icuSources/layout/ScriptAndLanguage.cpp

   1 /*
   2  * (C) Copyright IBM Corp. 1998-2008 - All Rights Reserved
   3  *
   4  */
   5
   6 #include "LETypes.h"
   7 #include "OpenTypeTables.h"
   8 #include "OpenTypeUtilities.h"
   9 #include "ScriptAndLanguage.h"
  10 #include "LESwaps.h"
  11
  12 U_NAMESPACE_BEGIN
  13
  14 const LangSysTable *ScriptTable::findLanguage(LETag languageTag, le_bool exactMatch) const
  15 {
  16     le_uint16 count = SWAPW(langSysCount);
  17     Offset langSysTableOffset = exactMatch? 0 : SWAPW(defaultLangSysTableOffset);
  18
  19     if (count > 0) {
  20         Offset foundOffset =
  21             OpenTypeUtilities::getTagOffset(languageTag, langSysRecordArray, count);
  22
  23         if (foundOffset != 0) {
  24             langSysTableOffset = foundOffset;
  25         }
  26     }
  27
  28     if (langSysTableOffset != 0) {
  29         return (const LangSysTable *) ((char *)this + langSysTableOffset);
  30     }
  31
  32     return NULL;
  33 }
  34
  35 const ScriptTable *ScriptListTable::findScript(LETag scriptTag) const
  36 {
  37     /*
  38      * There are some fonts that have a large, bogus value for scriptCount. To try
  39      * and protect against this, we use the offset in the first scriptRecord,
  40      * which we know has to be past the end of the scriptRecordArray, to compute
  41      * a value which is greater than or equal to the actual script count.
  42      *
  43      * Note: normally, the first offset will point to just after the scriptRecordArray,
  44      * but there's no guarantee of this, only that it's *after* the scriptRecordArray.
  45      * Because of this, a binary serach isn't safe, because the new count may include
  46      * data that's not actually in the scriptRecordArray and hence the array will appear
  47      * to be unsorted.
  48      */
  49     le_uint16 count = SWAPW(scriptCount);
  50     le_uint16 limit = ((SWAPW(scriptRecordArray[0].offset) - sizeof(ScriptListTable)) / sizeof(scriptRecordArray)) + ANY_NUMBER;
  51     Offset scriptTableOffset = 0;
  52
  53     if (count > limit) {
  54         // the scriptCount value is bogus; do a linear search
  55         // because limit may still be too large.
  56         for(le_int32 s = 0; s < limit; s += 1) {
  57             if (SWAPT(scriptRecordArray[s].tag) == scriptTag) {
  58                 scriptTableOffset = SWAPW(scriptRecordArray[s].offset);
  59                 break;
  60             }
  61         }
  62     } else {
  63         scriptTableOffset = OpenTypeUtilities::getTagOffset(scriptTag, scriptRecordArray, count);
  64     }
  65
  66     if (scriptTableOffset != 0) {
  67         return (const ScriptTable *) ((char *)this + scriptTableOffset);
  68     }
  69
  70     return NULL;
  71 }
  72
  73 const LangSysTable *ScriptListTable::findLanguage(LETag scriptTag, LETag languageTag, le_bool exactMatch) const
  74 {
  75     const ScriptTable *scriptTable = findScript(scriptTag);
  76
  77     if (scriptTable == 0) {
  78         return NULL;
  79     }
  80
  81     return scriptTable->findLanguage(languageTag, exactMatch);
  82 }
  83
  84 U_NAMESPACE_END