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Diffstat (limited to 'src/util/fifo_buffer.h')
-rw-r--r-- | src/util/fifo_buffer.h | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/src/util/fifo_buffer.h b/src/util/fifo_buffer.h new file mode 100644 index 000000000..ccea97d86 --- /dev/null +++ b/src/util/fifo_buffer.h @@ -0,0 +1,164 @@ +/* + * Copyright (C) 2003-2011 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; + +#ifdef __cplusplus +extern "C" { +#endif + +/** + * 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); + +void +fifo_buffer_init(struct fifo_buffer *buffer, size_t size); + +/** + * Change the capacity of the #fifo_buffer, while preserving existing + * data. + * + * @param buffer the old buffer, may be NULL + * @param new_size the requested new size of the #fifo_buffer; must + * not be smaller than the data which is stored in the old buffer + * @return the new buffer, may be NULL if the requested new size is 0 + */ +struct fifo_buffer * +fifo_buffer_realloc(struct fifo_buffer *buffer, size_t new_size); + +/** + * Frees the resources consumed by this #fifo_buffer object. + */ +void +fifo_buffer_free(struct fifo_buffer *buffer); + +/** + * Return the capacity of the buffer, i.e. the size that was passed to + * fifo_buffer_new(). + */ +size_t +fifo_buffer_capacity(const struct fifo_buffer *buffer); + +/** + * Return the number of bytes currently stored in the buffer. + */ +size_t +fifo_buffer_available(const 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); + +#ifdef __cplusplus +} +#endif + +#endif |