piececache.c

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	}

	if (piece == BITTORRENT_PIECE_UNDEF)
		return NULL;

	request = add_piece_to_bittorrent_free_list(cache, bittorrent, piece);

	/* Check for end game once again to update it sooner than later. */
	if (cache->remaining_pieces == 0
	    && list_empty(cache->free_list))
		bittorrent->mode = BITTORRENT_MODE_END_GAME;

	return request;
}

/* Find all dublicate request and clear the cloned flag if only one is found. */
static void
clear_cloned_bittorrent_peer_request(struct bittorrent_connection *bittorrent,
				     struct bittorrent_peer_request *request)
{
	struct bittorrent_peer_request *single_clone = NULL;
	struct bittorrent_peer_connection *peer;

	foreach (peer, bittorrent->peers) {
		struct bittorrent_peer_request *clone;

		clone = find_local_bittorrent_peer_request(peer, request);
		if (!clone) continue;

		/* More than one has the request pending so no cloned flags
		 * needs to be cleared. */
		if (single_clone)
			return;

		single_clone = clone;
	}

	if (single_clone)
		single_clone->cloned = 0;
}

static void
add_request_to_bittorrent_piece_cache(struct bittorrent_connection *bittorrent,
				      struct bittorrent_peer_request *request)
{
	del_from_list(request);
	if (!request->cloned) {
		/* fixme: ensure that the free list is sorted by piece the
		 * number of remaining request so that downloading of complete
		 * pieces are prioritized. */
		request->requested = 0;
		add_to_list(bittorrent->cache->free_list, request);
		return;
	}

	clear_cloned_bittorrent_peer_request(bittorrent, request);
	mem_free(request);
}

void
add_requests_to_bittorrent_piece_cache(struct bittorrent_peer_connection *peer,
				       struct bittorrent_peer_status *status)
{
	struct bittorrent_peer_request *request, *next;

	foreachsafe (request, next, status->requests) {
		add_request_to_bittorrent_piece_cache(peer->bittorrent, request);
	}
}


/* ************************************************************************** */
/* Piece cache rarity index management: */
/* ************************************************************************** */

void
update_bittorrent_piece_cache(struct bittorrent_peer_connection *peer,
			      uint32_t piece)
{
	struct bittorrent_piece_cache *cache = peer->bittorrent->cache;

	assert(piece <= peer->bittorrent->meta.pieces);

	if (!cache->entries[piece].completed
	    && !cache->entries[piece].rarity)
		cache->unavailable_pieces--;

	cache->entries[piece].rarity++;
	assertm(cache->entries[piece].rarity <= list_size(&peer->bittorrent->peers),
		"Piece rarity overflow");
}

void
update_bittorrent_piece_cache_from_bitfield(struct bittorrent_peer_connection *peer)
{
	uint32_t piece;

	assert(peer->bitfield->bitsize == peer->bittorrent->meta.pieces);

	foreach_bitfield_set (piece, peer->bitfield) {
		update_bittorrent_piece_cache(peer, piece);
	}
}

void
remove_bittorrent_peer_from_piece_cache(struct bittorrent_peer_connection *peer)
{
	struct bittorrent_piece_cache *cache = peer->bittorrent->cache;
	unsigned int piece;

	assert(peer->bitfield);

	foreach_bitfield_set (piece, peer->bitfield) {
		cache->entries[piece].rarity--;
		assertm(cache->entries[piece].rarity <= list_size(&peer->bittorrent->peers),
			"Piece rarity underflow");

		if (!cache->entries[piece].completed
		    && !cache->entries[piece].rarity)
			cache->unavailable_pieces++;
	}
}


/* ************************************************************************** */
/* Piece cache disk management: */
/* ************************************************************************** */

/* Recursively create directories in a path. The last element in the path is
 * taken to be a filename, and simply ignored */
static enum bittorrent_state
create_bittorrent_path(unsigned char *path)
{
	int pos;

	if (!*path) return BITTORRENT_STATE_ERROR;

	for (pos = 1; path[pos]; pos++) {
		unsigned char separator = path[pos];
		int ret;

		if (!dir_sep(separator))
			continue;

		path[pos] = 0;

		ret = mkdir(path, S_IREAD | S_IWRITE | S_IEXEC);

		path[pos] = separator;

		if (ret < 0 && errno != EEXIST)
			return BITTORRENT_STATE_ERROR;
	}

	return BITTORRENT_STATE_OK;
}

/* Complementary to the above rmdir()s each directory in the path. */
static void
remove_bittorrent_path(struct bittorrent_meta *meta, unsigned char *path)
{
	unsigned char *root = strstr(path, meta->name);
	int pos;

	assert(meta->type == BITTORRENT_MULTI_FILE);

	if (!root || root == path)
		return;

	for (pos = strlen(root); pos >= 0; pos--) {
		unsigned char separator = root[pos];
		int ret;

		if (!dir_sep(separator))
			continue;

		root[pos] = 0;

		ret = rmdir(path);

		path[pos] = separator;

		if (ret < 0) return;
	}
}

static unsigned char *
get_bittorrent_file_name(struct bittorrent_meta *meta, struct bittorrent_file *file)
{
	unsigned char *name;

	name = expand_tilde(get_opt_str("document.download.directory"));
	if (!name) return NULL;

	add_to_strn(&name, "/");
	add_to_strn(&name, meta->name);

	if (meta->type == BITTORRENT_MULTI_FILE) {
		add_to_strn(&name, "/");
		add_to_strn(&name, file->name);
	}

	return name;
}

enum bittorrent_translation {
	BITTORRENT_READ,
	BITTORRENT_WRITE,
	BITTORRENT_SEEK,
};

static int
open_bittorrent_file(struct bittorrent_meta *meta, struct bittorrent_file *file,
		     enum bittorrent_translation trans, off_t offset)
{
	unsigned char *name = get_bittorrent_file_name(meta, file);
	off_t seek_result;
	int fd;
	int flags = (trans == BITTORRENT_WRITE ? O_WRONLY : O_RDONLY);

	assert(trans != BITTORRENT_SEEK);

	if (!name) return -1;

	fd = open(name, flags, S_IRUSR | S_IWUSR);
	if (fd == -1) {
		/* 99% of the time the file will already exist so special case
		 * the directory and file creation. */
		if (errno == ENOENT
		    && trans == BITTORRENT_WRITE
		    && create_bittorrent_path(name) == BITTORRENT_STATE_OK)
			fd = open(name, flags | O_CREAT, S_IRUSR | S_IWUSR);
	}

	mem_free(name);

	if (fd == -1) return -1;

	if (trans == BITTORRENT_READ) {
		struct stat stat;

		if (fstat(fd, &stat) < -1 || stat.st_size < offset) {
			close(fd);
			return -1;
		}
	}

	seek_result = lseek(fd, offset, SEEK_SET);
	if (seek_result == (off_t) -1 || seek_result != offset) {
		close(fd);
		return -1;
	}

	return fd;
}

static enum bittorrent_state
bittorrent_file_piece_translation(struct bittorrent_meta *meta,
				  struct bittorrent_piece_cache *cache,
				  struct bittorrent_piece_cache_entry *entry,
				  uint32_t piece,
				  enum bittorrent_translation trans)
{
	struct bittorrent_file *file;
	uint32_t piece_length = get_bittorrent_piece_length(meta, piece);
	uint32_t piece_offset = 0;
	off_t torrent_offset = (off_t) meta->piece_length * piece;
	off_t current_offset = 0;
	enum bittorrent_state state = BITTORRENT_STATE_OK;
	int prev_selected = -1;

	if (trans == BITTORRENT_READ) {
		assert(!entry->data);

		entry->data = mem_mmap_alloc(piece_length);
		if (!entry->data)
			return BITTORRENT_STATE_OUT_OF_MEM;
	}

	foreach (file, meta->files) {
		unsigned char *data;
		off_t file_offset, file_length;
		uint32_t data_length;
		ssize_t length;
		int fd;

		if (piece_offset >= piece_length)
			break;

		if (current_offset + file->length < torrent_offset) {
			current_offset += file->length;
			continue;
		}

		assert(current_offset <= torrent_offset + piece_length);

		/* Figure out where in the file we need access. */
		file_offset = torrent_offset - current_offset;
		if (file_offset < 0)
			file_offset = 0;

		assertm(file_offset <= file->length, "%ld %ld", file_offset, file->length);

		/* How much needs to be read or written. */
		data_length = piece_length - piece_offset;
		file_length = file->length - file_offset;
		if (data_length > file_length)
			data_length = file_length;

		if (trans == BITTORRENT_SEEK) {
			/* Mark all pieces which need to be downloaded. */
			if (!entry->selected)
				entry->selected = (file->selected == 1);

			/* Lock entries that span both selected and unselected
			 * files in memory. */
			if (prev_selected != -1
			    && prev_selected != file->selected)
				entry->locked = 1;

			prev_selected = file->selected;

			/* Prepare the next iteration. */
			piece_offset   += data_length;
			current_offset += file->length;
			continue;
		}

		/* Jump on unselected files. */
		if (!file->selected) {
			if (trans != BITTORRENT_READ
			    || !entry->completed) {
				/* Prepare the next iteration. */
				piece_offset   += data_length;
				current_offset += file->length;
				continue;
			}

			/* Allow reading of pieces which is resumable. */
			assert(entry->completed && trans == BITTORRENT_READ);
		}

		/* Open at the desired offset and possibly create the file and
		 * parent directories. */
		fd = open_bittorrent_file(meta, file, trans, file_offset);
		if (fd == -1) {
			/* Try to gracefully handle bogus paths; empty file
			 * names and directory names. */
			if (!file->name[0]
			    || dir_sep(file->name[strlen(file->name) - 1])) {
				current_offset += file->length;
				continue;
			}

			if (trans == BITTORRENT_WRITE) {
				state = BITTORRENT_STATE_ERROR;
				break;
			}

			state = BITTORRENT_STATE_FILE_MISSING;
			break;
		}

		assert(entry->data);

		data = &entry->data[piece_offset];

		/* Do it! ;-) */
		if (trans == BITTORRENT_READ) {
			length = safe_read(fd, data, data_length);
		} else {
			length = safe_write(fd, data, data_length);
		}

		/* Cleanup. */
		close(fd);

		/* Check if the operation failed. */
		if (length != data_length)
			return BITTORRENT_STATE_ERROR;

		/* Prepare the next iteration. */
		piece_offset   += data_length;
		current_offset += file->length;
	}

	if (state != BITTORRENT_STATE_OK || piece_offset != piece_length) {
		if (piece_offset != piece_length)
			state = BITTORRENT_STATE_ERROR;

		assert(trans != BITTORRENT_SEEK);

		mem_mmap_free(entry->data, piece_length);
		entry->data = NULL;

		return state;
	}

	if (trans != BITTORRENT_SEEK) {
		/* Whether we just read or wrote the piece, it is now
		 * disposable. */
		add_to_list(cache->queue, entry);
	}

	return BITTORRENT_STATE_OK;
}


/* ************************************************************************** */
/* Piece cache block data management: */
/* ************************************************************************** */

static void
cancel_cloned_bittorrent_peer_requests(struct bittorrent_connection *bittorrent,
				       struct bittorrent_peer_request *request)
{
	struct bittorrent_peer_connection *peer;

	foreach (peer, bittorrent->peers) {
		struct bittorrent_peer_request *clone;

		clone = find_local_bittorrent_peer_request(peer, request);
		if (!clone)
			continue;

		/* Only cancel it if it was actually requested. */
		if (clone->requested)
			cancel_bittorrent_peer_request(peer, clone);

		del_from_list(clone);
		mem_free(clone);
	}
}

enum bittorrent_state
add_to_bittorrent_piece_cache(struct bittorrent_peer_connection *peer,
			      uint32_t piece, uint32_t offset,
			      unsigned char *data, uint32_t datalen,
			      int *write_errno)
{
	struct bittorrent_connection *bittorrent = peer->bittorrent;
	struct bittorrent_meta *meta = &bittorrent->meta;
	struct bittorrent_piece_cache *cache = bittorrent->cache;
	struct bittorrent_piece_cache_entry *entry;
	struct bittorrent_peer_request *request;
	enum bittorrent_state state;
	uint32_t piece_length;

	assert(piece < bittorrent->meta.pieces);
	assert(offset + datalen <= get_bittorrent_piece_length(meta, piece));
	assert(datalen);

	entry = &cache->entries[piece];