X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Fwimlib.h;h=0618ff3801114645820b0584e99afeb6eb9dca88;hp=5ed6c684c7245cc5b7b0ad3d35a0669efc72879d;hb=5cdd60306facd14cc9dcc24471386451294ca73c;hpb=26fdf3f709adf52521e1cf962095987a3e0e2e00

diff --git a/src/wimlib.h b/src/wimlib.h
index 5ed6c684..0618ff38 100644
--- a/src/wimlib.h
+++ b/src/wimlib.h
@@ -4,7 +4,7 @@
  * External header for wimlib.
  */
 
-/* 
+/*
  * Copyright (C) 2012 Eric Biggers
  *
  * This file is part of wimlib, a library for working with WIM files.
@@ -57,7 +57,7 @@
  * A WIM file may be either stand-alone or split into multiple parts.
  *
  * \section winpe Windows PE
- * 
+ *
  * A major use for this library is to create customized images of Windows PE, the
  * Windows Preinstallation Environment, without having to rely on Windows.  Windows
  * PE is a lightweight version of Windows that can run entirely from memory and can
@@ -108,10 +108,9 @@
  * that this is for convenience only, and some errors can occur without a
  * message being printed.
  *
- * wimlib is thread-safe as long as different ::WIMStruct's are used, with the
- * following exceptions:  wimlib_set_print_errors() and
- * wimlib_set_memory_allocator() apply globally, and wimlib_mount() can only be
- * used by one ::WIMStruct at a time.
+ * wimlib is thread-safe as long as different ::WIMStruct's are used, except for
+ * the fact that wimlib_set_print_errors() and wimlib_set_memory_allocator()
+ * both apply globally.
  *
  * To open an existing WIM, use wimlib_open_wim().
  *
@@ -142,14 +141,18 @@
  *
  * After creating or modifying a WIM file, you can write it to a file using
  * wimlib_write().  Alternatively,  if the WIM was originally read from a file,
- * you can use wimlib_overwrite() to overwrite the original file.  In some
- * cases, wimlib_overwrite_xml_and_header() can be used instead.
+ * you can use wimlib_overwrite() to overwrite the original file.
+ *
+ * Please not: merely by calling wimlib_add_image() or many of the other
+ * functions in this library that operate on ::WIMStruct's, you are @b not
+ * modifing the WIM file on disk.  Changes are not saved until you explicitly
+ * call wimlib_write() or wimlib_overwrite().
  *
  * After you are done with the WIM file, use wimlib_free() to free all memory
  * associated with a ::WIMStruct and close all files associated with it.
  *
- * To see an example of how to use wimlib, see the file
- * @c programs/imagex.c in wimlib's source tree.
+ * To see an example of how to use wimlib, see the file @c programs/imagex.c in
+ * wimlib's source tree.
  *
  * wimlib supports custom memory allocators; use wimlib_set_memory_allocator()
  * for this.  However, if wimlib calls into @c libntfs-3g, the custom memory
@@ -160,7 +163,7 @@
  * wimlib comes with the <b>imagex</b> program, which is documented in man pages.
  *
  * \section mkwinpeimg mkwinpeimg
- * 
+ *
  * wimlib comes with the <b>mkwinpeimg</b> script, which is documented in a man
  * page.
  *
@@ -211,8 +214,8 @@
 #include <stdbool.h>
 
 #ifndef _WIMLIB_INTERNAL_H
-/** 
- * Opaque structure that represents a WIM file. 
+/**
+ * Opaque structure that represents a WIM file.
  */
 typedef struct WIMStruct WIMStruct;
 #endif
@@ -252,7 +255,7 @@ enum wim_compression_type {
  * alternate file stream name. */
 #define WIMLIB_MOUNT_FLAG_STREAM_INTERFACE_WINDOWS	0x00000040
 
-/** Include an integrity table in the new WIM being written during the unmount. 
+/** Include an integrity table in the new WIM being written during the unmount.
  * Ignored for read-only mounts. */
 #define WIMLIB_UNMOUNT_FLAG_CHECK_INTEGRITY	0x00000001
 
@@ -263,12 +266,33 @@ enum wim_compression_type {
 /** Include an integrity table in the new WIM file. */
 #define WIMLIB_WRITE_FLAG_CHECK_INTEGRITY	0x00000001
 
-/** Print progress information when writing the integrity table. */
+/** Print progress information when writing streams and when writing the
+ * integrity table. */
 #define WIMLIB_WRITE_FLAG_SHOW_PROGRESS		0x00000002
 
 /** Print file paths as we write then */
 #define WIMLIB_WRITE_FLAG_VERBOSE		0x00000004
 
+/** Call fsync() when the WIM file is closed */
+#define WIMLIB_WRITE_FLAG_FSYNC			0x00000008
+
+/** Re-build the entire WIM file rather than appending data to it, if possible.
+ * (Applies to wimlib_overwrite(), not wimlib_write()). */
+#define WIMLIB_WRITE_FLAG_REBUILD		0x00000010
+
+/** Do not copy compressed resources between WIMs if the compression type is the
+ * same.  Instead, recompress them. */
+#define WIMLIB_WRITE_FLAG_RECOMPRESS		0x00000020
+
+/** Specifying this flag overrides the default behavior of wimlib_overwrite()
+ * after one or more calls to wimlib_delete_image(), which is to rebuild the
+ * entire WIM.  If you specifiy this flag to wimlib_overwrite() instead, only
+ * minimal changes to correctly remove the image from the WIM will be taken.  In
+ * particular, all streams will be left alone, even if they are no longer
+ * references.  This is probably not what you want, because almost no space will
+ * be spaced by deleting an image in this way. */
+#define WIMLIB_WRITE_FLAG_SOFT_DELETE		0x00000040
+
 /** Mark the image being added as the bootable image of the WIM. */
 #define WIMLIB_ADD_IMAGE_FLAG_BOOT		0x00000001
 
@@ -279,6 +303,9 @@ enum wim_compression_type {
 /** Follow symlinks; archive and dump the files they point to. */
 #define WIMLIB_ADD_IMAGE_FLAG_DEREFERENCE	0x00000004
 
+/** Show progress information when scanning a directory tree */
+#define WIMLIB_ADD_IMAGE_FLAG_SHOW_PROGRESS	0x00000008
+
 /** See documentation for wimlib_export_image(). */
 #define WIMLIB_EXPORT_FLAG_BOOT			0x00000001
 
@@ -304,6 +331,12 @@ enum wim_compression_type {
 /** Print the name of each file as it is extracted from the WIM image. */
 #define WIMLIB_EXTRACT_FLAG_VERBOSE		0x00000008
 
+/** Read the WIM file sequentially while extracting the image. */
+#define WIMLIB_EXTRACT_FLAG_SEQUENTIAL		0x00000010
+
+/** Print progress information while extracting the image. */
+#define WIMLIB_EXTRACT_FLAG_SHOW_PROGRESS	0x00000020
+
 /**
  * Possible values of the error code returned by many functions in wimlib.
  *
@@ -346,6 +379,8 @@ enum wimlib_error_code {
 	WIMLIB_ERR_READLINK,
 	WIMLIB_ERR_READ,
 	WIMLIB_ERR_RENAME,
+	WIMLIB_ERR_REOPEN,
+	WIMLIB_ERR_RESOURCE_ORDER,
 	WIMLIB_ERR_SPECIAL_FILE,
 	WIMLIB_ERR_SPLIT_INVALID,
 	WIMLIB_ERR_SPLIT_UNSUPPORTED,
@@ -390,7 +425,7 @@ enum wimlib_error_code {
  * @param config_len
  * 	Length of the string @a config in bytes.  Ignored if @a config is @c
  * 	NULL.
- * 	
+ *
  * @param flags
  * 	Bitwise OR of flags prefixed with WIMLIB_ADD_IMAGE_FLAG.  If
  * 	::WIMLIB_ADD_IMAGE_FLAG_BOOT is specified, the image in @a wim that is
@@ -399,15 +434,17 @@ enum wimlib_error_code {
  * 	printed as it is scanned or captured.  If
  * 	::WIMLIB_ADD_IMAGE_FLAG_DEREFERENCE is specified, the files or
  * 	directories pointed to by symbolic links are archived rather than the
- * 	symbolic links themselves.
+ * 	symbolic links themselves.  If ::WIMLIB_ADD_IMAGE_FLAG_SHOW_PROGRESS is
+ * 	specified, progress information will be printed (distinct from the
+ * 	verbose information).
  *
  * @return 0 on success; nonzero on error.  On error, changes to @a wim are
  * discarded so that it appears to be in the same state as when this function
  * was called.
  *
- * @retval ::WIMLIB_ERR_IMAGE_NAME_COLLISION 
+ * @retval ::WIMLIB_ERR_IMAGE_NAME_COLLISION
  * 	There is already an image named @a name in @a w.
- * @retval ::WIMLIB_ERR_INVALID_PARAM 
+ * @retval ::WIMLIB_ERR_INVALID_PARAM
  * 	@a dir was @c NULL, @a name was @c NULL, or @a name was the empty string.
  * @retval ::WIMLIB_ERR_NOMEM
  * 	Failed to allocate needed memory.
@@ -428,7 +465,7 @@ enum wimlib_error_code {
  * 	@a wim is part of a split WIM.  Adding an image to a split WIM is
  * 	unsupported.
  */
-extern int wimlib_add_image(WIMStruct *wim, const char *dir, 
+extern int wimlib_add_image(WIMStruct *wim, const char *dir,
 			    const char *name, const char *config,
 			    size_t config_len, int flags);
 
@@ -459,10 +496,10 @@ extern int wimlib_apply_image_to_ntfs_volume(WIMStruct *wim, int image,
 					     WIMStruct **additional_swms,
 					     unsigned num_additional_swms);
 
-/** 
+/**
  * Creates a WIMStruct for a new WIM file.
  *
- * @param ctype 
+ * @param ctype
  * 	The type of compression to be used in the new WIM file.  Must be
  * 	::WIM_COMPRESSION_TYPE_NONE, ::WIM_COMPRESSION_TYPE_LZX, or
  * 	::WIM_COMPRESSION_TYPE_XPRESS.
@@ -507,9 +544,9 @@ extern int wimlib_create_new_wim(int ctype, WIMStruct **wim_ret);
  * @retval ::WIMLIB_ERR_INVALID_IMAGE
  * 	@a image does not exist in the WIM and is not ::WIM_ALL_IMAGES.
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_SIZE
- *	The metadata resource for @a image in the WIM is invalid.	
+ *	The metadata resource for @a image in the WIM is invalid.
  * @retval ::WIMLIB_ERR_INVALID_SECURITY_DATA
- *	The security data for @a image in the WIM is invalid.	
+ *	The security data for @a image in the WIM is invalid.
  * @retval ::WIMLIB_ERR_NOMEM
  * 	Failed to allocate needed memory.
  * @retval ::WIMLIB_ERR_READ
@@ -590,7 +627,7 @@ extern int wimlib_delete_image(WIMStruct *wim, int image);
  * @retval ::WIMLIB_ERR_IMAGE_NAME_COLLISION
  * 	One or more of the names being given to an exported image was already in
  * 	use in the destination WIM.
- * @retval ::WIMLIB_ERR_INVALID_DENTRY 
+ * @retval ::WIMLIB_ERR_INVALID_DENTRY
  * 	A directory entry in the metadata resource for @a src_image in @a
  * 	src_wim is invalid.
  * @retval ::WIMLIB_ERR_INVALID_IMAGE
@@ -603,10 +640,10 @@ extern int wimlib_delete_image(WIMStruct *wim, int image);
  * 	::WIM_ALL_IMAGES, and @a src_wim contains multiple images; or @a src_wim
  * 	or @a dest_wim was @c NULL.
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_SIZE
- *	The metadata resource for @a src_image in @a src_wim is invalid.	
+ *	The metadata resource for @a src_image in @a src_wim is invalid.
  * @retval ::WIMLIB_ERR_INVALID_SECURITY_DATA
- *	The security data for @a src_image in @a src_wim is invalid.	
- * @retval ::WIMLIB_ERR_NOMEM 
+ *	The security data for @a src_image in @a src_wim is invalid.
+ * @retval ::WIMLIB_ERR_NOMEM
  * 	Failed to allocate needed memory.
  * @retval ::WIMLIB_ERR_READ
  * 	Could not read the metadata resource for @a src_image from @a src_wim.
@@ -619,8 +656,8 @@ extern int wimlib_delete_image(WIMStruct *wim, int image);
  * 	@a dest_wim is part of a split WIM.  Exporting an image to a split WIM
  * 	is unsupported.
  */
-extern int wimlib_export_image(WIMStruct *src_wim, int src_image, 
-			       WIMStruct *dest_wim, const char *dest_name, 
+extern int wimlib_export_image(WIMStruct *src_wim, int src_image,
+			       WIMStruct *dest_wim, const char *dest_name,
 			       const char *dest_description, int flags,
 			       WIMStruct **additional_swms,
 			       unsigned num_additional_swms);
@@ -667,16 +704,16 @@ extern int wimlib_export_image(WIMStruct *src_wim, int src_image,
  * @retval ::WIMLIB_ERR_DECOMPRESSION
  * 	Could not decompress a resource (file or metadata) for @a image in @a
  * 	wim.
- * @retval ::WIMLIB_ERR_INVALID_DENTRY 
+ * @retval ::WIMLIB_ERR_INVALID_DENTRY
  * 	A directory entry in the metadata resource for @a image in @a wim is
  * 	invalid.
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_HASH
  * 	The SHA1 message digest of an extracted stream did not match the SHA1
  * 	message digest given in the WIM file.
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_SIZE
- *	A resource (file or metadata) for @a image in @a wim is invalid.	
+ *	A resource (file or metadata) for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_INVALID_SECURITY_DATA
- *	The security data for @a image in @a wim is invalid.	
+ *	The security data for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_LINK
  * 	Failed to create a symbolic link or a hard link.
  * @retval ::WIMLIB_ERR_MKDIR
@@ -708,8 +745,8 @@ extern int wimlib_extract_image(WIMStruct *wim, int image,
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * @param fp 
- * 	@c stdout, or a FILE* opened for writing, to extract the data to.  
+ * @param fp
+ * 	@c stdout, or a FILE* opened for writing, to extract the data to.
  *
  * @return 0 on success; nonzero on error.
  * @retval ::WIMLIB_ERR_WRITE
@@ -719,7 +756,7 @@ extern int wimlib_extract_xml_data(WIMStruct *wim, FILE *fp);
 
 /**
  * Frees all memory allocated for a WIMStruct and closes all files associated
- * with it. 
+ * with it.
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
@@ -733,7 +770,7 @@ extern void wimlib_free(WIMStruct *wim);
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * 
+ *
  * @return
  * 	0 if no image is marked as bootable, or the number of the image marked
  * 	as bootable (numbered starting at 1).
@@ -745,7 +782,7 @@ extern int wimlib_get_boot_idx(const WIMStruct *wim);
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file
- * 
+ *
  * @return
  * 	::WIM_COMPRESSION_TYPE_NONE, ::WIM_COMPRESSION_TYPE_LZX, or
  * 	::WIM_COMPRESSION_TYPE_XPRESS.
@@ -819,7 +856,7 @@ extern const char *wimlib_get_image_name(const WIMStruct *wim, int image);
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.  It may be either a
  * 	standalone WIM or a split WIM part.
- * 
+ *
  * @return
  * 	The number of images contained in the WIM file.
  */
@@ -834,7 +871,7 @@ extern int wimlib_get_num_images(const WIMStruct *wim);
  * 	If non-@c NULL, the total number of parts in the split WIM (1 for
  * 	non-split WIMs) is written to this location.
  *
- * @return 
+ * @return
  * 	The part number of the WIM (1 for non-split WIMs)
  */
 extern int wimlib_get_part_number(const WIMStruct *wim, int *total_parts_ret);
@@ -892,7 +929,10 @@ extern bool wimlib_image_name_in_use(const WIMStruct *wim, const char *name);
  * 	An error occurred when trying to write data to the new WIM at @a output_path.
  *
  * Note that this function merely copies the resources, so it will not check to
- * see if the resources, including the metadata resource, are valid or not.
+ * see if the resources, including the metadata resources, are valid or not.
+ *
+ * Also, after this function is called, the only function that may be called on
+ * the ::WIMStruct's in the @a swms array is wimlib_free().
  */
 extern int wimlib_join(const char **swms, unsigned num_swms,
 		       const char *output_path, int flags);
@@ -905,11 +945,16 @@ extern int wimlib_join(const char **swms, unsigned num_swms,
  * If the mount is read-write, modifications to the WIM are staged in a staging
  * directory.
  *
- * wimlib_mount() currently cannot be used with multiple ::WIMStruct's without
- * intervening wimlib_unmount()s.
+ * wimlib_mount() may be called from multiple threads without intervening calls
+ * to wimlib_unmount(), provided that different ::WIMStruct's are used.  (This
+ * was not the case for versions of this library 1.0.3 and earlier.)
  *
  * wimlib_mount() cannot be used on an image that was exported with
- * wimlib_export() while the dentry trees for both images are still in memory.
+ * wimlib_export_image() while the dentry trees for both images are still in
+ * memory.  In addition, wimlib_mount() may not be used to mount an image that
+ * has just been added with wimlib_add_image() or
+ * wimlib_add_image_from_ntfs_volume(), unless the WIM has been written and read
+ * into a new ::WIMStruct.
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for the WIM file to be mounted.
@@ -942,18 +987,19 @@ extern int wimlib_join(const char **swms, unsigned num_swms,
  * 	Could not decompress the metadata resource for @a image in @a wim.
  * @retval ::WIMLIB_ERR_FUSE
  * 	A non-zero status was returned by @c fuse_main().
- * @retval ::WIMLIB_ERR_INVALID_DENTRY 
+ * @retval ::WIMLIB_ERR_INVALID_DENTRY
  * 	A directory entry in the metadata resource for @a image in @a wim is
  * 	invalid.
  * @retval ::WIMLIB_ERR_INVALID_IMAGE
  * 	@a image does not specify an existing, single image in @a wim.
  * @retval ::WIMLIB_ERR_INVALID_PARAM
  * 	@a image is shared among multiple ::WIMStruct's as a result of a call to
- * 	wimlib_export().
+ * 	wimlib_export_image(), or @a image has been added with
+ * 	wimlib_add_image() or wimlib_add_image_from_ntfs_volume().
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_SIZE
- *	The metadata resource for @a image in @a wim is invalid.	
+ *	The metadata resource for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_INVALID_SECURITY_DATA
- *	The security data for @a image in @a wim is invalid.	
+ *	The security data for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_MKDIR
  * 	::WIMLIB_MOUNT_FLAG_READWRITE was specified in @a flags, but the staging
  * 	directory could not be created.
@@ -980,7 +1026,7 @@ extern int wimlib_mount(WIMStruct *wim, int image, const char *dir, int flags,
 /**
  * Opens a WIM file and creates a ::WIMStruct for it.
  *
- * @param wim_file 
+ * @param wim_file
  * 	The path to the WIM file to open.
  * @param flags
  * 	Bitwise OR of ::WIMLIB_OPEN_FLAG_CHECK_INTEGRITY and/or
@@ -993,7 +1039,7 @@ extern int wimlib_mount(WIMStruct *wim, int image, const char *dir, int flags,
  * 	If ::WIMLIB_OPEN_FLAG_SHOW_PROGRESS is given, progress information will
  * 	be shown if the integrity of the WIM is checked.
  * 	If ::WIMLIB_OPEN_FLAG_SPLIT_OK is given, no error will be issued if the
- * 	WIM is part of a split WIM; otherwise WIMLIB_ERR_SPLIT_UNSUPPORTED is
+ * 	WIM is part of a split WIM; otherwise ::WIMLIB_ERR_SPLIT_UNSUPPORTED is
  * 	returned.  (This flag may be removed in the future, in which case no
  * 	error will be issued when opening a split WIM.)
  *
@@ -1050,26 +1096,49 @@ extern int wimlib_mount(WIMStruct *wim, int image, const char *dir, int flags,
  * @retval ::WIMLIB_ERR_XML
  * 	The XML data for @a wim_file is invalid.
  */
-extern int wimlib_open_wim(const char *wim_file, int flags, 
+extern int wimlib_open_wim(const char *wim_file, int flags,
 			   WIMStruct **wim_ret);
 
 /**
  * Overwrites the file that the WIM was originally read from, with changes made.
  *
- * The new WIM is written to a temporary file and then renamed to the original
- * file after it is has been completely written.  The temporary file currently
- * is made in the same directory as the original WIM file.
- *
- * After this function returns, @a wim must be freed using wimlib_free().  Any
- * further actions on @a wim before doing this are undefined.
+ * There are two ways that a WIM may be overwritten.  The first is to do a full
+ * rebuild: the new WIM is written to a temporary file and then renamed to the
+ * original file after it is has been completely written.  The temporary file
+ * currently is made in the same directory as the original WIM file.  A full
+ * rebuild may take a while, but can be used even if images have been modified
+ * or deleted, will produce a WIM with no holes, and has little chance of
+ * unintentional data loss because the temporary WIM is fsync()ed before being
+ * renamed to the original WIM.
+ *
+ * The second way to overwrite a WIM is by appending to the end of it.  This can
+ * be much faster than a full rebuild, but it only works if the only operations
+ * on the WIM have been to change the header or XML data, or to add new images.
+ * Writing a WIM in this mode begins with writing any new file resources *after*
+ * everything in the old WIM, even though this will leave a hole where the old
+ * lookup table, XML data, and integrity were.  This is done so that the WIM
+ * remains valid even if the operation is aborted mid-write.
+ *
+ * By default, the overwrite mode is chosen based on the past operations
+ * performed on the WIM.  Use the flag ::WIMLIB_WRITE_FLAG_REBUILD to explicitly
+ * request a full rebuild.
+ *
+ * In the temporary-file overwrite mode, no changes are made to the WIM on
+ * failure, and the temporary file is deleted (if possible).  Abnormal
+ * termination of the program will result in the temporary file being orphaned.
+ * In the direct append mode, the WIM is truncated to the original length on
+ * failure, while abnormal termination of the program will result in extra data
+ * appended to the original WIM, but it will still be a valid WIM.
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for the WIM file to write.  There may have
  * 	been in-memory changes made to it, which are then reflected in the
  * 	output file.
- * @param flags 
+ * @param write_flags
  * 	Bitwise OR of ::WIMLIB_WRITE_FLAG_CHECK_INTEGRITY and/or
  * 	::WIMLIB_WRITE_FLAG_SHOW_PROGRESS.
+ * @param num_threads
+ * 	Number of threads to use for compression (see wimlib_write()).
  *
  * @return 0 on success; nonzero on error.  This function may return any value
  * returned by wimlib_write() as well as the following error codes:
@@ -1079,56 +1148,32 @@ extern int wimlib_open_wim(const char *wim_file, int flags,
  * @retval ::WIMLIB_ERR_RENAME
  * 	The temporary file that the WIM was written to could not be renamed to
  * 	the original filename of @a wim.
+ * @retval ::WIMLIB_ERR_REOPEN
+ * 	The WIM was overwritten successfully, but it could not be re-opened
+ * 	read-only.  Therefore, the resources in the WIM can no longer be
+ * 	accessed, so this limits the functions that can be called on @a wim
+ * 	before calling wimlib_free().
  */
-extern int wimlib_overwrite(WIMStruct *wim, int flags);
+extern int wimlib_overwrite(WIMStruct *wim, int write_flags,
+			    unsigned num_threads);
 
 /**
- * Updates the header and XML data of the WIM file, without the need to write
- * out the entire WIM to a temporary file as in wimlib_write().
- *
- * This function must only be used if no files, directories, or images have been
- * added, removed, or changed in the WIM.  It must be used when only the boot
- * index or the name or description of image(s) has been changed.
- *
- * After this function returns, @a wim must be freed using wimlib_free().  Any
- * further actions on @a wim before doing this are undefined.
- *
- * @param wim
- * 	Pointer to the ::WIMStruct for the WIM file to overwrite.
- * @param flags 
- * 	Bitwise OR of ::WIMLIB_WRITE_FLAG_CHECK_INTEGRITY and/or
- * 	::WIMLIB_WRITE_FLAG_SHOW_PROGRESS.
- *
- * @return 0 on success; nonzero on error.
- *
- * @retval ::WIMLIB_ERR_NO_FILENAME
- * 	@a wim corresponds to a WIM created with wimlib_create_new_wim() rather
- * 	than a WIM read with wimlib_open_wim().
- * @retval ::WIMLIB_ERR_NOMEM
- * 	Failed to allocate needed memory.
- * @retval ::WIMLIB_ERR_OPEN
- * 	The WIM file associated with @a wim could not be re-opened read-write.
- * @retval ::WIMLIB_ERR_READ
- * 	::WIMLIB_WRITE_FLAG_CHECK_INTEGRITY was specified in @a flags, but data
- * 	from the WIM file associated with @a wim could not be read to compute
- * 	the SHA1 message digests, or the old integrity table (if it existed)
- * 	could not be read.
- * @retval ::WIMLIB_ERR_WRITE
- * 	Failed to write the WIM header, the XML data, or the integrity table to
- * 	the WIM file associated with @a wim.
+ * This function is deprecated; call wimlib_overwrite() instead.
+ * (wimlib_overwrite() no longer rebuilds the full WIM unless it has to or is
+ * specified explicitly with ::WIMLIB_WRITE_FLAG_REBUILD)
  */
-extern int wimlib_overwrite_xml_and_header(WIMStruct *wim, int flags);
+extern int wimlib_overwrite_xml_and_header(WIMStruct *wim, int write_flags);
 
 /**
  * Prints information about one image, or all images, contained in a WIM.
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * @param image 
+ * @param image
  * 	The image about which to print information.  Can be the number of an
  * 	image, or ::WIM_ALL_IMAGES to print information about all images in the
  * 	WIM.
- * 
+ *
  * @return This function has no return value.  No error checking is done when
  * printing the information.  If @a image is invalid, an error message is
  * printed.
@@ -1141,9 +1186,9 @@ extern void wimlib_print_available_images(const WIMStruct *wim, int image);
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * @param image 
+ * @param image
  * 	Which image to print files for.  Can be the number of an image, or
- * 	::WIM_ALL_IMAGES to print the files contained in all images.  
+ * 	::WIM_ALL_IMAGES to print the files contained in all images.
  *
  * @return 0 on success; nonzero on error.
  * @retval ::WIMLIB_ERR_DECOMPRESSION
@@ -1184,7 +1229,7 @@ extern int wimlib_print_files(WIMStruct *wim, int image);
  */
 extern void wimlib_print_header(const WIMStruct *wim);
 
-/** 
+/**
  * Prints the lookup table of a WIM file.  The lookup table maps SHA1 message
  * digests, as found in the directory entry tree in the WIM file, to file
  * resources in the WIM file.  This table includes one entry for each unique
@@ -1201,11 +1246,11 @@ extern void wimlib_print_lookup_table(WIMStruct *wim);
 /**
  * Prints the metadata of the specified image in a WIM file.  The metadata
  * consists of the security data as well as the directory entry tree, and each
- * image has its own metadata.  
+ * image has its own metadata.
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * @param image 
+ * @param image
  * 	Which image to print the metadata for.  Can be the number of an image,
  * 	or ::WIM_ALL_IMAGES to print the metadata for all images in the WIM.
  *
@@ -1245,7 +1290,7 @@ extern int wimlib_print_metadata(WIMStruct *wim, int image);
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
  *
- * @return This function has no return value.  
+ * @return This function has no return value.
  */
 extern void wimlib_print_wim_information(const WIMStruct *wim);
 
@@ -1255,14 +1300,14 @@ extern void wimlib_print_wim_information(const WIMStruct *wim);
  *
  * @param wim
  * 	Pointer to the ::WIMStruct for a WIM file.
- * @param image_name_or_num  
+ * @param image_name_or_num
  * 	A string specifying which image.  If it begins with a number, it is
  * 	taken to be a string specifying the image number.  Otherwise, it is
  * 	taken to be the name of an image, as specified in the XML data for the
  * 	WIM file.  It also may be the keyword "all" or the string "*", both of
  * 	which will resolve to ::WIM_ALL_IMAGES.
  *
- * @return 
+ * @return
  * 	If the string resolved to a single existing image, the number of that
  * 	image, counting starting at 1, is returned.  If the keyword "all" was
  * 	specified, ::WIM_ALL_IMAGES is returned.  Otherwise, ::WIM_NO_IMAGE is
@@ -1281,7 +1326,7 @@ extern int wimlib_resolve_image(WIMStruct *wim, const char *image_name_or_num);
  * @return 0 on success; nonzero on error.
  * @retval ::WIMLIB_ERR_INVALID_PARAM
  * 	@a wim was @c NULL.
- * @retval ::WIMLIB_ERR_INVALID_IMAGE 
+ * @retval ::WIMLIB_ERR_INVALID_IMAGE
  * 	@a boot_idx does not specify an existing image in @a wim, and it was not
  * 	0.
  * @retval ::WIMLIB_ERR_SPLIT_UNSUPPORTED
@@ -1312,7 +1357,7 @@ extern int wimlib_set_boot_idx(WIMStruct *wim, int boot_idx);
  * 	Failed to allocate the memory needed to duplicate the @a description
  * 	string.
  */
-extern int wimlib_set_image_descripton(WIMStruct *wim, int image, 
+extern int wimlib_set_image_descripton(WIMStruct *wim, int image,
 				       const char *description);
 
 /**
@@ -1442,7 +1487,7 @@ extern int wimlib_set_print_errors(bool show_messages);
  * 	An error occurred when trying to write data to one of the split WIMs.
  *
  */
-extern int wimlib_split(const char *wimfile, const char *swm_name, 
+extern int wimlib_split(const char *wimfile, const char *swm_name,
 			size_t part_size, int flags);
 
 /**
@@ -1459,7 +1504,7 @@ extern int wimlib_split(const char *wimfile, const char *swm_name,
  * there should be no infinite loops or crashes in the code, so this wouldn't be
  * much of a problem.  Currently, a timeout of 600 seconds (so long because WIMs
  * can be very large) is implemented so that this function will not wait forever
- * before returning failure.  
+ * before returning failure.
  *
  * @param dir
  * 	The directory that the WIM image was mounted on.
@@ -1515,18 +1560,24 @@ extern int wimlib_unmount(const char *dir, int flags);
  * @param image
  * 	The image inside the WIM to write.  Use ::WIM_ALL_IMAGES to include all
  * 	images.
- * @param flags 
+ * @param write_flags
  * 	Bitwise OR of ::WIMLIB_WRITE_FLAG_CHECK_INTEGRITY and/or
  * 	::WIMLIB_WRITE_FLAG_SHOW_PROGRESS.  If
  * 	::WIMLIB_WRITE_FLAG_CHECK_INTEGRITY is given, an integrity table is
  * 	included in the WIM being written.  If ::WIMLIB_WRITE_FLAG_SHOW_PROGRESS
  * 	is given, the progress of the calculation of the integrity table is
  * 	shown.
+ * @param num_threads
+ * 	Number of threads to use for compressing data.  Autodetected if set to
+ * 	0.  Note: if no data compression needs to be done, no threads will be
+ * 	created regardless of this parameter (e.g. if writing an uncompressed
+ * 	WIM, or exporting an image from a compressed WIM to another WIM of the
+ * 	same compression type).
  *
  * @return 0 on success; nonzero on error.
  * @retval ::WIMLIB_ERR_DECOMPRESSION
  * 	Failed to decompress a metadata or file resource in @a wim.
- * @retval ::WIMLIB_ERR_INVALID_DENTRY 
+ * @retval ::WIMLIB_ERR_INVALID_DENTRY
  * 	A directory entry in the metadata resource for @a image in @a wim is
  * 	invalid.
  * @retval ::WIMLIB_ERR_INVALID_IMAGE
@@ -1539,7 +1590,7 @@ extern int wimlib_unmount(const char *dir, int flags);
  * @retval ::WIMLIB_ERR_INVALID_PARAM
  * 	@a wim or @a path was @c NULL.
  * @retval ::WIMLIB_ERR_INVALID_RESOURCE_SIZE
- *	The metadata resource for @a image in @a wim is invalid.	
+ *	The metadata resource for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_INVALID_SECURITY_DATA
  *	The security data for @a image in @a wim is invalid.
  * @retval ::WIMLIB_ERR_NOMEM
@@ -1560,7 +1611,8 @@ extern int wimlib_unmount(const char *dir, int flags);
  * 	An error occurred when trying to write data to the new WIM file at @a
  * 	path.
  */
-extern int wimlib_write(WIMStruct *wim, const char *path, int image, int flags);
+extern int wimlib_write(WIMStruct *wim, const char *path, int image,
+			int write_flags, unsigned num_threads);