76 lines
1.3 KiB
C
76 lines
1.3 KiB
C
#include <u.h>
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#include <libc.h>
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#include <bio.h>
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#include "sky.h"
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static int hufvals[] = {
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1, 1, 1, 1, 1, 1, 1, 1,
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2, 2, 2, 2, 2, 2, 2, 2,
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4, 4, 4, 4, 4, 4, 4, 4,
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8, 8, 8, 8, 8, 8, 8, 8,
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3, 3, 3, 3, 5, 5, 5, 5,
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10, 10, 10, 10, 12, 12, 12, 12,
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15, 15, 15, 15, 6, 6, 7, 7,
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9, 9, 11, 11, 13, 13, 0, 14,
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};
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static int huflens[] = {
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3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 3, 3, 3, 3, 3, 3,
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4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 4, 4, 4, 4,
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4, 4, 4, 4, 5, 5, 5, 5,
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5, 5, 5, 5, 5, 5, 6, 6,
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};
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static int buffer;
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static int bits_to_go; /* Number of bits still in buffer */
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void
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start_inputing_bits(void)
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{
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bits_to_go = 0;
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}
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int
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input_huffman(Biobuf *infile)
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{
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int c;
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if(bits_to_go < 6) {
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c = Bgetc(infile);
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if(c < 0) {
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fprint(2, "input_huffman: unexpected EOF\n");
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exits("format");
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}
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buffer = (buffer<<8) | c;
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bits_to_go += 8;
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}
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c = (buffer >> (bits_to_go-6)) & 0x3f;
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bits_to_go -= huflens[c];
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return hufvals[c];
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}
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int
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input_nybble(Biobuf *infile)
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{
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int c;
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if(bits_to_go < 4) {
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c = Bgetc(infile);
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if(c < 0){
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fprint(2, "input_nybble: unexpected EOF\n");
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exits("format");
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}
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buffer = (buffer<<8) | c;
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bits_to_go += 8;
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}
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/*
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* pick off the first 4 bits
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*/
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bits_to_go -= 4;
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return (buffer>>bits_to_go) & 0x0f;
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}
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