pdfjs-dist/lib/core/function.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2021 Mozilla Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * @licend The above is the entire license notice for the
 * Javascript code in this page
 */
"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.isPDFFunction = isPDFFunction;
exports.PostScriptEvaluator = exports.PostScriptCompiler = exports.PDFFunctionFactory = void 0;

var _primitives = require("./primitives.js");

var _util = require("../shared/util.js");

var _ps_parser = require("./ps_parser.js");

var _image_utils = require("./image_utils.js");

class PDFFunctionFactory {
  constructor({
    xref,
    isEvalSupported = true
  }) {
    this.xref = xref;
    this.isEvalSupported = isEvalSupported !== false;
  }

  create(fn) {
    const cachedFunction = this.getCached(fn);

    if (cachedFunction) {
      return cachedFunction;
    }

    const parsedFunction = PDFFunction.parse({
      xref: this.xref,
      isEvalSupported: this.isEvalSupported,
      fn: fn instanceof _primitives.Ref ? this.xref.fetch(fn) : fn
    });

    this._cache(fn, parsedFunction);

    return parsedFunction;
  }

  createFromArray(fnObj) {
    const cachedFunction = this.getCached(fnObj);

    if (cachedFunction) {
      return cachedFunction;
    }

    const parsedFunction = PDFFunction.parseArray({
      xref: this.xref,
      isEvalSupported: this.isEvalSupported,
      fnObj: fnObj instanceof _primitives.Ref ? this.xref.fetch(fnObj) : fnObj
    });

    this._cache(fnObj, parsedFunction);

    return parsedFunction;
  }

  getCached(cacheKey) {
    let fnRef;

    if (cacheKey instanceof _primitives.Ref) {
      fnRef = cacheKey;
    } else if (cacheKey instanceof _primitives.Dict) {
      fnRef = cacheKey.objId;
    } else if ((0, _primitives.isStream)(cacheKey)) {
      fnRef = cacheKey.dict && cacheKey.dict.objId;
    }

    if (fnRef) {
      const localFunction = this._localFunctionCache.getByRef(fnRef);

      if (localFunction) {
        return localFunction;
      }
    }

    return null;
  }

  _cache(cacheKey, parsedFunction) {
    if (!parsedFunction) {
      throw new Error('PDFFunctionFactory._cache - expected "parsedFunction" argument.');
    }

    let fnRef;

    if (cacheKey instanceof _primitives.Ref) {
      fnRef = cacheKey;
    } else if (cacheKey instanceof _primitives.Dict) {
      fnRef = cacheKey.objId;
    } else if ((0, _primitives.isStream)(cacheKey)) {
      fnRef = cacheKey.dict && cacheKey.dict.objId;
    }

    if (fnRef) {
      this._localFunctionCache.set(null, fnRef, parsedFunction);
    }
  }

  get _localFunctionCache() {
    return (0, _util.shadow)(this, "_localFunctionCache", new _image_utils.LocalFunctionCache());
  }

}

exports.PDFFunctionFactory = PDFFunctionFactory;

function toNumberArray(arr) {
  if (!Array.isArray(arr)) {
    return null;
  }

  const length = arr.length;

  for (let i = 0; i < length; i++) {
    if (typeof arr[i] !== "number") {
      const result = new Array(length);

      for (let j = 0; j < length; j++) {
        result[j] = +arr[j];
      }

      return result;
    }
  }

  return arr;
}

class PDFFunction {
  static getSampleArray(size, outputSize, bps, stream) {
    let i, ii;
    let length = 1;

    for (i = 0, ii = size.length; i < ii; i++) {
      length *= size[i];
    }

    length *= outputSize;
    const array = new Array(length);
    let codeSize = 0;
    let codeBuf = 0;
    const sampleMul = 1.0 / (2.0 ** bps - 1);
    const strBytes = stream.getBytes((length * bps + 7) / 8);
    let strIdx = 0;

    for (i = 0; i < length; i++) {
      while (codeSize < bps) {
        codeBuf <<= 8;
        codeBuf |= strBytes[strIdx++];
        codeSize += 8;
      }

      codeSize -= bps;
      array[i] = (codeBuf >> codeSize) * sampleMul;
      codeBuf &= (1 << codeSize) - 1;
    }

    return array;
  }

  static parse({
    xref,
    isEvalSupported,
    fn
  }) {
    const dict = fn.dict || fn;
    const typeNum = dict.get("FunctionType");

    switch (typeNum) {
      case 0:
        return this.constructSampled({
          xref,
          isEvalSupported,
          fn,
          dict
        });

      case 1:
        break;

      case 2:
        return this.constructInterpolated({
          xref,
          isEvalSupported,
          dict
        });

      case 3:
        return this.constructStiched({
          xref,
          isEvalSupported,
          dict
        });

      case 4:
        return this.constructPostScript({
          xref,
          isEvalSupported,
          fn,
          dict
        });
    }

    throw new _util.FormatError("Unknown type of function");
  }

  static parseArray({
    xref,
    isEvalSupported,
    fnObj
  }) {
    if (!Array.isArray(fnObj)) {
      return this.parse({
        xref,
        isEvalSupported,
        fn: fnObj
      });
    }

    const fnArray = [];

    for (let j = 0, jj = fnObj.length; j < jj; j++) {
      fnArray.push(this.parse({
        xref,
        isEvalSupported,
        fn: xref.fetchIfRef(fnObj[j])
      }));
    }

    return function (src, srcOffset, dest, destOffset) {
      for (let i = 0, ii = fnArray.length; i < ii; i++) {
        fnArray[i](src, srcOffset, dest, destOffset + i);
      }
    };
  }

  static constructSampled({
    xref,
    isEvalSupported,
    fn,
    dict
  }) {
    function toMultiArray(arr) {
      const inputLength = arr.length;
      const out = [];
      let index = 0;

      for (let i = 0; i < inputLength; i += 2) {
        out[index++] = [arr[i], arr[i + 1]];
      }

      return out;
    }

    function interpolate(x, xmin, xmax, ymin, ymax) {
      return ymin + (x - xmin) * ((ymax - ymin) / (xmax - xmin));
    }

    let domain = toNumberArray(dict.getArray("Domain"));
    let range = toNumberArray(dict.getArray("Range"));

    if (!domain || !range) {
      throw new _util.FormatError("No domain or range");
    }

    const inputSize = domain.length / 2;
    const outputSize = range.length / 2;
    domain = toMultiArray(domain);
    range = toMultiArray(range);
    const size = toNumberArray(dict.getArray("Size"));
    const bps = dict.get("BitsPerSample");
    const order = dict.get("Order") || 1;

    if (order !== 1) {
      (0, _util.info)("No support for cubic spline interpolation: " + order);
    }

    let encode = toNumberArray(dict.getArray("Encode"));

    if (!encode) {
      encode = [];

      for (let i = 0; i < inputSize; ++i) {
        encode.push([0, size[i] - 1]);
      }
    } else {
      encode = toMultiArray(encode);
    }

    let decode = toNumberArray(dict.getArray("Decode"));

    if (!decode) {
      decode = range;
    } else {
      decode = toMultiArray(decode);
    }

    const samples = this.getSampleArray(size, outputSize, bps, fn);
    return function constructSampledFn(src, srcOffset, dest, destOffset) {
      const cubeVertices = 1 << inputSize;
      const cubeN = new Float64Array(cubeVertices);
      const cubeVertex = new Uint32Array(cubeVertices);
      let i, j;

      for (j = 0; j < cubeVertices; j++) {
        cubeN[j] = 1;
      }

      let k = outputSize,
          pos = 1;

      for (i = 0; i < inputSize; ++i) {
        const domain_2i = domain[i][0];
        const domain_2i_1 = domain[i][1];
        const xi = Math.min(Math.max(src[srcOffset + i], domain_2i), domain_2i_1);
        let e = interpolate(xi, domain_2i, domain_2i_1, encode[i][0], encode[i][1]);
        const size_i = size[i];
        e = Math.min(Math.max(e, 0), size_i - 1);
        const e0 = e < size_i - 1 ? Math.floor(e) : e - 1;
        const n0 = e0 + 1 - e;
        const n1 = e - e0;
        const offset0 = e0 * k;
        const offset1 = offset0 + k;

        for (j = 0; j < cubeVertices; j++) {
          if (j & pos) {
            cubeN[j] *= n1;
            cubeVertex[j] += offset1;
          } else {
            cubeN[j] *= n0;
            cubeVertex[j] += offset0;
          }
        }

        k *= size_i;
        pos <<= 1;
      }

      for (j = 0; j < outputSize; ++j) {
        let rj = 0;

        for (i = 0; i < cubeVertices; i++) {
          rj += samples[cubeVertex[i] + j] * cubeN[i];
        }

        rj = interpolate(rj, 0, 1, decode[j][0], decode[j][1]);
        dest[destOffset + j] = Math.min(Math.max(rj, range[j][0]), range[j][1]);
      }
    };
  }

  static constructInterpolated({
    xref,
    isEvalSupported,
    dict
  }) {
    const c0 = toNumberArray(dict.getArray("C0")) || [0];
    const c1 = toNumberArray(dict.getArray("C1")) || [1];
    const n = dict.get("N");
    const diff = [];

    for (let i = 0, ii = c0.length; i < ii; ++i) {
      diff.push(c1[i] - c0[i]);
    }

    const length = diff.length;
    return function constructInterpolatedFn(src, srcOffset, dest, destOffset) {
      const x = n === 1 ? src[srcOffset] : src[srcOffset] ** n;

      for (let j = 0; j < length; ++j) {
        dest[destOffset + j] = c0[j] + x * diff[j];
      }
    };
  }

  static constructStiched({
    xref,
    isEvalSupported,
    dict
  }) {
    const domain = toNumberArray(dict.getArray("Domain"));

    if (!domain) {
      throw new _util.FormatError("No domain");
    }

    const inputSize = domain.length / 2;

    if (inputSize !== 1) {
      throw new _util.FormatError("Bad domain for stiched function");
    }

    const fnRefs = dict.get("Functions");
    const fns = [];

    for (let i = 0, ii = fnRefs.length; i < ii; ++i) {
      fns.push(this.parse({
        xref,
        isEvalSupported,
        fn: xref.fetchIfRef(fnRefs[i])
      }));
    }

    const bounds = toNumberArray(dict.getArray("Bounds"));
    const encode = toNumberArray(dict.getArray("Encode"));
    const tmpBuf = new Float32Array(1);
    return function constructStichedFn(src, srcOffset, dest, destOffset) {
      const clip = function constructStichedFromIRClip(v, min, max) {
        if (v > max) {
          v = max;
        } else if (v < min) {
          v = min;
        }

        return v;
      };

      const v = clip(src[srcOffset], domain[0], domain[1]);
      const length = bounds.length;
      let i;

      for (i = 0; i < length; ++i) {
        if (v < bounds[i]) {
          break;
        }
      }

      let dmin = domain[0];

      if (i > 0) {
        dmin = bounds[i - 1];
      }

      let dmax = domain[1];

      if (i < bounds.length) {
        dmax = bounds[i];
      }

      const rmin = encode[2 * i];
      const rmax = encode[2 * i + 1];
      tmpBuf[0] = dmin === dmax ? rmin : rmin + (v - dmin) * (rmax - rmin) / (dmax - dmin);
      fns[i](tmpBuf, 0, dest, destOffset);
    };
  }

  static constructPostScript({
    xref,
    isEvalSupported,
    fn,
    dict
  }) {
    const domain = toNumberArray(dict.getArray("Domain"));
    const range = toNumberArray(dict.getArray("Range"));

    if (!domain) {
      throw new _util.FormatError("No domain.");
    }

    if (!range) {
      throw new _util.FormatError("No range.");
    }

    const lexer = new _ps_parser.PostScriptLexer(fn);
    const parser = new _ps_parser.PostScriptParser(lexer);
    const code = parser.parse();

    if (isEvalSupported && _util.IsEvalSupportedCached.value) {
      const compiled = new PostScriptCompiler().compile(code, domain, range);

      if (compiled) {
        return new Function("src", "srcOffset", "dest", "destOffset", compiled);
      }
    }

    (0, _util.info)("Unable to compile PS function");
    const numOutputs = range.length >> 1;
    const numInputs = domain.length >> 1;
    const evaluator = new PostScriptEvaluator(code);
    const cache = Object.create(null);
    const MAX_CACHE_SIZE = 2048 * 4;
    let cache_available = MAX_CACHE_SIZE;
    const tmpBuf = new Float32Array(numInputs);
    return function constructPostScriptFn(src, srcOffset, dest, destOffset) {
      let i, value;
      let key = "";
      const input = tmpBuf;

      for (i = 0; i < numInputs; i++) {
        value = src[srcOffset + i];
        input[i] = value;
        key += value + "_";
      }

      const cachedValue = cache[key];

      if (cachedValue !== undefined) {
        dest.set(cachedValue, destOffset);
        return;
      }

      const output = new Float32Array(numOutputs);
      const stack = evaluator.execute(input);
      const stackIndex = stack.length - numOutputs;

      for (i = 0; i < numOutputs; i++) {
        value = stack[stackIndex + i];
        let bound = range[i * 2];

        if (value < bound) {
          value = bound;
        } else {
          bound = range[i * 2 + 1];

          if (value > bound) {
            value = bound;
          }
        }

        output[i] = value;
      }

      if (cache_available > 0) {
        cache_available--;
        cache[key] = output;
      }

      dest.set(output, destOffset);
    };
  }

}

function isPDFFunction(v) {
  let fnDict;

  if (typeof v !== "object") {
    return false;
  } else if ((0, _primitives.isDict)(v)) {
    fnDict = v;
  } else if ((0, _primitives.isStream)(v)) {
    fnDict = v.dict;
  } else {
    return false;
  }

  return fnDict.has("FunctionType");
}

class PostScriptStack {
  static get MAX_STACK_SIZE() {
    return (0, _util.shadow)(this, "MAX_STACK_SIZE", 100);
  }

  constructor(initialStack) {
    this.stack = !initialStack ? [] : Array.prototype.slice.call(initialStack, 0);
  }

  push(value) {
    if (this.stack.length >= PostScriptStack.MAX_STACK_SIZE) {
      throw new Error("PostScript function stack overflow.");
    }

    this.stack.push(value);
  }

  pop() {
    if (this.stack.length <= 0) {
      throw new Error("PostScript function stack underflow.");
    }

    return this.stack.pop();
  }

  copy(n) {
    if (this.stack.length + n >= PostScriptStack.MAX_STACK_SIZE) {
      throw new Error("PostScript function stack overflow.");
    }

    const stack = this.stack;

    for (let i = stack.length - n, j = n - 1; j >= 0; j--, i++) {
      stack.push(stack[i]);
    }
  }

  index(n) {
    this.push(this.stack[this.stack.length - n - 1]);
  }

  roll(n, p) {
    const stack = this.stack;
    const l = stack.length - n;
    const r = stack.length - 1;
    const c = l + (p - Math.floor(p / n) * n);

    for (let i = l, j = r; i < j; i++, j--) {
      const t = stack[i];
      stack[i] = stack[j];
      stack[j] = t;
    }

    for (let i = l, j = c - 1; i < j; i++, j--) {
      const t = stack[i];
      stack[i] = stack[j];
      stack[j] = t;
    }

    for (let i = c, j = r; i < j; i++, j--) {
      const t = stack[i];
      stack[i] = stack[j];
      stack[j] = t;
    }
  }

}

class PostScriptEvaluator {
  constructor(operators) {
    this.operators = operators;
  }

  execute(initialStack) {
    const stack = new PostScriptStack(initialStack);
    let counter = 0;
    const operators = this.operators;
    const length = operators.length;
    let operator, a, b;

    while (counter < length) {
      operator = operators[counter++];

      if (typeof operator === "number") {
        stack.push(operator);
        continue;
      }

      switch (operator) {
        case "jz":
          b = stack.pop();
          a = stack.pop();

          if (!a) {
            counter = b;
          }

          break;

        case "j":
          a = stack.pop();
          counter = a;
          break;

        case "abs":
          a = stack.pop();
          stack.push(Math.abs(a));
          break;

        case "add":
          b = stack.pop();
          a = stack.pop();
          stack.push(a + b);
          break;

        case "and":
          b = stack.pop();
          a = stack.pop();

          if ((0, _util.isBool)(a) && (0, _util.isBool)(b)) {
            stack.push(a && b);
          } else {
            stack.push(a & b);
          }

          break;

        case "atan":
          a = stack.pop();
          stack.push(Math.atan(a));
          break;

        case "bitshift":
          b = stack.pop();
          a = stack.pop();

          if (a > 0) {
            stack.push(a << b);
          } else {
            stack.push(a >> b);
          }

          break;

        case "ceiling":
          a = stack.pop();
          stack.push(Math.ceil(a));
          break;

        case "copy":
          a = stack.pop();
          stack.copy(a);
          break;

        case "cos":
          a = stack.pop();
          stack.push(Math.cos(a));
          break;

        case "cvi":
          a = stack.pop() | 0;
          stack.push(a);
          break;

        case "cvr":
          break;

        case "div":
          b = stack.pop();
          a = stack.pop();
          stack.push(a / b);
          break;

        case "dup":
          stack.copy(1);
          break;

        case "eq":
          b = stack.pop();
          a = stack.pop();
          stack.push(a === b);
          break;

        case "exch":
          stack.roll(2, 1);
          break;

        case "exp":
          b = stack.pop();
          a = stack.pop();
          stack.push(a ** b);
          break;

        case "false":
          stack.push(false);
          break;

        case "floor":
          a = stack.pop();
          stack.push(Math.floor(a));
          break;

        case "ge":
          b = stack.pop();
          a = stack.pop();
          stack.push(a >= b);
          break;

        case "gt":
          b = stack.pop();
          a = stack.pop();
          stack.push(a > b);
          break;

        case "idiv":
          b = stack.pop();
          a = stack.pop();
          stack.push(a / b | 0);
          break;

        case "index":
          a = stack.pop();
          stack.index(a);
          break;

        case "le":
          b = stack.pop();
          a = stack.pop();
          stack.push(a <= b);
          break;

        case "ln":
          a = stack.pop();
          stack.push(Math.log(a));
          break;

        case "log":
          a = stack.pop();
          stack.push(Math.log(a) / Math.LN10);
          break;

        case "lt":
          b = stack.pop();
          a = stack.pop();
          stack.push(a < b);
          break;

        case "mod":
          b = stack.pop();
          a = stack.pop();
          stack.push(a % b);
          break;

        case "mul":
          b = stack.pop();
          a = stack.pop();
          stack.push(a * b);
          break;

        case "ne":
          b = stack.pop();
          a = stack.pop();
          stack.push(a !== b);
          break;

        case "neg":
          a = stack.pop();
          stack.push(-a);
          break;

        case "not":
          a = stack.pop();

          if ((0, _util.isBool)(a)) {
            stack.push(!a);
          } else {
            stack.push(~a);
          }

          break;

        case "or":
          b = stack.pop();
          a = stack.pop();

          if ((0, _util.isBool)(a) && (0, _util.isBool)(b)) {
            stack.push(a || b);
          } else {
            stack.push(a | b);
          }

          break;

        case "pop":
          stack.pop();
          break;

        case "roll":
          b = stack.pop();
          a = stack.pop();
          stack.roll(a, b);
          break;

        case "round":
          a = stack.pop();
          stack.push(Math.round(a));
          break;

        case "sin":
          a = stack.pop();
          stack.push(Math.sin(a));
          break;

        case "sqrt":
          a = stack.pop();
          stack.push(Math.sqrt(a));
          break;

        case "sub":
          b = stack.pop();
          a = stack.pop();
          stack.push(a - b);
          break;

        case "true":
          stack.push(true);
          break;

        case "truncate":
          a = stack.pop();
          a = a < 0 ? Math.ceil(a) : Math.floor(a);
          stack.push(a);
          break;

        case "xor":
          b = stack.pop();
          a = stack.pop();

          if ((0, _util.isBool)(a) && (0, _util.isBool)(b)) {
            stack.push(a !== b);
          } else {
            stack.push(a ^ b);
          }

          break;

        default:
          throw new _util.FormatError(`Unknown operator ${operator}`);
      }
    }

    return stack.stack;
  }

}

exports.PostScriptEvaluator = PostScriptEvaluator;

const PostScriptCompiler = function PostScriptCompilerClosure() {
  class AstNode {
    constructor(type) {
      this.type = type;
    }

    visit(visitor) {
      (0, _util.unreachable)("abstract method");
    }

  }

  class AstArgument extends AstNode {
    constructor(index, min, max) {
      super("args");
      this.index = index;
      this.min = min;
      this.max = max;
    }

    visit(visitor) {
      visitor.visitArgument(this);
    }

  }

  class AstLiteral extends AstNode {
    constructor(number) {
      super("literal");
      this.number = number;
      this.min = number;
      this.max = number;
    }

    visit(visitor) {
      visitor.visitLiteral(this);
    }

  }

  class AstBinaryOperation extends AstNode {
    constructor(op, arg1, arg2, min, max) {
      super("binary");
      this.op = op;
      this.arg1 = arg1;
      this.arg2 = arg2;
      this.min = min;
      this.max = max;
    }

    visit(visitor) {
      visitor.visitBinaryOperation(this);
    }

  }

  class AstMin extends AstNode {
    constructor(arg, max) {
      super("max");
      this.arg = arg;
      this.min = arg.min;
      this.max = max;
    }

    visit(visitor) {
      visitor.visitMin(this);
    }

  }

  class AstVariable extends AstNode {
    constructor(index, min, max) {
      super("var");
      this.index = index;
      this.min = min;
      this.max = max;
    }

    visit(visitor) {
      visitor.visitVariable(this);
    }

  }

  class AstVariableDefinition extends AstNode {
    constructor(variable, arg) {
      super("definition");
      this.variable = variable;
      this.arg = arg;
    }

    visit(visitor) {
      visitor.visitVariableDefinition(this);
    }

  }

  class ExpressionBuilderVisitor {
    constructor() {
      this.parts = [];
    }

    visitArgument(arg) {
      this.parts.push("Math.max(", arg.min, ", Math.min(", arg.max, ", src[srcOffset + ", arg.index, "]))");
    }

    visitVariable(variable) {
      this.parts.push("v", variable.index);
    }

    visitLiteral(literal) {
      this.parts.push(literal.number);
    }

    visitBinaryOperation(operation) {
      this.parts.push("(");
      operation.arg1.visit(this);
      this.parts.push(" ", operation.op, " ");
      operation.arg2.visit(this);
      this.parts.push(")");
    }

    visitVariableDefinition(definition) {
      this.parts.push("var ");
      definition.variable.visit(this);
      this.parts.push(" = ");
      definition.arg.visit(this);
      this.parts.push(";");
    }

    visitMin(max) {
      this.parts.push("Math.min(");
      max.arg.visit(this);
      this.parts.push(", ", max.max, ")");
    }

    toString() {
      return this.parts.join("");
    }

  }

  function buildAddOperation(num1, num2) {
    if (num2.type === "literal" && num2.number === 0) {
      return num1;
    }

    if (num1.type === "literal" && num1.number === 0) {
      return num2;
    }

    if (num2.type === "literal" && num1.type === "literal") {
      return new AstLiteral(num1.number + num2.number);
    }

    return new AstBinaryOperation("+", num1, num2, num1.min + num2.min, num1.max + num2.max);
  }

  function buildMulOperation(num1, num2) {
    if (num2.type === "literal") {
      if (num2.number === 0) {
        return new AstLiteral(0);
      } else if (num2.number === 1) {
        return num1;
      } else if (num1.type === "literal") {
        return new AstLiteral(num1.number * num2.number);
      }
    }

    if (num1.type === "literal") {
      if (num1.number === 0) {
        return new AstLiteral(0);
      } else if (num1.number === 1) {
        return num2;
      }
    }

    const min = Math.min(num1.min * num2.min, num1.min * num2.max, num1.max * num2.min, num1.max * num2.max);
    const max = Math.max(num1.min * num2.min, num1.min * num2.max, num1.max * num2.min, num1.max * num2.max);
    return new AstBinaryOperation("*", num1, num2, min, max);
  }

  function buildSubOperation(num1, num2) {
    if (num2.type === "literal") {
      if (num2.number === 0) {
        return num1;
      } else if (num1.type === "literal") {
        return new AstLiteral(num1.number - num2.number);
      }
    }

    if (num2.type === "binary" && num2.op === "-" && num1.type === "literal" && num1.number === 1 && num2.arg1.type === "literal" && num2.arg1.number === 1) {
      return num2.arg2;
    }

    return new AstBinaryOperation("-", num1, num2, num1.min - num2.max, num1.max - num2.min);
  }

  function buildMinOperation(num1, max) {
    if (num1.min >= max) {
      return new AstLiteral(max);
    } else if (num1.max <= max) {
      return num1;
    }

    return new AstMin(num1, max);
  }

  class PostScriptCompiler {
    compile(code, domain, range) {
      const stack = [];
      const instructions = [];
      const inputSize = domain.length >> 1,
            outputSize = range.length >> 1;
      let lastRegister = 0;
      let n, j;
      let num1, num2, ast1, ast2, tmpVar, item;

      for (let i = 0; i < inputSize; i++) {
        stack.push(new AstArgument(i, domain[i * 2], domain[i * 2 + 1]));
      }

      for (let i = 0, ii = code.length; i < ii; i++) {
        item = code[i];

        if (typeof item === "number") {
          stack.push(new AstLiteral(item));
          continue;
        }

        switch (item) {
          case "add":
            if (stack.length < 2) {
              return null;
            }

            num2 = stack.pop();
            num1 = stack.pop();
            stack.push(buildAddOperation(num1, num2));
            break;

          case "cvr":
            if (stack.length < 1) {
              return null;
            }

            break;

          case "mul":
            if (stack.length < 2) {
              return null;
            }

            num2 = stack.pop();
            num1 = stack.pop();
            stack.push(buildMulOperation(num1, num2));
            break;

          case "sub":
            if (stack.length < 2) {
              return null;
            }

            num2 = stack.pop();
            num1 = stack.pop();
            stack.push(buildSubOperation(num1, num2));
            break;

          case "exch":
            if (stack.length < 2) {
              return null;
            }

            ast1 = stack.pop();
            ast2 = stack.pop();
            stack.push(ast1, ast2);
            break;

          case "pop":
            if (stack.length < 1) {
              return null;
            }

            stack.pop();
            break;

          case "index":
            if (stack.length < 1) {
              return null;
            }

            num1 = stack.pop();

            if (num1.type !== "literal") {
              return null;
            }

            n = num1.number;

            if (n < 0 || !Number.isInteger(n) || stack.length < n) {
              return null;
            }

            ast1 = stack[stack.length - n - 1];

            if (ast1.type === "literal" || ast1.type === "var") {
              stack.push(ast1);
              break;
            }

            tmpVar = new AstVariable(lastRegister++, ast1.min, ast1.max);
            stack[stack.length - n - 1] = tmpVar;
            stack.push(tmpVar);
            instructions.push(new AstVariableDefinition(tmpVar, ast1));
            break;

          case "dup":
            if (stack.length < 1) {
              return null;
            }

            if (typeof code[i + 1] === "number" && code[i + 2] === "gt" && code[i + 3] === i + 7 && code[i + 4] === "jz" && code[i + 5] === "pop" && code[i + 6] === code[i + 1]) {
              num1 = stack.pop();
              stack.push(buildMinOperation(num1, code[i + 1]));
              i += 6;
              break;
            }

            ast1 = stack[stack.length - 1];

            if (ast1.type === "literal" || ast1.type === "var") {
              stack.push(ast1);
              break;
            }

            tmpVar = new AstVariable(lastRegister++, ast1.min, ast1.max);
            stack[stack.length - 1] = tmpVar;
            stack.push(tmpVar);
            instructions.push(new AstVariableDefinition(tmpVar, ast1));
            break;

          case "roll":
            if (stack.length < 2) {
              return null;
            }

            num2 = stack.pop();
            num1 = stack.pop();

            if (num2.type !== "literal" || num1.type !== "literal") {
              return null;
            }

            j = num2.number;
            n = num1.number;

            if (n <= 0 || !Number.isInteger(n) || !Number.isInteger(j) || stack.length < n) {
              return null;
            }

            j = (j % n + n) % n;

            if (j === 0) {
              break;
            }

            Array.prototype.push.apply(stack, stack.splice(stack.length - n, n - j));
            break;

          default:
            return null;
        }
      }

      if (stack.length !== outputSize) {
        return null;
      }

      const result = [];

      for (const instruction of instructions) {
        const statementBuilder = new ExpressionBuilderVisitor();
        instruction.visit(statementBuilder);
        result.push(statementBuilder.toString());
      }

      for (let i = 0, ii = stack.length; i < ii; i++) {
        const expr = stack[i],
              statementBuilder = new ExpressionBuilderVisitor();
        expr.visit(statementBuilder);
        const min = range[i * 2],
              max = range[i * 2 + 1];
        const out = [statementBuilder.toString()];

        if (min > expr.min) {
          out.unshift("Math.max(", min, ", ");
          out.push(")");
        }

        if (max < expr.max) {
          out.unshift("Math.min(", max, ", ");
          out.push(")");
        }

        out.unshift("dest[destOffset + ", i, "] = ");
        out.push(";");
        result.push(out.join(""));
      }

      return result.join("\n");
    }

  }

  return PostScriptCompiler;
}();

exports.PostScriptCompiler = PostScriptCompiler;