From 2403465b5af6a5f9d21106fa038f3aefe5fc3438 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thorbj=C3=B8rn=20Lindeijer?= <[EMAIL REDACTED]>
Date: Fri, 21 Feb 2025 11:20:28 +0100
Subject: [PATCH] stb_vorbis: Use a buffer to cache SDL_RWops reads
Requesting the data one byte at a time can be prohibitively expensive,
especially when the SDL_RWops isn't backed by constant memory but routed
through PhysicsFS for example.
This change introduces a 2kb buffer, which feels small enough to not add
too much overhead and is the same size as used by libvorbisfile. In my
measurements, using a larger buffer no longer made a significant
difference when starting to play an OGG file.
Testing with an uncompressed OGG file read from zip file, timing the
call to Mix_LoadMUS_RW:
* No buffer: ~ 47 ms
* 10 bytes: ~ 5.2 ms
* 100 bytes: ~ 1.1 ms
* 1 kb: ~ 0.62 ms
* 2 kb: ~ 0.6 ms
* 8 kb: ~ 0.58 ms
When using the libvorbisfile backend it takes about 0.2 ms.
(cherry picked from commit da1704a70ca94a866f87320f9e8126dd9f203e7d)
---
src/codecs/stb_vorbis/stb_vorbis.h | 75 ++++++++++++++++++++++++------
1 file changed, 61 insertions(+), 14 deletions(-)
diff --git a/src/codecs/stb_vorbis/stb_vorbis.h b/src/codecs/stb_vorbis/stb_vorbis.h
index c159a7c3..4b3c4900 100644
--- a/src/codecs/stb_vorbis/stb_vorbis.h
+++ b/src/codecs/stb_vorbis/stb_vorbis.h
@@ -308,6 +308,7 @@ extern stb_vorbis * stb_vorbis_open_file_section(FILE *f, int close_handle_on_cl
#ifdef STB_VORBIS_SDL
extern stb_vorbis * stb_vorbis_open_rwops_section(SDL_RWops *rwops, int close_on_free, int *error, const stb_vorbis_alloc *alloc, unsigned int length);
extern stb_vorbis * stb_vorbis_open_rwops(SDL_RWops *rwops, int close_on_free, int *error, const stb_vorbis_alloc *alloc);
+#define RWOPS_BUFFER_SIZE 2048
#endif
extern int stb_vorbis_seek_frame(stb_vorbis *f, unsigned int sample_number);
@@ -836,6 +837,10 @@ struct stb_vorbis
#ifdef STB_VORBIS_SDL
SDL_RWops *rwops;
uint32 rwops_start;
+ uint32 rwops_virtual_pos;
+ uint32 rwops_buffer_pos;
+ uint32 rwops_buffer_fill;
+ uint8 rwops_buffer[RWOPS_BUFFER_SIZE];
int close_on_free;
#endif
@@ -1400,9 +1405,13 @@ static int STBV_CDECL point_compare(const void *p, const void *q)
static uint8 get8(vorb *z)
{
#ifdef STB_VORBIS_SDL
- uint8 c;
- if (SDL_RWread(z->rwops, &c, 1, 1) != 1) { z->eof = TRUE; return 0; }
- return c;
+ if (z->rwops_buffer_pos >= z->rwops_buffer_fill) {
+ z->rwops_buffer_fill = SDL_RWread(z->rwops, z->rwops_buffer, 1, RWOPS_BUFFER_SIZE);
+ z->rwops_buffer_pos = 0;
+ if (z->rwops_buffer_fill == 0) { z->eof = TRUE; return 0; }
+ }
+ z->rwops_virtual_pos++;
+ return z->rwops_buffer[z->rwops_buffer_pos++];
#else
if (USE_MEMORY(z)) {
@@ -1433,9 +1442,28 @@ static uint32 get32(vorb *f)
static int getn(vorb *z, uint8 *data, int n)
{
#ifdef STB_VORBIS_SDL
- if (SDL_RWread(z->rwops, data, n, 1) == 1) return 1;
- z->eof = 1;
- return 0;
+ while (n > 0) {
+ int chunk;
+
+ if (z->rwops_buffer_pos >= z->rwops_buffer_fill) {
+ z->rwops_buffer_fill = SDL_RWread(z->rwops, z->rwops_buffer, 1, RWOPS_BUFFER_SIZE);
+ z->rwops_buffer_pos = 0;
+ if (z->rwops_buffer_fill == 0) {
+ z->eof = 1;
+ return 0;
+ }
+ }
+
+ chunk = z->rwops_buffer_fill - z->rwops_buffer_pos;
+ if (chunk > n) chunk = n;
+
+ memcpy(data, z->rwops_buffer + z->rwops_buffer_pos, chunk);
+ z->rwops_buffer_pos += chunk;
+ z->rwops_virtual_pos += chunk;
+ data += chunk;
+ n -= chunk;
+ }
+ return 1;
#else
if (USE_MEMORY(z)) {
@@ -1456,11 +1484,12 @@ static int getn(vorb *z, uint8 *data, int n)
#endif
}
+static int set_file_offset(stb_vorbis *f, unsigned int loc);
+
static void skip(vorb *z, int n)
{
#ifdef STB_VORBIS_SDL
- SDL_RWseek(z->rwops, n, RW_SEEK_CUR);
-
+ set_file_offset(z, z->rwops_virtual_pos + n);
#else
if (USE_MEMORY(z)) {
z->stream += n;
@@ -1485,17 +1514,31 @@ static int set_file_offset(stb_vorbis *f, unsigned int loc)
f->eof = 0;
#ifdef STB_VORBIS_SDL
- if (loc + f->rwops_start < loc || loc >= 0x80000000) {
- loc = 0x7fffffff;
+ { unsigned int rwops_pos;
+ uint32 buffer_start = f->rwops_virtual_pos - f->rwops_buffer_pos;
+ uint32 buffer_end = buffer_start + f->rwops_buffer_fill;
+ f->rwops_virtual_pos = loc;
+
+ // Move within buffer if possible
+ if (loc >= buffer_start && loc < buffer_end)
+ {
+ f->rwops_buffer_pos = loc - buffer_start;
+ return 1;
+ }
+
+ rwops_pos = loc + f->rwops_start;
+ if (rwops_pos < loc || loc >= 0x80000000) {
+ rwops_pos = 0x7fffffff;
f->eof = 1;
- } else {
- loc += f->rwops_start;
}
- if (SDL_RWseek(f->rwops, loc, RW_SEEK_SET) != -1)
+
+ f->rwops_buffer_pos = f->rwops_buffer_fill = 0; // Invalidate buffer
+ if (SDL_RWseek(f->rwops, rwops_pos, RW_SEEK_SET) != -1)
return 1;
f->eof = 1;
SDL_RWseek(f->rwops, f->rwops_start, RW_SEEK_END);
return 0;
+ }
#else
if (USE_MEMORY(f)) {
@@ -4440,6 +4483,10 @@ static void vorbis_init(stb_vorbis *p, const stb_vorbis_alloc *z)
#ifdef STB_VORBIS_SDL
p->close_on_free = FALSE;
p->rwops = NULL;
+ p->rwops_start = 0;
+ p->rwops_virtual_pos = 0;
+ p->rwops_buffer_pos = 0;
+ p->rwops_buffer_fill = 0;
#endif
#ifndef STB_VORBIS_NO_STDIO
p->close_on_free = FALSE;
@@ -4711,7 +4758,7 @@ unsigned int stb_vorbis_get_file_offset(stb_vorbis *f)
if (f->push_mode) return 0;
#endif
#ifdef STB_VORBIS_SDL
- return (unsigned int) (SDL_RWtell(f->rwops) - f->rwops_start);
+ return f->rwops_virtual_pos;
#else
if (USE_MEMORY(f)) return (unsigned int) (f->stream - f->stream_start);
#endif