icuSources/layout/LookupTables.cpp

   1 /*
   2  *
   3  * (C) Copyright IBM Corp. 1998-2013 - All Rights Reserved
   4  *
   5  */
   6
   7 #include "LETypes.h"
   8 #include "LayoutTables.h"
   9 #include "LookupTables.h"
  10 #include "LESwaps.h"
  11
  12 U_NAMESPACE_BEGIN
  13
  14 /*
  15     These are the rolled-up versions of the uniform binary search.
  16     Someday, if we need more performance, we can un-roll them.
  17
  18     Note: I put these in the base class, so they only have to
  19     be written once. Since the base class doesn't define the
  20     segment table, these routines assume that it's right after
  21     the binary search header.
  22
  23     Another way to do this is to put each of these routines in one
  24     of the derived classes, and implement it in the others by casting
  25     the "this" pointer to the type that has the implementation.
  26 */
  27 const LookupSegment *BinarySearchLookupTable::lookupSegment(const LETableReference &base, const LookupSegment *segments, LEGlyphID glyph, LEErrorCode &success) const
  28 {
  29
  30     le_int16  unity = SWAPW(unitSize);
  31     le_int16  probe = SWAPW(searchRange);
  32     le_int16  extra = SWAPW(rangeShift);
  33     TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph);
  34     LEReferenceTo<LookupSegment> entry(base, success, segments);
  35     LEReferenceTo<LookupSegment> trial(entry, success, extra);
  36
  37     if(LE_FAILURE(success)) return NULL;
  38
  39     if (SWAPW(trial->lastGlyph) <= ttGlyph) {
  40         entry = trial;
  41     }
  42
  43     while (probe > unity && LE_SUCCESS(success)) {
  44         probe >>= 1;
  45         trial = entry; // copy
  46         trial.addOffset(probe, success);
  47
  48         if (SWAPW(trial->lastGlyph) <= ttGlyph) {
  49             entry = trial;
  50         }
  51     }
  52
  53     if (SWAPW(entry->firstGlyph) <= ttGlyph) {
  54       return entry.getAlias();
  55     }
  56
  57     return NULL;
  58 }
  59
  60 const LookupSingle *BinarySearchLookupTable::lookupSingle(const LETableReference &base, const LookupSingle *entries, LEGlyphID glyph, LEErrorCode &success) const
  61 {
  62     le_int16  unity = SWAPW(unitSize);
  63     le_int16  probe = SWAPW(searchRange);
  64     le_int16  extra = SWAPW(rangeShift);
  65     TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph);
  66     LEReferenceTo<LookupSingle> entry(base, success, entries);
  67     LEReferenceTo<LookupSingle> trial(entry, success, extra);
  68
  69     if (SWAPW(trial->glyph) <= ttGlyph) {
  70         entry = trial;
  71     }
  72
  73     while (probe > unity && LE_SUCCESS(success)) {
  74         probe >>= 1;
  75         trial = entry;
  76         trial.addOffset(probe, success);
  77
  78         if (SWAPW(trial->glyph) <= ttGlyph) {
  79             entry = trial;
  80         }
  81     }
  82
  83     if (SWAPW(entry->glyph) == ttGlyph) {
  84       return entry.getAlias();
  85     }
  86
  87     return NULL;
  88 }
  89
  90 U_NAMESPACE_END