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Fix slight FLAC seek inaccuracy e.g. when using 'trim' effect: further update

--- a/src/flac.c

+++ b/src/flac.c

@@ -58,6 +58,8 @@

   FLAC__StreamDecoder * decoder;

   FLAC__bool eof;

+  sox_bool seek_pending;

+  uint64_t seek_offset;

   /* Encode buffer: */

   FLAC__int32 * decoded_samples;

@@ -124,6 +126,7 @@

     return FLAC__STREAM_DECODER_WRITE_STATUS_ABORT;

   }

+  /* FIXME: We're skating on thin ice here: buffer may be on the stack! */

   p->decoded_wide_samples = buffer;

   p->number_of_wide_samples = frame->header.blocksize;

   p->wide_sample_number = 0;

@@ -194,12 +197,18 @@

   priv_t * p = (priv_t *)ft->priv;

   size_t actual = 0;

+  if (p->seek_pending) {

+    p->seek_pending = sox_false; 

+    p->wide_sample_number = p->number_of_wide_samples = 0;

+    if (!FLAC__stream_decoder_seek_absolute(p->decoder, (FLAC__uint64)(p->seek_offset / ft->signal.channels)))

+      return 0;

+  }

   while (!p->eof && actual < requested) {

     if (p->wide_sample_number >= p->number_of_wide_samples)

       FLAC__stream_decoder_process_single(p->decoder);

     if (p->wide_sample_number >= p->number_of_wide_samples)

       p->eof = sox_true;

-    else {

+    else { /* FIXME: this block should really be inside the decode callback */

       unsigned channel;

       for (channel = 0; channel < p->channels; channel++, actual++) {

@@ -484,9 +493,11 @@

 static int seek(sox_format_t * ft, uint64_t offset)

 {

   priv_t * p = (priv_t *)ft->priv;

-  p->wide_sample_number = p->number_of_wide_samples = 0;

-  return ft->mode == 'r' && FLAC__stream_decoder_seek_absolute(p->decoder, (FLAC__uint64)(offset / ft->signal.channels)) ?  SOX_SUCCESS : SOX_EOF;

+  p->seek_offset = offset;

+  p->seek_pending = sox_true;

+  return ft->mode == 'r' ? SOX_SUCCESS : SOX_EOF;

 }

+

 SOX_FORMAT_HANDLER(flac)