/**
* 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);
}
/**
* Initialize torrent context before calculaing hash.
*
* @param ctx context to initalize
*/
void torrent_init(torrent_ctx* ctx)
{
memset(ctx, 0, sizeof(torrent_ctx));
ctx->blocks_hashes.blocks.destructor = free;
ctx->files.destructor = free;
ctx->piece_length = 65536;
#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);
}
/**
* Calculate message hash.
* Can be called repeatedly with chunks of the message to be hashed.
*
* @param ctx the algorithm context containing current hashing state
* @param msg message chunk
* @param size length of the message chunk
*/
void bt_update(torrent_ctx *ctx, const void* msg, size_t size)
{
const unsigned char* pmsg = (const unsigned char*)msg;
size_t rest = (size_t)(ctx->piece_length - ctx->index);
assert(ctx->index < ctx->piece_length);
while(size > 0) {
size_t left = (size < rest ? size : rest);
SHA1_UPDATE(ctx, pmsg, left);
if(size < rest) {
ctx->index += left;
break;
}
bt_store_piece_sha1(ctx);
SHA1_INIT(ctx);
ctx->index = 0;
pmsg += rest;
size -= rest;
rest = ctx->piece_length;
}
}
/**
* Calculate message hash.
* Can be called repeatedly with chunks of the message to be hashed.
*
* @param ctx the algorithm context containing current hashing state
* @param msg message chunk
* @param size length of the message chunk
*/
void torrent_update(torrent_ctx *ctx, const void* msg, size_t size)
{
unsigned char hash[20];
const unsigned char* pmsg = (const unsigned char*)msg;
size_t rest = (size_t)(ctx->piece_length - ctx->index);
assert(ctx->index < ctx->piece_length);
while(size > 0) {
size_t left = (size < rest ? size : rest);
SHA1_UPDATE(ctx, pmsg, left);
if(size < rest) {
ctx->index += left;
break;
}
SHA1_FINAL(ctx, hash);
BT_ADD_HASH(ctx, hash); /* store a piece hash */
SHA1_INIT(ctx);
ctx->index = 0;
pmsg += rest;
size -= rest;
rest = ctx->piece_length;
}
}
/**
* 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);
}
/**
* Generate torrent file content
* @see http://wiki.theory.org/BitTorrentSpecification
*
* @param ctx the torrent algorithm context
*/
static void make_torrent(torrent_ctx *ctx)
{
uint64_t total_size = 0;
size_t info_start_pos;
assert(ctx->torrent == NULL);
assert(ctx->files.size <= 1);
ctx->torrent = str_new();
if(ctx->piece_length == 0) {
if(ctx->files.size == 1) {
total_size = ((file_n_size_info*)ctx->files.array[0])->size;
}
ctx->piece_length = torrent_default_piece_length(total_size);
}
/* write torrent header to the ctx->torrent string bufer */
if((ctx->flags & BT_OPT_INFOHASH_ONLY) == 0) {
str_append(ctx->torrent, "d");
if(ctx->announce) {
str_append(ctx->torrent, "8:announce");
bt_bencode_str(ctx->torrent, ctx->announce);
}
if(ctx->program_name) {
str_append(ctx->torrent, "10:created by");
bt_bencode_str(ctx->torrent, ctx->program_name);
}
str_append(ctx->torrent, "13:creation date");
bt_bencode_int(ctx->torrent, (uint64_t)time(NULL));
}
str_append(ctx->torrent, "8:encoding5:UTF-8");
str_append(ctx->torrent, "4:infod"); /* start info dictionary */
info_start_pos = ctx->torrent->len - 1;
if(ctx->files.size == 1) {
file_n_size_info* f = (file_n_size_info*)ctx->files.array[0];
str_append(ctx->torrent, "6:length");
bt_bencode_int(ctx->torrent, f->size);
/* note: for one file f->path must be a basename */
str_append(ctx->torrent, "4:name");
bt_bencode_str(ctx->torrent, f->path);
}
str_append(ctx->torrent, "12:piece length");
bt_bencode_int(ctx->torrent, ctx->piece_length);
str_append(ctx->torrent, "6:pieces");
bt_bencode_pieces(ctx->torrent, ctx);
if(ctx->flags & BT_OPT_PRIVATE) {
str_append(ctx->torrent, "7:privatei1e");
}
str_append(ctx->torrent, "ee");
SHA1_INIT(ctx);
SHA1_UPDATE(ctx, (unsigned char*)ctx->torrent->str + info_start_pos,
ctx->torrent->len - info_start_pos - 1);
SHA1_FINAL(ctx, ctx->btih);
}
