public VorbisFile(VorbisFile original, VorbisComments replacement)
{
// Extract comments from original file
VorbisHeader commentHeader = original.GetPageHeaders().Select(p => p.GetCommentHeader()).Single(h => h != null);
VorbisCommentsFromFile originalComments = commentHeader.ExtractComments();
// Get new comments header into byte array
byte[] replacementData;
using (var ms = new MemoryStream()) {
replacement.WriteTo(ms);
replacementData = ms.ToArray();
}
if (replacementData.Length + 7 >= 255)
{
throw new Exception("Comment header is too long for this program to handle (must be under 248 bytes)");
}
// Calculate new filesize and allocate memory
this.Length = original.Length
- (int)(originalComments.OrigEnd - originalComments.OrigStart)
+ replacementData.Length;
this.Data = Marshal.AllocHGlobal(this.Length);
// Copy section before comment header
byte *sourcePtr = (byte *)original.Data;
byte *endPtr = sourcePtr + original.Length;
byte *destinationPtr = (byte *)this.Data;
while (sourcePtr < originalComments.OrigStart)
{
*destinationPtr++ = *sourcePtr++;
}
// Copy new comment header
Marshal.Copy(replacementData, 0, (IntPtr)destinationPtr, replacementData.Length);
destinationPtr += replacementData.Length;
// Copy section after comment header
sourcePtr = originalComments.OrigEnd;
while (sourcePtr < endPtr)
{
*destinationPtr++ = *sourcePtr++;
}
if (destinationPtr - this.Length != (byte *)this.Data)
{
throw new Exception("not enough data written");
}
// Update length of segment containing comments
byte *comment_header_segment_table_entry = (byte *)this.Data + (commentHeader.segment_table_entry - (byte *)original.Data);
*comment_header_segment_table_entry = (byte)(replacementData.Length + 7);
// Recalculate all checksums
foreach (OggPage page in GetPageHeaders())
{
page.RecalculateCrc32();
}
}
public unsafe VorbisHeader GetCommentHeader()
{
byte *table = (byte *)Header + 27;
byte *header = table + Header->PageSegments;
for (int i = 0; i < Header->PageSegments; i++)
{
// Don't check a segment if its length is greater than 254 bytes (data is probably split across segments)
if (table[i] < 255)
{
VorbisHeader test = new VorbisHeader(this, &table[i], header);
if (test.PacketType == 3 && test.VorbisTag == "vorbis")
{
return(test);
}
}
header += table[i];
}
return(null);
}
