CopyFileEx “The parameter is invalid” error

Question

I\'m writing a (fairly) simple C# application using .NET 4 to check for updates before running an executable. If a newer version of an exe exists on a network share, simply

Answer 1

Instead of calling ReadBytes(), which allocates a new byte[] buffer array on every call, allocate a single buffer (of, say 64KB in size) and call Read(buf, 0, buf.Length), which will read up to buf.Length bytes into the array and then return the actual number of bytes read. Then re-use that same buffer array for every read (after writing out its contents to the target stream). This saves having to re-allocate a new buffer for each read/write operation.

Example

For example, the inner loop of a stream copying method would look something like this:

byte[]  buf;

// Allocate an I/O data buffer
buf = new byte[64*1024];

// Copy the contents of the input stream to the output stream
for (;;)
{
    int     len;

    // Read a block of data from the input stream
    len = inp.ReadBytes(buf, 0, buf.Length);
    if (len <= 0)
        break;

    // Write the data to the output stream
    outp.Write(buf, 0, len);
}

The loop reads up to 64KB of bytes from the input stream into the buffer, then writes out the actual number of bytes read to the output stream. The same buffer is used for each read/write operation, so we're not doing unnecessary allocations and deallocations of buffers. When the read operation fails, we've reached the end of the input stream, so we exit the loop.