shithub: libtags

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optional TOC handler

--- a/examples/readtags.c

+++ b/examples/readtags.c

@@ -38,7 +38,7 @@

 };

 static void

-cb(Tagctx *ctx, int t, const char *k, const char *v, int offset, int size, Tagread f)

+tag(Tagctx *ctx, int t, const char *k, const char *v, int offset, int size, Tagread f)

 {

 	USED(ctx); USED(k); USED(f);

 	if(t == Timage)

@@ -47,6 +47,12 @@

 		print("%-12s %s\n", t2s[t], v);

 }

+static void

+toc(Tagctx *ctx, int ms, int offset)

+{

+	USED(ctx); USED(ms); USED(offset);

+}

+

 static int

 ctxread(Tagctx *ctx, void *buf, int cnt)

 {

@@ -71,7 +77,8 @@

 	{

 		.read = ctxread,

 		.seek = ctxseek,

-		.tag = cb,

+		.tag = tag,

+		.toc = toc,

 		.buf = buf,

 		.bufsz = sizeof(buf),

 		.aux = &aux,

--- a/id3v2.c

+++ b/id3v2.c

@@ -294,10 +294,10 @@

 static void

 getduration(Tagctx *ctx, int offset)

 {

-	uvlong n, framelen, samplespf;

+	uvlong n, framelen, samplespf, toc;

 	uchar *b;

 	uint x;

-	int xversion, xlayer, xbitrate;

+	int xversion, xlayer, xbitrate, i;

 	if(ctx->read(ctx, ctx->buf, 256) != 256)

 		return;

@@ -330,10 +330,23 @@

 				if(ctx->duration == 0 && framelen > 0)

 					ctx->duration = n * samplespf * 1000 / framelen / ctx->samplerate;

-				if((x & 4) != 0){ /* TOC is set */

-					/* not doing anything yet */

+				if((x & 4) != 0 && ctx->toc != nil){ /* TOC is set */

+					toc = offset + 100 + (char*)b - ctx->buf;

+					if((x & 8) != 0) /* VBR scale */

+						toc += 4;

+					for(i = 0; i < 100; i++){

+						/*

+						 * offset = n * b[i] / 256

+						 * ms = i * duration / 100

+						 */

+						ctx->toc(ctx, i * ctx->duration / 100, toc + (n * b[i]) / 256);

+					}

+					b += 100;

+					if((x & 8) != 0) /* VBR scale */

+						b += 4;

 				}

 			}

+			offset += (char*)b - ctx->buf;

 		}else if(memcmp(&ctx->buf[0x24], "VBRI", 4) == 0){

 			n = beuint((uchar*)&ctx->buf[0x32]);

 			ctx->duration = n * samplespf * 1000 / ctx->samplerate;

--- a/tags.h

+++ b/tags.h

@@ -53,6 +53,9 @@

 	 */

 	void (*tag)(Tagctx *ctx, int type, const char *k, const char *s, int offset, int size, Tagread f);

+	/* Approximate millisecond-to-byte offsets within the file, if available. This callback is optional. */

+	void (*toc)(Tagctx *ctx, int ms, int offset);

+

 	/* Auxiliary data. Not used by libtags. */

 	void *aux;