static uint32_t correct_current_frame_number
(
lwlibav_video_decode_handler_t *vdhp,
AVPacket *pkt,
uint32_t i, /* frame_number */
uint32_t goal
)
{
#define MATCH_DTS( j ) (info[j].dts == pkt->dts)
#define MATCH_POS( j ) ((vdhp->lw_seek_flags & SEEK_POS_CORRECTION) && info[j].file_offset == pkt->pos)
order_converter_t *oc = vdhp->order_converter;
video_frame_info_t *info = vdhp->frame_list;
uint32_t p = oc ? oc[i].decoding_to_presentation : i;
if( pkt->dts == AV_NOPTS_VALUE || MATCH_DTS( p ) || MATCH_POS( p ) )
return i;
if( pkt->dts > info[p].dts )
{
/* too forward */
uint32_t limit = MIN( goal, vdhp->frame_count );
if( oc )
while( !MATCH_DTS( oc[++i].decoding_to_presentation )
&& !MATCH_POS( oc[ i].decoding_to_presentation )
&& i <= limit );
else
while( !MATCH_DTS( ++i )
&& !MATCH_POS( i )
&& i <= limit );
if( i > limit )
return 0;
}
else
{
/* too backward */
if( oc )
while( !MATCH_DTS( oc[--i].decoding_to_presentation )
&& !MATCH_POS( oc[ i].decoding_to_presentation )
&& i );
else
while( !MATCH_DTS( --i )
&& !MATCH_POS( i )
&& i );
if( i == 0 )
return 0;
}
return i;
#undef MATCH_DTS
#undef MATCH_POS
}
static Obj NFFUNCTION(Obj self, Obj rel, Obj dir, Obj word)
{
/* word is an integer lists. dir is true/false.
rel is a list of lists: square of positive relator+square of negative
relator; positions in 1st of letter i; position in 1st of letter -i
* if dir=true, replace all (>=1/2)-cyclic occurrences of rel in word by the shorter half
* if dir=false, replace all occurrences of the last generator in word by the corresponding bit of rel
*/
Obj posind = ELM_PLIST(rel,2), negind = ELM_PLIST(rel,3);
rel = ELM_PLIST(rel,1);
Int n = LEN_PLIST(posind), allocn = n, i = 0, resulti = 0, match = 0, matchlen = 0, j;
Obj result = ALLOC_PLIST(allocn);
while (i < LEN_PLIST(word)) {
/* we produced result[1..resulti] as the compressed version of word[1..i].
additionally, matchlen is maximal such that
rel[match..match+matchlen-1] = result[resulti-matchlen+1..resulti]
*/
i++;
Obj wi = ELM_PLIST(word,i);
Int vi = INT_INTOBJ(wi);
if (dir == False) {
if (vi == n) {
match = INT_INTOBJ(ELM_PLIST(negind,n));
for (j = 1; j < n; j++)
PUSH_LETTER(INT_INTOBJ(ELM_PLIST(rel,j+match)));
} else if (vi == -n) {
match = INT_INTOBJ(ELM_PLIST(posind,n));
for (j = 1; j < n; j++)
PUSH_LETTER(INT_INTOBJ(ELM_PLIST(rel,j+match)));
} else
PUSH_LETTER(vi);
} else {
if (resulti && vi == -INT_INTOBJ(ELM_PLIST(result,resulti))) {
/* pop letter, and update match */
resulti--;
matchlen--;
if (matchlen == 0 && resulti) {
MATCH_POS(match,INT_INTOBJ(ELM_PLIST(result,resulti)));
matchlen = 1;
while (resulti > matchlen && ELM_PLIST(result,resulti-matchlen) == ELM_PLIST(rel,match+n-1)) {
matchlen++;
if (!--match)
match = n;
}
} else
match = 0;
} else {
PUSH_LETTER(vi);
if (match && wi == ELM_PLIST(rel,match+matchlen)) {
matchlen++;
if (matchlen >= (n+1+(match < 2*n))/2) { /* more than half, or exactly half and negatives */
resulti -= matchlen;
for (j = n-1; j >= matchlen; j--)
PUSH_LETTER(-INT_INTOBJ(ELM_PLIST(rel,j+match)));
matchlen = n-matchlen;
match = 4*n+1 - (match+n-1);
}
} else {
matchlen = 1;
MATCH_POS(match,vi);
}
}
}
}
SET_LEN_PLIST(result,resulti);
return result;
}
