bencode2json 0.1.0

A Bencoded to JSON converter library and console app with no intermediary in-memory structure.
Documentation 
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191

/* converts Bencoded data on stdin to JSON on stdout */

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>

int pos = 0;
int c;
char stack[1024], *sp = stack;

void die()
{
    fflush(stdout);
    fprintf(stderr, "\nparse error at position %d: ", pos);
    if (c == EOF)
        fputs("got EOF\n", stderr);
    else
        fprintf(stderr, "found '%c'\n", (char)c);
    exit(1);
}

static inline int chomp()
{
    pos++;
    c = getchar();
    return c != EOF;
}

static inline void dump_int()
{
    int st = 0;

    while (chomp())
    {
        if (isdigit(c))
        {
            st = 2;
            putchar(c);
        }
        else if (c == 'e' && st == 2)
        {
            return;
        }
        else if (c == '-' && st == 0)
        {
            st = 1;
            putchar(c);
        }
        else
        {
            die();
        }
    }
}

static inline void dump_str(int len)
{
    int st = 0;

    len -= '0';
    putchar('"');
    while (chomp())
    {
        if (st == 0)
        {
            if (isdigit(c))
            {
                len = 10 * len + c - '0';
            }
            else if (c == ':')
            {
                st = 1;
                if (len == 0)
                    break;
            }
            else
                die();
        }
        else
        {
            len--;
            if (c == '"' || c == '\\')
            {
                putchar('\\');
            }
            putchar(c);
            if (len == 0)
                break;
        }
    }
    if (len > 0)
        die();
    putchar('"');
}

static void struct_hlp()
{
    switch (*sp)
    {
    case 'd':
        *sp = 'e';
        break;
    case 'e':
        putchar(':');
        *sp = 'f';
        break;
    case 'f':
        putchar(',');
        *sp = 'e';
        break;
    case 'l':
        *sp = 'm';
        break;
    case 'm':
        putchar(',');
        break;
    }
}

static inline void push(char ch)
{
    if (sp >= stack + sizeof(stack) - 1)
    {
        fputs("stack overflow\n", stderr);
        die();
    }
    *++sp = ch;
}

int main(int ac, char *av[])
{
    *sp = 'i';
    while (chomp())
    {
        switch ((char)c)
        {
        case 'd':
            struct_hlp();
            putchar('{');
            push((char)c);
            break;
        case 'l':
            struct_hlp();
            putchar('[');
            push((char)c);
            break;
        case 'i':
            struct_hlp();
            dump_int();
            break;
        case '0':
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
        case '8':
        case '9':
            struct_hlp();
            dump_str(c);
            break;
        case 'e':
            if (*sp == 'l' || *sp == 'm')
            {
                putchar(']');
                sp--;
            }
            else if (*sp == 'd' || *sp == 'f')
            {
                putchar('}');
                sp--;
            }
            else
                die();
            if (sp < stack)
                die();
            break;
        case '\n':
            break;
        default:
            die();
            break;
        }
    }
    if (sp != stack)
        die();
    putchar('\n');
    return 0;
}