diff options
Diffstat (limited to 'src/liblzma/api/lzma/container.h')
| -rw-r--r-- | src/liblzma/api/lzma/container.h | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/src/liblzma/api/lzma/container.h b/src/liblzma/api/lzma/container.h index 9fbf4df0..581f3507 100644 --- a/src/liblzma/api/lzma/container.h +++ b/src/liblzma/api/lzma/container.h @@ -444,6 +444,55 @@ extern LZMA_API(lzma_ret) lzma_stream_buffer_encode( lzma_nothrow lzma_attr_warn_unused_result; +/** + * \brief EROFS LZMA encoder + * + * The EROFS LZMA format is a raw LZMA stream whose first byte (always 0x00) + * has been replaced with bitwise-negation of the LZMA properties (lc/lp/pb). + * This encoding ensures that the first byte of EROFS LZMA stream is never + * 0x00. There is no end of payload marker and thus the uncompressed size + * must be stored separately. For the best error detection the dictionary + * size should be stored separately as well but alternatively one may use + * the uncompressed size as the dictionary size when decoding. + * + * With the EROFS LZMA encoder, lzma_code() behaves slightly unusually. + * The action argument must be LZMA_FINISH and the return value cannot be + * LZMA_OK. Thus the encoding is always done with a single lzma_code() after + * the initialization. The benefit of the combination of initialization + * function and lzma_code() is that memory allocations can be re-used for + * better performance. + * + * lzma_code() will try to encode as much input as is possible to fit into + * the given output buffer. If not all input can be encoded, the stream will + * be finished without encoding all the input. The caller must check both + * input and output buffer usage after lzma_code() (total_in and total_out + * in lzma_stream can be convenient). Often lzma_code() can fill the output + * buffer completely if there is a lot of input, but sometimes a few bytes + * may remain unused because the next LZMA symbol would require more space. + * + * lzma_stream.avail_out must be at least 6. Otherwise LZMA_PROG_ERROR + * will be returned. + * + * The LZMA dictionary should be reasonably low to speed up the encoder + * re-initialization. A good value is bigger than the resulting + * uncompressed size of most of the output chunks. For example, if output + * size is 4 KiB, dictionary size of 32 KiB or 64 KiB is good. If the + * data compresses extremely well, even 128 KiB may be useful. + * + * \return - LZMA_STREAM_END: All good. Check the amounts of input used + * and output produced. Store the amount of input used + * (uncompressed size) as it needs to be known to decompress + * the data. + * - LZMA_OPTIONS_ERROR + * - LZMA_MEM_ERROR + * - LZMA_PROG_ERROR: In addition to the generic reasons for this + * error code, this may also be returned if there isn't enough + * output space (6 bytes) to create a valid EROFS LZMA stream. + */ +extern LZMA_API(lzma_ret) lzma_erofs_encoder( + lzma_stream *strm, const lzma_options_lzma *options); + + /************ * Decoding * ************/ @@ -630,3 +679,30 @@ extern LZMA_API(lzma_ret) lzma_stream_buffer_decode( 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 lzma_attr_warn_unused_result; + + +/** + * \brief EROFS LZMA decoder + * + * See lzma_erofs_decoder() for more information. + * + * The lzma_code() usage with this decoder is completely normal. + * The special behavior of lzma_code() applies to lzma_erofs_encoder() only. + * + * \param strm Pointer to properly prepared lzma_stream + * \param uncomp_size Uncompressed size of the EROFS LZMA stream. + * The caller must somehow know this. Note that + * while the EROFS LZMA decoder in XZ Embedded needs + * also the compressed size, the implementation in + * liblzma doesn't need to know the compressed size. + * \param dict_size LZMA dictionary size that was used when + * compressing the data. It is OK to use a bigger + * value too but liblzma will then allocate more + * memory than would actually be required and error + * detection will be slightly worse. (Note that with + * the implementation in XZ Embedded it doesn't + * affect the memory usage if one specifies bigger + * dictionary than actually required.) + */ +extern LZMA_API(lzma_ret) lzma_erofs_decoder( + lzma_stream *strm, uint64_t uncomp_size, uint32_t dict_size); |