include/qemu/buffer.h

   1 /*
   2  * QEMU generic buffers
   3  *
   4  * Copyright (c) 2015 Red Hat, Inc.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #ifndef QEMU_BUFFER_H__
  22 #define QEMU_BUFFER_H__
  23
  24 #include "qemu-common.h"
  25
  26 typedef struct Buffer Buffer;
  27
  28 /**
  29  * Buffer:
  30  *
  31  * The Buffer object provides a simple dynamically resizing
  32  * array, with separate tracking of capacity and usage. This
  33  * is typically useful when buffering I/O or processing data.
  34  */
  35
  36 struct Buffer {
  37     size_t capacity;
  38     size_t offset;
  39     uint8_t *buffer;
  40 };
  41
  42 /**
  43  * buffer_reserve:
  44  * @buffer: the buffer object
  45  * @len: the minimum required free space
  46  *
  47  * Ensure that the buffer has space allocated for at least
  48  * @len bytes. If the current buffer is too small, it will
  49  * be reallocated, possibly to a larger size than requested.
  50  */
  51 void buffer_reserve(Buffer *buffer, size_t len);
  52
  53 /**
  54  * buffer_reset:
  55  * @buffer: the buffer object
  56  *
  57  * Reset the length of the stored data to zero, but do
  58  * not free / reallocate the memory buffer
  59  */
  60 void buffer_reset(Buffer *buffer);
  61
  62 /**
  63  * buffer_free:
  64  * @buffer: the buffer object
  65  *
  66  * Reset the length of the stored data to zero and also
  67  * free the internal memory buffer
  68  */
  69 void buffer_free(Buffer *buffer);
  70
  71 /**
  72  * buffer_append:
  73  * @buffer: the buffer object
  74  * @data: the data block to append
  75  * @len: the length of @data in bytes
  76  *
  77  * Append the contents of @data to the end of the buffer.
  78  * The caller must ensure that the buffer has sufficient
  79  * free space for @len bytes, typically by calling the
  80  * buffer_reserve() method prior to appending.
  81  */
  82 void buffer_append(Buffer *buffer, const void *data, size_t len);
  83
  84 /**
  85  * buffer_advance:
  86  * @buffer: the buffer object
  87  * @len: the number of bytes to skip
  88  *
  89  * Remove @len bytes of data from the head of the buffer.
  90  * The internal buffer will not be reallocated, so will
  91  * have at least @len bytes of free space after this
  92  * call completes
  93  */
  94 void buffer_advance(Buffer *buffer, size_t len);
  95
  96 /**
  97  * buffer_end:
  98  * @buffer: the buffer object
  99  *
 100  * Get a pointer to the tail end of the internal buffer
 101  * The returned pointer is only valid until the next
 102  * call to buffer_reserve().
 103  *
 104  * Returns: the tail of the buffer
 105  */
 106 uint8_t *buffer_end(Buffer *buffer);
 107
 108 /**
 109  * buffer_empty:
 110  * @buffer: the buffer object
 111  *
 112  * Determine if the buffer contains any current data
 113  *
 114  * Returns: true if the buffer holds data, false otherwise
 115  */
 116 gboolean buffer_empty(Buffer *buffer);
 117
 118 #endif /* QEMU_BUFFER_H__ */