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spice/server/glz-encode.tmpl.c
Frediano Ziglio 461288534f glz-encode: Remove obsolete reference segment 
The GLZ code is basically LZ code (in spice-common) sharing image
segments between multiple images.
The code for RLE check in LZ (common/lz_compress_tmpl.c) is dealing
with both RLE and dictionary matches being:

    if (!distance) {
        /* zero distance means a run */
        PIXEL x = *ref;
        while ((ip < ip_bound) && (ref < ref_limit)) { // TODO: maybe separate a run from
                                                       //       the same seg or from different
                                                       //       ones in order to spare
                                                       //       ref < ref_limit

in GLZ that part was copied to RLE part removing the need for the
second segment ("ref"). However the comment and setting ref variables
were not removed. Remove the old code to avoid confusions.

This also remove a Covscan warning as ref_limit was set not not used
(reported by Uri Lublin).
The warning was:

CLANG warning: "Value stored to 'ref_limit' is never read"

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>
Acked-by: Uri Lublin <uril@redhat.com>
2019-08-12 10:48:02 +01:00

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/*
Copyright (C) 2009 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 <config.h>
#define DJB2_START 5381
#define DJB2_HASH(hash, c) (hash = ((hash << 5) + hash) ^ (c)) //|{hash = ((hash << 5) + hash) + c;}
/*
For each pixel type the following macros are defined:
PIXEL : input type
FNAME(name)
ENCODE_PIXEL(encoder, pixel) : writing a pixel to the compressed buffer (byte by byte)
SAME_PIXEL(pix1, pix2) : comparing two pixels
HASH_FUNC(value, pix_ptr) : hash func of 3 consecutive pixels
*/
#ifdef LZ_PLT
#define PIXEL one_byte_pixel_t
#define FNAME(name) glz_plt_##name
#define ENCODE_PIXEL(e, pix) encode(e, (pix).a) // gets the pixel and write only the needed bytes
// from the pixel
#define SAME_PIXEL(pix1, pix2) ((pix1).a == (pix2).a)
#define MIN_REF_ENCODE_SIZE 4
#define MAX_REF_ENCODE_SIZE 7
#define HASH_FUNC(v, p) { \
v = DJB2_START; \
DJB2_HASH(v, p[0].a); \
DJB2_HASH(v, p[1].a); \
DJB2_HASH(v, p[2].a); \
v &= HASH_MASK; \
}
#endif
#ifdef LZ_RGB_ALPHA
//#undef LZ_RGB_ALPHA
#define PIXEL rgb32_pixel_t
#define FNAME(name) glz_rgb_alpha_##name
#define ENCODE_PIXEL(e, pix) {encode(e, (pix).pad);}
#define SAME_PIXEL(pix1, pix2) ((pix1).pad == (pix2).pad)
#define MIN_REF_ENCODE_SIZE 4
#define MAX_REF_ENCODE_SIZE 7
#define HASH_FUNC(v, p) { \
v = DJB2_START; \
DJB2_HASH(v, p[0].pad); \
DJB2_HASH(v, p[1].pad); \
DJB2_HASH(v, p[2].pad); \
v &= HASH_MASK; \
}
#endif
#ifdef LZ_RGB16
#define PIXEL rgb16_pixel_t
#define FNAME(name) glz_rgb16_##name
#define GET_rgb(pix) ((pix) & 0x7fffu)
#define SAME_PIXEL(p1, p2) (GET_rgb(p1) == GET_rgb(p2))
#define ENCODE_PIXEL(e, pix) {encode(e, (pix) >> 8); encode(e, (pix) & 0xff);}
#define MIN_REF_ENCODE_SIZE 2
#define MAX_REF_ENCODE_SIZE 3
#define HASH_FUNC(v, p) { \
v = DJB2_START; \
DJB2_HASH(v, p[0] & (0x00ff)); \
DJB2_HASH(v, (p[0] >> 8) & (0x007f)); \
DJB2_HASH(v, p[1] & (0x00ff)); \
DJB2_HASH(v, (p[1] >> 8) & (0x007f)); \
DJB2_HASH(v, p[2] & (0x00ff)); \
DJB2_HASH(v, (p[2] >> 8) & (0x007f)); \
v &= HASH_MASK; \
}
#endif
#ifdef LZ_RGB24
#define PIXEL rgb24_pixel_t
#define FNAME(name) glz_rgb24_##name
#endif
#ifdef LZ_RGB32
#define PIXEL rgb32_pixel_t
#define FNAME(name) glz_rgb32_##name
#endif
#if defined(LZ_RGB24) || defined(LZ_RGB32)
#define ENCODE_PIXEL(e, pix) {encode(e, (pix).b); encode(e, (pix).g); encode(e, (pix).r);}
#define MIN_REF_ENCODE_SIZE 2
#define MAX_REF_ENCODE_SIZE 2
#define SAME_PIXEL(p1, p2) ((p1).r == (p2).r && (p1).g == (p2).g && (p1).b == (p2).b)
#define HASH_FUNC(v, p) { \
v = DJB2_START; \
DJB2_HASH(v, p[0].r); \
DJB2_HASH(v, p[0].g); \
DJB2_HASH(v, p[0].b); \
DJB2_HASH(v, p[1].r); \
DJB2_HASH(v, p[1].g); \
DJB2_HASH(v, p[1].b); \
DJB2_HASH(v, p[2].r); \
DJB2_HASH(v, p[2].g); \
DJB2_HASH(v, p[2].b); \
v &= HASH_MASK; \
}
#endif
#define PIXEL_ID(pix_ptr, seg_ptr, pix_per_byte) \
(((pix_ptr) - ((PIXEL *)(seg_ptr)->lines)) * pix_per_byte + (seg_ptr)->pixels_so_far)
#define PIXEL_DIST(src_pix_ptr, src_seg_ptr, ref_pix_ptr, ref_seg_ptr, pix_per_byte) \
((PIXEL_ID(src_pix_ptr,src_seg_ptr, pix_per_byte) - \
PIXEL_ID(ref_pix_ptr, ref_seg_ptr, pix_per_byte)) / pix_per_byte)
/* returns the length of the match. 0 if no match.
if image_distance = 0, pixel_distance is the distance between the matching pixels.
Otherwise, it is the offset from the beginning of the referred image */
static inline size_t FNAME(do_match)(SharedDictionary *dict,
WindowImageSegment *ref_seg, const PIXEL *ref,
const PIXEL *ref_limit,
WindowImageSegment *ip_seg, const PIXEL *ip,
const PIXEL *ip_limit,
int pix_per_byte,
size_t *o_image_dist, size_t *o_pix_distance)
{
int encode_size;
const PIXEL *tmp_ip = ip;
const PIXEL *tmp_ref = ref;
if (ref > (ref_limit - MIN_REF_ENCODE_SIZE)) {
return 0; // in case the hash entry is not relevant
}
/* min match length == MIN_REF_ENCODE_SIZE (depends on pixel type) */
if (!SAME_PIXEL(*tmp_ref, *tmp_ip)) {
return 0;
} else {
tmp_ref++;
tmp_ip++;
}
if (!SAME_PIXEL(*tmp_ref, *tmp_ip)) {
return 0;
} else {
tmp_ref++;
tmp_ip++;
}
#if defined(LZ_PLT) || defined(LZ_RGB_ALPHA)
if (!SAME_PIXEL(*tmp_ref, *tmp_ip)) {
return 0;
} else {
tmp_ref++;
tmp_ip++;
}
if (!SAME_PIXEL(*tmp_ref, *tmp_ip)) {
return 0;
} else {
tmp_ref++;
tmp_ip++;
}
#endif
*o_image_dist = ip_seg->image->id - ref_seg->image->id;
if (!(*o_image_dist)) { // the ref is inside the same image - encode distance
*o_pix_distance = PIXEL_DIST(ip, ip_seg, ref, ref_seg, pix_per_byte);
} else { // the ref is at different image - encode offset from the image start
*o_pix_distance = PIXEL_DIST(ref, ref_seg,
(PIXEL *)(dict->window.segs[ref_seg->image->first_seg].lines),
&dict->window.segs[ref_seg->image->first_seg],
pix_per_byte);
}
if ((*o_pix_distance == 0) || (*o_pix_distance >= MAX_PIXEL_LONG_DISTANCE) ||
(*o_image_dist > MAX_IMAGE_DIST)) {
return 0;
}
/* continue the match*/
while ((tmp_ip < ip_limit) && (tmp_ref < ref_limit)) {
if (!SAME_PIXEL(*tmp_ref, *tmp_ip)) {
break;
} else {
tmp_ref++;
tmp_ip++;
}
}
if ((tmp_ip - ip) > MAX_REF_ENCODE_SIZE) {
return (tmp_ip - ip);
}
encode_size = get_encode_ref_size(*o_image_dist, *o_pix_distance);
// min number of identical pixels for a match
#if defined(LZ_RGB16)
encode_size /= 2;
#elif defined(LZ_RGB24) || defined(LZ_RGB32)
encode_size /= 3;
#endif
encode_size++; // the minimum match
// match len is smaller than the encoding - not worth encoding
if ((tmp_ip - ip) < encode_size) {
return 0;
}
return (tmp_ip - ip);
}
/* compresses one segment starting from 'from'.
In order to encode a match, we use pixels resolution when we encode RGB image,
and bytes count when we encode PLT.
*/
static void FNAME(compress_seg)(Encoder *encoder, uint32_t seg_idx, PIXEL *from, int copied)
{
WindowImageSegment *seg = &encoder->dict->window.segs[seg_idx];
const PIXEL *ip = from;
const PIXEL *ip_bound = (PIXEL *)(seg->lines_end) - BOUND_OFFSET;
const PIXEL *ip_limit = (PIXEL *)(seg->lines_end) - LIMIT_OFFSET;
int hval;
int copy = copied;
#ifdef LZ_PLT
int pix_per_byte = PLT_PIXELS_PER_BYTE[encoder->cur_image.type];
#else
int pix_per_byte = 1;
#endif
#ifdef DEBUG_ENCODE
int n_encoded = 0;
#endif
if (copy == 0) {
encode_copy_count(encoder, MAX_COPY - 1);
}
while (LZ_EXPECT_CONDITIONAL(ip < ip_limit)) {
const PIXEL *ref;
const PIXEL *ref_limit;
WindowImageSegment *ref_seg;
uint32_t ref_seg_idx;
size_t pix_dist;
size_t image_dist;
/* minimum match length */
size_t len = 0;
/* comparison starting-point */
const PIXEL *anchor = ip;
#ifdef CHAINED_HASH
int hash_id = 0;
size_t best_len = 0;
size_t best_pix_dist = 0;
size_t best_image_dist = 0;
#endif
/* check for a run */
if (LZ_EXPECT_CONDITIONAL(ip > (PIXEL *)(seg->lines))) {
if (SAME_PIXEL(ip[-1], ip[0]) && SAME_PIXEL(ip[0], ip[1]) && SAME_PIXEL(ip[1], ip[2])) {
PIXEL x = ip[2];
pix_dist = 1;
image_dist = 0;
ip += 3;
len = 3;
while (ip < ip_bound) {
if (!SAME_PIXEL(*ip, x)) {
ip++;
break;
} else {
ip++;
len++;
}
}
goto match;
} // END RLE MATCH
}
/* find potential match */
HASH_FUNC(hval, ip);
#ifdef CHAINED_HASH
for (hash_id = 0; hash_id < HASH_CHAIN_SIZE; hash_id++) {
ref_seg_idx = encoder->dict->htab[hval][hash_id].image_seg_idx;
#else
ref_seg_idx = encoder->dict->htab[hval].image_seg_idx;
#endif
ref_seg = encoder->dict->window.segs + ref_seg_idx;
if (REF_SEG_IS_VALID(encoder->dict, encoder->id,
ref_seg, seg)) {
#ifdef CHAINED_HASH
ref = ((PIXEL *)ref_seg->lines) + encoder->dict->htab[hval][hash_id].ref_pix_idx;
#else
ref = ((PIXEL *)ref_seg->lines) + encoder->dict->htab[hval].ref_pix_idx;
#endif
ref_limit = (PIXEL *)ref_seg->lines_end;
len = FNAME(do_match)(encoder->dict, ref_seg, ref, ref_limit, seg, ip, ip_bound,
pix_per_byte,
&image_dist, &pix_dist);
#ifdef CHAINED_HASH
// TODO. not compare len but rather len - encode_size
if (len > best_len) {
best_len = len;
best_pix_dist = pix_dist;
best_image_dist = image_dist;
}
#endif
}
#ifdef CHAINED_HASH
} // end chain loop
len = best_len;
pix_dist = best_pix_dist;
image_dist = best_image_dist;
#endif
/* update hash table */
UPDATE_HASH(encoder->dict, hval, seg_idx, anchor - ((PIXEL *)seg->lines));
if (!len) {
goto literal;
}
match: // RLE or dictionary (both are encoded by distance from ref (-1) and length)
#ifdef DEBUG_ENCODE
printf(", match(%zu, %zu, %zu)", image_dist, pix_dist, len);
n_encoded += len;
#endif
/* distance is biased */
if (!image_dist) {
pix_dist--;
}
/* if we have copied something, adjust the copy count */
if (copy) {
/* copy is biased, '0' means 1 byte copy */
update_copy_count(encoder, copy - 1);
} else {
/* back, to overwrite the copy count */
compress_output_prev(encoder);
}
/* reset literal counter */
copy = 0;
/* length is biased, '1' means a match of 3 pixels for PLT and alpha*/
/* for RGB 16 1 means 2 */
/* for RGB24/32 1 means 1...*/
ip = anchor + len - 2;
#if defined(LZ_RGB16)
len--;
#elif defined(LZ_PLT) || defined(LZ_RGB_ALPHA)
len -= 2;
#endif
GLZ_ASSERT(encoder->usr, len > 0);
encode_match(encoder, image_dist, pix_dist, len);
/* update the hash at match boundary */
#if defined(LZ_RGB16) || defined(LZ_RGB24) || defined(LZ_RGB32)
if (ip > anchor)
#endif
{
HASH_FUNC(hval, ip);
UPDATE_HASH(encoder->dict, hval, seg_idx, ip - ((PIXEL *)seg->lines));
}
ip++;
#if defined(LZ_RGB24) || defined(LZ_RGB32)
if (ip > anchor)
#endif
{
HASH_FUNC(hval, ip);
UPDATE_HASH(encoder->dict, hval, seg_idx, ip - ((PIXEL *)seg->lines));
}
ip++;
/* assuming literal copy */
encode_copy_count(encoder, MAX_COPY - 1);
continue;
literal:
#ifdef DEBUG_ENCODE
printf(", copy");
n_encoded++;
#endif
ENCODE_PIXEL(encoder, *anchor);
anchor++;
ip = anchor;
copy++;
if (LZ_UNEXPECT_CONDITIONAL(copy == MAX_COPY)) {
copy = 0;
encode_copy_count(encoder, MAX_COPY - 1);
}
} // END LOOP (ip < ip_limit)
/* left-over as literal copy */
ip_bound++;
while (ip <= ip_bound) {
#ifdef DEBUG_ENCODE
printf(", copy");
n_encoded++;
#endif
ENCODE_PIXEL(encoder, *ip);
ip++;
copy++;
if (copy == MAX_COPY) {
copy = 0;
encode_copy_count(encoder, MAX_COPY - 1);
}
}
/* if we have copied something, adjust the copy length */
if (copy) {
update_copy_count(encoder, copy - 1);
} else {
compress_output_prev(encoder);
}
#ifdef DEBUG_ENCODE
printf("\ntotal encoded=%d\n", n_encoded);
#endif
}
/* If the file is very small, copies it.
copies the first two pixels of the first segment, and sends the segments
one by one to compress_seg.
the number of bytes compressed are stored inside encoder. */
static void FNAME(compress)(Encoder *encoder)
{
uint32_t seg_id = encoder->cur_image.first_win_seg;
PIXEL *ip;
SharedDictionary *dict = encoder->dict;
int hval;
// fetch the first image segment that is not too small
while ((seg_id != NULL_IMAGE_SEG_ID) &&
(dict->window.segs[seg_id].image->id == encoder->cur_image.id) &&
((((PIXEL *)dict->window.segs[seg_id].lines_end) -
((PIXEL *)dict->window.segs[seg_id].lines)) < 4)) {
// coping the segment
if (dict->window.segs[seg_id].lines != dict->window.segs[seg_id].lines_end) {
ip = (PIXEL *)dict->window.segs[seg_id].lines;
// Note: we assume MAX_COPY > 3
encode_copy_count(encoder, (uint8_t)(
(((PIXEL *)dict->window.segs[seg_id].lines_end) -
((PIXEL *)dict->window.segs[seg_id].lines)) - 1));
while (ip < (PIXEL *)dict->window.segs[seg_id].lines_end) {
ENCODE_PIXEL(encoder, *ip);
ip++;
}
}
seg_id = dict->window.segs[seg_id].next;
}
if ((seg_id == NULL_IMAGE_SEG_ID) ||
(dict->window.segs[seg_id].image->id != encoder->cur_image.id)) {
return;
}
ip = (PIXEL *)dict->window.segs[seg_id].lines;
encode_copy_count(encoder, MAX_COPY - 1);
HASH_FUNC(hval, ip);
UPDATE_HASH(encoder->dict, hval, seg_id, 0);
ENCODE_PIXEL(encoder, *ip);
ip++;
ENCODE_PIXEL(encoder, *ip);
ip++;
#ifdef DEBUG_ENCODE
printf("copy, copy");
#endif
// compressing the first segment
FNAME(compress_seg)(encoder, seg_id, ip, 2);
// compressing the next segments
for (seg_id = dict->window.segs[seg_id].next;
seg_id != NULL_IMAGE_SEG_ID && (
dict->window.segs[seg_id].image->id == encoder->cur_image.id);
seg_id = dict->window.segs[seg_id].next) {
FNAME(compress_seg)(encoder, seg_id, (PIXEL *)dict->window.segs[seg_id].lines, 0);
}
}
#undef FNAME
#undef PIXEL_ID
#undef PIXEL_DIST
#undef PIXEL
#undef ENCODE_PIXEL
#undef SAME_PIXEL
#undef HASH_FUNC
#undef GET_rgb
#undef LZ_PLT
#undef LZ_RGB_ALPHA
#undef LZ_RGB16
#undef LZ_RGB24
#undef LZ_RGB32
#undef MIN_REF_ENCODE_SIZE
#undef MAX_REF_ENCODE_SIZE
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