Subversion Repositories planix.SVN

#include        <u.h>
#include        <libc.h>
#include        <bio.h>
#include        "sky.h"

static int hufvals[] = {
         1,  1,  1,  1,  1,  1,  1,  1,
         2,  2,  2,  2,  2,  2,  2,  2,
         4,  4,  4,  4,  4,  4,  4,  4,
         8,  8,  8,  8,  8,  8,  8,  8,
         3,  3,  3,  3,  5,  5,  5,  5,
        10, 10, 10, 10, 12, 12, 12, 12,
        15, 15, 15, 15,  6,  6,  7,  7,
         9,  9, 11, 11, 13, 13,  0, 14,
};

static int huflens[] = {
        3, 3, 3, 3, 3, 3, 3, 3,
        3, 3, 3, 3, 3, 3, 3, 3,
        3, 3, 3, 3, 3, 3, 3, 3,
        3, 3, 3, 3, 3, 3, 3, 3,
        4, 4, 4, 4, 4, 4, 4, 4,
        4, 4, 4, 4, 4, 4, 4, 4,
        4, 4, 4, 4, 5, 5, 5, 5,
        5, 5, 5, 5, 5, 5, 6, 6,
};

static  int     buffer;
static  int     bits_to_go;             /* Number of bits still in buffer */

void
start_inputing_bits(void)
{
        bits_to_go = 0;
}

int
input_huffman(Biobuf *infile)
{
        int c;

        if(bits_to_go < 6) {
                c = Bgetc(infile);
                if(c < 0) {
                        fprint(2, "input_huffman: unexpected EOF\n");
                        exits("format");
                }
                buffer = (buffer<<8) | c;
                bits_to_go += 8;
        }
        c = (buffer >> (bits_to_go-6)) & 0x3f;
        bits_to_go -= huflens[c];
        return hufvals[c];
}

int
input_nybble(Biobuf *infile)
{
        int c;

        if(bits_to_go < 4) {
                c = Bgetc(infile);
                if(c < 0){
                        fprint(2, "input_nybble: unexpected EOF\n");
                        exits("format");
                }
                buffer = (buffer<<8) | c;
                bits_to_go += 8;
        }

        /*
         * pick off the first 4 bits
         */
        bits_to_go -= 4;
        return (buffer>>bits_to_go) & 0x0f;
}