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 2.1 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
  25 typedef struct Buffer Buffer;
  26
  27 /**
  28  * Buffer:
  29  *
  30  * The Buffer object provides a simple dynamically resizing
  31  * array, with separate tracking of capacity and usage. This
  32  * is typically useful when buffering I/O or processing data.
  33  */
  34
  35 struct Buffer {
  36     char *name;
  37     size_t capacity;
  38     size_t offset;
  39     uint64_t avg_size;
  40     uint8_t *buffer;
  41 };
  42
  43 /**
  44  * buffer_init:
  45  * @buffer: the buffer object
  46  * @name: buffer name
  47  *
  48  * Optionally attach a name to the buffer, to make it easier
  49  * to identify in debug traces.
  50  */
  51 void buffer_init(Buffer *buffer, const char *name, ...)
  52         GCC_FMT_ATTR(2, 3);
  53
  54 /**
  55  * buffer_shrink:
  56  * @buffer: the buffer object
  57  *
  58  * Try to shrink the buffer.  Checks current buffer capacity and size
  59  * and reduces capacity in case only a fraction of the buffer is
  60  * actually used.
  61  */
  62 void buffer_shrink(Buffer *buffer);
  63
  64 /**
  65  * buffer_reserve:
  66  * @buffer: the buffer object
  67  * @len: the minimum required free space
  68  *
  69  * Ensure that the buffer has space allocated for at least
  70  * @len bytes. If the current buffer is too small, it will
  71  * be reallocated, possibly to a larger size than requested.
  72  */
  73 void buffer_reserve(Buffer *buffer, size_t len);
  74
  75 /**
  76  * buffer_reset:
  77  * @buffer: the buffer object
  78  *
  79  * Reset the length of the stored data to zero, but do
  80  * not free / reallocate the memory buffer
  81  */
  82 void buffer_reset(Buffer *buffer);
  83
  84 /**
  85  * buffer_free:
  86  * @buffer: the buffer object
  87  *
  88  * Reset the length of the stored data to zero and also
  89  * free the internal memory buffer
  90  */
  91 void buffer_free(Buffer *buffer);
  92
  93 /**
  94  * buffer_append:
  95  * @buffer: the buffer object
  96  * @data: the data block to append
  97  * @len: the length of @data in bytes
  98  *
  99  * Append the contents of @data to the end of the buffer.
 100  * The caller must ensure that the buffer has sufficient
 101  * free space for @len bytes, typically by calling the
 102  * buffer_reserve() method prior to appending.
 103  */
 104 void buffer_append(Buffer *buffer, const void *data, size_t len);
 105
 106 /**
 107  * buffer_advance:
 108  * @buffer: the buffer object
 109  * @len: the number of bytes to skip
 110  *
 111  * Remove @len bytes of data from the head of the buffer.
 112  * The internal buffer will not be reallocated, so will
 113  * have at least @len bytes of free space after this
 114  * call completes
 115  */
 116 void buffer_advance(Buffer *buffer, size_t len);
 117
 118 /**
 119  * buffer_end:
 120  * @buffer: the buffer object
 121  *
 122  * Get a pointer to the tail end of the internal buffer
 123  * The returned pointer is only valid until the next
 124  * call to buffer_reserve().
 125  *
 126  * Returns: the tail of the buffer
 127  */
 128 uint8_t *buffer_end(Buffer *buffer);
 129
 130 /**
 131  * buffer_empty:
 132  * @buffer: the buffer object
 133  *
 134  * Determine if the buffer contains any current data
 135  *
 136  * Returns: true if the buffer holds data, false otherwise
 137  */
 138 gboolean buffer_empty(Buffer *buffer);
 139
 140 /**
 141  * buffer_move_empty:
 142  * @to: destination buffer object
 143  * @from: source buffer object
 144  *
 145  * Moves buffer, without copying data.  'to' buffer must be empty.
 146  * 'from' buffer is empty and zero-sized on return.
 147  */
 148 void buffer_move_empty(Buffer *to, Buffer *from);
 149
 150 /**
 151  * buffer_move:
 152  * @to: destination buffer object
 153  * @from: source buffer object
 154  *
 155  * Moves buffer, copying data (unless 'to' buffer happens to be empty).
 156  * 'from' buffer is empty and zero-sized on return.
 157  */
 158 void buffer_move(Buffer *to, Buffer *from);
 159
 160 #endif /* QEMU_BUFFER_H */