diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h index fb6246a1..007b03df 100644 --- a/lib/common/zstd_internal.h +++ b/lib/common/zstd_internal.h @@ -197,8 +197,8 @@ static void ZSTD_copy8(void* dst, const void* src) { memcpy(dst, src, 8); } static void ZSTD_copy16(void* dst, const void* src) { memcpy(dst, src, 16); } #define COPY16(d,s) { ZSTD_copy16(d,s); d+=16; s+=16; } -#define WILDCOPY_OVERLENGTH 8 -#define VECLEN 16 +#define WILDCOPY_OVERLENGTH 16 +#define WILDCOPY_VECLEN 16 typedef enum { ZSTD_no_overlap, @@ -207,83 +207,58 @@ typedef enum { } ZSTD_overlap_e; /*! ZSTD_wildcopy() : - * custom version of memcpy(), can overwrite up to WILDCOPY_OVERLENGTH bytes (if length==0) */ + * Custom version of memcpy(), can over read/write up to WILDCOPY_OVERLENGTH bytes (if length==0) + * @param ovtype controls the overlap detection + * - ZSTD_no_overlap: The source and destination are guaranteed to be at least WILDCOPY_VECLEN bytes apart. + * - ZSTD_overlap_src_before_dst: The src and dst may overlap, but they MUST be at least 8 bytes apart. + * The src buffer must be before the dst buffer. + */ MEM_STATIC FORCE_INLINE_ATTR DONT_VECTORIZE -void ZSTD_wildcopy(void* dst, const void* src, BYTE* oend_g, ptrdiff_t length, ZSTD_overlap_e ovtype) +void ZSTD_wildcopy(void* dst, const void* src, ptrdiff_t length, ZSTD_overlap_e ovtype) { ptrdiff_t diff = (BYTE*)dst - (const BYTE*)src; const BYTE* ip = (const BYTE*)src; BYTE* op = (BYTE*)dst; BYTE* const oend = op + length; - assert(diff >= 8 || (ovtype == ZSTD_no_overlap && diff < -8)); + assert(diff >= 8 || (ovtype == ZSTD_no_overlap && diff <= -WILDCOPY_VECLEN)); - if (length < VECLEN || (ovtype == ZSTD_overlap_src_before_dst && diff < VECLEN)) { - do - COPY8(op, ip) - while (op < oend); - } - else { - if (oend < oend_g-16) { - /* common case */ + if (ovtype == ZSTD_overlap_src_before_dst && diff < WILDCOPY_VECLEN) { + /* Handle short offset copies. */ do { - COPY16(op, ip); + COPY8(op, ip) + } while (op < oend); + } else { + assert(diff >= WILDCOPY_VECLEN || diff <= -WILDCOPY_VECLEN); + /* Separate out the first two COPY16() calls because the copy length is + * almost certain to be short, so the branches have different + * probabilities. + * On gcc-9 unrolling once is +1.6%, twice is +2%, thrice is +1.8%. + * On clang-8 unrolling once is +1.4%, twice is +3.3%, thrice is +3%. + */ + COPY16(op, ip); + if (op >= oend) return; + COPY16(op, ip); + if (op >= oend) return; + do { + COPY16(op, ip); } while (op < oend); - } - else { - do { - COPY8(op, ip); - } - while (op < oend); - } } } -/*! ZSTD_wildcopy_16min() : - * same semantics as ZSTD_wildcopy() except guaranteed to be able to copy 16 bytes at the start */ -MEM_STATIC FORCE_INLINE_ATTR DONT_VECTORIZE -void ZSTD_wildcopy_16min(void* dst, const void* src, BYTE* oend_g, ptrdiff_t length, ZSTD_overlap_e ovtype) -{ - ptrdiff_t diff = (BYTE*)dst - (const BYTE*)src; - const BYTE* ip = (const BYTE*)src; - BYTE* op = (BYTE*)dst; - BYTE* const oend = op + length; - - assert(length >= 8); - assert(diff >= 8 || (ovtype == ZSTD_no_overlap && diff < -8)); - - if (ovtype == ZSTD_overlap_src_before_dst && diff < VECLEN) { - do { - COPY8(op, ip); - } - while (op < oend); - } - else { - if (oend < oend_g-16) { - /* common case */ - do { - COPY16(op, ip); - } - while (op < oend); - } - else { - do { - COPY8(op, ip); - } - while (op < oend); - } - } -} - -MEM_STATIC void ZSTD_wildcopy_e(void* dst, const void* src, void* dstEnd) /* should be faster for decoding, but strangely, not verified on all platform */ +/*! ZSTD_wildcopy8() : + * The same as ZSTD_wildcopy(), but it can only overwrite 8 bytes, and works for + * overlapping buffers that are at least 8 bytes apart. + */ +MEM_STATIC void ZSTD_wildcopy8(void* dst, const void* src, ptrdiff_t length) { const BYTE* ip = (const BYTE*)src; BYTE* op = (BYTE*)dst; - BYTE* const oend = (BYTE*)dstEnd; - do + BYTE* const oend = (BYTE*)op + length; + do { COPY8(op, ip) - while (op < oend); + } while (op < oend); } diff --git a/lib/compress/zstd_compress_internal.h b/lib/compress/zstd_compress_internal.h index 208a04c5..fefa8aff 100644 --- a/lib/compress/zstd_compress_internal.h +++ b/lib/compress/zstd_compress_internal.h @@ -359,7 +359,10 @@ MEM_STATIC void ZSTD_storeSeq(seqStore_t* seqStorePtr, size_t litLength, const v /* copy Literals */ assert(seqStorePtr->maxNbLit <= 128 KB); assert(seqStorePtr->lit + litLength <= seqStorePtr->litStart + seqStorePtr->maxNbLit); - ZSTD_wildcopy(seqStorePtr->lit, literals, seqStorePtr->lit + litLength + 8, (ptrdiff_t)litLength, ZSTD_no_overlap); + /* We are guaranteed at least 8 bytes of literals space because of HASH_READ_SIZE and + * MINMATCH. + */ + ZSTD_wildcopy8(seqStorePtr->lit, literals, (ptrdiff_t)litLength); seqStorePtr->lit += litLength; /* literal Length */ diff --git a/lib/decompress/zstd_decompress_block.c b/lib/decompress/zstd_decompress_block.c index bab96fb7..e799a5c7 100644 --- a/lib/decompress/zstd_decompress_block.c +++ b/lib/decompress/zstd_decompress_block.c @@ -573,38 +573,118 @@ typedef struct { size_t pos; } seqState_t; +/*! ZSTD_overlapCopy8() : + * Copies 8 bytes from ip to op and updates op and ip where ip <= op. + * If the offset is < 8 then the offset is spread to at least 8 bytes. + * + * Precondition: *ip <= *op + * Postcondition: *op - *op >= 8 + */ +static void ZSTD_overlapCopy8(BYTE** op, BYTE const** ip, size_t offset) { + assert(*ip <= *op); + if (offset < 8) { + /* close range match, overlap */ + static const U32 dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */ + static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* subtracted */ + int const sub2 = dec64table[offset]; + (*op)[0] = (*ip)[0]; + (*op)[1] = (*ip)[1]; + (*op)[2] = (*ip)[2]; + (*op)[3] = (*ip)[3]; + *ip += dec32table[offset]; + ZSTD_copy4(*op+4, *ip); + *ip -= sub2; + } else { + ZSTD_copy8(*op, *ip); + } + *ip += 8; + *op += 8; + assert(*op - *ip >= 8); +} -/* ZSTD_execSequenceLast7(): - * exceptional case : decompress a match starting within last 7 bytes of output buffer. - * requires more careful checks, to ensure there is no overflow. - * performance does not matter though. - * note : this case is supposed to be never generated "naturally" by reference encoder, - * since in most cases it needs at least 8 bytes to look for a match. - * but it's allowed by the specification. */ +/*! ZSTD_safecopy() : + * Specialized version of memcpy() that is allowed to READ up to WILDCOPY_OVERLENGTH past the input buffer + * and write up to 16 bytes past oend_w (op >= oend_w is allowed). + * This function is only called in the uncommon case where the sequence is near the end of the block. It + * should be fast for a single long sequence, but can be slow for several short sequences. + * + * @param ovtype controls the overlap detection + * - ZSTD_no_overlap: The source and destination are guaranteed to be at least WILDCOPY_VECLEN bytes apart. + * - ZSTD_overlap_src_before_dst: The src and dst may overlap and may be any distance apart. + * The src buffer must be before the dst buffer. + */ +static void ZSTD_safecopy(BYTE* op, BYTE* const oend_w, BYTE const* ip, ptrdiff_t length, ZSTD_overlap_e ovtype) { + ptrdiff_t const diff = op - ip; + BYTE* const oend = op + length; + + assert((ovtype == ZSTD_no_overlap && (diff <= -8 || diff >= 8)) || + (ovtype == ZSTD_overlap_src_before_dst && diff >= 0)); + + if (length < 8) { + /* Handle short lengths. */ + while (op < oend) *op++ = *ip++; + return; + } + if (ovtype == ZSTD_overlap_src_before_dst) { + /* Copy 8 bytes and ensure the offset >= 8 when there can be overlap. */ + assert(length >= 8); + ZSTD_overlapCopy8(&op, &ip, diff); + assert(op - ip >= 8); + assert(op <= oend); + } + + if (oend <= oend_w) { + /* No risk of overwrite. */ + ZSTD_wildcopy(op, ip, length, ovtype); + return; + } + if (op <= oend_w) { + /* Wildcopy until we get close to the end. */ + assert(oend > oend_w); + ZSTD_wildcopy(op, ip, oend_w - op, ovtype); + ip += oend_w - op; + op = oend_w; + } + /* Handle the leftovers. */ + while (op < oend) *op++ = *ip++; +} + +/* ZSTD_execSequenceEnd(): + * This version handles cases that are near the end of the output buffer. It requires + * more careful checks to make sure there is no overflow. By separating out these hard + * and unlikely cases, we can speed up the common cases. + * + * NOTE: This function needs to be fast for a single long sequence, but doesn't need + * to be optimized for many small sequences, since those fall into ZSTD_execSequence(). + */ FORCE_NOINLINE -size_t ZSTD_execSequenceLast7(BYTE* op, - BYTE* const oend, seq_t sequence, - const BYTE** litPtr, const BYTE* const litLimit, - const BYTE* const base, const BYTE* const vBase, const BYTE* const dictEnd) +size_t ZSTD_execSequenceEnd(BYTE* op, + BYTE* const oend, seq_t sequence, + const BYTE** litPtr, const BYTE* const litLimit, + const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd) { BYTE* const oLitEnd = op + sequence.litLength; size_t const sequenceLength = sequence.litLength + sequence.matchLength; BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */ const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; + BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH; - /* check */ - RETURN_ERROR_IF(oMatchEnd>oend, dstSize_tooSmall, "last match must fit within dstBuffer"); + /* bounds checks */ + assert(oLitEnd < oMatchEnd); + RETURN_ERROR_IF(oMatchEnd > oend, dstSize_tooSmall, "last match must fit within dstBuffer"); RETURN_ERROR_IF(iLitEnd > litLimit, corruption_detected, "try to read beyond literal buffer"); /* copy literals */ - while (op < oLitEnd) *op++ = *(*litPtr)++; + ZSTD_safecopy(op, oend_w, *litPtr, sequence.litLength, ZSTD_no_overlap); + op = oLitEnd; + *litPtr = iLitEnd; /* copy Match */ - if (sequence.offset > (size_t)(oLitEnd - base)) { + if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix */ - RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - vBase),corruption_detected); - match = dictEnd - (base-match); + RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected); + match = dictEnd - (prefixStart-match); if (match + sequence.matchLength <= dictEnd) { memmove(oLitEnd, match, sequence.matchLength); return sequenceLength; @@ -614,13 +694,12 @@ size_t ZSTD_execSequenceLast7(BYTE* op, memmove(oLitEnd, match, length1); op = oLitEnd + length1; sequence.matchLength -= length1; - match = base; + match = prefixStart; } } - while (op < oMatchEnd) *op++ = *match++; + ZSTD_safecopy(op, oend_w, match, sequence.matchLength, ZSTD_overlap_src_before_dst); return sequenceLength; } - HINT_INLINE size_t ZSTD_execSequence(BYTE* op, BYTE* const oend, seq_t sequence, @@ -634,20 +713,27 @@ size_t ZSTD_execSequence(BYTE* op, const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; - /* check */ - RETURN_ERROR_IF(oMatchEnd>oend, dstSize_tooSmall, "last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend"); - RETURN_ERROR_IF(iLitEnd > litLimit, corruption_detected, "over-read beyond lit buffer"); - if (oLitEnd>oend_w) return ZSTD_execSequenceLast7(op, oend, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd); + /* Errors and uncommon cases handled here. */ + assert(oLitEnd < oMatchEnd); + if (iLitEnd > litLimit || oMatchEnd > oend_w) + return ZSTD_execSequenceEnd(op, oend, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd); - /* copy Literals */ - if (sequence.litLength > 8) - ZSTD_wildcopy_16min(op, (*litPtr), oend, sequence.litLength, ZSTD_no_overlap); /* note : since oLitEnd <= oend-WILDCOPY_OVERLENGTH, no risk of overwrite beyond oend */ + /* Assumptions (everything else goes into ZSTD_execSequenceEnd()) */ + assert(iLitEnd <= litLimit /* Literal length is in bounds */); + assert(oLitEnd <= oend_w /* Can wildcopy literals */); + assert(oMatchEnd <= oend_w /* Can wildcopy matches */); + + /* Copy Literals: + * Split out litLength <= 16 since it is nearly always true. +1% on gcc-9. + */ + if (sequence.litLength <= 16) + ZSTD_copy16(op, *litPtr); else - ZSTD_copy8(op, *litPtr); + ZSTD_wildcopy(op, (*litPtr), sequence.litLength, ZSTD_no_overlap); op = oLitEnd; *litPtr = iLitEnd; /* update for next sequence */ - /* copy Match */ + /* Copy Match */ if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix -> go into extDict */ RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected); @@ -662,123 +748,33 @@ size_t ZSTD_execSequence(BYTE* op, op = oLitEnd + length1; sequence.matchLength -= length1; match = prefixStart; - if (op > oend_w || sequence.matchLength < MINMATCH) { - U32 i; - for (i = 0; i < sequence.matchLength; ++i) op[i] = match[i]; - return sequenceLength; - } } } - /* Requirement: op <= oend_w && sequence.matchLength >= MINMATCH */ + /* Match within prefix of 1 or more bytes */ + assert(op <= oMatchEnd); + assert(oMatchEnd <= oend_w); + assert(match >= prefixStart); + assert(sequence.matchLength >= 1); - /* match within prefix */ - if (sequence.offset < 8) { - /* close range match, overlap */ - static const U32 dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */ - static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* subtracted */ - int const sub2 = dec64table[sequence.offset]; - op[0] = match[0]; - op[1] = match[1]; - op[2] = match[2]; - op[3] = match[3]; - match += dec32table[sequence.offset]; - ZSTD_copy4(op+4, match); - match -= sub2; - } else { - ZSTD_copy8(op, match); + /* Nearly all offsets are >= 16 bytes, which means we can use wildcopy + * without overlap checking. + */ + if (sequence.offset >= 16) { + /* Split out matchLength <= 16 since it is nearly always true. +1% on gcc-9. */ + if (sequence.matchLength <= 16) + ZSTD_copy16(op, match); + else + ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap); + return sequenceLength; } - op += 8; match += 8; + assert(sequence.offset < 16); - if (oMatchEnd > oend-(16-MINMATCH)) { - if (op < oend_w) { - ZSTD_wildcopy(op, match, oend, oend_w - op, ZSTD_overlap_src_before_dst); - match += oend_w - op; - op = oend_w; - } - while (op < oMatchEnd) *op++ = *match++; - } else { - ZSTD_wildcopy(op, match, oend, (ptrdiff_t)sequence.matchLength-8, ZSTD_overlap_src_before_dst); /* works even if matchLength < 8 */ - } - return sequenceLength; -} + /* Copy 8 bytes and spread the offset to be >= 8. */ + ZSTD_overlapCopy8(&op, &match, sequence.offset); - -HINT_INLINE -size_t ZSTD_execSequenceLong(BYTE* op, - BYTE* const oend, seq_t sequence, - const BYTE** litPtr, const BYTE* const litLimit, - const BYTE* const prefixStart, const BYTE* const dictStart, const BYTE* const dictEnd) -{ - BYTE* const oLitEnd = op + sequence.litLength; - size_t const sequenceLength = sequence.litLength + sequence.matchLength; - BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */ - BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH; - const BYTE* const iLitEnd = *litPtr + sequence.litLength; - const BYTE* match = sequence.match; - - /* check */ - RETURN_ERROR_IF(oMatchEnd > oend, dstSize_tooSmall, "last match must start at a minimum distance of WILDCOPY_OVERLENGTH from oend"); - RETURN_ERROR_IF(iLitEnd > litLimit, corruption_detected, "over-read beyond lit buffer"); - if (oLitEnd > oend_w) return ZSTD_execSequenceLast7(op, oend, sequence, litPtr, litLimit, prefixStart, dictStart, dictEnd); - - /* copy Literals */ - if (sequence.litLength > 8) - ZSTD_wildcopy_16min(op, *litPtr, oend, sequence.litLength, ZSTD_no_overlap); /* note : since oLitEnd <= oend-WILDCOPY_OVERLENGTH, no risk of overwrite beyond oend */ - else - ZSTD_copy8(op, *litPtr); /* note : op <= oLitEnd <= oend_w == oend - 8 */ - - op = oLitEnd; - *litPtr = iLitEnd; /* update for next sequence */ - - /* copy Match */ - if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { - /* offset beyond prefix */ - RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - dictStart), corruption_detected); - if (match + sequence.matchLength <= dictEnd) { - memmove(oLitEnd, match, sequence.matchLength); - return sequenceLength; - } - /* span extDict & currentPrefixSegment */ - { size_t const length1 = dictEnd - match; - memmove(oLitEnd, match, length1); - op = oLitEnd + length1; - sequence.matchLength -= length1; - match = prefixStart; - if (op > oend_w || sequence.matchLength < MINMATCH) { - U32 i; - for (i = 0; i < sequence.matchLength; ++i) op[i] = match[i]; - return sequenceLength; - } - } } - assert(op <= oend_w); - assert(sequence.matchLength >= MINMATCH); - - /* match within prefix */ - if (sequence.offset < 8) { - /* close range match, overlap */ - static const U32 dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */ - static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* subtracted */ - int const sub2 = dec64table[sequence.offset]; - op[0] = match[0]; - op[1] = match[1]; - op[2] = match[2]; - op[3] = match[3]; - match += dec32table[sequence.offset]; - ZSTD_copy4(op+4, match); - match -= sub2; - } else { - ZSTD_copy8(op, match); - } - op += 8; match += 8; - - if (oMatchEnd > oend-(16-MINMATCH)) { - if (op < oend_w) { - ZSTD_wildcopy(op, match, oend, oend_w - op, ZSTD_overlap_src_before_dst); - match += oend_w - op; - op = oend_w; - } - while (op < oMatchEnd) *op++ = *match++; - } else { - ZSTD_wildcopy(op, match, oend, (ptrdiff_t)sequence.matchLength-8, ZSTD_overlap_src_before_dst); /* works even if matchLength < 8 */ + /* If the match length is > 8 bytes, then continue with the wildcopy. */ + if (sequence.matchLength > 8) { + assert(op < oMatchEnd); + ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength-8, ZSTD_overlap_src_before_dst); } return sequenceLength; } @@ -1098,7 +1094,7 @@ ZSTD_decompressSequencesLong_body( /* decode and decompress */ for ( ; (BIT_reloadDStream(&(seqState.DStream)) <= BIT_DStream_completed) && (seqNb