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zstd/contrib/seekable_format/zstdseek_decompress.c
Yoni Gilad 618bf84e0d seekable_format: Prevent rereading frame when seeking forward 
When decompressing a seekable file, if seeking forward within
a frame (by issuing multiple ZSTD_seekable_decompress calls
with a small gap between them), the frame will be unnecessarily
reread from the beginning. This patch makes it continue using
the current frame data and simply skip over the unneeded bytes.
2023-03-29 21:24:12 -07:00

596 lines
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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
* All rights reserved.
*
* This source code is licensed under both the BSD-style license (found in the
* LICENSE file in the root directory of this source tree) and the GPLv2 (found
* in the COPYING file in the root directory of this source tree).
* You may select, at your option, one of the above-listed licenses.
*/
/* *********************************************************
* Turn on Large Files support (>4GB) for 32-bit Linux/Unix
***********************************************************/
#if !defined(__64BIT__) || defined(__MINGW32__) /* No point defining Large file for 64 bit but MinGW-w64 requires it */
# if !defined(_FILE_OFFSET_BITS)
# define _FILE_OFFSET_BITS 64 /* turn off_t into a 64-bit type for ftello, fseeko */
# endif
# if !defined(_LARGEFILE_SOURCE) /* obsolete macro, replaced with _FILE_OFFSET_BITS */
# define _LARGEFILE_SOURCE 1 /* Large File Support extension (LFS) - fseeko, ftello */
# endif
# if defined(_AIX) || defined(__hpux)
# define _LARGE_FILES /* Large file support on 32-bits AIX and HP-UX */
# endif
#endif
/* ************************************************************
* Detect POSIX version
* PLATFORM_POSIX_VERSION = 0 for non-Unix e.g. Windows
* PLATFORM_POSIX_VERSION = 1 for Unix-like but non-POSIX
* PLATFORM_POSIX_VERSION > 1 is equal to found _POSIX_VERSION
* Value of PLATFORM_POSIX_VERSION can be forced on command line
***************************************************************/
#ifndef PLATFORM_POSIX_VERSION
# if (defined(__APPLE__) && defined(__MACH__)) || defined(__SVR4) || defined(_AIX) || defined(__hpux) /* POSIX.1-2001 (SUSv3) conformant */ \
|| defined(__DragonFly__) || defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) /* BSD distros */
/* exception rule : force posix version to 200112L,
* note: it's better to use unistd.h's _POSIX_VERSION whenever possible */
# define PLATFORM_POSIX_VERSION 200112L
/* try to determine posix version through official unistd.h's _POSIX_VERSION (https://pubs.opengroup.org/onlinepubs/7908799/xsh/unistd.h.html).
* note : there is no simple way to know in advance if <unistd.h> is present or not on target system,
* Posix specification mandates its presence and its content, but target system must respect this spec.
* It's necessary to _not_ #include <unistd.h> whenever target OS is not unix-like
* otherwise it will block preprocessing stage.
* The following list of build macros tries to "guess" if target OS is likely unix-like, and therefore can #include <unistd.h>
*/
# elif !defined(_WIN32) \
&& ( defined(__unix__) || defined(__unix) \
|| defined(__midipix__) || defined(__VMS) || defined(__HAIKU__) )
# if defined(__linux__) || defined(__linux) || defined(__CYGWIN__)
# ifndef _POSIX_C_SOURCE
# define _POSIX_C_SOURCE 200809L /* feature test macro : https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html */
# endif
# endif
# include <unistd.h> /* declares _POSIX_VERSION */
# if defined(_POSIX_VERSION) /* POSIX compliant */
# define PLATFORM_POSIX_VERSION _POSIX_VERSION
# else
# define PLATFORM_POSIX_VERSION 1
# endif
# ifdef __UCLIBC__
# ifndef __USE_MISC
# define __USE_MISC /* enable st_mtim on uclibc */
# endif
# endif
# else /* non-unix target platform (like Windows) */
# define PLATFORM_POSIX_VERSION 0
# endif
#endif /* PLATFORM_POSIX_VERSION */
/* ************************************************************
* Avoid fseek()'s 2GiB barrier with MSVC, macOS, *BSD, MinGW
***************************************************************/
#if defined(_MSC_VER) && _MSC_VER >= 1400
# define LONG_SEEK _fseeki64
#elif !defined(__64BIT__) && (PLATFORM_POSIX_VERSION >= 200112L) /* No point defining Large file for 64 bit */
# define LONG_SEEK fseeko
#elif defined(__MINGW32__) && !defined(__STRICT_ANSI__) && !defined(__NO_MINGW_LFS) && defined(__MSVCRT__)
# define LONG_SEEK fseeko64
#elif defined(_WIN32) && !defined(__DJGPP__)
# include <windows.h>
static int LONG_SEEK(FILE* file, __int64 offset, int origin) {
LARGE_INTEGER off;
DWORD method;
off.QuadPart = offset;
if (origin == SEEK_END)
method = FILE_END;
else if (origin == SEEK_CUR)
method = FILE_CURRENT;
else
method = FILE_BEGIN;
if (SetFilePointerEx((HANDLE) _get_osfhandle(_fileno(file)), off, NULL, method))
return 0;
else
return -1;
}
#else
# define LONG_SEEK fseek
#endif
#include <stdlib.h> /* malloc, free */
#include <stdio.h> /* FILE* */
#include <limits.h> /* UNIT_MAX */
#include <assert.h>
#define XXH_STATIC_LINKING_ONLY
#include "xxhash.h"
#define ZSTD_STATIC_LINKING_ONLY
#include "zstd.h"
#include "zstd_errors.h"
#include "mem.h"
#include "zstd_seekable.h"
#undef ERROR
#define ERROR(name) ((size_t)-ZSTD_error_##name)
#define CHECK_IO(f) { int const errcod = (f); if (errcod < 0) return ERROR(seekableIO); }
#undef MIN
#undef MAX
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX 16
/* Special-case callbacks for FILE* and in-memory modes, so that we can treat
* them the same way as the advanced API */
static int ZSTD_seekable_read_FILE(void* opaque, void* buffer, size_t n)
{
size_t const result = fread(buffer, 1, n, (FILE*)opaque);
if (result != n) {
return -1;
}
return 0;
}
static int ZSTD_seekable_seek_FILE(void* opaque, long long offset, int origin)
{
int const ret = LONG_SEEK((FILE*)opaque, offset, origin);
if (ret) return ret;
return fflush((FILE*)opaque);
}
typedef struct {
const void *ptr;
size_t size;
size_t pos;
} buffWrapper_t;
static int ZSTD_seekable_read_buff(void* opaque, void* buffer, size_t n)
{
buffWrapper_t* const buff = (buffWrapper_t*)opaque;
assert(buff != NULL);
if (buff->pos + n > buff->size) return -1;
memcpy(buffer, (const BYTE*)buff->ptr + buff->pos, n);
buff->pos += n;
return 0;
}
static int ZSTD_seekable_seek_buff(void* opaque, long long offset, int origin)
{
buffWrapper_t* const buff = (buffWrapper_t*) opaque;
unsigned long long newOffset;
assert(buff != NULL);
switch (origin) {
case SEEK_SET:
assert(offset >= 0);
newOffset = (unsigned long long)offset;
break;
case SEEK_CUR:
newOffset = (unsigned long long)((long long)buff->pos + offset);
break;
case SEEK_END:
newOffset = (unsigned long long)((long long)buff->size + offset);
break;
default:
assert(0); /* not possible */
}
if (newOffset > buff->size) {
return -1;
}
buff->pos = newOffset;
return 0;
}
typedef struct {
U64 cOffset;
U64 dOffset;
U32 checksum;
} seekEntry_t;
struct ZSTD_seekTable_s {
seekEntry_t* entries;
size_t tableLen;
int checksumFlag;
};
#define SEEKABLE_BUFF_SIZE ZSTD_BLOCKSIZE_MAX
struct ZSTD_seekable_s {
ZSTD_DStream* dstream;
ZSTD_seekTable seekTable;
ZSTD_seekable_customFile src;
U64 decompressedOffset;
U32 curFrame;
BYTE inBuff[SEEKABLE_BUFF_SIZE]; /* need to do our own input buffering */
BYTE outBuff[SEEKABLE_BUFF_SIZE]; /* so we can efficiently decompress the
starts of chunks before we get to the
desired section */
ZSTD_inBuffer in; /* maintain continuity across ZSTD_seekable_decompress operations */
buffWrapper_t buffWrapper; /* for `src.opaque` in in-memory mode */
XXH64_state_t xxhState;
};
ZSTD_seekable* ZSTD_seekable_create(void)
{
ZSTD_seekable* const zs = (ZSTD_seekable*)malloc(sizeof(ZSTD_seekable));
if (zs == NULL) return NULL;
/* also initializes stage to zsds_init */
memset(zs, 0, sizeof(*zs));
zs->dstream = ZSTD_createDStream();
if (zs->dstream == NULL) {
free(zs);
return NULL;
}
return zs;
}
size_t ZSTD_seekable_free(ZSTD_seekable* zs)
{
if (zs == NULL) return 0; /* support free on null */
ZSTD_freeDStream(zs->dstream);
free(zs->seekTable.entries);
free(zs);
return 0;
}
ZSTD_seekTable* ZSTD_seekTable_create_fromSeekable(const ZSTD_seekable* zs)
{
ZSTD_seekTable* const st = (ZSTD_seekTable*)malloc(sizeof(ZSTD_seekTable));
if (st==NULL) return NULL;
st->checksumFlag = zs->seekTable.checksumFlag;
st->tableLen = zs->seekTable.tableLen;
/* Allocate an extra entry at the end to match logic of initial allocation */
size_t const entriesSize = sizeof(seekEntry_t) * (zs->seekTable.tableLen + 1);
seekEntry_t* const entries = (seekEntry_t*)malloc(entriesSize);
if (entries==NULL) {
free(st);
return NULL;
}
memcpy(entries, zs->seekTable.entries, entriesSize);
st->entries = entries;
return st;
}
size_t ZSTD_seekTable_free(ZSTD_seekTable* st)
{
if (st == NULL) return 0; /* support free on null */
free(st->entries);
free(st);
return 0;
}
/** ZSTD_seekable_offsetToFrameIndex() :
* Performs a binary search to find the last frame with a decompressed offset
* <= pos
* @return : the frame's index */
unsigned ZSTD_seekable_offsetToFrameIndex(const ZSTD_seekable* zs, unsigned long long pos)
{
return ZSTD_seekTable_offsetToFrameIndex(&zs->seekTable, pos);
}
unsigned ZSTD_seekTable_offsetToFrameIndex(const ZSTD_seekTable* st, unsigned long long pos)
{
U32 lo = 0;
U32 hi = (U32)st->tableLen;
assert(st->tableLen <= UINT_MAX);
if (pos >= st->entries[st->tableLen].dOffset) {
return (unsigned)st->tableLen;
}
while (lo + 1 < hi) {
U32 const mid = lo + ((hi - lo) >> 1);
if (st->entries[mid].dOffset <= pos) {
lo = mid;
} else {
hi = mid;
}
}
return lo;
}
unsigned ZSTD_seekable_getNumFrames(const ZSTD_seekable* zs)
{
return ZSTD_seekTable_getNumFrames(&zs->seekTable);
}
unsigned ZSTD_seekTable_getNumFrames(const ZSTD_seekTable* st)
{
assert(st->tableLen <= UINT_MAX);
return (unsigned)st->tableLen;
}
unsigned long long ZSTD_seekable_getFrameCompressedOffset(const ZSTD_seekable* zs, unsigned frameIndex)
{
return ZSTD_seekTable_getFrameCompressedOffset(&zs->seekTable, frameIndex);
}
unsigned long long ZSTD_seekTable_getFrameCompressedOffset(const ZSTD_seekTable* st, unsigned frameIndex)
{
if (frameIndex >= st->tableLen) return ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE;
return st->entries[frameIndex].cOffset;
}
unsigned long long ZSTD_seekable_getFrameDecompressedOffset(const ZSTD_seekable* zs, unsigned frameIndex)
{
return ZSTD_seekTable_getFrameDecompressedOffset(&zs->seekTable, frameIndex);
}
unsigned long long ZSTD_seekTable_getFrameDecompressedOffset(const ZSTD_seekTable* st, unsigned frameIndex)
{
if (frameIndex >= st->tableLen) return ZSTD_SEEKABLE_FRAMEINDEX_TOOLARGE;
return st->entries[frameIndex].dOffset;
}
size_t ZSTD_seekable_getFrameCompressedSize(const ZSTD_seekable* zs, unsigned frameIndex)
{
return ZSTD_seekTable_getFrameCompressedSize(&zs->seekTable, frameIndex);
}
size_t ZSTD_seekTable_getFrameCompressedSize(const ZSTD_seekTable* st, unsigned frameIndex)
{
if (frameIndex >= st->tableLen) return ERROR(frameIndex_tooLarge);
return st->entries[frameIndex + 1].cOffset -
st->entries[frameIndex].cOffset;
}
size_t ZSTD_seekable_getFrameDecompressedSize(const ZSTD_seekable* zs, unsigned frameIndex)
{
return ZSTD_seekTable_getFrameDecompressedSize(&zs->seekTable, frameIndex);
}
size_t ZSTD_seekTable_getFrameDecompressedSize(const ZSTD_seekTable* st, unsigned frameIndex)
{
if (frameIndex > st->tableLen) return ERROR(frameIndex_tooLarge);
return st->entries[frameIndex + 1].dOffset -
st->entries[frameIndex].dOffset;
}
static size_t ZSTD_seekable_loadSeekTable(ZSTD_seekable* zs)
{
int checksumFlag;
ZSTD_seekable_customFile src = zs->src;
/* read the footer, fixed size */
CHECK_IO(src.seek(src.opaque, -(int)ZSTD_seekTableFooterSize, SEEK_END));
CHECK_IO(src.read(src.opaque, zs->inBuff, ZSTD_seekTableFooterSize));
if (MEM_readLE32(zs->inBuff + 5) != ZSTD_SEEKABLE_MAGICNUMBER) {
return ERROR(prefix_unknown);
}
{ BYTE const sfd = zs->inBuff[4];
checksumFlag = sfd >> 7;
/* check reserved bits */
if ((sfd >> 2) & 0x1f) {
return ERROR(corruption_detected);
} }
{ U32 const numFrames = MEM_readLE32(zs->inBuff);
U32 const sizePerEntry = 8 + (checksumFlag?4:0);
U32 const tableSize = sizePerEntry * numFrames;
U32 const frameSize = tableSize + ZSTD_seekTableFooterSize + ZSTD_SKIPPABLEHEADERSIZE;
U32 remaining = frameSize - ZSTD_seekTableFooterSize; /* don't need to re-read footer */
{ U32 const toRead = MIN(remaining, SEEKABLE_BUFF_SIZE);
CHECK_IO(src.seek(src.opaque, -(S64)frameSize, SEEK_END));
CHECK_IO(src.read(src.opaque, zs->inBuff, toRead));
remaining -= toRead;
}
if (MEM_readLE32(zs->inBuff) != (ZSTD_MAGIC_SKIPPABLE_START | 0xE)) {
return ERROR(prefix_unknown);
}
if (MEM_readLE32(zs->inBuff+4) + ZSTD_SKIPPABLEHEADERSIZE != frameSize) {
return ERROR(prefix_unknown);
}
{ /* Allocate an extra entry at the end so that we can do size
* computations on the last element without special case */
seekEntry_t* const entries = (seekEntry_t*)malloc(sizeof(seekEntry_t) * (numFrames + 1));
U32 idx = 0;
U32 pos = 8;
U64 cOffset = 0;
U64 dOffset = 0;
if (entries == NULL) return ERROR(memory_allocation);
/* compute cumulative positions */
for (; idx < numFrames; idx++) {
if (pos + sizePerEntry > SEEKABLE_BUFF_SIZE) {
U32 const offset = SEEKABLE_BUFF_SIZE - pos;
U32 const toRead = MIN(remaining, SEEKABLE_BUFF_SIZE - offset);
memmove(zs->inBuff, zs->inBuff + pos, offset); /* move any data we haven't read yet */
CHECK_IO(src.read(src.opaque, zs->inBuff+offset, toRead));
remaining -= toRead;
pos = 0;
}
entries[idx].cOffset = cOffset;
entries[idx].dOffset = dOffset;
cOffset += MEM_readLE32(zs->inBuff + pos);
pos += 4;
dOffset += MEM_readLE32(zs->inBuff + pos);
pos += 4;
if (checksumFlag) {
entries[idx].checksum = MEM_readLE32(zs->inBuff + pos);
pos += 4;
}
}
entries[numFrames].cOffset = cOffset;
entries[numFrames].dOffset = dOffset;
zs->seekTable.entries = entries;
zs->seekTable.tableLen = numFrames;
zs->seekTable.checksumFlag = checksumFlag;
return 0;
}
}
}
size_t ZSTD_seekable_initBuff(ZSTD_seekable* zs, const void* src, size_t srcSize)
{
zs->buffWrapper = (buffWrapper_t){src, srcSize, 0};
{ ZSTD_seekable_customFile srcFile = {&zs->buffWrapper,
&ZSTD_seekable_read_buff,
&ZSTD_seekable_seek_buff};
return ZSTD_seekable_initAdvanced(zs, srcFile); }
}
size_t ZSTD_seekable_initFile(ZSTD_seekable* zs, FILE* src)
{
ZSTD_seekable_customFile srcFile = {src, &ZSTD_seekable_read_FILE,
&ZSTD_seekable_seek_FILE};
return ZSTD_seekable_initAdvanced(zs, srcFile);
}
size_t ZSTD_seekable_initAdvanced(ZSTD_seekable* zs, ZSTD_seekable_customFile src)
{
zs->src = src;
{ const size_t seekTableInit = ZSTD_seekable_loadSeekTable(zs);
if (ZSTD_isError(seekTableInit)) return seekTableInit; }
zs->decompressedOffset = (U64)-1;
zs->curFrame = (U32)-1;
{ const size_t dstreamInit = ZSTD_initDStream(zs->dstream);
if (ZSTD_isError(dstreamInit)) return dstreamInit; }
return 0;
}
size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsigned long long offset)
{
unsigned long long const eos = zs->seekTable.entries[zs->seekTable.tableLen].dOffset;
if (offset + len > eos) {
len = eos - offset;
}
U32 targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, offset);
U32 noOutputProgressCount = 0;
size_t srcBytesRead = 0;
do {
/* check if we can continue from a previous decompress job */
if (targetFrame != zs->curFrame || offset < zs->decompressedOffset) {
zs->decompressedOffset = zs->seekTable.entries[targetFrame].dOffset;
zs->curFrame = targetFrame;
assert(zs->seekTable.entries[targetFrame].cOffset < LLONG_MAX);
CHECK_IO(zs->src.seek(zs->src.opaque,
(long long)zs->seekTable.entries[targetFrame].cOffset,
SEEK_SET));
zs->in = (ZSTD_inBuffer){zs->inBuff, 0, 0};
XXH64_reset(&zs->xxhState, 0);
ZSTD_DCtx_reset(zs->dstream, ZSTD_reset_session_only);
if (zs->buffWrapper.size && srcBytesRead > zs->buffWrapper.size) {
return ERROR(seekableIO);
}
}
while (zs->decompressedOffset < offset + len) {
size_t toRead;
ZSTD_outBuffer outTmp;
size_t prevOutPos;
size_t prevInPos;
size_t forwardProgress;
if (zs->decompressedOffset < offset) {
/* dummy decompressions until we get to the target offset */
outTmp = (ZSTD_outBuffer){zs->outBuff, (size_t) (MIN(SEEKABLE_BUFF_SIZE, offset - zs->decompressedOffset)), 0};
} else {
outTmp = (ZSTD_outBuffer){dst, len, (size_t) (zs->decompressedOffset - offset)};
}
prevOutPos = outTmp.pos;
prevInPos = zs->in.pos;
toRead = ZSTD_decompressStream(zs->dstream, &outTmp, &zs->in);
if (ZSTD_isError(toRead)) {
return toRead;
}
if (zs->seekTable.checksumFlag) {
XXH64_update(&zs->xxhState, (BYTE*)outTmp.dst + prevOutPos,
outTmp.pos - prevOutPos);
}
forwardProgress = outTmp.pos - prevOutPos;
if (forwardProgress == 0) {
if (noOutputProgressCount++ > ZSTD_SEEKABLE_NO_OUTPUT_PROGRESS_MAX) {
return ERROR(seekableIO);
}
} else {
noOutputProgressCount = 0;
}
zs->decompressedOffset += forwardProgress;
srcBytesRead += zs->in.pos - prevInPos;
if (toRead == 0) {
/* frame complete */
/* verify checksum */
if (zs->seekTable.checksumFlag &&
(XXH64_digest(&zs->xxhState) & 0xFFFFFFFFU) !=
zs->seekTable.entries[targetFrame].checksum) {
return ERROR(corruption_detected);
}
if (zs->decompressedOffset < offset + len) {
/* go back to the start and force a reset of the stream */
targetFrame = ZSTD_seekable_offsetToFrameIndex(zs, zs->decompressedOffset);
/* in this case it will fail later with corruption_detected, since last block does not have checksum */
assert(targetFrame != zs->seekTable.tableLen);
}
break;
}
/* read in more data if we're done with this buffer */
if (zs->in.pos == zs->in.size) {
toRead = MIN(toRead, SEEKABLE_BUFF_SIZE);
CHECK_IO(zs->src.read(zs->src.opaque, zs->inBuff, toRead));
zs->in.size = toRead;
zs->in.pos = 0;
}
} /* while (zs->decompressedOffset < offset + len) */
} while (zs->decompressedOffset != offset + len);
return len;
}
size_t ZSTD_seekable_decompressFrame(ZSTD_seekable* zs, void* dst, size_t dstSize, unsigned frameIndex)
{
if (frameIndex >= zs->seekTable.tableLen) {
return ERROR(frameIndex_tooLarge);
}
{ size_t const decompressedSize =
zs->seekTable.entries[frameIndex + 1].dOffset -
zs->seekTable.entries[frameIndex].dOffset;
if (dstSize < decompressedSize) {
return ERROR(dstSize_tooSmall);
}
return ZSTD_seekable_decompress(
zs, dst, decompressedSize,
zs->seekTable.entries[frameIndex].dOffset);
}
}
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