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1 // Copyright (c) 2001-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // |
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15 |
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16 #include <e32std.h> |
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17 #include <baflpan.h> |
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18 #include "BADICTIONARYCOMPRESSION.H" |
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19 |
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20 RDictionaryCompressionBitStream::RDictionaryCompressionBitStream() : |
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21 iNumberOfBitsUsedForDictionaryTokens(0), |
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22 iOffsetToFirstBit(-1), |
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23 iOffsetToCurrentBit(-1), |
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24 iOffsetOnePastLastBit(-1), |
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25 iOwnsBitBuffer(EFalse), |
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26 iBuffer(NULL), |
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27 iAssertObj() |
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28 { |
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29 } |
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30 |
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31 void RDictionaryCompressionBitStream::OpenL( |
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32 TInt aNumberOfBitsUsedForDictionaryTokens, |
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33 TInt aOffsetToFirstBit, |
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34 TInt aOffsetOnePastLastBit, |
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35 TBool aTransferringOwnershipOfBuffer, |
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36 TUint8* aBuffer, |
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37 const TBaAssert& aAssertObj) |
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38 { |
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39 iNumberOfBitsUsedForDictionaryTokens = aNumberOfBitsUsedForDictionaryTokens; |
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40 iOffsetToFirstBit = aOffsetToFirstBit; |
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41 iOffsetToCurrentBit = aOffsetToFirstBit; |
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42 iOffsetOnePastLastBit = aOffsetOnePastLastBit; |
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43 iOwnsBitBuffer = aTransferringOwnershipOfBuffer; |
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44 iBuffer = aBuffer; |
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45 iAssertObj = aAssertObj; |
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46 |
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47 iAssertObj.AssertDebL(aBuffer!=NULL,EBafPanicNullPointer); |
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48 iAssertObj.AssertDebL(aOffsetToFirstBit>=0,EBafPanicNegativeOffsetToFirstBit1); |
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49 iAssertObj.AssertDebL(aOffsetToFirstBit<=aOffsetOnePastLastBit,EBafPanicNegativeLengthOfBitBuffer); |
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50 } |
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51 |
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52 void RDictionaryCompressionBitStream::Close() |
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53 { |
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54 if (iOwnsBitBuffer) |
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55 { |
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56 iOwnsBitBuffer=EFalse; |
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57 delete [] iBuffer; |
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58 } |
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59 iBuffer=NULL; |
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60 } |
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61 |
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62 TBool RDictionaryCompressionBitStream::EndOfStreamL() const |
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63 { |
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64 __ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed1)); |
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65 iAssertObj.AssertDebL(iOffsetToFirstBit>=0,EBafPanicNegativeOffsetToFirstBit2); |
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66 iAssertObj.AssertDebL(iOffsetToCurrentBit>=iOffsetToFirstBit,EBafPanicBadCurrentBitPosition1); |
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67 iAssertObj.AssertDebL(iOffsetToCurrentBit<=iOffsetOnePastLastBit,EBafPanicBadCurrentBitPosition2); |
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68 return iOffsetToCurrentBit>=iOffsetOnePastLastBit; |
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69 } |
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70 |
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71 TInt RDictionaryCompressionBitStream::IndexOfDictionaryEntryL() |
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72 { |
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73 // increments the current bit-position if it returns a value >=0; returns KErrNotFound if the next thing in the stream is plain data rather than the index of a dictionary entry |
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74 __ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed2)); |
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75 iAssertObj.AssertDebL(!EndOfStreamL(),EBafPanicEndOfStream1); |
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76 if (!CurrentBitIsOn()) |
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77 { |
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78 ++iOffsetToCurrentBit; |
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79 return ReadIntegerL(iNumberOfBitsUsedForDictionaryTokens); |
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80 } |
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81 return KErrNotFound; |
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82 } |
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83 |
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84 void RDictionaryCompressionBitStream::ReadL(TDes8& aBufferToAppendTo,TBool aCalypsoFileFormat) |
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85 { |
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86 // can only be called if IndexOfDictionaryEntry returned a negative value |
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87 __ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed3)); |
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88 iAssertObj.AssertDebL(!EndOfStreamL(),EBafPanicEndOfStream2); |
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89 TInt numberOfConsecutivePrefixBits=0; |
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90 TInt i; |
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91 for (i=0; i<4; ++i) |
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92 { |
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93 const TBool currentBitIsOn=CurrentBitIsOn(); |
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94 ++iOffsetToCurrentBit; // increment this regardless whether the current bit is on |
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95 if (!currentBitIsOn) |
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96 { |
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97 break; |
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98 } |
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99 ++numberOfConsecutivePrefixBits; |
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100 } |
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101 iAssertObj.AssertDebL(numberOfConsecutivePrefixBits>0,EBafPanicBadNumberOfConsecutivePrefixBits1); |
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102 iAssertObj.AssertDebL(numberOfConsecutivePrefixBits<=4,EBafPanicBadNumberOfConsecutivePrefixBits2); |
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103 TInt numberOfBytesToRead; |
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104 if (numberOfConsecutivePrefixBits==3) |
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105 { |
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106 numberOfBytesToRead=3+ReadIntegerL(3); |
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107 } |
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108 else if (numberOfConsecutivePrefixBits==4) |
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109 { |
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110 numberOfBytesToRead=ReadIntegerL(8); |
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111 if (!aCalypsoFileFormat) |
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112 { |
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113 numberOfBytesToRead+=3+(1<<3); |
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114 } |
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115 } |
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116 else |
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117 { |
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118 numberOfBytesToRead=numberOfConsecutivePrefixBits; |
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119 } |
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120 const TInt numberOfBitsOffByteBoundary=iOffsetToCurrentBit%8; |
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121 const TUint8* currentByte=iBuffer+(iOffsetToCurrentBit/8); |
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122 iAssertObj.AssertDebL( |
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123 (numberOfBytesToRead + aBufferToAppendTo.Length()) <= aBufferToAppendTo.MaxLength(), |
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124 EBafPanicBufLength); |
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125 for (i=0; i<numberOfBytesToRead; ++i, ++currentByte) |
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126 { |
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127 TUint byte=*currentByte; |
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128 iAssertObj.AssertDebL(numberOfBitsOffByteBoundary>=0,EBafPanicBadNumberOfBitsOffByteBoundary1); |
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129 if (numberOfBitsOffByteBoundary>0) |
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130 { |
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131 byte>>=numberOfBitsOffByteBoundary; |
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132 byte|=(*(currentByte+1)<<(8-numberOfBitsOffByteBoundary)); |
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133 byte&=0xff; |
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134 } |
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135 aBufferToAppendTo.Append(byte); |
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136 } |
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137 iOffsetToCurrentBit+=numberOfBytesToRead*8; |
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138 iAssertObj.AssertDebL(numberOfBitsOffByteBoundary==iOffsetToCurrentBit%8,EBafPanicBadNumberOfBitsOffByteBoundary2); |
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139 } |
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140 |
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141 TBool RDictionaryCompressionBitStream::CurrentBitIsOn() const |
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142 { |
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143 // does not increment the current bit-position |
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144 __ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed4)); |
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145 return iBuffer[iOffsetToCurrentBit/8]&(1<<(iOffsetToCurrentBit%8)); |
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146 } |
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147 |
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148 TUint RDictionaryCompressionBitStream::ReadIntegerL(TInt aNumberOfBits) |
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149 { |
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150 // increments the current bit-position |
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151 __ASSERT_DEBUG(iBuffer!=NULL,Panic(EBafPanicNotConstructed5)); |
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152 TInt integer=0; |
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153 TInt numberOfBitsLeftToRead=aNumberOfBits; |
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154 FOREVER |
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155 { |
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156 const TInt offsetToFirstBitToReadInCurrentByte=iOffsetToCurrentBit%8; |
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157 const TInt offsetOnePastLastBitToReadInCurrentByte=Min(8,offsetToFirstBitToReadInCurrentByte+numberOfBitsLeftToRead); |
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158 const TInt numberOfBitsReadFromCurrentByte=offsetOnePastLastBitToReadInCurrentByte-offsetToFirstBitToReadInCurrentByte; |
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159 iAssertObj.AssertDebL(numberOfBitsReadFromCurrentByte>0,EBafPanicBadNumberOfBitsReadFromCurrentByte); |
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160 const TUint bitsReadFromCurrentByte=((iBuffer[iOffsetToCurrentBit/8]>>offsetToFirstBitToReadInCurrentByte)&((1<<numberOfBitsReadFromCurrentByte)-1)); |
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161 integer|=(bitsReadFromCurrentByte<<(aNumberOfBits-numberOfBitsLeftToRead)); |
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162 iOffsetToCurrentBit+=numberOfBitsReadFromCurrentByte; |
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163 numberOfBitsLeftToRead-=numberOfBitsReadFromCurrentByte; |
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164 iAssertObj.AssertDebL(numberOfBitsLeftToRead>=0,EBafPanicBadNumberOfBitsLeftToRead); |
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165 if (numberOfBitsLeftToRead<=0) |
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166 { |
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167 break; |
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168 } |
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169 } |
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170 return integer; |
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171 } |
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172 |