jsxmin_reduction.cpp
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	/**
	* Copyright (c) 2008-2009 Facebook
	*
	* 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.
	*
	* See accompanying file LICENSE.txt.
	*
	* @author Marcel Laverdet
	*/

	#include "libfbjs/node.hpp"

	#include "jsxmin_reduction.h"
	#include "reduce.hpp"

	#include <iostream>
	#include <string.h>

	using namespace fbjs;
	using namespace std;

	void CodeReduction::process(NodeProgram* root) {
	// If there is no well-formed replacement pattern in command line option,
	// skip the process. A well-formed pattern string has the format of
	// "pattern1:replacement1,pattern2:replacement2".
	// For example, --replace "__DEV__:0,Util.isDevelopmentEnvironment():false"
	// specifies that replaces __DEV__ by 0
	// and replaces Util.isDevelopmentEnvironment() by false.
	if (parse_patterns(replacements)) {
	for (replacement_t::iterator it = _replacement.begin();
	it != _replacement.end();
	++it) {
	NodeProgram left(it->first.c_str());
	NodeProgram right(it->second.c_str());
	replace(root, find_expression(&left), find_expression(&right));
	}
	}

	ReductionWalker walker;
	walker.walk(root);
	}

	// Format: orig1 : new1, orig2: new2, parsed as
	// orig1 => new1
	// orig2 => new2
	bool CodeReduction::parse_patterns(const string& input) {
	if (input.size() == 0) {
	return false;
	}

	size_t cur_pos = 0;
	while (true) {
	size_t pos = input.find(',', cur_pos);
	size_t end_pos = (pos == string::npos) ? input.size() : pos;
	string pattern = input.substr(cur_pos, end_pos-cur_pos);

	size_t p = pattern.find(':');
	if (p != string::npos) {
	string needle = pattern.substr(0, p);
	string rep = pattern.substr(p+1);
	_replacement[needle] = rep;
	}

	if (pos == string::npos) {
	break;
	}
	cur_pos = end_pos + 1;
	}

	return _replacement.size() != 0;
	}

	// Replaces instances of `needle` in `haystack` with `rep`.
	Node* CodeReduction::replace(Node* haystack, const Node* needle,
	const Node* rep) {
	if (haystack == NULL) {
	return NULL;
	} else if (haystack == needle) {
	delete haystack;
	return rep->clone();
	}

	Node* tmp;
	node_list_t::iterator ii = haystack->childNodes().begin();
	while (ii != haystack->childNodes().end()) {
	tmp = replace(*ii, needle, rep);
	if (tmp != (*ii)) {
	haystack->replaceChild(tmp, ii++);
	} else {
	++ii;
	}
	}
	return haystack;
	}

	// Finds the first NodeExpression in a Node tree
	const NodeExpression* CodeReduction::find_expression(const Node* node) {
	if (dynamic_cast<const NodeExpression*>(node) != NULL) {
	return static_cast<const NodeExpression*>(node);
	}
	const NodeExpression* tmp;
	for (node_list_t::iterator ii = node->childNodes().begin(); ii != node->childNodes().end(); ++ii) {
	tmp = find_expression(*ii);
	if (tmp != NULL) {
	return tmp;
	}
	}
	return NULL;
	}

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