Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Xml / System / Xml / Base64Decoder.cs / 1 / Base64Decoder.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //[....] //----------------------------------------------------------------------------- using System; using System.Diagnostics; namespace System.Xml { internal class Base64Decoder : IncrementalReadDecoder { // // Fields // byte[] buffer; int startIndex; int curIndex; int endIndex; int bits; int bitsFilled; private static readonly String CharsBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; private static readonly byte[] MapBase64 = ConstructMapBase64(); private const int MaxValidChar = (int)'z'; private const byte Invalid = unchecked((byte)-1); // // IncrementalReadDecoder interface // internal override int DecodedCount { get { return curIndex - startIndex; } } internal override bool IsFull { get { return curIndex == endIndex; } } internal override unsafe int Decode( char[] chars, int startPos, int len ) { Debug.Assert( chars != null ); Debug.Assert( len >= 0 ); Debug.Assert( startPos >= 0 ); Debug.Assert( chars.Length - startPos >= len ); if ( len == 0 ) { return 0; } int bytesDecoded, charsDecoded; fixed ( char* pChars = &chars[startPos] ) { fixed ( byte* pBytes = &buffer[curIndex] ) { Decode( pChars, pChars + len, pBytes, pBytes + ( endIndex - curIndex ), out charsDecoded, out bytesDecoded ); } } curIndex += bytesDecoded; return charsDecoded; } internal override unsafe int Decode( string str, int startPos, int len ) { Debug.Assert( str != null ); Debug.Assert( len >= 0 ); Debug.Assert( startPos >= 0 ); Debug.Assert( str.Length - startPos >= len ); if ( len == 0 ) { return 0; } int bytesDecoded, charsDecoded; fixed ( char* pChars = str ) { fixed ( byte* pBytes = &buffer[curIndex] ) { Decode( pChars + startPos, pChars + startPos + len, pBytes, pBytes + ( endIndex - curIndex ), out charsDecoded, out bytesDecoded ); } } curIndex += bytesDecoded; return charsDecoded; } internal override void Reset() { bitsFilled = 0; bits = 0; } internal override void SetNextOutputBuffer( Array buffer, int index, int count ) { Debug.Assert( buffer != null ); Debug.Assert( count >= 0 ); Debug.Assert( index >= 0 ); Debug.Assert( buffer.Length - index >= count ); Debug.Assert( ( buffer as byte[] ) != null ); this.buffer = (byte[])buffer; this.startIndex = index; this.curIndex = index; this.endIndex = index + count; } // // Private methods // private static byte[] ConstructMapBase64() { byte[] mapBase64 = new byte[MaxValidChar + 1]; for ( int i = 0; i < mapBase64.Length; i++ ) { mapBase64[i]= Invalid; } for ( int i = 0; i < CharsBase64.Length; i++ ) { mapBase64[(int)CharsBase64[i]] = (byte)i; } return mapBase64; } private unsafe void Decode( char* pChars, char* pCharsEndPos, byte* pBytes, byte* pBytesEndPos, out int charsDecoded, out int bytesDecoded ) { #if DEBUG Debug.Assert( pCharsEndPos - pChars >= 0 ); Debug.Assert( pBytesEndPos - pBytes >= 0 ); #endif // walk hex digits pairing them up and shoving the value of each pair into a byte byte *pByte = pBytes; char *pChar = pChars; int b = bits; int bFilled = bitsFilled; XmlCharType xmlCharType = XmlCharType.Instance; while ( pChar < pCharsEndPos && pByte < pBytesEndPos ) { char ch = *pChar; // end? if ( ch == '=' ) { break; } pChar++; // ignore white space if ( ( xmlCharType.charProperties[ch] & XmlCharType.fWhitespace ) != 0 ) { // if ( xmlCharType.IsWhiteSpace(ch) ) { continue; } int digit; if ( ch > 122 || ( digit = MapBase64[ch] ) == Invalid ) { throw new XmlException(Res.Xml_InvalidBase64Value, new string( pChars, 0, (int)(pCharsEndPos - pChars) )); } b = ( b << 6 ) | digit; bFilled += 6; if ( bFilled >= 8 ) { // get top eight valid bits *pByte++ = (byte)( ( b >> ( bFilled - 8 ) ) & 0xFF ); bFilled -= 8; if ( pByte == pBytesEndPos ) { goto Return; } } } if ( pChar < pCharsEndPos && *pChar == '=' ) { bFilled = 0; // ignore padding chars do { pChar++; } while ( pChar < pCharsEndPos && *pChar == '=' ); // ignore whitespace after the padding chars if ( pChar < pCharsEndPos ) { do { if ( !( ( xmlCharType.charProperties[*pChar++] & XmlCharType.fWhitespace ) != 0 ) ) { // if ( !( xmlCharType.IsWhiteSpace( chars[charPos++] ) ) ) { throw new XmlException(Res.Xml_InvalidBase64Value, new string( pChars, 0, (int)( pCharsEndPos - pChars ) )); } } while ( pChar < pCharsEndPos ); } } Return: bits = b; bitsFilled = bFilled; bytesDecoded = (int)(pByte - pBytes); charsDecoded = (int)(pChar - pChars); } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
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