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[sixel] comment on requirement of 8 free qnodes per onode

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nick black 2022-01-08 08:25:10 -05:00 committed by nick black
parent 7abf93e166
commit 3375e9061c
1 changed files with 21 additions and 15 deletions
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36
src/lib/sixel.c
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@ -86,12 +86,14 @@ qidx(const qnode* q){
#define QNODECOUNT 1000
// create+zorch an array of QNODECOUNT qnodes. this is 12 bits per index
// (down from 24); we use 4/5/3 bits of the original 8/8/8 (see color_key()).
// in addition, at the end we allocate |colorregs| qnodes, to be used
// create+zorch an array of QNODECOUNT qnodes. this is 1000 entries covering
// 1000 sixel colors each (we pretend 100 doesn't exist, working on [0..99],
// heh). in addition, at the end we allocate |colorregs| qnodes, to be used
// dynamically in "fracturing". the original QNODECOUNT nodes are a static
// 5-level octree, flattened into an array; the latter are used as an actual
// octree.
// octree, flattened into an array; the latter are used as an actual octree.
// we must have 8 dynnodes available for every onode we create, or we can run
// into a situation where we don't have an available dynnode
// (see insert_color()).
static int
alloc_qstate(unsigned colorregs, qstate* qs){
qs->dynnodes_free = colorregs;
@ -99,7 +101,7 @@ alloc_qstate(unsigned colorregs, qstate* qs){
if((qs->qnodes = malloc((QNODECOUNT + qs->dynnodes_total) * sizeof(qnode))) == NULL){
return -1;
}
qs->onodes_free = colorregs / 8;
qs->onodes_free = qs->dynnodes_total / 8;
qs->onodes_total = qs->onodes_free;
if((qs->onodes = malloc(qs->onodes_total * sizeof(*qs->onodes))) == NULL){
free(qs->qnodes);
@ -124,7 +126,7 @@ free_qstate(qstate *qs){
}
// insert a color from the source image into the octree.
static void
static int
insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
const unsigned r = ncpixel_r(pixel);
const unsigned g = ncpixel_g(pixel);
@ -140,7 +142,7 @@ insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
q->q.comps[2] = b;
q->q.pop = 1;
++*colors;
return;
return 0;
}
onode* o;
// it's not a fractured node, but it's been used. check to see if we
@ -150,7 +152,7 @@ insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
qnode_keys(q->q.comps[0], q->q.comps[1], q->q.comps[2], &skeynat);
if(skey == skeynat){
++q->q.pop; // pretty good match
return;
return 0;
}
// we want to fracture. if we have no onodes, though, we can't.
// we also need at least one dynamic qnode. note that this means we might
@ -159,7 +161,7 @@ insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
if(qs->dynnodes_free == 0 || qs->onodes_free == 0){
//fprintf(stderr, "NO FREE ONES %u\n", key);
++q->q.pop; // not a great match, but we're already scattered
return;
return 0;
}
// get the next free onode and zorch it out
o = qs->onodes + qs->onodes_total - qs->onodes_free;
@ -182,14 +184,14 @@ insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
if(o->q[skey]){
// our subnode is already present, huzzah. increase its popcount.
++o->q[skey]->q.pop;
return;
return 0;
}
// we try otherwise to insert ourselves into o. this requires a free dynnode.
if(qs->dynnodes_free == 0){
//fprintf(stderr, "NO DYNFREE %u\n", key);
// FIXME won't find it in find_color() -- need to do something!
// whoops! no room in the inn, mother mary. throw this sample away.
return;
// this should never happen, because we always ought have 8 dynnodes for
// every possible onode.
return -1;
}
// get the next free dynnode and assign it to o, account for dnode
o->q[skey] = &qs->qnodes[QNODECOUNT + qs->dynnodes_total - qs->dynnodes_free];
@ -202,6 +204,7 @@ insert_color(qstate* qs, uint32_t pixel, uint32_t* colors){
o->q[skey]->cidx = 0;
++*colors;
//fprintf(stderr, "INSERTED[%u]: %u %u %u\n", key, q->q.comps[0], q->q.comps[1], q->q.comps[2]);
return 0;
}
// resolve the input color to a color table index following any postprocessing
@ -736,7 +739,10 @@ extract_color_table(const uint32_t* data, int linesize, int cols,
if(rgba_trans_p(*rgb, bargs->transcolor)){
continue;
}
insert_color(&qs, *rgb, &octets);
if(insert_color(&qs, *rgb, &octets)){
free_qstate(&qs);
return -1;
}
++pixels;
}
++pos;