sdk/lib/_internal/compiler/implementation/js_backend/minify_namer.dart - sdk.git - Git at Google

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.

 part of js_backend;

 /**
  * Assigns JavaScript identifiers to Dart variables, class-names and members.
  */
 class MinifyNamer extends Namer {
   MinifyNamer(Compiler compiler) : super(compiler) {
     reserveBackendNames();
   }

   String get isolateName => 'I';
   String get isolatePropertiesName => 'p';
   bool get shouldMinify => true;

   final String getterPrefix = 'g';
   final String setterPrefix = 's';

   const ALPHABET_CHARACTERS = 52;  // a-zA-Z.
   const ALPHANUMERIC_CHARACTERS = 62;  // a-zA-Z0-9.

   // You can pass an invalid identifier to this and unlike its non-minifying
   // counterpart it will never return the proposedName as the new fresh name.
   String getFreshName(String proposedName,
                       Set<String> usedNames,
                       Map<String, String> suggestedNames,
                       {bool ensureSafe: true}) {
     var freshName;
     var suggestion = suggestedNames[proposedName];
     if (suggestion != null && !usedNames.contains(suggestion)) {
       freshName = suggestion;
     } else {
       freshName = _getUnusedName(proposedName, usedNames);
     }
     usedNames.add(freshName);
     return freshName;
   }

   SourceString getClosureVariableName(SourceString name, int id) {
     if (id < ALPHABET_CHARACTERS) {
       return new SourceString(new String.fromCharCodes([_letterNumber(id)]));
     }
     return new SourceString("${getMappedInstanceName('closure')}_$id");
   }

   void reserveBackendNames() {
     // From issue 7554.  These should not be used on objects (as instance
     // variables) because they clash with names from the DOM.
     const reservedNativeProperties = const <String>[
         'Q', 'a', 'b', 'c', 'd', 'e', 'f', 'r', 'x', 'y', 'z',
         // 2-letter:
         'ch', 'cx', 'cy', 'db', 'dx', 'dy', 'fr', 'fx', 'fy', 'go', 'id', 'k1',
         'k2', 'k3', 'k4', 'r1', 'r2', 'rx', 'ry', 'x1', 'x2', 'y1', 'y2',
         // 3-letter:
         'add', 'all', 'alt', 'arc', 'CCW', 'cmp', 'dir', 'end', 'get', 'in1',
         'in2', 'INT', 'key', 'log', 'low', 'm11', 'm12', 'm13', 'm14', 'm21',
         'm22', 'm23', 'm24', 'm31', 'm32', 'm33', 'm34', 'm41', 'm42', 'm43',
         'm44', 'max', 'min', 'now', 'ONE', 'put', 'red', 'rel', 'rev', 'RGB',
         'sdp', 'set', 'src', 'tag', 'top', 'uid', 'uri', 'url', 'URL',
         // 4-letter:
         'abbr', 'atob', 'Attr', 'axes', 'axis', 'back', 'BACK', 'beta', 'bias',
         'Blob', 'blue', 'blur', 'BLUR', 'body', 'BOOL', 'BOTH', 'btoa', 'BYTE',
         'cite', 'clip', 'code', 'cols', 'cues', 'data', 'DECR', 'DONE', 'face',
         'file', 'File', 'fill', 'find', 'font', 'form', 'gain', 'hash', 'head',
         'high', 'hint', 'host', 'href', 'HRTF', 'IDLE', 'INCR', 'info', 'INIT',
         'isId', 'item', 'KEEP', 'kind', 'knee', 'lang', 'left', 'LESS', 'line',
         'link', 'list', 'load', 'loop', 'mode', 'name', 'Node', 'None', 'NONE',
         'only', 'open', 'OPEN', 'ping', 'play', 'port', 'rect', 'Rect', 'refX',
         'refY', 'RGBA', 'root', 'rows', 'save', 'seed', 'seek', 'self', 'send',
         'show', 'SINE', 'size', 'span', 'stat', 'step', 'stop', 'tags', 'text',
         'Text', 'time', 'type', 'view', 'warn', 'wrap', 'ZERO'];

     for (var name in reservedNativeProperties) {
       if (name.length < 2) {
         instanceNameMap[name] = name;
       }
       usedInstanceNames.add(name);
       // Getter and setter names are autogenerated by prepending 'g' and 's' to
       // field names.  Therefore there are some field names we don't want to
       // use.  It is implicit in the next line that the banned prefix is
       // only one character.
       if (_hasBannedPrefix(name)) usedInstanceNames.add(name.substring(1));
     }

     // This list of popular instance variable names generated with:
     // cat out.js |
     // perl -ne '$_=~s/(?<![^a-z0-9_\$]\$)\.([a-z0-9_\$]+)/print("$1\n")/gei' |
     // sort | uniq -c | sort -nr | head -40
     // Removed: html, call*, hasOwnProperty.
     _populateSuggestedNames(
         suggestedInstanceNames,
         usedInstanceNames,
         const <String>[
             r'$add', r'add$1', r'box_0', r'charCodeAt$1', r'constructor',
             r'current', r'$defineNativeClass', r'$eq', r'$ne',
             r'getPrototypeOf', r'hasOwnProperty', r'$index', r'$indexSet',
             r'$isJavaScriptIndexingBehavior', r'$isolateProperties',
             r'iterator', r'length', r'$lt', r'$gt', r'$le', r'$ge',
             r'moveNext$0', r'node', r'on', r'prototype', r'push', r'self',
             r'start', r'target', r'this_0', r'value', r'width', r'style']);

     _populateSuggestedNames(
         suggestedGlobalNames,
         usedGlobalNames,
         const <String>[
             r'Object', r'$throw', r'$eq', r'S', r'ioore', r'UnsupportedError$',
             r'length', r'$sub', r'getInterceptor$JSArrayJSString', r'$add',
             r'$gt', r'$ge', r'$lt', r'$le', r'add', r'getInterceptor$JSNumber',
             r'iterator', r'$index', r'iae', r'getInterceptor$JSArray',
             r'ArgumentError$', r'BoundClosure', r'StateError$',
             r'getInterceptor', r'max', r'$mul', r'List_List', r'Map_Map',
             r'getInterceptor$JSString', r'$div', r'$indexSet',
             r'List_List$from', r'Set_Set$from', r'toString', r'toInt', r'min',
             r'StringBuffer_StringBuffer', r'contains1', r'WhereIterable$',
             r'RangeError$value', r'JSString', r'JSNumber',
             r'JSArray'
             ]);
   }

   void _populateSuggestedNames(Map<String, String> suggestionMap,
                                Set<String> used,
                                List<String> suggestions) {
     int c = $a - 1;
     String letter;
     for (String name in suggestions) {
       do {
         assert(c != $Z);
         c = (c == $z) ? $A : c + 1;
         letter = new String.fromCharCodes([c]);
       } while (used.contains(letter));
       assert(suggestionMap[name] == null);
       suggestionMap[name] = letter;
     }
   }


   // This gets a minified name based on a hash of the proposed name.  This
   // is slightly less efficient than just getting the next name in a series,
   // but it means that small changes in the input program will give smallish
   // changes in the output, which can be useful for diffing etc.
   String _getUnusedName(String proposedName, Set<String> usedNames) {
     int hash = _calculateHash(proposedName);
     // Avoid very small hashes that won't try many names.
     hash = hash < 1000 ? hash * 314159 : hash;  // Yes, it's prime.

     // Try other n-character names based on the hash.  We try one to three
     // character identifiers.  For each length we try around 10 different names
     // in a predictable order determined by the proposed name.  This is in order
     // to make the renamer stable: small changes in the input should nornally
     // result in relatively small changes in the output.
     for (var n = 2; n <= 3; n++) {
       int h = hash;
       while (h > 10) {
         var codes = <int>[_letterNumber(h)];
         int h2 = h ~/ ALPHABET_CHARACTERS;
         for (var i = 1; i < n; i++) {
           codes.add(_alphaNumericNumber(h2));
           h2 ~/= ALPHANUMERIC_CHARACTERS;
         }
         final candidate = new String.fromCharCodes(codes);
         if (!usedNames.contains(candidate) &&
             !jsReserved.contains(candidate) &&
             !_hasBannedPrefix(candidate)) {
           return candidate;
         }
         // Try again with a slightly different hash.  After around 10 turns
         // around this loop h is zero and we try a longer name.
         h ~/= 7;
       }
     }

     // If we can't find a hash based name in the three-letter space, then base
     // the name on a letter and a counter.
     var startLetter = new String.fromCharCodes([_letterNumber(hash)]);
     var i = 0;
     while (usedNames.contains("$startLetter$i")) {
       i++;
     }
     // We don't need to check for banned prefix because the name is in the form
     // xnnn, where nnn is a number.  There can be no getter or setter called
     // gnnn since that would imply a numeric field name.
     return "$startLetter$i";
   }

   /// Instance members starting with g and s are reserved for getters and
   /// setters.
   bool _hasBannedPrefix(String name) {
     int code = name.codeUnitAt(0);
     return code == $g || code == $s;
   }

   int _calculateHash(String name) {
     int h = 0;
     for (int i = 0; i < name.length; i++) {
       h += name.codeUnitAt(i);
       h &= 0xffffffff;
       h += h << 10;
       h &= 0xffffffff;
       h ^= h >> 6;
       h &= 0xffffffff;
     }
     return h;
   }

   int _letterNumber(int x) {
     if (x >= ALPHABET_CHARACTERS) x %= ALPHABET_CHARACTERS;
     if (x < 26) return $a + x;
     return $A + x - 26;
   }

   int _alphaNumericNumber(int x) {
     if (x >= ALPHANUMERIC_CHARACTERS) x %= ALPHANUMERIC_CHARACTERS;
     if (x < 26) return $a + x;
     if (x < 52) return $A + x - 26;
     return $0 + x - 52;
   }

 }
	// Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file
	// for details. All rights reserved. Use of this source code is governed by a
	// BSD-style license that can be found in the LICENSE file.

	part of js_backend;

	/**
	* Assigns JavaScript identifiers to Dart variables, class-names and members.
	*/
	class MinifyNamer extends Namer {
	MinifyNamer(Compiler compiler) : super(compiler) {
	reserveBackendNames();
	}

	String get isolateName => 'I';
	String get isolatePropertiesName => 'p';
	bool get shouldMinify => true;

	final String getterPrefix = 'g';
	final String setterPrefix = 's';

	const ALPHABET_CHARACTERS = 52; // a-zA-Z.
	const ALPHANUMERIC_CHARACTERS = 62; // a-zA-Z0-9.

	// You can pass an invalid identifier to this and unlike its non-minifying
	// counterpart it will never return the proposedName as the new fresh name.
	String getFreshName(String proposedName,
	Set<String> usedNames,
	Map<String, String> suggestedNames,
	{bool ensureSafe: true}) {
	var freshName;
	var suggestion = suggestedNames[proposedName];
	if (suggestion != null && !usedNames.contains(suggestion)) {
	freshName = suggestion;
	} else {
	freshName = _getUnusedName(proposedName, usedNames);
	}
	usedNames.add(freshName);
	return freshName;
	}

	SourceString getClosureVariableName(SourceString name, int id) {
	if (id < ALPHABET_CHARACTERS) {
	return new SourceString(new String.fromCharCodes([_letterNumber(id)]));
	}
	return new SourceString("${getMappedInstanceName('closure')}_$id");
	}

	void reserveBackendNames() {
	// From issue 7554. These should not be used on objects (as instance
	// variables) because they clash with names from the DOM.
	const reservedNativeProperties = const <String>[
	'Q', 'a', 'b', 'c', 'd', 'e', 'f', 'r', 'x', 'y', 'z',
	// 2-letter:
	'ch', 'cx', 'cy', 'db', 'dx', 'dy', 'fr', 'fx', 'fy', 'go', 'id', 'k1',
	'k2', 'k3', 'k4', 'r1', 'r2', 'rx', 'ry', 'x1', 'x2', 'y1', 'y2',
	// 3-letter:
	'add', 'all', 'alt', 'arc', 'CCW', 'cmp', 'dir', 'end', 'get', 'in1',
	'in2', 'INT', 'key', 'log', 'low', 'm11', 'm12', 'm13', 'm14', 'm21',
	'm22', 'm23', 'm24', 'm31', 'm32', 'm33', 'm34', 'm41', 'm42', 'm43',
	'm44', 'max', 'min', 'now', 'ONE', 'put', 'red', 'rel', 'rev', 'RGB',
	'sdp', 'set', 'src', 'tag', 'top', 'uid', 'uri', 'url', 'URL',
	// 4-letter:
	'abbr', 'atob', 'Attr', 'axes', 'axis', 'back', 'BACK', 'beta', 'bias',
	'Blob', 'blue', 'blur', 'BLUR', 'body', 'BOOL', 'BOTH', 'btoa', 'BYTE',
	'cite', 'clip', 'code', 'cols', 'cues', 'data', 'DECR', 'DONE', 'face',
	'file', 'File', 'fill', 'find', 'font', 'form', 'gain', 'hash', 'head',
	'high', 'hint', 'host', 'href', 'HRTF', 'IDLE', 'INCR', 'info', 'INIT',
	'isId', 'item', 'KEEP', 'kind', 'knee', 'lang', 'left', 'LESS', 'line',
	'link', 'list', 'load', 'loop', 'mode', 'name', 'Node', 'None', 'NONE',
	'only', 'open', 'OPEN', 'ping', 'play', 'port', 'rect', 'Rect', 'refX',
	'refY', 'RGBA', 'root', 'rows', 'save', 'seed', 'seek', 'self', 'send',
	'show', 'SINE', 'size', 'span', 'stat', 'step', 'stop', 'tags', 'text',
	'Text', 'time', 'type', 'view', 'warn', 'wrap', 'ZERO'];

	for (var name in reservedNativeProperties) {
	if (name.length < 2) {
	instanceNameMap[name] = name;
	}
	usedInstanceNames.add(name);
	// Getter and setter names are autogenerated by prepending 'g' and 's' to
	// field names. Therefore there are some field names we don't want to
	// use. It is implicit in the next line that the banned prefix is
	// only one character.
	if (_hasBannedPrefix(name)) usedInstanceNames.add(name.substring(1));
	}

	// This list of popular instance variable names generated with:
	// cat out.js \|
	// perl -ne '$_=~s/(?<![^a-z0-9_\$]\$)\.([a-z0-9_\$]+)/print("$1\n")/gei' \|
	// sort \| uniq -c \| sort -nr \| head -40
	// Removed: html, call*, hasOwnProperty.
	_populateSuggestedNames(
	suggestedInstanceNames,
	usedInstanceNames,
	const <String>[
	r'$add', r'add$1', r'box_0', r'charCodeAt$1', r'constructor',
	r'current', r'$defineNativeClass', r'$eq', r'$ne',
	r'getPrototypeOf', r'hasOwnProperty', r'$index', r'$indexSet',
	r'$isJavaScriptIndexingBehavior', r'$isolateProperties',
	r'iterator', r'length', r'$lt', r'$gt', r'$le', r'$ge',
	r'moveNext$0', r'node', r'on', r'prototype', r'push', r'self',
	r'start', r'target', r'this_0', r'value', r'width', r'style']);

	_populateSuggestedNames(
	suggestedGlobalNames,
	usedGlobalNames,
	const <String>[
	r'Object', r'$throw', r'$eq', r'S', r'ioore', r'UnsupportedError$',
	r'length', r'$sub', r'getInterceptor$JSArrayJSString', r'$add',
	r'$gt', r'$ge', r'$lt', r'$le', r'add', r'getInterceptor$JSNumber',
	r'iterator', r'$index', r'iae', r'getInterceptor$JSArray',
	r'ArgumentError$', r'BoundClosure', r'StateError$',
	r'getInterceptor', r'max', r'$mul', r'List_List', r'Map_Map',
	r'getInterceptor$JSString', r'$div', r'$indexSet',
	r'List_List$from', r'Set_Set$from', r'toString', r'toInt', r'min',
	r'StringBuffer_StringBuffer', r'contains1', r'WhereIterable$',
	r'RangeError$value', r'JSString', r'JSNumber',
	r'JSArray'
	]);
	}

	void _populateSuggestedNames(Map<String, String> suggestionMap,
	Set<String> used,
	List<String> suggestions) {
	int c = $a - 1;
	String letter;
	for (String name in suggestions) {
	do {
	assert(c != $Z);
	c = (c == $z) ? $A : c + 1;
	letter = new String.fromCharCodes([c]);
	} while (used.contains(letter));
	assert(suggestionMap[name] == null);
	suggestionMap[name] = letter;
	}
	}


	// This gets a minified name based on a hash of the proposed name. This
	// is slightly less efficient than just getting the next name in a series,
	// but it means that small changes in the input program will give smallish
	// changes in the output, which can be useful for diffing etc.
	String _getUnusedName(String proposedName, Set<String> usedNames) {
	int hash = _calculateHash(proposedName);
	// Avoid very small hashes that won't try many names.
	hash = hash < 1000 ? hash * 314159 : hash; // Yes, it's prime.

	// Try other n-character names based on the hash. We try one to three
	// character identifiers. For each length we try around 10 different names
	// in a predictable order determined by the proposed name. This is in order
	// to make the renamer stable: small changes in the input should nornally
	// result in relatively small changes in the output.
	for (var n = 2; n <= 3; n++) {
	int h = hash;
	while (h > 10) {
	var codes = <int>[_letterNumber(h)];
	int h2 = h ~/ ALPHABET_CHARACTERS;
	for (var i = 1; i < n; i++) {
	codes.add(_alphaNumericNumber(h2));
	h2 ~/= ALPHANUMERIC_CHARACTERS;
	}
	final candidate = new String.fromCharCodes(codes);
	if (!usedNames.contains(candidate) &&
	!jsReserved.contains(candidate) &&
	!_hasBannedPrefix(candidate)) {
	return candidate;
	}
	// Try again with a slightly different hash. After around 10 turns
	// around this loop h is zero and we try a longer name.
	h ~/= 7;
	}
	}

	// If we can't find a hash based name in the three-letter space, then base
	// the name on a letter and a counter.
	var startLetter = new String.fromCharCodes([_letterNumber(hash)]);
	var i = 0;
	while (usedNames.contains("$startLetter$i")) {
	i++;
	}
	// We don't need to check for banned prefix because the name is in the form
	// xnnn, where nnn is a number. There can be no getter or setter called
	// gnnn since that would imply a numeric field name.
	return "$startLetter$i";
	}

	/// Instance members starting with g and s are reserved for getters and
	/// setters.
	bool _hasBannedPrefix(String name) {
	int code = name.codeUnitAt(0);
	return code == $g \|\| code == $s;
	}

	int _calculateHash(String name) {
	int h = 0;
	for (int i = 0; i < name.length; i++) {
	h += name.codeUnitAt(i);
	h &= 0xffffffff;
	h += h << 10;
	h &= 0xffffffff;
	h ^= h >> 6;
	h &= 0xffffffff;
	}
	return h;
	}

	int _letterNumber(int x) {
	if (x >= ALPHABET_CHARACTERS) x %= ALPHABET_CHARACTERS;
	if (x < 26) return $a + x;
	return $A + x - 26;
	}

	int _alphaNumericNumber(int x) {
	if (x >= ALPHANUMERIC_CHARACTERS) x %= ALPHANUMERIC_CHARACTERS;
	if (x < 26) return $a + x;
	if (x < 52) return $A + x - 26;
	return $0 + x - 52;
	}

	}