/**
* Initialize torrent context before calculating hash.
*
* @param ctx context to initialize
*/
void bt_init(torrent_ctx* ctx)
{
memset(ctx, 0, sizeof(torrent_ctx));
ctx->piece_length = BT_MIN_HASH_LENGTH;
assert(BT_MIN_HASH_LENGTH == bt_default_piece_length(0));
#ifdef USE_OPENSSL
{
/* get the methods of the selected SHA1 algorithm */
rhash_hash_info *sha1_info = &rhash_info_table[3];
assert(sha1_info->info->hash_id == RHASH_SHA1);
assert(sha1_info->context_size <= (sizeof(sha1_ctx) + sizeof(unsigned long)));
ctx->sha_init = sha1_info->init;
ctx->sha_update = sha1_info->update;
ctx->sha_final = sha1_info->final;
}
#endif
SHA1_INIT(ctx);
}
/**
* Add a file info into the batch of files of given torrent.
*
* @param ctx torrent algorithm context
* @param path file path
* @param filesize file size
* @return non-zero on success, zero on fail
*/
int bt_add_file(torrent_ctx *ctx, const char* path, uint64_t filesize)
{
size_t len = strlen(path);
bt_file_info* info = (bt_file_info*)malloc(sizeof(uint64_t) + len + 1);
if(info == NULL) {
ctx->error = 1;
return 0;
}
info->size = filesize;
memcpy(info->path, path, len + 1);
if(!bt_vector_add_ptr(&ctx->files, info)) return 0;
/* recalculate piece length (but only if hashing not started yet) */
if(ctx->piece_count == 0 && ctx->index == 0) {
/* note: in case of batch of files should use a total batch size */
ctx->piece_length = bt_default_piece_length(filesize);
}
return 1;
}
/**
* Generate torrent file content
* @see http://wiki.theory.org/BitTorrentSpecification
*
* @param ctx the torrent algorithm context
*/
static void bt_generate_torrent(torrent_ctx *ctx)
{
uint64_t total_size = 0;
size_t info_start_pos;
assert(ctx->content.str == NULL);
if(ctx->piece_length == 0) {
if(ctx->files.size == 1) {
total_size = ((bt_file_info*)ctx->files.array[0])->size;
}
ctx->piece_length = bt_default_piece_length(total_size);
}
/* write torrent header to the ctx->torrent string buffer */
if((ctx->options & BT_OPT_INFOHASH_ONLY) == 0) {
bt_str_append(ctx, "d");
if(ctx->announce) {
bt_bencode_str(ctx, "8:announce", ctx->announce);
}
if(ctx->program_name) {
bt_bencode_str(ctx, "10:created by", ctx->program_name);
}
bt_bencode_int(ctx, "13:creation date", (uint64_t)time(NULL));
}
bt_str_append(ctx, "8:encoding5:UTF-8");
bt_str_append(ctx, "4:infod"); /* start info dictionary */
info_start_pos = ctx->content.length - 1;
if(ctx->files.size > 1) {
size_t i;
/* process batch torrent */
bt_str_append(ctx, "5:filesl"); /* start list of files */
/* write length and path for each file in the batch */
for(i = 0; i < ctx->files.size; i++) {
bt_file_info_append(ctx, "d6:length", "4:pathl",
(bt_file_info*)ctx->files.array[i]);
bt_str_append(ctx, "ee");
}
/* note: get_batch_name modifies path, so should be called here */
bt_bencode_str(ctx, "e4:name", get_batch_name(
((bt_file_info*)ctx->files.array[0])->path));
}
else if(ctx->files.size > 0) {
/* write size and basename of the first file */
/* in the non-batch mode other files are ignored */
bt_file_info_append(ctx, "6:length", "4:name",
(bt_file_info*)ctx->files.array[0]);
}
bt_bencode_int(ctx, "12:piece length", ctx->piece_length);
bt_str_append(ctx, "6:pieces");
bt_bencode_pieces(ctx);
if(ctx->options & BT_OPT_PRIVATE) {
bt_str_append(ctx, "7:privatei1e");
}
bt_str_append(ctx, "ee");
/* calculate BTIH */
SHA1_INIT(ctx);
SHA1_UPDATE(ctx, (unsigned char*)ctx->content.str + info_start_pos,
ctx->content.length - info_start_pos - 1);
SHA1_FINAL(ctx, ctx->btih);
}
RHASH_API size_t rhash_torrent_get_default_piece_length(uint64_t total_size)
{
return bt_default_piece_length(total_size);
}
