path: root/src/bencode.c

/*
 * C implementation of a bencode decoder.
 * This is the format defined by BitTorrent:
 *  http://wiki.theory.org/BitTorrentSpecification#bencoding
 *
 * The only external requirements are a few [standard] function calls and
 * the gint64 type.  Any sane system should provide all of these things.
 *
 * See the bencode.h header file for usage information.
 *
 * This is released into the public domain:
 *  http://en.wikipedia.org/wiki/Public_Domain
 *
 * Written by:
 *   Mike Frysinger <vapier@gmail.com>
 * And improvements from:
 *   Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
 */

/*
 * This implementation isn't optimized at all as I wrote it to support a bogus
 * system.  I have no real interest in this format.  Feel free to send me
 * patches (so long as you don't copyright them and you release your changes
 * into the public domain as well).
 */

#include <stdlib.h>             /* malloc() realloc() free() strtoll() */
#include <string.h>             /* memset() */
#include <ctype.h>

#include <glib.h>

#include "bencode.h"

static be_node *be_alloc(be_type type)
{
    be_node *ret = g_malloc0(sizeof(be_node));
    if (ret)
        ret->type = type;
    return ret;
}

static gint64 _be_decode_int(const char **data, gint64 * data_len)
{
    char *endp;
    gint64 ret = strtoll(*data, &endp, 10);
    *data_len -= (endp - *data);
    *data = endp;
    return ret;
}

gint64 be_str_len(be_node * node)
{
    gint64 ret = 0;
    if (node->val.s)
        memcpy(&ret, node->val.s - sizeof(ret), sizeof(ret));
    return ret;
}

static char *_be_decode_str(const char **data, gint64 * data_len)
{
    gint64 sllen = _be_decode_int(data, data_len);
    long slen = sllen;
    unsigned long len;
    char *ret = NULL;

    /* slen is signed, so negative values get rejected */
    if (sllen < 0)
        return ret;

    /* reject attempts to allocate large values that overflow the
     * size_t type which is used with malloc()
     */
    if (sizeof(gint64) != sizeof(long))
        if (sllen != slen)
            return ret;

    /* make sure we have enough data left */
    if (sllen > *data_len - 1)
        return ret;

    /* switch from signed to unsigned so we don't overflow below */
    len = slen;

    if (**data == ':') {
        char *_ret = g_malloc(sizeof(sllen) + len + 1);
        memcpy(_ret, &sllen, sizeof(sllen));
        ret = _ret + sizeof(sllen);
        memcpy(ret, *data + 1, len);
        ret[len] = '\0';
        *data += len + 1;
        *data_len -= len + 1;
    }
    return ret;
}

static be_node *_be_decode(const char **data, gint64 * data_len)
{
    be_node *ret = NULL;
    char dc;

    if (!*data_len)
        return ret;

    dc = **data;
    if (dc == 'l') {
        unsigned int i = 0;

        ret = be_alloc(BE_LIST);

        --(*data_len);
        ++(*data);
        while (**data != 'e') {
            ret->val.l =
                g_realloc(ret->val.l, (i + 2) * sizeof(*ret->val.l));
            ret->val.l[i] = _be_decode(data, data_len);
            if (!ret->val.l[i])
                break;
            ++i;
        }
        --(*data_len);
        ++(*data);

        if (i > 0)
            ret->val.l[i] = NULL;

        return ret;
    } else if (dc == 'd') {
        unsigned int i = 0;

        ret = be_alloc(BE_DICT);

        --(*data_len);
        ++(*data);
        while (**data != 'e') {
            ret->val.d =
                g_realloc(ret->val.d, (i + 2) * sizeof(*ret->val.d));
            ret->val.d[i].key = _be_decode_str(data, data_len);
            ret->val.d[i].val = _be_decode(data, data_len);
            if (!ret->val.l[i])
                break;
            ++i;
        }
        --(*data_len);
        ++(*data);

        if (i > 0)
            ret->val.d[i].val = NULL;

        return ret;
    } else if (dc == 'i') {
        ret = be_alloc(BE_INT);

        --(*data_len);
        ++(*data);
        ret->val.i = _be_decode_int(data, data_len);
        if (**data != 'e')
            return NULL;
        --(*data_len);
        ++(*data);

        return ret;
    } else if (isdigit(dc)) {
        ret = be_alloc(BE_STR);

        ret->val.s = _be_decode_str(data, data_len);
        return ret;
    }

    return ret;
}

be_node *be_decoden(const char *data, gint64 len)
{
    return _be_decode(&data, &len);
}

be_node *be_decode(const char *data)
{
    return be_decoden(data, strlen(data));
}

gboolean be_validate_node(be_node * node, gint type)
{
    if (!node || node->type != type)
        return FALSE;
    else
        return TRUE;
}

static inline void _be_free_str(char *str)
{
    if (str)
        g_free(str - sizeof(gint64));
}

void be_free(be_node * node)
{
    switch (node->type) {
    case BE_STR:
        _be_free_str(node->val.s);
        break;

    case BE_INT:
        break;

    case BE_LIST:
        {
            unsigned int i;
            if (node->val.l) {
                for (i = 0; node->val.l[i]; ++i)
                    be_free(node->val.l[i]);
                g_free(node->val.l);
            }
            break;
        }

    case BE_DICT:
        {
            unsigned int i;
            if (node->val.d) {
                for (i = 0; node->val.d[i].val; ++i) {
                    _be_free_str(node->val.d[i].key);
                    be_free(node->val.d[i].val);
                }
                g_free(node->val.d);
            }
            break;
        }
    }
    g_free(node);
}

be_node *be_dict_find(be_node * node, char *key, int type)
{
    int i;
    for (i = 0; node->val.d[i].val; ++i) {
        if (!strcmp(node->val.d[i].key, key)) {
            be_node *cn = node->val.d[i].val;
            if (type < 0 || cn->type == type)
                return node->val.d[i].val;
        }
    }
    return NULL;
}

#ifdef BE_DEBUG
#include <stdio.h>
#include <stdint.h>

static void _be_dump_indent(ssize_t indent)
{
    while (indent-- > 0)
        printf("    ");
}

static void _be_dump(be_node * node, ssize_t indent)
{
    size_t i;

    _be_dump_indent(indent);
    indent = abs(indent);

    switch (node->type) {
    case BE_STR:
        printf("str = %s (len = %lli)\n", node->val.s, be_str_len(node));
        break;

    case BE_INT:
        printf("int = %lli\n", node->val.i);
        break;

    case BE_LIST:
        puts("list [");

        for (i = 0; node->val.l[i]; ++i)
            _be_dump(node->val.l[i], indent + 1);

        _be_dump_indent(indent);
        puts("]");
        break;

    case BE_DICT:
        puts("dict {");

        for (i = 0; node->val.d[i].val; ++i) {
            _be_dump_indent(indent + 1);
            printf("%s => ", node->val.d[i].key);
            _be_dump(node->val.d[i].val, -(indent + 1));
        }

        _be_dump_indent(indent);
        puts("}");
        break;
    }
}

void be_dump(be_node * node)
{
    _be_dump(node, 0);
}
#endif