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Initial check-in of sharps-full.js.
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Jason Orendorff committed Aug 15, 2011
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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

// sharps-full.js - Parser for sharp object literals where values may be JS functions.
//
// To use this file, concatenate it with lib/jsdefs.js, lib/jslex.js,
// lib/jsparse.js, and lib/decomp.js, then run it through your favorite JS code
// compressor. This file provides a single function:
//
// Sharps.parse(str) - Parse the string as a JS expression with
// sharp object syntax. Return its value.

var Sharps = (function () {
var TOK = Narcissus.definitions.tokenIds;

// The basic algorithm:
//
// Sharp defs, #nnn=[...] or #mmm={...}, are translated directly into
// assignment expressions $S[nnn]=[...] or $S[mmm]={...}.
//
// Each object literal or array literal that directly contains a sharp ref:
// { ..., a: #nnn#, ...}
// [ ..., #mmm#, ...]
// is assigned a number if it doesn't already have a number by virtue of a
// sharpdef. Thus these may be translated to
// ($S[j] = { ... a: 0, ...})
// ($S[k] = [ ... 0, ...])
// where j and k are chosen arbitrarily. The 0 is just a placeholder.
//
// The entire AST is translated this way; and then each object that had a
// sharp ref is fixed up by assigning, for example:
// $S[j].a = $S[nnn]
// $S[k][5] = $S[mmm]
//
// The AST and the fixup assignments are bundled together in a function that
// evaluates them and returns the appropriate object. The final result is a
// call-expression that calls this function.
//
// Example:
// #1=[#1#]
// This is translated by replacing the sharpref #1# with 0 and replacing the
// sharpdef #1=[...] with $S[1]=[...]. So the translation is $S[1]=[0].
// The fixup assignment for the #1# is $S[1][0] = $S[1].
// The final result of combining the translation with the fixup is:
// (function ($S) { return [$S[1]=[0]][$S[1][0] = $S[1], 0]; })([])
function parse(s) {
var ast = Narcissus.parser.parse("(" + s + ");");
if (ast.type !== TOK.SCRIPT)
throw SyntaxError("parser internal error");
if (ast.children.length !== 1)
throw SyntaxError("expected a single expression");
ast = ast.children[0];
if (ast.type !== TOK.SEMICOLON)
throw SyntaxError("expected a single expression, not a statement");
ast = ast.expression;

// Node constructors.
var tokenizer = ast.tokenizer;
function assign(l, r) {
var x = new Narcissus.parser.Node(tokenizer, {type: TOK.ASSIGN});
x.push(l);
x.push(r);
return x;
}
function index(a, b) {
var x = new Narcissus.parser.Node(tokenizer, {type: TOK.INDEX});
x.push(a);
x.push(b);
return x;
}
function dot(a, b) {
var x = new Narcissus.parser.Node(tokenizer, {type: TOK.DOT});
x.push(a);
x.push(b);
return x;
}
function identifier(id) {
return new Narcissus.parser.Node(tokenizer, {type: TOK.IDENTIFIER, value: id});
}
function number(v) {
return new Narcissus.parser.Node(tokenizer, {type: TOK.NUMBER, value: v});
}
function string(v) {
return new Narcissus.parser.Node(tokenizer, {type: TOK.STRING, value: v});
}
function seq(arr) {
var x = new Narcissus.parser.Node(tokenizer, {type: TOK.COMMA});
for (var i = 0; i < arr.length; i++)
x.push(arr[i]);
return x;
}
function arrayInit(arr) {
var x = new Narcissus.parser.Node(tokenizer, {type: TOK.ARRAY_INIT});
for (var i = 0; i < arr.length; i++)
x.push(arr[i]);
return x;
}
function prog0(arr) {
// prog0([n, n1...]) ==> `[n][(n1..., 0)]`
var first = arr[0];
if (arr.length === 1)
return first;
var rest = arr.slice(1);
rest.push(number(0));
return index(arrayInit([first]), seq(rest));
}

var sharpVars = [];
var nextSyntheticId = 0;
var syntheticIndexNodes = [];
var fixups = [];

function translateNode(n, objid) {
var objidIsSharpIndex = objid !== undefined;
switch (n.type) {
case TOK.OBJECT_INIT:
var arr = n.children;
for (var j = 0; j < arr.length; j++) {
var pi = arr[j];
assertEq(pi.type, TOK.PROPERTY_INIT);
var pair = pi.children;
assertEq(pair.length, 2);
var id = pair[0], expr = pair[1];
assertEq(id.type, TOK.IDENTIFIER);
if (expr.type === TOK.SHARPREF) {
if (sharpVars[expr.value] === undefined)
throw new SyntaxError("Sharp variable used before definition");
if (objid === undefined)
objid = nextSyntheticId++;
fixups.push([objid, objidIsSharpIndex, id.value, expr.value]);
pair[1] = number(0);
} else {
pair[1] = translateNode(expr);
}
}
break;

case TOK.ARRAY_INIT:
var arr = n.children;
for (var j = 0; j < arr.length; j++) {
var expr = arr[j];
if (expr === null)
continue;

if (expr.type === TOK.SHARPREF) {
if (sharpVars[expr.value] === undefined)
throw new SyntaxError("Sharp variable used before definition");
if (objid === undefined)
objid = nextSyntheticId++;
fixups.push([objid, objidIsSharpIndex, j, expr.value]);
arr[j] = number(0);
} else {
arr[j] = translateNode(expr);
}
}
break;

case TOK.SHARPDEF:
if (n.value in sharpVars)
throw new SyntaxError("Sharp variable multiply defined");
sharpVars[n.value] = true;
var payload = translateNode(n.children[0], n.value);
return assign(index(identifier("$S"), number(n.value)), payload);

case TOK.SHARPREF:
throw new SyntaxError("Sharp variable reference in unsupported position");

default:
return n;
}

if (objidIsSharpIndex || objid === undefined)
return n;

var idx = number(objid);
syntheticIndexNodes.push(idx);
return assign(index(identifier("$S"), idx), n);
}


var arr = [translateNode(ast)];
var result;
if (sharpVars.length === 0) {
result = s;
} else {
// All the synthetic index numbers we came up with must be incremented
// so as not to conflict with any sharp variable number.
for (var i = 0; i < syntheticIndexNodes.length; i++)
syntheticIndexNodes[i].value += sharpVars.length;

for (var i = 0; i < fixups.length; i++) {
var f = fixups[i];
var objid = f[0], objidIsSharpIndex = f[1], propid = f[2], sharpid = f[3];
if (!objidIsSharpIndex)
objid += sharpVars.length;
var objexpr = index(identifier("$S"), objid);
var propexpr;
if (typeof propid === 'number')
propexpr = index(objexpr, number(propid));
else if (/^[A-Za-z_$][0-9A-Za-z_$]*$/.exec(propid) === null)
propexpr = index(objexpr, string(propid));
else
propexpr = dot(objexpr, identifier(propid));
var sharpobjexpr = index(identifier("$S"), number(sharpid));
arr.push(assign(propexpr, sharpobjexpr));
}

var expr = Narcissus.decompiler.pp(prog0(arr));
result = "(function($S){return " + expr + ";}([]))";
}

var indirectEval = eval;
return indirectEval(result);
}

return {parse: parse};
})();

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