dump: allow target to set the physical base
[qemu/ar7.git] / util / buffer.c
blob8b27c08aaca25c3523ca7671144ffe1d64b4d5ce
1 /*
2 * QEMU generic buffers
4 * Copyright (c) 2015 Red Hat, Inc.
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.
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.
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/>.
21 #include "qemu/buffer.h"
22 #include "trace.h"
24 #define BUFFER_MIN_INIT_SIZE 4096
25 #define BUFFER_MIN_SHRINK_SIZE 65536
27 /* define the factor alpha for the expentional smoothing
28 * that is used in the average size calculation. a shift
29 * of 7 results in an alpha of 1/2^7. */
30 #define BUFFER_AVG_SIZE_SHIFT 7
32 static size_t buffer_req_size(Buffer *buffer, size_t len)
34 return MAX(BUFFER_MIN_INIT_SIZE,
35 pow2ceil(buffer->offset + len));
38 static void buffer_adj_size(Buffer *buffer, size_t len)
40 size_t old = buffer->capacity;
41 buffer->capacity = buffer_req_size(buffer, len);
42 buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
43 trace_buffer_resize(buffer->name ?: "unnamed",
44 old, buffer->capacity);
46 /* make it even harder for the buffer to shrink, reset average size
47 * to currenty capacity if it is larger than the average. */
48 buffer->avg_size = MAX(buffer->avg_size,
49 buffer->capacity << BUFFER_AVG_SIZE_SHIFT);
52 void buffer_init(Buffer *buffer, const char *name, ...)
54 va_list ap;
56 va_start(ap, name);
57 buffer->name = g_strdup_vprintf(name, ap);
58 va_end(ap);
61 static uint64_t buffer_get_avg_size(Buffer *buffer)
63 return buffer->avg_size >> BUFFER_AVG_SIZE_SHIFT;
66 void buffer_shrink(Buffer *buffer)
68 size_t new;
70 /* Calculate the average size of the buffer as
71 * avg_size = avg_size * ( 1 - a ) + required_size * a
72 * where a is 1 / 2 ^ BUFFER_AVG_SIZE_SHIFT. */
73 buffer->avg_size *= (1 << BUFFER_AVG_SIZE_SHIFT) - 1;
74 buffer->avg_size >>= BUFFER_AVG_SIZE_SHIFT;
75 buffer->avg_size += buffer_req_size(buffer, 0);
77 /* And then only shrink if the average size of the buffer is much
78 * too big, to avoid bumping up & down the buffers all the time.
79 * realloc() isn't exactly cheap ... */
80 new = buffer_req_size(buffer, buffer_get_avg_size(buffer));
81 if (new < buffer->capacity >> 3 &&
82 new >= BUFFER_MIN_SHRINK_SIZE) {
83 buffer_adj_size(buffer, buffer_get_avg_size(buffer));
86 buffer_adj_size(buffer, 0);
89 void buffer_reserve(Buffer *buffer, size_t len)
91 if ((buffer->capacity - buffer->offset) < len) {
92 buffer_adj_size(buffer, len);
96 gboolean buffer_empty(Buffer *buffer)
98 return buffer->offset == 0;
101 uint8_t *buffer_end(Buffer *buffer)
103 return buffer->buffer + buffer->offset;
106 void buffer_reset(Buffer *buffer)
108 buffer->offset = 0;
109 buffer_shrink(buffer);
112 void buffer_free(Buffer *buffer)
114 trace_buffer_free(buffer->name ?: "unnamed", buffer->capacity);
115 g_free(buffer->buffer);
116 g_free(buffer->name);
117 buffer->offset = 0;
118 buffer->capacity = 0;
119 buffer->buffer = NULL;
120 buffer->name = NULL;
123 void buffer_append(Buffer *buffer, const void *data, size_t len)
125 memcpy(buffer->buffer + buffer->offset, data, len);
126 buffer->offset += len;
129 void buffer_advance(Buffer *buffer, size_t len)
131 memmove(buffer->buffer, buffer->buffer + len,
132 (buffer->offset - len));
133 buffer->offset -= len;
134 buffer_shrink(buffer);
137 void buffer_move_empty(Buffer *to, Buffer *from)
139 trace_buffer_move_empty(to->name ?: "unnamed",
140 from->offset,
141 from->name ?: "unnamed");
142 assert(to->offset == 0);
144 g_free(to->buffer);
145 to->offset = from->offset;
146 to->capacity = from->capacity;
147 to->buffer = from->buffer;
149 from->offset = 0;
150 from->capacity = 0;
151 from->buffer = NULL;
154 void buffer_move(Buffer *to, Buffer *from)
156 if (to->offset == 0) {
157 buffer_move_empty(to, from);
158 return;
161 trace_buffer_move(to->name ?: "unnamed",
162 from->offset,
163 from->name ?: "unnamed");
164 buffer_reserve(to, from->offset);
165 buffer_append(to, from->buffer, from->offset);
167 g_free(from->buffer);
168 from->offset = 0;
169 from->capacity = 0;
170 from->buffer = NULL;