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84 lines
2.2 KiB
84 lines
2.2 KiB
#!/usr/bin/env node
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// This script converts for and do-while loops into equivalent while loops.
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// Note that for-in statements are left unmodified, as they do not have a
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// simple analogy to while loops. Also note that labeled continue statements
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// are not correctly handled at this point, and will trigger an assertion
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// failure if encountered.
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var assert = require("assert");
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var recast = require("recast");
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var types = recast.types;
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var n = types.namedTypes;
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var b = types.builders;
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recast.run(function(ast, callback) {
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recast.visit(ast, {
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visitForStatement: function(path) {
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var fst = path.node;
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path.replace(
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fst.init,
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b.whileStatement(
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fst.test,
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insertBeforeLoopback(fst, fst.update)
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)
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);
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this.traverse(path);
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},
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visitDoWhileStatement: function(path) {
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var dwst = path.node;
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return b.whileStatement(
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b.literal(true),
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insertBeforeLoopback(
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dwst,
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b.ifStatement(
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dwst.test,
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b.breakStatement()
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)
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)
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);
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}
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});
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callback(ast);
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});
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function insertBeforeLoopback(loop, toInsert) {
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var body = loop.body;
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if (!n.Statement.check(toInsert)) {
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toInsert = b.expressionStatement(toInsert);
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}
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if (n.BlockStatement.check(body)) {
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body.body.push(toInsert);
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} else {
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body = b.blockStatement([body, toInsert]);
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loop.body = body;
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}
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recast.visit(body, {
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visitContinueStatement: function(path) {
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var cst = path.node;
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assert.equal(
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cst.label, null,
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"Labeled continue statements are not yet supported."
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);
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path.replace(toInsert, path.node);
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return false;
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},
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// Do not descend into nested loops.
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visitWhileStatement: function() {},
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visitForStatement: function() {},
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visitForInStatement: function() {},
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visitDoWhileStatement: function() {}
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});
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return body;
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}
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