/// <summary>Sets the current position of this stream to the given value.</summary>
/// <param name="offset">The point relative to origin from which to begin seeking. </param>
/// <param name="origin">
/// Specifies the beginning, the end, or the current position as a reference
/// point for offset, using a value of type SeekOrigin.
/// </param>
/// <returns>The new position in the stream.</returns>
public override long Seek(long offset, SeekOrigin origin)
{
if (origin < SeekOrigin.Begin || origin > SeekOrigin.End)
{
throw new ArgumentException(SR.Argument_InvalidSeekOrigin, nameof(origin));
}
if (_fileHandle.IsClosed)
{
throw Error.GetFileNotOpen();
}
if (!CanSeek)
{
throw Error.GetSeekNotSupported();
}
VerifyOSHandlePosition();
// Flush our write/read buffer. FlushWrite will output any write buffer we have and reset _bufferWritePos.
// We don't call FlushRead, as that will do an unnecessary seek to rewind the read buffer, and since we're
// about to seek and update our position, we can simply update the offset as necessary and reset our read
// position and length to 0. (In the future, for some simple cases we could potentially add an optimization
// here to just move data around in the buffer for short jumps, to avoid re-reading the data from disk.)
FlushWriteBuffer();
if (origin == SeekOrigin.Current)
{
offset -= (_readLength - _readPos);
}
_readPos = _readLength = 0;
// Keep track of where we were, in case we're in append mode and need to verify
long oldPos = 0;
if (_appendStart >= 0)
{
oldPos = SeekCore(_fileHandle, 0, SeekOrigin.Current);
}
// Jump to the new location
long pos = SeekCore(_fileHandle, offset, origin);
// Prevent users from overwriting data in a file that was opened in append mode.
if (_appendStart != -1 && pos < _appendStart)
{
SeekCore(_fileHandle, oldPos, SeekOrigin.Begin);
throw new IOException(SR.IO_SeekAppendOverwrite);
}
// Return the new position
return(pos);
}
/// <summary>Sets the length of this stream to the given value.</summary>
/// <param name="value">The new length of the stream.</param>
public override void SetLength(long value)
{
if (value < 0)
{
throw new ArgumentOutOfRangeException(nameof(value), SR.ArgumentOutOfRange_NeedNonNegNum);
}
if (_fileHandle.IsClosed)
{
throw Error.GetFileNotOpen();
}
if (!CanSeek)
{
throw Error.GetSeekNotSupported();
}
if (!CanWrite)
{
throw Error.GetWriteNotSupported();
}
SetLengthInternal(value);
}
public sealed override long Seek(long offset, SeekOrigin origin)
{
throw Error.GetSeekNotSupported();
}
public sealed override void SetLength(long value)
{
throw Error.GetSeekNotSupported();
}
