--- /dev/null
+/*
+ * C port of the snappy compressor from Google.
+ * This is a very fast compressor with comparable compression to lzo.
+ * Works best on 64bit little-endian, but should be good on others too.
+ * Ported by Andi Kleen.
+ * Based on snappy 1.0.3 plus some selected changes from SVN.
+ */
+
+/*
+ * Copyright 2005 Google Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "postgres.h"
+
+#include "common/snappy/snappy.h"
+#include "snappy-compat.h"
+
+#define CRASH_UNLESS(x) BUG_ON(!(x))
+#define CHECK(cond) CRASH_UNLESS(cond)
+#define CHECK_LE(a, b) CRASH_UNLESS((a) <= (b))
+#define CHECK_GE(a, b) CRASH_UNLESS((a) >= (b))
+#define CHECK_EQ(a, b) CRASH_UNLESS((a) == (b))
+#define CHECK_NE(a, b) CRASH_UNLESS((a) != (b))
+#define CHECK_LT(a, b) CRASH_UNLESS((a) < (b))
+#define CHECK_GT(a, b) CRASH_UNLESS((a) > (b))
+
+#define UNALIGNED_LOAD16(_p) get_unaligned((u16 *)(_p))
+#define UNALIGNED_LOAD32(_p) get_unaligned((u32 *)(_p))
+#define UNALIGNED_LOAD64(_p) get_unaligned((u64 *)(_p))
+
+#define UNALIGNED_STORE16(_p, _val) put_unaligned(_val, (u16 *)(_p))
+#define UNALIGNED_STORE32(_p, _val) put_unaligned(_val, (u32 *)(_p))
+#define UNALIGNED_STORE64(_p, _val) put_unaligned(_val, (u64 *)(_p))
+
+#ifdef NDEBUG
+
+#define DCHECK(cond) do {} while(0)
+#define DCHECK_LE(a, b) do {} while(0)
+#define DCHECK_GE(a, b) do {} while(0)
+#define DCHECK_EQ(a, b) do {} while(0)
+#define DCHECK_NE(a, b) do {} while(0)
+#define DCHECK_LT(a, b) do {} while(0)
+#define DCHECK_GT(a, b) do {} while(0)
+
+#else
+
+#define DCHECK(cond) CHECK(cond)
+#define DCHECK_LE(a, b) CHECK_LE(a, b)
+#define DCHECK_GE(a, b) CHECK_GE(a, b)
+#define DCHECK_EQ(a, b) CHECK_EQ(a, b)
+#define DCHECK_NE(a, b) CHECK_NE(a, b)
+#define DCHECK_LT(a, b) CHECK_LT(a, b)
+#define DCHECK_GT(a, b) CHECK_GT(a, b)
+
+#endif
+
+static inline bool is_little_endian(void)
+{
+#ifndef WORDS_BIGENDIAN
+ return true;
+#endif
+ return false;
+}
+
+static inline int log2_floor(u32 n)
+{
+ return n == 0 ? -1 : 31 ^ __builtin_clz(n);
+}
+
+static inline int find_lsb_set_non_zero(u32 n)
+{
+ return __builtin_ctz(n);
+}
+
+static inline int find_lsb_set_non_zero64(u64 n)
+{
+ return __builtin_ctzll(n);
+}
+
+#define kmax32 5
+
+/*
+ * Attempts to parse a varint32 from a prefix of the bytes in [ptr,limit-1].
+ * Never reads a character at or beyond limit. If a valid/terminated varint32
+ * was found in the range, stores it in *OUTPUT and returns a pointer just
+ * past the last byte of the varint32. Else returns NULL. On success,
+ * "result <= limit".
+ */
+static inline const char *varint_parse32_with_limit(const char *p,
+ const char *l,
+ u32 * OUTPUT)
+{
+ const unsigned char *ptr = (const unsigned char *)(p);
+ const unsigned char *limit = (const unsigned char *)(l);
+ u32 b, result;
+
+ if (ptr >= limit)
+ return NULL;
+ b = *(ptr++);
+ result = b & 127;
+ if (b < 128)
+ goto done;
+ if (ptr >= limit)
+ return NULL;
+ b = *(ptr++);
+ result |= (b & 127) << 7;
+ if (b < 128)
+ goto done;
+ if (ptr >= limit)
+ return NULL;
+ b = *(ptr++);
+ result |= (b & 127) << 14;
+ if (b < 128)
+ goto done;
+ if (ptr >= limit)
+ return NULL;
+ b = *(ptr++);
+ result |= (b & 127) << 21;
+ if (b < 128)
+ goto done;
+ if (ptr >= limit)
+ return NULL;
+ b = *(ptr++);
+ result |= (b & 127) << 28;
+ if (b < 16)
+ goto done;
+ return NULL; /* Value is too long to be a varint32 */
+done:
+ *OUTPUT = result;
+ return (const char *)(ptr);
+}
+
+/*
+ * REQUIRES "ptr" points to a buffer of length sufficient to hold "v".
+ * EFFECTS Encodes "v" into "ptr" and returns a pointer to the
+ * byte just past the last encoded byte.
+ */
+static inline char *varint_encode32(char *sptr, u32 v)
+{
+ /* Operate on characters as unsigneds */
+ unsigned char *ptr = (unsigned char *)(sptr);
+ static const int B = 128;
+
+ if (v < (1 << 7)) {
+ *(ptr++) = v;
+ } else if (v < (1 << 14)) {
+ *(ptr++) = v | B;
+ *(ptr++) = v >> 7;
+ } else if (v < (1 << 21)) {
+ *(ptr++) = v | B;
+ *(ptr++) = (v >> 7) | B;
+ *(ptr++) = v >> 14;
+ } else if (v < (1 << 28)) {
+ *(ptr++) = v | B;
+ *(ptr++) = (v >> 7) | B;
+ *(ptr++) = (v >> 14) | B;
+ *(ptr++) = v >> 21;
+ } else {
+ *(ptr++) = v | B;
+ *(ptr++) = (v >> 7) | B;
+ *(ptr++) = (v >> 14) | B;
+ *(ptr++) = (v >> 21) | B;
+ *(ptr++) = v >> 28;
+ }
+ return (char *)(ptr);
+}
+
+#ifdef SG
+
+struct source {
+ struct iovec *iov;
+ int iovlen;
+ int curvec;
+ int curoff;
+ size_t total;
+};
+
+/* Only valid at beginning when nothing is consumed */
+static inline int available(struct source *s)
+{
+ return s->total;
+}
+
+static inline const char *peek(struct source *s, size_t *len)
+{
+ if (likely(s->curvec < s->iovlen)) {
+ struct iovec *iv = &s->iov[s->curvec];
+ if (s->curoff < iv->iov_len) {
+ *len = iv->iov_len - s->curoff;
+ return iv->iov_base + s->curoff;
+ }
+ }
+ *len = 0;
+ return NULL;
+}
+
+static inline void skip(struct source *s, size_t n)
+{
+ struct iovec *iv = &s->iov[s->curvec];
+ s->curoff += n;
+ DCHECK_LE(s->curoff, iv->iov_len);
+ if (s->curoff >= iv->iov_len && s->curvec + 1 < s->iovlen) {
+ s->curoff = 0;
+ s->curvec++;
+ }
+}
+
+struct sink {
+ struct iovec *iov;
+ int iovlen;
+ unsigned curvec;
+ unsigned curoff;
+ unsigned written;
+};
+
+static inline void append(struct sink *s, const char *data, size_t n)
+{
+ struct iovec *iov = &s->iov[s->curvec];
+ char *dst = iov->iov_base + s->curoff;
+ size_t nlen = min_t(size_t, iov->iov_len - s->curoff, n);
+ if (data != dst)
+ memcpy(dst, data, nlen);
+ s->written += n;
+ s->curoff += nlen;
+ while ((n -= nlen) > 0) {
+ data += nlen;
+ s->curvec++;
+ DCHECK_LT(s->curvec, s->iovlen);
+ iov++;
+ nlen = min_t(size_t, iov->iov_len, n);
+ memcpy(iov->iov_base, data, nlen);
+ s->curoff = nlen;
+ }
+}
+
+static inline void *sink_peek(struct sink *s, size_t n)
+{
+ struct iovec *iov = &s->iov[s->curvec];
+ if (s->curvec < iov->iov_len && iov->iov_len - s->curoff >= n)
+ return iov->iov_base + s->curoff;
+ return NULL;
+}
+
+#else
+
+struct source {
+ const char *ptr;
+ size_t left;
+};
+
+static inline int available(struct source *s)
+{
+ return s->left;
+}
+
+static inline const char *peek(struct source *s, size_t * len)
+{
+ *len = s->left;
+ return s->ptr;
+}
+
+static inline void skip(struct source *s, size_t n)
+{
+ s->left -= n;
+ s->ptr += n;
+}
+
+struct sink {
+ char *dest;
+};
+
+static inline void append(struct sink *s, const char *data, size_t n)
+{
+ if (data != s->dest)
+ memcpy(s->dest, data, n);
+ s->dest += n;
+}
+
+#define sink_peek(s, n) sink_peek_no_sg(s)
+
+static inline void *sink_peek_no_sg(const struct sink *s)
+{
+ return s->dest;
+}
+
+#endif
+
+struct writer {
+ char *base;
+ char *op;
+ char *op_limit;
+};
+
+/* Called before decompression */
+static inline void writer_set_expected_length(struct writer *w, size_t len)
+{
+ w->op_limit = w->op + len;
+}
+
+/* Called after decompression */
+static inline bool writer_check_length(struct writer *w)
+{
+ return w->op == w->op_limit;
+}
+
+/*
+ * Copy "len" bytes from "src" to "op", one byte at a time. Used for
+ * handling COPY operations where the input and output regions may
+ * overlap. For example, suppose:
+ * src == "ab"
+ * op == src + 2
+ * len == 20
+ * After IncrementalCopy(src, op, len), the result will have
+ * eleven copies of "ab"
+ * ababababababababababab
+ * Note that this does not match the semantics of either memcpy()
+ * or memmove().
+ */
+static inline void incremental_copy(const char *src, char *op, int len)
+{
+ DCHECK_GT(len, 0);
+ do {
+ *op++ = *src++;
+ } while (--len > 0);
+}
+
+/*
+ * Equivalent to IncrementalCopy except that it can write up to ten extra
+ * bytes after the end of the copy, and that it is faster.
+ *
+ * The main part of this loop is a simple copy of eight bytes at a time until
+ * we've copied (at least) the requested amount of bytes. However, if op and
+ * src are less than eight bytes apart (indicating a repeating pattern of
+ * length < 8), we first need to expand the pattern in order to get the correct
+ * results. For instance, if the buffer looks like this, with the eight-byte
+ * <src> and <op> patterns marked as intervals:
+ *
+ * abxxxxxxxxxxxx
+ * [------] src
+ * [------] op
+ *
+ * a single eight-byte copy from <src> to <op> will repeat the pattern once,
+ * after which we can move <op> two bytes without moving <src>:
+ *
+ * ababxxxxxxxxxx
+ * [------] src
+ * [------] op
+ *
+ * and repeat the exercise until the two no longer overlap.
+ *
+ * This allows us to do very well in the special case of one single byte
+ * repeated many times, without taking a big hit for more general cases.
+ *
+ * The worst case of extra writing past the end of the match occurs when
+ * op - src == 1 and len == 1; the last copy will read from byte positions
+ * [0..7] and write to [4..11], whereas it was only supposed to write to
+ * position 1. Thus, ten excess bytes.
+ */
+
+#define kmax_increment_copy_overflow 10
+
+static inline void incremental_copy_fast_path(const char *src, char *op,
+ int len)
+{
+ while (op - src < 8) {
+ UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+ len -= op - src;
+ op += op - src;
+ }
+ while (len > 0) {
+ UNALIGNED_STORE64(op, UNALIGNED_LOAD64(src));
+ src += 8;
+ op += 8;
+ len -= 8;
+ }
+}
+
+static inline bool writer_append_from_self(struct writer *w, u32 offset,
+ u32 len)
+{
+ char *const op = w->op;
+ CHECK_LE(op, w->op_limit);
+ const u32 space_left = w->op_limit - op;
+
+ if (op - w->base <= offset - 1u) /* -1u catches offset==0 */
+ return false;
+ if (len <= 16 && offset >= 8 && space_left >= 16) {
+ /* Fast path, used for the majority (70-80%) of dynamic
+ * invocations. */
+ UNALIGNED_STORE64(op, UNALIGNED_LOAD64(op - offset));
+ UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(op - offset + 8));
+ } else {
+ if (space_left >= len + kmax_increment_copy_overflow) {
+ incremental_copy_fast_path(op - offset, op, len);
+ } else {
+ if (space_left < len) {
+ return false;
+ }
+ incremental_copy(op - offset, op, len);
+ }
+ }
+
+ w->op = op + len;
+ return true;
+}
+
+static inline bool writer_append(struct writer *w, const char *ip, u32 len)
+{
+ char *const op = w->op;
+ CHECK_LE(op, w->op_limit);
+ const u32 space_left = w->op_limit - op;
+ if (space_left < len)
+ return false;
+ memcpy(op, ip, len);
+ w->op = op + len;
+ return true;
+}
+
+static inline bool writer_try_fast_append(struct writer *w, const char *ip,
+ u32 available_bytes, u32 len)
+{
+ char *const op = w->op;
+ const int space_left = w->op_limit - op;
+ if (len <= 16 && available_bytes >= 16 && space_left >= 16) {
+ /* Fast path, used for the majority (~95%) of invocations */
+ UNALIGNED_STORE64(op, UNALIGNED_LOAD64(ip));
+ UNALIGNED_STORE64(op + 8, UNALIGNED_LOAD64(ip + 8));
+ w->op = op + len;
+ return true;
+ }
+ return false;
+}
+
+/*
+ * Any hash function will produce a valid compressed bitstream, but a good
+ * hash function reduces the number of collisions and thus yields better
+ * compression for compressible input, and more speed for incompressible
+ * input. Of course, it doesn't hurt if the hash function is reasonably fast
+ * either, as it gets called a lot.
+ */
+static inline u32 hash_bytes(u32 bytes, int shift)
+{
+ u32 kmul = 0x1e35a7bd;
+ return (bytes * kmul) >> shift;
+}
+
+static inline u32 hash(const char *p, int shift)
+{
+ return hash_bytes(UNALIGNED_LOAD32(p), shift);
+}
+
+/*
+ * Compressed data can be defined as:
+ * compressed := item* literal*
+ * item := literal* copy
+ *
+ * The trailing literal sequence has a space blowup of at most 62/60
+ * since a literal of length 60 needs one tag byte + one extra byte
+ * for length information.
+ *
+ * Item blowup is trickier to measure. Suppose the "copy" op copies
+ * 4 bytes of data. Because of a special check in the encoding code,
+ * we produce a 4-byte copy only if the offset is < 65536. Therefore
+ * the copy op takes 3 bytes to encode, and this type of item leads
+ * to at most the 62/60 blowup for representing literals.
+ *
+ * Suppose the "copy" op copies 5 bytes of data. If the offset is big
+ * enough, it will take 5 bytes to encode the copy op. Therefore the
+ * worst case here is a one-byte literal followed by a five-byte copy.
+ * I.e., 6 bytes of input turn into 7 bytes of "compressed" data.
+ *
+ * This last factor dominates the blowup, so the final estimate is:
+ */
+size_t snappy_max_compressed_length(size_t source_len)
+{
+ return 32 + source_len + source_len / 6;
+}
+EXPORT_SYMBOL(snappy_max_compressed_length);
+
+enum {
+ LITERAL = 0,
+ COPY_1_BYTE_OFFSET = 1, /* 3 bit length + 3 bits of offset in opcode */
+ COPY_2_BYTE_OFFSET = 2,
+ COPY_4_BYTE_OFFSET = 3
+};
+
+static inline char *emit_literal(char *op,
+ const char *literal,
+ int len, bool allow_fast_path)
+{
+ int n = len - 1; /* Zero-length literals are disallowed */
+
+ if (n < 60) {
+ /* Fits in tag byte */
+ *op++ = LITERAL | (n << 2);
+
+/*
+ * The vast majority of copies are below 16 bytes, for which a
+ * call to memcpy is overkill. This fast path can sometimes
+ * copy up to 15 bytes too much, but that is okay in the
+ * main loop, since we have a bit to go on for both sides:
+ *
+ * - The input will always have kInputMarginBytes = 15 extra
+ * available bytes, as long as we're in the main loop, and
+ * if not, allow_fast_path = false.
+ * - The output will always have 32 spare bytes (see
+ * MaxCompressedLength).
+ */
+ if (allow_fast_path && len <= 16) {
+ UNALIGNED_STORE64(op, UNALIGNED_LOAD64(literal));
+ UNALIGNED_STORE64(op + 8,
+ UNALIGNED_LOAD64(literal + 8));
+ return op + len;
+ }
+ } else {
+ /* Encode in upcoming bytes */
+ char *base = op;
+ int count = 0;
+ op++;
+ while (n > 0) {
+ *op++ = n & 0xff;
+ n >>= 8;
+ count++;
+ }
+ DCHECK(count >= 1);
+ DCHECK(count <= 4);
+ *base = LITERAL | ((59 + count) << 2);
+ }
+ memcpy(op, literal, len);
+ return op + len;
+}
+
+static inline char *emit_copy_less_than64(char *op, int offset, int len)
+{
+ DCHECK_LE(len, 64);
+ DCHECK_GE(len, 4);
+ DCHECK_LT(offset, 65536);
+
+ if ((len < 12) && (offset < 2048)) {
+ int len_minus_4 = len - 4;
+ DCHECK(len_minus_4 < 8); /* Must fit in 3 bits */
+ *op++ =
+ COPY_1_BYTE_OFFSET | ((len_minus_4) << 2) | ((offset >> 8)
+ << 5);
+ *op++ = offset & 0xff;
+ } else {
+ *op++ = COPY_2_BYTE_OFFSET | ((len - 1) << 2);
+ put_unaligned_le16(offset, op);
+ op += 2;
+ }
+ return op;
+}
+
+static inline char *emit_copy(char *op, int offset, int len)
+{
+ /*
+ * Emit 64 byte copies but make sure to keep at least four bytes
+ * reserved
+ */
+ while (len >= 68) {
+ op = emit_copy_less_than64(op, offset, 64);
+ len -= 64;
+ }
+
+ /*
+ * Emit an extra 60 byte copy if have too much data to fit in
+ * one copy
+ */
+ if (len > 64) {
+ op = emit_copy_less_than64(op, offset, 60);
+ len -= 60;
+ }
+
+ /* Emit remainder */
+ op = emit_copy_less_than64(op, offset, len);
+ return op;
+}
+
+/**
+ * snappy_uncompressed_length - return length of uncompressed output.
+ * @start: compressed buffer
+ * @n: length of compressed buffer.
+ * @result: Write the length of the uncompressed output here.
+ *
+ * Returns true when successfull, otherwise false.
+ */
+bool snappy_uncompressed_length(const char *start, size_t n, size_t * result)
+{
+ u32 v = 0;
+ const char *limit = start + n;
+ if (varint_parse32_with_limit(start, limit, &v) != NULL) {
+ *result = v;
+ return true;
+ } else {
+ return false;
+ }
+}
+EXPORT_SYMBOL(snappy_uncompressed_length);
+
+#define kblock_log 15
+#define kblock_size (1 << kblock_log)
+
+/*
+ * This value could be halfed or quartered to save memory
+ * at the cost of slightly worse compression.
+ */
+#define kmax_hash_table_bits 14
+#define kmax_hash_table_size (1U << kmax_hash_table_bits)
+
+/*
+ * Use smaller hash table when input.size() is smaller, since we
+ * fill the table, incurring O(hash table size) overhead for
+ * compression, and if the input is short, we won't need that
+ * many hash table entries anyway.
+ */
+static u16 *get_hash_table(struct snappy_env *env, size_t input_size,
+ int *table_size)
+{
+ unsigned htsize = 256;
+
+ DCHECK(kmax_hash_table_size >= 256);
+ while (htsize < kmax_hash_table_size && htsize < input_size)
+ htsize <<= 1;
+ CHECK_EQ(0, htsize & (htsize - 1));
+ CHECK_LE(htsize, kmax_hash_table_size);
+
+ u16 *table;
+ table = env->hash_table;
+
+ *table_size = htsize;
+ memset(table, 0, htsize * sizeof(*table));
+ return table;
+}
+
+/*
+ * Return the largest n such that
+ *
+ * s1[0,n-1] == s2[0,n-1]
+ * and n <= (s2_limit - s2).
+ *
+ * Does not read *s2_limit or beyond.
+ * Does not read *(s1 + (s2_limit - s2)) or beyond.
+ * Requires that s2_limit >= s2.
+ *
+ * Separate implementation for x86_64, for speed. Uses the fact that
+ * x86_64 is little endian.
+ */
+#if !defined(WORDS_BIGENDIAN) && BITS_PER_LONG == 64
+static inline int find_match_length(const char *s1,
+ const char *s2, const char *s2_limit)
+{
+ int matched = 0;
+
+ DCHECK_GE(s2_limit, s2);
+ /*
+ * Find out how long the match is. We loop over the data 64 bits at a
+ * time until we find a 64-bit block that doesn't match; then we find
+ * the first non-matching bit and use that to calculate the total
+ * length of the match.
+ */
+ while (likely(s2 <= s2_limit - 8)) {
+ if (unlikely
+ (UNALIGNED_LOAD64(s2) == UNALIGNED_LOAD64(s1 + matched))) {
+ s2 += 8;
+ matched += 8;
+ } else {
+ /*
+ * On current (mid-2008) Opteron models there
+ * is a 3% more efficient code sequence to
+ * find the first non-matching byte. However,
+ * what follows is ~10% better on Intel Core 2
+ * and newer, and we expect AMD's bsf
+ * instruction to improve.
+ */
+ u64 x =
+ UNALIGNED_LOAD64(s2) ^ UNALIGNED_LOAD64(s1 +
+ matched);
+ int matching_bits = find_lsb_set_non_zero64(x);
+ matched += matching_bits >> 3;
+ return matched;
+ }
+ }
+ while (likely(s2 < s2_limit)) {
+ if (likely(s1[matched] == *s2)) {
+ ++s2;
+ ++matched;
+ } else {
+ return matched;
+ }
+ }
+ return matched;
+}
+#else
+static inline int find_match_length(const char *s1,
+ const char *s2, const char *s2_limit)
+{
+ /* Implementation based on the x86-64 version, above. */
+ DCHECK_GE(s2_limit, s2);
+ int matched = 0;
+
+ while (s2 <= s2_limit - 4 &&
+ UNALIGNED_LOAD32(s2) == UNALIGNED_LOAD32(s1 + matched)) {
+ s2 += 4;
+ matched += 4;
+ }
+ if (is_little_endian() && s2 <= s2_limit - 4) {
+ u32 x =
+ UNALIGNED_LOAD32(s2) ^ UNALIGNED_LOAD32(s1 + matched);
+ int matching_bits = find_lsb_set_non_zero(x);
+ matched += matching_bits >> 3;
+ } else {
+ while ((s2 < s2_limit) && (s1[matched] == *s2)) {
+ ++s2;
+ ++matched;
+ }
+ }
+ return matched;
+}
+#endif
+
+/*
+ * For 0 <= offset <= 4, GetU32AtOffset(UNALIGNED_LOAD64(p), offset) will
+ * equal UNALIGNED_LOAD32(p + offset). Motivation: On x86-64 hardware we have
+ * empirically found that overlapping loads such as
+ * UNALIGNED_LOAD32(p) ... UNALIGNED_LOAD32(p+1) ... UNALIGNED_LOAD32(p+2)
+ * are slower than UNALIGNED_LOAD64(p) followed by shifts and casts to u32.
+ */
+static inline u32 get_u32_at_offset(u64 v, int offset)
+{
+ DCHECK(0 <= offset && offset <= 4);
+ return v >> (is_little_endian()? 8 * offset : 32 - 8 * offset);
+}
+
+/*
+ * Flat array compression that does not emit the "uncompressed length"
+ * prefix. Compresses "input" string to the "*op" buffer.
+ *
+ * REQUIRES: "input" is at most "kBlockSize" bytes long.
+ * REQUIRES: "op" points to an array of memory that is at least
+ * "MaxCompressedLength(input.size())" in size.
+ * REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+ * REQUIRES: "table_size" is a power of two
+ *
+ * Returns an "end" pointer into "op" buffer.
+ * "end - op" is the compressed size of "input".
+ */
+
+static char *compress_fragment(const char *const input,
+ const size_t input_size,
+ char *op, u16 * table, const unsigned table_size)
+{
+ /* "ip" is the input pointer, and "op" is the output pointer. */
+ const char *ip = input;
+ CHECK_LE(input_size, kblock_size);
+ CHECK_EQ(table_size & (table_size - 1), 0);
+ const int shift = 32 - log2_floor(table_size);
+ DCHECK_EQ(UINT_MAX >> shift, table_size - 1);
+ const char *ip_end = input + input_size;
+ const char *baseip = ip;
+ /*
+ * Bytes in [next_emit, ip) will be emitted as literal bytes. Or
+ * [next_emit, ip_end) after the main loop.
+ */
+ const char *next_emit = ip;
+
+ const unsigned kinput_margin_bytes = 15;
+
+ if (likely(input_size >= kinput_margin_bytes)) {
+ const char *const ip_limit = input + input_size -
+ kinput_margin_bytes;
+
+ u32 next_hash;
+ for (next_hash = hash(++ip, shift);;) {
+ DCHECK_LT(next_emit, ip);
+/*
+ * The body of this loop calls EmitLiteral once and then EmitCopy one or
+ * more times. (The exception is that when we're close to exhausting
+ * the input we goto emit_remainder.)
+ *
+ * In the first iteration of this loop we're just starting, so
+ * there's nothing to copy, so calling EmitLiteral once is
+ * necessary. And we only start a new iteration when the
+ * current iteration has determined that a call to EmitLiteral will
+ * precede the next call to EmitCopy (if any).
+ *
+ * Step 1: Scan forward in the input looking for a 4-byte-long match.
+ * If we get close to exhausting the input then goto emit_remainder.
+ *
+ * Heuristic match skipping: If 32 bytes are scanned with no matches
+ * found, start looking only at every other byte. If 32 more bytes are
+ * scanned, look at every third byte, etc.. When a match is found,
+ * immediately go back to looking at every byte. This is a small loss
+ * (~5% performance, ~0.1% density) for lcompressible data due to more
+ * bookkeeping, but for non-compressible data (such as JPEG) it's a huge
+ * win since the compressor quickly "realizes" the data is incompressible
+ * and doesn't bother looking for matches everywhere.
+ *
+ * The "skip" variable keeps track of how many bytes there are since the
+ * last match; dividing it by 32 (ie. right-shifting by five) gives the
+ * number of bytes to move ahead for each iteration.
+ */
+ u32 skip_bytes = 32;
+
+ const char *next_ip = ip;
+ const char *candidate;
+ do {
+ ip = next_ip;
+ u32 hval = next_hash;
+ DCHECK_EQ(hval, hash(ip, shift));
+ u32 bytes_between_hash_lookups = skip_bytes++ >> 5;
+ next_ip = ip + bytes_between_hash_lookups;
+ if (unlikely(next_ip > ip_limit)) {
+ goto emit_remainder;
+ }
+ next_hash = hash(next_ip, shift);
+ candidate = baseip + table[hval];
+ DCHECK_GE(candidate, baseip);
+ DCHECK_LT(candidate, ip);
+
+ table[hval] = ip - baseip;
+ } while (likely(UNALIGNED_LOAD32(ip) !=
+ UNALIGNED_LOAD32(candidate)));
+
+/*
+ * Step 2: A 4-byte match has been found. We'll later see if more
+ * than 4 bytes match. But, prior to the match, input
+ * bytes [next_emit, ip) are unmatched. Emit them as "literal bytes."
+ */
+ DCHECK_LE(next_emit + 16, ip_end);
+ op = emit_literal(op, next_emit, ip - next_emit, true);
+
+/*
+ * Step 3: Call EmitCopy, and then see if another EmitCopy could
+ * be our next move. Repeat until we find no match for the
+ * input immediately after what was consumed by the last EmitCopy call.
+ *
+ * If we exit this loop normally then we need to call EmitLiteral next,
+ * though we don't yet know how big the literal will be. We handle that
+ * by proceeding to the next iteration of the main loop. We also can exit
+ * this loop via goto if we get close to exhausting the input.
+ */
+ u64 input_bytes = 0;
+ u32 candidate_bytes = 0;
+
+ do {
+/*
+ * We have a 4-byte match at ip, and no need to emit any
+ * "literal bytes" prior to ip.
+ */
+ const char *base = ip;
+ int matched = 4 +
+ find_match_length(candidate + 4, ip + 4,
+ ip_end);
+ ip += matched;
+ int offset = base - candidate;
+ DCHECK_EQ(0, memcmp(base, candidate, matched));
+ op = emit_copy(op, offset, matched);
+/*
+ * We could immediately start working at ip now, but to improve
+ * compression we first update table[Hash(ip - 1, ...)].
+ */
+ const char *insert_tail = ip - 1;
+ next_emit = ip;
+ if (unlikely(ip >= ip_limit)) {
+ goto emit_remainder;
+ }
+ input_bytes = UNALIGNED_LOAD64(insert_tail);
+ u32 prev_hash =
+ hash_bytes(get_u32_at_offset
+ (input_bytes, 0), shift);
+ table[prev_hash] = ip - baseip - 1;
+ u32 cur_hash =
+ hash_bytes(get_u32_at_offset
+ (input_bytes, 1), shift);
+ candidate = baseip + table[cur_hash];
+ candidate_bytes = UNALIGNED_LOAD32(candidate);
+ table[cur_hash] = ip - baseip;
+ } while (get_u32_at_offset(input_bytes, 1) ==
+ candidate_bytes);
+
+ next_hash =
+ hash_bytes(get_u32_at_offset(input_bytes, 2),
+ shift);
+ ++ip;
+ }
+ }
+
+emit_remainder:
+ /* Emit the remaining bytes as a literal */
+ if (next_emit < ip_end)
+ op = emit_literal(op, next_emit, ip_end - next_emit, false);
+
+ return op;
+}
+
+/*
+ * -----------------------------------------------------------------------
+ * Lookup table for decompression code. Generated by ComputeTable() below.
+ * -----------------------------------------------------------------------
+ */
+
+/* Mapping from i in range [0,4] to a mask to extract the bottom 8*i bits */
+static const u32 wordmask[] = {
+ 0u, 0xffu, 0xffffu, 0xffffffu, 0xffffffffu
+};
+
+/*
+ * Data stored per entry in lookup table:
+ * Range Bits-used Description
+ * ------------------------------------
+ * 1..64 0..7 Literal/copy length encoded in opcode byte
+ * 0..7 8..10 Copy offset encoded in opcode byte / 256
+ * 0..4 11..13 Extra bytes after opcode
+ *
+ * We use eight bits for the length even though 7 would have sufficed
+ * because of efficiency reasons:
+ * (1) Extracting a byte is faster than a bit-field
+ * (2) It properly aligns copy offset so we do not need a <<8
+ */
+static const u16 char_table[256] = {
+ 0x0001, 0x0804, 0x1001, 0x2001, 0x0002, 0x0805, 0x1002, 0x2002,
+ 0x0003, 0x0806, 0x1003, 0x2003, 0x0004, 0x0807, 0x1004, 0x2004,
+ 0x0005, 0x0808, 0x1005, 0x2005, 0x0006, 0x0809, 0x1006, 0x2006,
+ 0x0007, 0x080a, 0x1007, 0x2007, 0x0008, 0x080b, 0x1008, 0x2008,
+ 0x0009, 0x0904, 0x1009, 0x2009, 0x000a, 0x0905, 0x100a, 0x200a,
+ 0x000b, 0x0906, 0x100b, 0x200b, 0x000c, 0x0907, 0x100c, 0x200c,
+ 0x000d, 0x0908, 0x100d, 0x200d, 0x000e, 0x0909, 0x100e, 0x200e,
+ 0x000f, 0x090a, 0x100f, 0x200f, 0x0010, 0x090b, 0x1010, 0x2010,
+ 0x0011, 0x0a04, 0x1011, 0x2011, 0x0012, 0x0a05, 0x1012, 0x2012,
+ 0x0013, 0x0a06, 0x1013, 0x2013, 0x0014, 0x0a07, 0x1014, 0x2014,
+ 0x0015, 0x0a08, 0x1015, 0x2015, 0x0016, 0x0a09, 0x1016, 0x2016,
+ 0x0017, 0x0a0a, 0x1017, 0x2017, 0x0018, 0x0a0b, 0x1018, 0x2018,
+ 0x0019, 0x0b04, 0x1019, 0x2019, 0x001a, 0x0b05, 0x101a, 0x201a,
+ 0x001b, 0x0b06, 0x101b, 0x201b, 0x001c, 0x0b07, 0x101c, 0x201c,
+ 0x001d, 0x0b08, 0x101d, 0x201d, 0x001e, 0x0b09, 0x101e, 0x201e,
+ 0x001f, 0x0b0a, 0x101f, 0x201f, 0x0020, 0x0b0b, 0x1020, 0x2020,
+ 0x0021, 0x0c04, 0x1021, 0x2021, 0x0022, 0x0c05, 0x1022, 0x2022,
+ 0x0023, 0x0c06, 0x1023, 0x2023, 0x0024, 0x0c07, 0x1024, 0x2024,
+ 0x0025, 0x0c08, 0x1025, 0x2025, 0x0026, 0x0c09, 0x1026, 0x2026,
+ 0x0027, 0x0c0a, 0x1027, 0x2027, 0x0028, 0x0c0b, 0x1028, 0x2028,
+ 0x0029, 0x0d04, 0x1029, 0x2029, 0x002a, 0x0d05, 0x102a, 0x202a,
+ 0x002b, 0x0d06, 0x102b, 0x202b, 0x002c, 0x0d07, 0x102c, 0x202c,
+ 0x002d, 0x0d08, 0x102d, 0x202d, 0x002e, 0x0d09, 0x102e, 0x202e,
+ 0x002f, 0x0d0a, 0x102f, 0x202f, 0x0030, 0x0d0b, 0x1030, 0x2030,
+ 0x0031, 0x0e04, 0x1031, 0x2031, 0x0032, 0x0e05, 0x1032, 0x2032,
+ 0x0033, 0x0e06, 0x1033, 0x2033, 0x0034, 0x0e07, 0x1034, 0x2034,
+ 0x0035, 0x0e08, 0x1035, 0x2035, 0x0036, 0x0e09, 0x1036, 0x2036,
+ 0x0037, 0x0e0a, 0x1037, 0x2037, 0x0038, 0x0e0b, 0x1038, 0x2038,
+ 0x0039, 0x0f04, 0x1039, 0x2039, 0x003a, 0x0f05, 0x103a, 0x203a,
+ 0x003b, 0x0f06, 0x103b, 0x203b, 0x003c, 0x0f07, 0x103c, 0x203c,
+ 0x0801, 0x0f08, 0x103d, 0x203d, 0x1001, 0x0f09, 0x103e, 0x203e,
+ 0x1801, 0x0f0a, 0x103f, 0x203f, 0x2001, 0x0f0b, 0x1040, 0x2040
+};
+
+struct snappy_decompressor {
+ struct source *reader; /* Underlying source of bytes to decompress */
+ const char *ip; /* Points to next buffered byte */
+ const char *ip_limit; /* Points just past buffered bytes */
+ u32 peeked; /* Bytes peeked from reader (need to skip) */
+ bool eof; /* Hit end of input without an error? */
+ char scratch[5]; /* Temporary buffer for peekfast boundaries */
+};
+
+static void
+init_snappy_decompressor(struct snappy_decompressor *d, struct source *reader)
+{
+ d->reader = reader;
+ d->ip = NULL;
+ d->ip_limit = NULL;
+ d->peeked = 0;
+ d->eof = false;
+}
+
+static void exit_snappy_decompressor(struct snappy_decompressor *d)
+{
+ skip(d->reader, d->peeked);
+}
+
+/*
+ * Read the uncompressed length stored at the start of the compressed data.
+ * On succcess, stores the length in *result and returns true.
+ * On failure, returns false.
+ */
+static bool read_uncompressed_length(struct snappy_decompressor *d,
+ u32 * result)
+{
+ DCHECK(d->ip == NULL); /*
+ * Must not have read anything yet
+ * Length is encoded in 1..5 bytes
+ */
+ *result = 0;
+ u32 shift = 0;
+ while (true) {
+ if (shift >= 32)
+ return false;
+ size_t n;
+ const char *ip = peek(d->reader, &n);
+ if (n == 0)
+ return false;
+ const unsigned char c = *(const unsigned char *)(ip);
+ skip(d->reader, 1);
+ *result |= (u32) (c & 0x7f) << shift;
+ if (c < 128) {
+ break;
+ }
+ shift += 7;
+ }
+ return true;
+}
+
+static bool refill_tag(struct snappy_decompressor *d);
+
+/*
+ * Process the next item found in the input.
+ * Returns true if successful, false on error or end of input.
+ */
+static void decompress_all_tags(struct snappy_decompressor *d,
+ struct writer *writer)
+{
+ const char *ip = d->ip;
+
+ /*
+ * We could have put this refill fragment only at the beginning of the loop.
+ * However, duplicating it at the end of each branch gives the compiler more
+ * scope to optimize the <ip_limit_ - ip> expression based on the local
+ * context, which overall increases speed.
+ */
+#define MAYBE_REFILL() \
+ if (d->ip_limit - ip < 5) { \
+ d->ip = ip; \
+ if (!refill_tag(d)) return; \
+ ip = d->ip; \
+ }
+
+
+ MAYBE_REFILL();
+ for (;;) {
+ if (d->ip_limit - ip < 5) {
+ d->ip = ip;
+ if (!refill_tag(d))
+ return;
+ ip = d->ip;
+ }
+
+ const unsigned char c = *(const unsigned char *)(ip++);
+
+ if ((c & 0x3) == LITERAL) {
+ u32 literal_length = (c >> 2) + 1;
+ if (writer_try_fast_append(writer, ip, d->ip_limit - ip,
+ literal_length)) {
+ DCHECK_LT(literal_length, 61);
+ ip += literal_length;
+ MAYBE_REFILL();
+ continue;
+ }
+ if (unlikely(literal_length >= 61)) {
+ /* Long literal */
+ const u32 literal_ll = literal_length - 60;
+ literal_length = (get_unaligned_le32(ip) &
+ wordmask[literal_ll]) + 1;
+ ip += literal_ll;
+ }
+
+ u32 avail = d->ip_limit - ip;
+ while (avail < literal_length) {
+ if (!writer_append(writer, ip, avail))
+ return;
+ literal_length -= avail;
+ skip(d->reader, d->peeked);
+ size_t n;
+ ip = peek(d->reader, &n);
+ avail = n;
+ d->peeked = avail;
+ if (avail == 0)
+ return; /* Premature end of input */
+ d->ip_limit = ip + avail;
+ }
+ if (!writer_append(writer, ip, literal_length))
+ return;
+ ip += literal_length;
+ MAYBE_REFILL();
+ } else {
+ const u32 entry = char_table[c];
+ const u32 trailer = get_unaligned_le32(ip) &
+ wordmask[entry >> 11];
+ const u32 length = entry & 0xff;
+ ip += entry >> 11;
+
+ /*
+ * copy_offset/256 is encoded in bits 8..10.
+ * By just fetching those bits, we get
+ * copy_offset (since the bit-field starts at
+ * bit 8).
+ */
+ const u32 copy_offset = entry & 0x700;
+ if (!writer_append_from_self(writer,
+ copy_offset + trailer,
+ length))
+ return;
+ MAYBE_REFILL();
+ }
+ }
+}
+
+#undef MAYBE_REFILL
+
+static bool refill_tag(struct snappy_decompressor *d)
+{
+ const char *ip = d->ip;
+
+ if (ip == d->ip_limit) {
+ size_t n;
+ /* Fetch a new fragment from the reader */
+ skip(d->reader, d->peeked); /* All peeked bytes are used up */
+ ip = peek(d->reader, &n);
+ d->peeked = n;
+ if (n == 0) {
+ d->eof = true;
+ return false;
+ }
+ d->ip_limit = ip + n;
+ }
+
+ /* Read the tag character */
+ DCHECK_LT(ip, d->ip_limit);
+ const unsigned char c = *(const unsigned char *)(ip);
+ const u32 entry = char_table[c];
+ const u32 needed = (entry >> 11) + 1; /* +1 byte for 'c' */
+ DCHECK_LE(needed, sizeof(d->scratch));
+
+ /* Read more bytes from reader if needed */
+ u32 nbuf = d->ip_limit - ip;
+
+ if (nbuf < needed) {
+ /*
+ * Stitch together bytes from ip and reader to form the word
+ * contents. We store the needed bytes in "scratch". They
+ * will be consumed immediately by the caller since we do not
+ * read more than we need.
+ */
+ memmove(d->scratch, ip, nbuf);
+ skip(d->reader, d->peeked); /* All peeked bytes are used up */
+ d->peeked = 0;
+ while (nbuf < needed) {
+ size_t length;
+ const char *src = peek(d->reader, &length);
+ if (length == 0)
+ return false;
+ u32 to_add = min_t(u32, needed - nbuf, length);
+ memcpy(d->scratch + nbuf, src, to_add);
+ nbuf += to_add;
+ skip(d->reader, to_add);
+ }
+ DCHECK_EQ(nbuf, needed);
+ d->ip = d->scratch;
+ d->ip_limit = d->scratch + needed;
+ } else if (nbuf < 5) {
+ /*
+ * Have enough bytes, but move into scratch so that we do not
+ * read past end of input
+ */
+ memmove(d->scratch, ip, nbuf);
+ skip(d->reader, d->peeked); /* All peeked bytes are used up */
+ d->peeked = 0;
+ d->ip = d->scratch;
+ d->ip_limit = d->scratch + nbuf;
+ } else {
+ /* Pass pointer to buffer returned by reader. */
+ d->ip = ip;
+ }
+ return true;
+}
+
+static int internal_uncompress(struct source *r,
+ struct writer *writer, u32 max_len)
+{
+ struct snappy_decompressor decompressor;
+ u32 uncompressed_len = 0;
+
+ init_snappy_decompressor(&decompressor, r);
+
+ if (!read_uncompressed_length(&decompressor, &uncompressed_len))
+ return -EIO;
+ /* Protect against possible DoS attack */
+ if ((u64) (uncompressed_len) > max_len)
+ return -EIO;
+
+ writer_set_expected_length(writer, uncompressed_len);
+
+ /* Process the entire input */
+ decompress_all_tags(&decompressor, writer);
+
+ exit_snappy_decompressor(&decompressor);
+ return (decompressor.eof && writer_check_length(writer)) ? 0 : -EIO;
+}
+
+static inline int compress(struct snappy_env *env, struct source *reader,
+ struct sink *writer)
+{
+ int err;
+ size_t written = 0;
+ int N = available(reader);
+ char ulength[kmax32];
+ char *p = varint_encode32(ulength, N);
+
+ append(writer, ulength, p - ulength);
+ written += (p - ulength);
+
+ while (N > 0) {
+ /* Get next block to compress (without copying if possible) */
+ size_t fragment_size;
+ const char *fragment = peek(reader, &fragment_size);
+ if (fragment_size == 0) {
+ err = -EIO;
+ goto out;
+ }
+ const unsigned num_to_read = min_t(int, N, kblock_size);
+ size_t bytes_read = fragment_size;
+
+ int pending_advance = 0;
+ if (bytes_read >= num_to_read) {
+ /* Buffer returned by reader is large enough */
+ pending_advance = num_to_read;
+ fragment_size = num_to_read;
+ }
+ else {
+ memcpy(env->scratch, fragment, bytes_read);
+ skip(reader, bytes_read);
+
+ while (bytes_read < num_to_read) {
+ fragment = peek(reader, &fragment_size);
+ size_t n =
+ min_t(size_t, fragment_size,
+ num_to_read - bytes_read);
+ memcpy((char *)(env->scratch) + bytes_read, fragment, n);
+ bytes_read += n;
+ skip(reader, n);
+ }
+ DCHECK_EQ(bytes_read, num_to_read);
+ fragment = env->scratch;
+ fragment_size = num_to_read;
+ }
+ if (fragment_size < num_to_read)
+ return -EIO;
+
+ /* Get encoding table for compression */
+ int table_size;
+ u16 *table = get_hash_table(env, num_to_read, &table_size);
+
+ /* Compress input_fragment and append to dest */
+ char *dest;
+ dest = sink_peek(writer, snappy_max_compressed_length(num_to_read));
+ if (!dest) {
+ /*
+ * Need a scratch buffer for the output,
+ * because the byte sink doesn't have enough
+ * in one piece.
+ */
+ dest = env->scratch_output;
+ }
+ char *end = compress_fragment(fragment, fragment_size,
+ dest, table, table_size);
+ append(writer, dest, end - dest);
+ written += (end - dest);
+
+ N -= num_to_read;
+ skip(reader, pending_advance);
+ }
+
+ err = 0;
+out:
+ return err;
+}
+
+#ifdef SG
+
+int snappy_compress_iov(struct snappy_env *env,
+ struct iovec *iov_in,
+ int iov_in_len,
+ size_t input_length,
+ struct iovec *iov_out,
+ int *iov_out_len,
+ size_t *compressed_length)
+{
+ struct source reader = {
+ .iov = iov_in,
+ .iovlen = iov_in_len,
+ .total = input_length
+ };
+ struct sink writer = {
+ .iov = iov_out,
+ .iovlen = *iov_out_len,
+ };
+ int err = compress(env, &reader, &writer);
+
+ *iov_out_len = writer.curvec + 1;
+
+ /* Compute how many bytes were added */
+ *compressed_length = writer.written;
+ return err;
+}
+EXPORT_SYMBOL(snappy_compress_iov);
+
+/**
+ * snappy_compress - Compress a buffer using the snappy compressor.
+ * @env: Preallocated environment
+ * @input: Input buffer
+ * @input_length: Length of input_buffer
+ * @compressed: Output buffer for compressed data
+ * @compressed_length: The real length of the output written here.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ *
+ * The output buffer must be at least
+ * snappy_max_compressed_length(input_length) bytes long.
+ *
+ * Requires a preallocated environment from snappy_init_env.
+ * The environment does not keep state over individual calls
+ * of this function, just preallocates the memory.
+ */
+int snappy_compress(struct snappy_env *env,
+ const char *input,
+ size_t input_length,
+ char *compressed, size_t *compressed_length)
+{
+ struct iovec iov_in = {
+ .iov_base = (char *)input,
+ .iov_len = input_length,
+ };
+ struct iovec iov_out = {
+ .iov_base = compressed,
+ .iov_len = 0xffffffff,
+ };
+ int out = 1;
+ return snappy_compress_iov(env,
+ &iov_in, 1, input_length,
+ &iov_out, &out, compressed_length);
+}
+EXPORT_SYMBOL(snappy_compress);
+
+int snappy_uncompress_iov(struct iovec *iov_in, int iov_in_len,
+ size_t input_len, char *uncompressed)
+{
+ struct source reader = {
+ .iov = iov_in,
+ .iovlen = iov_in_len,
+ .total = input_len
+ };
+ struct writer output = {
+ .base = uncompressed,
+ .op = uncompressed
+ };
+ return internal_uncompress(&reader, &output, 0xffffffff);
+}
+EXPORT_SYMBOL(snappy_uncompress_iov);
+
+/**
+ * snappy_uncompress - Uncompress a snappy compressed buffer
+ * @compressed: Input buffer with compressed data
+ * @n: length of compressed buffer
+ * @uncompressed: buffer for uncompressed data
+ *
+ * The uncompressed data buffer must be at least
+ * snappy_uncompressed_length(compressed) bytes long.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ */
+int snappy_uncompress(const char *compressed, size_t n, char *uncompressed)
+{
+ struct iovec iov = {
+ .iov_base = (char *)compressed,
+ .iov_len = n
+ };
+ return snappy_uncompress_iov(&iov, 1, n, uncompressed);
+}
+EXPORT_SYMBOL(snappy_uncompress);
+
+#else
+/**
+ * snappy_compress - Compress a buffer using the snappy compressor.
+ * @env: Preallocated environment
+ * @input: Input buffer
+ * @input_length: Length of input_buffer
+ * @compressed: Output buffer for compressed data
+ * @compressed_length: The real length of the output written here.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ *
+ * The output buffer must be at least
+ * snappy_max_compressed_length(input_length) bytes long.
+ *
+ * Requires a preallocated environment from snappy_init_env.
+ * The environment does not keep state over individual calls
+ * of this function, just preallocates the memory.
+ */
+int snappy_compress(struct snappy_env *env,
+ const char *input,
+ size_t input_length,
+ char *compressed, size_t *compressed_length)
+{
+ struct source reader = {
+ .ptr = input,
+ .left = input_length
+ };
+ struct sink writer = {
+ .dest = compressed,
+ };
+ int err = compress(env, &reader, &writer);
+
+ /* Compute how many bytes were added */
+ *compressed_length = (writer.dest - compressed);
+ return err;
+}
+EXPORT_SYMBOL(snappy_compress);
+
+/**
+ * snappy_uncompress - Uncompress a snappy compressed buffer
+ * @compressed: Input buffer with compressed data
+ * @n: length of compressed buffer
+ * @uncompressed: buffer for uncompressed data
+ *
+ * The uncompressed data buffer must be at least
+ * snappy_uncompressed_length(compressed) bytes long.
+ *
+ * Return 0 on success, otherwise an negative error code.
+ */
+int snappy_uncompress(const char *compressed, size_t n, char *uncompressed)
+{
+ struct source reader = {
+ .ptr = compressed,
+ .left = n
+ };
+ struct writer output = {
+ .base = uncompressed,
+ .op = uncompressed
+ };
+ return internal_uncompress(&reader, &output, 0xffffffff);
+}
+EXPORT_SYMBOL(snappy_uncompress);
+#endif
+
+#ifdef SG
+/**
+ * snappy_init_env_sg - Allocate snappy compression environment
+ * @env: Environment to preallocate
+ * @sg: Input environment ever does scather gather
+ *
+ * If false is passed to sg then multiple entries in an iovec
+ * are not legal.
+ * Returns 0 on success, otherwise negative errno.
+ * Must run in process context.
+ */
+int snappy_init_env_sg(struct snappy_env *env, bool sg)
+{
+ env->hash_table = vmalloc(sizeof(u16) * kmax_hash_table_size);
+ if (!env->hash_table)
+ goto error;
+ if (sg) {
+ env->scratch = vmalloc(kblock_size);
+ if (!env->scratch)
+ goto error;
+ env->scratch_output =
+ vmalloc(snappy_max_compressed_length(kblock_size));
+ if (!env->scratch_output)
+ goto error;
+ }
+ return 0;
+error:
+ snappy_free_env(env);
+ return -ENOMEM;
+}
+EXPORT_SYMBOL(snappy_init_env_sg);
+#endif
+
+/**
+ * snappy_init_env - Allocate snappy compression environment
+ * @env: Environment to preallocate
+ *
+ * Passing multiple entries in an iovec is not allowed
+ * on the environment allocated here.
+ * Returns 0 on success, otherwise negative errno.
+ * Must run in process context.
+ */
+int snappy_init_env(struct snappy_env *env)
+{
+ env->hash_table = vmalloc(sizeof(u16) * kmax_hash_table_size);
+ if (!env->hash_table)
+ return -ENOMEM;
+ return 0;
+}
+EXPORT_SYMBOL(snappy_init_env);
+
+/**
+ * snappy_free_env - Free an snappy compression environment
+ * @env: Environment to free.
+ *
+ * Must run in process context.
+ */
+void snappy_free_env(struct snappy_env *env)
+{
+ vfree(env->hash_table);
+#ifdef SG
+ vfree(env->scratch);
+ vfree(env->scratch_output);
+#endif
+ memset(env, 0, sizeof(struct snappy_env));
+}
+EXPORT_SYMBOL(snappy_free_env);
projects / users / andresfreund / postgres.git / commitdiff