Add libtags for extracting info from files

lib/libtags/437.c

@@ -0,0 +1,9 @@
+/* https://en.wikipedia.org/wiki/Code_page_437 */
+#include "tagspriv.h"
+
+int
+cp437toutf8(char *o, int osz, const char *s, int sz)
+{
+	/* FIXME somebody come up with portable code */
+	return snprint(o, osz, "%.*s", sz, s);
+}

lib/libtags/8859.c

@@ -0,0 +1,29 @@
+/* http://en.wikipedia.org/wiki/ISO/IEC_8859-1 */
+#include "tagspriv.h"
+
+int
+iso88591toutf8(uchar *o, int osz, const uchar *s, int sz)
+{
+	int i;
+
+	for(i = 0; i < sz && osz > 1 && s[i] != 0; i++){
+		if(s[i] >= 0xa0 && osz < 3)
+			break;
+
+		if(s[i] >= 0xc0){
+			*o++ = 0xc3;
+			*o++ = s[i] - 0x40;
+			osz--;
+		}else if(s[i] >= 0xa0){
+			*o++ = 0xc2;
+			*o++ = s[i];
+			osz--;
+		}else{
+			*o++ = s[i];
+		}
+		osz--;
+	}
+
+	*o = 0;
+	return i;
+}

lib/libtags/CMakeLists.txt

@@ -0,0 +1,5 @@
+idf_component_register(
+  SRCS 437.c 8859.c flac.c id3genres.c id3v1.c id3v2.c it.c m4a.c mod.c opus.c
+  s3m.c tags.c utf16.c vorbis.c wav.c xm.c
+  INCLUDE_DIRS .
+)

lib/libtags/LICENSE

@@ -0,0 +1,18 @@
+Copyright © 2013-2020 Sigrid Solveig Haflínudóttir
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

lib/libtags/README.md

@@ -0,0 +1,47 @@
+libtags
+=======
+
+A cross-platform library for reading tags, designed for highly constrained environments.
+
+Comparison to id3lib and taglib:
+
+|                | libtags         | id3lib           | taglib           |
+|:---------------|:----------------|:-----------------|:-----------------|
+| ID3v2.4        | yes             | no               | yes              |
+| Ogg/Vorbis     | yes             | no               | yes              |
+| FLAC           | yes             | no               | yes              |
+| m4a            | yes             | no               | yes              |
+| opus           | yes             | no               | yes              |
+| WAV            | yes             | no               | yes              |
+| IT             | yes             | no               | ???              |
+| XM             | yes             | no               | ???              |
+| S3M            | yes             | no               | ???              |
+| MOD            | yes             | no               | ???              |
+| replay gain    | yes             | no               | ???              |
+| size           | tiny            | bloated          | more bloated     |
+| license        | MIT             | LGPL             | LGPL/MPL         |
+| written in     | C               | C++              | C++              |
+| memory         | no allocations  | allocates memory | allocates memory |
+| thread safe    | yes             | ???              | ???              |
+| speed          | ultra-fast      | slow             | fast             |
+| tag writing    | no, not a goal  | yes              | yes              |
+| Plan 9 support | yes, native     | no               | no               |
+
+CPU time (784 files: mp3, ogg, flac):
+
+|                | libtags          | taglib           |
+|:---------------|:-----------------|:-----------------|
+| files cached   | real    0m0.027s | real    0m0.155s |
+|                | user    0m0.014s | user    0m0.102s |
+|                | sys     0m0.012s | sys     0m0.053s |
+|                |                  |                  |
+| cache dropped  | real    0m1.158s | real    0m1.628s |
+|                | user    0m0.024s | user    0m0.211s |
+|                | sys     0m0.132s | sys     0m0.187s |
+
+## Usage
+
+Just compile it to an archive (`.a`) and link to your program. Use it in your code
+by including `tags.h`, that's the API. Documentation is in the header.
+
+See `examples/readtags.c`. You can compile it on Linux like so: `gcc examples/readtags.c *.c -I. -o readtags`.

lib/libtags/examples/mkfile

@@ -0,0 +1,13 @@
+</$objtype/mkfile
+
+TARG=readtags
+
+OFILES=\
+	readtags.$O\
+	
+BIN=/$objtype/bin/audio
+
+HFILES=\
+	/sys/include/tags.h\
+
+</sys/src/cmd/mkone

lib/libtags/examples/readtags.c

@@ -0,0 +1,114 @@
+#ifdef __unix__
+#define _DEFAULT_SOURCE
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+#define print printf
+#define seek lseek
+#define nil NULL
+#define OREAD O_RDONLY
+#define USED(x) (void)x
+#else
+#include <u.h>
+#include <libc.h>
+#endif
+#include <tags.h>
+
+typedef struct Aux Aux;
+
+struct Aux
+{
+	int fd;
+};
+
+static const char *t2s[] =
+{
+	[Tartist] = "artist",
+	[Talbum] = "album",
+	[Ttitle] = "title",
+	[Tdate] = "date",
+	[Ttrack] = "track",
+	[Talbumgain] = "albumgain",
+	[Talbumpeak] = "albumpeak",
+	[Ttrackgain] = "trackgain",
+	[Ttrackpeak] = "trackpeak",
+	[Tgenre] = "genre",
+	[Timage] = "image",
+};
+
+static void
+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)
+		print("%-12s %s %d %d\n", t2s[t], v, offset, size);
+	else if(t != Tunknown)
+		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)
+{
+	Aux *aux = ctx->aux;
+	return read(aux->fd, buf, cnt);
+}
+
+static int
+ctxseek(Tagctx *ctx, int offset, int whence)
+{
+	Aux *aux = ctx->aux;
+	return seek(aux->fd, offset, whence);
+}
+
+int
+main(int argc, char **argv)
+{
+	int i;
+	char buf[256];
+	Aux aux;
+	Tagctx ctx =
+	{
+		.read = ctxread,
+		.seek = ctxseek,
+		.tag = tag,
+		.toc = toc,
+		.buf = buf,
+		.bufsz = sizeof(buf),
+		.aux = &aux,
+	};
+
+	if(argc < 2){
+		print("usage: readtags FILE...\n");
+		return -1;
+	}
+
+	for(i = 1; i < argc; i++){
+		print("*** %s\n", argv[i]);
+		if((aux.fd = open(argv[i], OREAD)) < 0)
+			print("failed to open\n");
+		else{
+			if(tagsget(&ctx) != 0)
+				print("no tags or failed to read tags\n");
+			else{
+				if(ctx.duration > 0)
+					print("%-12s %d ms\n", "duration", ctx.duration);
+				if(ctx.samplerate > 0)
+					print("%-12s %d\n", "samplerate", ctx.samplerate);
+				if(ctx.channels > 0)
+					print("%-12s %d\n", "channels", ctx.channels);
+				if(ctx.bitrate > 0)
+					print("%-12s %d\n", "bitrate", ctx.bitrate);
+			}
+			close(aux.fd);
+		}
+		print("\n");
+	}
+	return 0;
+}

lib/libtags/flac.c

@@ -0,0 +1,111 @@
+/* https://xiph.org/flac/format.html */
+#include "tagspriv.h"
+
+#define beu3(d) ((d)[0]<<16 | (d)[1]<<8 | (d)[2]<<0)
+
+int
+tagflac(Tagctx *ctx)
+{
+	uchar *d;
+	int sz, last;
+	uvlong g;
+
+	d = (uchar*)ctx->buf;
+	/* 8 bytes for marker, block type, length. 18 bytes for the stream info */
+	if(ctx->read(ctx, d, 8+18) != 8+18 || memcmp(d, "fLaC\x00", 5) != 0)
+		return -1;
+
+	sz = beu3(&d[5]); /* size of the stream info */
+	ctx->samplerate = beu3(&d[18]) >> 4;
+	ctx->channels = ((d[20]>>1) & 7) + 1;
+	if(ctx->samplerate < 1 || ctx->channels < 1)
+		return -1;
+
+	g = (uvlong)(d[21] & 0xf)<<32 | beu3(&d[22])<<8 | d[25];
+	ctx->duration = g * 1000 / ctx->samplerate;
+
+	/* skip the rest of the stream info */
+	if(ctx->seek(ctx, sz-18, 1) != ctx->restart+8+sz)
+		return -1;
+
+	for(last = 0; !last;){
+		if(ctx->read(ctx, d, 4) != 4)
+			return -1;
+
+		sz = beu3(&d[1]);
+		if((d[0] & 0x80) != 0)
+			last = 1;
+
+		if((d[0] & 0x7f) == 6){ /* 6 = picture */
+			int n, offset;
+			char *mime;
+
+			if(sz < 16 || ctx->read(ctx, d, 8) != 8) /* type, mime length */
+				return -1;
+			sz -= 8;
+			n = beuint(&d[4]);
+			mime = ctx->buf+20;
+			if(n >= sz || n >= ctx->bufsz-1 || ctx->read(ctx, mime, n) != n)
+				return -1;
+			sz -= n;
+			mime[n] = 0;
+			ctx->read(ctx, d, 4); /* description */
+			sz -= 4;
+			offset = beuint(d) + ctx->seek(ctx, 0, 1) + 20;
+			ctx->read(ctx, d, 20);
+			sz -= 20;
+			n = beuint(&d[16]);
+			tagscallcb(ctx, Timage, "", mime, offset, n, nil);
+			if(ctx->seek(ctx, sz, 1) <= 0)
+				return -1;
+		}else if((d[0] & 0x7f) == 4){ /* 4 = vorbis comment */
+			int i, numtags, tagsz, vensz;
+			char *k, *v;
+
+			if(sz < 12 || ctx->read(ctx, d, 4) != 4)
+				return -1;
+
+			sz -= 4;
+			vensz = leuint(d);
+			if(vensz < 0 || vensz > sz-4)
+				return -1;
+			/* skip vendor, read the number of tags */
+			if(ctx->seek(ctx, vensz, 1) < 0 || ctx->read(ctx, d, 4) != 4)
+				return -1;
+			sz -= vensz + 4;
+			numtags = leuint(d);
+
+			for(i = 0; i < numtags && sz > 4; i++){
+				if(ctx->read(ctx, d, 4) != 4)
+					return -1;
+				tagsz = leuint(d);
+				sz -= 4;
+				if(tagsz > sz)
+					return -1;
+
+				/* if it doesn't fit, ignore it */
+				if(tagsz+1 > ctx->bufsz){
+					if(ctx->seek(ctx, tagsz, 1) < 0)
+						return -1;
+					continue;
+				}
+
+				k = ctx->buf;
+				if(ctx->read(ctx, k, tagsz) != tagsz)
+					return -1;
+				/* some tags have a stupid '\r'; ignore */
+				if(k[tagsz-1] == '\r')
+					k[tagsz-1] = 0;
+				k[tagsz] = 0;
+
+				if((v = strchr(k, '=')) != nil){
+					*v++ = 0;
+					cbvorbiscomment(ctx, k, v);
+				}
+			}
+		}else if(ctx->seek(ctx, sz, 1) <= 0)
+			return -1;
+	}
+
+	return 0;
+}

lib/libtags/id3genres.c

@@ -0,0 +1,42 @@
+#include "tagspriv.h"
+
+const char *id3genres[Numgenre] =
+{
+	"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk",
+	"Grunge", "Hip-Hop", "Jazz", "Metal", "New Age", "Oldies",
+	"Other", "Pop", "Rhythm and Blues", "Rap", "Reggae", "Rock",
+	"Techno", "Industrial", "Alternative", "Ska", "Death Metal",
+	"Pranks", "Soundtrack", "Euro-Techno", "Ambient", "Trip-Hop",
+	"Vocal", "Jazz & Funk", "Fusion", "Trance", "Classical",
+	"Instrumental", "Acid", "House", "Game", "Sound Clip", "Gospel",
+	"Noise", "Alternative Rock", "Bass", "Soul", "Punk rock", "Space",
+	"Meditative", "Instrumental Pop", "Instrumental Rock", "Ethnic",
+	"Gothic", "Darkwave", "Techno-Industrial", "Electronic",
+	"Pop-Folk", "Eurodance", "Dream", "Southern Rock", "Comedy",
+	"Cult", "Gangsta", "Top 40", "Christian Rap", "Pop/Funk",
+	"Jungle", "Native American", "Cabaret", "New Wave", "Psychedelic",
+	"Rave", "Showtunes", "Trailer", "Lo-Fi", "Tribal", "Acid Punk",
+	"Acid Jazz", "Polka", "Retro", "Musical", "Rock & Roll", "Hard Rock",
+	"Folk", "Folk-Rock", "National Folk", "Swing", "Fast Fusion",
+	"Bebop", "Latin", "Revival", "Celtic", "Bluegrass", "Avantgarde",
+	"Gothic Rock", "Progressive Rock", "Psychedelic Rock", "Symphonic Rock",
+	"Slow Rock", "Big Band", "Chorus", "Easy Listening", "Acoustic",
+	"Humour", "Speech", "Chanson", "Opera", "Chamber Music", "Sonata",
+	"Symphony", "Booty Bass", "Primus", "Porn groove", "Satire", "Slow Jam",
+	"Club", "Tango", "Samba", "Folklore", "Ballad", "Power Ballad",
+	"Rhythmic Soul", "Freestyle", "Duet", "Punk rock", "Drum Solo", "A capella",
+	"Euro-House", "Dance Hall", "Goa Trance", "Drum & Bass",
+	"Club-House", "Hardcore Techno", "Terror", "Indie", "BritPop",
+	"Afro-punk", "Polsk Punk", "Beat", "Christian Gangsta Rap", "Heavy Metal",
+	"Black Metal", "Crossover", "Contemporary Christian", "Christian Rock",
+	"Merengue", "Salsa", "Thrash Metal", "Anime", "Jpop", "Synthpop",
+	"Abstract", "Art Rock", "Baroque", "Bhangra", "Big Beat",
+	"Breakbeat", "Chillout", "Downtempo", "Dub", "EBM", "Eclectic",
+	"Electro", "Electroclash", "Emo", "Experimental", "Garage",
+	"Global", "IDM", "Illbient", "Industro-Goth", "Jam Band",
+	"Krautrock", "Leftfield", "Lounge", "Math Rock", "New Romantic",
+	"Nu-Breakz", "Post-Punk", "Post-Rock", "Psytrance", "Shoegaze",
+	"Space Rock", "Trop Rock", "World Music", "Neoclassical",
+	"Audiobook", "Audio Theatre", "Neue Deutsche Welle", "Podcast",
+	"Indie Rock", "G-Funk", "Dubstep", "Garage Rock", "Psybient",
+};

lib/libtags/id3v1.c

@@ -0,0 +1,48 @@
+/*
+ * http://en.wikipedia.org/wiki/ID3
+ * Space-padded strings are mentioned there. This is wrong and is a lie.
+ */
+#include "tagspriv.h"
+
+enum
+{
+	Insz = 128,
+	Outsz = 61,
+};
+
+int
+tagid3v1(Tagctx *ctx)
+{
+	uchar *in, *out;
+
+	if(ctx->bufsz < Insz+Outsz)
+		return -1;
+	in = (uchar*)ctx->buf;
+	out = in + Insz;
+
+	if(ctx->seek(ctx, -Insz, 2) < 0)
+		return -1;
+	if(ctx->read(ctx, in, Insz) != Insz || memcmp(in, "TAG", 3) != 0)
+		return -1;
+
+	if((ctx->found & 1<<Ttitle) == 0 && iso88591toutf8(out, Outsz, &in[3], 30) > 0)
+		txtcb(ctx, Ttitle, "", out);
+	if((ctx->found & 1<<Tartist) == 0 && iso88591toutf8(out, Outsz, &in[33], 30) > 0)
+		txtcb(ctx, Tartist, "", out);
+	if((ctx->found & 1<<Talbum) == 0 && iso88591toutf8(out, Outsz, &in[63], 30) > 0)
+		txtcb(ctx, Talbum, "", out);
+
+	in[93+4] = 0;
+	if((ctx->found & 1<<Tdate) == 0 && in[93] != 0)
+		txtcb(ctx, Tdate, "", &in[93]);
+
+	if((ctx->found & 1<<Ttrack) == 0 && in[125] == 0 && in[126] > 0){
+		snprint((char*)out, Outsz, "%d", in[126]);
+		txtcb(ctx, Ttrack, "", out);
+	}
+
+	if((ctx->found & 1<<Tgenre) == 0 && in[127] < Numgenre)
+		txtcb(ctx, Tgenre, "", id3genres[in[127]]);
+
+	return 0;
+}

lib/libtags/id3v2.c

@@ -0,0 +1,479 @@
+/*
+ * Have fun reading the following:
+ *
+ * http://id3.org/id3v2.4.0-structure
+ * http://id3.org/id3v2.4.0-frames
+ * http://id3.org/d3v2.3.0
+ * http://id3.org/id3v2-00
+ * http://mpgedit.org/mpgedit/mpeg_format/mpeghdr.htm
+ * http://wiki.hydrogenaud.io/index.php?title=MP3#VBRI.2C_XING.2C_and_LAME_headers
+ * http://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header#VBRIHeader
+ */
+#include "tagspriv.h"
+
+#define synchsafe(d) (uint)(((d)[0]&127)<<21 | ((d)[1]&127)<<14 | ((d)[2]&127)<<7 | ((d)[3]&127)<<0)
+
+static int
+v2cb(Tagctx *ctx, char *k, char *v)
+{
+	k++;
+	if(strcmp(k, "AL") == 0 || strcmp(k, "ALB") == 0)
+		txtcb(ctx, Talbum, k-1, v);
+	else if(strcmp(k, "PE1") == 0 || strcmp(k, "PE2") == 0 || strcmp(k, "P1") == 0 || strcmp(k, "P2") == 0)
+		txtcb(ctx, Tartist, k-1, v);
+	else if(strcmp(k, "IT2") == 0 || strcmp(k, "T2") == 0)
+		txtcb(ctx, Ttitle, k-1, v);
+	else if(strcmp(k, "YE") == 0 || strcmp(k, "YER") == 0 || strcmp(k, "DRC") == 0)
+		txtcb(ctx, Tdate, k-1, v);
+	else if(strcmp(k, "RK") == 0 || strcmp(k, "RCK") == 0)
+		txtcb(ctx, Ttrack, k-1, v);
+	else if(strcmp(k, "LEN") == 0)
+		ctx->duration = atoi(v);
+	else if(strcmp(k, "CO") == 0 || strcmp(k, "CON") == 0){
+		for(; v[0]; v++){
+			if(v[0] == '(' && v[1] <= '9' && v[1] >= '0'){
+				int i = atoi(&v[1]);
+				if(i < Numgenre)
+					txtcb(ctx, Tgenre, k-1, id3genres[i]);
+				for(v++; v[0] && v[0] != ')'; v++);
+				v--;
+			}else if(v[0] != '(' && v[0] != ')'){
+				txtcb(ctx, Tgenre, k-1, v);
+				break;
+			}
+		}
+	}else if(strcmp(k, "XXX") == 0 && strncmp(v, "REPLAYGAIN_", 11) == 0){
+		int type = -1;
+		v += 11;
+		if(strncmp(v, "TRACK_", 6) == 0){
+			v += 6;
+			if(strcmp(v, "GAIN") == 0)
+				type = Ttrackgain;
+			else if(strcmp(v, "PEAK") == 0)
+				type = Ttrackpeak;
+		}else if(strncmp(v, "ALBUM_", 6) == 0){
+			v += 6;
+			if(strcmp(v, "GAIN") == 0)
+				type = Talbumgain;
+			else if(strcmp(v, "PEAK") == 0)
+				type = Talbumpeak;
+		}
+		if(type >= 0)
+			txtcb(ctx, type, k-1, v+5);
+		else
+			return 0;
+	}else{
+		txtcb(ctx, Tunknown, k-1, v);
+	}
+	return 1;
+}
+
+static int
+rva2(Tagctx *ctx, char *tag, int sz)
+{
+	uchar *b, *end;
+
+	if((b = memchr(tag, 0, sz)) == nil)
+		return -1;
+	b++;
+	for(end = (uchar*)tag+sz; b+4 < end; b += 5){
+		int type = b[0];
+		float peak;
+		float va = (float)(b[1]<<8 | b[2]) / 512.0f;
+
+		if(b[3] == 24){
+			peak = (float)(b[4]<<16 | b[5]<<8 | b[6]) / 32768.0f;
+			b += 2;
+		}else if(b[3] == 16){
+			peak = (float)(b[4]<<8 | b[5]) / 32768.0f;
+			b += 1;
+		}else if(b[3] == 8){
+			peak = (float)b[4] / 32768.0f;
+		}else
+			return -1;
+
+		if(type == 1){ /* master volume */
+			char vas[16], peaks[8];
+			snprint(vas, sizeof(vas), "%+.5f dB", va);
+			snprint(peaks, sizeof(peaks), "%.5f", peak);
+			vas[sizeof(vas)-1] = 0;
+			peaks[sizeof(peaks)-1] = 0;
+
+			if(strcmp((char*)tag, "track") == 0){
+				txtcb(ctx, Ttrackgain, "RVA2", vas);
+				txtcb(ctx, Ttrackpeak, "RVA2", peaks);
+			}else if(strcmp((char*)tag, "album") == 0){
+				txtcb(ctx, Talbumgain, "RVA2", vas);
+				txtcb(ctx, Talbumpeak, "RVA2", peaks);
+			}
+			break;
+		}
+	}
+	return 0;
+}
+
+static int
+resync(uchar *b, int sz)
+{
+	int i;
+
+	if(sz < 4)
+		return sz;
+	for(i = 0; i < sz-2; i++){
+		if(b[i] == 0xff && b[i+1] == 0x00 && (b[i+2] & 0xe0) == 0xe0){
+			memmove(&b[i+1], &b[i+2], sz-i-2);
+			sz--;
+		}
+	}
+	return sz;
+}
+
+static int
+unsyncread(void *buf, int *sz)
+{
+	int i;
+	uchar *b;
+
+	b = buf;
+	for(i = 0; i < *sz; i++){
+		if(b[i] == 0xff){
+			if(i+1 >= *sz || (b[i+1] == 0x00 && i+2 >= *sz))
+				break;
+			if(b[i+1] == 0x00 && (b[i+2] & 0xe0) == 0xe0){
+				memmove(&b[i+1], &b[i+2], *sz-i-2);
+				(*sz)--;
+			}
+		}
+	}
+	return i;
+}
+
+static int
+nontext(Tagctx *ctx, uchar *d, int tsz, int unsync)
+{
+	int n, offset;
+	char *b, *tag;
+	Tagread f;
+
+	tag = ctx->buf;
+	n = 0;
+	f = unsync ? unsyncread : nil;
+	if(strcmp((char*)d, "APIC") == 0){
+		offset = ctx->seek(ctx, 0, 1);
+		if((n = ctx->read(ctx, tag, 256)) == 256){ /* APIC mime and description should fit */
+			b = tag + 1; /* mime type */
+			for(n = 1 + strlen(b) + 2; n < 253; n++){
+				if(tag[0] == 0 || tag[0] == 3){ /* one zero byte */
+					if(tag[n] == 0){
+						n++;
+						break;
+					}
+				}else if(tag[n] == 0 && tag[n+1] == 0 && tag[n+2] == 0){
+					n += 3;
+					break;
+				}
+			}
+			tagscallcb(ctx, Timage, "APIC", b, offset+n, tsz-n, f);
+			n = 256;
+		}
+	}else if(strcmp((char*)d, "PIC") == 0){
+		offset = ctx->seek(ctx, 0, 1);
+		if((n = ctx->read(ctx, tag, 256)) == 256){ /* PIC description should fit */
+			b = tag + 1; /* mime type */
+			for(n = 5; n < 253; n++){
+				if(tag[0] == 0 || tag[0] == 3){ /* one zero byte */
+					if(tag[n] == 0){
+						n++;
+						break;
+					}
+				}else if(tag[n] == 0 && tag[n+1] == 0 && tag[n+2] == 0){
+					n += 3;
+					break;
+				}
+			}
+			tagscallcb(ctx, Timage, "PIC", strcmp(b, "JPG") == 0 ? "image/jpeg" : "image/png", offset+n, tsz-n, f);
+			n = 256;
+		}
+	}else if(strcmp((char*)d, "RVA2") == 0 && tsz >= 6+5){
+		/* replay gain. 6 = "track\0", 5 = other */
+		if(ctx->bufsz >= tsz && (n = ctx->read(ctx, tag, tsz)) == tsz)
+			rva2(ctx, tag, unsync ? resync((uchar*)tag, n) : n);
+	}
+
+	return ctx->seek(ctx, tsz-n, 1) < 0 ? -1 : 0;
+}
+
+static int
+text(Tagctx *ctx, uchar *d, int tsz, int unsync)
+{
+	char *b, *tag;
+
+	if(ctx->bufsz >= tsz+1){
+		/* place the data at the end to make best effort at charset conversion */
+		tag = &ctx->buf[ctx->bufsz - tsz - 1];
+		if(ctx->read(ctx, tag, tsz) != tsz)
+			return -1;
+	}else{
+		ctx->seek(ctx, tsz, 1);
+		return 0;
+	}
+
+	if(unsync)
+		tsz = resync((uchar*)tag, tsz);
+
+	tag[tsz] = 0;
+	b = &tag[1];
+
+	switch(tag[0]){
+	case 0: /* iso-8859-1 */
+		if(iso88591toutf8((uchar*)ctx->buf, ctx->bufsz, (uchar*)b, tsz) > 0)
+			v2cb(ctx, (char*)d, ctx->buf);
+		break;
+	case 1: /* utf-16 */
+	case 2:
+		if(utf16to8((uchar*)ctx->buf, ctx->bufsz, (uchar*)b, tsz) > 0)
+			v2cb(ctx, (char*)d, ctx->buf);
+		break;
+	case 3: /* utf-8 */
+		if(*b)
+			v2cb(ctx, (char*)d, b);
+		break;
+	}
+
+	return 0;
+}
+
+static int
+isid3(uchar *d)
+{
+	/* "ID3" version[2] flags[1] size[4] */
+	return (
+		d[0] == 'I' && d[1] == 'D' && d[2] == '3' &&
+		d[3] < 0xff && d[4] < 0xff &&
+		d[6] < 0x80 && d[7] < 0x80 && d[8] < 0x80 && d[9] < 0x80
+	);
+}
+
+static const uchar bitrates[4][4][16] = {
+	{
+		{0},
+		{0,  4,  8, 12, 16, 20, 24, 28, 32, 40, 48, 56, 64,  72,  80, 0}, /* v2.5 III */
+		{0,  4,  8, 12, 16, 20, 24, 28, 32, 40, 48, 56, 64,  72,  80, 0}, /* v2.5 II */
+		{0, 16, 24, 28, 32, 40, 48, 56, 64, 72, 80, 88, 96, 112, 128, 0}, /* v2.5 I */
+	},
+	{ {0}, {0}, {0}, {0} },
+	{
+		{0},
+		{0,  4,  8, 12, 16, 20, 24, 28, 32, 40, 48, 56, 64,  72,  80, 0}, /* v2 III */
+		{0,  4,  8, 12, 16, 20, 24, 28, 32, 40, 48, 56, 64,  72,  80, 0}, /* v2 II */
+		{0, 16, 24, 28, 32, 40, 48, 56, 64, 72, 80, 88, 96, 112, 128, 0}, /* v2 I */
+	},
+	{
+		{0},
+		{0, 16, 20, 24, 28, 32, 40,  48,  56,  64,  80,  96, 112, 128, 160, 0}, /* v1 III */
+		{0, 16, 24, 28, 32, 40, 48,  56,  64,  80,  96, 112, 128, 160, 192, 0}, /* v1 II */
+		{0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 0}, /* v1 I */
+	}
+};
+
+static const uint samplerates[4][4] = {
+	{11025, 12000,  8000, 0},
+	{    0,     0,     0, 0},
+	{22050, 24000, 16000, 0},
+	{44100, 48000, 32000, 0},
+};
+
+static const int chans[] = {2, 2, 2, 1};
+
+static const int samplesframe[4][4] = {
+	{0,    0,    0,   0},
+	{0,  576, 1152, 384},
+	{0,  576, 1152, 384},
+	{0, 1152, 1152, 384},
+};
+
+static void
+getduration(Tagctx *ctx, int offset)
+{
+	uvlong n, framelen, samplespf, toc;
+	uchar *b;
+	uint x;
+	int xversion, xlayer, xbitrate, i;
+
+	if(ctx->read(ctx, ctx->buf, 256) != 256)
+		return;
+
+	x = beuint((uchar*)ctx->buf);
+	xversion = x >> 19 & 3;
+	xlayer = x >> 17 & 3;
+	xbitrate = x >> 12 & 0xf;
+	ctx->bitrate = 2000*(int)bitrates[xversion][xlayer][xbitrate];
+	samplespf = samplesframe[xversion][xlayer];
+
+	ctx->samplerate = samplerates[xversion][x >> 10 & 3];
+	ctx->channels = chans[x >> 6 & 3];
+
+	if(ctx->samplerate > 0){
+		framelen = (uvlong)144*ctx->bitrate / ctx->samplerate;
+		if((x & (1<<9)) != 0) /* padding */
+			framelen += xlayer == 3 ? 4 : 1; /* for I it's 4 bytes */
+
+		if(memcmp(&ctx->buf[0x24], "Info", 4) == 0 || memcmp(&ctx->buf[0x24], "Xing", 4) == 0){
+			b = (uchar*)ctx->buf + 0x28;
+			x = beuint(b); b += 4;
+			if((x & 1) != 0){ /* number of frames is set */
+				n = beuint(b); b += 4;
+				ctx->duration = n * samplespf * 1000 / ctx->samplerate;
+			}
+
+			if((x & 2) != 0){ /* file size is set */
+				n = beuint(b); b += 4;
+				if(ctx->duration == 0 && framelen > 0)
+					ctx->duration = n * samplespf * 1000 / framelen / ctx->samplerate;
+
+				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;
+
+			if(ctx->duration == 0 && framelen > 0){
+				n = beuint((uchar*)&ctx->buf[0x28]); /* file size */
+				ctx->duration = n * samplespf * 1000 / framelen / ctx->samplerate;
+			}
+		}
+	}
+
+	if(ctx->bitrate > 0 && ctx->duration == 0) /* worst case -- use real file size instead */
+		ctx->duration = (ctx->seek(ctx, 0, 2) - offset)/(ctx->bitrate / 1000) * 8;
+}
+
+int
+tagid3v2(Tagctx *ctx)
+{
+	int sz, exsz, framesz;
+	int ver, unsync, offset;
+	int newpos, oldpos;
+	uchar d[10], *b;
+
+	if(ctx->read(ctx, d, sizeof(d)) != sizeof(d))
+		return -1;
+	if(!isid3(d)){ /* no tags, but the stream information is there */
+		if(d[0] != 0xff || (d[1] & 0xfe) != 0xfa)
+			return -1;
+		ctx->seek(ctx, -(int)sizeof(d), 1);
+		getduration(ctx, 0);
+		return 0;
+	}
+
+	oldpos = 0;
+header:
+	ver = d[3];
+	unsync = d[5] & (1<<7);
+	sz = synchsafe(&d[6]);
+
+	if(ver == 2 && (d[5] & (1<<6)) != 0) /* compression */
+		return -1;
+
+	ctx->restart = sizeof(d)+sz;
+
+	if(ver > 2){
+		if((d[5] & (1<<4)) != 0) /* footer */
+			sz -= 10;
+		if((d[5] & (1<<6)) != 0){ /* skip extended header */
+			if(ctx->read(ctx, d, 4) != 4)
+				return -1;
+			exsz = (ver >= 3) ? beuint(d) : synchsafe(d);
+			if(ctx->seek(ctx, exsz, 1) < 0)
+				return -1;
+			sz -= exsz;
+		}
+	}
+
+	framesz = (ver >= 3) ? 10 : 6;
+	for(; sz > framesz;){
+		int tsz, frameunsync;
+
+		if(ctx->read(ctx, d, framesz) != framesz)
+			return -1;
+		sz -= framesz;
+
+		/* return on padding */
+		if(memcmp(d, "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", framesz) == 0)
+			break;
+		if(ver >= 3){
+			tsz = (ver == 3) ? beuint(&d[4]) : synchsafe(&d[4]);
+			if(tsz < 0 || tsz > sz)
+				break;
+			frameunsync = d[9] & (1<<1);
+			d[4] = 0;
+
+			if((d[9] & 0x0c) != 0){ /* compression & encryption */
+				ctx->seek(ctx, tsz, 1);
+				sz -= tsz;
+				continue;
+			}
+			if(ver == 4 && (d[9] & 1<<0) != 0){ /* skip data length indicator */
+				ctx->seek(ctx, 4, 1);
+				sz -= 4;
+				tsz -= 4;
+			}
+		}else{
+			tsz = beuint(&d[3]) >> 8;
+			if(tsz > sz)
+				return -1;
+			frameunsync = 0;
+			d[3] = 0;
+		}
+		sz -= tsz;
+
+		if(d[0] == 'T' && text(ctx, d, tsz, unsync || frameunsync) != 0)
+			return -1;
+		else if(d[0] != 'T' && nontext(ctx, d, tsz, unsync || frameunsync) != 0)
+			return -1;
+	}
+
+	offset = ctx->seek(ctx, sz, 1);
+	sz = ctx->bufsz <= 2048 ? ctx->bufsz : 2048;
+	b = nil;
+	for(exsz = 0; exsz < 2048; exsz += sz){
+		if(ctx->read(ctx, ctx->buf, sz) != sz)
+			break;
+		for(b = (uchar*)ctx->buf; (b = memchr(b, 'I', sz - 1 - ((char*)b - ctx->buf))) != nil; b++){
+			newpos = ctx->seek(ctx, (char*)b - ctx->buf + offset + exsz, 0);
+			if(ctx->read(ctx, d, sizeof(d)) != sizeof(d))
+				return 0;
+			if(isid3(d) && newpos != oldpos){
+				oldpos = newpos;
+				goto header;
+			}
+		}
+		for(b = (uchar*)ctx->buf; (b = memchr(b, 0xff, sz-3)) != nil; b++){
+			if((b[1] & 0xe0) == 0xe0){
+				offset = ctx->seek(ctx, (char*)b - ctx->buf + offset + exsz, 0);
+				exsz = 2048;
+				break;
+			}
+		}
+	}
+
+	if(b != nil)
+		getduration(ctx, offset);
+
+	return 0;
+}

lib/libtags/it.c

@@ -0,0 +1,15 @@
+#include "tagspriv.h"
+
+int
+tagit(Tagctx *ctx)
+{
+	uchar d[4+26+1], o[26*2+1];
+
+	if(ctx->read(ctx, d, 4+26) != 4+26 || memcmp(d, "IMPM", 4) != 0)
+		return -1;
+	d[4+26] = 0;
+	if(iso88591toutf8(o, sizeof(o), d+4, 26) > 0)
+		txtcb(ctx, Ttitle, "", o);
+
+	return 0;
+}

lib/libtags/m4a.c

@@ -0,0 +1,157 @@
+/* http://wiki.multimedia.cx/?title=QuickTime_container */
+/* https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFChap2/qtff2.html */
+#include "tagspriv.h"
+
+#define beuint16(d) (ushort)((d)[0]<<8 | (d)[1]<<0)
+
+int
+tagm4a(Tagctx *ctx)
+{
+	uvlong duration;
+	uint x;
+	uchar *d;
+	int sz, type, dtype, i, skip, n;
+
+	d = (uchar*)ctx->buf;
+	/* 4 bytes for atom size, 4 for type, 4 for data - exect "ftyp" to come first */
+	if(ctx->read(ctx, d, 4+4+4) != 4+4+4 || memcmp(d+4, "ftypM4A ", 8) != 0)
+		return -1;
+	sz = beuint(d) - 4; /* already have 8 bytes */
+
+	for(;;){
+		if(ctx->seek(ctx, sz, 1) < 0)
+			return -1;
+		if(ctx->read(ctx, d, 4) != 4) /* size */
+			break;
+		sz = beuint(d);
+		if(sz == 0)
+			continue;
+		if(ctx->read(ctx, d, 4) != 4) /* type */
+			return -1;
+		if(sz < 8)
+			continue;
+
+		d[4] = 0;
+
+		if(memcmp(d, "meta", 4) == 0){
+			sz = 4;
+			continue;
+		}else if(
+			memcmp(d, "udta", 4) == 0 ||
+			memcmp(d, "ilst", 4) == 0 ||
+			memcmp(d, "trak", 4) == 0 ||
+			memcmp(d, "mdia", 4) == 0 ||
+			memcmp(d, "minf", 4) == 0 ||
+			memcmp(d, "moov", 4) == 0 ||
+			memcmp(d, "trak", 4) == 0 ||
+			memcmp(d, "stbl", 4) == 0){
+			sz = 0;
+			continue;
+		}else if(memcmp(d, "stsd", 4) == 0){
+			sz -= 8;
+			if(ctx->read(ctx, d, 8) != 8)
+				return -1;
+			sz -= 8;
+
+			for(i = beuint(&d[4]); i > 0 && sz > 0; i--){
+				if(ctx->read(ctx, d, 8) != 8) /* size + format */
+					return -1;
+				sz -= 8;
+				skip = beuint(d) - 8;
+
+				if(memcmp(&d[4], "mp4a", 4) == 0){ /* audio */
+					n = 6+2 + 2+4+2 + 2+2 + 2+2 + 4; /* read a bunch at once */
+					/* reserved+id, ver+rev+vendor, channels+bps, ?+?, sample rate */
+					if(ctx->read(ctx, d, n) != n)
+						return -1;
+					skip -= n;
+					sz -= n;
+					ctx->channels = beuint16(&d[16]);
+					ctx->samplerate = beuint(&d[24])>>16;
+				}
+
+				if(ctx->seek(ctx, skip, 1) < 0)
+					return -1;
+				sz -= skip;
+			}
+			continue;
+		}
+
+		sz -= 8;
+		type = -1;
+		if(memcmp(d, "\251nam", 4) == 0)
+			type = Ttitle;
+		else if(memcmp(d, "\251alb", 4) == 0)
+			type = Talbum;
+		else if(memcmp(d, "\251ART", 4) == 0)
+			type = Tartist;
+		else if(memcmp(d, "\251gen", 4) == 0 || memcmp(d, "gnre", 4) == 0)
+			type = Tgenre;
+		else if(memcmp(d, "\251day", 4) == 0)
+			type = Tdate;
+		else if(memcmp(d, "covr", 4) == 0)
+			type = Timage;
+		else if(memcmp(d, "trkn", 4) == 0)
+			type = Ttrack;
+		else if(memcmp(d, "mdhd", 4) == 0){
+			if(ctx->read(ctx, d, 4) != 4)
+				return -1;
+			sz -= 4;
+			duration = 0;
+			if(d[0] == 0){ /* version 0 */
+				if(ctx->read(ctx, d, 16) != 16)
+					return -1;
+				sz -= 16;
+				if((x = beuint(&d[8])) > 0)
+					duration = beuint(&d[12]) / x;
+			}else if(d[1] == 1){ /* version 1 */
+				if(ctx->read(ctx, d, 28) != 28)
+					return -1;
+				sz -= 28;
+				if((x = beuint(&d[16])) > 0)
+					duration = ((uvlong)beuint(&d[20])<<32 | beuint(&d[24])) / (uvlong)x;
+			}
+			ctx->duration = duration * 1000;
+			continue;
+		}
+
+		if(type < 0)
+			continue;
+
+		if(ctx->seek(ctx, 8, 1) < 0) /* skip size and "data" */
+			return -1;
+		sz -= 8;
+		if(ctx->read(ctx, d, 8) != 8) /* read data type and 4 bytes of whatever else */
+			return -1;
+		sz -= 8;
+		d[0] = 0;
+		dtype = beuint(d);
+
+		if(type == Ttrack){
+			if(ctx->read(ctx, d, 4) != 4)
+				return -1;
+			sz -= 4;
+			snprint((char*)d, ctx->bufsz, "%d", beuint(d));
+			txtcb(ctx, type, "", d);
+		}else if(type == Tgenre){
+			if(ctx->read(ctx, d, 2) != 2)
+				return -1;
+			sz -= 2;
+			if((i = d[1]-1) >= 0 && i < Numgenre)
+				txtcb(ctx, type, "", id3genres[i]);
+		}else if(dtype == 1){ /* text */
+			if(sz >= ctx->bufsz) /* skip tags that can't fit into memory. ">=" because of '\0' */
+				continue;
+			if(ctx->read(ctx, d, sz) != sz)
+				return -1;
+			d[sz] = 0;
+			txtcb(ctx, type, "", d);
+			sz = 0;
+		}else if(type == Timage && dtype == 13) /* jpeg cover image */
+			tagscallcb(ctx, Timage, "", "image/jpeg", ctx->seek(ctx, 0, 1), sz, nil);
+		else if(type == Timage && dtype == 14) /* png cover image */
+			tagscallcb(ctx, Timage, "", "image/png", ctx->seek(ctx, 0, 1), sz, nil);
+	}
+
+	return 0;
+}

lib/libtags/mkfile

@@ -0,0 +1,29 @@
+</$objtype/mkfile
+LIB=/$objtype/lib/libtags.a
+
+OFILES=\
+	437.$O\
+	8859.$O\
+	flac.$O\
+	id3genres.$O\
+	id3v1.$O\
+	id3v2.$O\
+	it.$O\
+	m4a.$O\
+	opus.$O\
+	s3m.$O\
+	tags.$O\
+	utf16.$O\
+	vorbis.$O\
+	wav.$O\
+	xm.$O\
+	mod.$O\
+
+HFILES=\
+	/sys/include/tags.h\
+	tagspriv.h\
+
+/sys/include/%.h: %.h
+	cp $stem.h /sys/include/$stem.h
+
+</sys/src/cmd/mksyslib

lib/libtags/mod.c

@@ -0,0 +1,49 @@
+#include "tagspriv.h"
+
+/* insane. */
+static char *variants[] =
+{
+	"M.K.",
+	"M!K!",
+	"M&K!",
+	"N.T.",
+	"NSMS",
+	"FLT4",
+	"M\0\0\0",
+	"8\0\0\0",
+	"FEST",
+	"FLT8",
+	"CD81",
+	"OCTA",
+	"OKTA",
+	"10CH",
+	"16CN",
+	"32CN",
+	nil,
+};
+
+int
+tagmod(Tagctx *ctx)
+{
+	uchar d[20], o[20*2+1];
+	int i;
+
+	if(ctx->seek(ctx, 1080, 0) != 1080)
+		return -1;
+	if(ctx->read(ctx, d, 4) != 4)
+		return -1;
+	for(i = 0; ; i++){
+		if(variants[i] == nil)
+			return -1;
+		if(memcmp(d, variants[i], 4) == 0)
+			break;
+	}
+	if(ctx->seek(ctx, 0, 0) != 0)
+		return -1;
+	if(ctx->read(ctx, d, 20) != 20)
+		return -1;
+	if(iso88591toutf8(o, sizeof(o), d, 20) > 0)
+		txtcb(ctx, Ttitle, "", o);
+
+	return 0;
+}

lib/libtags/opus.c

@@ -0,0 +1,96 @@
+#include "tagspriv.h"
+
+int
+tagopus(Tagctx *ctx)
+{
+	char *v;
+	uchar *d, h[4];
+	int sz, numtags, i, npages, pgend;
+
+	d = (uchar*)ctx->buf;
+	for(npages = pgend = 0; npages < 2; npages++){
+		int nsegs;
+		if(ctx->read(ctx, d, 27) != 27)
+			return -1;
+		if(memcmp(d, "OggS", 4) != 0)
+			return -1;
+
+		/* calculate the size of the packet */
+		nsegs = d[26];
+		if(ctx->read(ctx, d, nsegs+8) != nsegs+8)
+			return -1;
+		for(sz = i = 0; i < nsegs; sz += d[i++]);
+
+		if(memcmp(&d[nsegs], "OpusHead", 8) == 0){
+			if(ctx->read(ctx, d, 8) != 8 || d[0] != 1)
+				return -1;
+			sz -= 8;
+			ctx->channels = d[1];
+			ctx->samplerate = leuint(&d[4]);
+		}else if(memcmp(&d[nsegs], "OpusTags", 8) == 0){
+			/* FIXME - embedded pics make tags span multiple packets */
+			pgend = ctx->seek(ctx, 0, 1) + sz;
+			break;
+		}
+
+		ctx->seek(ctx, sz-8, 1);
+	}
+
+	if(npages < 3){
+		if(ctx->read(ctx, d, 4) != 4)
+			return -1;
+		sz = leuint(d);
+		if(ctx->seek(ctx, sz, 1) < 0 || ctx->read(ctx, h, 4) != 4)
+			return -1;
+		numtags = leuint(h);
+
+		for(i = 0; i < numtags; i++){
+			if(ctx->read(ctx, h, 4) != 4)
+				return -1;
+			if((sz = leuint(h)) < 0)
+				return -1;
+			/* FIXME - embedded pics make tags span multiple packets */
+			if(pgend < ctx->seek(ctx, 0, 1)+sz)
+				break;
+
+			if(ctx->bufsz < sz+1){
+				if(ctx->seek(ctx, sz, 1) < 0)
+					return -1;
+				continue;
+			}
+			if(ctx->read(ctx, ctx->buf, sz) != sz)
+				return -1;
+			ctx->buf[sz] = 0;
+
+			if((v = strchr(ctx->buf, '=')) == nil)
+				return -1;
+			*v++ = 0;
+			cbvorbiscomment(ctx, ctx->buf, v);
+		}
+	}
+
+	/* calculate the duration */
+	if(ctx->samplerate > 0){
+		sz = ctx->bufsz <= 4096 ? ctx->bufsz : 4096;
+		for(i = sz; i < 65536+16; i += sz - 16){
+			if(ctx->seek(ctx, -i, 2) <= 0)
+				break;
+			v = ctx->buf;
+			if(ctx->read(ctx, v, sz) != sz)
+				break;
+			for(; v != nil && v < ctx->buf+sz;){
+				v = memchr(v, 'O', ctx->buf+sz - v - 14);
+				if(v != nil && v[1] == 'g' && v[2] == 'g' && v[3] == 'S'){
+					uvlong g = leuint(v+6) | (uvlong)leuint(v+10)<<32;
+					ctx->duration = g * 1000 / 48000; /* granule positions are always 48KHz */
+				}
+				if(v != nil)
+					v++;
+			}
+			if(ctx->duration != 0)
+				break;
+		}
+	}
+
+	return 0;
+}

lib/libtags/s3m.c

@@ -0,0 +1,17 @@
+#include "tagspriv.h"
+
+int
+tags3m(Tagctx *ctx)
+{
+	char d[28+1+1], o[28*UTFmax+1], *s;
+
+	if(ctx->read(ctx, d, 28+1+1) != 28+1+1 || (d[28] != 0x1a && d[28] != 0) || d[29] != 0x10)
+		return -1;
+	d[28] = 0;
+	for(s = d+27; s != d-1 && (*s == ' ' || *s == 0); s--);
+	s[1] = 0;
+	if(cp437toutf8(o, sizeof(o), d, s+1-d) > 0)
+		txtcb(ctx, Ttitle, "", o);
+
+	return 0;
+}

lib/libtags/tags.c

@@ -0,0 +1,80 @@
+#include "tagspriv.h"
+
+typedef struct Getter Getter;
+
+struct Getter
+{
+	int (*f)(Tagctx *ctx);
+	int format;
+};
+
+extern int tagflac(Tagctx *ctx);
+extern int tagid3v1(Tagctx *ctx);
+extern int tagid3v2(Tagctx *ctx);
+extern int tagit(Tagctx *ctx);
+extern int tagm4a(Tagctx *ctx);
+extern int tagopus(Tagctx *ctx);
+extern int tags3m(Tagctx *ctx);
+extern int tagvorbis(Tagctx *ctx);
+extern int tagwav(Tagctx *ctx);
+extern int tagxm(Tagctx *ctx);
+extern int tagmod(Tagctx *ctx);
+
+static const Getter g[] =
+{
+	{tagid3v2, Fmp3},
+	{tagid3v1, Fmp3},
+	{tagvorbis, Fogg},
+	{tagflac, Fflac},
+	{tagm4a, Fm4a},
+	{tagopus, Fopus},
+	{tagwav, Fwav},
+	{tagit, Fit},
+	{tagxm, Fxm},
+	{tags3m, Fs3m},
+	{tagmod, Fmod},
+};
+
+void
+tagscallcb(Tagctx *ctx, int type, const char *k, char *s, int offset, int size, Tagread f)
+{
+	char *e;
+
+	if(f == nil && size == 0){
+		while((uchar)*s <= ' ' && *s)
+			s++;
+		e = s + strlen(s);
+		while(e != s && (uchar)e[-1] <= ' ')
+			e--;
+		*e = 0;
+	}
+	if(*s){
+		ctx->tag(ctx, type, k, s, offset, size, f);
+		if(type != Tunknown){
+			ctx->found |= 1<<type;
+			ctx->num++;
+		}
+	}
+}
+
+int
+tagsget(Tagctx *ctx)
+{
+	int i, res;
+
+	ctx->channels = ctx->samplerate = ctx->bitrate = ctx->duration = 0;
+	ctx->found = 0;
+	ctx->format = Funknown;
+	ctx->restart = 0;
+	res = -1;
+	for(i = 0; i < nelem(g); i++){
+		ctx->num = 0;
+		if(g[i].f(ctx) == 0){
+			ctx->format = g[i].format;
+			res = 0;
+		}
+		ctx->seek(ctx, ctx->restart, 0);
+	}
+
+	return res;
+}

lib/libtags/tags.h

@@ -0,0 +1,94 @@
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct Tagctx Tagctx;
+typedef int (*Tagread)(void *buf, int *cnt);
+
+/* Tag type. */
+enum
+{
+	Tunknown = -1,
+	Tartist,
+	Talbum,
+	Ttitle,
+	Tdate, /* "2014", "2015/02/01", but the year goes first */
+	Ttrack, /* "1", "01", "1/4", but the track number goes first */
+	Talbumgain,
+	Talbumpeak,
+	Ttrackgain,
+	Ttrackpeak,
+	Tgenre,
+	Timage,
+};
+
+/* Format of the audio file. */
+enum
+{
+	Funknown = -1,
+	Fmp3,
+	Fogg,
+	Fflac,
+	Fm4a,
+	Fopus,
+	Fwav,
+	Fit,
+	Fxm,
+	Fs3m,
+	Fmod,
+
+	Fmax,
+};
+
+/* Tag parser context. You need to set it properly before parsing an audio file using libtags. */
+struct Tagctx
+{
+	/* Read function. This is what libtags uses to read the file. */
+	int (*read)(Tagctx *ctx, void *buf, int cnt);
+
+	/* Seek function. This is what libtags uses to seek through the file. */
+	int (*seek)(Tagctx *ctx, int offset, int whence);
+
+	/* Callback that is used by libtags to inform about the tags of a file.
+	 * "type" is the tag's type (Tartist, ...) or Tunknown if libtags doesn't know how to map a tag kind to
+	 * any of these. "k" is the raw key like "TPE1", "TPE2", etc. "s" is the null-terminated string unless "type" is
+	 * Timage. "offset" and "size" define the placement and size of the image cover ("type" = Timage)
+	 * inside the file, and "f" is not NULL in case reading the image cover requires additional
+	 * operations on the data, in which case you need to read the image cover as a stream and call this
+	 * function to apply these operations on the contents read.
+	 */
+	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;
+
+	/* Memory buffer to work in. */
+	char *buf;
+
+	/* Size of the buffer. Must be at least 256 bytes. */
+	int bufsz;
+
+	/* Here goes the stuff libtags sets. It should be accessed after tagsget() returns.
+	 * A value of 0 means it's undefined.
+	 */
+	int channels; /* Number of channels. */
+	int samplerate; /* Hz */
+	int bitrate; /* Bitrate, bits/s. */
+	int duration; /* ms */
+	int format; /* Fmp3, Fogg, Fflac, Fm4a */
+
+	/* Private, don't touch. */
+	int found;
+	int num;
+	int restart;
+};
+
+/* Parse the file using this function. Returns 0 on success. */
+extern int tagsget(Tagctx *ctx);
+
+#ifdef __cplusplus
+}
+#endif

lib/libtags/tagspriv.h

@@ -0,0 +1,59 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <stdint.h>
+#define snprint snprintf
+#define cistrcmp strcasecmp
+#define cistrncmp strncasecmp
+#define nil NULL
+#define UTFmax 4
+#define nelem(x) (int)(sizeof(x)/sizeof((x)[0]))
+typedef uint8_t uchar;
+typedef uint16_t u16int;
+typedef uint32_t u32int;
+typedef uint64_t uvlong;
+typedef unsigned int uint;
+typedef unsigned short ushort;
+#include "tags.h"
+
+enum
+{
+	Numgenre = 192,
+};
+
+#define beuint(d) (uint)(((uchar*)(d))[0]<<24 | ((uchar*)(d))[1]<<16 | ((uchar*)(d))[2]<<8 | ((uchar*)(d))[3]<<0)
+#define leuint(d) (uint)(((uchar*)(d))[3]<<24 | ((uchar*)(d))[2]<<16 | ((uchar*)(d))[1]<<8 | ((uchar*)(d))[0]<<0)
+
+extern const char *id3genres[Numgenre];
+
+/*
+ * Converts (to UTF-8) at most sz bytes of src and writes it to out buffer.
+ * Returns the number of bytes converted.
+ * You need sz*2+1 bytes for out buffer to be completely safe.
+ */
+int iso88591toutf8(uchar *out, int osz, const uchar *src, int sz);
+
+/*
+ * Converts (to UTF-8) at most sz bytes of src and writes it to out buffer.
+ * Returns the number of bytes converted or < 0 in case of error.
+ * You need sz*4+1 bytes for out buffer to be completely safe.
+ * UTF-16 defaults to big endian if there is no BOM.
+ */
+int utf16to8(uchar *out, int osz, const uchar *src, int sz);
+
+/*
+ * Same as utf16to8, but CP437 to UTF-8.
+ */
+int cp437toutf8(char *o, int osz, const char *s, int sz);
+
+/*
+ * This one is common for both vorbis.c and flac.c
+ * It maps a string k to tag type and executes the callback from ctx.
+ * Returns 1 if callback was called, 0 otherwise.
+ */
+void cbvorbiscomment(Tagctx *ctx, char *k, char *v);
+
+void tagscallcb(Tagctx *ctx, int type, const char *k, char *s, int offset, int size, Tagread f);
+
+#define txtcb(ctx, type, k, s) tagscallcb(ctx, type, k, (char*)s, 0, 0, nil)

lib/libtags/utf16.c

@@ -0,0 +1,59 @@
+/* Horror stories: http://en.wikipedia.org/wiki/UTF-16 */
+#include "tagspriv.h"
+
+#define rchr(s) (be ? ((s)[0]<<8 | (s)[1]) : ((s)[1]<<8 | (s)[0]))
+
+static const uchar mark[] = {0x00, 0x00, 0xc0, 0xe0, 0xf0};
+
+int
+utf16to8(uchar *o, int osz, const uchar *s, int sz)
+{
+	int i, be, c, c2, wr, j;
+
+	i = 0;
+	be = 1;
+	if(s[0] == 0xfe && s[1] == 0xff)
+		i += 2;
+	else if(s[0] == 0xff && s[1] == 0xfe){
+		be = 0;
+		i += 2;
+	}
+
+	for(; i < sz-1 && osz > 1;){
+		c = rchr(&s[i]);
+		i += 2;
+		if(c >= 0xd800 && c <= 0xdbff && i < sz-1){
+			c2 = rchr(&s[i]);
+			if(c2 >= 0xdc00 && c2 <= 0xdfff){
+				c = 0x10000 | (c - 0xd800)<<10 | (c2 - 0xdc00);
+				i += 2;
+			}else
+				return -1;
+		}else if(c >= 0xdc00 && c <= 0xdfff)
+			return -1;
+
+		if(c < 0x80)
+			wr = 1;
+		else if(c < 0x800)
+			wr = 2;
+		else if(c < 0x10000)
+			wr = 3;
+		else
+			wr = 4;
+
+		osz -= wr;
+		if(osz < 1)
+			break;
+
+		o += wr;
+		for(j = wr; j > 1; j--){
+			*(--o) = (c & 0xbf) | 0x80;
+			c >>= 6;
+		}
+		*(--o) = c | mark[wr];
+		o += wr;
+	}
+
+	*o = 0;
+	return i;
+}

lib/libtags/vorbis.c

@@ -0,0 +1,132 @@
+/*
+ * https://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-810005
+ * https://wiki.xiph.org/VorbisComment
+ */
+#include "tagspriv.h"
+
+void
+cbvorbiscomment(Tagctx *ctx, char *k, char *v){
+	if(*v == 0)
+		return;
+	if(cistrcmp(k, "album") == 0)
+		txtcb(ctx, Talbum, k, v);
+	else if(cistrcmp(k, "title") == 0)
+		txtcb(ctx, Ttitle, k, v);
+	else if(cistrcmp(k, "artist") == 0)
+		txtcb(ctx, Tartist, k, v);
+	else if(cistrcmp(k, "tracknumber") == 0)
+		txtcb(ctx, Ttrack, k, v);
+	else if(cistrcmp(k, "date") == 0)
+		txtcb(ctx, Tdate, k, v);
+	else if(cistrcmp(k, "replaygain_track_peak") == 0)
+		txtcb(ctx, Ttrackpeak, k, v);
+	else if(cistrcmp(k, "replaygain_track_gain") == 0)
+		txtcb(ctx, Ttrackgain, k, v);
+	else if(cistrcmp(k, "replaygain_album_peak") == 0)
+		txtcb(ctx, Talbumpeak, k, v);
+	else if(cistrcmp(k, "replaygain_album_gain") == 0)
+		txtcb(ctx, Talbumgain, k, v);
+	else if(cistrcmp(k, "genre") == 0)
+		txtcb(ctx, Tgenre, k, v);
+	else
+		txtcb(ctx, Tunknown, k, v);
+}
+
+int
+tagvorbis(Tagctx *ctx)
+{
+	char *v;
+	uchar *d, h[4];
+	int sz, numtags, i, npages, pgend;
+
+	d = (uchar*)ctx->buf;
+	/* need to find vorbis frame with type=3 */
+	for(npages = pgend = 0; npages < 2; npages++){ /* vorbis comment is the second header */
+		int nsegs;
+		if(ctx->read(ctx, d, 27) != 27)
+			return -1;
+		if(memcmp(d, "OggS", 4) != 0)
+			return -1;
+
+		/* calculate the size of the packet */
+		nsegs = d[26];
+		if(ctx->read(ctx, d, nsegs+1) != nsegs+1)
+			return -1;
+		for(sz = i = 0; i < nsegs; sz += d[i++]);
+
+		if(d[nsegs] == 3){ /* comment */
+			/* FIXME - embedded pics make tags span multiple packets */
+			pgend = ctx->seek(ctx, 0, 1) + sz;
+			break;
+		}
+		if(d[nsegs] == 1 && sz >= 28){ /* identification */
+			if(ctx->read(ctx, d, 28) != 28)
+				return -1;
+			sz -= 28;
+			ctx->channels = d[10];
+			ctx->samplerate = leuint(&d[11]);
+			if((ctx->bitrate = leuint(&d[15])) == 0) /* maximum */
+				ctx->bitrate = leuint(&d[19]); /* nominal */
+		}
+
+		ctx->seek(ctx, sz-1, 1);
+	}
+
+	if(npages < 3) {
+		if(ctx->read(ctx, &d[1], 10) != 10 || memcmp(&d[1], "vorbis", 6) != 0)
+			return -1;
+		sz = leuint(&d[7]);
+		if(ctx->seek(ctx, sz, 1) < 0 || ctx->read(ctx, h, 4) != 4)
+			return -1;
+		numtags = leuint(h);
+
+		for(i = 0; i < numtags; i++){
+			if(ctx->read(ctx, h, 4) != 4)
+				return -1;
+			if((sz = leuint(h)) < 0)
+				return -1;
+			/* FIXME - embedded pics make tags span multiple packets */
+			if(pgend < ctx->seek(ctx, 0, 1)+sz)
+				break;
+
+			if(ctx->bufsz < sz+1){
+				if(ctx->seek(ctx, sz, 1) < 0)
+					return -1;
+				continue;
+			}
+			if(ctx->read(ctx, ctx->buf, sz) != sz)
+				return -1;
+			ctx->buf[sz] = 0;
+
+			if((v = strchr(ctx->buf, '=')) == nil)
+				return -1;
+			*v++ = 0;
+			cbvorbiscomment(ctx, ctx->buf, v);
+		}
+	}
+
+	/* calculate the duration */
+	if(ctx->samplerate > 0){
+		sz = ctx->bufsz <= 4096 ? ctx->bufsz : 4096;
+		for(i = sz; i < 65536+16; i += sz - 16){
+			if(ctx->seek(ctx, -i, 2) <= 0)
+				break;
+			v = ctx->buf;
+			if(ctx->read(ctx, v, sz) != sz)
+				break;
+			for(; v != nil && v < ctx->buf+sz;){
+				v = memchr(v, 'O', ctx->buf+sz - v - 14);
+				if(v != nil && v[1] == 'g' && v[2] == 'g' && v[3] == 'S' && (v[5] & 4) == 4){ /* last page */
+					uvlong g = leuint(v+6) | (uvlong)leuint(v+10)<<32;
+					ctx->duration = g * 1000 / ctx->samplerate;
+				}
+				if(v != nil)
+					v++;
+			}
+			if(ctx->duration != 0)
+				break;
+		}
+	}
+
+	return 0;
+}

lib/libtags/wav.c

@@ -0,0 +1,90 @@
+#include "tagspriv.h"
+
+#define le16u(d) (u16int)((d)[0] | (d)[1]<<8)
+
+static struct {
+	char *s;
+	int type;
+}t[] = {
+	{"IART", Tartist},
+	{"ICRD", Tdate},
+	{"IGNR", Tgenre},
+	{"INAM", Ttitle},
+	{"IPRD", Talbum},
+	{"ITRK", Ttrack},
+};
+
+int
+tagwav(Tagctx *ctx)
+{
+	uchar *d;
+	int i, n, info;
+	u32int csz, x;
+	uvlong sz;
+
+	d = (uchar*)ctx->buf;
+
+	sz = 1;
+	info = 0;
+	for(i = 0; i < 8 && sz > 0; i++){
+		if(ctx->read(ctx, d, 4+4+(i?0:4)) != 4+4+(i?0:4))
+			return -1;
+		if(i == 0){
+			if(memcmp(d, "RIFF", 4) != 0 || memcmp(d+8, "WAVE", 4) != 0)
+				return -1;
+			sz = leuint(d+4);
+			if(sz < 4)
+				return -1;
+			sz -= 4;
+			continue;
+		}else if(memcmp(d, "INFO", 4) == 0){
+			info = 1;
+			ctx->seek(ctx, -4, 1);
+			continue;
+		}
+
+		if(sz <= 8)
+			break;
+		sz -= 4+4;
+		csz = leuint(d+4);
+		if(sz < csz)
+			break;
+		sz -= csz;
+
+		if(i == 1){
+			if(memcmp(d, "fmt ", 4) != 0 || csz < 16)
+				return -1;
+			if(ctx->read(ctx, d, 16) != 16)
+				return -1;
+			csz -= 16;
+			ctx->channels = le16u(d+2);
+			ctx->samplerate = leuint(d+4);
+			x = leuint(d+8);
+			if(ctx->channels < 1 || ctx->samplerate < 1 || x < 1)
+				return -1;
+			ctx->duration = sz*1000 / x;
+		}else if(memcmp(d, "LIST", 4) == 0){
+			sz = csz - 4;
+			continue;
+		}else if(memcmp(d, "data", 4) == 0){
+			break;
+		}else if(info){
+			csz++;
+			for(n = 0; n < nelem(t); n++){
+				if(memcmp(d, t[n].s, 4) == 0){
+					if(ctx->read(ctx, d, csz) != (int)csz)
+						return -1;
+					d[csz-1] = 0;
+					txtcb(ctx, t[n].type, "", d);
+					csz = 0;
+					break;
+				}
+			}
+		}
+
+		if(ctx->seek(ctx, csz, 1) < 0)
+			return -1;
+	}
+
+	return i > 0 ? 0 : -1;
+}

lib/libtags/xm.c

@@ -0,0 +1,15 @@
+#include "tagspriv.h"
+
+int
+tagxm(Tagctx *ctx)
+{
+	char d[17+20+1], o[20*UTFmax+1];
+
+	if(ctx->read(ctx, d, 17+20) != 17+20 || cistrncmp(d, "Extended Module: ", 17) != 0)
+		return -1;
+	d[17+20] = 0;
+	if(cp437toutf8(o, sizeof(o), d+17, 20) > 0)
+		txtcb(ctx, Ttitle, "", o);
+
+	return 0;
+}

src/database/CMakeLists.txt

@@ -1,7 +1,7 @@
 idf_component_register(
   SRCS "env_esp.cpp" "database.cpp" "tag_processor.cpp" "db_task.cpp"
   INCLUDE_DIRS "include"
-  REQUIRES "result" "span" "esp_psram" "fatfs")
+  REQUIRES "result" "span" "esp_psram" "fatfs" "libtags")
 
 target_compile_options(${COMPONENT_LIB} PRIVATE ${EXTRA_WARNINGS})
 

src/database/include/tag_processor.hpp

@@ -6,6 +6,8 @@ namespace database {
 
 struct FileInfo {
   bool is_playable;
+  std::string artist;
+  std::string album;
   std::string title;
 };
 

src/database/tag_processor.cpp

@@ -1,14 +1,102 @@
 #include "tag_processor.hpp"
 
+#include <ff.h>
+#include <tags.h>
+#include <esp_log.h>
+
 namespace database {
 
+namespace libtags {
+
+struct Aux {
+  FIL file;
+  FILINFO info;
+  std::string artist;
+  std::string album;
+  std::string title;
+};
+
+static int read(Tagctx *ctx, void *buf, int cnt) {
+	Aux *aux = reinterpret_cast<Aux*>(ctx->aux);
+        UINT bytes_read;
+        if (f_read(&aux->file, buf, cnt, &bytes_read) != FR_OK) {
+          return -1;
+        }
+        return bytes_read;
+}
+
+static int seek(Tagctx *ctx, int offset, int whence) {
+	Aux *aux = reinterpret_cast<Aux*>(ctx->aux);
+        FRESULT res;
+        if (whence == 0) {
+          // Seek from the start of the file. This is f_lseek's behaviour.
+          res = f_lseek(&aux->file, offset);
+        } else if (whence == 1) {
+          // Seek from current offset.
+          res = f_lseek(&aux->file, aux->file.fptr + offset);
+        } else if (whence == 2) {
+          // Seek from the end of the file
+          res = f_lseek(&aux->file, aux->info.fsize + offset);
+        } else {
+          return -1;
+        }
+	return res;
+}
+
+static void
+tag(Tagctx *ctx, int t, const char *k, const char *v, int offset, int size, Tagread f) {
+  Aux *aux = reinterpret_cast<Aux*>(ctx->aux);
+  if (t == Ttitle) {
+    aux->title = v;
+  } else if (t == Tartist) {
+    aux->artist = v;
+  } else if (t == Talbum) {
+    aux->album = v;
+  }
+}
+
+static void
+toc(Tagctx *ctx, int ms, int offset) {}
+
+} // namespace libtags
+
+static const std::size_t kBufSize = 1024;
+static const char* kTag = "TAGS";
+
 auto GetInfo(const std::string& path, FileInfo* out) -> bool {
-  // TODO(jacqueline): bring in taglib for this
-  if (path.ends_with(".mp3")) {
+  libtags::Aux aux;
+  if (f_stat(path.c_str(), &aux.info) != FR_OK || f_open(&aux.file, path.c_str(), FA_READ) != FR_OK) {
+    ESP_LOGI(kTag, "failed to open file");
+    return false;
+  }
+  // Fine to have this on the stack; this is only called on the leveldb task.
+  char buf[kBufSize];
+  Tagctx ctx;
+    ctx.read = libtags::read;
+    ctx.seek = libtags::seek;
+    ctx.tag = libtags::tag;
+    ctx.toc = libtags::toc;
+    ctx.aux = &aux;
+    ctx.buf = buf;
+    ctx.bufsz = kBufSize;
+  int res = tagsget(&ctx);
+  f_close(&aux.file);
+
+  if (res != 0) {
+    ESP_LOGI(kTag, "failed to parse tags");
+    return false;
+  }
+
+  if (ctx.format == Fmp3) {
+    ESP_LOGI(kTag, "file is mp3");
+    ESP_LOGI(kTag, "artist: %s", aux.artist.c_str());
+    ESP_LOGI(kTag, "album: %s", aux.album.c_str());
+    ESP_LOGI(kTag, "title: %s", aux.title.c_str());
     out->is_playable = true;
-    out->title = path.substr(0, path.size() - 4);
+    out->title = aux.title;
     return true;
   }
+
   return false;
 }
 

tools/cmake/common.cmake

@@ -8,6 +8,7 @@ set(COMPONENTS "")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/catch2")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/cbor")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/libmad")
+list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/libtags")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/lvgl")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/result")
 list(APPEND EXTRA_COMPONENT_DIRS "$ENV{PROJ_PATH}/lib/span")