Code:
/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / IO / UnmanagedMemoryStream.cs / 1 / UnmanagedMemoryStream.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: UnmanagedMemoryStream ** ** Purpose: Create a stream over unmanaged memory, mostly ** useful for memory-mapped files. ** ** Date: October 20, 2000 (made public August 4, 2003) ** ===========================================================*/ using System; using System.Runtime.InteropServices; using System.Security.Permissions; namespace System.IO { /* * This class is used to access a contiguous block of memory, likely outside * the GC heap (or pinned in place in the GC heap, but a MemoryStream may * make more sense in those cases). It's great if you have a pointer and * a length for a section of memory mapped in by someone else and you don't * want to copy this into the GC heap. UnmanagedMemoryStream assumes these * two things: * * 1) All the memory in the specified block is readable or writable, * depending on the values you pass to the constructor. * 2) The lifetime of the block of memory is at least as long as the lifetime * of the UnmanagedMemoryStream. * 3) You clean up the memory when appropriate. The UnmanagedMemoryStream * currently will do NOTHING to free this memory. * 4) All calls to Write and WriteByte may not be threadsafe currently. * * It may become necessary to add in some sort of * DeallocationMode enum, specifying whether we unmap a section of memory, * call free, run a user-provided delegate to free the memory, etc etc. * We'll suggest user write a subclass of UnmanagedMemoryStream that uses * a SafeHandle subclass to hold onto the memory. * Check for problems when using this in the negative parts of a * process's address space. We may need to use unsigned longs internally * and change the overflow detection logic. */ [CLSCompliant(false)] public class UnmanagedMemoryStream : Stream { // private const long UnmanagedMemStreamMaxLength = Int64.MaxValue; private unsafe byte* _mem; private long _length; private long _capacity; private long _position; private FileAccess _access; internal bool _isOpen; // Needed for subclasses that need to map a file, etc. protected unsafe UnmanagedMemoryStream() { _mem = null; _isOpen = false; } public unsafe UnmanagedMemoryStream(byte* pointer, long length) { Initialize(pointer, length, length, FileAccess.Read, false); } public unsafe UnmanagedMemoryStream(byte* pointer, long length, long capacity, FileAccess access) { Initialize(pointer, length, capacity, access, false); } // We must create one of these without doing a security check. This // class is created while security is trying to start up. Plus, doing // a Demand from Assembly.GetManifestResourceStream isn't useful. internal unsafe UnmanagedMemoryStream(byte* pointer, long length, long capacity, FileAccess access, bool skipSecurityCheck) { Initialize(pointer, length, capacity, access, skipSecurityCheck); } protected unsafe void Initialize(byte* pointer, long length, long capacity, FileAccess access) { Initialize(pointer, length, capacity, access, false); } internal unsafe void Initialize(byte* pointer, long length, long capacity, FileAccess access, bool skipSecurityCheck) { if (pointer == null) throw new ArgumentNullException("pointer"); if (length < 0 || capacity < 0) throw new ArgumentOutOfRangeException((length < 0) ? "length" : "capacity", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (length > capacity) throw new ArgumentOutOfRangeException("length", Environment.GetResourceString("ArgumentOutOfRange_LengthGreaterThanCapacity")); // Check for wraparound. if (((byte*) ((long)pointer + capacity)) < pointer) throw new ArgumentOutOfRangeException("capacity", Environment.GetResourceString("ArgumentOutOfRange_UnmanagedMemStreamWrapAround")); if (access < FileAccess.Read || access > FileAccess.ReadWrite) throw new ArgumentOutOfRangeException("access", Environment.GetResourceString("ArgumentOutOfRange_Enum")); if (_isOpen) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_CalledTwice")); if (!skipSecurityCheck) new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Demand(); _mem = pointer; _length = length; _capacity = capacity; _access = access; _isOpen = true; } public override bool CanRead { get { return _isOpen && (_access & FileAccess.Read) != 0; } } public override bool CanSeek { get { return _isOpen; } } public override bool CanWrite { get { return _isOpen && (_access & FileAccess.Write) != 0; } } protected override void Dispose(bool disposing) { _isOpen = false; //_mem = null; // Stream allocates WaitHandles for async calls. So for correctness // call base.Dispose(disposing) for better perf, avoiding waiting // for the finalizers to run on those types. base.Dispose(disposing); } public override void Flush() { if (!_isOpen) __Error.StreamIsClosed(); } public override long Length { get { if (!_isOpen) __Error.StreamIsClosed(); return _length; } } public long Capacity { get { if (!_isOpen) __Error.StreamIsClosed(); return _capacity; } } public unsafe override long Position { get { if (!_isOpen) __Error.StreamIsClosed(); return _position; } set { if (!_isOpen) __Error.StreamIsClosed(); if (value < 0) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); #if WIN32 // On 32 bit machines, ensure we don't wrap around. if (value > (long) Int32.MaxValue || _mem + value < _mem) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_MemStreamLength")); #endif _position = value; } } public unsafe byte* PositionPointer { [SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] get { long pos = _position; // Use a temp to avoid a race if (pos > _capacity) throw new IndexOutOfRangeException(Environment.GetResourceString("IndexOutOfRange_UMSPosition")); byte * ptr = _mem + pos; if (!_isOpen) __Error.StreamIsClosed(); return ptr; } [SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] set { if (!_isOpen) __Error.StreamIsClosed(); // Note: subtracting pointers returns an Int64. Working around // to avoid hitting compiler warning CS0652 on this line. if (new IntPtr(value - _mem).ToInt64() > UnmanagedMemStreamMaxLength) throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_UnmanagedMemStreamLength")); if (value < _mem) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position = value - _mem; } } internal unsafe byte* Pointer { get { return _mem; } } public override unsafe int Read([In, Out] byte[] buffer, int offset, int count) { if (!_isOpen) __Error.StreamIsClosed(); if ((_access & FileAccess.Read) == 0) __Error.ReadNotSupported(); if (buffer==null) throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer")); if (offset < 0) throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (count < 0) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (buffer.Length - offset < count) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); // Use a local variable to avoid a race where another thread // changes our position after we decide we can read some bytes. long pos = _position; long n = _length - pos; if (n > count) n = count; if (n <= 0) return 0; int nInt = (int) n; // Safe because n <= count, which is an Int32 if (nInt < 0) nInt = 0; // _position could be beyond EOF BCLDebug.Assert(pos + nInt >= 0, "_position + n >= 0"); // len is less than 2^63 -1. Buffer.memcpy(_mem + pos, 0, buffer, offset, nInt); _position = pos + n; return nInt; } public override unsafe int ReadByte() { if (!_isOpen) __Error.StreamIsClosed(); if ((_access & FileAccess.Read) == 0) __Error.ReadNotSupported(); long pos = _position; // Use a local to avoid a race condition if (pos >= _length) return -1; _position = pos + 1; return _mem[pos]; } public override unsafe long Seek(long offset, SeekOrigin loc) { if (!_isOpen) __Error.StreamIsClosed(); if (offset > UnmanagedMemStreamMaxLength) throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_UnmanagedMemStreamLength")); switch(loc) { case SeekOrigin.Begin: if (offset < 0) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position = offset; break; case SeekOrigin.Current: if (offset + _position < 0) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position += offset; break; case SeekOrigin.End: if (_length + offset < 0) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position = _length + offset; break; default: throw new ArgumentException(Environment.GetResourceString("Argument_InvalidSeekOrigin")); } BCLDebug.Assert(_position >= 0, "_position >= 0"); return _position; } public unsafe override void SetLength(long value) { if (!_isOpen) __Error.StreamIsClosed(); if ((_access & FileAccess.Write) == 0) __Error.WriteNotSupported(); if (value < 0) throw new ArgumentOutOfRangeException("length", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (value > _capacity) throw new IOException(Environment.GetResourceString("IO.IO_FixedCapacity")); long len = _length; if (value > len) Buffer.ZeroMemory(_mem+len, value-len); _length = value; if (_position > value) _position = value; } public override unsafe void Write(byte[] buffer, int offset, int count) { if (!_isOpen) __Error.StreamIsClosed(); if ((_access & FileAccess.Write) == 0) __Error.WriteNotSupported(); if (buffer==null) throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer")); if (offset < 0) throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (count < 0) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (buffer.Length - offset < count) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); long pos = _position; // Use a local to avoid a race condition long len = _length; long n = pos + count; // Check for overflow if (n < 0) throw new IOException(Environment.GetResourceString("IO.IO_StreamTooLong")); if (n > len) { if (n > _capacity) throw new NotSupportedException(Environment.GetResourceString("IO.IO_FixedCapacity")); _length = n; } // Check to see whether we are now expanding the stream and must // zero any memory in the middle. if (pos > len) Buffer.ZeroMemory(_mem+len, pos-len); Buffer.memcpy(buffer, offset, _mem + pos, 0, count); _position = n; return; } public override unsafe void WriteByte(byte value) { if (!_isOpen) __Error.StreamIsClosed(); if ((_access & FileAccess.Write) == 0) __Error.WriteNotSupported(); long pos = _position; // Use a local to avoid a race condition long len = _length; long n = pos + 1; if (pos >= len) { // Check for overflow if (n < 0) throw new IOException(Environment.GetResourceString("IO.IO_StreamTooLong")); if (n > _capacity) throw new NotSupportedException(Environment.GetResourceString("IO.IO_FixedCapacity")); _length = n; // Check to see whether we are now expanding the stream and must // zero any memory in the middle. if (pos > len) Buffer.ZeroMemory(_mem+len, pos-len); } _mem[pos] = value; _position = n; } } }
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