-
Notifications
You must be signed in to change notification settings - Fork 0
/
decoder.c
96 lines (74 loc) · 1.83 KB
/
decoder.c
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
#include "decoder.h"
#include <stdio.h>
#include <stdlib.h>
//1 - incorrect input
//2 - couldn't open file
//3 - failed to allocate memory
//4 - file corrupted
int decode(char *filename1, char *filename2) {
if (filename1 == NULL || filename2 == NULL) {
return 1;
}
FILE *in = fopen(filename1, "rb");
if (in == NULL) {
return 2;
}
FILE *out = fopen(filename2, "w");
if (out == NULL) {
fclose(in);
return 2;
}
int size;
fread(&size, sizeof(int), 1, in);
struct node *root = read_huffman_tree(in);
if (root == NULL) {
fclose(in);
fclose(out);
return 3;
}
union buffer buf;
int count = 0;
fread(&buf.byte, sizeof(union buffer), 1, in);
for (int i = 0; i < size; ++i) {
struct node cur = *root;
while (cur.is_leaf != 1) {
if (buf.bits.bit7) {
cur = *(cur.right);
} else {
cur = *(cur.left);
}
count++;
if (count == 8) {
count = 0;
fread(&buf.byte, sizeof(union buffer), 1, in);
} else {
buf.byte <<= 1;
}
}
fputc(cur.data, out);
}
fclose(in);
fclose(out);
return 0;
}
struct node *read_huffman_tree(FILE *f) {
unsigned char is_leaf;
fread(&is_leaf, sizeof(unsigned char), 1, f);
struct node *n = (struct node *) malloc(sizeof(struct node));
if (n == NULL) {
return NULL;
}
if (is_leaf) {
char value;
fread(&value, sizeof(char), 1, f);
n->data = value;
n->is_leaf = 1;
n->left = NULL;
n->right = NULL;
} else {
n->is_leaf = 0;
n->left = read_huffman_tree(f);
n->right = read_huffman_tree(f);
}
return n;
}