/* Copyright 2013 Google Inc. All Rights Reserved.

   Distributed under MIT license.

   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT

*/

/* Block split point selection utilities. */

#include "block_splitter.h"

#include <string.h>  /* memcpy, memset */

#include "../common/platform.h"

#include "bit_cost.h"

#include "cluster.h"

#include "command.h"

#include "fast_log.h"

#include "histogram.h"

#include "memory.h"

#include "quality.h"

#if defined(__cplusplus) || defined(c_plusplus)

extern "C" {

#endif

static const size_t kMaxLiteralHistograms = 100;

static const size_t kMaxCommandHistograms = 50;

static const double kLiteralBlockSwitchCost = 28.1;

static const double kCommandBlockSwitchCost = 13.5;

static const double kDistanceBlockSwitchCost = 14.6;

static const size_t kLiteralStrideLength = 70;

static const size_t kCommandStrideLength = 40;

static const size_t kDistanceStrideLength = 40;

static const size_t kSymbolsPerLiteralHistogram = 544;

static const size_t kSymbolsPerCommandHistogram = 530;

static const size_t kSymbolsPerDistanceHistogram = 544;

static const size_t kMinLengthForBlockSplitting = 128;

static const size_t kIterMulForRefining = 2;

static const size_t kMinItersForRefining = 100;

static size_t CountLiterals(const Command* cmds, const size_t num_commands) {

  /* Count how many we have. */

  size_t total_length = 0;

  size_t i;

  for (i = 0; i < num_commands; ++i) {

    total_length += cmds[i].insert_len_;

  }

  return total_length;

}

static void CopyLiteralsToByteArray(const Command* cmds,

                                    const size_t num_commands,

                                    const uint8_t* data,

                                    const size_t offset,

                                    const size_t mask,

                                    uint8_t* literals) {

  size_t pos = 0;

  size_t from_pos = offset & mask;

  size_t i;

  for (i = 0; i < num_commands; ++i) {

    size_t insert_len = cmds[i].insert_len_;

    if (from_pos + insert_len > mask) {

      size_t head_size = mask + 1 - from_pos;

      memcpy(literals + pos, data + from_pos, head_size);

      from_pos = 0;

      pos += head_size;

      insert_len -= head_size;

    }

    if (insert_len > 0) {

      memcpy(literals + pos, data + from_pos, insert_len);

      pos += insert_len;

    }

    from_pos = (from_pos + insert_len + CommandCopyLen(&cmds[i])) & mask;

  }

}

static BROTLI_INLINE uint32_t MyRand(uint32_t* seed) {

  /* Initial seed should be 7. In this case, loop length is (1 << 29). */

  *seed *= 16807U;

  return *seed;

}

static BROTLI_INLINE double BitCost(size_t count) {

  return count == 0 ? -2.0 : FastLog2(count);

}

#define HISTOGRAMS_PER_BATCH 64

#define CLUSTERS_PER_BATCH 16

#define FN(X) X ## Literal

#define DataType uint8_t

/* NOLINTNEXTLINE(build/include) */

#include "block_splitter_inc.h"

#undef DataType

#undef FN

#define FN(X) X ## Command

#define DataType uint16_t

/* NOLINTNEXTLINE(build/include) */

#include "block_splitter_inc.h"

#undef FN

#define FN(X) X ## Distance

/* NOLINTNEXTLINE(build/include) */

#include "block_splitter_inc.h"

#undef DataType

#undef FN

void BrotliInitBlockSplit(BlockSplit* self) {

  self->num_types = 0;

  self->num_blocks = 0;

  self->types = 0;

  self->lengths = 0;

  self->types_alloc_size = 0;

  self->lengths_alloc_size = 0;

}

void BrotliDestroyBlockSplit(MemoryManager* m, BlockSplit* self) {

  BROTLI_FREE(m, self->types);

  BROTLI_FREE(m, self->lengths);

}

/* Extracts literals, command distance and prefix codes, then applies

 * SplitByteVector to create partitioning. */

void BrotliSplitBlock(MemoryManager* m,

                      const Command* cmds,

                      const size_t num_commands,

                      const uint8_t* data,

                      const size_t pos,

                      const size_t mask,

                      const BrotliEncoderParams* params,

                      BlockSplit* literal_split,

                      BlockSplit* insert_and_copy_split,

                      BlockSplit* dist_split) {

  {

    size_t literals_count = CountLiterals(cmds, num_commands);

    uint8_t* literals = BROTLI_ALLOC(m, uint8_t, literals_count);

    if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(literals)) return;

    /* Create a continuous array of literals. */

    CopyLiteralsToByteArray(cmds, num_commands, data, pos, mask, literals);

    /* Create the block split on the array of literals.

     * Literal histograms can have alphabet size up to 256.

     * Though, to accomodate context modeling, less than half of maximum size

     * is allowed. */

    SplitByteVectorLiteral(

        m, literals, literals_count,

        kSymbolsPerLiteralHistogram, kMaxLiteralHistograms,

        kLiteralStrideLength, kLiteralBlockSwitchCost, params,

        literal_split);

    if (BROTLI_IS_OOM(m)) return;

    BROTLI_FREE(m, literals);

    /* NB: this might be a good place for injecting extra splitting without

     *     increasing encoder complexity; however, output parition would be less

     *     optimal than one produced with forced splitting inside

     *     SplitByteVector (FindBlocks / ClusterBlocks). */

  }

  {

    /* Compute prefix codes for commands. */

    uint16_t* insert_and_copy_codes = BROTLI_ALLOC(m, uint16_t, num_commands);

    size_t i;

    if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(insert_and_copy_codes)) return;

    for (i = 0; i < num_commands; ++i) {

      insert_and_copy_codes[i] = cmds[i].cmd_prefix_;

    }

    /* Create the block split on the array of command prefixes. */

    SplitByteVectorCommand(

        m, insert_and_copy_codes, num_commands,

        kSymbolsPerCommandHistogram, kMaxCommandHistograms,

        kCommandStrideLength, kCommandBlockSwitchCost, params,

        insert_and_copy_split);

    if (BROTLI_IS_OOM(m)) return;

    /* TODO(eustas): reuse for distances? */

    BROTLI_FREE(m, insert_and_copy_codes);

  }

  {

    /* Create a continuous array of distance prefixes. */

    uint16_t* distance_prefixes = BROTLI_ALLOC(m, uint16_t, num_commands);

    size_t j = 0;

    size_t i;

    if (BROTLI_IS_OOM(m) || BROTLI_IS_NULL(distance_prefixes)) return;

    for (i = 0; i < num_commands; ++i) {

      const Command* cmd = &cmds[i];

      if (CommandCopyLen(cmd) && cmd->cmd_prefix_ >= 128) {

        distance_prefixes[j++] = cmd->dist_prefix_ & 0x3FF;

      }

    }

    /* Create the block split on the array of distance prefixes. */

    SplitByteVectorDistance(

        m, distance_prefixes, j,

        kSymbolsPerDistanceHistogram, kMaxCommandHistograms,

        kDistanceStrideLength, kDistanceBlockSwitchCost, params,

        dist_split);

    if (BROTLI_IS_OOM(m)) return;

    BROTLI_FREE(m, distance_prefixes);

  }

}

#if defined(BROTLI_TEST)

size_t CountLiteralsForTest(const Command*, const size_t);

size_t CountLiteralsForTest(const Command* cmds, const size_t num_commands) {

  return CountLiterals(cmds, num_commands);

}

void CopyLiteralsToByteArrayForTest(const Command*,

    const size_t, const uint8_t*, const size_t, const size_t, uint8_t*);

void CopyLiteralsToByteArrayForTest(const Command* cmds,

    const size_t num_commands, const uint8_t* data, const size_t offset,

    const size_t mask, uint8_t* literals) {

  CopyLiteralsToByteArray(cmds, num_commands, data, offset, mask, literals);

}

#endif

#if defined(__cplusplus) || defined(c_plusplus)

}  /* extern "C" */

#endif