140 lines
7.1 KiB
C
140 lines
7.1 KiB
C
#ifndef SEEKABLE_H
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#define SEEKABLE_H
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#if defined (__cplusplus)
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extern "C" {
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#endif
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static const unsigned ZSTD_seekTableFooterSize = 9;
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#define ZSTD_SEEKABLE_MAGICNUMBER 0x8F92EAB1
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#define ZSTD_SEEKABLE_MAXFRAMES 0x8000000U
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/* Limit the maximum size to avoid any potential issues storing the compressed size */
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#define ZSTD_SEEKABLE_MAX_FRAME_DECOMPRESSED_SIZE 0x80000000U
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/*-****************************************************************************
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* Seekable Format
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*
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* The seekable format splits the compressed data into a series of "frames",
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* each compressed individually so that decompression of a section in the
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* middle of an archive only requires zstd to decompress at most a frame's
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* worth of extra data, instead of the entire archive.
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******************************************************************************/
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typedef struct ZSTD_seekable_CStream_s ZSTD_seekable_CStream;
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typedef struct ZSTD_seekable_DStream_s ZSTD_seekable_DStream;
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/*-****************************************************************************
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* Seekable compression - HowTo
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* A ZSTD_seekable_CStream object is required to tracking streaming operation.
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* Use ZSTD_seekable_createCStream() and ZSTD_seekable_freeCStream() to create/
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* release resources.
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*
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* Streaming objects are reusable to avoid allocation and deallocation,
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* to start a new compression operation call ZSTD_seekable_initCStream() on the
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* compressor.
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*
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* Data streamed to the seekable compressor will automatically be split into
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* frames of size `maxFrameSize` (provided in ZSTD_seekable_initCStream()),
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* or if none is provided, will be cut off whenever ZSTD_seekable_endFrame() is
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* called or when the default maximum frame size (2GB) is reached.
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*
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* Use ZSTD_seekable_initCStream() to initialize a ZSTD_seekable_CStream object
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* for a new compression operation.
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* `maxFrameSize` indicates the size at which to automatically start a new
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* seekable frame. `maxFrameSize == 0` implies the default maximum size.
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* `checksumFlag` indicates whether or not the seek table should include frame
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* checksums on the uncompressed data for verification.
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* @return : a size hint for input to provide for compression, or an error code
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* checkable with ZSTD_isError()
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*
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* Use ZSTD_seekable_compressStream() repetitively to consume input stream.
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* The function will automatically update both `pos` fields.
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* Note that it may not consume the entire input, in which case `pos < size`,
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* and it's up to the caller to present again remaining data.
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* @return : a size hint, preferred nb of bytes to use as input for next
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* function call or an error code, which can be tested using
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* ZSTD_isError().
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* Note 1 : it's just a hint, to help latency a little, any other
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* value will work fine.
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*
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* At any time, call ZSTD_seekable_endFrame() to end the current frame and
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* start a new one.
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*
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* ZSTD_seekable_endStream() will end the current frame, and then write the seek
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* table so that decompressors can efficiently find compressed frames.
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* ZSTD_seekable_endStream() may return a number > 0 if it was unable to flush
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* all the necessary data to `output`. In this case, it should be called again
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* until all remaining data is flushed out and 0 is returned.
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******************************************************************************/
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/*===== Seekable compressor management =====*/
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ZSTDLIB_API ZSTD_seekable_CStream* ZSTD_seekable_createCStream(void);
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ZSTDLIB_API size_t ZSTD_seekable_freeCStream(ZSTD_seekable_CStream* zcs);
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/*===== Seekable compression functions =====*/
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ZSTDLIB_API size_t ZSTD_seekable_initCStream(ZSTD_seekable_CStream* zcs, int compressionLevel, int checksumFlag, unsigned maxFrameSize);
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ZSTDLIB_API size_t ZSTD_seekable_compressStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
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ZSTDLIB_API size_t ZSTD_seekable_endFrame(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
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ZSTDLIB_API size_t ZSTD_seekable_endStream(ZSTD_seekable_CStream* zcs, ZSTD_outBuffer* output);
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/*-****************************************************************************
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* Seekable decompression - HowTo
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* A ZSTD_seekable_DStream object is required to tracking streaming operation.
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* Use ZSTD_seekable_createDStream() and ZSTD_seekable_freeDStream() to create/
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* release resources.
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*
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* Streaming objects are reusable to avoid allocation and deallocation,
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* to start a new compression operation call ZSTD_seekable_initDStream() on the
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* compressor.
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*
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* Use ZSTD_seekable_loadSeekTable() to load the seek table from a file.
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* `src` should point to a block of data read from the end of the file,
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* i.e. `src + srcSize` should always be the end of the file.
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* @return : 0 if the table was loaded successfully, or if `srcSize` was too
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* small, a size hint for how much data to provide.
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* An error code may also be returned, checkable with ZSTD_isError()
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*
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* Use ZSTD_seekable_initDStream to prepare for a new decompression operation
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* using the seektable loaded with ZSTD_seekable_loadSeekTable().
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* Data in the range [rangeStart, rangeEnd) will be decompressed.
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*
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* Call ZSTD_seekable_decompressStream() repetitively to consume input stream.
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* @return : There are a number of possible return codes for this function
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* - 0, the decompression operation has completed.
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* - An error code checkable with ZSTD_isError
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* + If this error code is ZSTD_error_needSeek, the user should seek
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* to the file position provided by ZSTD_seekable_getSeekOffset()
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* and indicate this to the stream with
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* ZSTD_seekable_updateOffset(), before resuming decompression
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* + Otherwise, this is a regular decompression error and the input
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* file is likely corrupted or the API was incorrectly used.
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* - A size hint, the preferred nb of bytes to provide as input to the
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* next function call to improve latency.
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*
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* ZSTD_seekable_getSeekOffset() and ZSTD_seekable_updateOffset() are helper
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* functions to indicate where the user should seek their file stream to, when
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* a different position is required to continue decompression.
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* Note that ZSTD_seekable_updateOffset will error if given an offset other
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* than the one requested from ZSTD_seekable_getSeekOffset().
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******************************************************************************/
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/*===== Seekable decompressor management =====*/
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ZSTDLIB_API ZSTD_seekable_DStream* ZSTD_seekable_createDStream(void);
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ZSTDLIB_API size_t ZSTD_seekable_freeDStream(ZSTD_seekable_DStream* zds);
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/*===== Seekable decompression functions =====*/
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ZSTDLIB_API size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable_DStream* zds, const void* src, size_t srcSize);
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ZSTDLIB_API size_t ZSTD_seekable_initDStream(ZSTD_seekable_DStream* zds, unsigned long long rangeStart, unsigned long long rangeEnd);
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ZSTDLIB_API size_t ZSTD_seekable_decompressStream(ZSTD_seekable_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
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ZSTDLIB_API unsigned long long ZSTD_seekable_getSeekOffset(ZSTD_seekable_DStream* zds);
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ZSTDLIB_API size_t ZSTD_seekable_updateOffset(ZSTD_seekable_DStream* zds, unsigned long long offset);
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#if defined (__cplusplus)
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}
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#endif
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#endif
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