Subversion Repositories planix.SVN

Rev

Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
2 - 1 
#include	<u.h>
2 
#include	<libc.h>
3 
#include	<bio.h>
4 
#include	"sky.h"
5 
 
6 
static int hufvals[] = {
7 
	 1,  1,  1,  1,  1,  1,  1,  1,
8 
	 2,  2,  2,  2,  2,  2,  2,  2,
9 
	 4,  4,  4,  4,  4,  4,  4,  4,
10 
	 8,  8,  8,  8,  8,  8,  8,  8,
11 
	 3,  3,  3,  3,  5,  5,  5,  5,
12 
	10, 10, 10, 10, 12, 12, 12, 12,
13 
	15, 15, 15, 15,  6,  6,  7,  7,
14 
	 9,  9, 11, 11, 13, 13,  0, 14,
15 
};
16 
 
17 
static int huflens[] = {
18 
	3, 3, 3, 3, 3, 3, 3, 3,
19 
	3, 3, 3, 3, 3, 3, 3, 3,
20 
	3, 3, 3, 3, 3, 3, 3, 3,
21 
	3, 3, 3, 3, 3, 3, 3, 3,
22 
	4, 4, 4, 4, 4, 4, 4, 4,
23 
	4, 4, 4, 4, 4, 4, 4, 4,
24 
	4, 4, 4, 4, 5, 5, 5, 5,
25 
	5, 5, 5, 5, 5, 5, 6, 6,
26 
};
27 
 
28 
static	int	buffer;
29 
static	int	bits_to_go;		/* Number of bits still in buffer */
30 
 
31 
void
32 
start_inputing_bits(void)
33 
{
34 
	bits_to_go = 0;
35 
}
36 
 
37 
int
38 
input_huffman(Biobuf *infile)
39 
{
40 
	int c;
41 
 
42 
	if(bits_to_go < 6) {
43 
		c = Bgetc(infile);
44 
		if(c < 0) {
45 
			fprint(2, "input_huffman: unexpected EOF\n");
46 
			exits("format");
47 
		}
48 
		buffer = (buffer<<8) | c;
49 
		bits_to_go += 8;
50 
	}
51 
	c = (buffer >> (bits_to_go-6)) & 0x3f;
52 
	bits_to_go -= huflens[c];
53 
	return hufvals[c];
54 
}
55 
 
56 
int
57 
input_nybble(Biobuf *infile)
58 
{
59 
	int c;
60 
 
61 
	if(bits_to_go < 4) {
62 
		c = Bgetc(infile);
63 
		if(c < 0){
64 
			fprint(2, "input_nybble: unexpected EOF\n");
65 
			exits("format");
66 
		}
67 
		buffer = (buffer<<8) | c;
68 
		bits_to_go += 8;
69 
	}
70 
 
71 
	/*
72 
	 * pick off the first 4 bits
73 
	 */
74 
	bits_to_go -= 4;
75 
	return (buffer>>bits_to_go) & 0x0f;
76 
}