From ee702d71e2635bc79fbcc8cd00cd74265cb5aed9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Mangano?= <fmang@mg0.fr>
Date: Tue, 1 Jan 2013 14:25:20 +0100
Subject: [PATCH] parse tags

---
 opustags.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/opustags.c b/opustags.c
index c66c0a7..5116820 100644
--- a/opustags.c
+++ b/opustags.c
@@ -4,6 +4,61 @@
 #include <string.h>
 #include <ogg/ogg.h>
 
+typedef struct {
+    uint32_t vendor_length;
+    const char *vendor_string;
+    uint32_t count;
+    uint32_t *lengths;
+    const char **comment;
+} opus_tags;
+
+int parse_tags(char *data, long len, opus_tags *tags){
+    long pos;
+    if(len < 8+4+4)
+        return -1;
+    if(strncmp(data, "OpusTags", 8) != 0)
+        return -1;
+    // Vendor
+    pos = 8;
+    tags->vendor_length = le32toh(*((uint32_t*) (data + pos)));
+    tags->vendor_string = data + pos + 4;
+    pos += 4 + tags->vendor_length;
+    if(pos + 4 > len)
+        return -1;
+    // Count
+    tags->count = le32toh(*((uint32_t*) (data + pos)));
+    if(tags->count == 0)
+        return 0;
+    tags->lengths = calloc(tags->count, sizeof(uint32_t));
+    if(tags->lengths == NULL)
+        return -1;
+    tags->comment = calloc(tags->count, sizeof(const char*));
+    if(tags->comment == NULL){
+        free(tags->lengths);
+        return -1;
+    }
+    pos += 4;
+    // Comment
+    uint32_t i;
+    for(i=0; i<tags->count; i++){
+        tags->lengths[i] = le32toh(*((uint32_t*) (data + pos)));
+        tags->comment[i] = data + pos + 4;
+        pos += 4 + tags->lengths[i];
+        if(pos > len)
+            return -1;
+    }
+    if(pos != len)
+        return -1;
+    return 0;
+}
+
+void free_tags(opus_tags *tags){
+    if(tags->count > 0){
+        free(tags->lengths);
+        free(tags->comment);
+    }
+}
+
 int main(int argc, char **argv){
     FILE *in = fopen(argv[1], "r");
     if(!in){
@@ -14,6 +69,7 @@ int main(int argc, char **argv){
     ogg_stream_state os;
     ogg_page og;
     ogg_packet op;
+    opus_tags tags;
     ogg_sync_init(&oy);
     char *buf;
     size_t len;
@@ -54,8 +110,16 @@ int main(int argc, char **argv){
                     error = "opustags: invalid identification header";
             }
             if(packet_count == 2){ // Comment header
-                if(strncmp((char*) op.packet, "OpusTags", 8) != 0)
+                if(parse_tags((char*) op.packet, op.bytes, &tags) == -1)
                     error = "opustags: invalid comment header";
+                fwrite(tags.vendor_string, 1, tags.vendor_length, stdout);
+                puts("");
+                int i;
+                for(i=0; i<tags.count; i++){
+                    fwrite(tags.comment[i], 1, tags.lengths[i], stdout);
+                    puts("");
+                }
+                free_tags(&tags);
                 break;
             }
         }