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-rw-r--r--src/liblzma/api/lzma/container.h76
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);