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87776ab72b
Move it to the actual users. There are some inclusions of qemu/host-utils.h in headers, but they are all necessary. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
174 lines
4.7 KiB
C
174 lines
4.7 KiB
C
/*
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* QEMU generic buffers
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*
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* Copyright (c) 2015 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "qemu/osdep.h"
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#include "qemu/host-utils.h"
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#include "qemu/buffer.h"
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#include "trace.h"
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#define BUFFER_MIN_INIT_SIZE 4096
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#define BUFFER_MIN_SHRINK_SIZE 65536
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/* define the factor alpha for the exponential smoothing
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* that is used in the average size calculation. a shift
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* of 7 results in an alpha of 1/2^7. */
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#define BUFFER_AVG_SIZE_SHIFT 7
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static size_t buffer_req_size(Buffer *buffer, size_t len)
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{
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return MAX(BUFFER_MIN_INIT_SIZE,
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pow2ceil(buffer->offset + len));
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}
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static void buffer_adj_size(Buffer *buffer, size_t len)
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{
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size_t old = buffer->capacity;
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buffer->capacity = buffer_req_size(buffer, len);
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buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
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trace_buffer_resize(buffer->name ?: "unnamed",
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old, buffer->capacity);
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/* make it even harder for the buffer to shrink, reset average size
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* to current capacity if it is larger than the average. */
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buffer->avg_size = MAX(buffer->avg_size,
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buffer->capacity << BUFFER_AVG_SIZE_SHIFT);
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}
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void buffer_init(Buffer *buffer, const char *name, ...)
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{
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va_list ap;
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va_start(ap, name);
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buffer->name = g_strdup_vprintf(name, ap);
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va_end(ap);
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}
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static uint64_t buffer_get_avg_size(Buffer *buffer)
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{
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return buffer->avg_size >> BUFFER_AVG_SIZE_SHIFT;
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}
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void buffer_shrink(Buffer *buffer)
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{
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size_t new;
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/* Calculate the average size of the buffer as
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* avg_size = avg_size * ( 1 - a ) + required_size * a
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* where a is 1 / 2 ^ BUFFER_AVG_SIZE_SHIFT. */
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buffer->avg_size *= (1 << BUFFER_AVG_SIZE_SHIFT) - 1;
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buffer->avg_size >>= BUFFER_AVG_SIZE_SHIFT;
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buffer->avg_size += buffer_req_size(buffer, 0);
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/* And then only shrink if the average size of the buffer is much
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* too big, to avoid bumping up & down the buffers all the time.
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* realloc() isn't exactly cheap ... */
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new = buffer_req_size(buffer, buffer_get_avg_size(buffer));
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if (new < buffer->capacity >> 3 &&
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new >= BUFFER_MIN_SHRINK_SIZE) {
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buffer_adj_size(buffer, buffer_get_avg_size(buffer));
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}
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buffer_adj_size(buffer, 0);
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}
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void buffer_reserve(Buffer *buffer, size_t len)
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{
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if ((buffer->capacity - buffer->offset) < len) {
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buffer_adj_size(buffer, len);
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}
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}
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gboolean buffer_empty(Buffer *buffer)
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{
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return buffer->offset == 0;
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}
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uint8_t *buffer_end(Buffer *buffer)
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{
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return buffer->buffer + buffer->offset;
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}
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void buffer_reset(Buffer *buffer)
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{
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buffer->offset = 0;
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buffer_shrink(buffer);
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}
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void buffer_free(Buffer *buffer)
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{
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trace_buffer_free(buffer->name ?: "unnamed", buffer->capacity);
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g_free(buffer->buffer);
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g_free(buffer->name);
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buffer->offset = 0;
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buffer->capacity = 0;
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buffer->buffer = NULL;
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buffer->name = NULL;
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}
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void buffer_append(Buffer *buffer, const void *data, size_t len)
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{
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memcpy(buffer->buffer + buffer->offset, data, len);
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buffer->offset += len;
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}
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void buffer_advance(Buffer *buffer, size_t len)
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{
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memmove(buffer->buffer, buffer->buffer + len,
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(buffer->offset - len));
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buffer->offset -= len;
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buffer_shrink(buffer);
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}
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void buffer_move_empty(Buffer *to, Buffer *from)
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{
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trace_buffer_move_empty(to->name ?: "unnamed",
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from->offset,
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from->name ?: "unnamed");
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assert(to->offset == 0);
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g_free(to->buffer);
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to->offset = from->offset;
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to->capacity = from->capacity;
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to->buffer = from->buffer;
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from->offset = 0;
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from->capacity = 0;
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from->buffer = NULL;
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}
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void buffer_move(Buffer *to, Buffer *from)
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{
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if (to->offset == 0) {
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buffer_move_empty(to, from);
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return;
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}
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trace_buffer_move(to->name ?: "unnamed",
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from->offset,
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from->name ?: "unnamed");
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buffer_reserve(to, from->offset);
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buffer_append(to, from->buffer, from->offset);
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g_free(from->buffer);
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from->offset = 0;
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from->capacity = 0;
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from->buffer = NULL;
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}
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