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
25typedef 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
35struct 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 */
51void 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 */
62void 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 */
73void 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 */
82void 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 */
91void 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 */
104void 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 */
116void 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 */
128uint8_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 */
138gboolean 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 */
148void 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 */
158void buffer_move(Buffer *to, Buffer *from);
159
160#endif /* QEMU_BUFFER_H */
161