write_integrity_table(): Fix documented return values
[wimlib] / src / integrity.c
index 49fe514..6d007fe 100644 (file)
 /*
  * integrity.c
  *
- * WIM files can optionally contain an array of SHA1 message digests at the end,
- * one digest for each 1 MB of the file.  This file implements the checking of
- * the digests, and the writing of the digests for new WIM files.
+ * WIM files can optionally contain a table of SHA1 message digests at the end,
+ * one digest for each chunk of the file of some specified size (often 10 MB).
+ * This file implements the checking and writing of this table.
  */
 
 /*
- * 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)
+ * 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
+ * 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
+ * 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 "io.h"
-#include "sha1.h"
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include "wimlib/assert.h"
+#include "wimlib/endianness.h"
+#include "wimlib/error.h"
+#include "wimlib/file_io.h"
+#include "wimlib/integrity.h"
+#include "wimlib/resource.h"
+#include "wimlib/sha1.h"
+#include "wimlib/wim.h"
 
 /* Size, in bytes, of each SHA1-summed chunk, when wimlib writes integrity
  * information. */
 #define INTEGRITY_CHUNK_SIZE 10485760
 
-/*
- * Verifies the integrity of a WIM. 
- *
- * @fp:                   FILE* of the WIM, currently positioned at the end of the header. 
- * @num_bytes:    Number of bytes to verify the integrity of.
- * @chunk_size:           Chunk size per SHA1 message digest.
- * @sha1sums:     Array of SHA1 message digests; 20 bytes each, one per chunk.
- * @show_progress: Nonzero if the percent complete is to be printed after every
- *                     chunk.
- * @status:       On success, set to WIM_INTEGRITY_OK or WIM_INTEGRITY_NOT_OK 
- *                     based on whether the WIM is intact or not.
- */
-static int verify_integrity(FILE *fp, u64 num_bytes, u32 chunk_size, 
-                           const u8 *sha1sums, int show_progress,
-                           int *status)
+/* Only use a different chunk size for compatiblity with an existing integrity
+ * table if the chunk size is between these two numbers. */
+#define INTEGRITY_MIN_CHUNK_SIZE 4096
+#define INTEGRITY_MAX_CHUNK_SIZE 134217728
+
+struct integrity_table {
+       u32 size;
+       u32 num_entries;
+       u32 chunk_size;
+       u8  sha1sums[][20];
+} _packed_attribute;
+
+static int
+calculate_chunk_sha1(struct filedes *in_fd, size_t this_chunk_size,
+                    off_t offset, u8 sha1_md[])
 {
-       char  *chunk_buf;
-       u8     resblock[WIM_HASH_SIZE];
-       u64    bytes_remaining;
+       u8 buf[BUFFER_SIZE];
+       SHA_CTX ctx;
+       size_t bytes_remaining;
        size_t bytes_to_read;
-       uint   percent_done;
-       int    ret;
+       int ret;
 
-       chunk_buf = MALLOC(chunk_size);
-       if (!chunk_buf) {
-               ERROR("Failed to allocate %u byte buffer for integrity chunks",
-                     chunk_size);
-               return WIMLIB_ERR_NOMEM;
-       }
-       bytes_remaining = num_bytes;
-       while (bytes_remaining != 0) {
-               if (show_progress) {
-                       percent_done = (num_bytes - bytes_remaining) * 100 / 
-                                       num_bytes;
-                       printf("Verifying integrity of WIM (%"PRIu64" bytes "
-                                       "remaining, %u%% done)       \r", 
-                                       bytes_remaining, percent_done);
-                       fflush(stdout);
-               }
-               bytes_to_read = min(chunk_size, bytes_remaining);
-               if (fread(chunk_buf, 1, bytes_to_read, fp) != bytes_to_read) {
-                       if (feof(fp)) {
-                               ERROR("Unexpected EOF while verifying "
-                                     "integrity of WIM");
-                       } else {
-                               ERROR_WITH_ERRNO("File stream error while "
-                                                "verifying integrity of WIM");
-                       }
-                       ret = WIMLIB_ERR_READ;
-                       goto verify_integrity_error;
-               }
-               sha1_buffer(chunk_buf, bytes_to_read, resblock);
-               if (memcmp(resblock, sha1sums, WIM_HASH_SIZE) != 0) {
-                       *status = WIM_INTEGRITY_NOT_OK;
-                       goto verify_integrity_done;
+       bytes_remaining = this_chunk_size;
+       sha1_init(&ctx);
+       do {
+               bytes_to_read = min(bytes_remaining, sizeof(buf));
+               ret = full_pread(in_fd, buf, bytes_to_read, offset);
+               if (ret) {
+                       ERROR_WITH_ERRNO("Read error while calculating "
+                                        "integrity checksums");
+                       return ret;
                }
-               sha1sums += WIM_HASH_SIZE;
+               sha1_update(&ctx, buf, bytes_to_read);
                bytes_remaining -= bytes_to_read;
-       }
-       *status = WIM_INTEGRITY_OK;
-verify_integrity_done:
-       ret = 0;
-verify_integrity_error:
-       FREE(chunk_buf);
-       if (show_progress)
-               putchar('\n');
-       return ret;
+               offset += bytes_to_read;
+       } while (bytes_remaining);
+       sha1_final(sha1_md, &ctx);
+       return 0;
 }
 
+
 /*
- * Verifies the integrity of the WIM. 
+ * read_integrity_table: -  Reads the integrity table from a WIM file.
+ *
+ * @wim:
+ *     WIMStruct for the WIM file; @wim->hdr.integrity specifies the location
+ *     of the integrity table.  The integrity table must exist (i.e.
+ *     res_entry->offset must not be 0).  @wim->in_fd is expected to be a
+ *     seekable file descriptor to the WIM file opened for reading.
  *
- * @show_progress: Nonzero if the percent complete is to be printed after every
- *                     chunk.
- * @status:       On success, set to WIM_INTEGRITY_OK, WIM_INTEGRITY_NOT_OK,
- *                     or WIM_INTEGRITY_NONEXISTENT.
+ * @num_checked_bytes:
+ *     Number of bytes of data that should be checked by the integrity table.
  *
- * Returns: 0, WIMLIB_ERR_INVALID_INTEGRITY_TABLE, WIMLIB_ERR_NOMEM, or
- * WIMLIB_ERR_READ.  If nonzero, the boolean pointed to by @ok is not changed.
+ * @table_ret:
+ *     On success, a pointer to an in-memory structure containing the integrity
+ *     information is written to this location.
+ *
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_INVALID_INTEGRITY_TABLE
+ *     WIMLIB_ERR_NOMEM
+ *     WIMLIB_ERR_READ
+ *     WIMLIB_ERR_UNEXPECTED_END_OF_FILE
  */
-int check_wim_integrity(WIMStruct *w, int show_progress, int *status)
+static int
+read_integrity_table(WIMStruct *wim, u64 num_checked_bytes,
+                    struct integrity_table **table_ret)
 {
-
-       struct resource_entry *res_entry;
-       int ctype;
-       u8 *buf = NULL;
+       void *buf;
+       struct integrity_table *table;
        int ret;
-       u32 integrity_table_size;
-       u32 num_entries;
-       u32 chunk_size;
-       const u8 *p;
-       u64 expected_size;
-       u64 end_lookup_table_offset;
-       u64 bytes_to_check;
-       u64 expected_num_entries;
 
-       res_entry = &w->hdr.integrity;
-       if (res_entry->size == 0) {
-               DEBUG("No integrity information.");
-               *status = WIM_INTEGRITY_NONEXISTENT;
-               return 0;
-       }
-       ctype = wim_resource_compression_type(w, res_entry);
-       if (res_entry->original_size < 12) {
-               ERROR("Integrity table is too short");
-               return WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
+       if (wim->hdr.integrity.size < 8)
+               goto invalid;
+
+       DEBUG("Reading integrity table (offset %"PRIu64", "
+             "original_size %"PRIu64")",
+             wim->hdr.integrity.offset, wim->hdr.integrity.original_size);
+
+       ret = res_entry_to_data(&wim->hdr.integrity, wim, &buf);
+       if (ret)
+               return ret;
+       table = buf;
+
+       table->size        = le32_to_cpu(table->size);
+       table->num_entries = le32_to_cpu(table->num_entries);
+       table->chunk_size  = le32_to_cpu(table->chunk_size);
+
+       DEBUG("table->size = %u, table->num_entries = %u, "
+             "table->chunk_size = %u",
+             table->size, table->num_entries, table->chunk_size);
+
+       if (table->size != wim->hdr.integrity.original_size ||
+           table->size != (u64)table->num_entries * SHA1_HASH_SIZE + 12 ||
+           table->chunk_size == 0 ||
+           table->num_entries != DIV_ROUND_UP(num_checked_bytes, table->chunk_size))
+       {
+               FREE(table);
+               goto invalid;
        }
 
-       /* Read the integrity table into memory. */
-       buf = MALLOC(res_entry->original_size);
-       if (!buf) {
-               ERROR("Out of memory (needed %zu bytes for integrity table)",
-                     res_entry->original_size);
-               ret = WIMLIB_ERR_NOMEM;
-               goto out;
-       }
-       ret = read_full_resource(w->fp, res_entry->size,
-                                res_entry->original_size,
-                                res_entry->offset, ctype, buf);
-       if (ret != 0) {
-               ERROR("Failed to read integrity table (size = %"PRIu64", "
-                     "original_size = %"PRIu64", offset = "
-                     "%"PRIu64", ctype = %d",
-                     (u64)res_entry->size, res_entry->original_size,
-                     res_entry->offset, ctype);
-               goto out;
-       }
+       *table_ret = table;
+       return 0;
 
-       p = get_u32(buf, &integrity_table_size);
-       p = get_u32(p, &num_entries);
-       p = get_u32(p, &chunk_size);
-
-       /* p now points to the array of SHA1 message digests for the WIM. */
+invalid:
+       ERROR("Integrity table is invalid");
+       return WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
+}
 
-       /* Make sure the integrity table is the right size. */
-       if (integrity_table_size != res_entry->original_size) {
-               ERROR("Inconsistent integrity table sizes: header says %u "
-                     "bytes but resource entry says "
-                     "%"PRIu64" bytes",
-                     integrity_table_size, res_entry->original_size);
-               ret = WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
-               goto out;
+/*
+ * calculate_integrity_table():
+ *
+ * Calculates an integrity table for the data in a file beginning at offset 208
+ * (WIM_HEADER_DISK_SIZE).
+ *
+ * @in_fd:
+ *     File descriptor for the file to be checked, opened for reading.  Does
+ *     not need to be at any specific location in the file.
+ *
+ * @new_check_end:
+ *     Offset of byte after the last byte to be checked.
+ *
+ * @old_table:
+ *     If non-NULL, a pointer to the table containing the previously calculated
+ *     integrity data for a prefix of this file.
+ *
+ * @old_check_end:
+ *     If @old_table is non-NULL, the byte after the last byte that was checked
+ *     in the old table.  Must be less than or equal to new_check_end.
+ *
+ * @progress_func:
+ *     If non-NULL, a progress function that will be called after every
+ *     calculated chunk.
+ *
+ * @integrity_table_ret:
+ *     On success, a pointer to the calculated integrity table is written into
+ *     this location.
+ *
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_NOMEM
+ *     WIMLIB_ERR_READ
+ *     WIMLIB_ERR_UNEXPECTED_END_OF_FILE
+ */
+static int
+calculate_integrity_table(struct filedes *in_fd,
+                         off_t new_check_end,
+                         const struct integrity_table *old_table,
+                         off_t old_check_end,
+                         wimlib_progress_func_t progress_func,
+                         struct integrity_table **integrity_table_ret)
+{
+       int ret;
+       size_t chunk_size = INTEGRITY_CHUNK_SIZE;
+
+       /* If an old table is provided, set the chunk size to be compatible with
+        * the old chunk size, unless the old chunk size was weird. */
+       if (old_table != NULL) {
+               if (old_table->num_entries == 0 ||
+                   old_table->chunk_size < INTEGRITY_MIN_CHUNK_SIZE ||
+                   old_table->chunk_size > INTEGRITY_MAX_CHUNK_SIZE)
+                       old_table = NULL;
+               else
+                       chunk_size = old_table->chunk_size;
        }
 
-       DEBUG("integrity_table_size = %u, num_entries = %u, chunk_size = %u",
-             integrity_table_size, num_entries, chunk_size);
 
+       u64 old_check_bytes = old_check_end - WIM_HEADER_DISK_SIZE;
+       u64 new_check_bytes = new_check_end - WIM_HEADER_DISK_SIZE;
 
-       expected_size = num_entries * WIM_HASH_SIZE + 12;
-
-       if (integrity_table_size != expected_size) {
-               ERROR("Integrity table is %u bytes, but expected %"PRIu64" "
-                     "bytes to hold %u entries", 
-                     integrity_table_size, expected_size, num_entries);
-               ret = WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
-               goto out;
-       }
-
-       if (chunk_size == 0) {
-               ERROR("Cannot use integrity chunk size of 0");
-               ret = WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
-               goto out;
-       }
+       u32 old_num_chunks = DIV_ROUND_UP(old_check_bytes, chunk_size);
+       u32 new_num_chunks = DIV_ROUND_UP(new_check_bytes, chunk_size);
 
-       end_lookup_table_offset = w->hdr.lookup_table_res_entry.offset +
-                                 w->hdr.lookup_table_res_entry.size;
+       size_t old_last_chunk_size = MODULO_NONZERO(old_check_bytes, chunk_size);
+       size_t new_last_chunk_size = MODULO_NONZERO(new_check_bytes, chunk_size);
 
-       bytes_to_check = end_lookup_table_offset - WIM_HEADER_DISK_SIZE;
+       size_t new_table_size = 12 + new_num_chunks * SHA1_HASH_SIZE;
 
-       expected_num_entries = (bytes_to_check + chunk_size - 1) / chunk_size;
-
-       if (num_entries != expected_num_entries) {
-               ERROR("%"PRIu64" entries would be required to checksum "
-                     "the %"PRIu64" bytes from the end of the header to the",
-                     expected_num_entries, bytes_to_check);
-               ERROR("end of the lookup table with a chunk size of %u, but "
-                     "there were only %u entries", expected_num_entries,
-                     bytes_to_check, chunk_size, num_entries);
-               ret = WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
-               goto out;
+       struct integrity_table *new_table = MALLOC(new_table_size);
+       if (!new_table)
+               return WIMLIB_ERR_NOMEM;
+       new_table->num_entries = new_num_chunks;
+       new_table->size = new_table_size;
+       new_table->chunk_size = chunk_size;
+
+       u64 offset = WIM_HEADER_DISK_SIZE;
+       union wimlib_progress_info progress;
+
+       if (progress_func) {
+               progress.integrity.total_bytes      = new_check_bytes;
+               progress.integrity.total_chunks     = new_num_chunks;
+               progress.integrity.completed_chunks = 0;
+               progress.integrity.completed_bytes  = 0;
+               progress.integrity.chunk_size       = chunk_size;
+               progress.integrity.filename         = NULL;
+               progress_func(WIMLIB_PROGRESS_MSG_CALC_INTEGRITY,
+                             &progress);
        }
 
-       /* The integrity checking starts after the header, so seek to the offset
-        * in the WIM after the header. */
-
-       if (fseeko(w->fp, WIM_HEADER_DISK_SIZE, SEEK_SET) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to byte %u of WIM to check "
-                                "integrity", WIM_HEADER_DISK_SIZE);
-               ret = WIMLIB_ERR_READ;
-               goto out;
+       for (u32 i = 0; i < new_num_chunks; i++) {
+               size_t this_chunk_size;
+               if (i == new_num_chunks - 1)
+                       this_chunk_size = new_last_chunk_size;
+               else
+                       this_chunk_size = chunk_size;
+               if (old_table &&
+                   ((this_chunk_size == chunk_size && i < old_num_chunks - 1) ||
+                     (i == old_num_chunks - 1 && this_chunk_size == old_last_chunk_size)))
+               {
+                       /* Can use SHA1 message digest from old integrity table
+                        * */
+                       copy_hash(new_table->sha1sums[i], old_table->sha1sums[i]);
+               } else {
+                       /* Calculate the SHA1 message digest of this chunk */
+                       ret = calculate_chunk_sha1(in_fd, this_chunk_size,
+                                                  offset, new_table->sha1sums[i]);
+                       if (ret) {
+                               FREE(new_table);
+                               return ret;
+                       }
+               }
+               offset += this_chunk_size;
+               if (progress_func) {
+                       progress.integrity.completed_chunks++;
+                       progress.integrity.completed_bytes += this_chunk_size;
+                       progress_func(WIMLIB_PROGRESS_MSG_CALC_INTEGRITY,
+                                     &progress);
+               }
        }
-       /* call verify_integrity(), which does the actual checking of the SHA1
-        * message digests. */
-       ret = verify_integrity(w->fp, bytes_to_check, chunk_size, p, 
-                              show_progress, status);
-out:
-       FREE(buf);
-       return ret;
+       *integrity_table_ret = new_table;
+       return 0;
 }
 
-/* 
- * Writes integrity information to the output stream for a WIM file being
- * written. 
+/*
+ * write_integrity_table():
+ *
+ * Writes a WIM integrity table (a list of SHA1 message digests of raw 10 MiB
+ * chunks of the file).
+ *
+ * This function can optionally re-use entries from an older integrity table.
+ * To do this, make @integrity_res_entry point to the resource entry for the
+ * older table (note: this is an input-output parameter), and set
+ * @old_lookup_table_end to the offset of the byte directly following the last
+ * byte checked by the old table.  If the old integrity table is invalid or
+ * cannot be read, a warning is printed and the integrity information is
+ * re-calculated.
+ *
+ * @wim:
+ *     WIMStruct for the WIM file.  @wim->out_fd must be a seekable descriptor
+ *     to the new WIM file, opened read-write, positioned at the location at
+ *     which the integrity table is to be written.  Furthermore,
+ *     @wim->hdr.integrity is expected to be a resource entry which will be set
+ *     to the integrity table information on success.  In addition, if
+ *     @old_lookup_table_end != 0, @wim->hdr.integrity must initially contain
+ *     information about the old integrity table, and @wim->in_fd must be a
+ *     seekable descriptor to the original WIM file opened for reading.
+ *
+ * @new_lookup_table_end:
+ *     The offset of the byte directly following the lookup table in the WIM
+ *     being written.
  *
- * @end_header_offset is the offset of the byte after the header, which is the
- *     beginning of the region that is checksummed.
+ * @old_lookup_table_end:
+ *     If nonzero, the offset of the byte directly following the old lookup
+ *     table in the WIM.
  *
- * @end_lookup_table_offset is the offset of the byte after the lookup table,
- *     which is the end of the region that is checksummed. 
+ * @progress_func
+ *     If non-NULL, a progress function that will be called after every
+ *     calculated chunk.
+ *
+ * Return values:
+ *     WIMLIB_ERR_SUCCESS (0)
+ *     WIMLIB_ERR_NOMEM
+ *     WIMLIB_ERR_UNEXPECTED_END_OF_FILE
+ *     WIMLIB_ERR_WRITE
  */
-int write_integrity_table(FILE *out, u64 end_header_offset, 
-                         u64 end_lookup_table_offset, int show_progress)
+int
+write_integrity_table(WIMStruct *wim,
+                     off_t new_lookup_table_end,
+                     off_t old_lookup_table_end,
+                     wimlib_progress_func_t progress_func)
 {
-       u64   bytes_to_check;
-       u64   bytes_remaining;
-       u8   *buf;
-       u8   *p;
-       char *chunk_buf;
-       u32   num_entries;
-       u32   integrity_table_size;
-       int   ret;
-
-       DEBUG("Writing integrity table");
-       if (fseeko(out, end_header_offset, SEEK_SET) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to byte %"PRIu64" of WIM to "
-                                "calculate integrity data", end_header_offset);
-               return WIMLIB_ERR_WRITE;
+       struct integrity_table *old_table;
+       struct integrity_table *new_table;
+       int ret;
+       u32 new_table_size;
+
+       wimlib_assert(old_lookup_table_end <= new_lookup_table_end);
+
+       old_table = NULL;
+       if (wim_has_integrity_table(wim) && old_lookup_table_end != 0) {
+               ret = read_integrity_table(wim,
+                                          old_lookup_table_end - WIM_HEADER_DISK_SIZE,
+                                          &old_table);
+               if (ret == WIMLIB_ERR_INVALID_INTEGRITY_TABLE) {
+                       WARNING("Old integrity table is invalid! "
+                               "Ignoring it");
+               } else if (ret != 0) {
+                       WARNING("Can't read old integrity table! "
+                               "Ignoring it");
+               }
        }
 
-       bytes_to_check = end_lookup_table_offset - end_header_offset;
-       num_entries = bytes_to_check / INTEGRITY_CHUNK_SIZE +
-                       (bytes_to_check % INTEGRITY_CHUNK_SIZE != 0);
-       integrity_table_size = num_entries * WIM_HASH_SIZE + 3 * sizeof(u32);
-
-       DEBUG("integrity table size = %u", integrity_table_size);
-
+       ret = calculate_integrity_table(&wim->out_fd, new_lookup_table_end,
+                                       old_table, old_lookup_table_end,
+                                       progress_func, &new_table);
+       if (ret)
+               goto out_free_old_table;
+
+       new_table_size = new_table->size;
+
+       new_table->size        = cpu_to_le32(new_table->size);
+       new_table->num_entries = cpu_to_le32(new_table->num_entries);
+       new_table->chunk_size  = cpu_to_le32(new_table->chunk_size);
+
+       ret = write_wim_resource_from_buffer(new_table,
+                                            new_table_size,
+                                            0,
+                                            &wim->out_fd,
+                                            WIMLIB_COMPRESSION_TYPE_NONE,
+                                            &wim->hdr.integrity,
+                                            NULL,
+                                            0);
+       FREE(new_table);
+out_free_old_table:
+       FREE(old_table);
+       return ret;
+}
 
-       buf = MALLOC(integrity_table_size);
-       if (!buf) {
-               ERROR("Failed to allocate %u bytes for integrity table",
-                     integrity_table_size);
-               return WIMLIB_ERR_NOMEM;
+/*
+ * verify_integrity():
+ *
+ * Checks a WIM for consistency with the integrity table.
+ *
+ * @in_fd:
+ *     File descriptor to the WIM file, opened for reading.
+ *
+ * @table:
+ *     The integrity table for the WIM, read into memory.
+ *
+ * @bytes_to_check:
+ *     Number of bytes in the WIM that need to be checked (offset of end of the
+ *     lookup table minus offset of end of the header).
+ *
+ * @progress_func
+ *     If non-NULL, a progress function that will be called after every
+ *     verified chunk.
+ *
+ * Returns:
+ *     > 0 (WIMLIB_ERR_READ, WIMLIB_ERR_UNEXPECTED_END_OF_FILE) on error
+ *     0 (WIM_INTEGRITY_OK) if the integrity was checked successfully and there
+ *     were no inconsistencies.
+ *     -1 (WIM_INTEGRITY_NOT_OK) if the WIM failed the integrity check.
+ */
+static int
+verify_integrity(struct filedes *in_fd, const tchar *filename,
+                const struct integrity_table *table,
+                u64 bytes_to_check,
+                wimlib_progress_func_t progress_func)
+{
+       int ret;
+       u64 offset = WIM_HEADER_DISK_SIZE;
+       u8 sha1_md[SHA1_HASH_SIZE];
+       union wimlib_progress_info progress;
+
+       if (progress_func) {
+               progress.integrity.total_bytes      = bytes_to_check;
+               progress.integrity.total_chunks     = table->num_entries;
+               progress.integrity.completed_chunks = 0;
+               progress.integrity.completed_bytes  = 0;
+               progress.integrity.chunk_size       = table->chunk_size;
+               progress.integrity.filename         = filename;
+               progress_func(WIMLIB_PROGRESS_MSG_VERIFY_INTEGRITY,
+                             &progress);
        }
-
-       p = put_u32(buf, integrity_table_size);
-       p = put_u32(p, num_entries);
-       p = put_u32(p, INTEGRITY_CHUNK_SIZE);
-
-       chunk_buf = MALLOC(INTEGRITY_CHUNK_SIZE);
-       if (!chunk_buf) {
-               ERROR("Failed to allocate %u bytes for integrity chunk buffer",
-                     INTEGRITY_CHUNK_SIZE);
-               ret = WIMLIB_ERR_NOMEM;
-               goto err2;
+       for (u32 i = 0; i < table->num_entries; i++) {
+               size_t this_chunk_size;
+               if (i == table->num_entries - 1)
+                       this_chunk_size = MODULO_NONZERO(bytes_to_check,
+                                                        table->chunk_size);
+               else
+                       this_chunk_size = table->chunk_size;
+
+               ret = calculate_chunk_sha1(in_fd, this_chunk_size, offset, sha1_md);
+               if (ret)
+                       return ret;
+
+               if (!hashes_equal(sha1_md, table->sha1sums[i]))
+                       return WIM_INTEGRITY_NOT_OK;
+
+               offset += this_chunk_size;
+               if (progress_func) {
+                       progress.integrity.completed_chunks++;
+                       progress.integrity.completed_bytes += this_chunk_size;
+                       progress_func(WIMLIB_PROGRESS_MSG_VERIFY_INTEGRITY,
+                                     &progress);
+               }
        }
+       return WIM_INTEGRITY_OK;
+}
 
-       bytes_remaining = bytes_to_check;
-
-       DEBUG("Bytes to check = %"PRIu64, bytes_to_check);
-
-       while (bytes_remaining != 0) {
 
-               uint percent_done = (bytes_to_check - bytes_remaining) * 
-                                   100 / bytes_to_check;
+/*
+ * check_wim_integrity():
+ *
+ * Verifies the integrity of the WIM by making sure the SHA1 message digests of
+ * ~10 MiB chunks of the WIM match up with the values given in the integrity
+ * table.
+ *
+ * @wim:
+ *     The WIM, opened for reading.
+ *
+ * @progress_func
+ *     If non-NULL, a progress function that will be called after every
+ *     verified chunk.
+ *
+ * Returns:
+ *     > 0 (WIMLIB_ERR_INVALID_INTEGRITY_TABLE, WIMLIB_ERR_READ,
+ *          WIMLIB_ERR_UNEXPECTED_END_OF_FILE) on error
+ *     0 (WIM_INTEGRITY_OK) if the integrity was checked successfully and there
+ *     were no inconsistencies.
+ *     -1 (WIM_INTEGRITY_NOT_OK) if the WIM failed the integrity check.
+ *     -2 (WIM_INTEGRITY_NONEXISTENT) if the WIM contains no integrity
+ *     information.
+ */
+int
+check_wim_integrity(WIMStruct *wim, wimlib_progress_func_t progress_func)
+{
+       int ret;
+       u64 bytes_to_check;
+       struct integrity_table *table;
+       u64 end_lookup_table_offset;
 
-               if (show_progress) {
-                       printf("Calculating integrity checksums for WIM "
-                                       "(%"PRIu64" bytes remaining, %u%% "
-                                       "done)      \r", 
-                                       bytes_remaining, percent_done);
-                       fflush(stdout);
-               }
+       if (!wim_has_integrity_table(wim)) {
+               DEBUG("No integrity information.");
+               return WIM_INTEGRITY_NONEXISTENT;
+       }
 
+       end_lookup_table_offset = wim->hdr.lookup_table_res_entry.offset +
+                                 wim->hdr.lookup_table_res_entry.size;
 
-               size_t bytes_to_read = min(INTEGRITY_CHUNK_SIZE, bytes_remaining);
-               size_t bytes_read = fread(chunk_buf, 1, bytes_to_read, out);
-               if (bytes_read != bytes_to_read) {
-                       if (feof(out)) {
-                               ERROR("Unexpected EOF while calculating "
-                                     "integrity checksums");
-                       } else {
-                               ERROR_WITH_ERRNO("File stream error while "
-                                                "calculating integrity "
-                                                "checksums");
-                       }
-                       ret = WIMLIB_ERR_READ;
-                       goto err2;
-               }
-               sha1_buffer(chunk_buf, bytes_read, p);
-               p += WIM_HASH_SIZE;
-               bytes_remaining -= bytes_read;
-       }
-       if (show_progress)
-               puts("Calculating integrity checksums for WIM "
-                               "(0 bytes remaining, 100% done)"
-                               "                       ");
-
-       if (fseeko(out, 0, SEEK_END) != 0) {
-               ERROR_WITH_ERRNO("Failed to seek to end of WIM to write "
-                                "integrity table");
-               ret = WIMLIB_ERR_WRITE;
-               goto err1;
+       if (end_lookup_table_offset < WIM_HEADER_DISK_SIZE) {
+               ERROR("WIM lookup table ends before WIM header ends!");
+               return WIMLIB_ERR_INVALID_INTEGRITY_TABLE;
        }
 
-       if (fwrite(buf, 1, integrity_table_size, out) != integrity_table_size) {
-               ERROR_WITH_ERRNO("Failed to write integrity table to end of "
-                                "WIM");
-               ret = WIMLIB_ERR_WRITE;
-               goto err1;
-       }
-       ret = 0;
-err1:
-       FREE(chunk_buf);
-err2:
-       FREE(buf);
+       bytes_to_check = end_lookup_table_offset - WIM_HEADER_DISK_SIZE;
+
+       ret = read_integrity_table(wim, bytes_to_check, &table);
+       if (ret)
+               return ret;
+       ret = verify_integrity(&wim->in_fd, wim->filename, table,
+                              bytes_to_check, progress_func);
+       FREE(table);
        return ret;
 }