id3v2: Decode CTOC flags

wader · May 2, 2023 · f237db2 · f237db2
1 parent b1b0891
commit f237db2
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Showing 2 changed files with 19 additions and 2 deletions.
diff --git a/format/id3/id3v2.go b/format/id3/id3v2.go
@@ -425,9 +425,23 @@ func decodeFrame(d *decode.D, version int) uint64 {
 			d.FieldU32("end_offset")
 			decodeFrames(d, version, uint64(d.BitsLeft()/8))
 		},
+
+		// <ID3v2.3 or ID3v2.4 frame header, ID: "CTOC">   (10 bytes)
+		// Element ID      <text string> $00
+		// Flags           %000000ab
+		// Entry count     $xx  (8-bit unsigned int)
+		// <Child Element ID list>
+		// <Optional embedded sub-frames>
+		//
+		// flag a: Top-level bit
+		// flag b: Ordered bit
 		"CTOC": func(d *decode.D) {
 			d.FieldStrFn("element_id", textNullFn(encodingUTF8))
-			d.FieldU8("ctoc_flags")
+			d.FieldStruct("ctoc_flags", func(d *decode.D) {
+				d.FieldU6("unused0")
+				d.FieldBool("top_level")
+				d.FieldBool("order")
+			})
 			entryCount := d.FieldU8("entry_count")
 			d.FieldArray("entries", func(d *decode.D) {
 				for i := uint64(0); i < entryCount; i++ {

diff --git a/format/id3/testdata/ctoc.fqtest b/format/id3/testdata/ctoc.fqtest
@@ -25,7 +25,10 @@ $ fq -d id3v2 dv ctoc
 0x10|         00                                    |   .            |        grouping_identity: false 0x13.2-0x13.2 (0.1)
 0x10|         00                                    |   .            |        unused1: 0 0x13.3-0x13.7 (0.5)
 0x10|            54 4f 43 4d 00                     |    TOCM.       |      element_id: "TOCM" 0x14-0x18.7 (5)
-0x10|                           03                  |         .      |      ctoc_flags: 3 0x19-0x19.7 (1)
+    |                                               |                |      ctoc_flags{}: 0x19-0x19.7 (1)
+0x10|                           03                  |         .      |        unused0: 0 0x19-0x19.5 (0.6)
+0x10|                           03                  |         .      |        top_level: true 0x19.6-0x19.6 (0.1)
+0x10|                           03                  |         .      |        order: true 0x19.7-0x19.7 (0.1)
 0x10|                              13               |          .     |      entry_count: 19 0x1a-0x1a.7 (1)
     |                                               |                |      entries[0:19]: 0x1b-0x6f.7 (85)
 0x10|                                 63 68 30 00   |           ch0. |        [0]: "ch0" entry 0x1b-0x1e.7 (4)