154 lines
4.5 KiB
C
154 lines
4.5 KiB
C
/*
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* Copyright (C) 2003-2011 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/** \file
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*
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* This is a general purpose FIFO buffer library. You may append data
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* at the end, while another instance reads data from the beginning.
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* It is optimized for zero-copy usage: you get pointers to the real
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* buffer, where you may operate on.
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*
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* This library is not thread safe.
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*/
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#ifndef MPD_FIFO_BUFFER_H
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#define MPD_FIFO_BUFFER_H
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#include <stdbool.h>
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#include <stddef.h>
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struct fifo_buffer;
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/**
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* Creates a new #fifo_buffer object. Free this object with
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* fifo_buffer_free().
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*
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* @param size the size of the buffer in bytes
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* @return the new #fifo_buffer object
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*/
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struct fifo_buffer *
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fifo_buffer_new(size_t size);
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/**
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* Change the capacity of the #fifo_buffer, while preserving existing
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* data.
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*
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* @param buffer the old buffer, may be NULL
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* @param new_size the requested new size of the #fifo_buffer; must
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* not be smaller than the data which is stored in the old buffer
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* @return the new buffer, may be NULL if the requested new size is 0
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*/
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struct fifo_buffer *
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fifo_buffer_realloc(struct fifo_buffer *buffer, size_t new_size);
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/**
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* Frees the resources consumed by this #fifo_buffer object.
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*/
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void
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fifo_buffer_free(struct fifo_buffer *buffer);
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/**
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* Return the capacity of the buffer, i.e. the size that was passed to
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* fifo_buffer_new().
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*/
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size_t
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fifo_buffer_capacity(const struct fifo_buffer *buffer);
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/**
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* Return the number of bytes currently stored in the buffer.
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*/
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size_t
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fifo_buffer_available(const struct fifo_buffer *buffer);
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/**
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* Clears all data currently in this #fifo_buffer object. This does
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* not overwrite the actuall buffer; it just resets the internal
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* pointers.
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*/
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void
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fifo_buffer_clear(struct fifo_buffer *buffer);
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/**
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* Reads from the beginning of the buffer. To remove consumed data
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* from the buffer, call fifo_buffer_consume().
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*
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* @param buffer the #fifo_buffer object
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* @param length_r the maximum amount to read is returned here
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* @return a pointer to the beginning of the buffer, or NULL if the
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* buffer is empty
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*/
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const void *
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fifo_buffer_read(const struct fifo_buffer *buffer, size_t *length_r);
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/**
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* Marks data at the beginning of the buffer as "consumed".
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*
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* @param buffer the #fifo_buffer object
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* @param length the number of bytes which were consumed
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*/
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void
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fifo_buffer_consume(struct fifo_buffer *buffer, size_t length);
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/**
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* Prepares writing to the buffer. This returns a buffer which you
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* can write to. To commit the write operation, call
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* fifo_buffer_append().
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*
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* @param buffer the #fifo_buffer object
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* @param max_length_r the maximum amount to write is returned here
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* @return a pointer to the end of the buffer, or NULL if the buffer
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* is already full
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*/
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void *
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fifo_buffer_write(struct fifo_buffer *buffer, size_t *max_length_r);
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/**
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* Commits the write operation initiated by fifo_buffer_write().
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*
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* @param buffer the #fifo_buffer object
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* @param length the number of bytes which were written
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*/
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void
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fifo_buffer_append(struct fifo_buffer *buffer, size_t length);
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/**
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* Checks if the buffer is empty.
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*/
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bool
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fifo_buffer_is_empty(struct fifo_buffer *buffer);
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/**
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* Checks if the buffer is full.
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*/
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bool
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fifo_buffer_is_full(struct fifo_buffer *buffer);
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#endif
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