private void ReadFooter()
{
// bring in the first three bytes. it must be ID3 or we have no tag
// TODO add logic to check the end of the file for "3D1" and other
// possible starting spots
string id3start = new string (br.ReadChars(3));
// check for a tag
if (!id3start.Equals("3DI"))
{
// TODO we are f****d. not really we just don't ahve a tag
// and we need to bail out gracefully.
//throw id3v23ReaderException;
}
else
{
// we have a tag
this.hasTag = true;
}
// read id3 version. 2 bytes:
// The first byte of ID3v2 version is it's major version,
// while the second byte is its revision number
this.MajorVersion = System.Convert.ToInt32(br.ReadByte());
this.MinorVersion = System.Convert.ToInt32(br.ReadByte());
// here is where we get fancy. I am useing silisoft's php code as
// a reference here. we are going to try and parse for 2.2, 2.3 and 2.4
// in one pass. hold on!!
if ((this.hasTag) && (this.MajorVersion <= 4)) // probably won't work on higher versions
{
// (%ab000000 in v2.2, %abc00000 in v2.3, %abcd0000 in v2.4.x)
//read next byte for flags
bool [] boolar = BitReader.ToBitBool(br.ReadByte());
// set the flags
if (this.MajorVersion == 2)
{
this.FA_Unsynchronisation = boolar[0];
this.FB_ExtendedHeader = boolar[1];
}
else if (this.MajorVersion == 3)
{
// set the flags
this.FA_Unsynchronisation = boolar[0];
this.FB_ExtendedHeader = boolar[1];
this.FC_ExperimentalIndicator = boolar[2];
}
else if (this.MajorVersion == 4)
{
// set the flags
this.FA_Unsynchronisation = boolar[0];
this.FB_ExtendedHeader = boolar[1];
this.FC_ExperimentalIndicator = boolar[2];
this.FD_Footer = boolar[3];
}
// read teh size
// this code is courtesy of Daniel E. White w/ minor modifications by me Thanx Dan
//Dan Code
char[] tagSize = br.ReadChars(4); // I use this to read the bytes in from the file
int[] bytes = new int[4]; // for bit shifting
ulong newSize = 0; // for the final number
// The ID3v2 tag size is encoded with four bytes
// where the most significant bit (bit 7)
// is set to zero in every byte,
// making a total of 28 bits.
// The zeroed bits are ignored
//
// Some bit grinding is necessary. Hang on.
bytes[3] = tagSize[3] | ((tagSize[2] & 1) << 7);
bytes[2] = ((tagSize[2] >> 1) & 63) | ((tagSize[1] & 3) << 6);
bytes[1] = ((tagSize[1] >> 2) & 31) | ((tagSize[0] & 7) << 5);
bytes[0] = ((tagSize[0] >> 3) & 15);
newSize = ((UInt64)10 + (UInt64)bytes[3] |
((UInt64)bytes[2] << 8) |
((UInt64)bytes[1] << 16) |
((UInt64)bytes[0] << 24));
//End Dan Code
this.headerSize = newSize;
}
}
private void ReadExtendedHeader()
{
// Extended header size 4 * %0xxxxxxx
// Number of flag bytes $01
// Extended Flags $xx
// Where the 'Extended header size' is the size of the whole extended header, stored as a 32 bit synchsafe integer.
// read teh size
// this code is courtesy of Daniel E. White w/ minor modifications by me Thanx Dan
//Dan Code
char[] extHeaderSize = br.ReadChars(4); // I use this to read the bytes in from the file
int[] bytes = new int[4]; // for bit shifting
ulong newSize = 0; // for the final number
// The ID3v2 tag size is encoded with four bytes
// where the most significant bit (bit 7)
// is set to zero in every byte,
// making a total of 28 bits.
// The zeroed bits are ignored
//
// Some bit grinding is necessary. Hang on.
bytes[3] = extHeaderSize[3] | ((extHeaderSize[2] & 1) << 7);
bytes[2] = ((extHeaderSize[2] >> 1) & 63) | ((extHeaderSize[1] & 3) << 6);
bytes[1] = ((extHeaderSize[1] >> 2) & 31) | ((extHeaderSize[0] & 7) << 5);
bytes[0] = ((extHeaderSize[0] >> 3) & 15);
newSize = ((UInt64)10 + (UInt64)bytes[3] |
((UInt64)bytes[2] << 8) |
((UInt64)bytes[1] << 16) |
((UInt64)bytes[0] << 24));
//End Dan Code
this.extHeaderSize = newSize;
// next we read the number of flag bytes
this.extNumFlagBytes = System.Convert.ToInt32(br.ReadByte());
// read the flag byte(s) and set the flags
bool[] extFlags = BitReader.ToBitBools(br.ReadBytes(this.extNumFlagBytes));
this.EB_Update = extFlags[1];
this.EC_CRC = extFlags[2];
this.ED_Restrictions = extFlags[3];
// check for flags
if (this.EB_Update)
{
// this tag has no data but will have a null byte so we need to read it in
//Flag data length $00
br.ReadByte();
}
if (this.EC_CRC)
{
// Flag data length $05
// Total frame CRC 5 * %0xxxxxxx
// read the first byte and check to make sure it is 5. if not the header is corrupt
// we will still try to process but we may be funked.
int extC_FlagDataLength = System.Convert.ToInt32(br.ReadByte());
if (extC_FlagDataLength == 5)
{
extHeaderSize = br.ReadChars(5); // I use this to read the bytes in from the file
bytes = new int[4]; // for bit shifting
newSize = 0; // for the final number
// The ID3v2 tag size is encoded with four bytes
// where the most significant bit (bit 7)
// is set to zero in every byte,
// making a total of 28 bits.
// The zeroed bits are ignored
//
// Some bit grinding is necessary. Hang on.
bytes[4] = extHeaderSize[4] | ((extHeaderSize[3] & 1) << 7);
bytes[3] = ((extHeaderSize[3] >> 1) & 63) | ((extHeaderSize[2] & 3) << 6);
bytes[2] = ((extHeaderSize[2] >> 2) & 31) | ((extHeaderSize[1] & 7) << 5);
bytes[1] = ((extHeaderSize[1] >> 3) & 15) | ((extHeaderSize[0] & 15) << 4);
bytes[0] = ((extHeaderSize[0] >> 4) & 7);
newSize = ((UInt64)10 + (UInt64)bytes[4] |
((UInt64)bytes[3] << 8) |
((UInt64)bytes[2] << 16) |
((UInt64)bytes[1] << 24) |
((UInt64)bytes[0] << 32));
this.extHeaderSize = newSize;
}
else
{
// we are f****d. do something
}
}
if (this.ED_Restrictions)
{
// Flag data length $01
//Restrictions %ppqrrstt
// advance past flag data lenght byte
br.ReadByte();
this.extD_Restrictions = br.ReadByte();
}
}
private void ReadHeader( )
{
// bring in the first three bytes. it must be ID3 or we have no tag
// TODO add logic to check the end of the file for "3D1" and other
// possible starting spots
string id3start = new string (br.ReadChars(3));
// check for a tag
if (!id3start.Equals("ID3"))
{
// TODO we are f****d.
//throw id3v2ReaderException;
this.hasTag = false;
return;
}
else
{
this.hasTag = true;
// read id3 version. 2 bytes:
// The first byte of ID3v2 version is it's major version,
// while the second byte is its revision number
this.MajorVersion = System.Convert.ToInt32(br.ReadByte());
this.MinorVersion = System.Convert.ToInt32(br.ReadByte());
//read next byte for flags
bool [] boolar = BitReader.ToBitBool(br.ReadByte());
// set the flags
this.FA_Unsynchronisation = boolar[0];
this.FB_ExtendedHeader = boolar[1];
this.FC_ExperimentalIndicator = boolar[2];
// read teh size
// this code is courtesy of Daniel E. White w/ minor modifications by me Thanx Dan
//Dan Code
char[] tagSize = br.ReadChars(4); // I use this to read the bytes in from the file
int[] bytes = new int[4]; // for bit shifting
ulong newSize = 0; // for the final number
// The ID3v2 tag size is encoded with four bytes
// where the most significant bit (bit 7)
// is set to zero in every byte,
// making a total of 28 bits.
// The zeroed bits are ignored
//
// Some bit grinding is necessary. Hang on.
bytes[3] = tagSize[3] | ((tagSize[2] & 1) << 7);
bytes[2] = ((tagSize[2] >> 1) & 63) | ((tagSize[1] & 3) << 6);
bytes[1] = ((tagSize[1] >> 2) & 31) | ((tagSize[0] & 7) << 5);
bytes[0] = ((tagSize[0] >> 3) & 15);
newSize = ((UInt64)10 + (UInt64)bytes[3] |
((UInt64)bytes[2] << 8) |
((UInt64)bytes[1] << 16) |
((UInt64)bytes[0] << 24));
//End Dan Code
this.headerSize = newSize;
}
}
