mp4: Simplify chunk_of_sample().

This function was unnecessarily complex. The equivalent replacement
code is much shorter and easier to read. Besides reducing the number
of local variables, we drop the chunk_sample parameter and return
this number via the return value of the function.

diff --git a/mp4.c b/mp4.c
index 1c20d89f27d28b5245095394eee52848fda1c8f0..71858305517cac98f2093050749dbadb1d0d94a1 100644 (file)
--- a/mp4.c
+++ b/mp4.c
@@ -981,46 +981,24 @@ void mp4_close(struct mp4 *f)
 }
 
 static int32_t chunk_of_sample(const struct mp4 *f, int32_t track,
-               int32_t sample, int32_t *chunk_sample, int32_t *chunk)
+               int32_t sample, int32_t *chunk)
 {
-       int32_t total_entries = 0;
-       int32_t chunk2entry;
-       int32_t chunk1, chunk2, chunk1samples, range_samples, total = 0;
-
-       *chunk_sample = 0;
-       *chunk = 1;
-
-       total_entries = f->track[track]->stsc_entry_count;
-
-       chunk1 = 1;
-       chunk1samples = 0;
-       chunk2entry = 0;
-
-       do {
-               chunk2 = f->track[track]->stsc_first_chunk[chunk2entry];
-               *chunk = chunk2 - chunk1;
-               range_samples = *chunk * chunk1samples;
+       const struct mp4_track *t = f->track[track];
+       uint32_t *fc = t->stsc_first_chunk, *spc = t->stsc_samples_per_chunk;
+       int32_t chunk1, chunk1samples, n, total, i;
 
-               if (sample < total + range_samples)
+       for (i = 1, total = 0; i < t->stsc_entry_count; i++, total += n) {
+               n = (fc[i] - fc[i - 1]) * spc[i - 1]; /* number of samples */
+               if (sample < total + n)
                        break;
-
-               chunk1samples = f->track[track]->stsc_samples_per_chunk[chunk2entry];
-               chunk1 = chunk2;
-
-               if (chunk2entry < total_entries) {
-                       chunk2entry++;
-                       total += range_samples;
-               }
-       } while (chunk2entry < total_entries);
-
-       if (chunk1samples)
+       }
+       chunk1 = fc[i - 1];
+       chunk1samples = spc[i - 1];
+       if (chunk1samples != 0)
                *chunk = (sample - total) / chunk1samples + chunk1;
        else
                *chunk = 1;
-
-       *chunk_sample = total + (*chunk - chunk1) * chunk1samples;
-
-       return 0;
+       return total + (*chunk - chunk1) * chunk1samples;
 }
 
 /**
@@ -1068,7 +1046,7 @@ int mp4_set_sample_position(struct mp4 *f, uint32_t track, int32_t sample)
 
        if (sample >= t->stsz_sample_count || track >= f->total_tracks)
                return -ERRNO_TO_PARA_ERROR(EINVAL);
-       chunk_of_sample(f, track, sample, &chunk_sample, &chunk);
+       chunk_sample = chunk_of_sample(f, track, sample, &chunk);
        if (t->stsz_sample_size > 0)
                srs = (sample - chunk_sample) * t->stsz_sample_size;
        else {