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player: add some comments

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The code is horribly undocumented as is. Try to improve this by
adding some comments in the most important parts.
This commit is contained in:
Erik Faye-Lund 2011-01-25 21:02:47 +01:00
parent bc5fcca75f
commit 55f2508283
1 changed files with 12 additions and 1 deletions
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13
sync/track.c
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@ -36,16 +36,21 @@ static float key_ramp(const struct track_key k[2], double row)
float sync_get_val(const struct sync_track *t, double row) float sync_get_val(const struct sync_track *t, double row)
{ {
int idx, irow; int idx, irow;
/* If we have no keys at all, return a constant 0 */
if (!t->num_keys) if (!t->num_keys)
return 0.0f; return 0.0f;
irow = (int)floor(row); irow = (int)floor(row);
idx = key_idx_floor(t, irow); idx = key_idx_floor(t, irow);
/* at the edges, return the first/last value */
if (idx < 0) if (idx < 0)
return t->keys[0].value; return t->keys[0].value;
if (idx > (int)t->num_keys - 2) if (idx > (int)t->num_keys - 2)
return t->keys[t->num_keys - 1].value; return t->keys[t->num_keys - 1].value;
/* interpolate according to key-type */
switch (t->keys[idx].type) { switch (t->keys[idx].type) {
case KEY_STEP: case KEY_STEP:
return t->keys[idx].value; return t->keys[idx].value;
@ -64,6 +69,8 @@ float sync_get_val(const struct sync_track *t, double row)
int sync_find_key(const struct sync_track *t, int row) int sync_find_key(const struct sync_track *t, int row)
{ {
int lo = 0, hi = t->num_keys; int lo = 0, hi = t->num_keys;
/* binary search, t->keys is sorted by row */
while (lo < hi) { while (lo < hi) {
int mi = (lo + hi) / 2; int mi = (lo + hi) / 2;
assert(mi != hi); assert(mi != hi);
@ -73,8 +80,11 @@ int sync_find_key(const struct sync_track *t, int row)
else if (t->keys[mi].row > row) else if (t->keys[mi].row > row)
hi = mi; hi = mi;
else else
return mi; return mi; /* exact hit */
} }
assert(lo == hi);
/* return first key after row, negated and biased (to allow -0) */
return -lo - 1; return -lo - 1;
} }
@ -83,6 +93,7 @@ int sync_set_key(struct sync_track *t, const struct track_key *k)
{ {
int idx = sync_find_key(t, k->row); int idx = sync_find_key(t, k->row);
if (idx < 0) { if (idx < 0) {
/* no exact hit, we need to allocate a new key */
void *tmp; void *tmp;
idx = -idx - 1; idx = -idx - 1;
tmp = realloc(t->keys, sizeof(struct track_key) * tmp = realloc(t->keys, sizeof(struct track_key) *