87 lines
2.3 KiB
C++
87 lines
2.3 KiB
C++
/*
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* @(#)LookupTables.cpp 1.5 00/03/15
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*
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* (C) Copyright IBM Corp. 1998-2003 - All Rights Reserved
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*
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*/
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#include "LETypes.h"
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#include "LayoutTables.h"
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#include "LookupTables.h"
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#include "LESwaps.h"
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U_NAMESPACE_BEGIN
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/*
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These are the rolled-up versions of the uniform binary search.
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Someday, if we need more performance, we can un-roll them.
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Note: I put these in the base class, so they only have to
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be written once. Since the base class doesn't define the
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segment table, these routines assume that it's right after
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the binary search header.
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Another way to do this is to put each of these routines in one
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of the derived classes, and implement it in the others by casting
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the "this" pointer to the type that has the implementation.
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*/
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const LookupSegment *BinarySearchLookupTable::lookupSegment(const LookupSegment *segments, LEGlyphID glyph) const
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{
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le_int16 unity = SWAPW(unitSize);
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le_int16 probe = SWAPW(searchRange);
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le_int16 extra = SWAPW(rangeShift);
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TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph);
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const LookupSegment *entry = segments;
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const LookupSegment *trial = (const LookupSegment *) ((char *) entry + extra);
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if (SWAPW(trial->lastGlyph) <= ttGlyph) {
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entry = trial;
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}
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while (probe > unity) {
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probe >>= 1;
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trial = (const LookupSegment *) ((char *) entry + probe);
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if (SWAPW(trial->lastGlyph) <= ttGlyph) {
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entry = trial;
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}
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}
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if (SWAPW(entry->firstGlyph) <= ttGlyph) {
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return entry;
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}
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return NULL;
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}
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const LookupSingle *BinarySearchLookupTable::lookupSingle(const LookupSingle *entries, LEGlyphID glyph) const
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{
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le_int16 unity = SWAPW(unitSize);
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le_int16 probe = SWAPW(searchRange);
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le_int16 extra = SWAPW(rangeShift);
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TTGlyphID ttGlyph = (TTGlyphID) LE_GET_GLYPH(glyph);
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const LookupSingle *entry = entries;
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const LookupSingle *trial = (const LookupSingle *) ((char *) entry + extra);
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if (SWAPW(trial->glyph) <= ttGlyph) {
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entry = trial;
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}
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while (probe > unity) {
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probe >>= 1;
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trial = (const LookupSingle *) ((char *) entry + probe);
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if (SWAPW(trial->glyph) <= ttGlyph) {
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entry = trial;
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}
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}
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if (SWAPW(entry->glyph) == ttGlyph) {
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return entry;
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}
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return NULL;
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}
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U_NAMESPACE_END
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