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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
namespace System.Text
{
using System.Runtime.Serialization;
using System.Text;
using System;
using System.Diagnostics.Contracts;
// A Decoder is used to decode a sequence of blocks of bytes into a
// sequence of blocks of characters. Following instantiation of a decoder,
// sequential blocks of bytes are converted into blocks of characters through
// calls to the GetChars method. The decoder maintains state between the
// conversions, allowing it to correctly decode byte sequences that span
// adjacent blocks.
//
// Instances of specific implementations of the Decoder abstract base
// class are typically obtained through calls to the GetDecoder method
// of Encoding objects.
//
[System.Runtime.InteropServices.ComVisible(true)]
[Serializable]
public abstract class Decoder
{
internal DecoderFallback m_fallback = null;
[NonSerialized]
internal DecoderFallbackBuffer m_fallbackBuffer = null;
internal void SerializeDecoder(SerializationInfo info)
{
info.AddValue("m_fallback", this.m_fallback);
}
protected Decoder( )
{
// We don't call default reset because default reset probably isn't good if we aren't initialized.
}
[System.Runtime.InteropServices.ComVisible(false)]
public DecoderFallback Fallback
{
get
{
return m_fallback;
}
set
{
if (value == null)
throw new ArgumentNullException("value");
Contract.EndContractBlock();
// Can't change fallback if buffer is wrong
if (m_fallbackBuffer != null && m_fallbackBuffer.Remaining > 0)
throw new ArgumentException(
Environment.GetResourceString("Argument_FallbackBufferNotEmpty"), "value");
m_fallback = value;
m_fallbackBuffer = null;
}
}
// Note: we don't test for threading here because async access to Encoders and Decoders
// doesn't work anyway.
[System.Runtime.InteropServices.ComVisible(false)]
public DecoderFallbackBuffer FallbackBuffer
{
get
{
if (m_fallbackBuffer == null)
{
if (m_fallback != null)
m_fallbackBuffer = m_fallback.CreateFallbackBuffer();
else
m_fallbackBuffer = DecoderFallback.ReplacementFallback.CreateFallbackBuffer();
}
return m_fallbackBuffer;
}
}
internal bool InternalHasFallbackBuffer
{
get
{
return m_fallbackBuffer != null;
}
}
// Reset the Decoder
//
// Normally if we call GetChars() and an error is thrown we don't change the state of the Decoder. This
// would allow the caller to correct the error condition and try again (such as if they need a bigger buffer.)
//
// If the caller doesn't want to try again after GetChars() throws an error, then they need to call Reset().
//
// Virtual implimentation has to call GetChars with flush and a big enough buffer to clear a 0 byte string
// We avoid GetMaxCharCount() because a) we can't call the base encoder and b) it might be really big.
[System.Runtime.InteropServices.ComVisible(false)]
public virtual void Reset()
{
byte[] byteTemp = {};
char[] charTemp = new char[GetCharCount(byteTemp, 0, 0, true)];
GetChars(byteTemp, 0, 0, charTemp, 0, true);
if (m_fallbackBuffer != null)
m_fallbackBuffer.Reset();
}
// Returns the number of characters the next call to GetChars will
// produce if presented with the given range of bytes. The returned value
// takes into account the state in which the decoder was left following the
// last call to GetChars. The state of the decoder is not affected
// by a call to this method.
//
public abstract int GetCharCount(byte[] bytes, int index, int count);
[System.Runtime.InteropServices.ComVisible(false)]
public virtual int GetCharCount(byte[] bytes, int index, int count, bool flush)
{
return GetCharCount(bytes, index, count);
}
// We expect this to be the workhorse for NLS Encodings, but for existing
// ones we need a working (if slow) default implimentation)
[System.Security.SecurityCritical] // auto-generated
[CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(false)]
public virtual unsafe int GetCharCount(byte* bytes, int count, bool flush)
{
// Validate input parameters
if (bytes == null)
throw new ArgumentNullException("bytes",
Environment.GetResourceString("ArgumentNull_Array"));
if (count < 0)
throw new ArgumentOutOfRangeException("count",
Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
Contract.EndContractBlock();
byte[] arrbyte = new byte[count];
int index;
for (index = 0; index < count; index++)
arrbyte[index] = bytes[index];
return GetCharCount(arrbyte, 0, count);
}
// Decodes a range of bytes in a byte array into a range of characters
// in a character array. The method decodes byteCount bytes from
// bytes starting at index byteIndex, storing the resulting
// characters in chars starting at index charIndex. The
// decoding takes into account the state in which the decoder was left
// following the last call to this method.
//
// An exception occurs if the character array is not large enough to
// hold the complete decoding of the bytes. The GetCharCount method
// can be used to determine the exact number of characters that will be
// produced for a given range of bytes. Alternatively, the
// GetMaxCharCount method of the Encoding that produced this
// decoder can be used to determine the maximum number of characters that
// will be produced for a given number of bytes, regardless of the actual
// byte values.
//
public abstract int GetChars(byte[] bytes, int byteIndex, int byteCount,
char[] chars, int charIndex);
public virtual int GetChars(byte[] bytes, int byteIndex, int byteCount,
char[] chars, int charIndex, bool flush)
{
return GetChars(bytes, byteIndex, byteCount, chars, charIndex);
}
// We expect this to be the workhorse for NLS Encodings, but for existing
// ones we need a working (if slow) default implimentation)
//
// WARNING WARNING WARNING
//
// WARNING: If this breaks it could be a security threat. Obviously we
// call this internally, so you need to make sure that your pointers, counts
// and indexes are correct when you call this method.
//
// In addition, we have internal code, which will be marked as "safe" calling
// this code. However this code is dependent upon the implimentation of an
// external GetChars() method, which could be overridden by a third party and
// the results of which cannot be guaranteed. We use that result to copy
// the char[] to our char* output buffer. If the result count was wrong, we
// could easily overflow our output buffer. Therefore we do an extra test
// when we copy the buffer so that we don't overflow charCount either.
[System.Security.SecurityCritical] // auto-generated
[CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(false)]
public virtual unsafe int GetChars(byte* bytes, int byteCount,
char* chars, int charCount, bool flush)
{
// Validate input parameters
if (chars == null || bytes == null)
throw new ArgumentNullException(chars == null ? "chars" : "bytes",
Environment.GetResourceString("ArgumentNull_Array"));
if (byteCount < 0 || charCount < 0)
throw new ArgumentOutOfRangeException((byteCount<0 ? "byteCount" : "charCount"),
Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
Contract.EndContractBlock();
// Get the byte array to convert
byte[] arrByte = new byte[byteCount];
int index;
for (index = 0; index < byteCount; index++)
arrByte[index] = bytes[index];
// Get the char array to fill
char[] arrChar = new char[charCount];
// Do the work
int result = GetChars(arrByte, 0, byteCount, arrChar, 0, flush);
// The only way this could fail is a bug in GetChars
Contract.Assert(result <= charCount, "Returned more chars than we have space for");
// Copy the char array
// WARNING: We MUST make sure that we don't copy too many chars. We can't
// rely on result because it could be a 3rd party implimentation. We need
// to make sure we never copy more than charCount chars no matter the value
// of result
if (result < charCount)
charCount = result;
// We check both result and charCount so that we don't accidentally overrun
// our pointer buffer just because of any GetChars bug.
for (index = 0; index < charCount; index++)
chars[index] = arrChar[index];
return charCount;
}
// This method is used when the output buffer might not be large enough.
// It will decode until it runs out of bytes, and then it will return
// true if it the entire input was converted. In either case it
// will also return the number of converted bytes and output characters used.
// It will only throw a buffer overflow exception if the entire lenght of chars[] is
// too small to store the next char. (like 0 or maybe 1 or 4 for some encodings)
// We're done processing this buffer only if completed returns true.
//
// Might consider checking Max...Count to avoid the extra counting step.
//
// Note that if all of the input bytes are not consumed, then we'll do a /2, which means
// that its likely that we didn't consume as many bytes as we could have. For some
// applications this could be slow. (Like trying to exactly fill an output buffer from a bigger stream)
[System.Runtime.InteropServices.ComVisible(false)]
public virtual void Convert(byte[] bytes, int byteIndex, int byteCount,
char[] chars, int charIndex, int charCount, bool flush,
out int bytesUsed, out int charsUsed, out bool completed)
{
// Validate parameters
if (bytes == null || chars == null)
throw new ArgumentNullException((bytes == null ? "bytes" : "chars"),
Environment.GetResourceString("ArgumentNull_Array"));
if (byteIndex < 0 || byteCount < 0)
throw new ArgumentOutOfRangeException((byteIndex<0 ? "byteIndex" : "byteCount"),
Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (charIndex < 0 || charCount < 0)
throw new ArgumentOutOfRangeException((charIndex<0 ? "charIndex" : "charCount"),
Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (bytes.Length - byteIndex < byteCount)
throw new ArgumentOutOfRangeException("bytes",
Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
if (chars.Length - charIndex < charCount)
throw new ArgumentOutOfRangeException("chars",
Environment.GetResourceString("ArgumentOutOfRange_IndexCountBuffer"));
Contract.EndContractBlock();
bytesUsed = byteCount;
// Its easy to do if it won't overrun our buffer.
while (bytesUsed > 0)
{
if (GetCharCount(bytes, byteIndex, bytesUsed, flush) <= charCount)
{
charsUsed = GetChars(bytes, byteIndex, bytesUsed, chars, charIndex, flush);
completed = (bytesUsed == byteCount &&
(m_fallbackBuffer == null || m_fallbackBuffer.Remaining == 0));
return;
}
// Try again with 1/2 the count, won't flush then 'cause won't read it all
flush = false;
bytesUsed /= 2;
}
// Oops, we didn't have anything, we'll have to throw an overflow
throw new ArgumentException(Environment.GetResourceString("Argument_ConversionOverflow"));
}
// This is the version that uses *.
// We're done processing this buffer only if completed returns true.
//
// Might consider checking Max...Count to avoid the extra counting step.
//
// Note that if all of the input bytes are not consumed, then we'll do a /2, which means
// that its likely that we didn't consume as many bytes as we could have. For some
// applications this could be slow. (Like trying to exactly fill an output buffer from a bigger stream)
[System.Security.SecurityCritical] // auto-generated
[CLSCompliant(false)]
[System.Runtime.InteropServices.ComVisible(false)]
public virtual unsafe void Convert(byte* bytes, int byteCount,
char* chars, int charCount, bool flush,
out int bytesUsed, out int charsUsed, out bool completed)
{
// Validate input parameters
if (chars == null || bytes == null)
throw new ArgumentNullException(chars == null ? "chars" : "bytes",
Environment.GetResourceString("ArgumentNull_Array"));
if (byteCount < 0 || charCount < 0)
throw new ArgumentOutOfRangeException((byteCount<0 ? "byteCount" : "charCount"),
Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
Contract.EndContractBlock();
// Get ready to do it
bytesUsed = byteCount;
// Its easy to do if it won't overrun our buffer.
while (bytesUsed > 0)
{
if (GetCharCount(bytes, bytesUsed, flush) <= charCount)
{
charsUsed = GetChars(bytes, bytesUsed, chars, charCount, flush);
completed = (bytesUsed == byteCount &&
(m_fallbackBuffer == null || m_fallbackBuffer.Remaining == 0));
return;
}
// Try again with 1/2 the count, won't flush then 'cause won't read it all
flush = false;
bytesUsed /= 2;
}
// Oops, we didn't have anything, we'll have to throw an overflow
throw new ArgumentException(Environment.GetResourceString("Argument_ConversionOverflow"));
}
}
}
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