SimpleCompressor/bits.c at master · ggolish/SimpleCompressor · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
#include "bits.h"

static int read_bytes(BITFILE *bd);

BITFILE *bit_open(char *path, int mode)
{
    BITFILE *tmp;

    tmp = (BITFILE *)malloc(sizeof(BITFILE));
    tmp->bit_pos = 0;
    tmp->byte_pos = 0;
    tmp->mode = mode;

    if(mode == BITWRITE) {
        if((tmp->fd = open(path, O_WRONLY | O_CREAT, 0644)) == -1) {
            free(tmp);
            return NULL;
        } else {
            memset(tmp->buffer, 0, BUFFMAX * sizeof(byte_t));
            return tmp;
        }
    } else if(mode == BITREAD) {
        if((tmp->fd = open(path, O_RDONLY)) == -1) {
            free(tmp);
            return NULL;
        } else {
            if(read_bytes(tmp) == -1) {
                free(tmp);
                return NULL;
            }
            return tmp;
        }
    }

    return NULL;
}

static int read_bytes(BITFILE *bd)
{
    int num_bytes;

    memset(bd->buffer, 0, BUFFMAX * sizeof(byte_t));
    num_bytes = read(bd->fd, bd->buffer, BUFFMAX);
    bd->byte_num = num_bytes;
    return num_bytes;
}

void bit_rewind(BITFILE *bd)
{
    if(bd->mode == BITCLOSED) return;

    bd->byte_pos = 0;
    bd->bit_pos = 0;
    if(bd->mode == BITWRITE) {
        memset(bd->buffer, 0, BUFFMAX * sizeof(byte_t));
    } else {
        read_bytes(bd);
    }
}

int bit_read(BITFILE *bd)
{
    if(bd->mode != BITREAD) return -1;

    int bit;

    if(bd->bit_pos == BITESIZE) {
        bd->byte_pos++;
        bd->bit_pos = 0;
        if(bd->byte_pos == bd->byte_num) {
            bd->byte_pos = 0;
            if(read_bytes(bd) == 0) {
                return -1;
            }
        }
    }

    if (bd->buffer[bd->byte_pos] & (1 << (BITESIZE - bd->bit_pos - 1))) {
        bit = 1;
    } else {
        bit = 0;
    }

    bd->bit_pos++;
    return bit;
}

void bit_write(BITFILE *bd, int bit)
{
    if(bd->mode != BITWRITE) return;

    if(bit) {
        bd->buffer[bd->byte_pos] |= (1 << (BITESIZE - bd->bit_pos - 1));
    }

    bd->bit_pos++;
    if(bd->bit_pos == BITESIZE) {
        bd->bit_pos = 0;
        bd->byte_pos++;
        if(bd->byte_pos == BUFFMAX) {
            write(bd->fd, bd->buffer, BUFFMAX);
            bd->byte_pos = 0;
            memset(bd->buffer, 0, BUFFMAX * sizeof(byte_t));
        }
    }
}

byte_t bit_close(BITFILE *bd)
{
    if(bd->mode == BITCLOSED) return 0;

    if(bd->mode == BITREAD) {
        close(bd->fd);
        bd->mode = BITCLOSED;
        return 0;
    }

    if(bd->bit_pos > 0) {
        bd->byte_pos++;
    }

    write(bd->fd, bd->buffer, bd->byte_pos);
    close(bd->fd);
    bd->mode = BITCLOSED;

    if(bd->bit_pos)
        return BITESIZE - bd->bit_pos;
    else
        return 0;
}