1 /* 2 * 3 * (C) Copyright IBM Corp. 1998-2004 - 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 LookupSegment *segments, LEGlyphID glyph) const 28 { 29 le_int16 unity = SWAPW(unitSize); 30 le_int16 probe = SWAPW(searchRange); 31 le_int16 extra = SWAPW(rangeShift); 32 TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph); 33 const LookupSegment *entry = segments; 34 const LookupSegment *trial = (const LookupSegment *) ((char *) entry + extra); 35 36 if (SWAPW(trial->lastGlyph) <= ttGlyph) { 37 entry = trial; 38 } 39 40 while (probe > unity) { 41 probe >>= 1; 42 trial = (const LookupSegment *) ((char *) entry + probe); 43 44 if (SWAPW(trial->lastGlyph) <= ttGlyph) { 45 entry = trial; 46 } 47 } 48 49 if (SWAPW(entry->firstGlyph) <= ttGlyph) { 50 return entry; 51 } 52 53 return NULL; 54 } 55 56 const LookupSingle *BinarySearchLookupTable::lookupSingle(const LookupSingle *entries, LEGlyphID glyph) const 57 { 58 le_int16 unity = SWAPW(unitSize); 59 le_int16 probe = SWAPW(searchRange); 60 le_int16 extra = SWAPW(rangeShift); 61 TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph); 62 const LookupSingle *entry = entries; 63 const LookupSingle *trial = (const LookupSingle *) ((char *) entry + extra); 64 65 if (SWAPW(trial->glyph) <= ttGlyph) { 66 entry = trial; 67 } 68 69 while (probe > unity) { 70 probe >>= 1; 71 trial = (const LookupSingle *) ((char *) entry + probe); 72 73 if (SWAPW(trial->glyph) <= ttGlyph) { 74 entry = trial; 75 } 76 } 77 78 if (SWAPW(entry->glyph) == ttGlyph) { 79 return entry; 80 } 81 82 return NULL; 83 } 84 85 U_NAMESPACE_END 86
