diff options
Diffstat (limited to 'src/liblzma/api/lzma')
| -rw-r--r-- | src/liblzma/api/lzma/stream_flags.h | 84 |
1 files changed, 80 insertions, 4 deletions
diff --git a/src/liblzma/api/lzma/stream_flags.h b/src/liblzma/api/lzma/stream_flags.h index 80c5f00f..bb080ac7 100644 --- a/src/liblzma/api/lzma/stream_flags.h +++ b/src/liblzma/api/lzma/stream_flags.h @@ -36,8 +36,37 @@ */ typedef struct { /** + * \brief Stream Flags format version + * + * To prevent API and ABI breakages if new features are needed in + * Stream Header or Stream Footer, a version number is used to + * indicate which fields in this structure are in use. For now, + * version must always be zero. With non-zero version, the + * lzma_stream_header_encode() and lzma_stream_footer_encode() + * will return LZMA_HEADER_ERROR. + * + * lzma_stream_header_decode() and lzma_stream_footer_decode() + * will always set this to the lowest value that supports all the + * features indicated by the Stream Flags field. The application + * must check that the version number set by the decoding functions + * is supported by the application. Otherwise it is possible that + * the application will decode the Stream incorrectly. + */ + uint32_t version; + + /** * Backward Size must be a multiple of four bytes. In this Stream * format version Backward Size is the size of the Index field. + * + * Backward Size isn't actually part of the Stream Flags field, but + * it is convenient to include in this structure anyway. Backward + * Size is present only in the Stream Footer. There is no need to + * initialize backward_size when encoding Stream Header. + * + * lzma_stream_header_decode() always sets backward_size to + * LZMA_VLI_VALUE_UNKNOWN so that it is convenient to use + * lzma_stream_flags_compare() when both Stream Header and Stream + * Footer have been decoded. */ lzma_vli backward_size; # define LZMA_BACKWARD_SIZE_MIN 4 @@ -48,6 +77,34 @@ typedef struct { */ lzma_check check; + /** + * Reserved space to allow possible future extensions without + * breaking the ABI. You should not touch these, because the + * names of these variables may change. + * + * (We will never be able to use all of these since Stream Flags + * is just two bytes plus Backward Size of four bytes. But it's + * nice to have the proper types when they are needed.) + */ + lzma_reserved_enum reserved_enum1; + lzma_reserved_enum reserved_enum2; + lzma_reserved_enum reserved_enum3; + lzma_reserved_enum reserved_enum4; + lzma_reserved_enum reserved_enum5; + lzma_reserved_enum reserved_enum6; + lzma_bool reserved_bool1; + lzma_bool reserved_bool2; + lzma_bool reserved_bool3; + lzma_bool reserved_bool4; + lzma_bool reserved_bool5; + lzma_bool reserved_bool6; + lzma_bool reserved_bool7; + lzma_bool reserved_bool8; + uint32_t reserved_int1; + uint32_t reserved_int2; + uint32_t reserved_int3; + uint32_t reserved_int4; + } lzma_stream_flags; @@ -61,6 +118,8 @@ typedef struct { * need to be initialized. * * \return - LZMA_OK: Encoding was successful. + * - LZMA_HEADER_ERROR: options->version is not supported by + * this liblzma version. * - LZMA_PROG_ERROR: Invalid options. */ extern lzma_ret lzma_stream_header_encode( @@ -76,6 +135,8 @@ extern lzma_ret lzma_stream_header_encode( * \param options Stream Footer options to be encoded. * * \return - LZMA_OK: Encoding was successful. + * - LZMA_HEADER_ERROR: options->version is not supported by + * this liblzma version. * - LZMA_PROG_ERROR: Invalid options. */ extern lzma_ret lzma_stream_footer_encode( @@ -92,7 +153,7 @@ extern lzma_ret lzma_stream_footer_encode( * * options->index_size is always set to LZMA_VLI_VALUE_UNKNOWN. This is to * help comparing Stream Flags from Stream Header and Stream Footer with - * lzma_stream_flags_equal(). + * lzma_stream_flags_compare(). * * \return - LZMA_OK: Decoding was successful. * - LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given @@ -121,6 +182,13 @@ extern lzma_ret lzma_stream_header_decode( * is corrupt. * - LZMA_HEADER_ERROR: Unsupported options are present * in the footer. + * + * \note If Stream Header was already decoded successfully, but + * decoding Stream Footer returns LZMA_FORMAT_ERROR, the + * application should probably report some other error message + * than "unsupported file format", since the file more likely is + * corrupt (possibly truncated). Stream decoder in liblzma uses + * LZMA_DATA_ERROR in this situation. */ extern lzma_ret lzma_stream_footer_decode( lzma_stream_flags *options, const uint8_t *in) @@ -130,10 +198,18 @@ extern lzma_ret lzma_stream_footer_decode( /** * \brief Compare two lzma_stream_flags structures * - * index_size values are compared only if both are not LZMA_VLI_VALUE_UNKNOWN. + * backward_size values are compared only if both are not + * LZMA_VLI_VALUE_UNKNOWN. * - * \return true if both structures are considered equal; false otherwise. + * \return - LZMA_OK: Both are equal. If either had backward_size set + * to LZMA_VLI_VALUE_UNKNOWN, backward_size values were not + * compared or validated. + * - LZMA_DATA_ERROR: The structures differ. + * - LZMA_HEADER_ERROR: version in either structure is greater + * than the maximum supported version (currently zero). + * - LZMA_PROG_ERROR: Invalid value, e.g. invalid check or + * backward_size. */ -extern lzma_bool lzma_stream_flags_equal( +extern lzma_ret lzma_stream_flags_compare( const lzma_stream_flags *a, const lzma_stream_flags *b) lzma_attr_pure; |