+ return match_pattern_list(path, path_nchars, pats);
+}
+
+/* Returns %true if the specified absolute path to a file in the WIM image can
+ * be subject to external backing when extracted. Otherwise returns %false. */
+static bool
+can_externally_back_path(const wchar_t *path, size_t path_nchars,
+ const struct win32_apply_ctx *ctx)
+{
+ if (in_prepopulate_list(path, path_nchars, ctx))
+ return false;
+
+ /* Since we attempt to modify the SYSTEM registry after it's extracted
+ * (see end_wimboot_extraction()), it can't be extracted as externally
+ * backed. This extends to associated files such as SYSTEM.LOG that
+ * also must be writable in order to write to the registry. Normally,
+ * SYSTEM is in [PrepopulateList], and the SYSTEM.* files match patterns
+ * in [ExclusionList] and therefore are not captured in the WIM at all.
+ * However, a WIM that wasn't specifically captured in "WIMBoot mode"
+ * may contain SYSTEM.* files. So to make things "just work", hard-code
+ * the pattern. */
+ if (match_path(path, path_nchars, L"\\Windows\\System32\\config\\SYSTEM*",
+ OS_PREFERRED_PATH_SEPARATOR, false))
+ return false;
+
+ return true;
+}
+
+#define WIM_BACKING_NOT_ENABLED -1
+#define WIM_BACKING_NOT_POSSIBLE -2
+#define WIM_BACKING_EXCLUDED -3
+
+static int
+will_externally_back_inode(struct wim_inode *inode, struct win32_apply_ctx *ctx,
+ const struct wim_dentry **excluded_dentry_ret)
+{
+ struct list_head *next;
+ struct wim_dentry *dentry;
+ struct wim_lookup_table_entry *stream;
+ int ret;
+
+ if (inode->i_can_externally_back)
+ return 0;
+
+ /* This may do redundant checks because the cached value
+ * i_can_externally_back is 2-state (as opposed to 3-state:
+ * unknown/no/yes). But most files can be externally backed, so this
+ * way is fine. */
+
+ if (inode->i_attributes & (FILE_ATTRIBUTE_DIRECTORY |
+ FILE_ATTRIBUTE_REPARSE_POINT |
+ FILE_ATTRIBUTE_ENCRYPTED))
+ return WIM_BACKING_NOT_POSSIBLE;
+
+ stream = inode_unnamed_lte_resolved(inode);
+
+ if (!stream ||
+ stream->resource_location != RESOURCE_IN_WIM ||
+ stream->rspec->wim != ctx->common.wim ||
+ stream->size != stream->rspec->uncompressed_size)
+ return WIM_BACKING_NOT_POSSIBLE;
+
+ /*
+ * We need to check the patterns in [PrepopulateList] against every name
+ * of the inode, in case any of them match.
+ */
+ next = inode->i_extraction_aliases.next;
+ do {
+ dentry = list_entry(next, struct wim_dentry,
+ d_extraction_alias_node);
+
+ ret = calculate_dentry_full_path(dentry);
+ if (ret)
+ return ret;
+
+ if (!can_externally_back_path(dentry->_full_path,
+ wcslen(dentry->_full_path), ctx))
+ {
+ if (excluded_dentry_ret)
+ *excluded_dentry_ret = dentry;
+ return WIM_BACKING_EXCLUDED;
+ }
+ next = next->next;
+ } while (next != &inode->i_extraction_aliases);
+
+ inode->i_can_externally_back = 1;
+ return 0;
+}
+
+/*
+ * Determines if the unnamed data stream of a file will be created as an
+ * external backing, as opposed to a standard extraction.
+ */
+static int
+win32_will_externally_back(struct wim_dentry *dentry, struct apply_ctx *_ctx)
+{
+ struct win32_apply_ctx *ctx = (struct win32_apply_ctx *)_ctx;
+
+ if (!(ctx->common.extract_flags & WIMLIB_EXTRACT_FLAG_WIMBOOT))
+ return WIM_BACKING_NOT_ENABLED;
+
+ if (!ctx->wimboot.tried_to_load_prepopulate_list)
+ if (load_prepopulate_pats(ctx) == WIMLIB_ERR_NOMEM)
+ return WIMLIB_ERR_NOMEM;
+
+ return will_externally_back_inode(dentry->d_inode, ctx, NULL);
+}
+
+static int
+set_external_backing(HANDLE h, struct wim_inode *inode, struct win32_apply_ctx *ctx)
+{
+ int ret;
+ const struct wim_dentry *excluded_dentry;
+
+ ret = will_externally_back_inode(inode, ctx, &excluded_dentry);
+ if (ret > 0) /* Error. */
+ return ret;
+
+ if (ret < 0 && ret != WIM_BACKING_EXCLUDED)
+ return 0; /* Not externally backing, other than due to exclusion. */
+
+ if (unlikely(ret == WIM_BACKING_EXCLUDED)) {
+ /* Not externally backing due to exclusion. */
+ union wimlib_progress_info info;
+
+ build_extraction_path(excluded_dentry, ctx);
+
+ info.wimboot_exclude.path_in_wim = excluded_dentry->_full_path;
+ info.wimboot_exclude.extraction_path = current_path(ctx);
+
+ return call_progress(ctx->common.progfunc,
+ WIMLIB_PROGRESS_MSG_WIMBOOT_EXCLUDE,
+ &info, ctx->common.progctx);
+ } else {
+ /* Externally backing. */
+ if (unlikely(!wimboot_set_pointer(h,
+ inode_unnamed_lte_resolved(inode),
+ ctx->wimboot.data_source_id,
+ ctx->wimboot.wim_lookup_table_hash,
+ ctx->wimboot.wof_running)))
+ {
+ const DWORD err = GetLastError();
+
+ build_extraction_path(inode_first_extraction_dentry(inode), ctx);
+ win32_error(err, L"\"%ls\": Couldn't set WIMBoot pointer data",
+ current_path(ctx));
+ return WIMLIB_ERR_WIMBOOT;
+ }
+ return 0;
+ }