diff options
Diffstat (limited to 'lz4.h')
| -rw-r--r-- | lz4.h | 34 |
1 files changed, 20 insertions, 14 deletions
@@ -43,17 +43,18 @@ int LZ4_uncompress (const char* source, char* dest, int osize); /*
LZ4_compress() :
- return : the number of bytes in compressed buffer dest
+ return : the number of bytes written in buffer dest
+ or 0 if the compression fails (if LZ4_COMPRESSMIN is set)
note : destination buffer must be already allocated.
- To avoid any problem, size it to handle worst cases situations (input data not compressible)
- Worst case size is : "inputsize + 0.4%", with "0.4%" being at least 8 bytes.
+ destination buffer must be sized to handle worst cases situations (input data not compressible)
+ worst case size evaluation is provided by function LZ4_compressBound()
LZ4_uncompress() :
osize : is the output size, therefore the original size
return : the number of bytes read in the source buffer
If the source stream is malformed, the function will stop decoding and return a negative result, indicating the byte position of the faulty instruction
- This version never writes beyond dest + osize, and is therefore protected against malicious data packets
- note 2 : destination buffer must be already allocated
+ This function never writes beyond dest + osize, and is therefore protected against malicious data packets
+ note : destination buffer must be already allocated
*/
@@ -65,11 +66,12 @@ int LZ4_compressBound(int isize); /*
LZ4_compressBound() :
- Provides the maximum size that LZ4 may output in a "worst case" scenario, for memory allocation of output buffer.
+ Provides the maximum size that LZ4 may output in a "worst case" scenario (input data not compressible)
+ primarily useful for memory allocation of output buffer.
isize : is the input size
- return : maximum size that LZ4 may output in a "worst case" scenario
- note : this function is limited by "int" range
+ return : maximum output size in a "worst case" scenario
+ note : this function is limited by "int" range (2^31-1)
*/
@@ -81,25 +83,29 @@ LZ4_uncompress_unknownOutputSize() : maxOutputSize : is the size of the destination buffer (which must be already allocated)
return : the number of bytes decoded in the destination buffer (necessarily <= maxOutputSize)
If the source stream is malformed, the function will stop decoding and return a negative result, indicating the byte position of the faulty instruction
- This version never writes beyond dest + maxOutputSize, and is therefore protected against malicious data packets
- note : This version is a bit slower than LZ4_uncompress
+ This function never writes beyond dest + maxOutputSize, and is therefore protected against malicious data packets
+ note : This version is slightly slower than LZ4_uncompress()
*/
int LZ4_compressCtx(void** ctx, const char* source, char* dest, int isize);
+int LZ4_compress64kCtx(void** ctx, const char* source, char* dest, int isize);
/*
LZ4_compressCtx() :
This function explicitly handles the CTX memory structure.
- It avoids allocating/deallocating memory between each call, improving performance when malloc is time-consuming.
- Note : when memory is allocated into the stack (default mode), there is no "malloc" penalty.
- Therefore, this function is mostly useful when memory is allocated into the heap (it requires increasing HASH_LOG value beyond STACK_LIMIT)
+ It avoids allocating/deallocating memory between each call, improving performance when malloc is heavily invoked.
+ This function is only useful when memory is allocated into the heap (HASH_LOG value beyond STACK_LIMIT)
+ Performance difference will be noticeable only when repetitively calling the compression function over many small segments.
+ Note : by default, memory is allocated into the stack, therefore "malloc" is not invoked.
+LZ4_compress64kCtx() :
+ Same as LZ4_compressCtx(), but specific to small inputs (<64KB).
+ isize *Must* be <64KB, otherwise the output will be corrupted.
On first call : provide a *ctx=NULL; It will be automatically allocated.
On next calls : reuse the same ctx pointer.
Use different pointers for different threads when doing multi-threading.
- note : performance difference is small, mostly noticeable in HeapMode when repetitively calling the compression function over many small segments.
*/
|