/// <summary>
/// ID3v2タグを読む
/// </summary>
/// <param name="strm"></param>
/// <param name="createImageObject"></param>
/// <returns></returns>
public static ID3tag readID3tag(System.IO.Stream strm, bool createImageObject)
{
// ヘッダ読み込み
byte[] id3_header = strm.ReadBytes(HEADER_LEN);
Header header = readHeader(id3_header);
if (header == null)
{
return(null);
}
if (header.Size >= strm.Length)
{
return(null);
}
ID3tag tag = new ID3tag();
tag.head = header;
// 拡張ヘッダがあるときサイズだけ読んでスキップ
if (tag.head.Flag.HasFlag(HEADER_FLAG.EXTENSION))
{
byte[] ext_header = strm.ReadBytes(EXT_HEADER_LEN);
var size = tag.head.Version == ID3V2_VER.ID3V23
? ReadUInt32(ext_header, 0)
: ReadUInt28(ext_header, 0) - EXT_HEADER_LEN; // v3とv4でEXT_HEADER_LENの扱いが違う
strm.Seek(size, System.IO.SeekOrigin.Current);
}
// 全Frameのデータ領域を読み出す
byte[] frame_buf = strm.ReadBytes(header.Size);
// .2, .3の場合は非同期化の解除
if (header.Version != ID3V2_VER.ID3V24 && header.Flag.HasFlag(HEADER_FLAG.UNSYNC))
{
decodeUnsync(ref frame_buf);
}
// 各Frameのデータ読み出し
var tagBodyStream = new MemoryStream(frame_buf, 0, frame_buf.Length);
while (true)
{
try
{
Frame fr = readFrame(tagBodyStream, tag, createImageObject);
if (fr != null)
{
tag.frame.Add(fr);
}
}
catch (EndOfTagException)
{
break;
}
}
return(tag);
}
/// <summary>
/// ID3V2タグフレームを読む
/// </summary>
/// <param name="strm"></param>
/// <param name="tag"></param>
/// <param name="createImageObject"></param>
/// <returns></returns>
private static Frame readFrame(Stream strm, ID3tag tag, bool createImageObject)
{
int frameHeaderSize = (tag.head.Version == ID3V2_VER.ID3V22) ? FRAME_HEADER_LEN_2 : FRAME_HEADER_LEN_34;
if (strm.Length - strm.Position < frameHeaderSize)
{
throw new EndOfTagException();
}
byte[] buf = strm.ReadBytes(frameHeaderSize);
var frame = readFrameHeader(buf, tag.head.Version);
if (frame.Size <= 0)
{
throw new EndOfTagException();
}
if (strm.Length - strm.Position < frame.Size)
{
throw new EndOfTagException();
}
int offset = 0;
bool unsupported = false;
if (frame.ID == null)
{
unsupported = true;
}
// 暗号化なんて知りませんよっと
if (frame.Flag.HasFlag(FRAME_FLAG.CRYPTED))
{
unsupported = true;
}
// 圧縮は実装してない
if (frame.Flag.HasFlag(FRAME_FLAG.COMPRESSED))
{
unsupported = true;
}
// グループ識別子を無視
if (frame.Flag.HasFlag(FRAME_FLAG.GROUPED))
{
// unsupportedにはしない
offset += 1;
}
// DATALENGTHを飛ばす
if (frame.Flag.HasFlag(FRAME_FLAG.DATALENGTH))
{
offset += 4;
}
if (unsupported)
{
strm.Seek(frame.Size, SeekOrigin.Current);
return(null);
}
strm.Seek(offset, SeekOrigin.Current);
byte[] buffer = strm.ReadBytes(frame.Size - offset);
if (frame.Flag.HasFlag(FRAME_FLAG.UNSYNC) && tag.head.Version == ID3V2_VER.ID3V24)
{
decodeUnsync(ref buffer);
}
MemoryStream frameBodyStream = new MemoryStream(buffer);
readFrameBody(frameBodyStream, frame, createImageObject);
return(frame);
}
