/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
 * access to either file, you may request a copy from help@hdfgroup.org.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * hdfgifwr.c  - handles writing of GIF files.
 *
 * Contains:
 *   hdfWriteGIF(fp, pic, ptype, w, h, rmap, gmap, bmap, numcols, colorstyle,
 *               comment)
 *
 * Note: slightly brain-damaged, in that it'll only write non-interlaced
 *       GIF files (in the interests of speed, or something)
 */

/*****************************************************************
 * Portions of this code Copyright (C) 1989 by Michael Mauldin.
 * Permission is granted to use this file in whole or in
 * part for any purpose, educational, recreational or commercial,
 * provided that this copyright notice is retained unchanged.
 * This software is available to all free of charge by anonymous
 * FTP and in the UUNET archives.
 *
 *
 * Authors:  Michael Mauldin (mlm@cs.cmu.edu)
 *           David Rowley (mgardi@watdcsu.waterloo.edu)
 *
 * Based on: compress.c - File compression ala IEEE Computer, June 1984.
 *
 * Spencer W. Thomas       (decvax!harpo!utah-cs!utah-gr!thomas)
 * Jim McKie               (decvax!mcvax!jim)
 * Steve Davies            (decvax!vax135!petsd!peora!srd)
 * Ken Turkowski           (decvax!decwrl!turtlevax!ken)
 * James A. Woods          (decvax!ihnp4!ames!jaw)
 * Joe Orost               (decvax!vax135!petsd!joe)
 *****************************************************************/


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "gif.h"

typedef BYTE  byte;
typedef long int count_int;

#ifdef __STDC__
static void compress(int, FILE *, byte *, int);
static void output(int);
static void cl_block(void);
static void cl_hash(count_int);
static void char_init(void);
static void char_out(int);
static void flush_char(void);
#else
static void compress(), output(), cl_block(), cl_hash();
static void char_init(), char_out(), flush_char();
#endif  /* __STDC__ */

static byte pc2nc[256];

/*************************************************************/
int hdfWriteGIF(FILE *fp, byte *pic, int ptype, int w, int h, byte *rmap,
                byte *gmap, byte *bmap, byte *pc2ncmap, int numcols,
                int colorstyle, int BitsPerPixel)
{
    int InitCodeSize;
    int i;
    byte *pic8 = pic;

    /* Shut compiler up... */
    ptype=ptype;
    rmap=rmap;
    gmap=gmap;
    bmap=bmap;
    numcols=numcols;
    colorstyle=colorstyle;

    for (i = 0; i < 256; i++) {
      pc2nc[i] = pc2ncmap[i];
    }

    if (BitsPerPixel <= 1)
        InitCodeSize = 2;
    else
        InitCodeSize = BitsPerPixel;

    if (!fp) {
        fprintf(stderr,  "WriteGIF: file not open for writing\n" );
        return (1);
    }

    compress(InitCodeSize+1, fp, pic8, w*h);

    if (ferror(fp))
        return -1;

    return  0 ;
}

/***********************************************************************/
static unsigned long cur_accum = 0;
static int           cur_bits = 0;

#define MAXCODE(n_bits)     ( (1 << (n_bits)) - 1)
#define XV_BITS 12    /* BITS was already defined on some systems */
#define HSIZE  5003            /* 80% occupancy */

typedef unsigned char   char_type;

static int n_bits;                    /* number of bits/code */
static int maxbits = XV_BITS;         /* user settable max # bits/code */
static int maxcode;                   /* maximum code, given n_bits */
static int maxmaxcode = 1 << XV_BITS; /* NEVER generate this */

static  count_int      htab [HSIZE];
static  unsigned short codetab [HSIZE];

#define HashTabOf(i)   htab[i]
#define CodeTabOf(i)   codetab[i]

static int hsize = HSIZE;            /* for dynamic table sizing */

/*
 * To save much memory, we overlay the table used by compress() with those
 * used by decompress().  The tab_prefix table is the same size and type as
 * the codetab.  The tab_suffix table needs 2**BITS characters.  We get this
 * from the beginning of htab.  The output stack uses the rest of htab, and
 * contains characters.  There is plenty of room for any possible stack (stack
 * used to be 8000 characters).
 */

static int free_ent = 0;                  /* first unused entry */

/*
 * block compression parameters -- after all codes are used up,
 * and compression rate changes, start over.
 */
static int clear_flg = 0;

static long int in_count = 1;            /* length of input */
static long int out_count = 0;           /* # of codes output (for debugging) */

/*
 * compress stdin to stdout
 *
 * Algorithm:  use open addressing double hashing (no chaining) on the prefix
 * code / next character combination.  We do a variant of Knuth's algorithm D
 * (vol. 3, sec. 6.4) along with G. Knott's relatively-prime secondary probe.
 * Here, the modular division first probe is gives way to a faster
 * exclusive-or manipulation.  Also do block compression with an adaptive
 * reset, whereby the code table is cleared when the compression ratio
 * decreases, but after the table fills.  The variable-length output codes are
 * re-sized at this point, and a special CLEAR code is generated for the
 * decompressor.  Late addition:  construct the table according to file size
 * for noticeable speed improvement on small files.  Please direct questions
 * about this implementation to ames!jaw.
 */

static int g_init_bits;
static FILE *g_outfile;

static int ClearCode;
static int EOFCode;

/********************************************************/
static void compress(int init_bits, FILE *outfile, byte *data, int len)
{
    register long fcode;
    register int i = 0;
    register int c;
    register int ent;
    register int disp;
    register int hsize_reg;
    register int hshift;

    /*
     * Set up the globals:  g_init_bits - initial number of bits g_outfile -
     * pointer to output file
     */
    g_init_bits = init_bits;
    g_outfile   = outfile;

    /* initialize 'compress' globals */
    maxbits = XV_BITS;
    maxmaxcode = 1<<XV_BITS;
    memset(htab, 0, sizeof(htab));
    memset(codetab, 0, sizeof(codetab));
    hsize = HSIZE;
    free_ent = 0;
    clear_flg = 0;
    in_count = 1;
    out_count = 0;
    cur_accum = 0;
    cur_bits = 0;

    /* Set up the necessary values */
    out_count = 0;
    clear_flg = 0;
    in_count = 1;
    maxcode = MAXCODE(n_bits = g_init_bits);

    ClearCode = (1 << (init_bits - 1));
    EOFCode = ClearCode + 1;
    free_ent = ClearCode + 2;

    char_init();
    ent = pc2nc[*data++];
    len--;

    hshift = 0;
    for (fcode = (long)hsize; fcode < 65536L; fcode *= 2L )
        hshift++;

    hshift = 8 - hshift; /* set hash code range bound */

    hsize_reg = hsize;
    cl_hash( (count_int) hsize_reg); /* clear hash table */

    output(ClearCode);

    while (len) {
        c = pc2nc[*data++];
        len--;
        in_count++;

        fcode = (long)(((long) c << maxbits) + ent);
        i = (((int) c << hshift) ^ ent);    /* xor hashing */

        if ( HashTabOf (i) == fcode ) {
            ent = CodeTabOf (i);
            continue;
        } else if ( (long)HashTabOf (i) < 0) {
            /* empty slot */
            goto nomatch;
        }

        disp = hsize_reg - i;   /* secondary hash (after G. Knott) */

        if ( i == 0 )
            disp = 1;

probe:
        if ((i -= disp) < 0)
            i += hsize_reg;

        if (HashTabOf (i) == fcode) {
            ent = CodeTabOf (i);
            continue;
        }

        if ((long)HashTabOf (i) >= 0)
            goto probe;

nomatch:
        output(ent);
        out_count++;
        ent = c;

        if (free_ent < maxmaxcode) {
            CodeTabOf (i) = free_ent++; /* code -> hashtable */
            HashTabOf (i) = fcode;
        } else {
            cl_block();
        }
    }

    /* Put out the final code */
    output(ent);
    out_count++;
    output(EOFCode);
}


/*****************************************************************
 * TAG( output )
 *
 * Output the given code.
 * Inputs:
 *      code:   A n_bits-bit integer.  If == -1, then EOF.  This assumes
 *              that n_bits =< (long)wordsize - 1.
 * Outputs:
 *      Outputs code to the file.
 * Assumptions:
 *      Chars are 8 bits long.
 * Algorithm:
 *      Maintain a BITS character long buffer (so that 8 codes will
 * fit in it exactly).  Use the VAX insv instruction to insert each
 * code in turn.  When the buffer fills up empty it and start over.
 */

static
unsigned long masks[] = { 0x0000, 0x0001, 0x0003, 0x0007, 0x000F,
                                  0x001F, 0x003F, 0x007F, 0x00FF,
                                  0x01FF, 0x03FF, 0x07FF, 0x0FFF,
                                  0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF };

static void
output(int code)
{
    cur_accum &= masks[cur_bits];

    if (cur_bits > 0)
        cur_accum |= ((long)code << cur_bits);
    else
        cur_accum = code;

    cur_bits += n_bits;

    while( cur_bits >= 8 ) {
        char_out( (int)((unsigned int) cur_accum & 0xff) );
        cur_accum >>= 8;
        cur_bits -= 8;
    }

    /*
     * If the next entry is going to be too big for the code size, then
     * increase it, if possible.
     */
    if (free_ent > maxcode || clear_flg) {
        if (clear_flg) {
            maxcode = MAXCODE (n_bits = g_init_bits);
            clear_flg = 0;
        } else {
            n_bits++;

            if ( n_bits == maxbits )
                maxcode = maxmaxcode;
            else
                maxcode = MAXCODE(n_bits);
        }
    }

    if (code == EOFCode) {
        /* At EOF, write the rest of the buffer */
        while( cur_bits > 0 ) {
            char_out( (int)((unsigned int)cur_accum & 0xff) );
            cur_accum >>= 8;
            cur_bits -= 8;
        }

        flush_char();
        fflush( g_outfile );

#ifdef FOO
        if(ferror( g_outfile))
            FatalError("unable to write GIF file");
#endif
    }
}

/********************************/
static void
cl_block(void)                  /* table clear for block compress */
{
    /* Clear out the hash table */
    cl_hash((count_int) hsize);
    free_ent = ClearCode + 2;
    clear_flg = 1;
    output(ClearCode);
}

/********************************/
static void
cl_hash(count_int hashsize)     /* reset code table */
{
    count_int *htab_p = htab+hashsize;
    long i, m1 = -1;

    i = hashsize - 16;

    do {    /* might use Sys V memset(3) here */
        *(htab_p-16) = m1;
        *(htab_p-15) = m1;
        *(htab_p-14) = m1;
        *(htab_p-13) = m1;
        *(htab_p-12) = m1;
        *(htab_p-11) = m1;
        *(htab_p-10) = m1;
        *(htab_p-9) = m1;
        *(htab_p-8) = m1;
        *(htab_p-7) = m1;
        *(htab_p-6) = m1;
        *(htab_p-5) = m1;
        *(htab_p-4) = m1;
        *(htab_p-3) = m1;
        *(htab_p-2) = m1;
        *(htab_p-1) = m1;
        htab_p -= 16;
    } while ((i -= 16) >= 0);

    for ( i += 16; i > 0; i-- )
        *--htab_p = m1;
}

/******************************************************************************
 *
 * GIF Specific routines
 *
 ******************************************************************************/

/*
 * Number of characters so far in this 'packet'
 */
static int a_count;

/*
 * Set up the 'byte output' routine
 */
static void
char_init(void)
{
    a_count = 0;
}

/*
 * Define the storage for the packet accumulator
 */
static char accum[ 256 ];

/*
 * Add a character to the end of the current packet, and if it is 254
 * characters, flush the packet to disk.
 */
static void
char_out(int c)
{
    accum[ a_count++ ] = c;

    if (a_count >= 254)
        flush_char();
}

/*
 * Flush the packet to disk, and reset the accumulator
 */
static void
flush_char(void)
{
    if (a_count > 0) {
        fputc( a_count, g_outfile );
        fwrite( accum, (size_t)1, (size_t)a_count, g_outfile);
        a_count = 0;
    }
}
