diff --git a/src/libguac/socket-nest.c b/src/libguac/socket-nest.c index 6acac7d9..967c9d97 100644 --- a/src/libguac/socket-nest.c +++ b/src/libguac/socket-nest.c @@ -25,80 +25,237 @@ #include #include +#include #include -#define GUAC_SOCKET_NEST_BUFFER_SIZE 8192 +/** + * The maximum number of bytes to buffer before sending a "nest" instruction. + * As some of the 8 KB space available for each instruction will be taken up by + * the "nest" opcode and other parameters, and 1 KB will be more than enough + * space for that extra data, this space is reduced to an even 7 KB. + */ +#define GUAC_SOCKET_NEST_BUFFER_SIZE 7168 -typedef struct __guac_socket_nest_data { +/** + * Internal data associated with an open socket which writes via a series of + * "nest" instructions to some underlying, parent socket. + */ +typedef struct guac_socket_nest_data { + /** + * The underlying socket which should be used to write "nest" instructions. + */ guac_socket* parent; - char buffer[GUAC_SOCKET_NEST_BUFFER_SIZE]; + + /** + * The arbitrary index of the nested socket, assigned at time of + * allocation. + */ int index; -} __guac_socket_nest_data; + /** + * The number of bytes currently in the main write buffer. + */ + int written; -ssize_t __guac_socket_nest_write_handler(guac_socket* socket, - const void* buf, size_t count) { + /** + * The main write buffer. Bytes written go here before being flushed + * as nest instructions. Space is included for the null terminator + * required by guac_protocol_send_nest(). + */ + char buffer[GUAC_SOCKET_NEST_BUFFER_SIZE]; - __guac_socket_nest_data* data = (__guac_socket_nest_data*) socket->data; - unsigned char* source = (unsigned char*) buf; + /** + * Lock which is acquired when an instruction is being written, and + * released when the instruction is finished being written. + */ + pthread_mutex_t socket_lock; - /* Current location in destination buffer during copy */ - char* current = data->buffer; + /** + * Lock which protects access to the internal buffer of this socket, + * guaranteeing atomicity of writes and flushes. + */ + pthread_mutex_t buffer_lock; - /* Number of bytes remaining in source buffer */ - int remaining = count; +} guac_socket_nest_data; - /* If we can't actually store that many bytes, reduce number of bytes - * expected to be written */ - if (remaining > GUAC_SOCKET_NEST_BUFFER_SIZE) - remaining = GUAC_SOCKET_NEST_BUFFER_SIZE; +/** + * Flushes the contents of the output buffer of the given socket immediately, + * without first locking access to the output buffer. This function must ONLY + * be called if the buffer lock has already been acquired. + * + * @param socket + * The guac_socket to flush. + * + * @return + * Zero if the flush operation was successful, non-zero otherwise. + */ +static ssize_t guac_socket_nest_flush(guac_socket* socket) { - /* Current offset within destination buffer */ - int offset; + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; - /* Number of characters before start of next character */ - int skip = 0; + /* Flush remaining bytes in buffer */ + if (data->written > 0) { - /* Copy UTF-8 characters into buffer */ - for (offset = 0; offset < GUAC_SOCKET_NEST_BUFFER_SIZE; offset++) { + /* Determine length of buffer containing complete UTF-8 characters + * (buffer may end with a partial, multi-byte character) */ + int length = 0; + while (length < data->written) + length += guac_utf8_charsize(*(data->buffer + length)); - /* Get next byte */ - unsigned char c = *source; - remaining--; + /* Add null terminator, preserving overwritten character for later + * restoration (guac_protocol_send_nest() requires null-terminated + * strings) */ + char overwritten = data->buffer[length]; + data->buffer[length] = '\0'; - /* If skipping, then skip */ - if (skip > 0) skip--; + /* Write ALL bytes in buffer as nest instruction */ + int retval = guac_protocol_send_nest(data->parent, data->index, data->buffer); - /* Otherwise, determine next skip value, and increment length */ - else { + /* Restore original value overwritten by null terminator */ + data->buffer[length] = overwritten; - /* Determine skip value (size in bytes of rest of character) */ - skip = guac_utf8_charsize(c) - 1; + if (retval) + return 1; - /* If not enough bytes to complete character, break */ - if (skip > remaining) - break; - - } - - /* Store byte */ - *current = c; - - /* Advance to next character */ - source++; - current++; + /* Shift any remaining data to beginning of buffer */ + memcpy(data->buffer, data->buffer + length, data->written - length); + data->written -= length; } - /* Append null-terminator */ - *current = 0; + return 0; - /* Send nest instruction containing read UTF-8 segment */ - guac_protocol_send_nest(data->parent, data->index, data->buffer); +} - /* Return number of bytes actually written */ - return offset; +/** + * Flushes the internal buffer of the given guac_socket, writing all data + * to the underlying socket using "nest" instructions. + * + * @param socket + * The guac_socket to flush. + * + * @return + * Zero if the flush operation was successful, non-zero otherwise. + */ +static ssize_t guac_socket_nest_flush_handler(guac_socket* socket) { + + int retval; + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; + + /* Acquire exclusive access to buffer */ + pthread_mutex_lock(&(data->buffer_lock)); + + /* Flush contents of buffer */ + retval = guac_socket_nest_flush(socket); + + /* Relinquish exclusive access to buffer */ + pthread_mutex_unlock(&(data->buffer_lock)); + + return retval; + +} + +/** + * Writes the contents of the buffer to the output buffer of the given socket, + * flushing the output buffer as necessary, without first locking access to the + * output buffer. This function must ONLY be called if the buffer lock has + * already been acquired. + * + * @param socket + * The guac_socket to write the given buffer to. + * + * @param buf + * The buffer to write to the given socket. + * + * @param count + * The number of bytes in the given buffer. + * + * @return + * The number of bytes written, or a negative value if an error occurs + * during write. + */ +static ssize_t guac_socket_nest_write_buffered(guac_socket* socket, + const void* buf, size_t count) { + + size_t original_count = count; + const char* current = buf; + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; + + /* Append to buffer, flush if necessary */ + while (count > 0) { + + int chunk_size; + + /* Calculate space remaining, including one extra byte for the null + * terminator added upon flush */ + int remaining = sizeof(data->buffer) - data->written - 1; + + /* If no space left in buffer, flush and retry */ + if (remaining == 0) { + + /* Abort if error occurs during flush */ + if (guac_socket_nest_flush(socket)) + return -1; + + /* Retry buffer append */ + continue; + + } + + /* Calculate size of chunk to be written to buffer */ + chunk_size = count; + if (chunk_size > remaining) + chunk_size = remaining; + + /* Update output buffer */ + memcpy(data->buffer + data->written, current, chunk_size); + data->written += chunk_size; + + /* Update provided buffer */ + current += chunk_size; + count -= chunk_size; + + } + + /* All bytes have been written, possibly some to the internal buffer */ + return original_count; + +} + +/** + * Appends the provided data to the internal buffer for future writing. The + * actual write attempt will occur only upon flush, or when the internal buffer + * is full. + * + * @param socket + * The guac_socket being write to. + * + * @param buf + * The arbitrary buffer containing the data to be written. + * + * @param count + * The number of bytes contained within the buffer. + * + * @return + * The number of bytes written, or -1 if an error occurs. + */ +static ssize_t guac_socket_nest_write_handler(guac_socket* socket, + const void* buf, size_t count) { + + int retval; + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; + + /* Acquire exclusive access to buffer */ + pthread_mutex_lock(&(data->buffer_lock)); + + /* Write provided data to buffer */ + retval = guac_socket_nest_write_buffered(socket, buf, count); + + /* Relinquish exclusive access to buffer */ + pthread_mutex_unlock(&(data->buffer_lock)); + + return retval; } @@ -113,29 +270,63 @@ ssize_t __guac_socket_nest_write_handler(guac_socket* socket, * Zero if the data was successfully freed, non-zero otherwise. This * implementation always succeeds, and will always return zero. */ -static int __guac_socket_nest_free_handler(guac_socket* socket) { +static int guac_socket_nest_free_handler(guac_socket* socket) { /* Free associated data */ - __guac_socket_nest_data* data = (__guac_socket_nest_data*) socket->data; + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; free(data); return 0; } +/** + * Acquires exclusive access to the given socket. + * + * @param socket + * The guac_socket to which exclusive access is required. + */ +static void guac_socket_nest_lock_handler(guac_socket* socket) { + + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; + + /* Acquire exclusive access to socket */ + pthread_mutex_lock(&(data->socket_lock)); + +} + +/** + * Relinquishes exclusive access to the given socket. + * + * @param socket + * The guac_socket to which exclusive access is no longer required. + */ +static void guac_socket_nest_unlock_handler(guac_socket* socket) { + + guac_socket_nest_data* data = (guac_socket_nest_data*) socket->data; + + /* Relinquish exclusive access to socket */ + pthread_mutex_unlock(&(data->socket_lock)); + +} + guac_socket* guac_socket_nest(guac_socket* parent, int index) { /* Allocate socket and associated data */ guac_socket* socket = guac_socket_alloc(); - __guac_socket_nest_data* data = malloc(sizeof(__guac_socket_nest_data)); + guac_socket_nest_data* data = malloc(sizeof(guac_socket_nest_data)); - /* Store file descriptor as socket data */ + /* Store nested socket details as socket data */ data->parent = parent; + data->index = index; socket->data = data; - /* Set write and free handlers */ - socket->write_handler = __guac_socket_nest_write_handler; - socket->free_handler = __guac_socket_nest_free_handler; + /* Set relevant handlers */ + socket->write_handler = guac_socket_nest_write_handler; + socket->lock_handler = guac_socket_nest_lock_handler; + socket->unlock_handler = guac_socket_nest_unlock_handler; + socket->flush_handler = guac_socket_nest_flush_handler; + socket->free_handler = guac_socket_nest_free_handler; return socket;