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import AATLookupTable from './AATLookupTable';
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const START_OF_TEXT_STATE = 0;
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const START_OF_LINE_STATE = 1;
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const END_OF_TEXT_CLASS = 0;
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const OUT_OF_BOUNDS_CLASS = 1;
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const DELETED_GLYPH_CLASS = 2;
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const END_OF_LINE_CLASS = 3;
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const DONT_ADVANCE = 0x4000;
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export default class AATStateMachine {
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constructor(stateTable) {
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this.stateTable = stateTable;
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this.lookupTable = new AATLookupTable(stateTable.classTable);
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}
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process(glyphs, reverse, processEntry) {
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let currentState = START_OF_TEXT_STATE; // START_OF_LINE_STATE is used for kashida glyph insertions sometimes I think?
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let index = reverse ? glyphs.length - 1 : 0;
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let dir = reverse ? -1 : 1;
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while ((dir === 1 && index <= glyphs.length) || (dir === -1 && index >= -1)) {
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let glyph = null;
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let classCode = OUT_OF_BOUNDS_CLASS;
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let shouldAdvance = true;
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if (index === glyphs.length || index === -1) {
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classCode = END_OF_TEXT_CLASS;
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} else {
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glyph = glyphs[index];
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if (glyph.id === 0xffff) { // deleted glyph
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classCode = DELETED_GLYPH_CLASS;
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} else {
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classCode = this.lookupTable.lookup(glyph.id);
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if (classCode == null) {
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classCode = OUT_OF_BOUNDS_CLASS;
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}
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}
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}
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let row = this.stateTable.stateArray.getItem(currentState);
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let entryIndex = row[classCode];
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let entry = this.stateTable.entryTable.getItem(entryIndex);
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if (classCode !== END_OF_TEXT_CLASS && classCode !== DELETED_GLYPH_CLASS) {
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processEntry(glyph, entry, index);
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shouldAdvance = !(entry.flags & DONT_ADVANCE);
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}
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currentState = entry.newState;
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if (shouldAdvance) {
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index += dir;
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}
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}
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return glyphs;
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}
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/**
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* Performs a depth-first traversal of the glyph strings
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* represented by the state machine.
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*/
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traverse(opts, state = 0, visited = new Set) {
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if (visited.has(state)) {
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return;
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}
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visited.add(state);
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let {nClasses, stateArray, entryTable} = this.stateTable;
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let row = stateArray.getItem(state);
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// Skip predefined classes
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for (let classCode = 4; classCode < nClasses; classCode++) {
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let entryIndex = row[classCode];
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let entry = entryTable.getItem(entryIndex);
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// Try all glyphs in the class
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for (let glyph of this.lookupTable.glyphsForValue(classCode)) {
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if (opts.enter) {
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opts.enter(glyph, entry);
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}
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if (entry.newState !== 0) {
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this.traverse(opts, entry.newState, visited);
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}
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if (opts.exit) {
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opts.exit(glyph, entry);
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}
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}
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}
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}
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}
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