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