Move dart2js from sdk/lib/_internal/compiler to pkg/compiler

sdk/lib/_internal/compiler/implementation/js_backend/minify_namer.dart

-// 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';
-  final String callPrefix = ''; // this will create function names $<n>
-
-  static const ALPHABET_CHARACTERS = 52;  // a-zA-Z.
-  static const ALPHANUMERIC_CHARACTERS = 62;  // a-zA-Z0-9.
-
-  // You can pass an invalid identifier to this and unlike its non-minifying
-  // counterpart it will never return the proposedName as the new fresh name.
-  String getFreshName(String proposedName,
-                      Set<String> usedNames,
-                      Map<String, String> suggestedNames,
-                      {bool ensureSafe: true}) {
-    var freshName;
-    var suggestion = suggestedNames[proposedName];
-    if (suggestion != null && !usedNames.contains(suggestion)) {
-      freshName = suggestion;
-    } else {
-      freshName = _getUnusedName(proposedName, usedNames);
-    }
-    usedNames.add(freshName);
-    return freshName;
-  }
-
-  String getClosureVariableName(String name, int id) {
-    if (id < ALPHABET_CHARACTERS) {
-      return new String.fromCharCodes([_letterNumber(id)]);
-    }
-    return "${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));
-    }
-
-    // These popular names are present in most programs and deserve
-    // single character minified names.  We could determine the popular names
-    // individually per program, but that would mean that the output of the
-    // minifier was less stable from version to version of the program being
-    // minified.
-    _populateSuggestedNames(
-        suggestedInstanceNames,
-        usedInstanceNames,
-        const <String>[
-            r'$add', r'add$1', r'$and', r'codeUnitAt$1', r'$or',
-            r'current', r'$shr', r'$eq', r'$ne',
-            r'getPrototypeOf', r'hasOwnProperty', r'$index', r'$indexSet',
-            r'$isJavaScriptIndexingBehavior', r'$xor',
-            r'iterator', r'length', r'$lt', r'$gt', r'$le', r'$ge',
-            r'moveNext$0', r'node', r'on', r'$negate', r'push', r'self',
-            r'start', r'target', r'$shl', r'value', r'width', r'style',
-            r'noSuchMethod$1', r'$mul', r'$div', r'$sub', r'$not', r'$mod',
-            r'$tdiv']);
-
-    _populateSuggestedNames(
-        suggestedGlobalNames,
-        usedGlobalNames,
-        const <String>[
-            r'Object', 'wrapException', r'$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', r'createInvocationMirror'
-            ]);
-  }
-
-  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;
-  }
-
-}