/* * Copyright (C) 2003-2010 The Music Player Daemon Project * http://www.musicpd.org * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the * distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ /** \file * * This is a general purpose FIFO buffer library. You may append data * at the end, while another instance reads data from the beginning. * It is optimized for zero-copy usage: you get pointers to the real * buffer, where you may operate on. * * This library is not thread safe. */ #ifndef MPD_FIFO_BUFFER_H #define MPD_FIFO_BUFFER_H #include <stdbool.h> #include <stddef.h> struct fifo_buffer; /** * Creates a new #fifo_buffer object. Free this object with * fifo_buffer_free(). * * @param size the size of the buffer in bytes * @return the new #fifo_buffer object */ struct fifo_buffer * fifo_buffer_new(size_t size); /** * Frees the resources consumed by this #fifo_buffer object. */ void fifo_buffer_free(struct fifo_buffer *buffer); /** * Clears all data currently in this #fifo_buffer object. This does * not overwrite the actuall buffer; it just resets the internal * pointers. */ void fifo_buffer_clear(struct fifo_buffer *buffer); /** * Reads from the beginning of the buffer. To remove consumed data * from the buffer, call fifo_buffer_consume(). * * @param buffer the #fifo_buffer object * @param length_r the maximum amount to read is returned here * @return a pointer to the beginning of the buffer, or NULL if the * buffer is empty */ const void * fifo_buffer_read(const struct fifo_buffer *buffer, size_t *length_r); /** * Marks data at the beginning of the buffer as "consumed". * * @param buffer the #fifo_buffer object * @param length the number of bytes which were consumed */ void fifo_buffer_consume(struct fifo_buffer *buffer, size_t length); /** * Prepares writing to the buffer. This returns a buffer which you * can write to. To commit the write operation, call * fifo_buffer_append(). * * @param buffer the #fifo_buffer object * @param max_length_r the maximum amount to write is returned here * @return a pointer to the end of the buffer, or NULL if the buffer * is already full */ void * fifo_buffer_write(struct fifo_buffer *buffer, size_t *max_length_r); /** * Commits the write operation initiated by fifo_buffer_write(). * * @param buffer the #fifo_buffer object * @param length the number of bytes which were written */ void fifo_buffer_append(struct fifo_buffer *buffer, size_t length); /** * Checks if the buffer is empty. */ bool fifo_buffer_is_empty(struct fifo_buffer *buffer); /** * Checks if the buffer is full. */ bool fifo_buffer_is_full(struct fifo_buffer *buffer); #endif