]> wimlib.net Git - wimlib/blobdiff - src/resource.c
read_compressed_resource(): Fix format strings
[wimlib] / src / resource.c
index 731bd1c0c3ebb258cbd8462b33ae1aaf5456ab79..8d61761414c9b718a1e4b0dab9312359616711ab 100644 (file)
@@ -1,50 +1,56 @@
 /*
  * resource.c
  *
- * Read uncompressed and compressed metadata and file resources.
+ * Read uncompressed and compressed metadata and file resources from a WIM file.
  */
 
 /*
- * Copyright (C) 2010 Carl Thijssen
- * Copyright (C) 2012 Eric Biggers
+ * Copyright (C) 2012, 2013 Eric Biggers
  *
  * This file is part of wimlib, a library for working with WIM files.
  *
  * wimlib is free software; you can redistribute it and/or modify it under the
- * terms of the GNU Lesser General Public License as published by the Free
- * Software Foundation; either version 2.1 of the License, or (at your option)
- * any later version.
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
  *
  * wimlib is distributed in the hope that it will be useful, but WITHOUT ANY
  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
- * A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
- * details.
+ * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
  *
- * You should have received a copy of the GNU Lesser General Public License
- * along with wimlib; if not, see http://www.gnu.org/licenses/.
+ * You should have received a copy of the GNU General Public License along with
+ * wimlib; if not, see http://www.gnu.org/licenses/.
  */
 
 #include "wimlib_internal.h"
+#include "dentry.h"
 #include "lookup_table.h"
-#include "io.h"
+#include "buffer_io.h"
 #include "lzx.h"
 #include "xpress.h"
 #include "sha1.h"
-#include "dentry.h"
-#include "config.h"
-#include <unistd.h>
+
 #include <errno.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <unistd.h>
 
+#ifdef WITH_NTFS_3G
+#include <time.h>
+#include <ntfs-3g/attrib.h>
+#include <ntfs-3g/inode.h>
+#include <ntfs-3g/dir.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
@@ -54,9 +60,9 @@
  *
  * 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[])
 {
 
@@ -71,9 +77,9 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
        if (len == 0)
                return 0;
 
-       int (*decompress)(const void *, uint, void *, uint);
+       int (*decompress)(const void *, unsigned, void *, unsigned);
        /* Set the appropriate decompress function. */
-       if (resource_ctype == WIM_COMPRESSION_TYPE_LZX)
+       if (resource_ctype == WIMLIB_COMPRESSION_TYPE_LZX)
                decompress = lzx_decompress;
        else
                decompress = xpress_decompress;
@@ -87,7 +93,7 @@ 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. */
@@ -135,7 +141,7 @@ 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. */
@@ -149,11 +155,11 @@ 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 "
@@ -180,17 +186,17 @@ 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 "
@@ -220,13 +226,14 @@ static int read_compressed_resource(FILE *fp, u64 resource_compressed_size,
 
                /* Calculate the sizes of the compressed chunk and of the
                 * uncompressed chunk. */
-               uint compressed_chunk_size, uncompressed_chunk_size;
+               unsigned compressed_chunk_size;
+               unsigned uncompressed_chunk_size;
                if (i != num_chunks - 1) {
                        /* All the chunks except the last one in the resource
                         * 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 {
@@ -234,15 +241,15 @@ 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
@@ -269,12 +276,12 @@ 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,
-                                       end_offset);
-               DEBUG2("partial_chunk_size = %u", partial_chunk_size);
+               DEBUG2("start_offset = %"PRIu64", end_offset = %"PRIu64"",
+                      start_offset, end_offset);
+               DEBUG2("partial_chunk_size = %"PRIu64"", partial_chunk_size);
 
                /* This is undocumented, but chunks can be uncompressed.  This
                 * appears to always be the case when the compressed chunk size
@@ -289,7 +296,7 @@ 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 {
@@ -297,7 +304,7 @@ 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;
 
@@ -308,7 +315,7 @@ 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;
@@ -339,11 +346,11 @@ err:
        return WIMLIB_ERR_READ;
 }
 
-/* 
+/*
  * Reads uncompressed data from an open file stream.
  */
-int read_uncompressed_resource(FILE *fp, u64 offset, u64 len, 
-                                       u8 contents_ret[])
+int read_uncompressed_resource(FILE *fp, u64 offset, u64 len,
+                              u8 contents_ret[])
 {
        if (fseeko(fp, offset, SEEK_SET) != 0) {
                ERROR("Failed to seek to byte %"PRIu64" of input file "
@@ -364,146 +371,6 @@ int read_uncompressed_resource(FILE *fp, u64 offset, u64 len,
        return 0;
 }
 
-
-/* 
- * Reads a WIM resource.
- *
- * @fp:                The FILE* for the WIM file.
- * @resource_size:             The compressed size of the resource.
- * @resource_original_size:    The uncompressed size of the resource.
- * @resource_offset:           The offset of the resource in the stream @fp.
- * @resource_ctype:            The compression type of the resource.
- *                             (WIM_COMPRESSION_TYPE_*)
- * @len:               How many bytes of the resource should be read.
- * @offset:            The offset within the resource at which the read
- *                             will occur.
- *
- *                     To read the whole file resource, specify offset =
- *                     0 and len = resource_original_size, or call
- *                     read_full_resource().
- *
- * @contents_ret:      An array, that must have length at least @len,
- *                             into which the uncompressed contents of
- *                             the file resource starting at @offset and 
- *                             continuing for @len bytes will be written.
- *
- * @return:            Zero on success, nonzero on failure. Failure may be due to
- *                     being unable to read the data from the WIM file at the
- *                     specified length and offset, or it may be due to the
- *                     compressed data (if the data is compressed) being
- *                     invalid.
- */
-int read_resource(FILE *fp, u64 resource_size, u64 resource_original_size,
-                 u64 resource_offset, int resource_ctype, u64 len, 
-                 u64 offset, void *contents_ret)
-{
-       if (resource_ctype == WIM_COMPRESSION_TYPE_NONE) {
-               if (resource_size != resource_original_size) {
-                       ERROR("Resource with original size %"PRIu64" bytes is "
-                             "marked as uncompressed, but its actual size is "
-                             "%"PRIu64" bytes", 
-                             resource_original_size, resource_size);
-                       return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
-               }
-               return read_uncompressed_resource(fp, 
-                               resource_offset + offset, 
-                               len, contents_ret);
-       } else {
-               return read_compressed_resource(fp, resource_size,
-                               resource_original_size, resource_offset,
-                               resource_ctype, len, offset, contents_ret);
-       }
-}
-
-
-/* 
- * Extracts the first @size bytes file resource specified by @entry to the open
- * file @fd.  Returns nonzero on error.
- *
- * XXX
- * This function is somewhat redundant with uncompress_resource(). The
- * main difference is that this function writes to a file descriptor using
- * low-level calls to write() rather than to a FILE* with fwrite(); also this
- * function allows only up to @size bytes to be extracted.
- */
-int extract_resource_to_fd(WIMStruct *w, const struct resource_entry *entry, 
-                          int fd, u64 size)
-{
-       u64 num_chunks;
-       u64 n;
-       u8 buf[min(size, WIM_CHUNK_SIZE)];
-       int res_ctype;
-       u64 offset;
-       u64 i;
-       int ret;
-
-       errno = 0;
-
-       num_chunks = (size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
-       n = WIM_CHUNK_SIZE;
-       res_ctype = wim_resource_compression_type(w, entry);
-       offset = 0;
-       for (i = 0; i < num_chunks; i++) {
-               if (i == num_chunks - 1) {
-                       n = size % WIM_CHUNK_SIZE;
-                       if (n == 0) {
-                               n = WIM_CHUNK_SIZE;
-                       }
-               }
-
-               ret = read_resource(w->fp, entry->size, entry->original_size,
-                                   entry->offset, res_ctype, n, offset, buf);
-               if (ret != 0)
-                       return ret;
-
-               if (full_write(fd, buf, n) != n)
-                       return WIMLIB_ERR_WRITE;
-               offset += n;
-       }
-       return ret;
-}
-
-/* 
- * Copies the file resource specified by the lookup table entry @lte from the
- * input WIM, pointed to by the fp field of the WIMStruct, to the output WIM,
- * pointed to by the out_fp field of the WIMStruct.
- *
- * The output_resource_entry, out_refcnt, and part_number fields of @lte are
- * updated.
- *
- * Metadata resources are not copied (they are handled elsewhere for joining and
- * splitting).
- */
-int copy_resource(struct lookup_table_entry *lte, void *w)
-{
-       if ((lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA) &&
-           !((WIMStruct*)w)->write_metadata) {
-               return 0;
-       }
-
-       FILE *in_fp = ((WIMStruct*)w)->fp;
-       FILE *out_fp = ((WIMStruct*)w)->out_fp;
-       int ret;
-       u64 size = lte->resource_entry.size;
-       u64 offset = lte->resource_entry.offset;
-       off_t new_offset = ftello(out_fp);
-
-       if (new_offset == -1)
-               return WIMLIB_ERR_WRITE;
-
-       ret = copy_between_files(in_fp, offset, out_fp, size);
-       if (ret != 0)
-               return ret;
-
-       memcpy(&lte->output_resource_entry, &lte->resource_entry, 
-                       sizeof(struct resource_entry));
-
-       lte->output_resource_entry.offset = new_offset;
-       lte->out_refcnt = lte->refcnt;
-       lte->part_number = ((WIMStruct*)w)->hdr.part_number;
-       return 0;
-}
-
 /* Reads the contents of a struct resource_entry, as represented in the on-disk
  * format, from the memory pointed to by @p, and fills in the fields of @entry.
  * A pointer to the byte after the memory read at @p is returned. */
@@ -516,8 +383,21 @@ 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;
 }
 
@@ -533,699 +413,313 @@ u8 *put_resource_entry(u8 *p, const struct resource_entry *entry)
        return p;
 }
 
-/* Given the compression type for the WIM file as a whole as the flags field of
- * a resource entry, returns the compression type for that resource entry. */
-int resource_compression_type(int wim_ctype, int reshdr_flags)
-{
-       if (wim_ctype != WIM_COMPRESSION_TYPE_NONE &&
-            (reshdr_flags & WIM_RESHDR_FLAG_COMPRESSED))
-               return wim_ctype;
-       else
-               return WIM_COMPRESSION_TYPE_NONE;
-}
-
-
-
-/*
- * Copies bytes between two file streams.
- *
- * Copies @len bytes from @in_fp to @out_fp, at the current position in @out_fp,
- * and at an offset of @in_offset in @in_fp.
- */
-int copy_between_files(FILE *in_fp, off_t in_offset, FILE *out_fp, size_t len)
+#ifdef WITH_FUSE
+static FILE *wim_get_fp(WIMStruct *w)
 {
-       u8 buf[BUFFER_SIZE];
-       size_t n;
+       pthread_mutex_lock(&w->fp_tab_mutex);
+       FILE *fp;
 
-       if (fseeko(in_fp, in_offset, SEEK_SET) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" of "
-                                "input file", in_offset);
-               return WIMLIB_ERR_READ;
-       }
-       /* To reduce memory usage and improve speed, read and write BUFFER_SIZE
-        * bytes at a time. */
-       while (len != 0) {
-               n = min(len, BUFFER_SIZE);
-               if (fread(buf, 1, n, in_fp) != n) {
-                       if (feof(in_fp)) {
-                               ERROR("Unexpected EOF when copying data "
-                                     "between files");
-                       } else {
-                               ERROR_WITH_ERRNO("Error copying data between "
-                                                "files");
-                       }
-                       return WIMLIB_ERR_READ;
-               }
+       wimlib_assert(w->filename != NULL);
 
-               if (fwrite(buf, 1, n, out_fp) != n) {
-                       ERROR_WITH_ERRNO("Error copying data between files");
-                       return WIMLIB_ERR_WRITE;
+       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;
                }
-               len -= n;
        }
-       return 0;
+       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;
 }
 
-
-/* 
- * Uncompresses a WIM file resource and writes it uncompressed to a file stream.
- *
- * @in_fp:          The file stream that contains the file resource.
- * @size:           The size of the resource in the input file.
- * @original_size:  The original (uncompressed) size of the resource. 
- * @offset:        The offset of the start of the resource in @in.
- * @input_ctype:    The compression type of the resource in @in.
- * @out_fp:        The file stream to write the file resource to.
- */
-static int uncompress_resource(FILE *in_fp, u64 size, u64 original_size,
-                              off_t offset, int input_ctype, FILE *out_fp)
+static int wim_release_fp(WIMStruct *w, FILE *fp)
 {
-       int ret;
-       u8 buf[WIM_CHUNK_SIZE];
-       /* Determine how many compressed chunks the file is divided into. */
-       u64 num_chunks;
-       u64 i;
-       u64 uncompressed_offset;
-       u64 uncompressed_chunk_size;
-       
-       num_chunks = (original_size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
-
-       for (i = 0; i < num_chunks; i++) {
-
-               uncompressed_offset = i * WIM_CHUNK_SIZE;
-               uncompressed_chunk_size = min(WIM_CHUNK_SIZE, original_size -
-                                             uncompressed_offset);
-
-               ret = read_resource(in_fp, size, original_size, offset,
-                                   input_ctype, uncompressed_chunk_size, 
-                                   uncompressed_offset, buf);
-               if (ret != 0)
-                       return ret;
+       int ret = 0;
+       FILE **fp_tab;
 
-               if (fwrite(buf, 1, uncompressed_chunk_size, out_fp) != 
-                     uncompressed_chunk_size) 
-               {
-                       ERROR_WITH_ERRNO("Failed to write file resource");
-                       return WIMLIB_ERR_WRITE;
+       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;
                }
        }
-       return 0;
+
+       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;
 }
+#endif
 
-/* 
- * Transfers a file resource between two files, writing it compressed.  The file
- * resource in the input file may be either compressed or uncompressed.
- * Alternatively, the input resource may be in-memory, but it must be
- * uncompressed.
+/*
+ * Reads some data from the resource corresponding to a WIM lookup table entry.
+ *
+ * @lte:       The WIM lookup table entry for the resource.
+ * @buf:       Buffer into which to write the data.
+ * @size:      Number of bytes to read.
+ * @offset:    Offset at which to start reading the resource.
  *
- * @in_fp:                 The file stream that contains the file resource.  Ignored
- *                     if uncompressed_resource != NULL.
- * @uncompressed_resource:     If this pointer is not NULL, it points to an
- *                                     array of @original_size bytes that are
- *                                     the uncompressed input resource.
- * @size:           The size of the resource in the input file.
- * @original_size:  The original (uncompressed) size of the resource. 
- * @offset:        The offset of the start of the resource in @in.  Ignored
- *                     if uncompressed_resource != NULL.
- * @input_ctype:    The compression type of the resource in @in.  Ignored if
- *                     uncompressed_resource != NULL.
- * @out_fp:        The file stream to write the file resource to.
- * @output_type:    The compression type to use when writing the resource to
- *                     @out.
- * @new_size_ret:   A location into which the new compressed size of the file
- *                     resource in returned.
+ * Returns zero on success, nonzero on failure.
  */
-static int recompress_resource(FILE *in_fp, const u8 *uncompressed_resource, 
-                              u64 size, u64 original_size,
-                              off_t offset, int input_ctype, FILE *out_fp,
-                              int output_ctype, u64 *new_size_ret)
+int read_wim_resource(const struct wim_lookup_table_entry *lte, u8 buf[],
+                     size_t size, u64 offset, int flags)
 {
-       int ret;
-       int (*compress)(const void *, uint, void *, uint *);
-       if (output_ctype == WIM_COMPRESSION_TYPE_LZX)
-               compress = lzx_compress;
-       else
-               compress = xpress_compress;
-
-       u8 uncompressed_buf[WIM_CHUNK_SIZE];
-       u8 compressed_buf[WIM_CHUNK_SIZE - 1];
-
-       /* Determine how many compressed chunks the file needs to be divided
-        * into. */
-       u64 num_chunks = (original_size + WIM_CHUNK_SIZE - 1) / WIM_CHUNK_SIZE;
-
-       u64 num_chunk_entries = num_chunks - 1;
-
-       /* Size of the chunk entries--- 8 bytes for files over 4GB, otherwise 4
-        * bytes */
-       uint chunk_entry_size = (original_size >= (u64)1 << 32) ? 8 : 4;
-
-       /* Array in which to construct the chunk offset table. */
-       u64 chunk_offsets[num_chunk_entries];
-
-       /* Offset of the start of the chunk table in the output file. */
-       off_t chunk_tab_offset = ftello(out_fp);
-
-       if (chunk_tab_offset == -1) {
-               ERROR_WITH_ERRNO("Failed to get offset of output file");
-               return WIMLIB_ERR_WRITE;
-       }
-
-       /* Total size of the chunk table (as written to the file) */
-       u64 chunk_tab_size = chunk_entry_size * num_chunk_entries;
-
-       /* Reserve space for the chunk table. */
-       if (fwrite(chunk_offsets, 1, chunk_tab_size, out_fp) !=
-             chunk_tab_size)
-       {
-               ERROR_WITH_ERRNO("Failed to write chunk offset table");
-               return WIMLIB_ERR_WRITE;
-       }
-
-       /* Read each chunk of the file, compress it, write it to the output
-        * file, and update th chunk offset table. */
-       u64 cur_chunk_offset = 0;
-       for (u64 i = 0; i < num_chunks; i++) {
-
-               u64 uncompressed_offset = i * WIM_CHUNK_SIZE;
-               u64 uncompressed_chunk_size = min(WIM_CHUNK_SIZE, 
-                                       original_size - uncompressed_offset);
-
-               const u8 *uncompressed_p;
-               if (uncompressed_resource != NULL) {
-                       uncompressed_p = uncompressed_resource + 
-                                        uncompressed_offset;
+       int ctype;
+       int ret = 0;
+       FILE *fp;
 
-               } else {
-                       /* Read chunk i of the file into uncompressed_buf. */
-                       ret = read_resource(in_fp, size, original_size, offset,
-                                           input_ctype,
-                                           uncompressed_chunk_size, 
-                                           uncompressed_offset, 
-                                           uncompressed_buf);
-                       if (ret != 0)
-                               return ret;
-                       uncompressed_p = uncompressed_buf;
+       /* We shouldn't be allowing read over-runs in any part of the library.
+        * */
+       if (flags & WIMLIB_RESOURCE_FLAG_RAW)
+               wimlib_assert(offset + size <= lte->resource_entry.size);
+       else
+               wimlib_assert(offset + size <= lte->resource_entry.original_size);
+
+       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 != NULL);
+
+               #ifdef WITH_FUSE
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       fp = wim_get_fp(lte->wim);
+                       if (!fp)
+                               return WIMLIB_ERR_OPEN;
+               } else
+               #endif
+               {
+                       wimlib_assert(!(flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED));
+                       wimlib_assert(lte->wim->fp != NULL);
+                       fp = lte->wim->fp;
                }
 
-               if (i != 0)
-                       chunk_offsets[i - 1] = cur_chunk_offset;
-
-               uint compressed_len;
+               ctype = wim_resource_compression_type(lte);
 
-               ret = compress(uncompressed_p, uncompressed_chunk_size, 
-                              compressed_buf, &compressed_len);
+               wimlib_assert(ctype != WIMLIB_COMPRESSION_TYPE_NONE ||
+                             (lte->resource_entry.original_size ==
+                              lte->resource_entry.size));
 
-               /* if compress() returned nonzero, the compressed chunk would
-                * have been at least as large as the uncompressed chunk.  In
-                * this situation, the WIM format requires that the uncompressed
-                * chunk be written instead. */
-               const u8 *buf_to_write;
-               uint len_to_write;
-               if (ret == 0) {
-                       buf_to_write = compressed_buf;
-                       len_to_write = compressed_len;
+               if ((flags & WIMLIB_RESOURCE_FLAG_RAW)
+                   || ctype == WIMLIB_COMPRESSION_TYPE_NONE)
+                       ret = read_uncompressed_resource(fp,
+                                                        lte->resource_entry.offset + offset,
+                                                        size, buf);
+               else
+                       ret = read_compressed_resource(fp,
+                                                      lte->resource_entry.size,
+                                                      lte->resource_entry.original_size,
+                                                      lte->resource_entry.offset,
+                                                      ctype, size, offset, buf);
+       #ifdef WITH_FUSE
+               if (flags & WIMLIB_RESOURCE_FLAG_MULTITHREADED) {
+                       int ret2 = wim_release_fp(lte->wim, fp);
+                       if (ret == 0)
+                               ret = ret2;
+               }
+       #endif
+               break;
+       case RESOURCE_IN_STAGING_FILE:
+       case RESOURCE_IN_FILE_ON_DISK:
+               /* The resource is in some file on the external filesystem and
+                * needs to be read uncompressed */
+               wimlib_assert(lte->file_on_disk != NULL);
+               BUILD_BUG_ON(&lte->file_on_disk != &lte->staging_file_name);
+               /* Use existing file pointer if available; otherwise open one
+                * temporarily */
+               if (lte->file_on_disk_fp) {
+                       fp = lte->file_on_disk_fp;
                } else {
-                       buf_to_write = uncompressed_p;
-                       len_to_write = uncompressed_chunk_size;
+                       fp = fopen(lte->file_on_disk, "rb");
+                       if (!fp) {
+                               ERROR_WITH_ERRNO("Failed to open the file "
+                                                "`%s'", lte->file_on_disk);
+                               ret = WIMLIB_ERR_OPEN;
+                               break;
+                       }
                }
-
-               if (fwrite(buf_to_write, 1, len_to_write, out_fp) !=
-                     len_to_write)
-               {
-                       ERROR_WITH_ERRNO("Failed to write compressed "
-                                        "file resource");
-                       return WIMLIB_ERR_WRITE;
+               ret = read_uncompressed_resource(fp, offset, size, buf);
+               if (fp != lte->file_on_disk_fp)
+                       fclose(fp);
+               break;
+#if defined(__CYGWIN__) || defined(__WIN32__)
+       case RESOURCE_WIN32:
+               wimlib_assert(lte->file_on_disk_fp != NULL);
+               ret = win32_read_file(lte->file_on_disk, lte->file_on_disk_fp,
+                                     offset, size, buf);
+               break;
+#endif
+       case RESOURCE_IN_ATTACHED_BUFFER:
+               /* The resource is directly attached uncompressed in an
+                * in-memory buffer. */
+               wimlib_assert(lte->attached_buffer != NULL);
+               memcpy(buf, lte->attached_buffer + offset, size);
+               break;
+#ifdef WITH_NTFS_3G
+       case RESOURCE_IN_NTFS_VOLUME:
+               wimlib_assert(lte->ntfs_loc != NULL);
+               wimlib_assert(lte->attr != NULL);
+               if (lte->ntfs_loc->is_reparse_point)
+                       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);
+                       ret = WIMLIB_ERR_NTFS_3G;
                }
-               cur_chunk_offset += len_to_write;
+               break;
+#endif
+       default:
+               wimlib_assert(0);
+               ret = -1;
+               break;
        }
-
-       /* The chunk offset after the last chunk, plus the size of the chunk
-        * table, gives the total compressed size of the resource. */
-       *new_size_ret = cur_chunk_offset + chunk_tab_size;
-
-       /* Now that all entries of the chunk table are determined, rewind the
-        * stream to where the chunk table was, and write it back out. */
-
-       if (fseeko(out_fp, chunk_tab_offset, SEEK_SET) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to beginning of chunk table");
-               return WIMLIB_ERR_READ;
-       }
-
-       if (chunk_entry_size == 8) {
-               array_to_le64(chunk_offsets, num_chunk_entries);
-       } else {
-               for (u64 i = 0; i < num_chunk_entries; i++)
-                       ((u32*)chunk_offsets)[i] = to_le32(chunk_offsets[i]);
-       }
-       if (fwrite(chunk_offsets, 1, chunk_tab_size, out_fp) != chunk_tab_size)
-       {
-               ERROR_WITH_ERRNO("Failed to write chunk table");
-               return WIMLIB_ERR_WRITE;
-       }
-
-       if (fseeko(out_fp, 0, SEEK_END) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to end of output file");
-               return WIMLIB_ERR_WRITE;
-       }
-
-       return 0;
+       return ret;
 }
 
-int write_resource_from_memory(const u8 resource[], int out_ctype,
-                              u64 resource_original_size, FILE *out_fp,
-                              u64 *resource_size_ret)
+/*
+ * Reads all the data from the resource corresponding to a WIM lookup table
+ * entry.
+ *
+ * @lte:       The WIM lookup table entry for the resource.
+ * @buf:       Buffer into which to write the data.  It must be at least
+ *             wim_resource_size(lte) bytes long.
+ *
+ * Returns 0 on success; nonzero on failure.
+ */
+int read_full_wim_resource(const struct wim_lookup_table_entry *lte, u8 buf[],
+                          int flags)
 {
-       if (out_ctype == WIM_COMPRESSION_TYPE_NONE) {
-               if (fwrite(resource, 1, resource_original_size, out_fp) != 
-                     resource_original_size)
-               {
-                       ERROR_WITH_ERRNO("Failed to write resource of length "
-                                        "%"PRIu64, resource_original_size);
-                       return WIMLIB_ERR_WRITE;
-               }
-               *resource_size_ret = resource_original_size;
-               return 0;
-       } else {
-               return recompress_resource(NULL, resource,
-                                          resource_original_size,
-                                          resource_original_size, 0, 0, out_fp,
-                                          out_ctype, resource_size_ret);
-       }
+       return read_wim_resource(lte, buf, wim_resource_size(lte), 0, flags);
 }
 
-
-/* 
- * Transfers a file resource from a FILE* opened for reading to a FILE* opened
- * for writing, possibly changing the compression type. 
+/* Extracts the first @size bytes of a WIM resource to somewhere.  In the
+ * process, the SHA1 message digest of the resource is checked if the full
+ * resource is being extracted.
  *
- * @in_fp:             The FILE* that contains the file resource.
- * @size:              The (compressed) size of the file resource.
- * @original_size:     The uncompressed size of the file resource.
- * @offset:            The offset of the file resource in the input file.
- * @input_ctype:       The compression type of the file resource in the input
- *                             file.
- * @out_fp:            The FILE* for the output file.  The file resource is 
- *                             written at the current position of @out.
- * @output_ctype:      The compression type to which the file resource will be
- *                             converted.
- * @output_res_entry:  A pointer to a resource entry that, upon successful
- *                             return of this function,  will have the size,
- *                             original size, offset, and flags fields filled
- *                             in for the file resource written to the output
- *                             file.
- */
-static int transfer_file_resource(FILE *in_fp, u64 size, u64 original_size,
-                                 off_t offset, int input_ctype, FILE *out_fp,
-                                 int output_ctype,
-                                 struct resource_entry *output_res_entry)
+ * @extract_chunk is a function that is called to extract each chunk of the
+ * resource. */
+int extract_wim_resource(const struct wim_lookup_table_entry *lte,
+                        u64 size,
+                        extract_chunk_func_t extract_chunk,
+                        void *extract_chunk_arg)
 {
-       int ret;
-
-       /* Handle zero-length files */
-       if (original_size == 0) {
-               memset(output_res_entry, 0, sizeof(*output_res_entry));
-               return 0;
-       }
-
-       /* Get current offset in the output file. */
-       off_t out_offset = ftello(out_fp);
-       if (out_offset == -1) {
-               ERROR_WITH_ERRNO("Failed to get output position");
-               return WIMLIB_ERR_WRITE;
-       }
-       output_res_entry->offset = (u64)out_offset;
+       u64 bytes_remaining = size;
+       u8 buf[min(WIM_CHUNK_SIZE, bytes_remaining)];
+       u64 offset = 0;
+       int ret = 0;
+       u8 hash[SHA1_HASH_SIZE];
+       bool check_hash = (size == wim_resource_size(lte));
+       SHA_CTX ctx;
 
-       if (output_ctype == input_ctype) {
-               /* The same compression types; simply copy the resource. */
+       if (check_hash)
+               sha1_init(&ctx);
 
-               ret = copy_between_files(in_fp, offset, out_fp, size);
+       while (bytes_remaining) {
+               u64 to_read = min(bytes_remaining, sizeof(buf));
+               ret = read_wim_resource(lte, buf, to_read, offset, 0);
                if (ret != 0)
                        return ret;
-               output_res_entry->size = size;
-       } else {
-               /* Different compression types. */
-
-               if (output_ctype == WIM_COMPRESSION_TYPE_NONE) {
-                       /* Uncompress a compressed file resource */
-                       ret = uncompress_resource(in_fp, size,
-                                                 original_size, offset, 
-                                                 input_ctype, out_fp);
-                       if (ret != 0)
-                               return ret;
-                       output_res_entry->size = original_size;
-               } else {
-                       u64 new_size;
-                       /* Compress an uncompressed file resource, or compress a
-                        * compressed file resource using a different
-                        * compression type */
-                       ret = recompress_resource(in_fp, NULL, size,
-                                                 original_size,
-                                                 offset, input_ctype, out_fp,
-                                                 output_ctype, &new_size);
-                       if (ret != 0)
-                               return ret;
-                       output_res_entry->size = new_size;
+               if (check_hash)
+                       sha1_update(&ctx, buf, to_read);
+               ret = extract_chunk(buf, to_read, offset, extract_chunk_arg);
+               if (ret != 0) {
+                       ERROR_WITH_ERRNO("Error extracting WIM resource");
+                       return ret;
+               }
+               bytes_remaining -= to_read;
+               offset += to_read;
+       }
+       if (check_hash) {
+               sha1_final(hash, &ctx);
+               if (!hashes_equal(hash, lte->hash)) {
+               #ifdef ENABLE_ERROR_MESSAGES
+                       ERROR("Invalid checksum on the following WIM resource:");
+                       print_lookup_table_entry(lte, stderr);
+               #endif
+                       return WIMLIB_ERR_INVALID_RESOURCE_HASH;
                }
-
        }
-
-       output_res_entry->original_size = original_size;
-       if (output_ctype == WIM_COMPRESSION_TYPE_NONE)
-               output_res_entry->flags = 0;
-       else
-               output_res_entry->flags = WIM_RESHDR_FLAG_COMPRESSED;
        return 0;
 }
 
-/* 
- * 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
- * filesystem.  The subdir_offset field of each directory entry gives the start
- * of its child entries from the beginning of the metadata resource.  An
- * end-of-directory is signaled by a directory entry of length '0', really of
- * length 8, because that's how long the 'length' field is.
+/* Write @n bytes from @buf to the file descriptor @fd, retrying on internupt
+ * and on short writes.
  *
- * @fp:                The FILE* for the input WIM file.
- * @wim_ctype: The compression type of the WIM file.
- * @imd:       Pointer to the image metadata structure.  Its
- *             `lookup_table_entry' member specifies the lookup table entry for
- *             the metadata resource.  The rest of the image metadata entry
- *             will be filled in by this function.
- *
- * @return:    Zero on success, nonzero on failure.
- */
-int read_metadata_resource(FILE *fp, int wim_ctype, struct image_metadata *imd)
+ * Returns short count and set errno on failure. */
+static ssize_t full_write(int fd, const void *buf, size_t n)
 {
-       u8 *buf;
-       int ctype;
-       u32 dentry_offset;
-       int ret;
-       const struct resource_entry *res_entry;
-       struct dentry *dentry;
-       struct wim_security_data *sd;
-       struct link_group_table *lgt;
-
-       res_entry = &imd->metadata_lte->resource_entry;
-
-       DEBUG("Reading metadata resource: length = %"PRIu64", "
-             "offset = %"PRIu64"",
-             res_entry->original_size, res_entry->offset);
-
-       if (res_entry->original_size < 8) {
-               ERROR("Expected at least 8 bytes for the metadata resource");
-               return WIMLIB_ERR_INVALID_RESOURCE_SIZE;
-       }
-
-       /* Allocate memory for the uncompressed metadata resource. */
-       buf = MALLOC(res_entry->original_size);
-
-       if (!buf) {
-               ERROR("Failed to allocate %"PRIu64" bytes for uncompressed "
-                     "metadata resource", res_entry->original_size);
-               return WIMLIB_ERR_NOMEM;
-       }
-
-       /* Determine the compression type of the metadata resource. */
-       ctype = resource_compression_type(wim_ctype, res_entry->flags);
-
-       /* Read the metadata resource into memory.  (It may be compressed.) */
-       ret = read_full_resource(fp, res_entry->size, 
-                                res_entry->original_size, res_entry->offset, 
-                                ctype, buf);
-       if (ret != 0)
-               goto out_free_buf;
-
-       DEBUG("Finished reading metadata resource into memory.");
-
-       /* The root directory entry starts after security data, on an 8-byte
-        * aligned address. 
-        *
-        * The security data starts with a 4-byte integer giving its total
-        * length. */
-
-       /* Read the security data into a wim_security_data structure. */
-       ret = read_security_data(buf, res_entry->original_size, &sd);
-       if (ret != 0)
-               goto out_free_buf;
-
-       dentry = MALLOC(sizeof(struct dentry));
-       if (!dentry) {
-               ERROR("Failed to allocate %zu bytes for root dentry",
-                     sizeof(struct dentry));
-               ret = WIMLIB_ERR_NOMEM;
-               goto out_free_security_data;
+       const char *p = buf;
+       ssize_t ret;
+       ssize_t total = 0;
+
+       while (total != n) {
+               ret = write(fd, p, n);
+               if (ret < 0) {
+                       if (errno == EINTR)
+                               continue;
+                       else
+                               break;
+               }
+               total += ret;
+               p += ret;
        }
-
-       get_u32(buf, &dentry_offset);
-       if (dentry_offset == 0)
-               dentry_offset = 8;
-       dentry_offset = (dentry_offset + 7) & ~7;
-               
-       ret = read_dentry(buf, res_entry->original_size, dentry_offset, dentry);
-       /* This is the root dentry, so set its pointers correctly. */
-       dentry->parent = dentry;
-       dentry->next   = dentry;
-       dentry->prev   = dentry;
-       if (ret != 0)
-               goto out_free_dentry_tree;
-
-       /* Now read the entire directory entry tree. */
-       ret = read_dentry_tree(buf, res_entry->original_size, dentry);
-       if (ret != 0)
-               goto out_free_dentry_tree;
-
-       /* Calculate the full paths in the dentry tree. */
-       ret = for_dentry_in_tree(dentry, calculate_dentry_full_path, NULL);
-       if (ret != 0)
-               goto out_free_dentry_tree;
-
-       lgt = new_link_group_table(9001);
-       if (!lgt)
-               goto out_free_dentry_tree;
-       ret = for_dentry_in_tree(dentry, link_group_table_insert, lgt);
-       if (ret != 0)
-               goto out_free_lgt;
-
-       imd->lgt           = lgt;
-       imd->security_data = sd;
-       imd->root_dentry   = dentry;
-       goto out_free_buf;
-out_free_lgt:
-       free_link_group_table(lgt);
-out_free_dentry_tree:
-       free_dentry_tree(dentry, NULL, false);
-out_free_security_data:
-       free_security_data(sd);
-out_free_buf:
-       FREE(buf);
-       return ret;
+       return total;
 }
 
-/* Write the metadata resource for the current image. */
-int write_metadata_resource(WIMStruct *w)
+int extract_wim_chunk_to_fd(const u8 *buf, size_t len, u64 offset, void *arg)
 {
-       FILE *out;
-       u8 *buf;
-       u8 *p;
-       int ret;
-       u64 subdir_offset;
-       struct dentry *root;
-       struct lookup_table_entry *lte;
-       struct resource_entry *res_entry;
-       off_t metadata_offset;
-       u64 metadata_original_size;
-       u64 metadata_compressed_size;
-       int metadata_ctype;
-       u8  hash[WIM_HASH_SIZE];
-
-       DEBUG("Writing metadata resource for image %d", w->current_image);
-
-       out = w->out_fp;
-       root = wim_root_dentry(w);
-       metadata_ctype = wimlib_get_compression_type(w);
-       metadata_offset = ftello(out);
-       if (metadata_offset == -1)
+       int fd = *(int*)arg;
+       ssize_t ret = full_write(fd, buf, len);
+       if (ret < len) {
+               ERROR_WITH_ERRNO("Error writing to file descriptor");
                return WIMLIB_ERR_WRITE;
-
-       struct wim_security_data *sd = wim_security_data(w);
-       if (sd)
-               subdir_offset = sd->total_length + root->length + 8;
-       else
-               subdir_offset = 8 + root->length + 8;
-       calculate_subdir_offsets(root, &subdir_offset);
-       metadata_original_size = subdir_offset;
-       buf = MALLOC(metadata_original_size);
-       if (!buf) {
-               ERROR("Failed to allocate %"PRIu64" bytes for "
-                     "metadata resource", metadata_original_size);
-               return WIMLIB_ERR_NOMEM;
-       }
-
-       p = write_security_data(sd, buf);
-
-       DEBUG("Writing dentry tree.");
-       p = write_dentry_tree(root, p);
-
-       /* Like file resources, the lookup table entry for a metadata resource
-        * uses for the hash code a SHA1 message digest of its uncompressed
-        * contents. */
-       sha1_buffer(buf, metadata_original_size, hash);
-
-       ret = write_resource_from_memory(buf, 
-                                        metadata_ctype,
-                                        metadata_original_size, 
-                                        out,
-                                        &metadata_compressed_size);
-       FREE(buf);
-       if (ret != 0)
-               return ret;
-
-       /* Update the lookup table entry, including the hash and output resource
-        * entry fields, for this image's metadata resource.  */
-       lte = wim_metadata_lookup_table_entry(w);
-       res_entry = &lte->output_resource_entry;
-       lte->out_refcnt++;
-       if (memcmp(hash, lte->hash, WIM_HASH_SIZE) != 0) {
-               lookup_table_unlink(w->lookup_table, lte);
-               memcpy(lte->hash, hash, WIM_HASH_SIZE);
-               lookup_table_insert(w->lookup_table, lte);
-       }
-       res_entry->original_size = metadata_original_size;
-       res_entry->offset        = metadata_offset;
-       res_entry->size          = metadata_compressed_size;
-       res_entry->flags         = WIM_RESHDR_FLAG_METADATA;
-       if (metadata_ctype != WIM_COMPRESSION_TYPE_NONE)
-               res_entry->flags |= WIM_RESHDR_FLAG_COMPRESSED;
-       return 0;
-}
-
-static int write_file_resource(WIMStruct *w, const u8 hash[])
-{
-       /* Get the lookup entry for the file resource. */
-       struct lookup_table_entry *lte;
-       
-       lte = __lookup_resource(w->lookup_table, hash);
-       if (!lte)
-               return 0;
-
-       /* No need to write file resources twice. */
-       if (++lte->out_refcnt != 1)
-               return 0;
-
-       /* do not write empty resources */
-       if (lte->resource_entry.original_size == 0)
-               return 0;
-
-       int out_wim_ctype = wimlib_get_compression_type(w);
-       struct resource_entry *output_res_entry = &lte->output_resource_entry;
-       u64 len;
-       FILE *in_fp;
-       FILE *out_fp = w->out_fp;
-       int ret = 0;
-
-       /* Figure out if we can read the resource from the WIM file, or
-        * if we have to read it from the filesystem outside, or if it's a
-        * symbolic link with the data already in memory pointed to by a field
-        * of the lookup table entry. */
-       if (lte->is_symlink) {
-               off_t offset = ftello(w->out_fp);
-               u64 new_size;
-
-               if (offset == -1) {
-                       ERROR_WITH_ERRNO("Could not get position in output "
-                                        "file");
-                       return WIMLIB_ERR_WRITE;
-               }
-
-               wimlib_assert(lte->symlink_buf);
-
-               len = lte->resource_entry.original_size;
-
-               ret = recompress_resource(NULL, lte->symlink_buf, len, len, 0,
-                                         0, out_fp, out_wim_ctype, &new_size);
-               output_res_entry->size = new_size;
-               output_res_entry->original_size = len;
-               output_res_entry->offset = offset;
-               output_res_entry->flags = (out_wim_ctype == WIM_COMPRESSION_TYPE_NONE)
-                                               ? 0 : WIM_RESHDR_FLAG_COMPRESSED;
-       } else if (lte->file_on_disk) {
-
-               /* Read from disk (uncompressed) */
-
-               len = lte->resource_entry.original_size;
-
-               in_fp = fopen(lte->file_on_disk, "rb");
-               if (!in_fp) {
-                       ERROR_WITH_ERRNO("Failed to open the file `%s'",
-                                        lte->file_on_disk);
-                       return WIMLIB_ERR_OPEN;
-               }
-
-               ret = transfer_file_resource(in_fp, len, len, 0,
-                                            WIM_COMPRESSION_TYPE_NONE, out_fp,
-                                            out_wim_ctype, output_res_entry);
-               fclose(in_fp);
        } else {
-               int in_wim_ctype;
-
-               /* Read from input WIM (possibly compressed) */
-
-               /* It may be a different WIM file, in the case of
-                * exporting images from one WIM file to another */
-               if (lte->other_wim_fp) {
-                       /* Different WIM file. */
-                       in_fp = lte->other_wim_fp;
-                       in_wim_ctype = lte->other_wim_ctype;
-               } else {
-                       /* Same WIM file. */
-                       in_fp = w->fp;
-                       in_wim_ctype = out_wim_ctype;
-               }
-               int input_res_ctype = resource_compression_type(
-                                               in_wim_ctype, 
-                                               lte->resource_entry.flags);
-
-               ret = transfer_file_resource(in_fp,
-                                            lte->resource_entry.size,
-                                            lte->resource_entry.original_size, 
-                                            lte->resource_entry.offset,
-                                            input_res_ctype, 
-                                            out_fp,
-                                            out_wim_ctype,
-                                            output_res_entry);
+               return 0;
        }
-       return ret;
 }
 
-/* 
- * Writes a dentry's resources to the output file. 
+/*
+ * 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.
  *
- * @dentry:  The dentry for the file resource.
- * @wim_p:   A pointer to the WIMStruct.  The fields of interest to this
- *          function are the input and output file streams and the lookup
- *          table, and the alternate data streams.
+ * The output_resource_entry, out_refcnt, and part_number fields of @lte are
+ * updated.
  *
- * @return zero on success, nonzero on failure. 
+ * (This function is confusing and should be refactored somehow.)
  */
-int write_dentry_resources(struct dentry *dentry, void *wim_p)
+int copy_resource(struct wim_lookup_table_entry *lte, void *wim)
 {
-       WIMStruct *w = wim_p;
+       WIMStruct *w = wim;
        int ret;
 
-       /* Directories don't need file resources. */
-       if (dentry_is_directory(dentry))
+       if ((lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA) &&
+           !w->write_metadata)
                return 0;
 
-       ret = write_file_resource(w, dentry->hash);
+       ret = write_wim_resource(lte, w->out_fp,
+                                wim_resource_compression_type(lte),
+                                &lte->output_resource_entry, 0);
        if (ret != 0)
                return ret;
-       for (u16 i = 0; i < dentry->num_ads; i++) {
-               ret = write_file_resource(w, dentry->ads_entries[i].hash);
-               if (ret != 0)
-                       return ret;
-       }
+       lte->out_refcnt = lte->refcnt;
+       lte->part_number = w->hdr.part_number;
        return 0;
 }
-