1 files changed, 195 insertions, 0 deletions

diff --git a/apps/metadata/vgm.c b/apps/metadata/vgm.c
new file mode 100644
index 0000000000..9ea95b3939
--- /dev/null
+++ b/apps/metadata/vgm.c
@@ -0,0 +1,195 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <inttypes.h>
+
+#include "system.h"
+#include "metadata.h"
+#include "metadata_common.h"
+#include "metadata_parsers.h"
+#include "rbunicode.h"
+
+/* Ripped off from Game_Music_Emu 0.5.2. http://www.slack.net/~ant/ */
+
+typedef unsigned char byte;
+
+enum { header_size = 0x40 };
+enum { max_field = 64 };
+
+struct header_t
+{
+    char tag [4]; 
+    byte data_size [4];
+    byte version [4];
+    byte psg_rate [4];
+    byte ym2413_rate [4];
+    byte gd3_offset [4];
+    byte track_duration [4];
+    byte loop_offset [4];
+    byte loop_duration [4];
+    byte frame_rate [4];
+    byte noise_feedback [2];
+    byte noise_width;
+    byte unused1;
+    byte ym2612_rate [4];
+    byte ym2151_rate [4];
+    byte data_offset [4];
+    byte unused2 [8];
+};
+
+static byte const* skip_gd3_str( byte const* in, byte const* end )
+{
+    while ( end - in >= 2 )
+    {
+        in += 2;
+        if ( !(in [-2] | in [-1]) )
+            break;
+    }
+    return in;
+}
+
+static byte const* get_gd3_str( byte const* in, byte const* end, char* field )
+{
+    byte const* mid = skip_gd3_str( in, end );
+    int len = (mid - in) / 2 - 1;
+    if ( field && len > 0 )
+    {
+        len = len < (int) max_field ? len : (int) max_field;
+
+        field [len] = 0;
+        /* Conver to utf8 */
+        utf16LEdecode( in, field, len );
+        
+        /* Copy string back to id3v2buf */
+        strcpy( (char*) in, field );
+    }
+    return mid;
+}
+
+static byte const* get_gd3_pair( byte const* in, byte const* end, char* field )
+{
+    return skip_gd3_str( get_gd3_str( in, end, field ), end );
+}
+
+static void parse_gd3( byte const* in, byte const* end, struct mp3entry* id3 )
+{
+    char* p = id3->path;
+    id3->title = (char *) in;
+    in = get_gd3_pair( in, end, p ); /* Song */
+
+    id3->album = (char *) in;
+    in = get_gd3_pair( in, end, p ); /* Game */
+
+    in = get_gd3_pair( in, end, NULL ); /* System */
+
+    id3->artist = (char *) in;
+    in = get_gd3_pair( in, end, p ); /* Author */
+
+#if MEMORYSIZE > 2
+    in = get_gd3_str ( in, end, NULL  ); /* Copyright */
+    in = get_gd3_pair( in, end, NULL ); /* Dumper */
+
+    id3->comment = (char *) in;
+    in = get_gd3_str ( in, end, p ); /* Comment */
+#endif
+}
+
+int const gd3_header_size = 12;
+
+static long check_gd3_header( byte* h, long remain )
+{
+    if ( remain < gd3_header_size ) return 0;
+    if ( memcmp( h, "Gd3 ", 4 ) ) return 0;
+    if ( get_long_le( h + 4 ) >= 0x200 ) return 0;
+
+    long gd3_size = get_long_le( h + 8 );
+    if ( gd3_size > remain - gd3_header_size )
+        gd3_size = remain - gd3_header_size;
+
+    return gd3_size;
+}
+
+static void get_vgm_length( struct header_t* h, struct mp3entry* id3 )
+{
+    long length = get_long_le( h->track_duration ) * 10 / 441;
+    if ( length > 0 )
+    {
+        long loop_length = 0, intro_length = 0;
+        long loop = get_long_le( h->loop_duration );
+        if ( loop > 0 && get_long_le( h->loop_offset ) )
+        {
+            loop_length = loop * 10 / 441;
+            intro_length = length - loop_length;
+        }
+        else
+        {
+            intro_length = length; /* make it clear that track is no longer than length */
+            loop_length = 0;
+        }
+        
+         id3->length = intro_length + 2 * loop_length; /* intro + 2 loops */
+         return;
+    }
+
+    id3->length = 150 * 1000; /* 2.5 minutes */
+}
+
+bool get_vgm_metadata(int fd, struct mp3entry* id3)
+{
+    /* Use the id3v2 part of the id3 structure as a temporary buffer */
+    unsigned char* buf = (unsigned char *)id3->id3v2buf;
+    int read_bytes;
+
+    memset(buf, 0, ID3V2_BUF_SIZE);
+    if ((lseek(fd, 0, SEEK_SET) < 0) 
+         || ((read_bytes = read(fd, buf, header_size)) < header_size))
+    {
+        return false;
+    }
+
+    id3->vbr = false;
+    id3->filesize = filesize(fd);
+
+    id3->bitrate = 706;
+    id3->frequency = 44100;
+
+    /* If file is gzipped, will get metadata later */
+    if (memcmp(buf, "Vgm ", 4))
+    {
+        /* We must set a default song length here because
+            the codec can't do it anymore */
+        id3->length = 150 * 1000; /* 2.5 minutes */
+        return true;
+    }
+
+    /* Get song length from header */
+    struct header_t* header = (struct header_t*) buf;
+    get_vgm_length( header, id3 );
+
+    long gd3_offset = get_long_le( header->gd3_offset ) - 0x2C;
+    
+    /* No gd3 tag found */
+    if ( gd3_offset < 0 )
+        return true;
+
+    /*  Seek to gd3 offset and read as 
+         many bytes posible */
+    gd3_offset = id3->filesize - (header_size + gd3_offset);
+    if ((lseek(fd, -gd3_offset, SEEK_END) < 0) 
+         || ((read_bytes = read(fd, buf, ID3V2_BUF_SIZE)) <= 0))
+        return true;
+
+    byte* gd3 = buf;
+    long gd3_size = check_gd3_header( gd3, read_bytes );
+
+    /* GD3 tag is zero */
+    if ( gd3_size == 0 )
+        return true;
+
+    /* Finally, parse gd3 tag */
+    if ( gd3 )
+        parse_gd3( gd3 + gd3_header_size, gd3 + read_bytes, id3 );
+
+    return true;
+}