shithub: opusfile

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Small speed-up to op_bisect_forward_serialno().

Try to guess that the next link will be approximately the average
 size of all previous links, for files with many links.
This cuts off 6-17% of the seeks.

Also remove a variable that was left unused after 5e36109d.

--- a/src/opusfile.c

+++ b/src/opusfile.c

@@ -808,7 +808,6 @@

  const ogg_uint32_t *_serialnos,int _nserialnos,OggOpusLink *_link,

  ogg_int64_t _end_gp,ogg_uint32_t _end_serialno,opus_int64 _offset,

  ogg_int64_t *_total_duration){

-  opus_int64   offset;

   ogg_int64_t  total_duration;

   ogg_int64_t  duration;

   ogg_uint32_t cur_serialno;

@@ -889,6 +888,7 @@

   for(;;){

     opus_int64 data_offset;

     opus_int64 end_searched;

+    opus_int64 bisect;

     opus_int64 next;

     opus_int64 last;

     int        sri;

@@ -918,15 +918,32 @@

     end_searched=next=_sr[sri-1].offset;

     if(sri<nsr)_searched=_sr[sri].offset+_sr[sri].size;

     nsr=sri;

+    bisect=-1;

+    /*If we've already found the end of at least one link, try to pick the

+       first bisection point at twice the average link size.

+      This is a good choice for files with lots of links that are all about the

+       same size.*/

+    if(nlinks>1){

+      opus_int64 last_offset;

+      opus_int64 avg_link_size;

+      opus_int64 upper_limit;

+      last_offset=links[nlinks-1].offset;

+      avg_link_size=last_offset/(nlinks-1);

+      upper_limit=end_searched-OP_CHUNK_SIZE-avg_link_size;

+      if(OP_LIKELY(last_offset>_searched-avg_link_size)

+       &&OP_LIKELY(last_offset<upper_limit)){

+        bisect=last_offset+avg_link_size;

+        if(OP_LIKELY(bisect<upper_limit))bisect+=avg_link_size;

+      }

+    }

     /*We guard against garbage separating the last and first pages of two

        links below.*/

     while(_searched<end_searched){

-      opus_int64 bisect;

-      if(OP_UNLIKELY(end_searched-_searched<OP_CHUNK_SIZE))bisect=_searched;

       /*TODO: We might be able to do a better job estimating the start of

          subsequent links by assuming its initial PCM offset is 0 and using two

          sightings of the same stream to estimate a bitrate.*/

-      else bisect=_searched+(end_searched-_searched>>1);

+      if(bisect==-1)bisect=_searched+(end_searched-_searched>>1);

+      if(OP_UNLIKELY(bisect-_searched<OP_CHUNK_SIZE))bisect=_searched;

       ret=op_seek_helper(_of,bisect);

       if(OP_UNLIKELY(ret<0))return ret;

       last=op_get_next_page(_of,&og,_of->end);

@@ -947,6 +964,7 @@

         }

       }

       else _searched=_of->offset;

+      bisect=-1;

     }

     /*Bisection point found.

       Get the final granule position of the previous link, assuming