Added support for ID3V2 ReplayGain tags (as written by Foobar). Generalized the replaygain tag parsing a bit, to cut down the code size (APE tags should use this as well, but as it requires larger changes, it will have to wait for another commit). Also fixed a bug in the ID3V2 parser; ISO-8859-1 strings could confuse the main parsing loop (causing bufferpos to come out of sync).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@7243 a1c6a512-1295-4272-9138-f99709370657

firmware/replaygain.c

@@ -20,9 +20,12 @@
 #include <ctype.h>
 #include <inttypes.h>
 #include <math.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdbool.h>
+#include <string.h>
+#include <system.h>
+#include "id3.h"
 #include "debug.h"
 
 /* The fixed point math routines (with the exception of fp_atof) are based
@@ -326,3 +329,106 @@ long get_replaypeak(const char* str)
     
     return peak;
 }
+
+/* Compare two strings, ignoring case, up to the end nil or another end of
+ * string character. E.g., if eos is '=', "a=" would equal "a". Returns 
+ * true for a match, false otherwise.
+ * TODO: This should be placed somewhere else, as it could be useful in 
+ *       other places too.
+ */
+static bool str_equal(const char* s1, const char* s2, char eos)
+{
+    char c1 = 0;
+    char c2 = 0;
+
+    while (*s1 && *s2 && (*s1 != eos) && (*s2 != eos))
+    {
+        if ((c1 = toupper(*s1)) != (c2 = toupper(*s2)))
+        {
+            return false;
+        }
+        
+        s1++;
+        s2++;
+    }
+    
+    if (c1 == eos)
+    {
+        c1 = '\0';
+    }
+    
+    if (c2 == eos)
+    {
+        c2 = '\0';
+    }
+
+    return c1 == c2;
+}
+
+/* Check for a ReplayGain tag conforming to the "VorbisGain standard". If 
+ * found, set the mp3entry accordingly. If value is NULL, key is expected 
+ * to be on the "key=value" format, and the comparion/extraction is done 
+ * accordingly. buffer is where to store the text contents of the gain tags;
+ * up to length bytes (including end nil) can be written.
+ * Returns number of bytes written to the tag text buffer, or zero if
+ * no ReplayGain tag was found (or nothing was copied to the buffer for
+ * other reasons).
+ */
+long parse_replaygain(const char* key, const char* value, 
+    struct mp3entry* entry, char* buffer, int length)
+{
+    const char* val = value;
+    char **p = NULL;
+    char eos = '\0';
+    
+    if (!val)
+    {
+        if (!(val = strchr(key, '=')))
+        {
+            return 0;
+        }
+        
+        val++;
+        eos = '=';
+    }
+
+    if (str_equal(key, "replaygain_track_gain", eos) 
+        || (str_equal(key, "rg_radio", eos) && !entry->track_gain))
+    {
+        entry->track_gain = get_replaygain(val);
+        p = &(entry->track_gain_string);
+    } 
+    else if (str_equal(key, "replaygain_album_gain", eos)
+        || (str_equal(key, "rg_audiophile", eos) && !entry->album_gain))
+    {
+        entry->album_gain = get_replaygain(val);
+        p = &(entry->album_gain_string);
+    }
+    else if (str_equal(key, "replaygain_track_peak", eos) 
+        || (str_equal(key, "rg_peak", eos) && !entry->track_peak))
+    {
+        entry->track_peak = get_replaypeak(val);
+    } 
+    else if (str_equal(key, "replaygain_album_peak", eos))
+    {
+        entry->album_peak = get_replaypeak(val);
+    }
+
+    if (p)
+    {
+        int len = strlen(val);
+        
+        len = MIN(len, length - 1);
+
+        /* A few characters just isn't interesting... */
+        if (len > 1)
+        {
+            strncpy(buffer, val, len);
+            buffer[len] = 0;
+            *p = buffer;
+            return len + 1;
+        }
+    }
+
+    return 0;
+}