new_wim_struct(): Don't dereference NULL in out-of-memory case
[wimlib] / src / wim.c
index bba8487..e1cda33 100644 (file)
--- a/src/wim.c
+++ b/src/wim.c
@@ -5,8 +5,6 @@
 /*
  * Copyright (C) 2012, 2013 Eric Biggers
  *
- * wimlib - Library for working with WIM files
- *
  * 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
  * along with wimlib; if not, see http://www.gnu.org/licenses/.
  */
 
-#include "config.h"
-
-#include <errno.h>
-#include <fcntl.h>
-#include <limits.h>
-#include <stdarg.h>
-#include <stdlib.h>
-#include <unistd.h>
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
 
+#include "wimlib/error.h"
+#include "wimlib/dentry.h"
+#include "wimlib/encoding.h"
+#include "wimlib/file_io.h"
+#include "wimlib/integrity.h"
+#include "wimlib/lookup_table.h"
+#include "wimlib/metadata.h"
 #ifdef WITH_NTFS_3G
-#  include <time.h>
-#  include <ntfs-3g/volume.h>
+#  include "wimlib/ntfs_3g.h" /* for do_ntfs_umount() */
 #endif
+#include "wimlib/security.h"
+#include "wimlib/wim.h"
+#include "wimlib/xml.h"
 
 #ifdef __WIN32__
-#  include "win32.h"
-#else
-#  include <langinfo.h>
+#  include "wimlib/win32.h" /* for realpath() replacement */
 #endif
 
-#include "buffer_io.h"
-#include "dentry.h"
-#include "lookup_table.h"
-#include "wimlib_internal.h"
-#include "xml.h"
+#include <errno.h>
+#include <fcntl.h>
+#ifndef __WIN32__
+#  include <langinfo.h>
+#endif
+#include <limits.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <unistd.h>
 
 static int
-image_print_metadata(WIMStruct *w)
+image_print_metadata(WIMStruct *wim)
 {
-       DEBUG("Printing metadata for image %d", w->current_image);
-       print_security_data(wim_security_data(w));
-       return for_dentry_in_tree(wim_root_dentry(w), print_dentry,
-                                 w->lookup_table);
+       DEBUG("Printing metadata for image %d", wim->current_image);
+       print_wim_security_data(wim_security_data(wim));
+       return for_dentry_in_tree(wim_root_dentry(wim), print_dentry,
+                                 wim->lookup_table);
 }
 
 
-static int
-image_print_files(WIMStruct *w)
-{
-       return for_dentry_in_tree(wim_root_dentry(w), print_dentry_full_path,
-                                 NULL);
-}
-
 static WIMStruct *
-new_wim_struct()
+new_wim_struct(void)
 {
-       WIMStruct *w = CALLOC(1, sizeof(WIMStruct));
-#ifdef WITH_FUSE
-       if (pthread_mutex_init(&w->fp_tab_mutex, NULL) != 0) {
-               ERROR_WITH_ERRNO("Failed to initialize mutex");
-               FREE(w);
-               w = NULL;
+       WIMStruct *wim = CALLOC(1, sizeof(WIMStruct));
+       if (wim) {
+               wim->in_fd.fd = -1;
+               wim->out_fd.fd = -1;
+               INIT_LIST_HEAD(&wim->subwims);
        }
-#endif
-       return w;
-
+       return wim;
 }
 
 /*
@@ -88,7 +82,7 @@ new_wim_struct()
  * the WIM only once, with that image selected.
  */
 int
-for_image(WIMStruct *w, int image, int (*visitor)(WIMStruct *))
+for_image(WIMStruct *wim, int image, int (*visitor)(WIMStruct *))
 {
        int ret;
        int start;
@@ -97,102 +91,43 @@ for_image(WIMStruct *w, int image, int (*visitor)(WIMStruct *))
 
        if (image == WIMLIB_ALL_IMAGES) {
                start = 1;
-               end = w->hdr.image_count;
-       } else if (image >= 1 && image <= w->hdr.image_count) {
+               end = wim->hdr.image_count;
+       } else if (image >= 1 && image <= wim->hdr.image_count) {
                start = image;
                end = image;
        } else {
                return WIMLIB_ERR_INVALID_IMAGE;
        }
        for (i = start; i <= end; i++) {
-               ret = select_wim_image(w, i);
+               ret = select_wim_image(wim, i);
                if (ret != 0)
                        return ret;
-               ret = visitor(w);
+               ret = visitor(wim);
                if (ret != 0)
                        return ret;
        }
        return 0;
 }
 
-static int
-sort_image_metadata_by_position(const void *p1, const void *p2)
-{
-       const struct wim_image_metadata *imd1 = p1;
-       const struct wim_image_metadata *imd2 = p2;
-       u64 offset1 = imd1->metadata_lte->resource_entry.offset;
-       u64 offset2 = imd2->metadata_lte->resource_entry.offset;
-       if (offset1 < offset2)
-               return -1;
-       else if (offset1 > offset2)
-               return 1;
-       else
-               return 0;
-}
-
-/*
- * If @lte points to a metadata resource, append it to the list of metadata
- * resources in the WIMStruct.  Otherwise, do nothing.
- */
-static int
-append_metadata_resource_entry(struct wim_lookup_table_entry *lte, void *wim_p)
-{
-       WIMStruct *w = wim_p;
-       int ret = 0;
-
-       if (lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA) {
-               if (w->current_image == w->hdr.image_count) {
-                       ERROR("The WIM header says there are %u images in the WIM,\n"
-                             "        but we found more metadata resources than this",
-                             w->hdr.image_count);
-                       ret = WIMLIB_ERR_IMAGE_COUNT;
-               } else {
-                       DEBUG("Found metadata resource for image %u at "
-                             "offset %"PRIu64".",
-                             w->current_image + 1,
-                             lte->resource_entry.offset);
-                       w->image_metadata[
-                               w->current_image++].metadata_lte = lte;
-               }
-       }
-       return ret;
-}
-
-/* Returns the compression type given in the flags of a WIM header. */
-static int
-wim_hdr_flags_compression_type(int wim_hdr_flags)
-{
-       if (wim_hdr_flags & WIM_HDR_FLAG_COMPRESSION) {
-               if (wim_hdr_flags & WIM_HDR_FLAG_COMPRESS_LZX)
-                       return WIMLIB_COMPRESSION_TYPE_LZX;
-               else if (wim_hdr_flags & WIM_HDR_FLAG_COMPRESS_XPRESS)
-                       return WIMLIB_COMPRESSION_TYPE_XPRESS;
-               else
-                       return WIMLIB_COMPRESSION_TYPE_INVALID;
-       } else {
-               return WIMLIB_COMPRESSION_TYPE_NONE;
-       }
-}
-
-/*
- * Creates a WIMStruct for a new WIM file.
- */
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_create_new_wim(int ctype, WIMStruct **w_ret)
+wimlib_create_new_wim(int ctype, WIMStruct **wim_ret)
 {
-       WIMStruct *w;
+       WIMStruct *wim;
        struct wim_lookup_table *table;
        int ret;
 
-       DEBUG("Creating new WIM with %s compression.",
+       wimlib_global_init(WIMLIB_INIT_FLAG_ASSUME_UTF8);
+
+       DEBUG("Creating new WIM with %"TS" compression.",
              wimlib_get_compression_type_string(ctype));
 
        /* Allocate the WIMStruct. */
-       w = new_wim_struct();
-       if (!w)
+       wim = new_wim_struct();
+       if (!wim)
                return WIMLIB_ERR_NOMEM;
 
-       ret = init_header(&w->hdr, ctype);
+       ret = init_wim_header(&wim->hdr, ctype);
        if (ret != 0)
                goto out_free;
 
@@ -201,22 +136,18 @@ wimlib_create_new_wim(int ctype, WIMStruct **w_ret)
                ret = WIMLIB_ERR_NOMEM;
                goto out_free;
        }
-       w->lookup_table = table;
-       *w_ret = w;
+       wim->lookup_table = table;
+       wim->refcnts_ok = 1;
+       wim->compression_type = ctype;
+       *wim_ret = wim;
        return 0;
 out_free:
-       FREE(w);
+       FREE(wim);
        return ret;
 }
 
-WIMLIBAPI int
-wimlib_get_num_images(const WIMStruct *w)
-{
-       return w->hdr.image_count;
-}
-
 int
-select_wim_image(WIMStruct *w, int image)
+select_wim_image(WIMStruct *wim, int image)
 {
        struct wim_image_metadata *imd;
        int ret;
@@ -228,52 +159,51 @@ select_wim_image(WIMStruct *w, int image)
                return WIMLIB_ERR_INVALID_IMAGE;
        }
 
-       if (image == w->current_image)
+       if (image == wim->current_image)
                return 0;
 
-       if (image < 1 || image > w->hdr.image_count) {
+       if (image < 1 || image > wim->hdr.image_count) {
                ERROR("Cannot select image %d: There are only %u images",
-                     image, w->hdr.image_count);
+                     image, wim->hdr.image_count);
                return WIMLIB_ERR_INVALID_IMAGE;
        }
 
+       if (!wim_has_metadata(wim)) {
+               ERROR("\"%"TS"\" does not contain metadata resources!", wim->filename);
+               if (wim->hdr.part_number != 1)
+                       ERROR("Specify the first part of the split WIM instead.");
+               return WIMLIB_ERR_METADATA_NOT_FOUND;
+       }
+
        /* If a valid image is currently selected, it can be freed if it is not
         * modified.  */
-       if (w->current_image != WIMLIB_NO_IMAGE) {
-               imd = wim_get_current_image_metadata(w);
+       if (wim->current_image != WIMLIB_NO_IMAGE) {
+               imd = wim_get_current_image_metadata(wim);
                if (!imd->modified) {
-                       DEBUG("Freeing image %u", w->current_image);
-                       destroy_image_metadata(imd, NULL);
-                       imd->root_dentry = NULL;
-                       imd->security_data = NULL;
-                       INIT_HLIST_HEAD(&imd->inode_list);
+                       wimlib_assert(list_empty(&imd->unhashed_streams));
+                       DEBUG("Freeing image %u", wim->current_image);
+                       destroy_image_metadata(imd, NULL, false);
                }
        }
-       w->current_image = image;
-       imd = &w->image_metadata[image - 1];
-       if (imd->root_dentry) {
+       wim->current_image = image;
+       imd = wim_get_current_image_metadata(wim);
+       if (imd->root_dentry || imd->modified) {
                ret = 0;
        } else {
                #ifdef ENABLE_DEBUG
                DEBUG("Reading metadata resource specified by the following "
                      "lookup table entry:");
-               print_lookup_table_entry(imd->metadata_lte, stdout);
+               print_lookup_table_entry(imd->metadata_lte, stderr);
                #endif
-               ret = read_metadata_resource(w, imd);
+               ret = read_metadata_resource(wim, imd);
                if (ret)
-                       w->current_image = WIMLIB_NO_IMAGE;
+                       wim->current_image = WIMLIB_NO_IMAGE;
        }
        return ret;
 }
 
 
-/* Returns the compression type of the WIM file. */
-WIMLIBAPI int
-wimlib_get_compression_type(const WIMStruct *w)
-{
-       return wim_hdr_flags_compression_type(w->hdr.flags);
-}
-
+/* API function documented in wimlib.h  */
 WIMLIBAPI const tchar *
 wimlib_get_compression_type_string(int ctype)
 {
@@ -289,72 +219,38 @@ wimlib_get_compression_type_string(int ctype)
        }
 }
 
-/*
- * Returns the number of an image in the WIM file, given a string that is either
- * the number of the image, or the name of the image.  The images are numbered
- * starting at 1.
- */
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_resolve_image(WIMStruct *w, const tchar *image_name_or_num)
+wimlib_resolve_image(WIMStruct *wim, const tchar *image_name_or_num)
 {
        tchar *p;
-       int image;
+       long image;
        int i;
 
        if (!image_name_or_num || !*image_name_or_num)
                return WIMLIB_NO_IMAGE;
 
-       if (tstrcmp(image_name_or_num, T("all")) == 0
-           || tstrcmp(image_name_or_num, T("*")) == 0)
+       if (!tstrcasecmp(image_name_or_num, T("all"))
+           || !tstrcasecmp(image_name_or_num, T("*")))
                return WIMLIB_ALL_IMAGES;
        image = tstrtol(image_name_or_num, &p, 10);
        if (p != image_name_or_num && *p == T('\0') && image > 0) {
-               if (image > w->hdr.image_count)
+               if (image > wim->hdr.image_count)
                        return WIMLIB_NO_IMAGE;
                return image;
        } else {
-               for (i = 1; i <= w->hdr.image_count; i++) {
-                       if (tstrcmp(image_name_or_num,
-                                   wimlib_get_image_name(w, i)) == 0)
+               for (i = 1; i <= wim->hdr.image_count; i++) {
+                       if (!tstrcmp(image_name_or_num,
+                                    wimlib_get_image_name(wim, i)))
                                return i;
                }
                return WIMLIB_NO_IMAGE;
        }
 }
 
-/* Prints some basic information about a WIM file. */
+/* API function documented in wimlib.h  */
 WIMLIBAPI void
-wimlib_print_wim_information(const WIMStruct *w)
-{
-       const struct wim_header *hdr;
-
-       hdr = &w->hdr;
-       tputs(T("WIM Information:"));
-       tputs(T("----------------"));
-       tprintf(T("Path:           %"TS"\n"), w->filename);
-       tfputs(T("GUID:           0x"), stdout);
-       print_byte_field(hdr->guid, WIM_GID_LEN);
-       tputchar(T('\n'));
-       tprintf(T("Image Count:    %d\n"), hdr->image_count);
-       tprintf(T("Compression:    %"TS"\n"),
-               wimlib_get_compression_type_string(wimlib_get_compression_type(w)));
-       tprintf(T("Part Number:    %d/%d\n"), hdr->part_number, hdr->total_parts);
-       tprintf(T("Boot Index:     %d\n"), hdr->boot_idx);
-       tprintf(T("Size:           %"PRIu64" bytes\n"),
-               wim_info_get_total_bytes(w->wim_info));
-       tprintf(T("Integrity Info: %"TS"\n"),
-               (w->hdr.integrity.offset != 0) ? T("yes") : T("no"));
-       tputchar(T('\n'));
-}
-
-WIMLIBAPI bool
-wimlib_has_integrity_table(const WIMStruct *w)
-{
-       return w->hdr.integrity.size != 0;
-}
-
-WIMLIBAPI void
-wimlib_print_available_images(const WIMStruct *w, int image)
+wimlib_print_available_images(const WIMStruct *wim, int image)
 {
        int first;
        int last;
@@ -363,8 +259,8 @@ wimlib_print_available_images(const WIMStruct *w, int image)
        if (image == WIMLIB_ALL_IMAGES) {
                n = tprintf(T("Available Images:\n"));
                first = 1;
-               last = w->hdr.image_count;
-       } else if (image >= 1 && image <= w->hdr.image_count) {
+               last = wim->hdr.image_count;
+       } else if (image >= 1 && image <= wim->hdr.image_count) {
                n = tprintf(T("Information for Image %d\n"), image);
                first = image;
                last = image;
@@ -377,74 +273,118 @@ wimlib_print_available_images(const WIMStruct *w, int image)
                tputchar(T('-'));
        tputchar(T('\n'));
        for (i = first; i <= last; i++)
-               print_image_info(w->wim_info, i);
+               print_image_info(wim->wim_info, i);
 }
 
 
-/* Prints the metadata for the specified image, which may be WIMLIB_ALL_IMAGES, but
- * not WIMLIB_NO_IMAGE. */
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_print_metadata(WIMStruct *w, int image)
+wimlib_print_metadata(WIMStruct *wim, int image)
 {
-       if (w->hdr.part_number != 1) {
-               ERROR("Cannot show the metadata from part %hu of a %hu-part split WIM!",
-                      w->hdr.part_number, w->hdr.total_parts);
-               ERROR("Select the first part of the split WIM to see the metadata.");
-               return WIMLIB_ERR_SPLIT_UNSUPPORTED;
-       }
-       return for_image(w, image, image_print_metadata);
+       return for_image(wim, image, image_print_metadata);
 }
 
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_print_files(WIMStruct *w, int image)
+wimlib_get_wim_info(WIMStruct *wim, struct wimlib_wim_info *info)
 {
-       if (w->hdr.part_number != 1) {
-               ERROR("Cannot list the files from part %hu of a %hu-part split WIM!",
-                      w->hdr.part_number, w->hdr.total_parts);
-               ERROR("Select the first part of the split WIM if you'd like to list the files.");
-               return WIMLIB_ERR_SPLIT_UNSUPPORTED;
-       }
-       return for_image(w, image, image_print_files);
+       memset(info, 0, sizeof(struct wimlib_wim_info));
+       memcpy(info->guid, wim->hdr.guid, WIMLIB_GUID_LEN);
+       info->image_count = wim->hdr.image_count;
+       info->boot_index = wim->hdr.boot_idx;
+       info->wim_version = WIM_VERSION;
+       info->chunk_size = WIM_CHUNK_SIZE;
+       info->part_number = wim->hdr.part_number;
+       info->total_parts = wim->hdr.total_parts;
+       info->compression_type = wim->compression_type;
+       info->total_bytes = wim_info_get_total_bytes(wim->wim_info);
+       info->has_integrity_table = wim_has_integrity_table(wim);
+       info->opened_from_file = (wim->filename != NULL);
+       info->is_readonly = (wim->hdr.flags & WIM_HDR_FLAG_READONLY) ||
+                            (wim->hdr.total_parts != 1) ||
+                            (wim->filename && taccess(wim->filename, W_OK));
+       info->has_rpfix = (wim->hdr.flags & WIM_HDR_FLAG_RP_FIX) != 0;
+       info->is_marked_readonly = (wim->hdr.flags & WIM_HDR_FLAG_READONLY) != 0;
+       info->write_in_progress = (wim->hdr.flags & WIM_HDR_FLAG_WRITE_IN_PROGRESS) != 0;
+       info->metadata_only = (wim->hdr.flags & WIM_HDR_FLAG_METADATA_ONLY) != 0;
+       info->resource_only = (wim->hdr.flags & WIM_HDR_FLAG_RESOURCE_ONLY) != 0;
+       info->spanned = (wim->hdr.flags & WIM_HDR_FLAG_SPANNED) != 0;
+       info->pipable = wim_is_pipable(wim);
+       return 0;
 }
 
-/* Sets the index of the bootable image. */
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_set_boot_idx(WIMStruct *w, int boot_idx)
+wimlib_set_wim_info(WIMStruct *wim, const struct wimlib_wim_info *info, int which)
 {
-       if (w->hdr.total_parts != 1) {
-               ERROR("Cannot modify the boot index of a split WIM!");
-               return WIMLIB_ERR_SPLIT_UNSUPPORTED;
+       int ret;
+
+       if (which & WIMLIB_CHANGE_READONLY_FLAG) {
+               if (info->is_marked_readonly)
+                       wim->hdr.flags |= WIM_HDR_FLAG_READONLY;
+               else
+                       wim->hdr.flags &= ~WIM_HDR_FLAG_READONLY;
        }
-       if (boot_idx < 0 || boot_idx > w->hdr.image_count)
-               return WIMLIB_ERR_INVALID_IMAGE;
-       w->hdr.boot_idx = boot_idx;
 
-       if (boot_idx == 0) {
-               memset(&w->hdr.boot_metadata_res_entry, 0,
-                      sizeof(struct resource_entry));
-       } else {
-               memcpy(&w->hdr.boot_metadata_res_entry,
-                      &w->image_metadata[
-                         boot_idx - 1].metadata_lte->resource_entry,
-                      sizeof(struct resource_entry));
+       if ((which & ~WIMLIB_CHANGE_READONLY_FLAG) == 0)
+               return 0;
+
+       ret = can_modify_wim(wim);
+       if (ret)
+               return ret;
+
+       if (which & WIMLIB_CHANGE_GUID) {
+               memcpy(wim->hdr.guid, info->guid, WIM_GID_LEN);
+               wim->guid_set_explicitly = 1;
        }
 
+       if (which & WIMLIB_CHANGE_BOOT_INDEX) {
+               if (info->boot_index > wim->hdr.image_count) {
+                       ERROR("%u is not 0 or a valid image in the WIM to mark as bootable",
+                             info->boot_index);
+                       return WIMLIB_ERR_INVALID_IMAGE;
+               }
+               wim->hdr.boot_idx = info->boot_index;
+       }
+
+       if (which & WIMLIB_CHANGE_RPFIX_FLAG) {
+               if (info->has_rpfix)
+                       wim->hdr.flags |= WIM_HDR_FLAG_RP_FIX;
+               else
+                       wim->hdr.flags &= ~WIM_HDR_FLAG_RP_FIX;
+       }
        return 0;
 }
 
-WIMLIBAPI int
-wimlib_get_part_number(const WIMStruct *w, int *total_parts_ret)
+static int
+do_open_wim(const tchar *filename, struct filedes *fd_ret)
 {
-       if (total_parts_ret)
-               *total_parts_ret = w->hdr.total_parts;
-       return w->hdr.part_number;
+       int raw_fd;
+
+       raw_fd = topen(filename, O_RDONLY | O_BINARY);
+       if (raw_fd < 0) {
+               ERROR_WITH_ERRNO("Can't open \"%"TS"\" read-only", filename);
+               return WIMLIB_ERR_OPEN;
+       }
+       filedes_init(fd_ret, raw_fd);
+       return 0;
 }
 
+int
+reopen_wim(WIMStruct *wim)
+{
+       wimlib_assert(!filedes_valid(&wim->in_fd));
+       return do_open_wim(wim->filename, &wim->in_fd);
+}
 
-WIMLIBAPI int
-wimlib_get_boot_idx(const WIMStruct *w)
+int
+close_wim(WIMStruct *wim)
 {
-       return w->hdr.boot_idx;
+       if (filedes_valid(&wim->in_fd)) {
+               filedes_close(&wim->in_fd);
+               filedes_invalidate(&wim->in_fd);
+       }
+       return 0;
 }
 
 /*
@@ -452,67 +392,102 @@ wimlib_get_boot_idx(const WIMStruct *w)
  * lookup table, and optionally checks the integrity.
  */
 static int
-begin_read(WIMStruct *w, const tchar *in_wim_path, int open_flags,
-          wimlib_progress_func_t progress_func)
+begin_read(WIMStruct *wim, const void *wim_filename_or_fd,
+          int open_flags, wimlib_progress_func_t progress_func)
 {
        int ret;
        int xml_num_images;
+       const tchar *wimfile;
 
-       DEBUG("Reading the WIM file `%"TS"'", in_wim_path);
+       if (open_flags & WIMLIB_OPEN_FLAG_FROM_PIPE) {
+               wimfile = NULL;
+               filedes_init(&wim->in_fd, *(const int*)wim_filename_or_fd);
+               wim->in_fd.is_pipe = 1;
+       } else {
+               wimfile = wim_filename_or_fd;
+               DEBUG("Reading the WIM file `%"TS"'", wimfile);
+               ret = do_open_wim(wimfile, &wim->in_fd);
+               if (ret)
+                       return ret;
 
-       w->fp = tfopen(in_wim_path, T("rb"));
-       if (!w->fp) {
-               ERROR_WITH_ERRNO("Failed to open `%"TS"' for reading",
-                                in_wim_path);
-               return WIMLIB_ERR_OPEN;
+               /* The absolute path to the WIM is requested so that
+                * wimlib_overwrite() still works even if the process changes
+                * its working directory.  This actually happens if a WIM is
+                * mounted read-write, since the FUSE thread changes directory
+                * to "/", and it needs to be able to find the WIM file again.
+                *
+                * This will break if the full path to the WIM changes in the
+                * intervening time...
+                *
+                * Warning: in Windows native builds, realpath() calls the
+                * replacement function in win32_replacements.c.
+                */
+               wim->filename = realpath(wimfile, NULL);
+               if (!wim->filename) {
+                       ERROR_WITH_ERRNO("Failed to resolve WIM filename");
+                       if (errno == ENOMEM)
+                               return WIMLIB_ERR_NOMEM;
+                       else
+                               return WIMLIB_ERR_OPEN;
+               }
        }
 
-       /* The absolute path to the WIM is requested so that wimlib_overwrite()
-        * still works even if the process changes its working directory.  This
-        * actually happens if a WIM is mounted read-write, since the FUSE
-        * thread changes directory to "/", and it needs to be able to find the
-        * WIM file again.
-        *
-        * This will break if the full path to the WIM changes in the
-        * intervening time...
-        *
-        * Warning: in Windows native builds, realpath() calls the replacement
-        * function in win32.c.
-        */
-       w->filename = realpath(in_wim_path, NULL);
-       if (!w->filename) {
-               ERROR_WITH_ERRNO("Failed to resolve WIM filename");
-               if (errno == ENOMEM)
-                       return WIMLIB_ERR_NOMEM;
-               else
-                       return WIMLIB_ERR_OPEN;
+       ret = read_wim_header(wim->filename, &wim->in_fd, &wim->hdr);
+       if (ret)
+               return ret;
+
+       if (wim->hdr.flags & WIM_HDR_FLAG_WRITE_IN_PROGRESS) {
+               WARNING("The WIM_HDR_FLAG_WRITE_IN_PROGRESS is set in the header of \"%"TS"\".\n"
+                       "          It may be being changed by another process, or a process\n"
+                       "          may have crashed while writing the WIM.", wimfile);
        }
 
-       ret = read_header(w->fp, &w->hdr, open_flags);
-       if (ret != 0)
-               return ret;
+       if (open_flags & WIMLIB_OPEN_FLAG_WRITE_ACCESS) {
+               ret = can_modify_wim(wim);
+               if (ret)
+                       return ret;
+       }
 
-       DEBUG("According to header, WIM contains %u images", w->hdr.image_count);
+       if ((open_flags & WIMLIB_OPEN_FLAG_ERROR_IF_SPLIT) &&
+           (wim->hdr.total_parts != 1))
+               return WIMLIB_ERR_IS_SPLIT_WIM;
+
+       DEBUG("According to header, WIM contains %u images", wim->hdr.image_count);
 
        /* If the boot index is invalid, print a warning and set it to 0 */
-       if (w->hdr.boot_idx > w->hdr.image_count) {
+       if (wim->hdr.boot_idx > wim->hdr.image_count) {
                WARNING("In `%"TS"', image %u is marked as bootable, "
                        "but there are only %u images in the WIM",
-                       in_wim_path, w->hdr.boot_idx, w->hdr.image_count);
-               w->hdr.boot_idx = 0;
+                       wimfile, wim->hdr.boot_idx, wim->hdr.image_count);
+               wim->hdr.boot_idx = 0;
        }
 
-       if (wimlib_get_compression_type(w) == WIMLIB_COMPRESSION_TYPE_INVALID) {
-               ERROR("Invalid compression type (WIM header flags = 0x%x)",
-                     w->hdr.flags);
-               return WIMLIB_ERR_INVALID_COMPRESSION_TYPE;
+       /* Check and cache the compression type */
+       if (wim->hdr.flags & WIM_HDR_FLAG_COMPRESSION) {
+               if (wim->hdr.flags & WIM_HDR_FLAG_COMPRESS_LZX) {
+                       if (wim->hdr.flags & WIM_HDR_FLAG_COMPRESS_XPRESS) {
+                               ERROR("Multiple compression flags are set in \"%"TS"\"",
+                                     wimfile);
+                               return WIMLIB_ERR_INVALID_COMPRESSION_TYPE;
+                       }
+                       wim->compression_type = WIMLIB_COMPRESSION_TYPE_LZX;
+               } else if (wim->hdr.flags & WIM_HDR_FLAG_COMPRESS_XPRESS) {
+                       wim->compression_type = WIMLIB_COMPRESSION_TYPE_XPRESS;
+               } else {
+                       ERROR("The compression flag is set on \"%"TS"\", but "
+                             "neither the XPRESS nor LZX flag is set",
+                             wimfile);
+                       return WIMLIB_ERR_INVALID_COMPRESSION_TYPE;
+               }
+       } else {
+               wim->compression_type = WIMLIB_COMPRESSION_TYPE_NONE;
        }
 
        if (open_flags & WIMLIB_OPEN_FLAG_CHECK_INTEGRITY) {
-               ret = check_wim_integrity(w, progress_func);
+               ret = check_wim_integrity(wim, progress_func);
                if (ret == WIM_INTEGRITY_NONEXISTENT) {
                        WARNING("No integrity information for `%"TS"'; skipping "
-                               "integrity check.", in_wim_path);
+                               "integrity check.", wimfile);
                } else if (ret == WIM_INTEGRITY_NOT_OK) {
                        ERROR("WIM is not intact! (Failed integrity check)");
                        return WIMLIB_ERR_INTEGRITY;
@@ -521,186 +496,344 @@ begin_read(WIMStruct *w, const tchar *in_wim_path, int open_flags,
                }
        }
 
-       ret = read_lookup_table(w);
-       if (ret != 0)
-               return ret;
-
-       if (w->hdr.image_count != 0) {
-               w->image_metadata = CALLOC(w->hdr.image_count,
-                                          sizeof(struct wim_image_metadata));
+       if (wim->hdr.image_count != 0 && wim->hdr.part_number == 1) {
+               wim->image_metadata = new_image_metadata_array(wim->hdr.image_count);
+               if (!wim->image_metadata)
+                       return WIMLIB_ERR_NOMEM;
+       }
 
-               if (!w->image_metadata) {
-                       ERROR("Failed to allocate memory for %u image metadata structures",
-                             w->hdr.image_count);
+       if (open_flags & WIMLIB_OPEN_FLAG_FROM_PIPE) {
+               wim->lookup_table = new_lookup_table(9001);
+               if (!wim->lookup_table)
                        return WIMLIB_ERR_NOMEM;
+       } else {
+               ret = read_wim_lookup_table(wim);
+               if (ret)
+                       return ret;
+
+               ret = read_wim_xml_data(wim);
+               if (ret)
+                       return ret;
+
+               xml_num_images = wim_info_get_num_images(wim->wim_info);
+               if (xml_num_images != wim->hdr.image_count) {
+                       ERROR("In the file `%"TS"', there are %u <IMAGE> elements "
+                             "in the XML data,", wimfile, xml_num_images);
+                       ERROR("but %u images in the WIM!  There must be exactly one "
+                             "<IMAGE> element per image.", wim->hdr.image_count);
+                       return WIMLIB_ERR_IMAGE_COUNT;
                }
+               DEBUG("Done beginning read of WIM file `%"TS"'.", wimfile);
        }
-       w->current_image = 0;
+       return 0;
+}
 
-       DEBUG("Looking for metadata resources in the lookup table.");
+int
+open_wim_as_WIMStruct(const void *wim_filename_or_fd, int open_flags,
+                     WIMStruct **wim_ret, wimlib_progress_func_t progress_func)
+{
+       WIMStruct *wim;
+       int ret;
 
-       /* Find the images in the WIM by searching the lookup table. */
-       ret = for_lookup_table_entry(w->lookup_table,
-                                    append_metadata_resource_entry, w);
+       wimlib_global_init(WIMLIB_INIT_FLAG_ASSUME_UTF8);
 
-       if (ret != 0)
-               return ret;
+       ret = WIMLIB_ERR_INVALID_PARAM;
+       if (!wim_ret)
+               goto out;
 
-       /* Make sure all the expected images were found.  (We already have
-        * returned WIMLIB_ERR_IMAGE_COUNT if *extra* images were found) */
-       if (w->current_image != w->hdr.image_count &&
-           w->hdr.part_number == 1)
-       {
-               ERROR("Only found %d images in WIM, but expected %u",
-                     w->current_image, w->hdr.image_count);
-               return WIMLIB_ERR_IMAGE_COUNT;
-       }
+       ret = WIMLIB_ERR_NOMEM;
+       wim = new_wim_struct();
+       if (!wim)
+               goto out;
 
-       /* Sort images by the position of their metadata resources.  I'm
-        * assuming that is what determines the other of the images in the WIM
-        * file, rather than their order in the lookup table, which is random
-        * because of hashing. */
-       qsort(w->image_metadata, w->current_image,
-             sizeof(struct wim_image_metadata), sort_image_metadata_by_position);
+       ret = begin_read(wim, wim_filename_or_fd, open_flags, progress_func);
+       if (ret)
+               goto out_wimlib_free;
 
-       w->current_image = WIMLIB_NO_IMAGE;
+       ret = 0;
+       *wim_ret = wim;
+       goto out;
+out_wimlib_free:
+       wimlib_free(wim);
+out:
+       return ret;
+}
 
-       /* Read the XML data. */
-       ret = read_xml_data(w->fp, &w->hdr.xml_res_entry,
-                           &w->xml_data, &w->wim_info);
+/* API function documented in wimlib.h  */
+WIMLIBAPI int
+wimlib_open_wim(const tchar *wimfile, int open_flags,
+               WIMStruct **wim_ret, wimlib_progress_func_t progress_func)
+{
+       open_flags &= WIMLIB_OPEN_MASK_PUBLIC;
+       return open_wim_as_WIMStruct(wimfile, open_flags, wim_ret,
+                                    progress_func);
+}
 
-       if (ret != 0)
-               return ret;
+void
+destroy_image_metadata(struct wim_image_metadata *imd,
+                      struct wim_lookup_table *table,
+                      bool free_metadata_lte)
+{
+       free_dentry_tree(imd->root_dentry, table);
+       imd->root_dentry = NULL;
+       free_wim_security_data(imd->security_data);
+       imd->security_data = NULL;
 
-       xml_num_images = wim_info_get_num_images(w->wim_info);
-       if (xml_num_images != w->hdr.image_count) {
-               ERROR("In the file `%"TS"', there are %u <IMAGE> elements "
-                     "in the XML data,", in_wim_path, xml_num_images);
-               ERROR("but %u images in the WIM!  There must be exactly one "
-                     "<IMAGE> element per image.", w->hdr.image_count);
-               return WIMLIB_ERR_IMAGE_COUNT;
+       if (free_metadata_lte) {
+               free_lookup_table_entry(imd->metadata_lte);
+               imd->metadata_lte = NULL;
+       }
+       if (!table) {
+               struct wim_lookup_table_entry *lte, *tmp;
+               list_for_each_entry_safe(lte, tmp, &imd->unhashed_streams, unhashed_list)
+                       free_lookup_table_entry(lte);
+       }
+       INIT_LIST_HEAD(&imd->unhashed_streams);
+       INIT_LIST_HEAD(&imd->inode_list);
+#ifdef WITH_NTFS_3G
+       if (imd->ntfs_vol) {
+               do_ntfs_umount(imd->ntfs_vol);
+               imd->ntfs_vol = NULL;
        }
+#endif
+}
 
-       DEBUG("Done beginning read of WIM file `%"TS"'.", in_wim_path);
-       return 0;
+void
+put_image_metadata(struct wim_image_metadata *imd,
+                  struct wim_lookup_table *table)
+{
+       if (imd && --imd->refcnt == 0) {
+               destroy_image_metadata(imd, table, true);
+               FREE(imd);
+       }
 }
 
-/*
- * Opens a WIM file and creates a WIMStruct for it.
- */
-WIMLIBAPI int
-wimlib_open_wim(const tchar *wim_file, int open_flags,
-               WIMStruct **w_ret,
-               wimlib_progress_func_t progress_func)
+/* Appends the specified image metadata structure to the array of image metadata
+ * for a WIM, and increments the image count. */
+int
+append_image_metadata(WIMStruct *wim, struct wim_image_metadata *imd)
 {
-       WIMStruct *w;
-       int ret;
+       struct wim_image_metadata **imd_array;
 
-       if (!wim_file || !w_ret)
-               return WIMLIB_ERR_INVALID_PARAM;
+       DEBUG("Reallocating image metadata array for image_count = %u",
+             wim->hdr.image_count + 1);
+       imd_array = REALLOC(wim->image_metadata,
+                           sizeof(wim->image_metadata[0]) * (wim->hdr.image_count + 1));
 
-       w = new_wim_struct();
-       if (!w)
+       if (!imd_array)
                return WIMLIB_ERR_NOMEM;
+       wim->image_metadata = imd_array;
+       imd_array[wim->hdr.image_count++] = imd;
+       return 0;
+}
 
-       ret = begin_read(w, wim_file, open_flags, progress_func);
-       if (ret == 0)
-               *w_ret = w;
-       else
-               wimlib_free(w);
-       return ret;
+
+struct wim_image_metadata *
+new_image_metadata(void)
+{
+       struct wim_image_metadata *imd;
+
+       imd = CALLOC(1, sizeof(*imd));
+       if (imd) {
+               imd->refcnt = 1;
+               INIT_LIST_HEAD(&imd->inode_list);
+               INIT_LIST_HEAD(&imd->unhashed_streams);
+               DEBUG("Created new image metadata (refcnt=1)");
+       } else {
+               ERROR_WITH_ERRNO("Failed to allocate new image metadata structure");
+       }
+       return imd;
 }
 
-void
-destroy_image_metadata(struct wim_image_metadata *imd,
-                      struct wim_lookup_table *table)
+struct wim_image_metadata **
+new_image_metadata_array(unsigned num_images)
 {
-       free_dentry_tree(imd->root_dentry, table);
-       free_security_data(imd->security_data);
+       struct wim_image_metadata **imd_array;
 
-       /* Get rid of the lookup table entry for this image's metadata resource
-        * */
-       if (table) {
-               lookup_table_unlink(table, imd->metadata_lte);
-               free_lookup_table_entry(imd->metadata_lte);
+       DEBUG("Creating new image metadata array for %u images",
+             num_images);
+
+       imd_array = CALLOC(num_images, sizeof(imd_array[0]));
+
+       if (!imd_array) {
+               ERROR("Failed to allocate memory for %u image metadata structures",
+                     num_images);
+               return NULL;
+       }
+       for (unsigned i = 0; i < num_images; i++) {
+               imd_array[i] = new_image_metadata();
+               if (!imd_array[i]) {
+                       for (unsigned j = 0; j < i; j++)
+                               put_image_metadata(imd_array[j], NULL);
+                       FREE(imd_array);
+                       return NULL;
+               }
        }
+       return imd_array;
 }
 
-/* Frees the memory for the WIMStruct, including all internal memory; also
- * closes all files associated with the WIMStruct.  */
-WIMLIBAPI void
-wimlib_free(WIMStruct *w)
+/* Checksum all streams that are unhashed (other than the metadata streams),
+ * merging them into the lookup table as needed.  This is a no-op unless the
+ * library has previously used to add or mount an image using the same
+ * WIMStruct. */
+int
+wim_checksum_unhashed_streams(WIMStruct *wim)
+{
+       int ret;
+
+       if (!wim_has_metadata(wim))
+               return 0;
+       for (int i = 0; i < wim->hdr.image_count; i++) {
+               struct wim_lookup_table_entry *lte, *tmp;
+               struct wim_image_metadata *imd = wim->image_metadata[i];
+               image_for_each_unhashed_stream_safe(lte, tmp, imd) {
+                       ret = hash_unhashed_stream(lte, wim->lookup_table, NULL);
+                       if (ret)
+                               return ret;
+               }
+       }
+       return 0;
+}
+
+/*
+ * can_modify_wim - Check if a given WIM is writeable.  This is only the case if
+ * it meets the following three conditions:
+ *
+ * 1. Write access is allowed to the underlying file (if any) at the filesystem level.
+ * 2. The WIM is not part of a spanned set.
+ * 3. The WIM_HDR_FLAG_READONLY flag is not set in the WIM header.
+ *
+ * Return value is 0 if writable; WIMLIB_ERR_WIM_IS_READONLY otherwise.
+ */
+int
+can_modify_wim(WIMStruct *wim)
 {
-       DEBUG("Freeing WIMStruct");
+       if (wim->filename) {
+               if (taccess(wim->filename, W_OK)) {
+                       ERROR_WITH_ERRNO("Can't modify \"%"TS"\"", wim->filename);
+                       return WIMLIB_ERR_WIM_IS_READONLY;
+               }
+       }
+       if (wim->hdr.total_parts != 1) {
+               ERROR("Cannot modify \"%"TS"\": is part of a split WIM",
+                     wim->filename);
+               return WIMLIB_ERR_WIM_IS_READONLY;
+       }
+       if (wim->hdr.flags & WIM_HDR_FLAG_READONLY) {
+               ERROR("Cannot modify \"%"TS"\": is marked read-only",
+                     wim->filename);
+               return WIMLIB_ERR_WIM_IS_READONLY;
+       }
+       return 0;
+}
 
-       if (!w)
+/*
+ * can_delete_from_wim - Check if files or images can be deleted from a given
+ * WIM file.
+ *
+ * This theoretically should be exactly the same as can_modify_wim(), but
+ * unfortunately, due to bugs in Microsoft's software that generate incorrect
+ * reference counts for some WIM resources, we need to run expensive
+ * verifications to make sure the reference counts are correct on all WIM
+ * resources.  Otherwise we might delete a WIM resource whose reference count
+ * has fallen to 0, but is actually still referenced somewhere.
+ */
+int
+can_delete_from_wim(WIMStruct *wim)
+{
+       int ret;
+
+       ret = can_modify_wim(wim);
+       if (ret)
+               return ret;
+       if (!wim->refcnts_ok)
+               wim_recalculate_refcnts(wim);
+       return 0;
+}
+
+/* API function documented in wimlib.h  */
+WIMLIBAPI void
+wimlib_free(WIMStruct *wim)
+{
+       if (!wim)
                return;
-       if (w->fp)
-               fclose(w->fp);
-       if (w->out_fp)
-               fclose(w->out_fp);
-
-#ifdef WITH_FUSE
-       if (w->fp_tab) {
-               for (size_t i = 0; i < w->num_allocated_fps; i++)
-                       if (w->fp_tab[i])
-                               fclose(w->fp_tab[i]);
-               FREE(w->fp_tab);
-       }
-       pthread_mutex_destroy(&w->fp_tab_mutex);
-#endif
 
-       free_lookup_table(w->lookup_table);
+       DEBUG("Freeing WIMStruct (filename=\"%"TS"\", image_count=%u)",
+             wim->filename, wim->hdr.image_count);
+
+       while (!list_empty(&wim->subwims)) {
+               WIMStruct *subwim;
 
-       FREE(w->filename);
-       FREE(w->xml_data);
-       free_wim_info(w->wim_info);
-       if (w->image_metadata) {
-               for (unsigned i = 0; i < w->hdr.image_count; i++)
-                       destroy_image_metadata(&w->image_metadata[i], NULL);
-               FREE(w->image_metadata);
+               subwim = list_entry(wim->subwims.next, WIMStruct, subwim_node);
+               list_del(&subwim->subwim_node);
+               DEBUG("Freeing subwim.");
+               wimlib_free(subwim);
        }
-#ifdef WITH_NTFS_3G
-       if (w->ntfs_vol) {
-               DEBUG("Unmounting NTFS volume");
-               ntfs_umount(w->ntfs_vol, FALSE);
+
+       if (filedes_valid(&wim->in_fd))
+               filedes_close(&wim->in_fd);
+       if (filedes_valid(&wim->out_fd))
+               filedes_close(&wim->out_fd);
+
+
+       free_lookup_table(wim->lookup_table);
+
+       FREE(wim->filename);
+       free_wim_info(wim->wim_info);
+       if (wim->image_metadata) {
+               for (unsigned i = 0; i < wim->hdr.image_count; i++)
+                       put_image_metadata(wim->image_metadata[i], NULL);
+               FREE(wim->image_metadata);
        }
-#endif
-       FREE(w);
-       DEBUG("Freed WIMStruct");
+       FREE(wim);
 }
 
 static bool
-test_locale_ctype_utf8()
+test_locale_ctype_utf8(void)
 {
+#ifdef __WIN32__
+       return false;
+#else
        char *ctype = nl_langinfo(CODESET);
 
-       return (strstr(ctype, "UTF-8") == 0 ||
-               strstr(ctype, "UTF8") == 0 ||
-               strstr(ctype, "utf8") == 0 ||
-               strstr(ctype, "utf-8") == 0);
+       return (!strstr(ctype, "UTF-8") ||
+               !strstr(ctype, "UTF8") ||
+               !strstr(ctype, "utf8") ||
+               !strstr(ctype, "utf-8"));
+#endif
 }
 
-/* Get global memory allocations out of the way.  Not strictly necessary in
- * single-threaded programs like 'imagex'. */
+/* API function documented in wimlib.h  */
 WIMLIBAPI int
-wimlib_global_init()
+wimlib_global_init(int init_flags)
 {
+       static bool already_inited = false;
+       int ret;
+
+       if (already_inited)
+               return 0;
        libxml_global_init();
-#ifdef WITH_NTFS_3G
-       libntfs3g_global_init();
-#endif
-       wimlib_mbs_is_utf8 = test_locale_ctype_utf8();
+       if (!(init_flags & WIMLIB_INIT_FLAG_ASSUME_UTF8)) {
+               wimlib_mbs_is_utf8 = test_locale_ctype_utf8();
+       #ifdef WITH_NTFS_3G
+               if (!wimlib_mbs_is_utf8)
+                       libntfs3g_global_init();
+       #endif
+       }
 #ifdef __WIN32__
-       win32_global_init();
+       ret = win32_global_init(init_flags);
+       if (ret)
+               return ret;
+#else
+       ret = 0;
 #endif
-       return 0;
+       already_inited = true;
+       return ret;
 }
 
-/* Free global memory allocations.  Not strictly necessary if the process using
- * wimlib is just about to exit (as is the case for 'imagex'). */
+/* API function documented in wimlib.h  */
 WIMLIBAPI void
-wimlib_global_cleanup()
+wimlib_global_cleanup(void)
 {
        libxml_global_cleanup();
        iconv_global_cleanup();