Merge pull request #575 from lz4/apiDoc

unpublish static-only functions

2 files changed, 92 insertions, 80 deletions

diff --git a/lib/README.md b/lib/README.md
index 7082fe3..8b3b424 100644
--- a/lib/README.md
+++ b/lib/README.md
@@ -16,10 +16,10 @@ They generate and decode data using [LZ4 block format].
 For more compression ratio at the cost of compression speed,
 the High Compression variant called **lz4hc** is available.
 Add files **`lz4hc.c`** and **`lz4hc.h`**.
-The variant still depends on regular `lib/lz4.*` source files.
+This variant also depends on regular `lib/lz4.*` source files.
 
 
-#### Frame variant, for interoperability
+#### Frame support, for interoperability
 
 In order to produce compressed data compatible with `lz4` command line utility,
 it's necessary to encode lz4-compressed blocks using the [official interoperable frame format].
@@ -32,9 +32,14 @@ So it's necessary to include all `*.c` and `*.h` files present in `/lib`.
 
 #### Advanced / Experimental API
 
-A complex API defined in `lz4frame_static.h` contains definitions
-which are not guaranteed to remain stable in future versions.
-As a consequence, it must be used with static linking ***only***.
+Definitions which are not guaranteed to remain stable in future versions,
+are protected behind macros, such as `LZ4_STATIC_LINKING_ONLY`.
+As the name implies, these definitions can only be invoked
+in the context of static linking ***only***.
+Otherwise, dependent application may fail on API or ABI break in the future.
+The associated symbols are also not present in dynamic library by default.
+Should they be nonetheless needed, it's possible to force their publication
+by using build macro `LZ4_PUBLISH_STATIC_FUNCTIONS`.
 
 
 #### Windows : using MinGW+MSYS to create DLL
@@ -48,7 +53,7 @@ The dynamic library has to be added to linking options.
 It means that if a project that uses LZ4 consists of a single `test-dll.c`
 file it should be linked with `dll\liblz4.dll`. For example:
 ```
-    gcc $(CFLAGS) -Iinclude/ test-dll.c -o test-dll dll\liblz4.dll
+    $(CC) $(CFLAGS) -Iinclude/ test-dll.c -o test-dll dll\liblz4.dll
 ```
 The compiled executable will require LZ4 DLL which is available at `dll\liblz4.dll`.
 
diff --git a/lib/lz4.h b/lib/lz4.h
index 059ef7c..6d67bfc 100644
--- a/lib/lz4.h
+++ b/lib/lz4.h
@@ -103,7 +103,7 @@ extern "C" {
 #define LZ4_VERSION_STRING LZ4_EXPAND_AND_QUOTE(LZ4_LIB_VERSION)
 
 LZ4LIB_API int LZ4_versionNumber (void);  /**< library version number; useful to check dll version */
-LZ4LIB_API const char* LZ4_versionString (void);   /**< library version string; unseful to check dll version */
+LZ4LIB_API const char* LZ4_versionString (void);   /**< library version string; useful to check dll version */
 
 
 /*-************************************
@@ -112,14 +112,15 @@ LZ4LIB_API const char* LZ4_versionString (void);   /**< library version string;
 /*!
  * LZ4_MEMORY_USAGE :
  * 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 may improve speed, thanks to cache effect
+ * Increasing memory usage improves compression ratio.
+ * Reduced memory usage may improve speed, thanks to better cache locality.
  * Default value is 14, for 16KB, which nicely fits into Intel x86 L1 cache
  */
 #ifndef LZ4_MEMORY_USAGE
 # define LZ4_MEMORY_USAGE 14
 #endif
 
+
 /*-************************************
 *  Simple Functions
 **************************************/
@@ -130,21 +131,22 @@ LZ4LIB_API const char* LZ4_versionString (void);   /**< library version string;
     It also runs faster, so it's a recommended setting.
     If the function cannot compress 'src' into a more limited 'dst' budget,
     compression stops *immediately*, and the function result is zero.
-    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).
+    In which case, 'dst' content is undefined (invalid).
         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 */
+       @return  : the number of bytes written into buffer 'dst' (necessarily <= dstCapacity)
+                  or 0 if compression fails
+    Note : This function is protected against buffer overflow scenarios (never writes outside 'dst' buffer, nor read outside 'source' buffer).
+*/
 LZ4LIB_API int LZ4_compress_default(const char* src, char* dst, int srcSize, int dstCapacity);
 
 /*! LZ4_decompress_safe() :
     compressedSize : is the exact complete size of the compressed block.
     dstCapacity : is the size of destination buffer, which must be already allocated.
-    return : the number of bytes decompressed into destination buffer (necessarily <= dstCapacity)
+   @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 malicious data packets.
+    Note : This function is protected against malicious data packets (never writes outside 'dst' buffer, nor read outside 'source' buffer).
 */
 LZ4LIB_API int LZ4_decompress_safe (const char* src, char* dst, int compressedSize, int dstCapacity);
 
@@ -155,8 +157,7 @@ LZ4LIB_API int LZ4_decompress_safe (const char* src, char* dst, int compressedSi
 #define LZ4_MAX_INPUT_SIZE        0x7E000000   /* 2 113 929 216 bytes */
 #define LZ4_COMPRESSBOUND(isize)  ((unsigned)(isize) > (unsigned)LZ4_MAX_INPUT_SIZE ? 0 : (isize) + ((isize)/255) + 16)
 
-/*!
-LZ4_compressBound() :
+/*! LZ4_compressBound() :
     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).
@@ -167,8 +168,7 @@ LZ4_compressBound() :
 */
 LZ4LIB_API int LZ4_compressBound(int inputSize);
 
-/*!
-LZ4_compress_fast() :
+/*! LZ4_compress_fast() :
     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.
@@ -178,13 +178,12 @@ LZ4_compress_fast() :
 LZ4LIB_API int LZ4_compress_fast (const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 
 
-/*!
-LZ4_compress_fast_extState() :
-    Same compression function, just using an externally allocated memory space to store compression state.
-    Use LZ4_sizeofState() to know how much memory must be allocated,
-    and allocate it on 8-bytes boundaries (using malloc() typically).
-    Then, provide this buffer as 'void* state' to compression function.
-*/
+/*! LZ4_compress_fast_extState() :
+ *  Same as LZ4_compress_fast(), using an externally allocated memory space for its state.
+ *  Use LZ4_sizeofState() to know how much memory must be allocated,
+ *  and allocate it on 8-bytes boundaries (using `malloc()` typically).
+ *  Then, provide this buffer as `void* state` to compression function.
+ */
 LZ4LIB_API int LZ4_sizeofState(void);
 LZ4LIB_API int LZ4_compress_fast_extState (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 
@@ -210,7 +209,7 @@ LZ4LIB_API int LZ4_compress_destSize (const char* src, char* dst, int* srcSizePt
  *  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 only remaining specificity is that it can decompress data without knowing its compressed size.
+ *  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.
@@ -257,10 +256,6 @@ LZ4LIB_API int LZ4_decompress_safe_partial (const char* src, char* dst, int srcS
 ***********************************************/
 typedef union LZ4_stream_u LZ4_stream_t;  /* incomplete type (defined later) */
 
-/*! LZ4_createStream() and LZ4_freeStream() :
- *  LZ4_createStream() will allocate and initialize an `LZ4_stream_t` structure.
- *  LZ4_freeStream() releases its memory.
- */
 LZ4LIB_API LZ4_stream_t* LZ4_createStream(void);
 LZ4LIB_API int           LZ4_freeStream (LZ4_stream_t* streamPtr);
 
@@ -280,7 +275,7 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in
 
 /*! LZ4_compress_fast_continue() :
  *  Compress 'src' content using data from previously compressed blocks, for better compression ratio.
- *  'dst' buffer must be already allocated.
+ * 'dst' buffer must be already allocated.
  *  If dstCapacity >= LZ4_compressBound(srcSize), compression is guaranteed to succeed, and runs faster.
  *
  * @return : size of compressed block
@@ -288,10 +283,10 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in
  *
  *  Note 1 : Each invocation to LZ4_compress_fast_continue() generates a new block.
  *           Each block has precise boundaries.
+ *           Each block must be decompressed separately, calling LZ4_decompress_*() with relevant metadata.
  *           It's not possible to append blocks together and expect a single invocation of LZ4_decompress_*() to decompress them together.
- *           Each block must be decompressed separately, calling LZ4_decompress_*() with associated metadata.
  *
- *  Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory!
+ *  Note 2 : The previous 64KB of source data is __assumed__ to remain present, unmodified, at same address in memory !
  *
  *  Note 3 : When input is structured as a double-buffer, each buffer can have any size, including < 64 KB.
  *           Make sure that buffers are separated, by at least one byte.
@@ -299,7 +294,7 @@ LZ4LIB_API int LZ4_loadDict (LZ4_stream_t* streamPtr, const char* dictionary, in
  *
  *  Note 4 : If input buffer is a ring-buffer, it can have any size, including < 64 KB.
  *
- *  Note 5 : After an error, the stream status is invalid, it can only be reset or freed.
+ *  Note 5 : After an error, the stream status is undefined (invalid), it can only be reset or freed.
  */
 LZ4LIB_API int LZ4_compress_fast_continue (LZ4_stream_t* streamPtr, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 
@@ -335,7 +330,7 @@ LZ4LIB_API int                 LZ4_freeStreamDecode (LZ4_streamDecode_t* LZ4_str
  */
 LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const char* dictionary, int dictSize);
 
-/*! LZ4_decoderRingBufferSize() : v1.8.2
+/*! LZ4_decoderRingBufferSize() : v1.8.2+
  *  Note : in a ring buffer scenario (optional),
  *  blocks are presumed decompressed next to each other
  *  up to the moment there is not enough remaining space for next block (remainingSize < maxBlockSize),
@@ -347,7 +342,7 @@ LZ4LIB_API int LZ4_setStreamDecode (LZ4_streamDecode_t* LZ4_streamDecode, const
  *           or 0 if there is an error (invalid maxBlockSize).
  */
 LZ4LIB_API int LZ4_decoderRingBufferSize(int maxBlockSize);
-#define LZ4_DECODER_RING_BUFFER_SIZE(mbs) (65536 + 14 + (mbs))  /* for static allocation; mbs presumed valid */
+#define LZ4_DECODER_RING_BUFFER_SIZE(maxBlockSize) (65536 + 14 + (maxBlockSize))  /* for static allocation; maxBlockSize presumed valid */
 
 /*! LZ4_decompress_*_continue() :
  *  These decoding functions allow decompression of consecutive blocks in "streaming" mode.
@@ -382,7 +377,9 @@ LZ4LIB_API int LZ4_decompress_fast_continue (LZ4_streamDecode_t* LZ4_streamDecod
  *  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.
- *  Dictionary is presumed stable : it must remain accessible and unmodified during next decompression.
+ *  Dictionary is presumed stable : it must remain accessible and unmodified during decompression.
+ *  Performance tip : Decompression speed can be substantially increased
+ *                    when dst == dictStart + dictSize.
  */
 LZ4LIB_API int LZ4_decompress_safe_usingDict (const char* src, char* dst, int srcSize, int dstCapcity, const char* dictStart, int dictSize);
 LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int originalSize, const char* dictStart, int dictSize);
@@ -395,29 +392,41 @@ LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int or
 /*-************************************
  *  Unstable declarations
  **************************************
- * Declarations in this section should be considered unstable.
- * Use at your own peril, etc., etc.
- * They may be removed in the future.
- * Their signatures may change.
+ * Declarations in this section must be considered unstable.
+ * Their signatures may change, or may be removed in the future.
+ * They are therefore only safe to depend on
+ * when the caller is statically linked against the library.
+ * To access their declarations, define LZ4_STATIC_LINKING_ONLY.
  **************************************/
 
 #ifdef LZ4_STATIC_LINKING_ONLY
 
+/* By default, symbols in this section aren't published into shared/dynamic libraries.
+ * You can override this behavior and force them to be published
+ * by defining LZ4_PUBLISH_STATIC_FUNCTIONS.
+ * Use at your own risk.
+ */
+
+#ifdef LZ4_PUBLISH_STATIC_FUNCTIONS
+#define LZ4LIB_STATIC_API LZ4LIB_API
+#else
+#define LZ4LIB_STATIC_API
+#endif
+
 /*! LZ4_resetStream_fast() :
  *  Use this, like LZ4_resetStream(), to prepare a context for a new chain of
  *  calls to a streaming API (e.g., LZ4_compress_fast_continue()).
  *
  *  Note:
- *  Using this in advance of a non- streaming-compression function is redundant,
- *  and potentially bad for performance, since they all perform their own custom
- *  reset internally.
+ *  Using this in advance of a non-streaming-compression function is redundant,
+ *  since they all perform their own custom reset internally.
  *
  *  Differences from LZ4_resetStream():
  *  When an LZ4_stream_t is known to be in a internally coherent state,
- *  it can often be prepared for a new compression with almost no work, only
- *  sometimes falling back to the full, expensive reset that is always required
- *  when the stream is in an indeterminate state (i.e., the reset performed by
- *  LZ4_resetStream()).
+ *  it can often be prepared for a new compression with almost no work,
+ *  only sometimes falling back to the full, expensive reset
+ *  that is always required when the stream is in an indeterminate state
+ *  (i.e., the reset performed by LZ4_resetStream()).
  *
  *  LZ4_streams are guaranteed to be in a valid state when:
  *  - returned from LZ4_createStream()
@@ -434,24 +443,23 @@ LZ4LIB_API int LZ4_decompress_fast_usingDict (const char* src, char* dst, int or
  *  any fastReset or streaming function. It must first be cleansed by the full
  *  LZ4_resetStream().
  */
-LZ4LIB_API void LZ4_resetStream_fast (LZ4_stream_t* streamPtr);
+LZ4LIB_STATIC_API void LZ4_resetStream_fast (LZ4_stream_t* streamPtr);
 
 /*! LZ4_compress_fast_extState_fastReset() :
  *  A variant of LZ4_compress_fast_extState().
  *
- *  Using this variant avoids an expensive initialization step. It is only safe
- *  to call if the state buffer is known to be correctly initialized already
- *  (see above comment on LZ4_resetStream_fast() for a definition of "correctly
- *  initialized"). From a high level, the difference is that this function
- *  initializes the provided state with a call to something like
- *  LZ4_resetStream_fast() while LZ4_compress_fast_extState() starts with a
- *  call to LZ4_resetStream().
+ *  Using this variant avoids an expensive initialization step.
+ *  It is only safe to call if the state buffer is known to be correctly initialized already
+ *  (see above comment on LZ4_resetStream_fast() for a definition of "correctly initialized").
+ *  From a high level, the difference is that
+ *  this function initializes the provided state with a call to something like LZ4_resetStream_fast()
+ *  while LZ4_compress_fast_extState() starts with a call to LZ4_resetStream().
  */
-LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
+LZ4LIB_STATIC_API int LZ4_compress_fast_extState_fastReset (void* state, const char* src, char* dst, int srcSize, int dstCapacity, int acceleration);
 
 /*! LZ4_attach_dictionary() :
- *  This is an experimental API that allows for the efficient use of a
- *  static dictionary many times.
+ *  This is an experimental API that allows
+ *  efficient use of a static dictionary many times.
  *
  *  Rather than re-loading the dictionary buffer into a working context before
  *  each compression, or copying a pre-loaded dictionary's LZ4_stream_t into a
@@ -462,8 +470,8 @@ LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* sr
  *  Currently, only streams which have been prepared by LZ4_loadDict() should
  *  be expected to work.
  *
- *  Alternatively, the provided dictionary stream pointer may be NULL, in which
- *  case any existing dictionary stream is unset.
+ *  Alternatively, the provided dictionaryStream may be NULL,
+ *  in which case any existing dictionary stream is unset.
  *
  *  If a dictionary is provided, it replaces any pre-existing stream history.
  *  The dictionary contents are the only history that can be referenced and
@@ -475,16 +483,17 @@ LZ4LIB_API int LZ4_compress_fast_extState_fastReset (void* state, const char* sr
  *  stream (and source buffer) must remain in-place / accessible / unchanged
  *  through the completion of the first compression call on the stream.
  */
-LZ4LIB_API void LZ4_attach_dictionary(LZ4_stream_t *working_stream, const LZ4_stream_t *dictionary_stream);
+LZ4LIB_STATIC_API void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream);
 
 #endif
 
+
 /*-************************************
  *  Private definitions
  **************************************
- * Do not use these definitions.
- * They are exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`.
- * Using these definitions will expose code to API and/or ABI break in future versions of the library.
+ * Do not use these definitions directly.
+ * They are only exposed to allow static allocation of `LZ4_stream_t` and `LZ4_streamDecode_t`.
+ * Accessing members will expose code to API and/or ABI break in future versions of the library.
  **************************************/
 #define LZ4_HASHLOG   (LZ4_MEMORY_USAGE-2)
 #define LZ4_HASHTABLESIZE (1 << LZ4_MEMORY_USAGE)
@@ -533,13 +542,12 @@ typedef struct {
 
 #endif
 
-/*!
- * LZ4_stream_t :
- * information structure to track an LZ4 stream.
- * init this structure before first use.
- * note : only use in association with static linking !
- *        this definition is not API/ABI safe,
- *        it may change in a future version !
+/*! LZ4_stream_t :
+ *  information structure to track an LZ4 stream.
+ *  init this structure with LZ4_resetStream() before first use.
+ *  note : only use in association with static linking !
+ *         this definition is not API/ABI safe,
+ *         it may change in a future version !
  */
 #define LZ4_STREAMSIZE_U64 ((1 << (LZ4_MEMORY_USAGE-3)) + 4)
 #define LZ4_STREAMSIZE     (LZ4_STREAMSIZE_U64 * sizeof(unsigned long long))
@@ -549,13 +557,12 @@ union LZ4_stream_u {
 } ;  /* previously typedef'd to LZ4_stream_t */
 
 
-/*!
- * LZ4_streamDecode_t :
- * information structure to track an LZ4 stream during decompression.
- * init this structure  using LZ4_setStreamDecode (or memset()) before first use
- * note : only use in association with static linking !
- *        this definition is not API/ABI safe,
- *        and may change in a future version !
+/*! LZ4_streamDecode_t :
+ *  information structure to track an LZ4 stream during decompression.
+ *  init this structure  using LZ4_setStreamDecode() before first use.
+ *  note : only use in association with static linking !
+ *         this definition is not API/ABI safe,
+ *         and may change in a future version !
  */
 #define LZ4_STREAMDECODESIZE_U64  4
 #define LZ4_STREAMDECODESIZE     (LZ4_STREAMDECODESIZE_U64 * sizeof(unsigned long long))