icu4c/source/layout/LigatureSubstProc.cpp

/*
 *
 * (C) Copyright IBM Corp. 1998-2013 - All Rights Reserved
 *
 */

#include "LETypes.h"
#include "MorphTables.h"
#include "StateTables.h"
#include "MorphStateTables.h"
#include "SubtableProcessor.h"
#include "StateTableProcessor.h"
#include "LigatureSubstProc.h"
#include "LEGlyphStorage.h"
#include "LESwaps.h"

U_NAMESPACE_BEGIN

#define ExtendedComplement(m) ((le_int32) (~((le_uint32) (m))))
#define SignBit(m) ((ExtendedComplement(m) >> 1) & (le_int32)(m))
#define SignExtend(v,m) (((v) & SignBit(m))? ((v) | ExtendedComplement(m)): (v))

UOBJECT_DEFINE_RTTI_IMPLEMENTATION(LigatureSubstitutionProcessor)

  LigatureSubstitutionProcessor::LigatureSubstitutionProcessor(const LEReferenceTo<MorphSubtableHeader> &morphSubtableHeader, LEErrorCode &success)
: StateTableProcessor(morphSubtableHeader, success), ligatureSubstitutionHeader(morphSubtableHeader, success)
{
    if(LE_FAILURE(success)) return;
    ligatureActionTableOffset = SWAPW(ligatureSubstitutionHeader->ligatureActionTableOffset);
    componentTableOffset = SWAPW(ligatureSubstitutionHeader->componentTableOffset);
    ligatureTableOffset = SWAPW(ligatureSubstitutionHeader->ligatureTableOffset);

    entryTable = LEReferenceToArrayOf<LigatureSubstitutionStateEntry>(stHeader, success, entryTableOffset, LE_UNBOUNDED_ARRAY);
}

LigatureSubstitutionProcessor::~LigatureSubstitutionProcessor()
{
}

void LigatureSubstitutionProcessor::beginStateTable()
{
    m = -1;
}

ByteOffset LigatureSubstitutionProcessor::processStateEntry(LEGlyphStorage &glyphStorage, le_int32 &currGlyph, EntryTableIndex index)
{
  LEErrorCode success = LE_NO_ERROR;
  const LigatureSubstitutionStateEntry *entry = entryTable.getAlias(index, success);

    ByteOffset newState = SWAPW(entry->newStateOffset);
    le_int16 flags = SWAPW(entry->flags);

    if (flags & lsfSetComponent) {
        if (++m >= nComponents) {
            m = 0;
        }

        componentStack[m] = currGlyph;
    } else if ( m == -1) {
        // bad font- skip this glyph.
        currGlyph++;
        return newState;
    }

    ByteOffset actionOffset = flags & lsfActionOffsetMask;

    if (actionOffset != 0) {
      LEReferenceTo<LigatureActionEntry> ap(stHeader, success, actionOffset);
        LigatureActionEntry action;
        le_int32 offset, i = 0;
        le_int32 stack[nComponents];
        le_int16 mm = -1;

        do {
            le_uint32 componentGlyph = componentStack[m--];

            action = SWAPL(*ap.getAlias());
            ap.addObject(success); // ap++

            if (m < 0) {
                m = nComponents - 1;
            }

            offset = action & lafComponentOffsetMask;
            if (offset != 0) {
              LEReferenceToArrayOf<le_int16> offsetTable(stHeader, success, 2 * SignExtend(offset, lafComponentOffsetMask), LE_UNBOUNDED_ARRAY);

              if(LE_FAILURE(success)) {
                  currGlyph++;
                  LE_DEBUG_BAD_FONT("off end of ligature substitution header");
                  return newState; // get out! bad font
              }
              if(componentGlyph > (le_uint32)glyphStorage.getGlyphCount()) {
                LE_DEBUG_BAD_FONT("preposterous componentGlyph");
                currGlyph++;
                return newState; // get out! bad font
              }
              i += SWAPW(offsetTable.getObject(LE_GET_GLYPH(glyphStorage[componentGlyph]), success));

                if (action & (lafLast | lafStore))  {
                  LEReferenceTo<TTGlyphID> ligatureOffset(stHeader, success, i);
                  TTGlyphID ligatureGlyph = SWAPW(*ligatureOffset.getAlias());

                  glyphStorage[componentGlyph] = LE_SET_GLYPH(glyphStorage[componentGlyph], ligatureGlyph);
                  if(mm==nComponents) {
                    LE_DEBUG_BAD_FONT("exceeded nComponents");
                    mm--; // don't overrun the stack.
                  }
                  stack[++mm] = componentGlyph;
                  i = 0;
                } else {
                  glyphStorage[componentGlyph] = LE_SET_GLYPH(glyphStorage[componentGlyph], 0xFFFF);
                }
            }
#if LE_ASSERT_BAD_FONT
            if(m<0) {
              LE_DEBUG_BAD_FONT("m<0")
            }
#endif
        } while (!(action & lafLast)  && (m>=0) ); // stop if last bit is set, or if run out of items

        while (mm >= 0) {
          if (++m >= nComponents) {
            m = 0;
          }
          
          componentStack[m] = stack[mm--];
        }
    }

    if (!(flags & lsfDontAdvance)) {
        // should handle reverse too!
        currGlyph += 1;
    }

    return newState;
}

void LigatureSubstitutionProcessor::endStateTable()
{
}

U_NAMESPACE_END