/// <summary>
/// Create a memory map instance that views can be opened from, for reading.
/// </summary>
/// <param name="fileName">name of the backing file</param>
/// <exception cref="IOException">Memory mapping failed at the Win32 layer</exception>
/// <returns>A Stream for a view on the file</returns>
public static Stream MemoryMappedStream(string fileName)
{
using (MemoryMappedFile mmf = new MemoryMappedFile(fileName))
{
return mmf.MapView();
}
}
/// <summary>
/// Create a memory map instance that views can be opened from.
/// </summary>
/// <param name="fileName">name of the backing file (or null for a pagefile-backed map)</param>
/// <param name="write">if true, write access is allowed; if false, it is read-only</param>
/// <param name="writeCopy">if true, copy on write; if false, write to original memory</param>
/// <exception cref="IOException">Memory mapping failed at the Win32 layer</exception>
/// <returns>A Stream for a view on the file</returns>
public static Stream MemoryMappedStream(string fileName, bool write, bool writeCopy)
{
using (MemoryMappedFile mmf = new MemoryMappedFile(fileName, write, writeCopy))
{
return mmf.MapView();
}
}
private static Stream _ConstructorInit(string filename, bool mmapFile)
{
Stream stream = null;
bool mmapAble = true;
// the MemoryMappedFile object doesn't handle files > 4GB
FileInfo fi = new FileInfo(filename);
if (fi.Length >= uint.MaxValue) mmapAble = false;
if (!mmapFile) {
Stream fs = ZStreamIn.Open(filename);
//Stream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
try {
byte[] buffer = new byte[fs.Length];
fs.Read(buffer, 0, (int)fs.Length);
stream = new MemoryStream(buffer);
}
catch {
stream = null;
}
}
// either malloc failed or we wanted to mmap from the start
MemoryMappedFile mmap = null;
if (stream == null && mmapAble) {
try {
mmap = new MemoryMappedFile(filename);
if (mmap != null) stream = mmap.MapView();
} catch {
if (mmap != null) mmap.Dispose();
}
}
// we failed at mmap so open a filestream
if (stream == null) {
#if NAMEDPIPEMODE
stream = ZStreamIn.Open(filename);
#else
stream = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
#endif
}
return stream;
}
