lib/core/function.js

/**
 * @licstart The following is the entire license notice for the
 * Javascript code in this page
 *
 * Copyright 2020 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.PostScriptCompiler = exports.PostScriptEvaluator = 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;
    this._localFunctionCache = null;
  }

  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) {
      if (!this._localFunctionCache) {
        this._localFunctionCache = new _image_utils.LocalFunctionCache();
      }

      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) {
      if (!this._localFunctionCache) {
        this._localFunctionCache = new _image_utils.LocalFunctionCache();
      }

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

}

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;
}

var PDFFunction = function PDFFunctionClosure() {
  const CONSTRUCT_SAMPLED = 0;
  const CONSTRUCT_INTERPOLATED = 2;
  const CONSTRUCT_STICHED = 3;
  const CONSTRUCT_POSTSCRIPT = 4;
  return {
    getSampleArray(size, outputSize, bps, stream) {
      var i, ii;
      var length = 1;

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

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

    getIR({
      xref,
      isEvalSupported,
      fn
    }) {
      var dict = fn.dict;

      if (!dict) {
        dict = fn;
      }

      var types = [this.constructSampled, null, this.constructInterpolated, this.constructStiched, this.constructPostScript];
      var typeNum = dict.get("FunctionType");
      var typeFn = types[typeNum];

      if (!typeFn) {
        throw new _util.FormatError("Unknown type of function");
      }

      return typeFn.call(this, {
        xref,
        isEvalSupported,
        fn,
        dict
      });
    },

    fromIR({
      xref,
      isEvalSupported,
      IR
    }) {
      var type = IR[0];

      switch (type) {
        case CONSTRUCT_SAMPLED:
          return this.constructSampledFromIR({
            xref,
            isEvalSupported,
            IR
          });

        case CONSTRUCT_INTERPOLATED:
          return this.constructInterpolatedFromIR({
            xref,
            isEvalSupported,
            IR
          });

        case CONSTRUCT_STICHED:
          return this.constructStichedFromIR({
            xref,
            isEvalSupported,
            IR
          });

        default:
          return this.constructPostScriptFromIR({
            xref,
            isEvalSupported,
            IR
          });
      }
    },

    parse({
      xref,
      isEvalSupported,
      fn
    }) {
      const IR = this.getIR({
        xref,
        isEvalSupported,
        fn
      });
      return this.fromIR({
        xref,
        isEvalSupported,
        IR
      });
    },

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

      var fnArray = [];

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

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

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

        return out;
      }

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

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

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

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

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

      if (!encode) {
        encode = [];

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

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

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

      var samples = this.getSampleArray(size, outputSize, bps, fn);
      return [CONSTRUCT_SAMPLED, inputSize, domain, encode, decode, samples, size, outputSize, 2 ** bps - 1, range];
    },

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

      return function constructSampledFromIRResult(src, srcOffset, dest, destOffset) {
        var m = IR[1];
        var domain = IR[2];
        var encode = IR[3];
        var decode = IR[4];
        var samples = IR[5];
        var size = IR[6];
        var n = IR[7];
        var range = IR[9];
        var cubeVertices = 1 << m;
        var cubeN = new Float64Array(cubeVertices);
        var cubeVertex = new Uint32Array(cubeVertices);
        var i, j;

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

        var k = n,
            pos = 1;

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

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

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

      return [CONSTRUCT_INTERPOLATED, c0, diff, n];
    },

    constructInterpolatedFromIR({
      xref,
      isEvalSupported,
      IR
    }) {
      var c0 = IR[1];
      var diff = IR[2];
      var n = IR[3];
      var length = diff.length;
      return function constructInterpolatedFromIRResult(src, srcOffset, dest, destOffset) {
        var x = n === 1 ? src[srcOffset] : src[srcOffset] ** n;

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

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

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

      var inputSize = domain.length / 2;

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

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

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

      var bounds = toNumberArray(dict.getArray("Bounds"));
      var encode = toNumberArray(dict.getArray("Encode"));
      return [CONSTRUCT_STICHED, domain, bounds, encode, fns];
    },

    constructStichedFromIR({
      xref,
      isEvalSupported,
      IR
    }) {
      var domain = IR[1];
      var bounds = IR[2];
      var encode = IR[3];
      var fns = IR[4];
      var tmpBuf = new Float32Array(1);
      return function constructStichedFromIRResult(src, srcOffset, dest, destOffset) {
        var clip = function constructStichedFromIRClip(v, min, max) {
          if (v > max) {
            v = max;
          } else if (v < min) {
            v = min;
          }

          return v;
        };

        var v = clip(src[srcOffset], domain[0], domain[1]);

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

        var dmin = domain[0];

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

        var dmax = domain[1];

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

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

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

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

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

      var lexer = new _ps_parser.PostScriptLexer(fn);
      var parser = new _ps_parser.PostScriptParser(lexer);
      var code = parser.parse();
      return [CONSTRUCT_POSTSCRIPT, domain, range, code];
    },

    constructPostScriptFromIR({
      xref,
      isEvalSupported,
      IR
    }) {
      var domain = IR[1];
      var range = IR[2];
      var code = IR[3];

      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");
      var numOutputs = range.length >> 1;
      var numInputs = domain.length >> 1;
      var evaluator = new PostScriptEvaluator(code);
      var cache = Object.create(null);
      var MAX_CACHE_SIZE = 2048 * 4;
      var cache_available = MAX_CACHE_SIZE;
      var tmpBuf = new Float32Array(numInputs);
      return function constructPostScriptFromIRResult(src, srcOffset, dest, destOffset) {
        var i, value;
        var key = "";
        var input = tmpBuf;

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

        var cachedValue = cache[key];

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

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

        for (i = 0; i < numOutputs; i++) {
          value = stack[stackIndex + i];
          var 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) {
  var 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");
}

var PostScriptStack = function PostScriptStackClosure() {
  var MAX_STACK_SIZE = 100;

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

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

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

      return this.stack.pop();
    },
    copy: function PostScriptStack_copy(n) {
      if (this.stack.length + n >= MAX_STACK_SIZE) {
        throw new Error("PostScript function stack overflow.");
      }

      var stack = this.stack;

      for (var i = stack.length - n, j = n - 1; j >= 0; j--, i++) {
        stack.push(stack[i]);
      }
    },
    index: function PostScriptStack_index(n) {
      this.push(this.stack[this.stack.length - n - 1]);
    },
    roll: function PostScriptStack_roll(n, p) {
      var stack = this.stack;
      var l = stack.length - n;
      var r = stack.length - 1,
          c = l + (p - Math.floor(p / n) * n),
          i,
          j,
          t;

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

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

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

var PostScriptEvaluator = function PostScriptEvaluatorClosure() {
  function PostScriptEvaluator(operators) {
    this.operators = operators;
  }

  PostScriptEvaluator.prototype = {
    execute: function PostScriptEvaluator_execute(initialStack) {
      var stack = new PostScriptStack(initialStack);
      var counter = 0;
      var operators = this.operators;
      var length = operators.length;
      var 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;
    }
  };
  return PostScriptEvaluator;
}();

exports.PostScriptEvaluator = PostScriptEvaluator;

var PostScriptCompiler = function PostScriptCompilerClosure() {
  function AstNode(type) {
    this.type = type;
  }

  AstNode.prototype.visit = function (visitor) {
    (0, _util.unreachable)("abstract method");
  };

  function AstArgument(index, min, max) {
    AstNode.call(this, "args");
    this.index = index;
    this.min = min;
    this.max = max;
  }

  AstArgument.prototype = Object.create(AstNode.prototype);

  AstArgument.prototype.visit = function (visitor) {
    visitor.visitArgument(this);
  };

  function AstLiteral(number) {
    AstNode.call(this, "literal");
    this.number = number;
    this.min = number;
    this.max = number;
  }

  AstLiteral.prototype = Object.create(AstNode.prototype);

  AstLiteral.prototype.visit = function (visitor) {
    visitor.visitLiteral(this);
  };

  function AstBinaryOperation(op, arg1, arg2, min, max) {
    AstNode.call(this, "binary");
    this.op = op;
    this.arg1 = arg1;
    this.arg2 = arg2;
    this.min = min;
    this.max = max;
  }

  AstBinaryOperation.prototype = Object.create(AstNode.prototype);

  AstBinaryOperation.prototype.visit = function (visitor) {
    visitor.visitBinaryOperation(this);
  };

  function AstMin(arg, max) {
    AstNode.call(this, "max");
    this.arg = arg;
    this.min = arg.min;
    this.max = max;
  }

  AstMin.prototype = Object.create(AstNode.prototype);

  AstMin.prototype.visit = function (visitor) {
    visitor.visitMin(this);
  };

  function AstVariable(index, min, max) {
    AstNode.call(this, "var");
    this.index = index;
    this.min = min;
    this.max = max;
  }

  AstVariable.prototype = Object.create(AstNode.prototype);

  AstVariable.prototype.visit = function (visitor) {
    visitor.visitVariable(this);
  };

  function AstVariableDefinition(variable, arg) {
    AstNode.call(this, "definition");
    this.variable = variable;
    this.arg = arg;
  }

  AstVariableDefinition.prototype = Object.create(AstNode.prototype);

  AstVariableDefinition.prototype.visit = function (visitor) {
    visitor.visitVariableDefinition(this);
  };

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

  ExpressionBuilderVisitor.prototype = {
    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;
      }
    }

    var min = Math.min(num1.min * num2.min, num1.min * num2.max, num1.max * num2.min, num1.max * num2.max);
    var 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);
  }

  function PostScriptCompiler() {}

  PostScriptCompiler.prototype = {
    compile: function PostScriptCompiler_compile(code, domain, range) {
      var stack = [];
      var instructions = [];
      var inputSize = domain.length >> 1,
          outputSize = range.length >> 1;
      var lastRegister = 0;
      var n, j;
      var 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;
      }

      var result = [];
      instructions.forEach(function (instruction) {
        var statementBuilder = new ExpressionBuilderVisitor();
        instruction.visit(statementBuilder);
        result.push(statementBuilder.toString());
      });
      stack.forEach(function (expr, i) {
        var statementBuilder = new ExpressionBuilderVisitor();
        expr.visit(statementBuilder);
        var min = range[i * 2],
            max = range[i * 2 + 1];
        var 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;