source/layout/OpenTypeUtilities.cpp

/*
 * @(#)OpenTypeUtilities.cpp	1.6 00/03/15
 *
 * (C) Copyright IBM Corp. 1998, 1999, 2000, 2001 - All Rights Reserved
 *
 */

#include "LETypes.h"
#include "OpenTypeTables.h"
#include "OpenTypeUtilities.h"
#include "LESwaps.h"

//
// Finds the high bit by binary searching
// through the bits in n.
//
le_int8 OpenTypeUtilities::highBit(le_int32 value)
{
    if (value <= 0)
    {
        return -32;
    }

    le_uint8 bit = 0;

    if (value >= 1 << 16)
    {
        value >>= 16;
        bit += 16;
    }

    if (value >= 1 << 8)
    {
        value >>= 8;
        bit += 8;
    }

    if (value >= 1 << 4)
    {
        value >>= 4;
        bit += 4;
    }

    if (value >= 1 << 2)
    {
        value >>= 2;
        bit += 2;
    }

    if (value >= 1 << 1)
    {
        value >>= 1;
        bit += 1;
    }

    return bit;
}

Offset OpenTypeUtilities::getTagOffset(LETag tag, const TagAndOffsetRecord *records, le_int32 recordCount)
{
    le_uint8 bit = highBit(recordCount);
    le_int32 power = 1 << bit;
    le_int32 extra = recordCount - power;
    le_int32 probe = power;
    le_int32 index = 0;

    if (SWAPT(records[extra].tag) <= tag)
    {
        index = extra;
    }

    while (probe > (1 << 0))
    {
        probe >>= 1;

        if (SWAPT(records[index + probe].tag) <= tag)
        {
            index += probe;
        }
    }

    if (SWAPT(records[index].tag) == tag)
    {
        return SWAPW(records[index].offset);
    }

    return 0;
}

le_int32 OpenTypeUtilities::getGlyphRangeIndex(LEGlyphID glyphID, const GlyphRangeRecord *records, le_int32 recordCount)
{
    le_uint8 bit = highBit(recordCount);
    le_int32 power = 1 << bit;
    le_int32 extra = recordCount - power;
    le_int32 probe = power;
    le_int32 range = 0;

    if (SWAPW(records[extra].firstGlyph) <= glyphID)
    {
        range = extra;
    }

    while (probe > (1 << 0))
    {
        probe >>= 1;

        if (SWAPW(records[range + probe].firstGlyph) <= glyphID)
        {
            range += probe;
        }
    }

    if (SWAPW(records[range].firstGlyph) <= glyphID && SWAPW(records[range].lastGlyph) >= glyphID)
    {
        return range;
    }

    return -1;
}

le_int32 OpenTypeUtilities::search(le_uint32 value, const le_uint32 array[], le_int32 count)
{
    le_int32 power = 1 << highBit(count);
    le_int32 extra = count - power;
    le_int32 probe = power;
    le_int32 index = 0;

    if (value >= array[extra]) {
        index = extra;
    }

    while (probe > (1 << 0)) {
        probe >>= 1;

        if (value >= array[index + probe]) {
            index += probe;
        }
    }

    return index;
}

le_int32 OpenTypeUtilities::search(le_uint16 value, const le_uint16 array[], le_int32 count)
{
    le_int32 power = 1 << highBit(count);
    le_int32 extra = count - power;
    le_int32 probe = power;
    le_int32 index = 0;

    if (value >= array[extra]) {
        index = extra;
    }

    while (probe > (1 << 0)) {
        probe >>= 1;

        if (value >= array[index + probe]) {
            index += probe;
        }
    }

    return index;
}