gtk/gdk/broadway/broadway-buffer.c
Pierre-Eric Pelloux-Prayer ad39298f6d broadway: make sure color/delta run length do not overflow
Fixes bug 723045.
2014-03-21 21:45:04 +01:00

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#include "config.h"
#include "broadway-buffer.h"
#include <string.h>
/* This code is based on some code from weston with this license:
*
* Copyright © 2012 Intel Corporation
*
* Permission to use, copy, modify, distribute, and sell this software and
* its documentation for any purpose is hereby granted without fee, provided
* that the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation, and that the name of the copyright holders not be used in
* advertising or publicity pertaining to distribution of the software
* without specific, written prior permission. The copyright holders make
* no representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
* THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS
* SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS, IN NO EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY
* SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
* RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF
* CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
struct entry {
int count;
int matches;
guint32 hash;
int x, y;
int index;
};
struct _BroadwayBuffer {
guint8 *data;
struct entry *table;
int width, height, stride;
int encoded;
int block_stride, length, block_count, shift;
int stats[5];
int clashes;
};
static const guint32 prime = 0x1f821e2d;
static const guint32 end_prime = 0xf907ec81; /* prime^block_size */
#if 0
static const guint32 vprime = 0x0137b89d;
static const guint32 end_vprime = 0xaea9a281; /* vprime^block_size */
#else
static const guint32 vprime = 0xf907ec81;
static const guint32 end_vprime = 0xcdb99001; /* vprime^block_size */
#endif
static const guint32 step = 0x0ac93019;
static const int block_size = 32, block_mask = 31;
static gboolean
verify_block_match (BroadwayBuffer *buffer, int x, int y,
BroadwayBuffer *prev, struct entry *entry)
{
int i;
void *old, *match;
int w1, w2, h1, h2;
w1 = block_size;
if (x + block_size > buffer->width)
w1 = buffer->width - x;
h1 = block_size;
if (y + block_size > buffer->height)
h1 = buffer->height - y;
w2 = block_size;
if (entry->x + block_size > prev->width)
w2 = prev->width - entry->x;
h2 = block_size;
if (entry->y + block_size > prev->height)
h2 = prev->height - entry->y;
if (w1 != w2 || h1 != h2)
return FALSE;
for (i = 0; i < h1; i++)
{
match = buffer->data + (y + i) * buffer->stride + x * 4;
old = prev->data + (entry->y + i) * prev->stride + entry->x * 4;
if (memcmp (match, old, w1 * 4) != 0)
{
buffer->clashes++;
return FALSE;
}
}
return TRUE;
}
static void
insert_block (BroadwayBuffer *buffer, guint32 h, int x, int y)
{
struct entry *entry;
int i;
guint32 collision = 0;
entry = &buffer->table[h >> buffer->shift];
for (i = step; entry->count > 0 && entry->hash != h; i += step)
{
entry = &buffer->table[(h + i) >> buffer->shift];
collision++;
}
entry->hash = h;
entry->count++;
entry->x = x;
entry->y = y;
entry->index = (buffer->block_stride * y + x) / block_size;
if (collision > G_N_ELEMENTS (buffer->stats) - 1)
collision = G_N_ELEMENTS (buffer->stats) - 1;
buffer->stats[collision]++;
}
static struct entry *
lookup_block (BroadwayBuffer *prev, guint32 h)
{
guint32 i;
struct entry *entry;
int shift = prev->shift;
for (i = h;
entry = &prev->table[i >> shift], entry->count > 0;
i += step)
{
if (entry->hash == h)
return entry;
}
return NULL;
}
struct encoder {
guint32 color;
guint32 color_run;
guint32 delta;
guint32 delta_run;
GString *dest;
int bytes;
};
/* Encoding:
*
* - all 1 pixel colors are encoded literally
*
* - We dont need to support colors with alpha 0 and non-zero
* color components, as they mean the same on the canvas anyway.
* So we use these as special codes:
*
* - 0x00 00 00 00 : one alpha 0 pixel
* - 0xaa rr gg bb : one color pixel, alpha > 0
* - 0x00 1x xx xx : delta 0 run, x is length, (20 bits)
* - 0x00 2x xx xx 0x xxxx yyyy: block ref, block number x (20 bits) at x, y
* - 0x00 3x xx xx 0xaarrggbb : solid color run, length x
* - 0x00 4x xx xx 0xaarrggbb : delta run, length x
*
*/
static void
emit (struct encoder *encoder, guint32 symbol)
{
g_string_append_len (encoder->dest, (char *)&symbol, sizeof (guint32));
encoder->bytes += sizeof (guint32);
}
static void
encode_run (struct encoder *encoder)
{
if (encoder->color_run == 0 && encoder->delta_run == 0)
return;
if (encoder->color_run >= encoder->delta_run)
{
if (encoder->color_run == 1)
emit (encoder, encoder->color);
else
{
emit (encoder, 0x00300000 | encoder->color_run);
emit (encoder, encoder->color);
}
}
else
{
if (encoder->delta == 0)
emit(encoder, 0x00100000 | encoder->delta_run);
else
{
emit(encoder, 0x00400000 | encoder->delta_run);
emit(encoder, encoder->delta);
}
}
}
static void
encode_pixel (struct encoder *encoder, guint32 color, guint32 prev_color)
{
guint32 delta = 0;
guint32 a, r, g, b;
if (color == prev_color)
delta = 0;
else if (prev_color == 0)
delta = color;
else
{
a = ((color & 0xff000000) - (prev_color & 0xff000000)) & 0xff000000;
r = ((color & 0x00ff0000) - (prev_color & 0x00ff0000)) & 0x00ff0000;
g = ((color & 0x0000ff00) - (prev_color & 0x0000ff00)) & 0x0000ff00;
b = ((color & 0x000000ff) - (prev_color & 0x000000ff)) & 0x000000ff;
delta = a | r | g | b;
}
if ((encoder->color != color &&
encoder->color_run > encoder->delta_run) ||
(encoder->delta != delta &&
encoder->delta_run > encoder->color_run) ||
(encoder->delta != delta && encoder->color != color) ||
(encoder->delta_run == 0xFFFFF || encoder->color_run == 0xFFFFF))
{
encode_run (encoder);
encoder->color_run = 1;
encoder->color = color;
encoder->delta_run = 1;
encoder->delta = delta;
return;
}
if (encoder->color == color)
encoder->color_run++;
else
{
encoder->color_run = 1;
encoder->color = color;
}
if (encoder->delta == delta)
encoder->delta_run++;
else
{
encoder->delta_run = 1;
encoder->delta = delta;
}
}
void
encoder_flush (struct encoder *encoder)
{
encode_run (encoder);
}
static void
encode_block (struct encoder *encoder, struct entry *entry, int x, int y)
{
/* 0x00 2x xx xx 0x xxxx yyyy:
* block ref, block number x (20 bits) at x, y */
/* FIXME: Maybe don't encode pixels under blocks and just emit
* blocks at their position within the stream. */
emit (encoder, 0x00200000 | entry->index);
emit (encoder, (x << 16) | y);
}
void
broadway_buffer_destroy (BroadwayBuffer *buffer)
{
g_free (buffer->data);
g_free (buffer->table);
g_free (buffer);
}
int
broadway_buffer_get_width (BroadwayBuffer *buffer)
{
return buffer->width;
}
int
broadway_buffer_get_height (BroadwayBuffer *buffer)
{
return buffer->height;
}
static void
unpremultiply_line (void *destp, void *srcp, int width)
{
guint32 *src = srcp;
guint32 *dest = destp;
guint32 *end = src + width;
while (src < end)
{
guint32 pixel;
guint8 alpha, r, g, b;
pixel = *src++;
alpha = (pixel & 0xff000000) >> 24;
if (alpha == 0xff)
*dest++ = pixel;
else if (alpha == 0)
*dest++ = 0;
else
{
r = (((pixel & 0xff0000) >> 16) * 255 + alpha / 2) / alpha;
g = (((pixel & 0x00ff00) >> 8) * 255 + alpha / 2) / alpha;
b = (((pixel & 0x0000ff) >> 0) * 255 + alpha / 2) / alpha;
*dest++ = (guint32)alpha << 24 | (guint32)r << 16 | (guint32)g << 8 | (guint32)b;
}
}
}
BroadwayBuffer *
broadway_buffer_create (int width, int height, guint8 *data, int stride)
{
BroadwayBuffer *buffer;
int y, bits_required;
buffer = g_new0 (BroadwayBuffer, 1);
buffer->width = width;
buffer->stride = width * 4;
buffer->height = height;
buffer->block_stride = (width + block_size - 1) / block_size;
buffer->block_count =
buffer->block_stride * ((height + block_size - 1) / block_size);
bits_required = g_bit_storage (buffer->block_count * 4);
buffer->shift = 32 - bits_required;
buffer->length = 1 << bits_required;
buffer->table = g_malloc0 (buffer->length * sizeof buffer->table[0]);
memset (buffer->stats, 0, sizeof buffer->stats);
buffer->clashes = 0;
buffer->data = g_malloc (buffer->stride * height);
for (y = 0; y < height; y++)
unpremultiply_line (buffer->data + y * buffer->stride, data + y * stride, width);
return buffer;
}
void
broadway_buffer_encode (BroadwayBuffer *buffer, BroadwayBuffer *prev, GString *dest)
{
struct entry *entry;
int i, j, k;
int x0, x1, y0, y1;
guint32 *block_hashes;
guint32 hash, bottom_hash, h, *line, *bottom, *prev_line;
int width, height;
struct encoder encoder = { 0 };
int *skyline, skyline_pixels;
int matches;
width = buffer->width;
height = buffer->height;
x0 = 0;
x1 = width;
y0 = 0;
y1 = height;
skyline = g_malloc0 ((width + block_size) * sizeof skyline[0]);
block_hashes = g_malloc0 (width * sizeof block_hashes[0]);
matches = 0;
encoder.dest = dest;
// Calculate the block hashes for the first row
for (i = y0; i < MIN(y1, y0 + block_size); i++)
{
line = (guint32 *)(buffer->data + i * buffer->stride);
hash = 0;
for (j = x0; j < MIN(x1, x0 + block_size); j++)
hash = hash * prime + line[j];
for (j = j; j < x0 + block_size; j++)
hash = hash * prime;
for (j = x0; j < x1; j++)
{
block_hashes[j] = block_hashes[j] * vprime + hash;
hash = hash * prime - line[j] * end_prime;
if (j + block_size < width)
hash += line[j + block_size];
}
}
// Do the last rows if height < block_size
for (i = i; i < y0 + block_size; i++)
{
for (j = x0; j < x1; j++)
block_hashes[j] = block_hashes[j] * vprime;
}
for (i = y0; i < y1; i++)
{
line = (guint32 *) (buffer->data + i * buffer->stride);
bottom = (guint32 *) (buffer->data + (i + block_size) * buffer->stride);
bottom_hash = 0;
hash = 0;
skyline_pixels = 0;
if (prev && i < prev->height)
prev_line = (guint32 *) (prev->data + i * prev->stride);
else
prev_line = NULL;
for (j = x0; j < x0 + block_size; j++)
{
hash = hash * prime;
if (j < width)
hash += line[j];
if (i + block_size < height)
{
bottom_hash = bottom_hash * prime;
if (j < width)
bottom_hash += bottom[j];
}
if (i < skyline[j])
skyline_pixels = 0;
else
skyline_pixels++;
}
for (j = x0; j < x1; j++)
{
if (i < skyline[j])
encode_pixel (&encoder, line[j], line[j]);
else if (prev)
{
/* FIXME: Add back overlap exception
* for consecutive blocks */
h = block_hashes[j];
entry = lookup_block (prev, h);
if (entry && entry->count < 2 &&
skyline_pixels >= block_size &&
verify_block_match (buffer, j, i, prev, entry) &&
(entry->x != j || entry->y != i))
{
matches++;
encode_block (&encoder, entry, j, i);
for (k = 0; k < block_size; k++)
skyline[j + k] = i + block_size;
encode_pixel (&encoder, line[j], line[j]);
}
else
{
if (prev_line && j < prev->width)
encode_pixel (&encoder, line[j],
prev_line[j]);
else
encode_pixel (&encoder, line[j], 0);
}
}
else
encode_pixel (&encoder, line[j], 0);
if (i < skyline[j + block_size])
skyline_pixels = 0;
else
skyline_pixels++;
/* Insert block in hash table if we're on a
* grid point. */
if (((i | j) & block_mask) == 0 && !buffer->encoded)
insert_block (buffer, block_hashes[j], j, i);
/* Update sliding block hash */
block_hashes[j] =
block_hashes[j] * vprime + bottom_hash -
hash * end_vprime;
if (i + block_size < height)
{
bottom_hash = bottom_hash * prime - bottom[j] * end_prime;
if (j + block_size < width)
bottom_hash += bottom[j + block_size];
}
hash = hash * prime - line[j] * end_prime;
if (j + block_size < width)
hash += line[j + block_size] ;
}
}
encoder_flush (&encoder);
#if 0
fprintf(stderr, "collision stats:");
for (i = 0; i < (int) G_N_ELEMENTS(buffer->stats); i++)
fprintf(stderr, "%c%d", i == 0 ? ' ' : '/', buffer->stats[i]);
fprintf(stderr, "\n");
fprintf(stderr, "%d / %d blocks (%d%%) matched, %d clashes\n",
matches, buffer->block_count,
100 * matches / buffer->block_count, buffer->clashes);
fprintf(stderr, "output stream %d bytes, raw buffer %d bytes (%d%%)\n",
encoder.bytes, height * buffer->stride,
100 * encoder.bytes / (height * buffer->stride));
#endif
g_free (skyline);
g_free (block_hashes);
buffer->encoded = TRUE;
}