -
                                                chunk_table_size -
                                                chunk_offsets[i - start_chunk];
 
-                       uncompressed_chunk_size = resource_uncompressed_size % 
+                       uncompressed_chunk_size = resource_uncompressed_size %
                                                                WIM_CHUNK_SIZE;
 
                        /* If the remainder is 0, the last chunk actually
@@ -280,7 +281,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                        end_offset = WIM_CHUNK_SIZE - 1;
 
                u64 partial_chunk_size = end_offset + 1 - start_offset;
-               bool is_partial_chunk = (partial_chunk_size != 
+               bool is_partial_chunk = (partial_chunk_size !=
                                                uncompressed_chunk_size);
 
                DEBUG2("start_offset = %u, end_offset = %u", start_offset,
@@ -300,7 +301,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                                        return WIMLIB_ERR_READ;
                                }
                        }
-                       if (fread(out_p, 1, partial_chunk_size, fp) != 
+                       if (fread(out_p, 1, partial_chunk_size, fp) !=
                                        partial_chunk_size)
                                goto err;
                } else {
@@ -308,7 +309,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
                        int ret;
 
                        /* Read the compressed data into compressed_buf. */
-                       if (fread(compressed_buf, 1, compressed_chunk_size, 
+                       if (fread(compressed_buf, 1, compressed_chunk_size,
                                                fp) != compressed_chunk_size)
                                goto err;
 
@@ -319,7 +320,7 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
                                ret = decompress(compressed_buf,
                                                compressed_chunk_size,
-                                               uncompressed_buf, 
+                                               uncompressed_buf,
                                                uncompressed_chunk_size);
                                if (ret != 0)
                                        return WIMLIB_ERR_DECOMPRESSION;
@@ -350,7 +351,7 @@ err:
        return WIMLIB_ERR_READ;
 }
 
-/* 
+/*
  * Reads uncompressed data from an open file stream.
  */
 int read_uncompressed_resource(FILE *fp, u64 offset, u64 len,
@@ -390,8 +391,21 @@ const u8 *get_resource_entry(const u8 *p, struct resource_entry *entry)
        p = get_u8(p, &flags);
        entry->size = size;
        entry->flags = flags;
+
+       /* offset and original_size are truncated to 62 bits to avoid possible
+        * overflows, when converting to a signed 64-bit integer (off_t) or when
+        * adding size or original_size.  This is okay since no one would ever
+        * actually have a WIM bigger than 4611686018427387903 bytes... */
        p = get_u64(p, &entry->offset);
+       if (entry->offset & 0xc000000000000000ULL) {
+               WARNING("Truncating offset in resource entry");
+               entry->offset &= 0x3fffffffffffffffULL;
+       }
        p = get_u64(p, &entry->original_size);
+       if (entry->original_size & 0xc000000000000000ULL) {
+               WARNING("Truncating original_size in resource entry");
+               entry->original_size &= 0x3fffffffffffffffULL;
+       }
        return p;
 }
 
@@ -407,6 +421,57 @@ u8 *put_resource_entry(u8 *p, const struct resource_entry *entry)
        return p;
 }
 
+static FILE *wim_get_fp(WIMStruct *w)
+{
+       pthread_mutex_lock(&w->fp_tab_mutex);
+       FILE *fp;
+
+       wimlib_assert(w->filename != NULL);
+
+       for (size_t i = 0; i < w->num_allocated_fps; i++) {
+               if (w->fp_tab[i]) {
+                       fp = w->fp_tab[i];
+                       w->fp_tab[i] = NULL;
+                       goto out;
+               }
+       }
+       DEBUG("Opening extra file descriptor to `%s'", w->filename);
+       fp = fopen(w->filename, "rb");
+       if (!fp)
+               ERROR_WITH_ERRNO("Failed to open `%s'", w->filename);
+out:
+       pthread_mutex_unlock(&w->fp_tab_mutex);
+       return fp;
+}
+
+static int wim_release_fp(WIMStruct *w, FILE *fp)
+{
+       int ret = 0;
+       FILE **fp_tab;
+
+       pthread_mutex_lock(&w->fp_tab_mutex);
+
+       for (size_t i = 0; i < w->num_allocated_fps; i++) {
+               if (w->fp_tab[i] == NULL) {
+                       w->fp_tab[i] = fp;
+                       goto out;
+               }
+       }
+
+       fp_tab = REALLOC(w->fp_tab, sizeof(FILE*) * (w->num_allocated_fps + 4));
+       if (!fp_tab) {
+               ret = WIMLIB_ERR_NOMEM;
+               goto out;
+       }
+       w->fp_tab = fp_tab;
+       memset(&w->fp_tab[w->num_allocated_fps], 0, 4 * sizeof(FILE*));
+       w->fp_tab[w->num_allocated_fps] = fp;
+       w->num_allocated_fps += 4;
+out:
+       pthread_mutex_unlock(&w->fp_tab_mutex);
+       return ret;
+}
+
 /*
  * Reads some data from the resource corresponding to a WIM lookup table entry.
  *
@@ -414,47 +479,61 @@ u8 *put_resource_entry(u8 *p, const struct resource_entry *entry)
  * @buf:       Buffer into which to write the data.
  * @size:      Number of bytes to read.
  * @offset:    Offset at which to start reading the resource.
- * @raw:       If %true, compressed data is read literally rather than being
- *                     decompressed first.
  *
  * Returns zero on success, nonzero on failure.
  */
 int read_wim_resource(const struct lookup_table_entry *lte, u8 buf[],
-                     size_t size, u64 offset, bool raw)
+                     size_t size, u64 offset, int flags)
 {
+       int ctype;
+       int ret = 0;
+       FILE *fp;
+
        /* We shouldn't be allowing read over-runs in any part of the library.
         * */
-       if (raw)
+       if (flags & WIMLIB_RESOURCE_FLAG_RAW)
                wimlib_assert(offset + size <= lte->resource_entry.size);
        else
                wimlib_assert(offset + size <= lte->resource_entry.original_size);
 
-       int ctype;
-       int ret;
-       FILE *fp;
        switch (lte->resource_location) {
        case RESOURCE_IN_WIM:
                /* The resource is in a WIM file, and its WIMStruct is given by
                 * the lte->wim member.  The resource may be either compressed
                 * or uncompressed. */
-               wimlib_assert(lte->wim);
-               wimlib_assert(lte->wim->fp);
+               wimlib_assert(lte->wim != NULL);
+
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       fp = wim_get_fp(lte->wim);
+                       if (!fp)
+                               return WIMLIB_ERR_OPEN;
+               } else {
+                       wimlib_assert(lte->wim->fp != NULL);
+                       fp = lte->wim->fp;
+               }
+
                ctype = wim_resource_compression_type(lte);
 
                wimlib_assert(ctype != WIM_COMPRESSION_TYPE_NONE ||
                              (lte->resource_entry.original_size ==
                               lte->resource_entry.size));
 
-               if (raw || ctype == WIM_COMPRESSION_TYPE_NONE)
-                       return read_uncompressed_resource(lte->wim->fp,
-                                                         lte->resource_entry.offset + offset,
-                                                         size, buf);
+               if ((flags & WIMLIB_RESOURCE_FLAG_RAW)
+                   || ctype == WIM_COMPRESSION_TYPE_NONE)
+                       ret = read_uncompressed_resource(fp,
+                                                        lte->resource_entry.offset + offset,
+                                                        size, buf);
                else
-                       return read_compressed_resource(lte->wim->fp,
-                                                       lte->resource_entry.size,
-                                                       lte->resource_entry.original_size,
-                                                       lte->resource_entry.offset,
-                                                       ctype, size, offset, buf);
+                       ret = read_compressed_resource(fp,
+                                                      lte->resource_entry.size,
+                                                      lte->resource_entry.original_size,
+                                                      lte->resource_entry.offset,
+                                                      ctype, size, offset, buf);
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       int ret2 = wim_release_fp(lte->wim, fp);
+                       if (ret == 0)
+                               ret = ret2;
+               }
                break;
        case RESOURCE_IN_STAGING_FILE:
        case RESOURCE_IN_FILE_ON_DISK:
@@ -471,49 +550,45 @@ int read_wim_resource(const struct lookup_table_entry *lte, u8 buf[],
                        if (!fp) {
                                ERROR_WITH_ERRNO("Failed to open the file "
                                                 "`%s'", lte->file_on_disk);
-                               return WIMLIB_ERR_OPEN;
+                               ret = WIMLIB_ERR_OPEN;
+                               break;
                        }
                }
                ret = read_uncompressed_resource(fp, offset, size, buf);
                if (fp != lte->file_on_disk_fp)
                        fclose(fp);
-               return ret;
                break;
        case RESOURCE_IN_ATTACHED_BUFFER:
                /* The resource is directly attached uncompressed in an
                 * in-memory buffer. */
-               wimlib_assert(lte->attached_buffer);
+               wimlib_assert(lte->attached_buffer != NULL);
                memcpy(buf, lte->attached_buffer + offset, size);
-               return 0;
                break;
 #ifdef WITH_NTFS_3G
        case RESOURCE_IN_NTFS_VOLUME:
-               wimlib_assert(lte->ntfs_loc);
-               if (lte->attr) {
-                       u64 adjusted_offset;
+               wimlib_assert(lte->ntfs_loc != NULL);
+               wimlib_assert(lte->attr != NULL);
+               {
                        if (lte->ntfs_loc->is_reparse_point)
-                               adjusted_offset = offset + 8;
-                       else
-                               adjusted_offset = offset;
-                       if (ntfs_attr_pread(lte->attr, offset, size, buf) == size) {
-                               return 0;
-                       } else {
+                               offset += 8;
+                       if (ntfs_attr_pread(lte->attr, offset, size, buf) != size) {
                                ERROR_WITH_ERRNO("Error reading NTFS attribute "
                                                 "at `%s'",
                                                 lte->ntfs_loc->path_utf8);
-                               return WIMLIB_ERR_NTFS_3G;
+                               ret = WIMLIB_ERR_NTFS_3G;
                        }
-               } else {
-                       wimlib_assert(0);
+                       break;
                }
-               break;
 #endif
        default:
-               assert(0);
+               wimlib_assert(0);
+               ret = -1;
+               break;
        }
+       return ret;
 }
 
-/* 
+/*
  * Reads all the data from the resource corresponding to a WIM lookup table
  * entry.
  *
@@ -523,9 +598,10 @@ int read_wim_resource(const struct lookup_table_entry *lte, u8 buf[],
  *
  * Returns 0 on success; nonzero on failure.
  */
-int read_full_wim_resource(const struct lookup_table_entry *lte, u8 buf[])
+int read_full_wim_resource(const struct lookup_table_entry *lte, u8 buf[],
+                          int flags)
 {
-       return read_wim_resource(lte, buf, wim_resource_size(lte), 0, false);
+       return read_wim_resource(lte, buf, wim_resource_size(lte), 0, flags);
 }
 
 /* Chunk table that's located at the beginning of each compressed resource in
@@ -542,7 +618,7 @@ struct chunk_table {
        u64 offsets[0];
 };
 
-/* 
+/*
  * Allocates and initializes a chunk table, and reserves space for it in the
  * output file.
  */
@@ -554,11 +630,9 @@ begin_wim_resource_chunk_tab(const struct lookup_table_entry *lte,
 {
        u64 size = wim_resource_size(lte);
        u64 num_chunks = (size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
-       struct chunk_table *chunk_tab = MALLOC(sizeof(struct chunk_table) +
-                                              num_chunks * sizeof(u64));
-       int ret = 0;
-
-       wimlib_assert(size != 0);
+       size_t alloc_size = sizeof(struct chunk_table) + num_chunks * sizeof(u64);
+       struct chunk_table *chunk_tab = CALLOC(1, alloc_size);
+       int ret;
 
        if (!chunk_tab) {
                ERROR("Failed to allocate chunk table for %"PRIu64" byte "
@@ -583,12 +657,13 @@ begin_wim_resource_chunk_tab(const struct lookup_table_entry *lte,
                goto out;
        }
 
-       *chunk_tab_ret = chunk_tab;
+       ret = 0;
 out:
+       *chunk_tab_ret = chunk_tab;
        return ret;
 }
 
-/* 
+/*
  * Compresses a chunk of a WIM resource.
  *
  * @chunk:             Uncompressed data of the chunk.
@@ -632,7 +707,7 @@ static int compress_chunk(const u8 chunk[], unsigned chunk_size,
  * @chunk:       Uncompressed data of the chunk.
  * @chunk_size:          Size of the chunk (<= WIM_CHUNK_SIZE)
  * @out_fp:      FILE * to write tho chunk to.
- * @out_ctype:   Compression type to use when writing the chunk (ignored if no 
+ * @out_ctype:   Compression type to use when writing the chunk (ignored if no
  *                     chunk table provided)
  * @chunk_tab:   Pointer to chunk table being created.  It is updated with the
  *                     offset of the chunk we write.
@@ -666,7 +741,7 @@ static int write_wim_resource_chunk(const u8 chunk[], unsigned chunk_size,
                *chunk_tab->cur_offset_p++ = chunk_tab->cur_offset;
                chunk_tab->cur_offset += out_chunk_size;
        }
-       
+
        if (fwrite(out_chunk, 1, out_chunk_size, out_fp) != out_chunk_size) {
                ERROR_WITH_ERRNO("Failed to write WIM resource chunk");
                return WIMLIB_ERR_WRITE;
@@ -674,7 +749,7 @@ static int write_wim_resource_chunk(const u8 chunk[], unsigned chunk_size,
        return 0;
 }
 
-/* 
+/*
  * Finishes a WIM chunk tale and writes it to the output file at the correct
  * offset.
  *
@@ -693,11 +768,11 @@ finish_wim_resource_chunk_tab(struct chunk_table *chunk_tab,
        }
 
        if (chunk_tab->bytes_per_chunk_entry == 8) {
-               array_to_le64(chunk_tab->offsets, chunk_tab->num_chunks);
+               array_cpu_to_le64(chunk_tab->offsets, chunk_tab->num_chunks);
        } else {
                for (u64 i = 0; i < chunk_tab->num_chunks; i++)
                        ((u32*)chunk_tab->offsets)[i] =
-                               to_le32(chunk_tab->offsets[i]);
+                               cpu_to_le32(chunk_tab->offsets[i]);
        }
        bytes_written = fwrite((u8*)chunk_tab->offsets +
                                        chunk_tab->bytes_per_chunk_entry,
@@ -730,7 +805,7 @@ finish_wim_resource_chunk_tab(struct chunk_table *chunk_tab,
  *                     the same as the compression type of the WIM resource we
  *                     need to read, we simply copy the data (i.e. we do not
  *                     uncompress it, then compress it again).
- * @out_res_entry:  If non-NULL, a resource entry that is filled in with the 
+ * @out_res_entry:  If non-NULL, a resource entry that is filled in with the
  *                 offset, original size, compressed size, and compression flag
  *                 of the output resource.
  *
@@ -738,14 +813,15 @@ finish_wim_resource_chunk_tab(struct chunk_table *chunk_tab,
  */
 static int write_wim_resource(struct lookup_table_entry *lte,
                              FILE *out_fp, int out_ctype,
-                             struct resource_entry *out_res_entry)
+                             struct resource_entry *out_res_entry,
+                             int flags)
 {
        u64 bytes_remaining;
        u64 original_size;
        u64 old_compressed_size;
        u64 new_compressed_size;
-       u64 offset = 0;
-       int ret = 0;
+       u64 offset;
+       int ret;
        struct chunk_table *chunk_tab = NULL;
        bool raw;
        off_t file_offset;
@@ -768,15 +844,19 @@ static int write_wim_resource(struct lookup_table_entry *lte,
                                 "stream");
                return WIMLIB_ERR_WRITE;
        }
-       
+
        /* Are the compression types the same?  If so, do a raw copy (copy
         * without decompressing and recompressing the data). */
        raw = (wim_resource_compression_type(lte) == out_ctype
               && out_ctype != WIM_COMPRESSION_TYPE_NONE);
-       if (raw)
+
+       if (raw) {
+               flags |= WIMLIB_RESOURCE_FLAG_RAW;
                bytes_remaining = old_compressed_size;
-       else
+       } else {
+               flags &= ~WIMLIB_RESOURCE_FLAG_RAW;
                bytes_remaining = original_size;
+       }
 
        /* Empty resource; nothing needs to be done, so just return success. */
        if (bytes_remaining == 0)
@@ -846,9 +926,10 @@ static int write_wim_resource(struct lookup_table_entry *lte,
        /* While there are still bytes remaining in the WIM resource, read a
         * chunk of the resource, update SHA1, then write that chunk using the
         * desired compression type. */
+       offset = 0;
        do {
                u64 to_read = min(bytes_remaining, WIM_CHUNK_SIZE);
-               ret = read_wim_resource(lte, buf, to_read, offset, raw);
+               ret = read_wim_resource(lte, buf, to_read, offset, flags);
                if (ret != 0)
                        goto out_fclose;
                if (!raw)
@@ -863,7 +944,7 @@ static int write_wim_resource(struct lookup_table_entry *lte,
 
        /* Raw copy:  The new compressed size is the same as the old compressed
         * size
-        * 
+        *
         * Using WIM_COMPRESSION_TYPE_NONE:  The new compressed size is the
         * original size
         *
@@ -917,7 +998,7 @@ static int write_wim_resource(struct lookup_table_entry *lte,
                        goto out_fclose;
                }
                ret = write_wim_resource(lte, out_fp, WIM_COMPRESSION_TYPE_NONE,
-                                        out_res_entry);
+                                        out_res_entry, flags);
                if (ret != 0)
                        goto out_fclose;
                if (fflush(out_fp) != 0) {
@@ -928,22 +1009,23 @@ static int write_wim_resource(struct lookup_table_entry *lte,
                if (ftruncate(fileno(out_fp), file_offset + out_res_entry->size) != 0) {
                        ERROR_WITH_ERRNO("Failed to truncate output WIM file");
                        ret = WIMLIB_ERR_WRITE;
+                       goto out_fclose;
+               }
+       } else {
+               if (out_res_entry) {
+                       out_res_entry->size          = new_compressed_size;
+                       out_res_entry->original_size = original_size;
+                       out_res_entry->offset        = file_offset;
+                       out_res_entry->flags         = lte->resource_entry.flags
+                                                       & ~WIM_RESHDR_FLAG_COMPRESSED;
+                       if (out_ctype != WIM_COMPRESSION_TYPE_NONE)
+                               out_res_entry->flags |= WIM_RESHDR_FLAG_COMPRESSED;
                }
-               goto out_fclose;
-       }
-       wimlib_assert(new_compressed_size <= original_size || raw);
-       if (out_res_entry) {
-               out_res_entry->size          = new_compressed_size;
-               out_res_entry->original_size = original_size;
-               out_res_entry->offset        = file_offset;
-               out_res_entry->flags         = lte->resource_entry.flags
-                                               & ~WIM_RESHDR_FLAG_COMPRESSED;
-               if (out_ctype != WIM_COMPRESSION_TYPE_NONE)
-                       out_res_entry->flags |= WIM_RESHDR_FLAG_COMPRESSED;
        }
+       ret = 0;
 out_fclose:
        if (lte->resource_location == RESOURCE_IN_FILE_ON_DISK
-            && lte->file_on_disk_fp) {
+           && lte->file_on_disk_fp) {
                fclose(lte->file_on_disk_fp);
                lte->file_on_disk_fp = NULL;
        }
@@ -952,9 +1034,9 @@ out_fclose:
                if (lte->attr) {
                        ntfs_attr_close(lte->attr);
                        lte->attr = NULL;
-               } if (ni) {
-                       ntfs_inode_close(ni);
                }
+               if (ni)
+                       ntfs_inode_close(ni);
        }
 #endif
 out:
@@ -970,7 +1052,7 @@ static int write_wim_resource_from_buffer(const u8 *buf, u64 buf_size,
                                          struct resource_entry *out_res_entry,
                                          u8 hash[SHA1_HASH_SIZE])
 {
-       /* Set up a temporary lookup table entry that we provide to
+       /* Set up a temporary lookup table entry to provide to
         * write_wim_resource(). */
        struct lookup_table_entry lte;
        int ret;
@@ -982,17 +1064,17 @@ static int write_wim_resource_from_buffer(const u8 *buf, u64 buf_size,
        lte.attached_buffer              = (u8*)buf;
 
        zero_out_hash(lte.hash);
-       ret = write_wim_resource(&lte, out_fp, out_ctype, out_res_entry);
+       ret = write_wim_resource(&lte, out_fp, out_ctype, out_res_entry, 0);
        if (ret != 0)
                return ret;
        copy_hash(hash, lte.hash);
        return 0;
 }
 
-/* 
+/*
  * Extracts the first @size bytes of the WIM resource specified by @lte to the
  * open file descriptor @fd.
- * 
+ *
  * Returns 0 on success; nonzero on failure.
  */
 int extract_wim_resource_to_fd(const struct lookup_table_entry *lte, int fd,
@@ -1009,7 +1091,7 @@ int extract_wim_resource_to_fd(const struct lookup_table_entry *lte, int fd,
 
        while (bytes_remaining) {
                u64 to_read = min(bytes_remaining, WIM_CHUNK_SIZE);
-               ret = read_wim_resource(lte, buf, to_read, offset, false);
+               ret = read_wim_resource(lte, buf, to_read, offset, 0);
                if (ret != 0)
                        break;
                sha1_update(&ctx, buf, to_read);
@@ -1031,9 +1113,9 @@ int extract_wim_resource_to_fd(const struct lookup_table_entry *lte, int fd,
        return 0;
 }
 
-/* 
+/*
  * Extracts the WIM resource specified by @lte to the open file descriptor @fd.
- * 
+ *
  * Returns 0 on success; nonzero on failure.
  */
 int extract_full_wim_resource_to_fd(const struct lookup_table_entry *lte, int fd)
@@ -1041,7 +1123,7 @@ int extract_full_wim_resource_to_fd(const struct lookup_table_entry *lte, int fd
        return extract_wim_resource_to_fd(lte, fd, wim_resource_size(lte));
 }
 
-/* 
+/*
  * Copies the file resource specified by the lookup table entry @lte from the
  * input WIM to the output WIM that has its FILE * given by
  * ((WIMStruct*)wim)->out_fp.
@@ -1062,8 +1144,8 @@ int copy_resource(struct lookup_table_entry *lte, void *wim)
                return 0;
 
        ret = write_wim_resource(lte, w->out_fp,
-                                wim_resource_compression_type(lte), 
-                                &lte->output_resource_entry);
+                                wim_resource_compression_type(lte),
+                                &lte->output_resource_entry, 0);
        if (ret != 0)
                return ret;
        lte->out_refcnt = lte->refcnt;
@@ -1071,14 +1153,14 @@ int copy_resource(struct lookup_table_entry *lte, void *wim)
        return 0;
 }
 
-/* 
+/*
  * Writes a dentry's resources, including the main file resource as well as all
- * alternate data streams, to the output file. 
+ * alternate data streams, to the output file.
  *
  * @dentry:  The dentry for the file.
  * @wim_p:   A pointer to the WIMStruct containing @dentry.
  *
- * @return zero on success, nonzero on failure. 
+ * @return zero on success, nonzero on failure.
  */
 int write_dentry_resources(struct dentry *dentry, void *wim_p)
 {
@@ -1096,7 +1178,7 @@ int write_dentry_resources(struct dentry *dentry, void *wim_p)
                lte = inode_stream_lte(dentry->d_inode, i, w->lookup_table);
                if (lte && ++lte->out_refcnt == 1) {
                        ret = write_wim_resource(lte, w->out_fp, ctype,
-                                                &lte->output_resource_entry);
+                                                &lte->output_resource_entry, 0);
                        if (ret != 0)
                                break;
                }
@@ -1104,7 +1186,7 @@ int write_dentry_resources(struct dentry *dentry, void *wim_p)
        return ret;
 }
 
-/* 
+/*
  * Reads the metadata metadata resource from the WIM file.  The metadata
  * resource consists of the security data, followed by the directory entry for
  * the root directory, followed by all the other directory entries in the
@@ -1151,6 +1233,12 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
                return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
        }
 
+       if (sizeof(size_t) < 8 && metadata_len > 0xffffffff) {
+               ERROR("Metadata resource is too large (%"PRIu64" bytes",
+                     metadata_len);
+               return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
+       }
+
        /* Allocate memory for the uncompressed metadata resource. */
        buf = MALLOC(metadata_len);
 
@@ -1161,7 +1249,7 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
        }
 
        /* Read the metadata resource into memory.  (It may be compressed.) */
-       ret = read_full_wim_resource(metadata_lte, buf);
+       ret = read_full_wim_resource(metadata_lte, buf, 0);
        if (ret != 0)
                goto out_free_buf;
 
@@ -1178,14 +1266,18 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
         * and if successful, go ahead and calculate the offset in the metadata
         * resource of the root dentry. */
 
+       wimlib_assert(imd->security_data == NULL);
        ret = read_security_data(buf, metadata_len, &imd->security_data);
        if (ret != 0)
                goto out_free_buf;
 
-       get_u32(buf, &dentry_offset);
-       if (dentry_offset == 0)
-               dentry_offset = 8;
-       dentry_offset = (dentry_offset + 7) & ~7;
+       dentry_offset = (imd->security_data->total_length + 7) & ~7;
+
+       if (dentry_offset == 0) {
+               ERROR("Integer overflow while reading metadata resource");
+               ret = WIMLIB_ERR_INVALID_SECURITY_DATA;
+               goto out_free_security_data;
+       }
 
        /* Allocate memory for the root dentry and read it into memory */
        dentry = MALLOC(sizeof(struct dentry));
@@ -1195,13 +1287,12 @@ int read_metadata_resource(WIMStruct *w, struct image_metadata *imd)
                ret = WIMLIB_ERR_NOMEM;
                goto out_free_security_data;
        }
-               
+
        ret = read_dentry(buf, metadata_len, dentry_offset, dentry);
 
-       /* This is the root dentry, so set its pointers correctly. */
+       /* This is the root dentry, so set its parent to itself. */
        dentry->parent = dentry;
-       dentry->next   = dentry;
-       dentry->prev   = dentry;
+
        if (ret != 0)
                goto out_free_dentry_tree;
        inode_add_dentry(dentry, dentry->d_inode);
@@ -1264,7 +1355,6 @@ int write_metadata_resource(WIMStruct *w)
        struct lookup_table_entry *lte;
        u64 metadata_original_size;
        const struct wim_security_data *sd;
-       const unsigned random_tail_len = 20;
 
        DEBUG("Writing metadata resource for image %d", w->current_image);
 
@@ -1273,7 +1363,8 @@ int write_metadata_resource(WIMStruct *w)
 
        /* We do not allow the security data pointer to be NULL, although it may
         * point to an empty security data with no entries. */
-       wimlib_assert(sd);
+       wimlib_assert(root != NULL);
+       wimlib_assert(sd != NULL);
 
        /* Offset of first child of the root dentry.  It's equal to:
         * - The total length of the security data, rounded to the next 8-byte
@@ -1289,7 +1380,7 @@ int write_metadata_resource(WIMStruct *w)
        calculate_subdir_offsets(root, &subdir_offset);
 
        /* Total length of the metadata resource (uncompressed) */
-       metadata_original_size = subdir_offset + random_tail_len;
+       metadata_original_size = subdir_offset;
 
        /* Allocate a buffer to contain the uncompressed metadata resource */
        buf = MALLOC(metadata_original_size);
@@ -1303,26 +1394,18 @@ int write_metadata_resource(WIMStruct *w)
        p = write_security_data(sd, buf);
 
        /* Write the dentry tree into the resource buffer */
-       DEBUG("Writing dentry tree.");
        p = write_dentry_tree(root, p);
 
-       /* 
-        * Append 20 random bytes to the metadata resource so that we don't have
-        * identical metadata resources if we happen to append exactly the same
-        * image twice without any changes in timestamps.  If this were to
-        * happen, it would cause confusion about the number and order of images
-        * in the WIM.
-        */
-       randomize_byte_array(p, random_tail_len);
-
        /* We MUST have exactly filled the buffer; otherwise we calculated its
         * size incorrectly or wrote the data incorrectly. */
-       wimlib_assert(p - buf + random_tail_len == metadata_original_size);
+       wimlib_assert(p - buf == metadata_original_size);
 
        /* Get the lookup table entry for the metadata resource so we can update
         * it. */
        lte = wim_metadata_lookup_table_entry(w);
 
+       wimlib_assert(lte != NULL);
+
        /* Write the metadata resource to the output WIM using the proper
         * compression type.  The lookup table entry for the metadata resource
         * is updated. */
@@ -1336,14 +1419,17 @@ int write_metadata_resource(WIMStruct *w)
 
        /* It's very likely the SHA1 message digest of the metadata resource
         * changed, so re-insert the lookup table entry into the lookup table.
+        *
+        * We do not check for other lookup table entries having the same SHA1
+        * message digest.  It's possible for 2 absolutely identical images to
+        * be added, therefore causing 2 identical metadata resources to be in
+        * the WIM.  However, in this case, it's expected for 2 separate lookup
+        * table entries to be created, even though this doesn't make a whole
+        * lot of sense since they will share the same SHA1 message digest.
         * */
        lookup_table_unlink(w->lookup_table, lte);
        lookup_table_insert(w->lookup_table, lte);
 
-       /* We do not allow a metadata resource to be referenced multiple times,
-        * and the 20 random bytes appended to it should make it extremely
-        * likely for each metadata resource to be unique, even if the exact
-        * same image is captured. */
        wimlib_assert(lte->out_refcnt == 0);
        lte->out_refcnt = 1;