Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / IO / MemoryStream.cs / 1 / MemoryStream.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== /*============================================================ ** ** Class: MemoryStream ** ** ** Purpose: A Stream whose backing store is memory. Great ** for temporary storage without creating a temp file. Also ** lets users expose a byte[] as a stream. ** ** ===========================================================*/ using System; using System.Runtime.InteropServices; namespace System.IO { // A MemoryStream represents a Stream in memory (ie, it has no backing store). // This stream may reduce the need for temporary buffers and files in // an application. // // There are two ways to create a MemoryStream. You can initialize one // from an unsigned byte array, or you can create an empty one. Empty // memory streams are resizable, while ones created with a byte array provide // a stream "view" of the data. [Serializable] [ComVisible(true)] public class MemoryStream : Stream { private byte[] _buffer; // Either allocated internally or externally. private int _origin; // For user-provided arrays, start at this origin private int _position; // read/write head. private int _length; // Number of bytes within the memory stream private int _capacity; // length of usable portion of buffer for stream // Note that _capacity == _buffer.Length for non-user-provided byte[]'s private bool _expandable; // User-provided buffers aren't expandable. private bool _writable; // Can user write to this stream? private bool _exposable; // Whether the array can be returned to the user. private bool _isOpen; // Is this stream open or closed? // < private const int MemStreamMaxLength = Int32.MaxValue; public MemoryStream() : this(0) { } public MemoryStream(int capacity) { if (capacity < 0) { throw new ArgumentOutOfRangeException("capacity", Environment.GetResourceString("ArgumentOutOfRange_NegativeCapacity")); } _buffer = new byte[capacity]; _capacity = capacity; _expandable = true; _writable = true; _exposable = true; _origin = 0; // Must be 0 for byte[]'s created by MemoryStream _isOpen = true; } public MemoryStream(byte[] buffer) : this(buffer, true) { } public MemoryStream(byte[] buffer, bool writable) { if (buffer == null) throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer")); _buffer = buffer; _length = _capacity = buffer.Length; _writable = writable; _exposable = false; _origin = 0; _isOpen = true; } public MemoryStream(byte[] buffer, int index, int count) : this(buffer, index, count, true, false) { } public MemoryStream(byte[] buffer, int index, int count, bool writable) : this(buffer, index, count, writable, false) { } public MemoryStream(byte[] buffer, int index, int count, bool writable, bool publiclyVisible) { if (buffer==null) throw new ArgumentNullException("buffer", Environment.GetResourceString("ArgumentNull_Buffer")); if (index < 0) throw new ArgumentOutOfRangeException("index", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (count < 0) throw new ArgumentOutOfRangeException("count", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (buffer.Length - index < count) throw new ArgumentException(Environment.GetResourceString("Argument_InvalidOffLen")); _buffer = buffer; _origin = _position = index; _length = _capacity = index + count; _writable = writable; _exposable = publiclyVisible; // Can GetBuffer return the array? _expandable = false; _isOpen = true; } public override bool CanRead { get { return _isOpen; } } public override bool CanSeek { get { return _isOpen; } } public override bool CanWrite { get { return _writable; } } protected override void Dispose(bool disposing) { try { if (disposing) { _isOpen = false; _writable = false; _expandable = false; // Don't set buffer to null - allow GetBuffer & ToArray to work. } } finally { // Call base.Close() to cleanup async IO resources base.Dispose(disposing); } } // returns a bool saying whether we allocated a new array. private bool EnsureCapacity(int value) { // Check for overflow if (value < 0) throw new IOException(Environment.GetResourceString("IO.IO_StreamTooLong")); if (value > _capacity) { int newCapacity = value; if (newCapacity < 256) newCapacity = 256; if (newCapacity < _capacity * 2) newCapacity = _capacity * 2; Capacity = newCapacity; return true; } return false; } public override void Flush() { } public virtual byte[] GetBuffer() { if (!_exposable) throw new UnauthorizedAccessException(Environment.GetResourceString("UnauthorizedAccess_MemStreamBuffer")); return _buffer; } // -------------- PERF: Internal functions for fast direct access of MemoryStream buffer (cf. BinaryReader for usage) --------------- // PERF: Internal sibling of GetBuffer, always returns a buffer (cf. GetBuffer()) internal byte[] InternalGetBuffer() { return _buffer; } // PERF: Get origin and length - used in ResourceWriter. internal void InternalGetOriginAndLength(out int origin, out int length) { if (!_isOpen) __Error.StreamIsClosed(); origin = _origin; length = _length; } // PERF: True cursor position, we don't need _origin for direct access internal int InternalGetPosition() { if (!_isOpen) __Error.StreamIsClosed(); return _position; } // PERF: Takes out Int32 as fast as possible internal int InternalReadInt32() { if (!_isOpen) __Error.StreamIsClosed(); int pos = (_position += 4); // use temp to avoid race if (pos > _length) { _position = _length; __Error.EndOfFile(); } return (int)(_buffer[pos-4] | _buffer[pos-3] << 8 | _buffer[pos-2] << 16 | _buffer[pos-1] << 24); } // PERF: Get actual length of bytes available for read; do sanity checks; shift position - i.e. everything except actual copying bytes internal int InternalEmulateRead(int count) { if (!_isOpen) __Error.StreamIsClosed(); int n = _length - _position; if (n > count) n = count; if (n < 0) n = 0; BCLDebug.Assert(_position + n >= 0, "_position + n >= 0"); // len is less than 2^31 -1. _position += n; return n; } // Gets &; sets the capacity (number of bytes allocated) for this stream. // The capacity cannot be set to a value less than the current length // of the stream. // public virtual int Capacity { get { if (!_isOpen) __Error.StreamIsClosed(); return _capacity - _origin; } set { if (!_isOpen) __Error.StreamIsClosed(); if (value != _capacity) { if (!_expandable) __Error.MemoryStreamNotExpandable(); if (value < _length) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_SmallCapacity")); if (value > 0) { byte[] newBuffer = new byte[value]; if (_length > 0) Buffer.InternalBlockCopy(_buffer, 0, newBuffer, 0, _length); _buffer = newBuffer; } else { _buffer = null; } _capacity = value; } } } public override long Length { get { if (!_isOpen) __Error.StreamIsClosed(); return _length - _origin; } } public override long Position { get { if (!_isOpen) __Error.StreamIsClosed(); return _position - _origin; } set { if (!_isOpen) __Error.StreamIsClosed(); if (value < 0) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum")); if (value > MemStreamMaxLength) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_MemStreamLength")); _position = _origin + (int)value; } } public override int Read([In, Out] byte[] buffer, int offset, int count) { if (!_isOpen) __Error.StreamIsClosed(); 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")); int n = _length - _position; if (n > count) n = count; if (n <= 0) return 0; BCLDebug.Assert(_position + n >= 0, "_position + n >= 0"); // len is less than 2^31 -1. if (n <= 8) { int byteCount = n; while (--byteCount >= 0) buffer[offset + byteCount] = _buffer[_position + byteCount]; } else Buffer.InternalBlockCopy(_buffer, _position, buffer, offset, n); _position += n; return n; } public override int ReadByte() { if (!_isOpen) __Error.StreamIsClosed(); if (_position >= _length) return -1; return _buffer[_position++]; } public override long Seek(long offset, SeekOrigin loc) { if (!_isOpen) __Error.StreamIsClosed(); if (offset > MemStreamMaxLength) throw new ArgumentOutOfRangeException("offset", Environment.GetResourceString("ArgumentOutOfRange_MemStreamLength")); switch(loc) { case SeekOrigin.Begin: if (offset < 0) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position = _origin + (int)offset; break; case SeekOrigin.Current: if (offset + _position < _origin) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position += (int)offset; break; case SeekOrigin.End: if (_length + offset < _origin) throw new IOException(Environment.GetResourceString("IO.IO_SeekBeforeBegin")); _position = _length + (int)offset; break; default: throw new ArgumentException(Environment.GetResourceString("Argument_InvalidSeekOrigin")); } BCLDebug.Assert(_position >= 0, "_position >= 0"); return _position; } // Sets the length of the stream to a given value. The new // value must be nonnegative and less than the space remaining in // the array, Int32.MaxValue - origin // Origin is 0 in all cases other than a MemoryStream created on // top of an existing array and a specific starting offset was passed // into the MemoryStream constructor. The upper bounds prevents any // situations where a stream may be created on top of an array then // the stream is made longer than the maximum possible length of the // array (Int32.MaxValue). // public override void SetLength(long value) { if (!_writable) __Error.WriteNotSupported(); if (value > MemStreamMaxLength) throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_MemStreamLength")); if (value < 0 || value > (Int32.MaxValue - _origin)) { throw new ArgumentOutOfRangeException("value", Environment.GetResourceString("ArgumentOutOfRange_MemStreamLength")); } int newLength = _origin + (int)value; bool allocatedNewArray = EnsureCapacity(newLength); if (!allocatedNewArray && newLength > _length) Array.Clear(_buffer, _length, newLength - _length); _length = newLength; if (_position > newLength) _position = newLength; } public virtual byte[] ToArray() { BCLDebug.Perf(_exposable, "MemoryStream::GetBuffer will let you avoid a copy."); byte[] copy = new byte[_length - _origin]; Buffer.InternalBlockCopy(_buffer, _origin, copy, 0, _length - _origin); return copy; } public override void Write(byte[] buffer, int offset, int count) { if (!_isOpen) __Error.StreamIsClosed(); if (!_writable) __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")); int i = _position + count; // Check for overflow if (i < 0) throw new IOException(Environment.GetResourceString("IO.IO_StreamTooLong")); if (i > _length) { bool mustZero = _position > _length; if (i > _capacity) { bool allocatedNewArray = EnsureCapacity(i); if (allocatedNewArray) mustZero = false; } if (mustZero) Array.Clear(_buffer, _length, i - _length); _length = i; } if (count <= 8) { int byteCount = count; while (--byteCount >= 0) _buffer[_position + byteCount] = buffer[offset + byteCount]; } else Buffer.InternalBlockCopy(buffer, offset, _buffer, _position, count); _position = i; return; } public override void WriteByte(byte value) { if (!_isOpen) __Error.StreamIsClosed(); if (!_writable) __Error.WriteNotSupported(); if (_position >= _length) { int newLength = _position + 1; bool mustZero = _position > _length; if (newLength >= _capacity) { bool allocatedNewArray = EnsureCapacity(newLength); if (allocatedNewArray) mustZero = false; } if (mustZero) Array.Clear(_buffer, _length, _position - _length); _length = newLength; } _buffer[_position++] = value; } // Writes this MemoryStream to another stream. public virtual void WriteTo(Stream stream) { if (!_isOpen) __Error.StreamIsClosed(); if (stream==null) throw new ArgumentNullException("stream", Environment.GetResourceString("ArgumentNull_Stream")); stream.Write(_buffer, _origin, _length - _origin); } } }
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