1 // 2016 and later: Unicode, Inc. and others. 2 // License & terms of use: http://www.unicode.org/copyright.html#License 3 /* 4 ******************************************************************************* 5 * Copyright (C) 2006-2015, International Business Machines Corporation and 6 * others. All Rights Reserved. 7 ******************************************************************************* 8 */ 9 10 package com.ibm.icu.charset; 11 12 import java.io.IOException; 13 import java.nio.ByteBuffer; 14 15 import com.ibm.icu.impl.ICUBinary; 16 17 18 /* Format of cnvalias.icu ----------------------------------------------------- 19 * 20 * cnvalias.icu is a binary, memory-mappable form of convrtrs.txt. 21 * This binary form contains several tables. All indexes are to uint16_t 22 * units, and not to the bytes (uint8_t units). Addressing everything on 23 * 16-bit boundaries allows us to store more information with small index 24 * numbers, which are also 16-bit in size. The majority of the table (except 25 * the string table) are 16-bit numbers. 26 * 27 * First there is the size of the Table of Contents (TOC). The TOC 28 * entries contain the size of each section. In order to find the offset 29 * you just need to sum up the previous offsets. 30 * The TOC length and entries are an array of uint32_t values. 31 * The first section after the TOC starts immediately after the TOC. 32 * 33 * 1) This section contains a list of converters. This list contains indexes 34 * into the string table for the converter name. The index of this list is 35 * also used by other sections, which are mentioned later on. 36 * This list is not sorted. 37 * 38 * 2) This section contains a list of tags. This list contains indexes 39 * into the string table for the tag name. The index of this list is 40 * also used by other sections, which are mentioned later on. 41 * This list is in priority order of standards. 42 * 43 * 3) This section contains a list of sorted unique aliases. This 44 * list contains indexes into the string table for the alias name. The 45 * index of this list is also used by other sections, like the 4th section. 46 * The index for the 3rd and 4th section is used to get the 47 * alias -> converter name mapping. Section 3 and 4 form a two column table. 48 * 49 * 4) This section contains a list of mapped converter names. Consider this 50 * as a table that maps the 3rd section to the 1st section. This list contains 51 * indexes into the 1st section. The index of this list is the same index in 52 * the 3rd section. There is also some extra information in the high bits of 53 * each converter index in this table. Currently it's only used to say that 54 * an alias mapped to this converter is ambiguous. See UCNV_CONVERTER_INDEX_MASK 55 * and UCNV_AMBIGUOUS_ALIAS_MAP_BIT for more information. This section is 56 * the predigested form of the 5th section so that an alias lookup can be fast. 57 * 58 * 5) This section contains a 2D array with indexes to the 6th section. This 59 * section is the full form of all alias mappings. The column index is the 60 * index into the converter list (column header). The row index is the index 61 * to tag list (row header). This 2D array is the top part a 3D array. The 62 * third dimension is in the 6th section. 63 * 64 * 6) This is blob of variable length arrays. Each array starts with a size, 65 * and is followed by indexes to alias names in the string table. This is 66 * the third dimension to the section 5. No other section should be referencing 67 * this section. 68 * 69 * 7) Reserved at this time (There is no information). This _usually_ has a 70 * size of 0. Future versions may add more information here. 71 * 72 * 8) This is the string table. All strings are indexed on an even address. 73 * There are two reasons for this. First many chip architectures locate strings 74 * faster on even address boundaries. Second, since all indexes are 16-bit 75 * numbers, this string table can be 128KB in size instead of 64KB when we 76 * only have strings starting on an even address. 77 * 78 * 79 * Here is the concept of section 5 and 6. It's a 3D cube. Each tag 80 * has a unique alias among all converters. That same alias can 81 * be mentioned in other standards on different converters, 82 * but only one alias per tag can be unique. 83 * 84 * 85 * Converter Names (Usually in TR22 form) 86 * -------------------------------------------. 87 * T / /| 88 * a / / | 89 * g / / | 90 * s / / | 91 * / / | 92 * ------------------------------------------/ | 93 * A | | | 94 * l | | | 95 * i | | / 96 * a | | / 97 * s | | / 98 * e | | / 99 * s | |/ 100 * ------------------------------------------- 101 * 102 * 103 * 104 * Here is what it really looks like. It's like swiss cheese. 105 * There are holes. Some converters aren't recognized by 106 * a standard, or they are really old converters that the 107 * standard doesn't recognize anymore. 108 * 109 * Converter Names (Usually in TR22 form) 110 * -------------------------------------------. 111 * T /##########################################/| 112 * a / # # /# 113 * g / # ## ## ### # ### ### ### #/ 114 * s / # ##### #### ## ## #/# 115 * / ### # # ## # # # ### # # #/## 116 * ------------------------------------------/# # 117 * A |### # # ## # # # ### # # #|# # 118 * l |# # # # # ## # #|# # 119 * i |# # # # # # #|# 120 * a |# #|# 121 * s | #|# 122 * e 123 * s 124 * 125 */ 126 127 final class UConverterAliasDataReader implements ICUBinary.Authenticate { 128 // private final static boolean debug = ICUDebug.enabled("UConverterAliasDataReader"); 129 130 /** 131 * <p>Protected constructor.</p> 132 * @param bytes ICU uprop.dat file buffer 133 * @exception IOException throw if data file fails authentication 134 */ 135 protected UConverterAliasDataReader(ByteBuffer bytes) 136 throws IOException{ 137 //if(debug) System.out.println("Bytes in buffer " + bytes.remaining()); 138 139 byteBuffer = bytes; 140 /*unicodeVersion = */ICUBinary.readHeader(byteBuffer, DATA_FORMAT_ID, this); 141 142 //if(debug) System.out.println("Bytes left in byteBuffer " + byteBuffer.remaining()); 143 } 144 145 // protected methods ------------------------------------------------- 146 147 protected int[] readToc(int n)throws IOException 148 { 149 //Read the toc 150 return ICUBinary.getInts(byteBuffer, n, 0); 151 } 152 153 @Override 154 public boolean isDataVersionAcceptable(byte version[]) 155 { 156 return version.length >= DATA_FORMAT_VERSION.length 157 && version[0] == DATA_FORMAT_VERSION[0] 158 && version[1] == DATA_FORMAT_VERSION[1] 159 && version[2] == DATA_FORMAT_VERSION[2]; 160 } 161 162 /*byte[] getUnicodeVersion(){ 163 return ICUBinary.getVersionByteArrayFromCompactInt(unicodeVersion); 164 }*/ 165 // private data members ------------------------------------------------- 166 167 168 /** 169 * ICU data file buffer 170 */ 171 private ByteBuffer byteBuffer; 172 173 // private int unicodeVersion; 174 175 /** 176 * File format version that this class understands. 177 * No guarantees are made if a older version is used 178 * see store.c of gennorm for more information and values 179 */ 180 // DATA_FORMAT_ID_ values taken from icu4c isAcceptable (ucnv_io.c) 181 private static final int DATA_FORMAT_ID = 0x4376416c; // dataFormat="CvAl" 182 private static final byte DATA_FORMAT_VERSION[] = {3, 0, 1}; 183 } 184
