smokephil/ardour
1
0
Fork 0
mirror of https://github.com/Ardour/ardour.git synced 2026-01-02 11:49:33 +01:00
Code Issues Projects Releases Wiki Activity

libsmf: speed up ridiculous design of smf_save()

Browse source 
This would realloc a buffer for every event, making it absurdly slow for
large MIDI files (say, 10k events). Use the somewhat standard heuristic
of doubling the requested allocation every time we need to increase the size.

This results in a speedup of 40-100x when saving SMF to disk
This commit is contained in:
Paul Davis 2025-11-17 14:37:27 -07:00
parent 662d1b9e46
commit 65332e603b
2 changed files with 27 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

1
libs/evoral/libsmf/smf.h
View file

@ -244,6 +244,7 @@ struct smf_struct {
/** These are private fields using only by loading and saving routines. */
FILE *stream;
void *file_buffer;
size_t file_buffer_capacity;
size_t file_buffer_length;
size_t next_chunk_offset;
int expected_number_of_tracks;

41
libs/evoral/libsmf/smf_save.c
View file

@ -58,21 +58,32 @@ smf_extend(smf_t *smf, const int length)
int i, previous_file_buffer_length = smf->file_buffer_length;
char *previous_file_buffer = (char*)smf->file_buffer;
/* XXX: Not terribly efficient. */
smf->file_buffer_length += length;
smf->file_buffer = realloc(smf->file_buffer, smf->file_buffer_length);
if (smf->file_buffer == NULL) {
g_warning("realloc(3) failed: %s", strerror(errno));
smf->file_buffer_length = 0;
return (NULL);
}
if (smf->file_buffer_capacity >= smf->file_buffer_length + length) {
smf->file_buffer_length += length;
} else {
/* Fix up pointers. XXX: omgwtf. */
for (i = 1; i <= smf->number_of_tracks; i++) {
smf_track_t *track;
track = smf_get_track_by_number(smf, i);
if (track->file_buffer != NULL)
track->file_buffer = (char *)track->file_buffer + ((char *)smf->file_buffer - previous_file_buffer);
if (smf->file_buffer_capacity == 0) {
smf->file_buffer_capacity = length * 2;
} else {
smf->file_buffer_capacity *= 2;
}
smf->file_buffer = realloc(smf->file_buffer, smf->file_buffer_capacity);
if (smf->file_buffer == NULL) {
g_warning("realloc(3) failed: %s", strerror(errno));
smf->file_buffer_length = 0;
smf->file_buffer_capacity = 0;
return (NULL);
}
smf->file_buffer_length += length;
/* Fix up pointers. XXX: omgwtf. */
for (i = 1; i <= smf->number_of_tracks; i++) {
smf_track_t *track;
track = smf_get_track_by_number(smf, i);
if (track->file_buffer != NULL)
track->file_buffer = (char *)track->file_buffer + ((char *)smf->file_buffer - previous_file_buffer);
}
}
return ((char *)smf->file_buffer + previous_file_buffer_length);
@ -441,6 +452,7 @@ free_buffer(smf_t *smf)
free(smf->file_buffer);
smf->file_buffer = NULL;
smf->file_buffer_length = 0;
smf->file_buffer_capacity = 0;
for (i = 1; i <= smf->number_of_tracks; i++) {
track = smf_get_track_by_number(smf, i);
@ -681,4 +693,3 @@ smf_save(smf_t *smf, FILE* file)
return (0);
}