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Diffstat (limited to 'doc/lz4_manual.html')
| -rw-r--r-- | doc/lz4_manual.html | 65 |
1 files changed, 39 insertions, 26 deletions
diff --git a/doc/lz4_manual.html b/doc/lz4_manual.html index f25aa79..b738c8d 100644 --- a/doc/lz4_manual.html +++ b/doc/lz4_manual.html @@ -127,27 +127,6 @@ int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int src or 0 if compression fails. </p></pre><BR> -<pre><b>int LZ4_decompress_fast (const char* src, char* dst, int originalSize); -</b><p> This function used to be a bit faster than LZ4_decompress_safe(), - though situation has changed in recent versions, - and now `LZ4_decompress_safe()` can be as fast and sometimes faster than `LZ4_decompress_fast()`. - Moreover, LZ4_decompress_fast() is not protected vs malformed input, as it doesn't perform full validation of compressed data. - As a consequence, this function is no longer recommended, and may be deprecated in future versions. - It's last remaining specificity is that it can decompress data without knowing its compressed size. - - originalSize : is the uncompressed size to regenerate. - `dst` must be already allocated, its size must be >= 'originalSize' bytes. - @return : number of bytes read from source buffer (== compressed size). - If the source stream is detected malformed, the function stops decoding and returns a negative result. - note : This function requires uncompressed originalSize to be known in advance. - The function never writes past the output buffer. - However, since it doesn't know its 'src' size, it may read past the intended input. - Also, because match offsets are not validated during decoding, - reads from 'src' may underflow. - Use this function in trusted environment **only**. - -</p></pre><BR> - <pre><b>int LZ4_decompress_safe_partial (const char* src, char* dst, int srcSize, int targetOutputSize, int dstCapacity); </b><p> Decompress an LZ4 compressed block, of size 'srcSize' at position 'src', into destination buffer 'dst' of size 'dstCapacity'. @@ -258,7 +237,6 @@ int LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_stream); </p></pre><BR> <pre><b>int LZ4_decompress_safe_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int srcSize, int dstCapacity); -int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize); </b><p> These decoding functions allow decompression of consecutive blocks in "streaming" mode. A block is an unsplittable entity, it must be presented entirely to a decompression function. Decompression functions only accepts one block at a time. @@ -285,7 +263,6 @@ int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const ch </p></pre><BR> <pre><b>int LZ4_decompress_safe_usingDict (const char* src, char* dst, int srcSize, int dstCapcity, const char* dictStart, int dictSize); -int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize); </b><p> These decoding functions work the same as a combination of LZ4_setStreamDecode() followed by LZ4_decompress_*_continue() They are stand-alone, and don't need an LZ4_streamDecode_t structure. @@ -457,11 +434,47 @@ union LZ4_streamDecode_u { # define LZ4_DEPRECATED(message) # endif #endif </b>/* LZ4_DISABLE_DEPRECATE_WARNINGS */<b> -</b><p> Should deprecation warnings be a problem, - it is generally possible to disable them, +</b><p> + Deprecated functions make the compiler generate a warning when invoked. + This is meant to invite users to update their source code. + Should deprecation warnings be a problem, it is generally possible to disable them, typically with -Wno-deprecated-declarations for gcc or _CRT_SECURE_NO_WARNINGS in Visual. - Otherwise, it's also possible to define LZ4_DISABLE_DEPRECATE_WARNINGS + + Another method is to define LZ4_DISABLE_DEPRECATE_WARNINGS + before including the header file. + +</p></pre><BR> + +<pre><b>LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe() instead") LZ4LIB_API +int LZ4_decompress_fast (const char* src, char* dst, int originalSize); +LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_continue() instead") LZ4LIB_API +int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const char* src, char* dst, int originalSize); +LZ4_DEPRECATED("This function is deprecated and unsafe. Consider using LZ4_decompress_safe_usingDict() instead") LZ4LIB_API +int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize); +</b><p> These functions used to be a bit faster than LZ4_decompress_safe(), + but situation has changed in recent versions. + Now, `LZ4_decompress_safe()` is as fast and sometimes even faster than `LZ4_decompress_fast()`. + Moreover, LZ4_decompress_safe() is protected vs malformed input, while `LZ4_decompress_fast()` is not, making it a security liability. + As a consequence, LZ4_decompress_fast() is strongly discouraged, and deprecated. + + Last LZ4_decompress_fast() specificity is that it can decompress a block without knowing its compressed size. + Note that even that functionality could be achieved in a more secure manner if need be, + though it would require new prototypes, and adaptation of the implementation to this new use case. + + Parameters: + originalSize : is the uncompressed size to regenerate. + `dst` must be already allocated, its size must be >= 'originalSize' bytes. + @return : number of bytes read from source buffer (== compressed size). + The function expects to finish at block's end exactly. + If the source stream is detected malformed, the function stops decoding and returns a negative result. + note : LZ4_decompress_fast*() requires originalSize. Thanks to this information, it never writes past the output buffer. + However, since it doesn't know its 'src' size, it may read an unknown amount of input, and overflow input buffer. + Also, since match offsets are not validated, match reads from 'src' may underflow. + These issues never happen if input data is correct. + But they may happen if input data is invalid (error or intentional tampering). + As a consequence, use these functions in trusted environments with trusted data **only**. + </p></pre><BR> </html> |