public static id3tag read_id3tag(System.IO.Stream strm, bool createImageObject)
{
id3tag tag = new id3tag();
byte[] id3_header = new byte[10];// ID3タグヘッダ用
strm.ReadOrThrow(id3_header, 0, 10);
id3v2header header = read_header(id3_header);
if (header == null)
{
return(null);
}
if (header.size >= strm.Length)
{
return(null);
}
tag.head = header;
if ((tag.head.flag & FLAG_HEAD_EXTENSION) > 0)// 拡張ヘッダがあるときサイズだけ読んでスキップ
{
byte[] ext_header = new byte[4];
strm.Read(ext_header, 0, 4);
int size;
if (tag.head.version == 3) // v2.3
{
size = ((ext_header[0] * 256 + ext_header[1]) * 256 + ext_header[2]) * 256 + ext_header[3];
}
else // v2.4
{
size = ((ext_header[0] * 128 + ext_header[1]) * 128 + ext_header[2]) * 128 + ext_header[3] - 4;
}
strm.Seek(size, System.IO.SeekOrigin.Current);
}
/* frame */
byte[] frame_buf = new byte[tag.head.size];
strm.Read(frame_buf, 0, tag.head.size);
if (((tag.head.flag & FLAG_HEAD_UNSYNC) > 0) && tag.head.version == 3)
{
frame_buf = DecodeUnsync(frame_buf);
}
MemoryStream tagBodyStream = new MemoryStream(frame_buf, 0, frame_buf.Length);
int count = 0;
while (true)
{ //offset < tag.head.size
frame fr = read_frame(tagBodyStream, tag, createImageObject);
if (fr == null)
{
break;
}
count++;
tag.frame.Add(fr);
}
return(tag);
}
static frame read_frame(Stream strm, id3tag tag, bool createImageObject)
{
int i;
int headsize = (tag.head.version == 2) ? 6 : 10;
if (strm.Length < headsize)
{
return(null);
}
byte[] buf = new byte[headsize];
strm.Read(buf, 0, headsize);
frame fr = new frame();
fr.id_x = 0; // どれでもない
uint _size;
switch (tag.head.version)
{
case 2:
fr.id = Encoding.ASCII.GetString(buf, 0, 3);
_size = ((uint)buf[3] * 256 + buf[4]) * 256 + buf[5];
fr.flag = 0;
for (i = 0; i < FRAMES.Length; i++)
{
if (fr.id == FRAMES[i].name2)
{
fr.id_x = i; break;
}
}
break;
case 3:
fr.id = Encoding.ASCII.GetString(buf, 0, 4);
_size = (((uint)buf[4] * 256 + buf[5]) * 256 + buf[6]) * 256 + buf[7];
fr.flag = ((uint)buf[8] << 7) + (((uint)buf[9] >> 4) & 0x0F) + (((uint)buf[9] << 1) & 0x40);
for (i = 0; i < FRAMES.Length; i++)
{
if (fr.id == FRAMES[i].name3)
{
fr.id_x = i; break;
}
}
break;
case 4:
fr.id = Encoding.ASCII.GetString(buf, 0, 4);
_size = (((uint)buf[4] * 128 + buf[5]) * 128 + buf[6]) * 128 + buf[7];
fr.flag = ((uint)buf[8] << 8) + buf[9];
for (i = 0; i < FRAMES.Length; i++)
{
if (fr.id == FRAMES[i].name4)
{
fr.id_x = i; break;
}
}
break;
default:
return(null);
}
if (_size > strm.Length)
{
return(null);
}
fr.size = (int)_size;
if ((fr.flag & FLAG_FRAME_CRYPTED) > 0)
{
return(null); // 暗号化なんて知りませんよっと
}
if ((fr.flag & FLAG_FRAME_COMPRESSED) > 0)
{
return(null); // 圧縮は実装してない
}
if (fr.size == 0)
{
return(null);
}
if (fr.id == "")
{
return(null);
}
int readsize = headsize + fr.size;
if (readsize > strm.Length)
{
return(null);
}
int offset = 0;
byte[] tmp = new byte[fr.size]; // + 2
strm.Read(tmp, 0, fr.size);
if (((fr.flag & FLAG_FRAME_UNSYNC) > 0) && tag.head.version == 4)
{
tmp = DecodeUnsync(tmp);
}
if ((fr.flag & FLAG_FRAME_DATALENGTH) > 0) // 元サイズ情報を飛ばす
{
offset = 4;
fr.size -= 4;
}
/*
* if ((fr.flag & FLAG_FRAME_CRYPTED) > 0) // 暗号方式を飛ばす
* {
* offset += 1;
* fr.size -= 1;
* }
*/
MemoryStream frameBodyStream = new MemoryStream(tmp, offset, tmp.Length - offset);
readFrameBody(frameBodyStream, fr, createImageObject);
return(fr);
}
