/*

 * jclhuff.c

 *

 * Copyright (C) 1991-1998, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains Huffman entropy encoding routines for lossless JPEG.

 *

 * Much of the complexity here has to do with supporting output suspension.

 * If the data destination module demands suspension, we want to be able to

 * back up to the start of the current MCU.  To do this, we copy state

 * variables into local working storage, and update them back to the

 * permanent JPEG objects only upon successful completion of an MCU.

 */

#define JPEG_INTERNALS

#include "jinclude12.h"

#include "jpeglib12.h"

#include "jlossls12.h"      /* Private declarations for lossless codec */

#include "jchuff12.h"       /* Declarations shared with jc*huff.c */

/* Expanded entropy encoder object for Huffman encoding.

 *

 * The savable_state subrecord contains fields that change within an MCU,

 * but must not be updated permanently until we complete the MCU.

 */

typedef struct {

  IJG_INT32 put_buffer;     /* current bit-accumulation buffer */

  int put_bits;         /* # of bits now in it */

} savable_state;

/* This macro is to work around compilers with missing or broken

 * structure assignment.  You'll need to fix this code if you have

 * such a compiler and you change MAX_COMPS_IN_SCAN.

 */

#ifndef NO_STRUCT_ASSIGN

#define ASSIGN_STATE(dest,src)  ((dest) = (src))

#else

#define ASSIGN_STATE(dest,src)  \

    ((dest).put_buffer = (src).put_buffer, \

     (dest).put_bits = (src).put_bits)

#endif

typedef struct {

  int ci, yoffset, MCU_width;

} lhe_input_ptr_info;

typedef struct {

  savable_state saved;      /* Bit buffer at start of MCU */

  /* These fields are NOT loaded into local working state. */

  unsigned int restarts_to_go;  /* MCUs left in this restart interval */

  int next_restart_num;     /* next restart number to write (0-7) */

  /* Pointers to derived tables (these workspaces have image lifespan) */

  c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];

  /* Pointers to derived tables to be used for each data unit within an MCU */

  c_derived_tbl * cur_tbls[C_MAX_DATA_UNITS_IN_MCU];

#ifdef ENTROPY_OPT_SUPPORTED    /* Statistics tables for optimization */

  long * count_ptrs[NUM_HUFF_TBLS];

  /* Pointers to stats tables to be used for each data unit within an MCU */

  long * cur_counts[C_MAX_DATA_UNITS_IN_MCU];

#endif

  /* Pointers to the proper input difference row for each group of data units

   * within an MCU.  For each component, there are Vi groups of Hi data units.

   */

  JDIFFROW input_ptr[C_MAX_DATA_UNITS_IN_MCU];

  /* Number of input pointers in use for the current MCU.  This is the sum

   * of all Vi in the MCU.

   */

  int num_input_ptrs;

  /* Information used for positioning the input pointers within the input

   * difference rows.

   */

  lhe_input_ptr_info input_ptr_info[C_MAX_DATA_UNITS_IN_MCU];

  /* Index of the proper input pointer for each data unit within an MCU */

  int input_ptr_index[C_MAX_DATA_UNITS_IN_MCU];

} lhuff_entropy_encoder;

typedef lhuff_entropy_encoder * lhuff_entropy_ptr;

/* Working state while writing an MCU.

 * This struct contains all the fields that are needed by subroutines.

 */

typedef struct {

  JOCTET * next_output_byte;    /* => next byte to write in buffer */

  size_t free_in_buffer;    /* # of byte spaces remaining in buffer */

  savable_state cur;        /* Current bit buffer & DC state */

  j_compress_ptr cinfo;     /* dump_buffer needs access to this */

} working_state;

/* Forward declarations */

METHODDEF(JDIMENSION) encode_mcus_huff (j_compress_ptr cinfo,

                    JDIFFIMAGE diff_buf,

                    JDIMENSION MCU_row_num,

                    JDIMENSION MCU_col_num,

                    JDIMENSION nMCU);

METHODDEF(void) finish_pass_huff JPP((j_compress_ptr cinfo));

#ifdef ENTROPY_OPT_SUPPORTED

METHODDEF(JDIMENSION) encode_mcus_gather (j_compress_ptr cinfo,

                      JDIFFIMAGE diff_buf,

                      JDIMENSION MCU_row_num,

                      JDIMENSION MCU_col_num,

                      JDIMENSION nMCU);

METHODDEF(void) finish_pass_gather JPP((j_compress_ptr cinfo));

#endif

/*

 * Initialize for a Huffman-compressed scan.

 * If gather_statistics is TRUE, we do not output anything during the scan,

 * just count the Huffman symbols used and generate Huffman code tables.

 */

METHODDEF(void)

start_pass_huff (j_compress_ptr cinfo, boolean gather_statistics)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsc->entropy_private;

  int ci, dctbl, sampn, ptrn, yoffset, xoffset;

  jpeg_component_info * compptr;

  if (gather_statistics) {

#ifdef ENTROPY_OPT_SUPPORTED

    losslsc->entropy_encode_mcus = encode_mcus_gather;

    losslsc->pub.entropy_finish_pass = finish_pass_gather;

#else

    ERREXIT(cinfo, JERR_NOT_COMPILED);

#endif

  } else {

    losslsc->entropy_encode_mcus = encode_mcus_huff;

    losslsc->pub.entropy_finish_pass = finish_pass_huff;

  }

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

    compptr = cinfo->cur_comp_info[ci];

    dctbl = compptr->dc_tbl_no;

    if (gather_statistics) {

#ifdef ENTROPY_OPT_SUPPORTED

      /* Check for invalid table indexes */

      /* (make_c_derived_tbl does this in the other path) */

      if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS)

    ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);

      /* Allocate and zero the statistics tables */

      /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */

      if (entropy->count_ptrs[dctbl] == NULL)

    entropy->count_ptrs[dctbl] = (long *)

      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

                      257 * SIZEOF(long));

      MEMZERO(entropy->count_ptrs[dctbl], 257 * SIZEOF(long));

#endif

    } else {

      /* Compute derived values for Huffman tables */

      /* We may do this more than once for a table, but it's not expensive */

      jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl,

                  & entropy->derived_tbls[dctbl]);

    }

  }

  /* Precalculate encoding info for each sample in an MCU of this scan */

  for (sampn = 0, ptrn = 0; sampn < cinfo->data_units_in_MCU;) {

    compptr = cinfo->cur_comp_info[cinfo->MCU_membership[sampn]];

    ci = compptr->component_index;

    /*    ci = cinfo->MCU_membership[sampn];

    compptr = cinfo->cur_comp_info[ci];*/

    for (yoffset = 0; yoffset < compptr->MCU_height; yoffset++, ptrn++) {

      /* Precalculate the setup info for each input pointer */

      entropy->input_ptr_info[ptrn].ci = ci;

      entropy->input_ptr_info[ptrn].yoffset = yoffset;

      entropy->input_ptr_info[ptrn].MCU_width = compptr->MCU_width;

      for (xoffset = 0; xoffset < compptr->MCU_width; xoffset++, sampn++) {

    /* Precalculate the input pointer index for each sample */

    entropy->input_ptr_index[sampn] = ptrn;

    /* Precalculate which tables to use for each sample */

    entropy->cur_tbls[sampn] = entropy->derived_tbls[compptr->dc_tbl_no];

    entropy->cur_counts[sampn] = entropy->count_ptrs[compptr->dc_tbl_no];

      }

    }

  }

  entropy->num_input_ptrs = ptrn;

  /* Initialize bit buffer to empty */

  entropy->saved.put_buffer = 0;

  entropy->saved.put_bits = 0;

  /* Initialize restart stuff */

  entropy->restarts_to_go = cinfo->restart_interval;

  entropy->next_restart_num = 0;

}

/* Outputting bytes to the file */

/* Emit a byte, taking 'action' if must suspend. */

#define emit_byte(state,val,action)  \

    { *(state)->next_output_byte++ = (JOCTET) (val);  \

      if (--(state)->free_in_buffer == 0)  \

        if (! dump_buffer(state))  \

          { action; } }

LOCAL(boolean)

dump_buffer (working_state * state)

/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */

{

  struct jpeg_destination_mgr * dest = state->cinfo->dest;

  if (! (*dest->empty_output_buffer) (state->cinfo))

    return FALSE;

  /* After a successful buffer dump, must reset buffer pointers */

  state->next_output_byte = dest->next_output_byte;

  state->free_in_buffer = dest->free_in_buffer;

  return TRUE;

}

/* Outputting bits to the file */

/* Only the right 24 bits of put_buffer are used; the valid bits are

 * left-justified in this part.  At most 16 bits can be passed to emit_bits

 * in one call, and we never retain more than 7 bits in put_buffer

 * between calls, so 24 bits are sufficient.

 */

INLINE

LOCAL(boolean)

emit_bits (working_state * state, unsigned int code, int size)

/* Emit some bits; return TRUE if successful, FALSE if must suspend */

{

  /* This routine is heavily used, so it's worth coding tightly. */

  register IJG_INT32 put_buffer = (IJG_INT32) code;

  register int put_bits = state->cur.put_bits;

  /* if size is 0, caller used an invalid Huffman table entry */

  if (size == 0)

    ERREXIT(state->cinfo, JERR_HUFF_MISSING_CODE);

  put_buffer &= (((IJG_INT32) 1)<<size) - 1; /* mask off any extra bits in code */

  put_bits += size;     /* new number of bits in buffer */

  put_buffer <<= 24 - put_bits; /* align incoming bits */

  put_buffer |= state->cur.put_buffer; /* and merge with old buffer contents */

  while (put_bits >= 8) {

    int c = (int) ((put_buffer >> 16) & 0xFF);

    emit_byte(state, c, return FALSE);

    if (c == 0xFF) {        /* need to stuff a zero byte? */

      emit_byte(state, 0, return FALSE);

    }

    put_buffer <<= 8;

    put_bits -= 8;

  }

  state->cur.put_buffer = put_buffer; /* update state variables */

  state->cur.put_bits = put_bits;

  return TRUE;

}

LOCAL(boolean)

flush_bits (working_state * state)

{

  if (! emit_bits(state, 0x7F, 7)) /* fill any partial byte with ones */

    return FALSE;

  state->cur.put_buffer = 0;    /* and reset bit-buffer to empty */

  state->cur.put_bits = 0;

  return TRUE;

}

/*

 * Emit a restart marker & resynchronize predictions.

 */

LOCAL(boolean)

emit_restart (working_state * state, int restart_num)

{

  /* int ci; */

  if (! flush_bits(state))

    return FALSE;

  emit_byte(state, 0xFF, return FALSE);

  emit_byte(state, JPEG_RST0 + restart_num, return FALSE);

  /* The restart counter is not updated until we successfully write the MCU. */

  return TRUE;

}

/*

 * Encode and output one nMCU's worth of Huffman-compressed differences.

 */

METHODDEF(JDIMENSION)

encode_mcus_huff (j_compress_ptr cinfo, JDIFFIMAGE diff_buf,

          JDIMENSION MCU_row_num, JDIMENSION MCU_col_num,

          JDIMENSION nMCU)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsc->entropy_private;

  working_state state;

  unsigned int mcu_num;

  int sampn, ci, yoffset, MCU_width, ptrn;

  /* jpeg_component_info * compptr; */

  /* Load up working state */

  state.next_output_byte = cinfo->dest->next_output_byte;

  state.free_in_buffer = cinfo->dest->free_in_buffer;

  ASSIGN_STATE(state.cur, entropy->saved);

  state.cinfo = cinfo;

  /* Emit restart marker if needed */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! emit_restart(&state, entropy->next_restart_num))

    return 0;

  }

  /* Set input pointer locations based on MCU_col_num */

  for (ptrn = 0; ptrn < entropy->num_input_ptrs; ptrn++) {

    ci = entropy->input_ptr_info[ptrn].ci;

    yoffset = entropy->input_ptr_info[ptrn].yoffset;

    MCU_width = entropy->input_ptr_info[ptrn].MCU_width;

    entropy->input_ptr[ptrn] =

      diff_buf[ci][MCU_row_num + (size_t)yoffset] + MCU_col_num * (size_t)MCU_width;

  }

  for (mcu_num = 0; mcu_num < nMCU; mcu_num++) {

    /* Inner loop handles the samples in the MCU */

    for (sampn = 0; sampn < cinfo->data_units_in_MCU; sampn++) {

      register int temp, temp2 /* , temp3 */ ;

      register int nbits;

      c_derived_tbl *dctbl = entropy->cur_tbls[sampn];

      /* Encode the difference per section H.1.2.2 */

      /* Input the sample difference */

      temp = *entropy->input_ptr[entropy->input_ptr_index[sampn]]++;

      if (temp & 0x8000) {  /* instead of temp < 0 */

    temp = (-temp) & 0x7FFF; /* absolute value, mod 2^16 */

    if (temp == 0)      /* special case: magnitude = 32768 */

      temp2 = temp = 0x8000;

    temp2 = ~ temp;     /* one's complement of magnitude */

      } else {

    temp &= 0x7FFF;     /* abs value mod 2^16 */

    temp2 = temp;       /* magnitude */

      }

      /* Find the number of bits needed for the magnitude of the difference */

      nbits = 0;

      while (temp) {

    nbits++;

    temp >>= 1;

      }

      /* Check for out-of-range difference values.

       */

      if (nbits > MAX_DIFF_BITS)

    ERREXIT(cinfo, JERR_BAD_DIFF);

      /* Emit the Huffman-coded symbol for the number of bits */

      if (! emit_bits(&state, dctbl->ehufco[nbits], dctbl->ehufsi[nbits]))

    return mcu_num;

      /* Emit that number of bits of the value, if positive, */

      /* or the complement of its magnitude, if negative. */

      if (nbits &&      /* emit_bits rejects calls with size 0 */

      nbits != 16)      /* special case: no bits should be emitted */

    if (! emit_bits(&state, (unsigned int) temp2, nbits))

      return mcu_num;

    }

    /* Completed MCU, so update state */

    cinfo->dest->next_output_byte = state.next_output_byte;

    cinfo->dest->free_in_buffer = state.free_in_buffer;

    ASSIGN_STATE(entropy->saved, state.cur);

    /* Update restart-interval state too */

    if (cinfo->restart_interval) {

      if (entropy->restarts_to_go == 0) {

    entropy->restarts_to_go = cinfo->restart_interval;

    entropy->next_restart_num++;

    entropy->next_restart_num &= 7;

      }

      entropy->restarts_to_go--;

    }

  }

  return nMCU;

}

/*

 * Finish up at the end of a Huffman-compressed scan.

 */

METHODDEF(void)

finish_pass_huff (j_compress_ptr cinfo)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsc->entropy_private;

  working_state state;

  /* Load up working state ... flush_bits needs it */

  state.next_output_byte = cinfo->dest->next_output_byte;

  state.free_in_buffer = cinfo->dest->free_in_buffer;

  ASSIGN_STATE(state.cur, entropy->saved);

  state.cinfo = cinfo;

  /* Flush out the last data */

  if (! flush_bits(&state))

    ERREXIT(cinfo, JERR_CANT_SUSPEND);

  /* Update state */

  cinfo->dest->next_output_byte = state.next_output_byte;

  cinfo->dest->free_in_buffer = state.free_in_buffer;

  ASSIGN_STATE(entropy->saved, state.cur);

}

/*

 * Huffman coding optimization.

 *

 * We first scan the supplied data and count the number of uses of each symbol

 * that is to be Huffman-coded. (This process MUST agree with the code above.)

 * Then we build a Huffman coding tree for the observed counts.

 * Symbols which are not needed at all for the particular image are not

 * assigned any code, which saves space in the DHT marker as well as in

 * the compressed data.

 */

#ifdef ENTROPY_OPT_SUPPORTED

/*

 * Trial-encode one nMCU's worth of Huffman-compressed differences.

 * No data is actually output, so no suspension return is possible.

 */

METHODDEF(JDIMENSION)

encode_mcus_gather (j_compress_ptr cinfo, JDIFFIMAGE diff_buf,

            JDIMENSION MCU_row_num, JDIMENSION MCU_col_num,

            JDIMENSION nMCU)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsc->entropy_private;

  unsigned int mcu_num; 

  int sampn, ci, yoffset, MCU_width, ptrn;

  /* jpeg_component_info * compptr; */

  /* Take care of restart intervals if needed */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0) {

      /* Update restart state */

      entropy->restarts_to_go = cinfo->restart_interval;

    }

    entropy->restarts_to_go--;

  }

  /* Set input pointer locations based on MCU_col_num */

  for (ptrn = 0; ptrn < entropy->num_input_ptrs; ptrn++) {

    ci = entropy->input_ptr_info[ptrn].ci;

    yoffset = entropy->input_ptr_info[ptrn].yoffset;

    MCU_width = entropy->input_ptr_info[ptrn].MCU_width;

    entropy->input_ptr[ptrn] =

      diff_buf[ci][MCU_row_num + (size_t)yoffset] + MCU_col_num * (size_t)MCU_width;

  }

  for (mcu_num = 0; mcu_num < nMCU; mcu_num++) {

    /* Inner loop handles the samples in the MCU */

    for (sampn = 0; sampn < cinfo->data_units_in_MCU; sampn++) {

      register int temp;

      register int nbits;

      /* c_derived_tbl *dctbl = entropy->cur_tbls[sampn]; */

      long * counts = entropy->cur_counts[sampn];

      /* Encode the difference per section H.1.2.2 */

      /* Input the sample difference */

      temp = *entropy->input_ptr[entropy->input_ptr_index[sampn]]++;

      if (temp & 0x8000) {  /* instead of temp < 0 */

    temp = (-temp) & 0x7FFF; /* absolute value, mod 2^16 */

    if (temp == 0)      /* special case: magnitude = 32768 */

      temp = 0x8000;

      } else

    temp &= 0x7FFF;     /* abs value mod 2^16 */

      /* Find the number of bits needed for the magnitude of the difference */

      nbits = 0;

      while (temp) {

    nbits++;

    temp >>= 1;

      }

      /* Check for out-of-range difference values.

       */

      if (nbits > MAX_DIFF_BITS)

    ERREXIT(cinfo, JERR_BAD_DIFF);

      /* Count the Huffman symbol for the number of bits */

      counts[nbits]++;

    }

  }

  return nMCU;

}

/*

 * Finish up a statistics-gathering pass and create the new Huffman tables.

 */

METHODDEF(void)

finish_pass_gather (j_compress_ptr cinfo)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy = (lhuff_entropy_ptr) losslsc->entropy_private;

  int ci, dctbl;

  jpeg_component_info * compptr;

  JHUFF_TBL **htblptr;

  boolean did_dc[NUM_HUFF_TBLS];

  /* It's important not to apply jpeg_gen_optimal_table more than once

   * per table, because it clobbers the input frequency counts!

   */

  MEMZERO(did_dc, SIZEOF(did_dc));

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

    compptr = cinfo->cur_comp_info[ci];

    dctbl = compptr->dc_tbl_no;

    if (! did_dc[dctbl]) {

      htblptr = & cinfo->dc_huff_tbl_ptrs[dctbl];

      if (*htblptr == NULL)

    *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);

      jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[dctbl]);

      did_dc[dctbl] = TRUE;

    }

  }

}

#endif /* ENTROPY_OPT_SUPPORTED */

METHODDEF(boolean)

need_optimization_pass (j_compress_ptr cinfo)

{

  (void)cinfo;

  return TRUE;

}

/*

 * Module initialization routine for Huffman entropy encoding.

 */

GLOBAL(void)

jinit_lhuff_encoder (j_compress_ptr cinfo)

{

  j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;

  lhuff_entropy_ptr entropy;

  int i;

  entropy = (lhuff_entropy_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

                SIZEOF(lhuff_entropy_encoder));

  losslsc->entropy_private = (void *) entropy;

  losslsc->pub.entropy_start_pass = start_pass_huff;

  losslsc->pub.need_optimization_pass = need_optimization_pass;

  /* Mark tables unallocated */

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

    entropy->derived_tbls[i] = NULL;

#ifdef ENTROPY_OPT_SUPPORTED

    entropy->count_ptrs[i] = NULL;

#endif

  }

}