summaryrefslogtreecommitdiffstats
path: root/doc/lz4_manual.html
diff options
context:
space:
mode:
Diffstat (limited to 'doc/lz4_manual.html')
-rw-r--r--doc/lz4_manual.html65
1 files changed, 33 insertions, 32 deletions
diff --git a/doc/lz4_manual.html b/doc/lz4_manual.html
index 46e6c3d..ef715f8 100644
--- a/doc/lz4_manual.html
+++ b/doc/lz4_manual.html
@@ -42,9 +42,9 @@
<a name="Chapter2"></a><h2>Version</h2><pre></pre>
-<pre><b>int LZ4_versionNumber (void); </b>/**< library version number; to be used when checking dll version */<b>
+<pre><b>int LZ4_versionNumber (void); </b>/**< library version number; useful to check dll version */<b>
</b></pre><BR>
-<pre><b>const char* LZ4_versionString (void); </b>/**< library version string; to be used when checking dll version */<b>
+<pre><b>const char* LZ4_versionString (void); </b>/**< library version string; unseful to check dll version */<b>
</b></pre><BR>
<a name="Chapter3"></a><h2>Tuning parameter</h2><pre></pre>
@@ -53,7 +53,7 @@
#endif
</b><p> Memory usage formula : N->2^N Bytes (examples : 10 -> 1KB; 12 -> 4KB ; 16 -> 64KB; 20 -> 1MB; etc.)
Increasing memory usage improves compression ratio
- Reduced memory usage can improve speed, due to cache effect
+ Reduced memory usage may improve speed, thanks to cache effect
Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache
</p></pre><BR>
@@ -65,12 +65,12 @@
into already allocated 'dst' buffer of size 'dstCapacity'.
Compression is guaranteed to succeed if 'dstCapacity' >= LZ4_compressBound(srcSize).
It also runs faster, so it's a recommended setting.
- If the function cannot compress 'src' into a limited 'dst' budget,
+ If the function cannot compress 'src' into a more limited 'dst' budget,
compression stops *immediately*, and the function result is zero.
- As a consequence, 'dst' content is not valid.
- This function never writes outside 'dst' buffer, nor read outside 'source' buffer.
- srcSize : supported max value is LZ4_MAX_INPUT_VALUE
- dstCapacity : full or partial size of buffer 'dst' (which must be already allocated)
+ Note : as a consequence, 'dst' content is not valid.
+ Note 2 : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer).
+ srcSize : max supported value is LZ4_MAX_INPUT_SIZE.
+ dstCapacity : size of buffer 'dst' (which must be already allocated)
return : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity)
or 0 if compression fails
</p></pre><BR>
@@ -81,8 +81,7 @@
return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity)
If destination buffer is not large enough, decoding will stop and output an error code (negative value).
If the source stream is detected malformed, the function will stop decoding and return a negative result.
- This function is protected against buffer overflow exploits, including malicious data packets.
- It never writes outside output buffer, nor reads outside input buffer.
+ This function is protected against malicious data packets.
</p></pre><BR>
<a name="Chapter5"></a><h2>Advanced Functions</h2><pre></pre>
@@ -91,18 +90,18 @@
</b><p> Provides the maximum size that LZ4 compression may output in a "worst case" scenario (input data not compressible)
This function is primarily useful for memory allocation purposes (destination buffer size).
Macro LZ4_COMPRESSBOUND() is also provided for compilation-time evaluation (stack memory allocation for example).
- Note that LZ4_compress_default() compress faster when dest buffer size is >= LZ4_compressBound(srcSize)
+ Note that LZ4_compress_default() compresses faster when dstCapacity is >= LZ4_compressBound(srcSize)
inputSize : max supported value is LZ4_MAX_INPUT_SIZE
return : maximum output size in a "worst case" scenario
- or 0, if input size is too large ( > LZ4_MAX_INPUT_SIZE)
+ or 0, if input size is incorrect (too large or negative)
</p></pre><BR>
<pre><b>int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
-</b><p> Same as LZ4_compress_default(), but allows to select an "acceleration" factor.
+</b><p> Same as LZ4_compress_default(), but allows selection of "acceleration" factor.
The larger the acceleration value, the faster the algorithm, but also the lesser the compression.
It's a trade-off. It can be fine tuned, with each successive value providing roughly +~3% to speed.
An acceleration value of "1" is the same as regular LZ4_compress_default()
- Values <= 0 will be replaced by ACCELERATION_DEFAULT (see lz4.c), which is 1.
+ Values <= 0 will be replaced by ACCELERATION_DEFAULT (currently == 1, see lz4.c).
</p></pre><BR>
<pre><b>int LZ4_sizeofState(void);
@@ -125,26 +124,28 @@ int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int src
</p></pre><BR>
<pre><b>int LZ4_decompress_fast (const char* src, char* dst, int originalSize);
-</b><p> originalSize : is the original uncompressed size
- return : the number of bytes read from the source buffer (in other words, the compressed size)
- If the source stream is detected malformed, the function will stop decoding and return a negative result.
- Destination buffer must be already allocated. Its size must be >= 'originalSize' bytes.
+</b><p>This function is a bit faster than LZ4_decompress_safe(),
+but doesn't provide any security guarantee.
+ originalSize : is the uncompressed size to regenerate
+ Destination buffer must be already allocated, and 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 return a negative result.
note : This function respects memory boundaries for *properly formed* compressed data.
- It is a bit faster than LZ4_decompress_safe().
- However, it does not provide any protection against intentionally modified data stream (malicious input).
- Use this function in trusted environment only (data to decode comes from a trusted source).
+ However, it does not provide any protection against malicious input.
+ It also doesn't know 'src' size, and implies it's >= compressed size.
+ 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> This function decompress a compressed block of size 'srcSize' at position 'src'
into destination buffer 'dst' of size 'dstCapacity'.
The function will decompress a minimum of 'targetOutputSize' bytes, and stop after that.
- However, it's not accurate, and may write more than 'targetOutputSize' (but <= dstCapacity).
+ However, it's not accurate, and may write more than 'targetOutputSize' (but always <= dstCapacity).
@return : the number of bytes decoded in the destination buffer (necessarily <= dstCapacity)
- Note : this number can be < 'targetOutputSize' should the compressed block contain less data.
- Always control how many bytes were decoded.
- If the source stream is detected malformed, the function will stop decoding and return a negative result.
- This function never writes outside of output buffer, and never reads outside of input buffer. It is therefore protected against malicious data packets.
+ Note : this number can also be < targetOutputSize, if compressed block contains less data.
+ Therefore, always control how many bytes were decoded.
+ If source stream is detected malformed, function returns a negative result.
+ This function is protected against malicious data packets.
</p></pre><BR>
<a name="Chapter6"></a><h2>Streaming Compression Functions</h2><pre></pre>
@@ -175,7 +176,8 @@ int LZ4_freeStream (LZ4_stream_t* streamPtr);
'dst' buffer must be already allocated.
If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster.
- Important : Up to 64KB of previously compressed data is assumed to remain present and unmodified in memory !
+ Important : The previous 64KB of compressed data is assumed to remain preset and unmodified in memory!
+ If less than 64KB has been compressed all the data must be present.
Special 1 : If input buffer is a double-buffer, it can have any size, including < 64 KB.
Special 2 : If input buffer is a ring-buffer, it can have any size, including < 64 KB.
@@ -215,7 +217,8 @@ int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecode, const ch
</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 accept one block at a time.
- Previously decoded blocks *must* remain available at the memory position where they were decoded (up to 64 KB).
+ The last 64KB of previously decoded data *must* remain available and unmodified at the memory position where they were decoded.
+ If less than 64KB of data has been decoded all the data must be present.
Special : if application sets a ring buffer for decompression, it must respect one of the following conditions :
- Exactly same size as encoding buffer, with same update rule (block boundaries at same positions)
@@ -311,11 +314,9 @@ union LZ4_streamDecode_u {
# define LZ4_DEPRECATED(message) </b>/* disable deprecation warnings */<b>
#else
# define LZ4_GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
-# if defined(__clang__) </b>/* clang doesn't handle mixed C++11 and CNU attributes */<b>
-# define LZ4_DEPRECATED(message) __attribute__((deprecated(message)))
-# elif defined (__cplusplus) && (__cplusplus >= 201402) </b>/* C++14 or greater */<b>
+# if defined (__cplusplus) && (__cplusplus >= 201402) </b>/* C++14 or greater */<b>
# define LZ4_DEPRECATED(message) [[deprecated(message)]]
-# elif (LZ4_GCC_VERSION >= 405)
+# elif (LZ4_GCC_VERSION >= 405) || defined(__clang__)
# define LZ4_DEPRECATED(message) __attribute__((deprecated(message)))
# elif (LZ4_GCC_VERSION >= 301)
# define LZ4_DEPRECATED(message) __attribute__((deprecated))