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1 // Copyright (c) 1998-2009 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 // e32tools\petran\Szip\huffman.h |
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15 // |
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16 // |
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17 |
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18 #ifndef __HUFFMAN_H__ |
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19 #define __HUFFMAN_H__ |
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20 |
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21 #include <e32std.h> |
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22 |
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23 /** Bit output stream. |
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24 Good for writing bit streams for packed, compressed or huffman data algorithms. |
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25 |
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26 This class must be derived from and OverflowL() reimplemented if the bitstream data |
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27 cannot be generated into a single memory buffer. |
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28 |
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29 @since 8.0 |
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30 @library euser.lib |
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31 */ |
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32 class TBitOutput |
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33 { |
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34 public: |
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35 TBitOutput(); |
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36 TBitOutput(TUint8* aBuf,TInt aSize); |
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37 inline virtual ~TBitOutput() { } |
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38 inline void Set(TUint8* aBuf,TInt aSize); |
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39 inline const TUint8* Ptr() const; |
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40 inline TInt BufferedBits() const; |
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41 // |
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42 void WriteL(TUint aValue, TInt aLength); |
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43 void HuffmanL(TUint aHuffCode); |
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44 void PadL(TUint aPadding); |
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45 private: |
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46 void DoWriteL(TUint aBits, TInt aSize); |
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47 virtual void OverflowL(); |
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48 private: |
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49 TUint iCode; // code in production |
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50 TInt iBits; |
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51 TUint8* iPtr; |
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52 TUint8* iEnd; |
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53 }; |
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54 |
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55 /** Set the memory buffer to use for output |
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56 |
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57 Data will be written to this buffer until it is full, at which point OverflowL() will |
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58 be called. This should handle the data and then can Set() again to reset the buffer |
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59 for further output. |
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60 |
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61 @param "TUint8* aBuf" The buffer for output |
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62 @param "TInt aSize" The size of the buffer in bytes |
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63 */ |
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64 inline void TBitOutput::Set(TUint8* aBuf,TInt aSize) |
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65 {iPtr=aBuf;iEnd=aBuf+aSize;} |
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66 /** Get the current write position in the output buffer |
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67 |
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68 In conjunction with the address of the buffer, which should be known to the |
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69 caller, this describes the data in the bitstream. |
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70 */ |
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71 inline const TUint8* TBitOutput::Ptr() const |
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72 {return iPtr;} |
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73 /** Get the number of bits that are buffered |
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74 |
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75 This reports the number of bits that have not yet been written into the |
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76 output buffer. It will always lie in the range 0..7. Use PadL() to |
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77 pad the data out to the next byte and write it to the buffer. |
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78 */ |
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79 inline TInt TBitOutput::BufferedBits() const |
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80 {return iBits+8;} |
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81 |
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82 |
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83 /** Bit input stream. |
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84 Good for reading bit streams for packed, compressed or huffman data algorithms. |
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85 @since 8.0 |
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86 @library euser.lib |
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87 */ |
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88 class TBitInput |
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89 { |
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90 public: |
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91 TBitInput(); |
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92 TBitInput(const TUint8* aPtr, TInt aLength, TInt aOffset=0); |
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93 void Set(const TUint8* aPtr, TInt aLength, TInt aOffset=0); |
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94 inline virtual ~TBitInput() { } |
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95 TUint ReadL(); |
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96 TUint ReadL(TInt aSize); |
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97 TUint HuffmanL(const TUint32* aTree); |
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98 private: |
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99 virtual void UnderflowL(); |
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100 private: |
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101 TInt iCount; |
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102 TUint iBits; |
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103 TInt iRemain; |
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104 const TUint32* iPtr; |
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105 }; |
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106 |
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107 /** Huffman code toolkit. |
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108 |
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109 This class builds a huffman encoding from a frequency table and builds |
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110 a decoding tree from a code-lengths table |
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111 |
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112 The encoding generated is based on the rule that given two symbols s1 and s2, with |
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113 code length l1 and l2, and huffman codes h1 and h2: |
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114 |
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115 if l1<l2 then h1<h2 when compared lexicographically |
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116 if l1==l2 and s1<s2 then h1<h2 ditto |
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117 |
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118 This allows the encoding to be stored compactly as a table of code lengths |
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119 |
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120 @since 8.0 |
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121 @library euser.lib |
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122 */ |
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123 class Huffman |
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124 { |
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125 public: |
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126 enum {KMaxCodeLength=27}; |
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127 enum {KMetaCodes=KMaxCodeLength+1}; |
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128 enum {KMaxCodes=0x8000}; |
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129 public: |
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130 static void HuffmanL(const TUint32 aFrequency[],TInt aNumCodes,TUint32 aHuffman[]); |
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131 static void Encoding(const TUint32 aHuffman[],TInt aNumCodes,TUint32 aEncodeTable[]); |
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132 static void Decoding(const TUint32 aHuffman[],TInt aNumCodes,TUint32 aDecodeTree[],TInt aSymbolBase=0); |
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133 static TBool IsValid(const TUint32 aHuffman[],TInt aNumCodes); |
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134 // |
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135 static void ExternalizeL(TBitOutput& aOutput,const TUint32 aHuffman[],TInt aNumCodes); |
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136 static void InternalizeL(TBitInput& aInput,TUint32 aHuffman[],TInt aNumCodes); |
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137 }; |
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138 |
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139 #endif |
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140 |