qemu/util/buffer.c
Chetan Pant 61f3c91a67 nomaintainer: Fix Lesser GPL version number
There is no "version 2" of the "Lesser" General Public License.
It is either "GPL version 2.0" or "Lesser GPL version 2.1".
This patch replaces all occurrences of "Lesser GPL version 2" with
"Lesser GPL version 2.1" in comment section.

This patch contains all the files, whose maintainer I could not get
from ‘get_maintainer.pl’ script.

Signed-off-by: Chetan Pant <chetan4windows@gmail.com>
Message-Id: <20201023124424.20177-1-chetan4windows@gmail.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
[thuth: Adapted exec.c and qdev-monitor.c to new location]
Signed-off-by: Thomas Huth <thuth@redhat.com>
2020-11-15 17:04:40 +01:00

174 lines
4.7 KiB
C

/*
* QEMU generic buffers
*
* Copyright (c) 2015 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "qemu/host-utils.h"
#include "qemu/buffer.h"
#include "trace.h"
#define BUFFER_MIN_INIT_SIZE 4096
#define BUFFER_MIN_SHRINK_SIZE 65536
/* define the factor alpha for the exponential smoothing
* that is used in the average size calculation. a shift
* of 7 results in an alpha of 1/2^7. */
#define BUFFER_AVG_SIZE_SHIFT 7
static size_t buffer_req_size(Buffer *buffer, size_t len)
{
return MAX(BUFFER_MIN_INIT_SIZE,
pow2ceil(buffer->offset + len));
}
static void buffer_adj_size(Buffer *buffer, size_t len)
{
size_t old = buffer->capacity;
buffer->capacity = buffer_req_size(buffer, len);
buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
trace_buffer_resize(buffer->name ?: "unnamed",
old, buffer->capacity);
/* make it even harder for the buffer to shrink, reset average size
* to current capacity if it is larger than the average. */
buffer->avg_size = MAX(buffer->avg_size,
buffer->capacity << BUFFER_AVG_SIZE_SHIFT);
}
void buffer_init(Buffer *buffer, const char *name, ...)
{
va_list ap;
va_start(ap, name);
buffer->name = g_strdup_vprintf(name, ap);
va_end(ap);
}
static uint64_t buffer_get_avg_size(Buffer *buffer)
{
return buffer->avg_size >> BUFFER_AVG_SIZE_SHIFT;
}
void buffer_shrink(Buffer *buffer)
{
size_t new;
/* Calculate the average size of the buffer as
* avg_size = avg_size * ( 1 - a ) + required_size * a
* where a is 1 / 2 ^ BUFFER_AVG_SIZE_SHIFT. */
buffer->avg_size *= (1 << BUFFER_AVG_SIZE_SHIFT) - 1;
buffer->avg_size >>= BUFFER_AVG_SIZE_SHIFT;
buffer->avg_size += buffer_req_size(buffer, 0);
/* And then only shrink if the average size of the buffer is much
* too big, to avoid bumping up & down the buffers all the time.
* realloc() isn't exactly cheap ... */
new = buffer_req_size(buffer, buffer_get_avg_size(buffer));
if (new < buffer->capacity >> 3 &&
new >= BUFFER_MIN_SHRINK_SIZE) {
buffer_adj_size(buffer, buffer_get_avg_size(buffer));
}
buffer_adj_size(buffer, 0);
}
void buffer_reserve(Buffer *buffer, size_t len)
{
if ((buffer->capacity - buffer->offset) < len) {
buffer_adj_size(buffer, len);
}
}
gboolean buffer_empty(Buffer *buffer)
{
return buffer->offset == 0;
}
uint8_t *buffer_end(Buffer *buffer)
{
return buffer->buffer + buffer->offset;
}
void buffer_reset(Buffer *buffer)
{
buffer->offset = 0;
buffer_shrink(buffer);
}
void buffer_free(Buffer *buffer)
{
trace_buffer_free(buffer->name ?: "unnamed", buffer->capacity);
g_free(buffer->buffer);
g_free(buffer->name);
buffer->offset = 0;
buffer->capacity = 0;
buffer->buffer = NULL;
buffer->name = NULL;
}
void buffer_append(Buffer *buffer, const void *data, size_t len)
{
memcpy(buffer->buffer + buffer->offset, data, len);
buffer->offset += len;
}
void buffer_advance(Buffer *buffer, size_t len)
{
memmove(buffer->buffer, buffer->buffer + len,
(buffer->offset - len));
buffer->offset -= len;
buffer_shrink(buffer);
}
void buffer_move_empty(Buffer *to, Buffer *from)
{
trace_buffer_move_empty(to->name ?: "unnamed",
from->offset,
from->name ?: "unnamed");
assert(to->offset == 0);
g_free(to->buffer);
to->offset = from->offset;
to->capacity = from->capacity;
to->buffer = from->buffer;
from->offset = 0;
from->capacity = 0;
from->buffer = NULL;
}
void buffer_move(Buffer *to, Buffer *from)
{
if (to->offset == 0) {
buffer_move_empty(to, from);
return;
}
trace_buffer_move(to->name ?: "unnamed",
from->offset,
from->name ?: "unnamed");
buffer_reserve(to, from->offset);
buffer_append(to, from->buffer, from->offset);
g_free(from->buffer);
from->offset = 0;
from->capacity = 0;
from->buffer = NULL;
}