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/** * \file lzma/filter.h * \brief Common filter related types and functions * \note Never include this file directly. Use <lzma.h> instead. */ /* * Author: Lasse Collin * * This file has been put into the public domain. * You can do whatever you want with this file. */ #ifndef LZMA_H_INTERNAL # error Never include this file directly. Use <lzma.h> instead. #endif /** * \brief Maximum number of filters in a chain * * A filter chain can have 1-4 filters, of which three are allowed to change * the size of the data. Usually only one or two filters are needed. */ #define LZMA_FILTERS_MAX 4 /** * \brief Filter options * * This structure is used to pass a Filter ID and a pointer to the filter's * options to liblzma. A few functions work with a single lzma_filter * structure, while most functions expect a filter chain. * * A filter chain is indicated with an array of lzma_filter structures. * The array is terminated with .id = LZMA_VLI_UNKNOWN. Thus, the filter * array must have LZMA_FILTERS_MAX + 1 elements (that is, five) to * be able to hold any arbitrary filter chain. This is important when * using lzma_block_header_decode() from block.h, because a filter array * that is too small would make liblzma write past the end of the array. */ typedef struct { /** * \brief Filter ID * * Use constants whose name begin with `LZMA_FILTER_' to specify * different filters. In an array of lzma_filter structures, use * LZMA_VLI_UNKNOWN to indicate end of filters. * * \note This is not an enum, because on some systems enums * cannot be 64-bit. */ lzma_vli id; /** * \brief Pointer to filter-specific options structure * * If the filter doesn't need options, set this to NULL. If id is * set to LZMA_VLI_UNKNOWN, options is ignored, and thus * doesn't need be initialized. */ void *options; } lzma_filter; /** * \brief Test if the given Filter ID is supported for encoding * * \param id Filter ID * * \return lzma_bool: * - true if the Filter ID is supported for encoding by this * liblzma build. * - false otherwise. */ extern LZMA_API(lzma_bool) lzma_filter_encoder_is_supported(lzma_vli id) lzma_nothrow lzma_attr_const; /** * \brief Test if the given Filter ID is supported for decoding * * \param id Filter ID * * \return lzma_bool: * - true if the Filter ID is supported for decoding by this * liblzma build. * - false otherwise. */ extern LZMA_API(lzma_bool) lzma_filter_decoder_is_supported(lzma_vli id) lzma_nothrow lzma_attr_const; /** * \brief Copy the filters array * * Copy the Filter IDs and filter-specific options from src to dest. * Up to LZMA_FILTERS_MAX filters are copied, plus the terminating * .id == LZMA_VLI_UNKNOWN. Thus, dest should have at least * LZMA_FILTERS_MAX + 1 elements space unless the caller knows that * src is smaller than that. * * Unless the filter-specific options is NULL, the Filter ID has to be * supported by liblzma, because liblzma needs to know the size of every * filter-specific options structure. The filter-specific options are not * validated. If options is NULL, any unsupported Filter IDs are copied * without returning an error. * * Old filter-specific options in dest are not freed, so dest doesn't * need to be initialized by the caller in any way. * * If an error occurs, memory possibly already allocated by this function * is always freed. liblzma versions older than 5.2.7 may modify the dest * array and leave its contents in an undefined state if an error occurs. * liblzma 5.2.7 and newer only modify the dest array when returning LZMA_OK. * * \param src Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * \param[out] dest Destination filter array * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_MEM_ERROR * - LZMA_OPTIONS_ERROR: Unsupported Filter ID and its options * is not NULL. * - LZMA_PROG_ERROR: src or dest is NULL. */ extern LZMA_API(lzma_ret) lzma_filters_copy( const lzma_filter *src, lzma_filter *dest, const lzma_allocator *allocator) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Free the options in the array of lzma_filter structures * * This frees the filter chain options. The filters array itself is not freed. * * The filters array must have at most LZMA_FILTERS_MAX + 1 elements * including the terminating element which must have .id = LZMA_VLI_UNKNOWN. * For all elements before the terminating element: * - options will be freed using the given lzma_allocator or, * if allocator is NULL, using free(). * - options will be set to NULL. * - id will be set to LZMA_VLI_UNKNOWN. * * If filters is NULL, this does nothing. Again, this never frees the * filters array itself. * * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). */ extern LZMA_API(void) lzma_filters_free( lzma_filter *filters, const lzma_allocator *allocator) lzma_nothrow; /** * \brief Calculate approximate memory requirements for raw encoder * * This function can be used to calculate the memory requirements for * Block and Stream encoders too because Block and Stream encoders don't * need significantly more memory than raw encoder. * * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * * \return Number of bytes of memory required for the given * filter chain when encoding or UINT64_MAX on error. */ extern LZMA_API(uint64_t) lzma_raw_encoder_memusage(const lzma_filter *filters) lzma_nothrow lzma_attr_pure; /** * \brief Calculate approximate memory requirements for raw decoder * * This function can be used to calculate the memory requirements for * Block and Stream decoders too because Block and Stream decoders don't * need significantly more memory than raw decoder. * * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * * \return Number of bytes of memory required for the given * filter chain when decoding or UINT64_MAX on error. */ extern LZMA_API(uint64_t) lzma_raw_decoder_memusage(const lzma_filter *filters) lzma_nothrow lzma_attr_pure; /** * \brief Initialize raw encoder * * This function may be useful when implementing custom file formats. * * The `action' with lzma_code() can be LZMA_RUN, LZMA_SYNC_FLUSH (if the * filter chain supports it), or LZMA_FINISH. * * \param strm Pointer to lzma_stream that is at least * initialized with LZMA_STREAM_INIT. * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_MEM_ERROR * - LZMA_OPTIONS_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_raw_encoder( lzma_stream *strm, const lzma_filter *filters) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Initialize raw decoder * * The initialization of raw decoder goes similarly to raw encoder. * * The `action' with lzma_code() can be LZMA_RUN or LZMA_FINISH. Using * LZMA_FINISH is not required, it is supported just for convenience. * * \param strm Pointer to lzma_stream that is at least * initialized with LZMA_STREAM_INIT. * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_MEM_ERROR * - LZMA_OPTIONS_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_raw_decoder( lzma_stream *strm, const lzma_filter *filters) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Update the filter chain in the encoder * * This function may be called after lzma_code() has returned LZMA_STREAM_END * when LZMA_FULL_BARRIER, LZMA_FULL_FLUSH, or LZMA_SYNC_FLUSH was used: * * - After LZMA_FULL_BARRIER or LZMA_FULL_FLUSH: Single-threaded .xz Stream * encoder (lzma_stream_encoder()) and (since liblzma 5.4.0) multi-threaded * Stream encoder (lzma_stream_encoder_mt()) allow setting a new filter * chain to be used for the next Block(s). * * - After LZMA_SYNC_FLUSH: Raw encoder (lzma_raw_encoder()), * Block encoder (lzma_block_encoder()), and single-threaded .xz Stream * encoder (lzma_stream_encoder()) allow changing certain filter-specific * options in the middle of encoding. The actual filters in the chain * (Filter IDs) must not be changed! Currently only the lc, lp, and pb * options of LZMA2 (not LZMA1) can be changed this way. * * - In the future some filters might allow changing some of their options * without any barrier or flushing but currently such filters don't exist. * * This function may also be called when no data has been compressed yet * although this is rarely useful. In that case, this function will behave * as if LZMA_FULL_FLUSH (Stream encoders) or LZMA_SYNC_FLUSH (Raw or Block * encoder) had been used right before calling this function. * * \param strm Pointer to lzma_stream that is at least * initialized with LZMA_STREAM_INIT. * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_MEM_ERROR * - LZMA_MEMLIMIT_ERROR * - LZMA_OPTIONS_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_filters_update( lzma_stream *strm, const lzma_filter *filters) lzma_nothrow; /** * \brief Single-call raw encoder * * \note There is no function to calculate how big output buffer * would surely be big enough. (lzma_stream_buffer_bound() * works only for lzma_stream_buffer_encode(); raw encoder * won't necessarily meet that bound.) * * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * \param in Beginning of the input buffer * \param in_size Size of the input buffer * \param[out] out Beginning of the output buffer * \param[out] out_pos The next byte will be written to out[*out_pos]. * *out_pos is updated only if encoding succeeds. * \param out_size Size of the out buffer; the first byte into * which no data is written to is out[out_size]. * * \return Possible lzma_ret values: * - LZMA_OK: Encoding was successful. * - LZMA_BUF_ERROR: Not enough output buffer space. * - LZMA_OPTIONS_ERROR * - LZMA_MEM_ERROR * - LZMA_DATA_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_raw_buffer_encode( const lzma_filter *filters, const lzma_allocator *allocator, const uint8_t *in, size_t in_size, uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow; /** * \brief Single-call raw decoder * * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * \param in Beginning of the input buffer * \param in_pos The next byte will be read from in[*in_pos]. * *in_pos is updated only if decoding succeeds. * \param in_size Size of the input buffer; the first byte that * won't be read is in[in_size]. * \param[out] out Beginning of the output buffer * \param[out] out_pos The next byte will be written to out[*out_pos]. * *out_pos is updated only if encoding succeeds. * \param out_size Size of the out buffer; the first byte into * which no data is written to is out[out_size]. * * \return Possible lzma_ret values: * - LZMA_OK: Decoding was successful. * - LZMA_BUF_ERROR: Not enough output buffer space. * - LZMA_OPTIONS_ERROR * - LZMA_MEM_ERROR * - LZMA_DATA_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_raw_buffer_decode( const lzma_filter *filters, const lzma_allocator *allocator, const uint8_t *in, size_t *in_pos, size_t in_size, uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow; /** * \brief Get the size of the Filter Properties field * * This function may be useful when implementing custom file formats * using the raw encoder and decoder. * * \note This function validates the Filter ID, but does not * necessarily validate the options. Thus, it is possible * that this returns LZMA_OK while the following call to * lzma_properties_encode() returns LZMA_OPTIONS_ERROR. * * \param[out] size Pointer to uint32_t to hold the size of the properties * \param filter Filter ID and options (the size of the properties may * vary depending on the options) * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_OPTIONS_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_properties_size( uint32_t *size, const lzma_filter *filter) lzma_nothrow; /** * \brief Encode the Filter Properties field * * \note Even this function won't validate more options than actually * necessary. Thus, it is possible that encoding the properties * succeeds but using the same options to initialize the encoder * will fail. * * \note If lzma_properties_size() indicated that the size * of the Filter Properties field is zero, calling * lzma_properties_encode() is not required, but it * won't do any harm either. * * \param filter Filter ID and options * \param[out] props Buffer to hold the encoded options. The size of * the buffer must have been already determined with * lzma_properties_size(). * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_properties_encode( const lzma_filter *filter, uint8_t *props) lzma_nothrow; /** * \brief Decode the Filter Properties field * * \param filter filter->id must have been set to the correct * Filter ID. filter->options doesn't need to be * initialized (it's not freed by this function). The * decoded options will be stored in filter->options; * it's application's responsibility to free it when * appropriate. filter->options is set to NULL if * there are no properties or if an error occurs. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * and in case of an error, also free(). * \param props Input buffer containing the properties. * \param props_size Size of the properties. This must be the exact * size; giving too much or too little input will * return LZMA_OPTIONS_ERROR. * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_OPTIONS_ERROR * - LZMA_MEM_ERROR */ extern LZMA_API(lzma_ret) lzma_properties_decode( lzma_filter *filter, const lzma_allocator *allocator, const uint8_t *props, size_t props_size) lzma_nothrow; /** * \brief Calculate encoded size of a Filter Flags field * * Knowing the size of Filter Flags is useful to know when allocating * memory to hold the encoded Filter Flags. * * \note If you need to calculate size of List of Filter Flags, * you need to loop over every lzma_filter entry. * * \param[out] size Pointer to integer to hold the calculated size * \param filter Filter ID and associated options whose encoded * size is to be calculated * * \return Possible lzma_ret values: * - LZMA_OK: *size set successfully. Note that this doesn't * guarantee that filter->options is valid, thus * lzma_filter_flags_encode() may still fail. * - LZMA_OPTIONS_ERROR: Unknown Filter ID or unsupported options. * - LZMA_PROG_ERROR: Invalid options */ extern LZMA_API(lzma_ret) lzma_filter_flags_size( uint32_t *size, const lzma_filter *filter) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Encode Filter Flags into given buffer * * In contrast to some functions, this doesn't allocate the needed buffer. * This is due to how this function is used internally by liblzma. * * \param filter Filter ID and options to be encoded * \param[out] out Beginning of the output buffer * \param[out] out_pos out[*out_pos] is the next write position. This * is updated by the encoder. * \param out_size out[out_size] is the first byte to not write. * * \return Possible lzma_ret values: * - LZMA_OK: Encoding was successful. * - LZMA_OPTIONS_ERROR: Invalid or unsupported options. * - LZMA_PROG_ERROR: Invalid options or not enough output * buffer space (you should have checked it with * lzma_filter_flags_size()). */ extern LZMA_API(lzma_ret) lzma_filter_flags_encode(const lzma_filter *filter, uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Decode Filter Flags from given buffer * * The decoded result is stored into *filter. The old value of * filter->options is not free()d. If anything other than LZMA_OK * is returned, filter->options is set to NULL. * * \param[out] filter Destination filter. The decoded Filter ID will * be stored in filter->id. If options are needed * they will be allocated and the pointer will be * stored in filter->options. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * \param in Beginning of the input buffer * \param[out] in_pos The next byte will be read from in[*in_pos]. * *in_pos is updated only if decoding succeeds. * \param in_size Size of the input buffer; the first byte that * won't be read is in[in_size]. * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_OPTIONS_ERROR * - LZMA_MEM_ERROR * - LZMA_DATA_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_filter_flags_decode( lzma_filter *filter, const lzma_allocator *allocator, const uint8_t *in, size_t *in_pos, size_t in_size) lzma_nothrow lzma_attr_warn_unused_result; /*********** * Strings * ***********/ /** * \brief Allow or show all filters * * By default only the filters supported in the .xz format are accept by * lzma_str_to_filters() or shown by lzma_str_list_filters(). */ #define LZMA_STR_ALL_FILTERS UINT32_C(0x01) /** * \brief Do not validate the filter chain in lzma_str_to_filters() * * By default lzma_str_to_filters() can return an error if the filter chain * as a whole isn't usable in the .xz format or in the raw encoder or decoder. * With this flag, this validation is skipped. This flag doesn't affect the * handling of the individual filter options. To allow non-.xz filters also * LZMA_STR_ALL_FILTERS is needed. */ #define LZMA_STR_NO_VALIDATION UINT32_C(0x02) /** * \brief Stringify encoder options * * Show the filter-specific options that the encoder will use. * This may be useful for verbose diagnostic messages. * * Note that if options were decoded from .xz headers then the encoder options * may be undefined. This flag shouldn't be used in such a situation. */ #define LZMA_STR_ENCODER UINT32_C(0x10) /** * \brief Stringify decoder options * * Show the filter-specific options that the decoder will use. * This may be useful for showing what filter options were decoded * from file headers. */ #define LZMA_STR_DECODER UINT32_C(0x20) /** * \brief Produce xz-compatible getopt_long() syntax * * That is, "delta:dist=2 lzma2:dict=4MiB,pb=1,lp=1" becomes * "--delta=dist=2 --lzma2=dict=4MiB,pb=1,lp=1". * * This syntax is compatible with xz 5.0.0 as long as the filters and * their options are supported too. */ #define LZMA_STR_GETOPT_LONG UINT32_C(0x40) /** * \brief Use two dashes "--" instead of a space to separate filters * * That is, "delta:dist=2 lzma2:pb=1,lp=1" becomes * "delta:dist=2--lzma2:pb=1,lp=1". This looks slightly odd but this * kind of strings should be usable on the command line without quoting. * However, it is possible that future versions with new filter options * might produce strings that require shell quoting anyway as the exact * set of possible characters isn't frozen for now. * * It is guaranteed that the single quote (') will never be used in * filter chain strings (even if LZMA_STR_NO_SPACES isn't used). */ #define LZMA_STR_NO_SPACES UINT32_C(0x80) /** * \brief Convert a string to a filter chain * * This tries to make it easier to write applications that allow users * to set custom compression options. This only handles the filter * configuration (including presets) but not the number of threads, * block size, check type, or memory limits. * * The input string can be either a preset or a filter chain. Presets * begin with a digit 0-9 and may be followed by zero or more flags * which are lower-case letters. Currently only "e" is supported, matching * LZMA_PRESET_EXTREME. For partial xz command line syntax compatibility, * a preset string may start with a single dash "-". * * A filter chain consists of one or more "filtername:opt1=value1,opt2=value2" * strings separated by one or more spaces. Leading and trailing spaces are * ignored. All names and values must be lower-case. Extra commas in the * option list are ignored. The order of filters is significant: when * encoding, the uncompressed input data goes to the leftmost filter first. * Normally "lzma2" is the last filter in the chain. * * If one wishes to avoid spaces, for example, to avoid shell quoting, * it is possible to use two dashes "--" instead of spaces to separate * the filters. * * For xz command line compatibility, each filter may be prefixed with * two dashes "--" and the colon ":" separating the filter name from * the options may be replaced with an equals sign "=". * * By default, only filters that can be used in the .xz format are accepted. * To allow all filters (LZMA1) use the flag LZMA_STR_ALL_FILTERS. * * By default, very basic validation is done for the filter chain as a whole, * for example, that LZMA2 is only used as the last filter in the chain. * The validation isn't perfect though and it's possible that this function * succeeds but using the filter chain for encoding or decoding will still * result in LZMA_OPTIONS_ERROR. To disable this validation, use the flag * LZMA_STR_NO_VALIDATION. * * The available filter names and their options are available via * lzma_str_list_filters(). See the xz man page for the description * of filter names and options. * * For command line applications, below is an example how an error message * can be displayed. Note the use of an empty string for the field width. * If "^" was used there it would create an off-by-one error except at * the very beginning of the line. * * \code{.c} * const char *str = ...; // From user * lzma_filter filters[LZMA_FILTERS_MAX + 1]; * int pos; * const char *msg = lzma_str_to_filters(str, &pos, filters, 0, NULL); * if (msg != NULL) { * printf("%s: Error in XZ compression options:\n", argv[0]); * printf("%s: %s\n", argv[0], str); * printf("%s: %*s^\n", argv[0], errpos, ""); * printf("%s: %s\n", argv[0], msg); * } * \endcode * * \param str User-supplied string describing a preset or * a filter chain. If a default value is needed and * you don't know what would be good, use "6" since * that is the default preset in xz too. * \param[out] error_pos If this isn't NULL, this value will be set on * both success and on all errors. This tells the * location of the error in the string. This is * an int to make it straightforward to use this * as printf() field width. The value is guaranteed * to be in the range [0, INT_MAX] even if strlen(str) * somehow was greater than INT_MAX. * \param[out] filters An array of lzma_filter structures. There must * be LZMA_FILTERS_MAX + 1 (that is, five) elements * in the array. The old contents are ignored so it * doesn't need to be initialized. This array is * modified only if this function returns NULL. * Once the allocated filter options are no longer * needed, lzma_filters_free() can be used to free the * options (it doesn't free the filters array itself). * \param flags Bitwise-or of zero or more of the flags * LZMA_STR_ALL_FILTERS and LZMA_STR_NO_VALIDATION. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * * \return On success, NULL is returned. On error, a statically-allocated * error message is returned which together with the error_pos * should give some idea what is wrong. */ extern LZMA_API(const char *) lzma_str_to_filters( const char *str, int *error_pos, lzma_filter *filters, uint32_t flags, const lzma_allocator *allocator) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief Convert a filter chain to a string * * Use cases: * * - Verbose output showing the full encoder options to the user * (use LZMA_STR_ENCODER in flags) * * - Showing the filters and options that are required to decode a file * (use LZMA_STR_DECODER in flags) * * - Showing the filter names without any options in informational messages * where the technical details aren't important (no flags). In this case * the .options in the filters array are ignored and may be NULL even if * a filter has a mandatory options structure. * * Note that even if the filter chain was specified using a preset, * the resulting filter chain isn't reversed to a preset. So if you * specify "6" to lzma_str_to_filters() then lzma_str_from_filters() * will produce a string containing "lzma2". * * \param[out] str On success *str will be set to point to an * allocated string describing the given filter * chain. Old value is ignored. On error *str is * always set to NULL. * \param filters Array of filters terminated with * .id == LZMA_VLI_UNKNOWN. * \param flags Bitwise-or of zero or more of the flags * LZMA_STR_ENCODER, LZMA_STR_DECODER, * LZMA_STR_GETOPT_LONG, and LZMA_STR_NO_SPACES. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_OPTIONS_ERROR: Empty filter chain * (filters[0].id == LZMA_VLI_UNKNOWN) or the filter chain * includes a Filter ID that is not supported by this function. * - LZMA_MEM_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_str_from_filters( char **str, const lzma_filter *filters, uint32_t flags, const lzma_allocator *allocator) lzma_nothrow lzma_attr_warn_unused_result; /** * \brief List available filters and/or their options (for help message) * * If a filter_id is given then only one line is created which contains the * filter name. If LZMA_STR_ENCODER or LZMA_STR_DECODER is used then the * options read by the encoder or decoder are printed on the same line. * * If filter_id is LZMA_VLI_UNKNOWN then all supported .xz-compatible filters * are listed: * * - If neither LZMA_STR_ENCODER nor LZMA_STR_DECODER is used then * the supported filter names are listed on a single line separated * by spaces. * * - If LZMA_STR_ENCODER or LZMA_STR_DECODER is used then filters and * the supported options are listed one filter per line. There won't * be a newline after the last filter. * * - If LZMA_STR_ALL_FILTERS is used then the list will include also * those filters that cannot be used in the .xz format (LZMA1). * * \param str On success *str will be set to point to an * allocated string listing the filters and options. * Old value is ignored. On error *str is always set * to NULL. * \param filter_id Filter ID or LZMA_VLI_UNKNOWN. * \param flags Bitwise-or of zero or more of the flags * LZMA_STR_ALL_FILTERS, LZMA_STR_ENCODER, * LZMA_STR_DECODER, and LZMA_STR_GETOPT_LONG. * \param allocator lzma_allocator for custom allocator functions. * Set to NULL to use malloc() and free(). * * \return Possible lzma_ret values: * - LZMA_OK * - LZMA_OPTIONS_ERROR: Unsupported filter_id or flags * - LZMA_MEM_ERROR * - LZMA_PROG_ERROR */ extern LZMA_API(lzma_ret) lzma_str_list_filters( char **str, lzma_vli filter_id, uint32_t flags, const lzma_allocator *allocator) lzma_nothrow lzma_attr_warn_unused_result;