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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).
 */

#include <stdlib.h>     /* malloc, free */
#include <limits.h>     /* UINT_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"

#define CHECK_Z(f) { size_t const ret = (f); if (ret != 0) return ret; }

#undef ERROR
#define ERROR(name) ((size_t)-ZSTD_error_##name)

#undef MIN
#undef MAX
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))

typedef struct {
    U32 cSize;
    U32 dSize;
    U32 checksum;
} framelogEntry_t;

struct ZSTD_frameLog_s {
    framelogEntry_t* entries;
    U32 size;
    U32 capacity;

    int checksumFlag;

    /* for use when streaming out the seek table */
    U32 seekTablePos;
    U32 seekTableIndex;
} framelog_t;

struct ZSTD_seekable_CStream_s {
    ZSTD_CStream* cstream;
    ZSTD_frameLog framelog;

    U32 frameCSize;
    U32 frameDSize;

    XXH64_state_t xxhState;

    U32 maxFrameSize;

    int writingSeekTable;
};

static size_t ZSTD_seekable_frameLog_allocVec(ZSTD_frameLog* fl)
{
    /* allocate some initial space */
    size_t const FRAMELOG_STARTING_CAPACITY = 16;
    fl->entries = (framelogEntry_t*)malloc(
            sizeof(framelogEntry_t) * FRAMELOG_STARTING_CAPACITY);
    if (fl->entries == NULL) return ERROR(memory_allocation);
    fl->capacity = (U32)FRAMELOG_STARTING_CAPACITY;
    return 0;
}

static size_t ZSTD_seekable_frameLog_freeVec(ZSTD_frameLog* fl)
{
    if (fl != NULL) free(fl->entries);
    return 0;
}

ZSTD_frameLog* ZSTD_seekable_createFrameLog(int checksumFlag)
{
    ZSTD_frameLog* const fl = (ZSTD_frameLog*)malloc(sizeof(ZSTD_frameLog));
    if (fl == NULL) return NULL;

    if (ZSTD_isError(ZSTD_seekable_frameLog_allocVec(fl))) {
        free(fl);
        return NULL;
    }

    fl->checksumFlag = checksumFlag;
    fl->seekTablePos = 0;
    fl->seekTableIndex = 0;
    fl->size = 0;

    return fl;
}

size_t ZSTD_seekable_freeFrameLog(ZSTD_frameLog* fl)
{
    ZSTD_seekable_frameLog_freeVec(fl);
    free(fl);
    return 0;
}