lz4: Revert "lz4: remove unused functions"

- This reverts commit 9f4c0c41c6d2 as EROFS uses LZ4_decompress_safe_partial(). Signed-off-by: Cyber Knight <cyberknight755@gmail.com> Signed-off-by: azrim <mirzaspc@gmail.com>
2025-02-20 11:45:48 +08:00 · 2022-05-03 16:15:19 -04:00 · 2022-05-03 16:15:19 -04:00 · 607eff5412
commit 607eff5412
parent 90e7e976f1
4 changed files with 1141 additions and 6 deletions
--- a/include/linux/lz4.h
+++ b/include/linux/lz4.h
@ -133,6 +133,23 @@ typedef union {
 	LZ4HC_CCtx_internal internal_donotuse;
 } LZ4_streamHC_t;

+/*
+ * LZ4_streamDecode_t - information structure to track an
+ *	LZ4 stream during decompression.
+ *
+ * init this structure using LZ4_setStreamDecode (or memset()) before first use
+ */
+typedef struct {
+	const uint8_t *externalDict;
+	size_t extDictSize;
+	const uint8_t *prefixEnd;
+	size_t prefixSize;
+} LZ4_streamDecode_t_internal;
+typedef union {
+	unsigned long long table[LZ4_STREAMDECODESIZE_U64];
+	LZ4_streamDecode_t_internal internal_donotuse;
+} LZ4_streamDecode_t;
+
 /*-************************************************************************
 *	SIZE OF STATE
 **************************************************************************/
@ -180,6 +197,54 @@ static inline int LZ4_compressBound(size_t isize)
 int LZ4_compress_default(const char *source, char *dest, int inputSize,
 	int maxOutputSize, void *wrkmem);

+/**
+ * LZ4_compress_fast() - As LZ4_compress_default providing an acceleration param
+ * @source: source address of the original data
+ * @dest: output buffer address of the compressed data
+ * @inputSize: size of the input data. Max supported value is LZ4_MAX_INPUT_SIZE
+ * @maxOutputSize: full or partial size of buffer 'dest'
+ *	which must be already allocated
+ * @acceleration: acceleration factor
+ * @wrkmem: address of the working memory.
+ *	This requires 'workmem' of LZ4_MEM_COMPRESS.
+ *
+ * Same as LZ4_compress_default(), but allows to select an "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 LZ4_ACCELERATION_DEFAULT, which is 1.
+ *
+ * Return: Number of bytes written into buffer 'dest'
+ *	(necessarily <= maxOutputSize) or 0 if compression fails
+ */
+static int LZ4_compress_fast(const char *source, char *dest, int inputSize,
+	int maxOutputSize, int acceleration, void *wrkmem);
+
+/**
+ * LZ4_compress_destSize() - Compress as much data as possible
+ *	from source to dest
+ * @source: source address of the original data
+ * @dest: output buffer address of the compressed data
+ * @sourceSizePtr: will be modified to indicate how many bytes where read
+ *	from 'source' to fill 'dest'. New value is necessarily <= old value.
+ * @targetDestSize: Size of buffer 'dest' which must be already allocated
+ * @wrkmem: address of the working memory.
+ *	This requires 'workmem' of LZ4_MEM_COMPRESS.
+ *
+ * Reverse the logic, by compressing as much data as possible
+ * from 'source' buffer into already allocated buffer 'dest'
+ * of size 'targetDestSize'.
+ * This function either compresses the entire 'source' content into 'dest'
+ * if it's large enough, or fill 'dest' buffer completely with as much data as
+ * possible from 'source'.
+ *
+ * Return: Number of bytes written into 'dest' (necessarily <= targetDestSize)
+ *	or 0 if compression fails
+ */
+static int LZ4_compress_destSize(const char *source, char *dest, int *sourceSizePtr,
+	int targetDestSize, void *wrkmem);
+
 /*-************************************************************************
 *	Decompression Functions
 **************************************************************************/
@ -227,6 +292,34 @@ int LZ4_decompress_fast(const char *source, char *dest, int originalSize);
 int LZ4_decompress_safe(const char *source, char *dest, int compressedSize,
 	int maxDecompressedSize);

+/**
+ * LZ4_decompress_safe_partial() - Decompress a block of size 'compressedSize'
+ *	at position 'source' into buffer 'dest'
+ * @source: source address of the compressed data
+ * @dest: output buffer address of the decompressed data which must be
+ *	already allocated
+ * @compressedSize: is the precise full size of the compressed block.
+ * @targetOutputSize: the decompression operation will try
+ *	to stop as soon as 'targetOutputSize' has been reached
+ * @maxDecompressedSize: is the size of destination buffer
+ *
+ * This function decompresses a compressed block of size 'compressedSize'
+ * at position 'source' into destination buffer 'dest'
+ * of size 'maxDecompressedSize'.
+ * The function tries to stop decompressing operation as soon as
+ * 'targetOutputSize' has been reached, reducing decompression time.
+ * This function never writes outside of output buffer,
+ * and never reads outside of input buffer.
+ * It is therefore protected against malicious data packets.
+ *
+ * Return: the number of bytes decoded in the destination buffer
+ *	(necessarily <= maxDecompressedSize)
+ *	or a negative result in case of error
+ *
+ */
+static int LZ4_decompress_safe_partial(const char *source, char *dest,
+	int compressedSize, int targetOutputSize, int maxDecompressedSize);
+
 /*-************************************************************************
 *	LZ4 HC Compression
 **************************************************************************/
@ -253,4 +346,303 @@ int LZ4_decompress_safe(const char *source, char *dest, int compressedSize,
 int LZ4_compress_HC(const char *src, char *dst, int srcSize, int dstCapacity,
 	int compressionLevel, void *wrkmem);

+/**
+ * LZ4_resetStreamHC() - Init an allocated 'LZ4_streamHC_t' structure
+ * @streamHCPtr: pointer to the 'LZ4_streamHC_t' structure
+ * @compressionLevel: Recommended values are between 4 and 9, although any
+ *	value between 1 and LZ4HC_MAX_CLEVEL will work.
+ *	Values >LZ4HC_MAX_CLEVEL behave the same as 16.
+ *
+ * An LZ4_streamHC_t structure can be allocated once
+ * and re-used multiple times.
+ * Use this function to init an allocated `LZ4_streamHC_t` structure
+ * and start a new compression.
+ */
+static void LZ4_resetStreamHC(LZ4_streamHC_t *streamHCPtr, int compressionLevel);
+
+/**
+ * LZ4_loadDictHC() - Load a static dictionary into LZ4_streamHC
+ * @streamHCPtr: pointer to the LZ4HC_stream_t
+ * @dictionary: dictionary to load
+ * @dictSize: size of dictionary
+ *
+ * Use this function to load a static dictionary into LZ4HC_stream.
+ * Any previous data will be forgotten, only 'dictionary'
+ * will remain in memory.
+ * Loading a size of 0 is allowed.
+ *
+ * Return : dictionary size, in bytes (necessarily <= 64 KB)
+ */
+static int	LZ4_loadDictHC(LZ4_streamHC_t *streamHCPtr, const char *dictionary,
+	int dictSize);
+
+/**
+ * LZ4_compress_HC_continue() - Compress 'src' using data from previously
+ *	compressed blocks as a dictionary using the HC algorithm
+ * @streamHCPtr: Pointer to the previous 'LZ4_streamHC_t' structure
+ * @src: source address of the original data
+ * @dst: output buffer address of the compressed data,
+ *	which must be already allocated
+ * @srcSize: size of the input data. Max supported value is LZ4_MAX_INPUT_SIZE
+ * @maxDstSize: full or partial size of buffer 'dest'
+ *	which must be already allocated
+ *
+ * These functions compress data in successive blocks of any size, using
+ * previous blocks as dictionary. One key assumption is that previous
+ * blocks (up to 64 KB) remain read-accessible while
+ * compressing next blocks. There is an exception for ring buffers,
+ * which can be smaller than 64 KB.
+ * Ring buffers scenario is automatically detected and handled by
+ * LZ4_compress_HC_continue().
+ * Before starting compression, state must be properly initialized,
+ * using LZ4_resetStreamHC().
+ * A first "fictional block" can then be designated as
+ * initial dictionary, using LZ4_loadDictHC() (Optional).
+ * Then, use LZ4_compress_HC_continue()
+ * to compress each successive block. Previous memory blocks
+ * (including initial dictionary when present) must remain accessible
+ * and unmodified during compression.
+ * 'dst' buffer should be sized to handle worst case scenarios, using
+ *  LZ4_compressBound(), to ensure operation success.
+ *  If, for any reason, previous data blocks can't be preserved unmodified
+ *  in memory during next compression block,
+ *  you must save it to a safer memory space, using LZ4_saveDictHC().
+ * Return value of LZ4_saveDictHC() is the size of dictionary
+ * effectively saved into 'safeBuffer'.
+ *
+ * Return: Number of bytes written into buffer 'dst'  or 0 if compression fails
+ */
+static int LZ4_compress_HC_continue(LZ4_streamHC_t *streamHCPtr, const char *src,
+	char *dst, int srcSize, int maxDstSize);
+
+/**
+ * LZ4_saveDictHC() - Save static dictionary from LZ4HC_stream
+ * @streamHCPtr: pointer to the 'LZ4HC_stream_t' structure
+ * @safeBuffer: buffer to save dictionary to, must be already allocated
+ * @maxDictSize: size of 'safeBuffer'
+ *
+ * If previously compressed data block is not guaranteed
+ * to remain available at its memory location,
+ * save it into a safer place (char *safeBuffer).
+ * Note : you don't need to call LZ4_loadDictHC() afterwards,
+ * dictionary is immediately usable, you can therefore call
+ * LZ4_compress_HC_continue().
+ *
+ * Return : saved dictionary size in bytes (necessarily <= maxDictSize),
+ *	or 0 if error.
+ */
+static int LZ4_saveDictHC(LZ4_streamHC_t *streamHCPtr, char *safeBuffer,
+	int maxDictSize);
+
+/*-*********************************************
+ *	Streaming Compression Functions
+ ***********************************************/
+
+/**
+ * LZ4_resetStream() - Init an allocated 'LZ4_stream_t' structure
+ * @LZ4_stream: pointer to the 'LZ4_stream_t' structure
+ *
+ * An LZ4_stream_t structure can be allocated once
+ * and re-used multiple times.
+ * Use this function to init an allocated `LZ4_stream_t` structure
+ * and start a new compression.
+ */
+static __always_inline void LZ4_resetStream(LZ4_stream_t *LZ4_stream);
+
+/**
+ * LZ4_loadDict() - Load a static dictionary into LZ4_stream
+ * @streamPtr: pointer to the LZ4_stream_t
+ * @dictionary: dictionary to load
+ * @dictSize: size of dictionary
+ *
+ * Use this function to load a static dictionary into LZ4_stream.
+ * Any previous data will be forgotten, only 'dictionary'
+ * will remain in memory.
+ * Loading a size of 0 is allowed.
+ *
+ * Return : dictionary size, in bytes (necessarily <= 64 KB)
+ */
+int LZ4_loadDict(LZ4_stream_t *streamPtr, const char *dictionary,
+	int dictSize);
+
+/**
+ * LZ4_saveDict() - Save static dictionary from LZ4_stream
+ * @streamPtr: pointer to the 'LZ4_stream_t' structure
+ * @safeBuffer: buffer to save dictionary to, must be already allocated
+ * @dictSize: size of 'safeBuffer'
+ *
+ * If previously compressed data block is not guaranteed
+ * to remain available at its memory location,
+ * save it into a safer place (char *safeBuffer).
+ * Note : you don't need to call LZ4_loadDict() afterwards,
+ * dictionary is immediately usable, you can therefore call
+ * LZ4_compress_fast_continue().
+ *
+ * Return : saved dictionary size in bytes (necessarily <= dictSize),
+ *	or 0 if error.
+ */
+int LZ4_saveDict(LZ4_stream_t *streamPtr, char *safeBuffer, int dictSize);
+
+/**
+ * LZ4_compress_fast_continue() - Compress 'src' using data from previously
+ *	compressed blocks as a dictionary
+ * @streamPtr: Pointer to the previous 'LZ4_stream_t' structure
+ * @src: source address of the original data
+ * @dst: output buffer address of the compressed data,
+ *	which must be already allocated
+ * @srcSize: size of the input data. Max supported value is LZ4_MAX_INPUT_SIZE
+ * @maxDstSize: full or partial size of buffer 'dest'
+ *	which must be already allocated
+ * @acceleration: acceleration factor
+ *
+ * Compress buffer content 'src', using data from previously compressed blocks
+ * as dictionary to improve compression ratio.
+ * Important : Previous data blocks are assumed to still
+ * be present and unmodified !
+ * If maxDstSize >= LZ4_compressBound(srcSize),
+ * compression is guaranteed to succeed, and runs faster.
+ *
+ * Return: Number of bytes written into buffer 'dst'  or 0 if compression fails
+ */
+static int LZ4_compress_fast_continue(LZ4_stream_t *streamPtr, const char *src,
+	char *dst, int srcSize, int maxDstSize, int acceleration);
+
+/**
+ * LZ4_setStreamDecode() - Instruct where to find dictionary
+ * @LZ4_streamDecode: the 'LZ4_streamDecode_t' structure
+ * @dictionary: dictionary to use
+ * @dictSize: size of dictionary
+ *
+ * Use this function to instruct where to find the dictionary.
+ *	Setting a size of 0 is allowed (same effect as reset).
+ *
+ * Return: 1 if OK, 0 if error
+ */
+static int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *dictionary, int dictSize);
+
+/**
+ * LZ4_decompress_safe_continue() - Decompress blocks in streaming mode
+ * @LZ4_streamDecode: the 'LZ4_streamDecode_t' structure
+ * @source: source address of the compressed data
+ * @dest: output buffer address of the uncompressed data
+ *	which must be already allocated
+ * @compressedSize: is the precise full size of the compressed block
+ * @maxDecompressedSize: is the size of 'dest' buffer
+ *
+ * This decoding function allows decompression of multiple blocks
+ * in "streaming" mode.
+ * Previously decoded blocks *must* remain available at the memory position
+ * where they were decoded (up to 64 KB)
+ * In the case of a ring buffers, decoding buffer must be either :
+ *    - Exactly same size as encoding buffer, with same update rule
+ *      (block boundaries at same positions) In which case,
+ *      the decoding & encoding ring buffer can have any size,
+ *      including very small ones ( < 64 KB).
+ *    - Larger than encoding buffer, by a minimum of maxBlockSize more bytes.
+ *      maxBlockSize is implementation dependent.
+ *      It's the maximum size you intend to compress into a single block.
+ *      In which case, encoding and decoding buffers do not need
+ *      to be synchronized, and encoding ring buffer can have any size,
+ *      including small ones ( < 64 KB).
+ *    - _At least_ 64 KB + 8 bytes + maxBlockSize.
+ *      In which case, encoding and decoding buffers do not need to be
+ *      synchronized, and encoding ring buffer can have any size,
+ *      including larger than decoding buffer. W
+ * Whenever these conditions are not possible, save the last 64KB of decoded
+ * data into a safe buffer, and indicate where it is saved
+ * using LZ4_setStreamDecode()
+ *
+ * Return: number of bytes decompressed into destination buffer
+ *	(necessarily <= maxDecompressedSize)
+ *	or a negative result in case of error
+ */
+static int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *source, char *dest, int compressedSize,
+	int maxDecompressedSize);
+
+/**
+ * LZ4_decompress_fast_continue() - Decompress blocks in streaming mode
+ * @LZ4_streamDecode: the 'LZ4_streamDecode_t' structure
+ * @source: source address of the compressed data
+ * @dest: output buffer address of the uncompressed data
+ *	which must be already allocated with 'originalSize' bytes
+ * @originalSize: is the original and therefore uncompressed size
+ *
+ * This decoding function allows decompression of multiple blocks
+ * in "streaming" mode.
+ * Previously decoded blocks *must* remain available at the memory position
+ * where they were decoded (up to 64 KB)
+ * In the case of a ring buffers, decoding buffer must be either :
+ *    - Exactly same size as encoding buffer, with same update rule
+ *      (block boundaries at same positions) In which case,
+ *      the decoding & encoding ring buffer can have any size,
+ *      including very small ones ( < 64 KB).
+ *    - Larger than encoding buffer, by a minimum of maxBlockSize more bytes.
+ *      maxBlockSize is implementation dependent.
+ *      It's the maximum size you intend to compress into a single block.
+ *      In which case, encoding and decoding buffers do not need
+ *      to be synchronized, and encoding ring buffer can have any size,
+ *      including small ones ( < 64 KB).
+ *    - _At least_ 64 KB + 8 bytes + maxBlockSize.
+ *      In which case, encoding and decoding buffers do not need to be
+ *      synchronized, and encoding ring buffer can have any size,
+ *      including larger than decoding buffer. W
+ * Whenever these conditions are not possible, save the last 64KB of decoded
+ * data into a safe buffer, and indicate where it is saved
+ * using LZ4_setStreamDecode()
+ *
+ * Return: number of bytes decompressed into destination buffer
+ *	(necessarily <= maxDecompressedSize)
+ *	or a negative result in case of error
+ */
+static int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *source, char *dest, int originalSize);
+
+/**
+ * LZ4_decompress_safe_usingDict() - Same as LZ4_setStreamDecode()
+ *	followed by LZ4_decompress_safe_continue()
+ * @source: source address of the compressed data
+ * @dest: output buffer address of the uncompressed data
+ *	which must be already allocated
+ * @compressedSize: is the precise full size of the compressed block
+ * @maxDecompressedSize: is the size of 'dest' buffer
+ * @dictStart: pointer to the start of the dictionary in memory
+ * @dictSize: size of dictionary
+ *
+ * This decoding function works the same as
+ * a combination of LZ4_setStreamDecode() followed by
+ * LZ4_decompress_safe_continue()
+ * It is stand-alone, and doesn't need an LZ4_streamDecode_t structure.
+ *
+ * Return: number of bytes decompressed into destination buffer
+ *	(necessarily <= maxDecompressedSize)
+ *	or a negative result in case of error
+ */
+static int LZ4_decompress_safe_usingDict(const char *source, char *dest,
+	int compressedSize, int maxDecompressedSize, const char *dictStart,
+	int dictSize);
+
+/**
+ * LZ4_decompress_fast_usingDict() - Same as LZ4_setStreamDecode()
+ *	followed by LZ4_decompress_fast_continue()
+ * @source: source address of the compressed data
+ * @dest: output buffer address of the uncompressed data
+ *	which must be already allocated with 'originalSize' bytes
+ * @originalSize: is the original and therefore uncompressed size
+ * @dictStart: pointer to the start of the dictionary in memory
+ * @dictSize: size of dictionary
+ *
+ * This decoding function works the same as
+ * a combination of LZ4_setStreamDecode() followed by
+ * LZ4_decompress_fast_continue()
+ * It is stand-alone, and doesn't need an LZ4_streamDecode_t structure.
+ *
+ * Return: number of bytes decompressed into destination buffer
+ *	(necessarily <= maxDecompressedSize)
+ *	or a negative result in case of error
+ */
+static int LZ4_decompress_fast_usingDict(const char *source, char *dest,
+	int originalSize, const char *dictStart, int dictSize);
+
 #endif
--- a/lib/lz4/lz4_compress.c
+++ b/lib/lz4/lz4_compress.c
@ -189,6 +189,9 @@ static FORCE_INLINE int LZ4_compress_generic(
 	const BYTE *base;
 	const BYTE *lowLimit;
 	const BYTE * const lowRefLimit = ip - dictPtr->dictSize;
+	const BYTE * const dictionary = dictPtr->dictionary;
+	const BYTE * const dictEnd = dictionary + dictPtr->dictSize;
+	const size_t dictDelta = dictEnd - (const BYTE *)source;
 	const BYTE *anchor = (const BYTE *) source;
 	const BYTE * const iend = ip + inputSize;
 	const BYTE * const mflimit = iend - MFLIMIT;
@ -216,6 +219,10 @@ static FORCE_INLINE int LZ4_compress_generic(
 		base = (const BYTE *)source - dictPtr->currentOffset;
 		lowLimit = (const BYTE *)source - dictPtr->dictSize;
 		break;
+	case usingExtDict:
+		base = (const BYTE *)source - dictPtr->currentOffset;
+		lowLimit = (const BYTE *)source;
+		break;
 	}

 	if ((tableType == byU16)
@ -259,6 +266,15 @@ static FORCE_INLINE int LZ4_compress_generic(
 					dictPtr->hashTable,
 					tableType, base);

+				if (dict == usingExtDict) {
+					if (match < (const BYTE *)source) {
+						refDelta = dictDelta;
+						lowLimit = dictionary;
+					} else {
+						refDelta = 0;
+						lowLimit = (const BYTE *)source;
+				}	 }
+
 				forwardH = LZ4_hashPosition(forwardIp,
 					tableType);

@ -319,9 +335,34 @@ _next_match:
 		{
 			unsigned int matchCode;

+			if ((dict == usingExtDict)
+				&& (lowLimit == dictionary)) {
+				const BYTE *limit;
+
+				match += refDelta;
+				limit = ip + (dictEnd - match);
+
+				if (limit > matchlimit)
+					limit = matchlimit;
+
+				matchCode = LZ4_count(ip + MINMATCH,
+					match + MINMATCH, limit);
+
+				ip += MINMATCH + matchCode;
+
+				if (ip == limit) {
+					unsigned const int more = LZ4_count(ip,
+						(const BYTE *)source,
+						matchlimit);
+
+					matchCode += more;
+					ip += more;
+				}
+			} else {
 				matchCode = LZ4_count(ip + MINMATCH,
 					match + MINMATCH, matchlimit);
 				ip += MINMATCH + matchCode;
+			}

 			if (outputLimited &&
 				/* Check output buffer overflow */
@ -360,6 +401,16 @@ _next_match:
 		match = LZ4_getPosition(ip, dictPtr->hashTable,
 			tableType, base);

+		if (dict == usingExtDict) {
+			if (match < (const BYTE *)source) {
+				refDelta = dictDelta;
+				lowLimit = dictionary;
+			} else {
+				refDelta = 0;
+				lowLimit = (const BYTE *)source;
+			}
+		}
+
 		LZ4_putPosition(ip, dictPtr->hashTable, tableType, base);

 		if (((dictIssue == dictSmall) ? (match >= lowRefLimit) : 1)
@ -419,7 +470,7 @@ static int LZ4_compress_fast_extState(
 	const tableType_t tableType = byPtr;
 #endif

-	memset(state, 0, sizeof(LZ4_stream_t));
+	LZ4_resetStream((LZ4_stream_t *)state);

 	if (acceleration < 1)
 		acceleration = LZ4_ACCELERATION_DEFAULT;
@ -464,5 +515,423 @@ int LZ4_compress_default(const char *source, char *dest, int inputSize,
 }
 EXPORT_SYMBOL(LZ4_compress_default);

+/*-******************************
+ *	*_destSize() variant
+ ********************************/
+static int LZ4_compress_destSize_generic(
+	LZ4_stream_t_internal * const ctx,
+	const char * const src,
+	char * const dst,
+	int * const srcSizePtr,
+	const int targetDstSize,
+	const tableType_t tableType)
+{
+	const BYTE *ip = (const BYTE *) src;
+	const BYTE *base = (const BYTE *) src;
+	const BYTE *lowLimit = (const BYTE *) src;
+	const BYTE *anchor = ip;
+	const BYTE * const iend = ip + *srcSizePtr;
+	const BYTE * const mflimit = iend - MFLIMIT;
+	const BYTE * const matchlimit = iend - LASTLITERALS;
+
+	BYTE *op = (BYTE *) dst;
+	BYTE * const oend = op + targetDstSize;
+	BYTE * const oMaxLit = op + targetDstSize - 2 /* offset */
+		- 8 /* because 8 + MINMATCH == MFLIMIT */ - 1 /* token */;
+	BYTE * const oMaxMatch = op + targetDstSize
+		- (LASTLITERALS + 1 /* token */);
+	BYTE * const oMaxSeq = oMaxLit - 1 /* token */;
+
+	U32 forwardH;
+
+	/* Init conditions */
+	/* Impossible to store anything */
+	if (targetDstSize < 1)
+		return 0;
+	/* Unsupported input size, too large (or negative) */
+	if ((U32)*srcSizePtr > (U32)LZ4_MAX_INPUT_SIZE)
+		return 0;
+	/* Size too large (not within 64K limit) */
+	if ((tableType == byU16) && (*srcSizePtr >= LZ4_64Klimit))
+		return 0;
+	/* Input too small, no compression (all literals) */
+	if (*srcSizePtr < LZ4_minLength)
+		goto _last_literals;
+
+	/* First Byte */
+	*srcSizePtr = 0;
+	LZ4_putPosition(ip, ctx->hashTable, tableType, base);
+	ip++; forwardH = LZ4_hashPosition(ip, tableType);
+
+	/* Main Loop */
+	for ( ; ; ) {
+		const BYTE *match;
+		BYTE *token;
+
+		/* Find a match */
+		{
+			const BYTE *forwardIp = ip;
+			unsigned int step = 1;
+			unsigned int searchMatchNb = 1 << LZ4_SKIPTRIGGER;
+
+			do {
+				U32 h = forwardH;
+
+				ip = forwardIp;
+				forwardIp += step;
+				step = (searchMatchNb++ >> LZ4_SKIPTRIGGER);
+
+				if (unlikely(forwardIp > mflimit))
+					goto _last_literals;
+
+				match = LZ4_getPositionOnHash(h, ctx->hashTable,
+					tableType, base);
+				forwardH = LZ4_hashPosition(forwardIp,
+					tableType);
+				LZ4_putPositionOnHash(ip, h,
+					ctx->hashTable, tableType,
+					base);
+
+			} while (((tableType == byU16)
+				? 0
+				: (match + MAX_DISTANCE < ip))
+				|| (LZ4_read32(match) != LZ4_read32(ip)));
+		}
+
+		/* Catch up */
+		while ((ip > anchor)
+			&& (match > lowLimit)
+			&& (unlikely(ip[-1] == match[-1]))) {
+			ip--;
+			match--;
+		}
+
+		/* Encode Literal length */
+		{
+			unsigned int litLength = (unsigned int)(ip - anchor);
+
+			token = op++;
+			if (op + ((litLength + 240) / 255)
+				+ litLength > oMaxLit) {
+				/* Not enough space for a last match */
+				op--;
+				goto _last_literals;
+			}
+			if (litLength >= RUN_MASK) {
+				unsigned int len = litLength - RUN_MASK;
+				*token = (RUN_MASK<<ML_BITS);
+				for (; len >= 255; len -= 255)
+					*op++ = 255;
+				*op++ = (BYTE)len;
+			} else
+				*token = (BYTE)(litLength << ML_BITS);
+
+			/* Copy Literals */
+			LZ4_wildCopy(op, anchor, op + litLength);
+			op += litLength;
+		}
+
+_next_match:
+		/* Encode Offset */
+		LZ4_writeLE16(op, (U16)(ip - match)); op += 2;
+
+		/* Encode MatchLength */
+		{
+			size_t matchLength = LZ4_count(ip + MINMATCH,
+			match + MINMATCH, matchlimit);
+
+			if (op + ((matchLength + 240)/255) > oMaxMatch) {
+				/* Match description too long : reduce it */
+				matchLength = (15 - 1) + (oMaxMatch - op) * 255;
+			}
+			ip += MINMATCH + matchLength;
+
+			if (matchLength >= ML_MASK) {
+				*token += ML_MASK;
+				matchLength -= ML_MASK;
+				while (matchLength >= 255) {
+					matchLength -= 255;
+					*op++ = 255;
+				}
+				*op++ = (BYTE)matchLength;
+			} else
+				*token += (BYTE)(matchLength);
+		}
+
+		anchor = ip;
+
+		/* Test end of block */
+		if (ip > mflimit)
+			break;
+		if (op > oMaxSeq)
+			break;
+
+		/* Fill table */
+		LZ4_putPosition(ip - 2, ctx->hashTable, tableType, base);
+
+		/* Test next position */
+		match = LZ4_getPosition(ip, ctx->hashTable, tableType, base);
+		LZ4_putPosition(ip, ctx->hashTable, tableType, base);
+
+		if ((match + MAX_DISTANCE >= ip)
+			&& (LZ4_read32(match) == LZ4_read32(ip))) {
+			token = op++; *token = 0;
+			goto _next_match;
+		}
+
+		/* Prepare next loop */
+		forwardH = LZ4_hashPosition(++ip, tableType);
+	}
+
+_last_literals:
+	/* Encode Last Literals */
+	{
+		size_t lastRunSize = (size_t)(iend - anchor);
+
+		if (op + 1 /* token */
+			+ ((lastRunSize + 240) / 255) /* litLength */
+			+ lastRunSize /* literals */ > oend) {
+			/* adapt lastRunSize to fill 'dst' */
+			lastRunSize	= (oend - op) - 1;
+			lastRunSize -= (lastRunSize + 240) / 255;
+		}
+		ip = anchor + lastRunSize;
+
+		if (lastRunSize >= RUN_MASK) {
+			size_t accumulator = lastRunSize - RUN_MASK;
+
+			*op++ = RUN_MASK << ML_BITS;
+			for (; accumulator >= 255; accumulator -= 255)
+				*op++ = 255;
+			*op++ = (BYTE) accumulator;
+		} else {
+			*op++ = (BYTE)(lastRunSize<<ML_BITS);
+		}
+		memcpy(op, anchor, lastRunSize);
+		op += lastRunSize;
+	}
+
+	/* End */
+	*srcSizePtr = (int) (((const char *)ip) - src);
+	return (int) (((char *)op) - dst);
+}
+
+static int LZ4_compress_destSize_extState(
+	LZ4_stream_t *state,
+	const char *src,
+	char *dst,
+	int *srcSizePtr,
+	int targetDstSize)
+{
+#if LZ4_ARCH64
+	const tableType_t tableType = byU32;
+#else
+	const tableType_t tableType = byPtr;
+#endif
+
+	LZ4_resetStream(state);
+
+	if (targetDstSize >= LZ4_COMPRESSBOUND(*srcSizePtr)) {
+		/* compression success is guaranteed */
+		return LZ4_compress_fast_extState(
+			state, src, dst, *srcSizePtr,
+			targetDstSize, 1);
+	} else {
+		if (*srcSizePtr < LZ4_64Klimit)
+			return LZ4_compress_destSize_generic(
+				&state->internal_donotuse,
+				src, dst, srcSizePtr,
+				targetDstSize, byU16);
+		else
+			return LZ4_compress_destSize_generic(
+				&state->internal_donotuse,
+				src, dst, srcSizePtr,
+				targetDstSize, tableType);
+	}
+}
+
+
+static int LZ4_compress_destSize(
+	const char *src,
+	char *dst,
+	int *srcSizePtr,
+	int targetDstSize,
+	void *wrkmem)
+{
+	return LZ4_compress_destSize_extState(wrkmem, src, dst, srcSizePtr,
+		targetDstSize);
+}
+
+/*-******************************
+ *	Streaming functions
+ ********************************/
+static FORCE_INLINE void LZ4_resetStream(LZ4_stream_t *LZ4_stream)
+{
+	memset(LZ4_stream, 0, sizeof(LZ4_stream_t));
+}
+
+int LZ4_loadDict(LZ4_stream_t *LZ4_dict,
+	const char *dictionary, int dictSize)
+{
+	LZ4_stream_t_internal *dict = &LZ4_dict->internal_donotuse;
+	const BYTE *p = (const BYTE *)dictionary;
+	const BYTE * const dictEnd = p + dictSize;
+	const BYTE *base;
+
+	if ((dict->initCheck)
+		|| (dict->currentOffset > 1 * GB)) {
+		/* Uninitialized structure, or reuse overflow */
+		LZ4_resetStream(LZ4_dict);
+	}
+
+	if (dictSize < (int)HASH_UNIT) {
+		dict->dictionary = NULL;
+		dict->dictSize = 0;
+		return 0;
+	}
+
+	if ((dictEnd - p) > 64 * KB)
+		p = dictEnd - 64 * KB;
+	dict->currentOffset += 64 * KB;
+	base = p - dict->currentOffset;
+	dict->dictionary = p;
+	dict->dictSize = (U32)(dictEnd - p);
+	dict->currentOffset += dict->dictSize;
+
+	while (p <= dictEnd - HASH_UNIT) {
+		LZ4_putPosition(p, dict->hashTable, byU32, base);
+		p += 3;
+	}
+
+	return dict->dictSize;
+}
+EXPORT_SYMBOL(LZ4_loadDict);
+
+static void LZ4_renormDictT(LZ4_stream_t_internal *LZ4_dict,
+	const BYTE *src)
+{
+	if ((LZ4_dict->currentOffset > 0x80000000) ||
+		((uptrval)LZ4_dict->currentOffset > (uptrval)src)) {
+		/* address space overflow */
+		/* rescale hash table */
+		U32 const delta = LZ4_dict->currentOffset - 64 * KB;
+		const BYTE *dictEnd = LZ4_dict->dictionary + LZ4_dict->dictSize;
+		int i;
+
+		for (i = 0; i < LZ4_HASH_SIZE_U32; i++) {
+			if (LZ4_dict->hashTable[i] < delta)
+				LZ4_dict->hashTable[i] = 0;
+			else
+				LZ4_dict->hashTable[i] -= delta;
+		}
+		LZ4_dict->currentOffset = 64 * KB;
+		if (LZ4_dict->dictSize > 64 * KB)
+			LZ4_dict->dictSize = 64 * KB;
+		LZ4_dict->dictionary = dictEnd - LZ4_dict->dictSize;
+	}
+}
+
+int LZ4_saveDict(LZ4_stream_t *LZ4_dict, char *safeBuffer, int dictSize)
+{
+	LZ4_stream_t_internal * const dict = &LZ4_dict->internal_donotuse;
+	const BYTE * const previousDictEnd = dict->dictionary + dict->dictSize;
+
+	if ((U32)dictSize > 64 * KB) {
+		/* useless to define a dictionary > 64 * KB */
+		dictSize = 64 * KB;
+	}
+	if ((U32)dictSize > dict->dictSize)
+		dictSize = dict->dictSize;
+
+	memmove(safeBuffer, previousDictEnd - dictSize, dictSize);
+
+	dict->dictionary = (const BYTE *)safeBuffer;
+	dict->dictSize = (U32)dictSize;
+
+	return dictSize;
+}
+EXPORT_SYMBOL(LZ4_saveDict);
+
+static int LZ4_compress_fast_continue(LZ4_stream_t *LZ4_stream, const char *source,
+	char *dest, int inputSize, int maxOutputSize, int acceleration)
+{
+	LZ4_stream_t_internal *streamPtr = &LZ4_stream->internal_donotuse;
+	const BYTE * const dictEnd = streamPtr->dictionary
+		+ streamPtr->dictSize;
+
+	const BYTE *smallest = (const BYTE *) source;
+
+	if (streamPtr->initCheck) {
+		/* Uninitialized structure detected */
+		return 0;
+	}
+
+	if ((streamPtr->dictSize > 0) && (smallest > dictEnd))
+		smallest = dictEnd;
+
+	LZ4_renormDictT(streamPtr, smallest);
+
+	if (acceleration < 1)
+		acceleration = LZ4_ACCELERATION_DEFAULT;
+
+	/* Check overlapping input/dictionary space */
+	{
+		const BYTE *sourceEnd = (const BYTE *) source + inputSize;
+
+		if ((sourceEnd > streamPtr->dictionary)
+			&& (sourceEnd < dictEnd)) {
+			streamPtr->dictSize = (U32)(dictEnd - sourceEnd);
+			if (streamPtr->dictSize > 64 * KB)
+				streamPtr->dictSize = 64 * KB;
+			if (streamPtr->dictSize < 4)
+				streamPtr->dictSize = 0;
+			streamPtr->dictionary = dictEnd - streamPtr->dictSize;
+		}
+	}
+
+	/* prefix mode : source data follows dictionary */
+	if (dictEnd == (const BYTE *)source) {
+		int result;
+
+		if ((streamPtr->dictSize < 64 * KB) &&
+			(streamPtr->dictSize < streamPtr->currentOffset)) {
+			result = LZ4_compress_generic(
+				streamPtr, source, dest, inputSize,
+				maxOutputSize, limitedOutput, byU32,
+				withPrefix64k, dictSmall, acceleration);
+		} else {
+			result = LZ4_compress_generic(
+				streamPtr, source, dest, inputSize,
+				maxOutputSize, limitedOutput, byU32,
+				withPrefix64k, noDictIssue, acceleration);
+		}
+		streamPtr->dictSize += (U32)inputSize;
+		streamPtr->currentOffset += (U32)inputSize;
+		return result;
+	}
+
+	/* external dictionary mode */
+	{
+		int result;
+
+		if ((streamPtr->dictSize < 64 * KB) &&
+			(streamPtr->dictSize < streamPtr->currentOffset)) {
+			result = LZ4_compress_generic(
+				streamPtr, source, dest, inputSize,
+				maxOutputSize, limitedOutput, byU32,
+				usingExtDict, dictSmall, acceleration);
+		} else {
+			result = LZ4_compress_generic(
+				streamPtr, source, dest, inputSize,
+				maxOutputSize, limitedOutput, byU32,
+				usingExtDict, noDictIssue, acceleration);
+		}
+		streamPtr->dictionary = (const BYTE *)source;
+		streamPtr->dictSize = (U32)inputSize;
+		streamPtr->currentOffset += (U32)inputSize;
+		return result;
+	}
+}
+
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("LZ4 compressor");
--- a/lib/lz4/lz4_decompress.c
+++ b/lib/lz4/lz4_decompress.c
@ -70,7 +70,7 @@ static FORCE_INLINE int LZ4_decompress_generic(
 	 endCondition_directive endOnInput,
 	 /* full, partial */
 	 earlyEnd_directive partialDecoding,
-	 /* noDict, withPrefix64k */
+	 /* noDict, withPrefix64k, usingExtDict */
 	 dict_directive dict,
 	 /* always <= dst, == dst when no prefix */
 	 const BYTE * const lowPrefix,
@ -87,6 +87,7 @@ static FORCE_INLINE int LZ4_decompress_generic(
 	BYTE * const oend = op + outputSize;
 	BYTE *cpy;

+	const BYTE * const dictEnd = (const BYTE *)dictStart + dictSize;
 	static const unsigned int inc32table[8] = {0, 1, 2, 1, 0, 4, 4, 4};
 	static const int dec64table[8] = {0, 0, 0, -1, -4, 1, 2, 3};

@ -328,6 +329,48 @@ _copy_match:

 		length += MINMATCH;

+		/* match starting within external dictionary */
+		if ((dict == usingExtDict) && (match < lowPrefix)) {
+			if (unlikely(op + length > oend - LASTLITERALS)) {
+				/* doesn't respect parsing restriction */
+				if (!partialDecoding)
+					goto _output_error;
+				length = min(length, (size_t)(oend - op));
+			}
+
+			if (length <= (size_t)(lowPrefix - match)) {
+				/*
+				 * match fits entirely within external
+				 * dictionary : just copy
+				 */
+				memmove(op, dictEnd - (lowPrefix - match),
+					length);
+				op += length;
+			} else {
+				/*
+				 * match stretches into both external
+				 * dictionary and current block
+				 */
+				size_t const copySize = (size_t)(lowPrefix - match);
+				size_t const restSize = length - copySize;
+
+				memcpy(op, dictEnd - copySize, copySize);
+				op += copySize;
+				if (restSize > (size_t)(op - lowPrefix)) {
+					/* overlap copy */
+					BYTE * const endOfMatch = op + restSize;
+					const BYTE *copyFrom = lowPrefix;
+
+					while (op < endOfMatch)
+						*op++ = *copyFrom++;
+				} else {
+					memcpy(op, lowPrefix, restSize);
+					op += restSize;
+				}
+			}
+			continue;
+		}
+
 		/* copy match within block */
 		cpy = op + length;

@ -419,6 +462,15 @@ int LZ4_decompress_safe(const char *source, char *dest,
 				      noDict, (BYTE *)dest, NULL, 0);
 }

+static int LZ4_decompress_safe_partial(const char *src, char *dst,
+	int compressedSize, int targetOutputSize, int dstCapacity)
+{
+	dstCapacity = min(targetOutputSize, dstCapacity);
+	return LZ4_decompress_generic(src, dst, compressedSize, dstCapacity,
+				      endOnInputSize, partial_decode,
+				      noDict, (BYTE *)dst, NULL, 0);
+}
+
 int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
 {
 	return LZ4_decompress_generic(source, dest, 0, originalSize,
@ -427,6 +479,228 @@ int LZ4_decompress_fast(const char *source, char *dest, int originalSize)
 				      (BYTE *)dest - 64 * KB, NULL, 0);
 }

+/* ===== Instantiate a few more decoding cases, used more than once. ===== */
+
+static int LZ4_decompress_safe_withPrefix64k(const char *source, char *dest,
+				      int compressedSize, int maxOutputSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      withPrefix64k,
+				      (BYTE *)dest - 64 * KB, NULL, 0);
+}
+
+static int LZ4_decompress_safe_withSmallPrefix(const char *source, char *dest,
+					       int compressedSize,
+					       int maxOutputSize,
+					       size_t prefixSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      noDict,
+				      (BYTE *)dest - prefixSize, NULL, 0);
+}
+
+static int LZ4_decompress_safe_forceExtDict(const char *source, char *dest,
+				     int compressedSize, int maxOutputSize,
+				     const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+static int LZ4_decompress_fast_extDict(const char *source, char *dest,
+				       int originalSize,
+				       const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      0, originalSize,
+				      endOnOutputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+/*
+ * The "double dictionary" mode, for use with e.g. ring buffers: the first part
+ * of the dictionary is passed as prefix, and the second via dictStart + dictSize.
+ * These routines are used only once, in LZ4_decompress_*_continue().
+ */
+static FORCE_INLINE
+int LZ4_decompress_safe_doubleDict(const char *source, char *dest,
+				   int compressedSize, int maxOutputSize,
+				   size_t prefixSize,
+				   const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      compressedSize, maxOutputSize,
+				      endOnInputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest - prefixSize,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+static FORCE_INLINE
+int LZ4_decompress_fast_doubleDict(const char *source, char *dest,
+				   int originalSize, size_t prefixSize,
+				   const void *dictStart, size_t dictSize)
+{
+	return LZ4_decompress_generic(source, dest,
+				      0, originalSize,
+				      endOnOutputSize, decode_full_block,
+				      usingExtDict, (BYTE *)dest - prefixSize,
+				      (const BYTE *)dictStart, dictSize);
+}
+
+/* ===== streaming decompression functions ===== */
+
+static int LZ4_setStreamDecode(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *dictionary, int dictSize)
+{
+	LZ4_streamDecode_t_internal *lz4sd =
+		&LZ4_streamDecode->internal_donotuse;
+
+	lz4sd->prefixSize = (size_t) dictSize;
+	lz4sd->prefixEnd = (const BYTE *) dictionary + dictSize;
+	lz4sd->externalDict = NULL;
+	lz4sd->extDictSize	= 0;
+	return 1;
+}
+
+/*
+ * *_continue() :
+ * These decoding functions allow decompression of multiple blocks
+ * in "streaming" mode.
+ * Previously decoded blocks must still be available at the memory
+ * position where they were decoded.
+ * If it's not possible, save the relevant part of
+ * decoded data into a safe buffer,
+ * and indicate where it stands using LZ4_setStreamDecode()
+ */
+static int LZ4_decompress_safe_continue(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *source, char *dest, int compressedSize, int maxOutputSize)
+{
+	LZ4_streamDecode_t_internal *lz4sd =
+		&LZ4_streamDecode->internal_donotuse;
+	int result;
+
+	if (lz4sd->prefixSize == 0) {
+		/* The first call, no dictionary yet. */
+		assert(lz4sd->extDictSize == 0);
+		result = LZ4_decompress_safe(source, dest,
+			compressedSize, maxOutputSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = result;
+		lz4sd->prefixEnd = (BYTE *)dest + result;
+	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
+		/* They're rolling the current segment. */
+		if (lz4sd->prefixSize >= 64 * KB - 1)
+			result = LZ4_decompress_safe_withPrefix64k(source, dest,
+				compressedSize, maxOutputSize);
+		else if (lz4sd->extDictSize == 0)
+			result = LZ4_decompress_safe_withSmallPrefix(source,
+				dest, compressedSize, maxOutputSize,
+				lz4sd->prefixSize);
+		else
+			result = LZ4_decompress_safe_doubleDict(source, dest,
+				compressedSize, maxOutputSize,
+				lz4sd->prefixSize,
+				lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize += result;
+		lz4sd->prefixEnd  += result;
+	} else {
+		/*
+		 * The buffer wraps around, or they're
+		 * switching to another buffer.
+		 */
+		lz4sd->extDictSize = lz4sd->prefixSize;
+		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
+		result = LZ4_decompress_safe_forceExtDict(source, dest,
+			compressedSize, maxOutputSize,
+			lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = result;
+		lz4sd->prefixEnd  = (BYTE *)dest + result;
+	}
+
+	return result;
+}
+
+static int LZ4_decompress_fast_continue(LZ4_streamDecode_t *LZ4_streamDecode,
+	const char *source, char *dest, int originalSize)
+{
+	LZ4_streamDecode_t_internal *lz4sd = &LZ4_streamDecode->internal_donotuse;
+	int result;
+
+	if (lz4sd->prefixSize == 0) {
+		assert(lz4sd->extDictSize == 0);
+		result = LZ4_decompress_fast(source, dest, originalSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = originalSize;
+		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
+	} else if (lz4sd->prefixEnd == (BYTE *)dest) {
+		if (lz4sd->prefixSize >= 64 * KB - 1 ||
+		    lz4sd->extDictSize == 0)
+			result = LZ4_decompress_fast(source, dest,
+						     originalSize);
+		else
+			result = LZ4_decompress_fast_doubleDict(source, dest,
+				originalSize, lz4sd->prefixSize,
+				lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize += originalSize;
+		lz4sd->prefixEnd  += originalSize;
+	} else {
+		lz4sd->extDictSize = lz4sd->prefixSize;
+		lz4sd->externalDict = lz4sd->prefixEnd - lz4sd->extDictSize;
+		result = LZ4_decompress_fast_extDict(source, dest,
+			originalSize, lz4sd->externalDict, lz4sd->extDictSize);
+		if (result <= 0)
+			return result;
+		lz4sd->prefixSize = originalSize;
+		lz4sd->prefixEnd = (BYTE *)dest + originalSize;
+	}
+	return result;
+}
+
+static int LZ4_decompress_safe_usingDict(const char *source, char *dest,
+				  int compressedSize, int maxOutputSize,
+				  const char *dictStart, int dictSize)
+{
+	if (dictSize == 0)
+		return LZ4_decompress_safe(source, dest,
+					   compressedSize, maxOutputSize);
+	if (dictStart+dictSize == dest) {
+		if (dictSize >= 64 * KB - 1)
+			return LZ4_decompress_safe_withPrefix64k(source, dest,
+				compressedSize, maxOutputSize);
+		return LZ4_decompress_safe_withSmallPrefix(source, dest,
+			compressedSize, maxOutputSize, dictSize);
+	}
+	return LZ4_decompress_safe_forceExtDict(source, dest,
+		compressedSize, maxOutputSize, dictStart, dictSize);
+}
+
+static int LZ4_decompress_fast_usingDict(const char *source, char *dest,
+				  int originalSize,
+				  const char *dictStart, int dictSize)
+{
+	if (dictSize == 0 || dictStart + dictSize == dest)
+		return LZ4_decompress_fast(source, dest, originalSize);
+
+	return LZ4_decompress_fast_extDict(source, dest, originalSize,
+		dictStart, dictSize);
+}
+
 #ifndef STATIC
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_DESCRIPTION("LZ4 decompressor");
--- a/lib/lz4/lz4defs.h
+++ b/lib/lz4/lz4defs.h
@ -234,7 +234,7 @@ static FORCE_INLINE unsigned int LZ4_count(
 typedef enum { noLimit = 0, limitedOutput = 1 } limitedOutput_directive;
 typedef enum { byPtr, byU32, byU16 } tableType_t;

-typedef enum { noDict = 0, withPrefix64k } dict_directive;
+typedef enum { noDict = 0, withPrefix64k, usingExtDict } dict_directive;
 typedef enum { noDictIssue = 0, dictSmall } dictIssue_directive;

 typedef enum { endOnOutputSize = 0, endOnInputSize = 1 } endCondition_directive;