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* QEMU VNC display driver: Zlib Run-length Encoding (ZRLE)
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* From libvncserver/libvncserver/zrle.c
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* Copyright (C) 2002 RealVNC Ltd. All Rights Reserved.
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* Copyright (C) 2003 Sun Microsystems, Inc.
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* Copyright (C) 2010 Corentin Chary <corentin.chary@gmail.com>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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#include "vnc-enc-zrle.h"
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static const int bits_per_packed_pixel[] = {
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0, 1, 2, 2, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4
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static void vnc_zrle_start(VncState *vs)
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buffer_reset(&vs->zrle.zrle);
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/* make the output buffer be the zlib buffer, so we can compress it later */
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vs->zrle.tmp = vs->output;
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vs->output = vs->zrle.zrle;
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static void vnc_zrle_stop(VncState *vs)
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/* switch back to normal output/zlib buffers */
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vs->zrle.zrle = vs->output;
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vs->output = vs->zrle.tmp;
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static void *zrle_convert_fb(VncState *vs, int x, int y, int w, int h,
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buffer_reset(&vs->zrle.fb);
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buffer_reserve(&vs->zrle.fb, w * h * bpp + bpp);
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vs->output = vs->zrle.fb;
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vnc_raw_send_framebuffer_update(vs, x, y, w, h);
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vs->zrle.fb = vs->output;
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return vs->zrle.fb.buffer;
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static int zrle_compress_data(VncState *vs, int level)
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z_streamp zstream = &vs->zrle.stream;
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buffer_reset(&vs->zrle.zlib);
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if (zstream->opaque != vs) {
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zstream->zalloc = vnc_zlib_zalloc;
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zstream->zfree = vnc_zlib_zfree;
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err = deflateInit2(zstream, level, Z_DEFLATED, MAX_WBITS,
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MAX_MEM_LEVEL, Z_DEFAULT_STRATEGY);
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fprintf(stderr, "VNC: error initializing zlib\n");
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/* reserve memory in output buffer */
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buffer_reserve(&vs->zrle.zlib, vs->zrle.zrle.offset + 64);
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zstream->next_in = vs->zrle.zrle.buffer;
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zstream->avail_in = vs->zrle.zrle.offset;
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zstream->next_out = vs->zrle.zlib.buffer + vs->zrle.zlib.offset;
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zstream->avail_out = vs->zrle.zlib.capacity - vs->zrle.zlib.offset;
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zstream->data_type = Z_BINARY;
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if (deflate(zstream, Z_SYNC_FLUSH) != Z_OK) {
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fprintf(stderr, "VNC: error during zrle compression\n");
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vs->zrle.zlib.offset = vs->zrle.zlib.capacity - zstream->avail_out;
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return vs->zrle.zlib.offset;
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/* Try to work out whether to use RLE and/or a palette. We do this by
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* estimating the number of bytes which will be generated and picking the
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* method which results in the fewest bytes. Of course this may not result
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* in the fewest bytes after compression... */
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static void zrle_choose_palette_rle(VncState *vs, int w, int h,
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VncPalette *palette, int bpp_out,
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int runs, int single_pixels,
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bool *use_rle, bool *use_palette)
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size_t estimated_bytes;
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size_t plain_rle_bytes;
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*use_palette = *use_rle = false;
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estimated_bytes = w * h * (bpp_out / 8); /* start assuming raw */
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if (zywrle_level > 0 && !(zywrle_level & 0x80))
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estimated_bytes >>= zywrle_level;
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plain_rle_bytes = ((bpp_out / 8) + 1) * (runs + single_pixels);
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if (plain_rle_bytes < estimated_bytes) {
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estimated_bytes = plain_rle_bytes;
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if (palette_size(palette) < 128) {
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int palette_rle_bytes;
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palette_rle_bytes = (bpp_out / 8) * palette_size(palette);
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palette_rle_bytes += 2 * runs + single_pixels;
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if (palette_rle_bytes < estimated_bytes) {
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estimated_bytes = palette_rle_bytes;
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if (palette_size(palette) < 17) {
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packed_bytes = (bpp_out / 8) * palette_size(palette);
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packed_bytes += w * h *
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bits_per_packed_pixel[palette_size(palette)-1] / 8;
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if (packed_bytes < estimated_bytes) {
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estimated_bytes = packed_bytes;
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static void zrle_write_u32(VncState *vs, uint32_t value)
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vnc_write(vs, (uint8_t *)&value, 4);
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static void zrle_write_u24a(VncState *vs, uint32_t value)
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vnc_write(vs, (uint8_t *)&value, 3);
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static void zrle_write_u24b(VncState *vs, uint32_t value)
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vnc_write(vs, ((uint8_t *)&value) + 1, 3);
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static void zrle_write_u16(VncState *vs, uint16_t value)
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vnc_write(vs, (uint8_t *)&value, 2);
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static void zrle_write_u8(VncState *vs, uint8_t value)
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vnc_write_u8(vs, value);
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#define ENDIAN_LITTLE 0
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#define ZYWRLE_ENDIAN ENDIAN_NO
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_LITTLE
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_BIG
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_LITTLE
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_BIG
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_LITTLE
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_BIG
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#include "vnc-enc-zrle-template.c"
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#define ZRLE_COMPACT_PIXEL 24a
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#define ZYWRLE_ENDIAN ENDIAN_LITTLE
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_BIG
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#include "vnc-enc-zrle-template.c"
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#undef ZRLE_COMPACT_PIXEL
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#define ZRLE_COMPACT_PIXEL 24b
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#define ZYWRLE_ENDIAN ENDIAN_LITTLE
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#include "vnc-enc-zrle-template.c"
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#define ZYWRLE_ENDIAN ENDIAN_BIG
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#include "vnc-enc-zrle-template.c"
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#undef ZRLE_COMPACT_PIXEL
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static int zrle_send_framebuffer_update(VncState *vs, int x, int y,
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bool be = !!(vs->clientds.flags & QEMU_BIG_ENDIAN_FLAG);
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if (vs->zrle.type == VNC_ENCODING_ZYWRLE) {
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if (!vs->vd->lossy || vs->tight.quality == (uint8_t)-1
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|| vs->tight.quality == 9) {
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vs->zrle.type = VNC_ENCODING_ZRLE;
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} else if (vs->tight.quality < 3) {
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} else if (vs->tight.quality < 6) {
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switch(vs->clientds.pf.bytes_per_pixel) {
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zrle_encode_8ne(vs, x, y, w, h, zywrle_level);
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if (vs->clientds.pf.gmax > 0x1F) {
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zrle_encode_16be(vs, x, y, w, h, zywrle_level);
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zrle_encode_16le(vs, x, y, w, h, zywrle_level);
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zrle_encode_15be(vs, x, y, w, h, zywrle_level);
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zrle_encode_15le(vs, x, y, w, h, zywrle_level);
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bool fits_in_ls3bytes;
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bool fits_in_ms3bytes;
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((vs->clientds.pf.rmax << vs->clientds.pf.rshift) < (1 << 24) &&
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(vs->clientds.pf.gmax << vs->clientds.pf.gshift) < (1 << 24) &&
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(vs->clientds.pf.bmax << vs->clientds.pf.bshift) < (1 << 24));
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fits_in_ms3bytes = (vs->clientds.pf.rshift > 7 &&
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vs->clientds.pf.gshift > 7 &&
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vs->clientds.pf.bshift > 7);
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if ((fits_in_ls3bytes && !be) || (fits_in_ms3bytes && be)) {
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zrle_encode_24abe(vs, x, y, w, h, zywrle_level);
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zrle_encode_24ale(vs, x, y, w, h, zywrle_level);
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} else if ((fits_in_ls3bytes && be) || (fits_in_ms3bytes && !be)) {
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zrle_encode_24bbe(vs, x, y, w, h, zywrle_level);
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zrle_encode_24ble(vs, x, y, w, h, zywrle_level);
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zrle_encode_32be(vs, x, y, w, h, zywrle_level);
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zrle_encode_32le(vs, x, y, w, h, zywrle_level);
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bytes = zrle_compress_data(vs, Z_DEFAULT_COMPRESSION);
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vnc_framebuffer_update(vs, x, y, w, h, vs->zrle.type);
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vnc_write_u32(vs, bytes);
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vnc_write(vs, vs->zrle.zlib.buffer, vs->zrle.zlib.offset);
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int vnc_zrle_send_framebuffer_update(VncState *vs, int x, int y, int w, int h)
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vs->zrle.type = VNC_ENCODING_ZRLE;
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return zrle_send_framebuffer_update(vs, x, y, w, h);
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int vnc_zywrle_send_framebuffer_update(VncState *vs, int x, int y, int w, int h)
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vs->zrle.type = VNC_ENCODING_ZYWRLE;
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return zrle_send_framebuffer_update(vs, x, y, w, h);
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void vnc_zrle_clear(VncState *vs)
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if (vs->zrle.stream.opaque) {
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deflateEnd(&vs->zrle.stream);
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buffer_free(&vs->zrle.zrle);
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buffer_free(&vs->zrle.fb);
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buffer_free(&vs->zrle.zlib);