Code:
/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Text / Decoder.cs / 1 / Decoder.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== namespace System.Text { using System.Runtime.Serialization; using System.Text; using System; // 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"); // 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) [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")); 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. [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")); // 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 BCLDebug.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")); 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) [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")); // 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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