diff options
Diffstat (limited to '')
| -rw-r--r-- | src/fifo_buffer.c | 160 | ||||
| -rw-r--r-- | src/fifo_buffer.h | 128 |
2 files changed, 288 insertions, 0 deletions
diff --git a/src/fifo_buffer.c b/src/fifo_buffer.c new file mode 100644 index 000000000..adee438c0 --- /dev/null +++ b/src/fifo_buffer.c @@ -0,0 +1,160 @@ +/* + * Copyright (C) 2003-2009 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. + */ + +#include "fifo_buffer.h" + +#include <glib.h> + +#include <assert.h> +#include <string.h> + +struct fifo_buffer { + size_t size, start, end; + unsigned char buffer[sizeof(size_t)]; +}; + +struct fifo_buffer * +fifo_buffer_new(size_t size) +{ + struct fifo_buffer *buffer; + + assert(size > 0); + + buffer = (struct fifo_buffer *)g_malloc(sizeof(*buffer) - + sizeof(buffer->buffer) + size); + + buffer->size = size; + buffer->start = 0; + buffer->end = 0; + + return buffer; +} + +void +fifo_buffer_free(struct fifo_buffer *buffer) +{ + assert(buffer != NULL); + + g_free(buffer); +} + +void +fifo_buffer_clear(struct fifo_buffer *buffer) +{ + assert(buffer != NULL); + + buffer->start = 0; + buffer->end = 0; +} + +const void * +fifo_buffer_read(const struct fifo_buffer *buffer, size_t *length_r) +{ + assert(buffer != NULL); + assert(buffer->end >= buffer->start); + assert(length_r != NULL); + + if (buffer->start == buffer->end) + /* the buffer is empty */ + return NULL; + + *length_r = buffer->end - buffer->start; + return buffer->buffer + buffer->start; +} + +void +fifo_buffer_consume(struct fifo_buffer *buffer, size_t length) +{ + assert(buffer != NULL); + assert(buffer->end >= buffer->start); + assert(buffer->start + length <= buffer->end); + + buffer->start += length; +} + +/** + * Move data to the beginning of the buffer, to make room at the end. + */ +static void +fifo_buffer_move(struct fifo_buffer *buffer) +{ + if (buffer->start == 0) + return; + + if (buffer->end > buffer->start) + memmove(buffer->buffer, + buffer->buffer + buffer->start, + buffer->end - buffer->start); + + buffer->end -= buffer->start; + buffer->start = 0; +} + +void * +fifo_buffer_write(struct fifo_buffer *buffer, size_t *max_length_r) +{ + assert(buffer != NULL); + assert(buffer->end <= buffer->size); + assert(max_length_r != NULL); + + if (buffer->end == buffer->size) { + fifo_buffer_move(buffer); + if (buffer->end == buffer->size) + return NULL; + } else if (buffer->start > 0 && buffer->start == buffer->end) { + buffer->start = 0; + buffer->end = 0; + } + + *max_length_r = buffer->size - buffer->end; + return buffer->buffer + buffer->end; +} + +void +fifo_buffer_append(struct fifo_buffer *buffer, size_t length) +{ + assert(buffer != NULL); + assert(buffer->end >= buffer->start); + assert(buffer->end + length <= buffer->size); + + buffer->end += length; +} + +bool +fifo_buffer_is_empty(struct fifo_buffer *buffer) +{ + return buffer->start == buffer->end; +} + +bool +fifo_buffer_is_full(struct fifo_buffer *buffer) +{ + return buffer->start == 0 && buffer->end == buffer->size; +} diff --git a/src/fifo_buffer.h b/src/fifo_buffer.h new file mode 100644 index 000000000..4af6bde3b --- /dev/null +++ b/src/fifo_buffer.h @@ -0,0 +1,128 @@ +/* + * Copyright (C) 2003-2009 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 |