src/fifo_buffer.h

   1 /*
   2  * Copyright (C) 2003-2010 The Music Player Daemon Project
   3  * http://www.musicpd.org
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * - Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *
  12  * - Redistributions in binary form must reproduce the above copyright
  13  * notice, this list of conditions and the following disclaimer in the
  14  * documentation and/or other materials provided with the
  15  * distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  21  * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  26  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  28  * OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 /** \file
  32  *
  33  * This is a general purpose FIFO buffer library.  You may append data
  34  * at the end, while another instance reads data from the beginning.
  35  * It is optimized for zero-copy usage: you get pointers to the real
  36  * buffer, where you may operate on.
  37  *
  38  * This library is not thread safe.
  39  */
  40
  41 #ifndef MPD_FIFO_BUFFER_H
  42 #define MPD_FIFO_BUFFER_H
  43
  44 #include <stdbool.h>
  45 #include <stddef.h>
  46
  47 struct fifo_buffer;
  48
  49 /**
  50  * Creates a new #fifo_buffer object.  Free this object with
  51  * fifo_buffer_free().
  52  *
  53  * @param size the size of the buffer in bytes
  54  * @return the new #fifo_buffer object
  55  */
  56 struct fifo_buffer *
  57 fifo_buffer_new(size_t size);
  58
  59 /**
  60  * Frees the resources consumed by this #fifo_buffer object.
  61  */
  62 void
  63 fifo_buffer_free(struct fifo_buffer *buffer);
  64
  65 /**
  66  * Clears all data currently in this #fifo_buffer object.  This does
  67  * not overwrite the actuall buffer; it just resets the internal
  68  * pointers.
  69  */
  70 void
  71 fifo_buffer_clear(struct fifo_buffer *buffer);
  72
  73 /**
  74  * Reads from the beginning of the buffer.  To remove consumed data
  75  * from the buffer, call fifo_buffer_consume().
  76  *
  77  * @param buffer the #fifo_buffer object
  78  * @param length_r the maximum amount to read is returned here
  79  * @return a pointer to the beginning of the buffer, or NULL if the
  80  * buffer is empty
  81  */
  82 const void *
  83 fifo_buffer_read(const struct fifo_buffer *buffer, size_t *length_r);
  84
  85 /**
  86  * Marks data at the beginning of the buffer as "consumed".
  87  *
  88  * @param buffer the #fifo_buffer object
  89  * @param length the number of bytes which were consumed
  90  */
  91 void
  92 fifo_buffer_consume(struct fifo_buffer *buffer, size_t length);
  93
  94 /**
  95  * Prepares writing to the buffer.  This returns a buffer which you
  96  * can write to.  To commit the write operation, call
  97  * fifo_buffer_append().
  98  *
  99  * @param buffer the #fifo_buffer object
 100  * @param max_length_r the maximum amount to write is returned here
 101  * @return a pointer to the end of the buffer, or NULL if the buffer
 102  * is already full
 103  */
 104 void *
 105 fifo_buffer_write(struct fifo_buffer *buffer, size_t *max_length_r);
 106
 107 /**
 108  * Commits the write operation initiated by fifo_buffer_write().
 109  *
 110  * @param buffer the #fifo_buffer object
 111  * @param length the number of bytes which were written
 112  */
 113 void
 114 fifo_buffer_append(struct fifo_buffer *buffer, size_t length);
 115
 116 /**
 117  * Checks if the buffer is empty.
 118  */
 119 bool
 120 fifo_buffer_is_empty(struct fifo_buffer *buffer);
 121
 122 /**
 123  * Checks if the buffer is full.
 124  */
 125 bool
 126 fifo_buffer_is_full(struct fifo_buffer *buffer);
 127
 128 #endif