/*

 * jcphuff.c

 *

 * Copyright (C) 1995-1997, 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 progressive JPEG.

 *

 * We do not support output suspension in this module, since the library

 * currently does not allow multiple-scan files to be written with output

 * suspension.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jchuff.h"		/* Declarations shared with jchuff.c */

#ifdef C_PROGRESSIVE_SUPPORTED

/* Expanded entropy encoder object for progressive Huffman encoding. */

typedef struct {

  struct jpeg_entropy_encoder pub; /* public fields */

  /* Mode flag: TRUE for optimization, FALSE for actual data output */

  boolean gather_statistics;

  /* Bit-level coding status.

   * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.

   */

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

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

  INT32 put_buffer;		/* current bit-accumulation buffer */

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

  j_compress_ptr cinfo;		/* link to cinfo (needed for dump_buffer) */

  /* Coding status for DC components */

  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */

  /* Coding status for AC components */

  int ac_tbl_no;		/* the table number of the single component */

  unsigned int EOBRUN;		/* run length of EOBs */

  unsigned int BE;		/* # of buffered correction bits before MCU */

  char * bit_buffer;		/* buffer for correction bits (1 per char) */

  /* packing correction bits tightly would save some space but cost time... */

  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).

   * Since any one scan codes only DC or only AC, we only need one set

   * of tables, not one for DC and one for AC.

   */

  c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];

  /* Statistics tables for optimization; again, one set is enough */

  long * count_ptrs[NUM_HUFF_TBLS];

} phuff_entropy_encoder;

typedef phuff_entropy_encoder * phuff_entropy_ptr;

/* MAX_CORR_BITS is the number of bits the AC refinement correction-bit

 * buffer can hold.  Larger sizes may slightly improve compression, but

 * 1000 is already well into the realm of overkill.

 * The minimum safe size is 64 bits.

 */

#define MAX_CORR_BITS  1000	/* Max # of correction bits I can buffer */

/* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.

 * We assume that int right shift is unsigned if INT32 right shift is,

 * which should be safe.

 */

#ifdef RIGHT_SHIFT_IS_UNSIGNED

#define ISHIFT_TEMPS	int ishift_temp;

#define IRIGHT_SHIFT(x,shft)  \

	((ishift_temp = (x)) < 0 ? \

	 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \

	 (ishift_temp >> (shft)))

#else

#define ISHIFT_TEMPS

#define IRIGHT_SHIFT(x,shft)	((x) >> (shft))

#endif

/* Forward declarations */

METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,

					    JBLOCKROW *MCU_data));

METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,

					    JBLOCKROW *MCU_data));

METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,

					     JBLOCKROW *MCU_data));

METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,

					     JBLOCKROW *MCU_data));

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

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

/*

 * Initialize for a Huffman-compressed scan using progressive JPEG.

 */

METHODDEF(void)

start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)

{  

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  boolean is_DC_band;

  int ci, tbl;

  jpeg_component_info * compptr;

  entropy->cinfo = cinfo;

  entropy->gather_statistics = gather_statistics;

  is_DC_band = (cinfo->Ss == 0);

  /* We assume jcmaster.c already validated the scan parameters. */

  /* Select execution routines */

  if (cinfo->Ah == 0) {

    if (is_DC_band)

      entropy->pub.encode_mcu = encode_mcu_DC_first;

    else

      entropy->pub.encode_mcu = encode_mcu_AC_first;

  } else {

    if (is_DC_band)

      entropy->pub.encode_mcu = encode_mcu_DC_refine;

    else {

      entropy->pub.encode_mcu = encode_mcu_AC_refine;

      /* AC refinement needs a correction bit buffer */

      if (entropy->bit_buffer == NULL)

	entropy->bit_buffer = (char *)

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

				      MAX_CORR_BITS * SIZEOF(char));

    }

  }

  if (gather_statistics)

    entropy->pub.finish_pass = finish_pass_gather_phuff;

  else

    entropy->pub.finish_pass = finish_pass_phuff;

  /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1

   * for AC coefficients.

   */

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

    compptr = cinfo->cur_comp_info[ci];

    /* Initialize DC predictions to 0 */

    entropy->last_dc_val[ci] = 0;

    /* Get table index */

    if (is_DC_band) {

      if (cinfo->Ah != 0)	/* DC refinement needs no table */

	continue;

      tbl = compptr->dc_tbl_no;

    } else {

      entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;

    }

    if (gather_statistics) {

      /* Check for invalid table index */

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

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

        ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);

      /* Allocate and zero the statistics tables */

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

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

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

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

				      257 * SIZEOF(long));

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

    } else {

      /* Compute derived values for Huffman table */

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

      jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,

			      & entropy->derived_tbls[tbl]);

    }

  }

  /* Initialize AC stuff */

  entropy->EOBRUN = 0;

  entropy->BE = 0;

  /* Initialize bit buffer to empty */

  entropy->put_buffer = 0;

  entropy->put_bits = 0;

  /* Initialize restart stuff */

  entropy->restarts_to_go = cinfo->restart_interval;

  entropy->next_restart_num = 0;

}

/* Outputting bytes to the file.

 * NB: these must be called only when actually outputting,

 * that is, entropy->gather_statistics == FALSE.

 */

/* Emit a byte */

#define emit_byte(entropy,val)  \

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

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

	    dump_buffer(entropy); }

LOCAL(void)

dump_buffer (phuff_entropy_ptr entropy)

/* Empty the output buffer; we do not support suspension in this module. */

{

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

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

    ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);

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

  entropy->next_output_byte = dest->next_output_byte;

  entropy->free_in_buffer = dest->free_in_buffer;

}

/* 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(void)

emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)

/* Emit some bits, unless we are in gather mode */

{

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

  register INT32 put_buffer = (INT32) code;

  register int put_bits = entropy->put_bits;

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

  if (size == 0)

    ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

  if (entropy->gather_statistics)

    return;			/* do nothing if we're only getting stats */

  put_buffer &= (((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 |= entropy->put_buffer; /* and merge with old buffer contents */

  while (put_bits >= 8) {

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

    emit_byte(entropy, c);

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

      emit_byte(entropy, 0);

    }

    put_buffer <<= 8;

    put_bits -= 8;

  }

  entropy->put_buffer = put_buffer; /* update variables */

  entropy->put_bits = put_bits;

}

LOCAL(void)

flush_bits (phuff_entropy_ptr entropy)

{

  emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */

  entropy->put_buffer = 0;     /* and reset bit-buffer to empty */

  entropy->put_bits = 0;

}

/*

 * Emit (or just count) a Huffman symbol.

 */

INLINE

LOCAL(void)

emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)

{

  if (entropy->gather_statistics)

    entropy->count_ptrs[tbl_no][symbol]++;

  else {

    c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];

    emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);

  }

}

/*

 * Emit bits from a correction bit buffer.

 */

LOCAL(void)

emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,

		    unsigned int nbits)

{

  if (entropy->gather_statistics)

    return;			/* no real work */

  while (nbits > 0) {

    emit_bits(entropy, (unsigned int) (*bufstart), 1);

    bufstart++;

    nbits--;

  }

}

/*

 * Emit any pending EOBRUN symbol.

 */

LOCAL(void)

emit_eobrun (phuff_entropy_ptr entropy)

{

  register int temp, nbits;

  if (entropy->EOBRUN > 0) {	/* if there is any pending EOBRUN */

    temp = entropy->EOBRUN;

    nbits = 0;

    while ((temp >>= 1))

      nbits++;

    /* safety check: shouldn't happen given limited correction-bit buffer */

    if (nbits > 14)

      ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);

    emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);

    if (nbits)

      emit_bits(entropy, entropy->EOBRUN, nbits);

    entropy->EOBRUN = 0;

    /* Emit any buffered correction bits */

    emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);

    entropy->BE = 0;

  }

}

/*

 * Emit a restart marker & resynchronize predictions.

 */

LOCAL(void)

emit_restart (phuff_entropy_ptr entropy, int restart_num)

{

  int ci;

  emit_eobrun(entropy);

  if (! entropy->gather_statistics) {

    flush_bits(entropy);

    emit_byte(entropy, 0xFF);

    emit_byte(entropy, JPEG_RST0 + restart_num);

  }

  if (entropy->cinfo->Ss == 0) {

    /* Re-initialize DC predictions to 0 */

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

      entropy->last_dc_val[ci] = 0;

  } else {

    /* Re-initialize all AC-related fields to 0 */

    entropy->EOBRUN = 0;

    entropy->BE = 0;

  }

}

/*

 * MCU encoding for DC initial scan (either spectral selection,

 * or first pass of successive approximation).

 */

METHODDEF(boolean)

encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  register int temp, temp2;

  register int nbits;

  int blkn, ci;

  int Al = cinfo->Al;

  JBLOCKROW block;

  jpeg_component_info * compptr;

  ISHIFT_TEMPS

  entropy->next_output_byte = cinfo->dest->next_output_byte;

  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */

  if (cinfo->restart_interval)

    if (entropy->restarts_to_go == 0)

      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data blocks */

  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

    block = MCU_data[blkn];

    ci = cinfo->MCU_membership[blkn];

    compptr = cinfo->cur_comp_info[ci];

    /* Compute the DC value after the required point transform by Al.

     * This is simply an arithmetic right shift.

     */

    temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);

    /* DC differences are figured on the point-transformed values. */

    temp = temp2 - entropy->last_dc_val[ci];

    entropy->last_dc_val[ci] = temp2;

    /* Encode the DC coefficient difference per section G.1.2.1 */

    temp2 = temp;

    if (temp < 0) {

      temp = -temp;		/* temp is abs value of input */

      /* For a negative input, want temp2 = bitwise complement of abs(input) */

      /* This code assumes we are on a two's complement machine */

      temp2--;

    }

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

    nbits = 0;

    while (temp) {

      nbits++;

      temp >>= 1;

    }

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

     * Since we're encoding a difference, the range limit is twice as much.

     */

    if (nbits > MAX_COEF_BITS+1)

      ERREXIT(cinfo, JERR_BAD_DCT_COEF);

    /* Count/emit the Huffman-coded symbol for the number of bits */

    emit_symbol(entropy, compptr->dc_tbl_no, nbits);

    /* 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 */

      emit_bits(entropy, (unsigned int) temp2, nbits);

  }

  cinfo->dest->next_output_byte = entropy->next_output_byte;

  cinfo->dest->free_in_buffer = entropy->free_in_buffer;

  /* 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 TRUE;

}

/*

 * MCU encoding for AC initial scan (either spectral selection,

 * or first pass of successive approximation).

 */

METHODDEF(boolean)

encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  register int temp, temp2;

  register int nbits;

  register int r, k;

  int Se = cinfo->Se;

  int Al = cinfo->Al;

  JBLOCKROW block;

  entropy->next_output_byte = cinfo->dest->next_output_byte;

  entropy->free_in_buffer = cinfo->dest->free_in_buffer;

  /* Emit restart marker if needed */

  if (cinfo->restart_interval)

    if (entropy->restarts_to_go == 0)

      emit_restart(entropy, entropy->next_restart_num);

  /* Encode the MCU data block */

  block = MCU_data[0];

  /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */

  r = 0;			/* r = run length of zeros */

  for (k = cinfo->Ss; k <= Se; k++) {

    if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {

      r++;

      continue;

    }

    /* We must apply the point transform by Al.  For AC coefficients this

     * is an integer division with rounding towards 0.  To do this portably

     * in C, we shift after obtaining the absolute value; so the code is

     * interwoven with finding the abs value (temp) and output bits (temp2).

     */

    if (temp < 0) {

      temp = -temp;		/* temp is abs value of input */

      temp >>= Al;		/* apply the point transform */

      /* For a negative coef, want temp2 = bitwise complement of abs(coef) */

      temp2 = ~temp;

    } else {

      temp >>= Al;		/* apply the point transform */

      temp2 = temp;

    }

    /* Watch out for case that nonzero coef is zero after point transform */

    if (temp == 0) {

      r++;

      continue;

    }

    /* Emit any pending EOBRUN */

    if (entropy->EOBRUN > 0)

      emit_eobrun(entropy);

    /* if run length > 15, must emit special run-length-16 codes (0xF0) */

    while (r > 15) {

      emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);

      r -= 16;

    }

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

    nbits = 1;			/* there must be at least one 1 bit */

    while ((temp >>= 1))

      nbits++;

    /* Check for out-of-range coefficient values */

    if (nbits > MAX_COEF_BITS)

      ERREXIT(cinfo, JERR_BAD_DCT_COEF);