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author | Alex Lam S.L <alexlamsl@gmail.com> | 2017-11-19 19:29:51 +0800 |
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committer | GitHub <noreply@github.com> | 2017-11-19 19:29:51 +0800 |
commit | f4e2fb9864a8c5dd6fb24870c4c09761b5914f75 (patch) | |
tree | 99c3b5be676fa17879db559319b084ce942df58f /lib/scope.js | |
parent | b80062c490178552f45fe66acfa04e6d9c3a6363 (diff) | |
download | tracifyjs-f4e2fb9864a8c5dd6fb24870c4c09761b5914f75.tar.gz tracifyjs-f4e2fb9864a8c5dd6fb24870c4c09761b5914f75.zip |
expand symbol space to improve compression (#2460)
- give globally distinct names to distinct variables
- improve ability to compress cross-scoped
- introduce `options.rename` to `minify()`
- default `true` if both `compress` & `mangle`
Diffstat (limited to 'lib/scope.js')
-rw-r--r-- | lib/scope.js | 95 |
1 files changed, 74 insertions, 21 deletions
diff --git a/lib/scope.js b/lib/scope.js index 0d2a7aeb..ea35c0bf 100644 --- a/lib/scope.js +++ b/lib/scope.js @@ -43,7 +43,7 @@ "use strict"; -function SymbolDef(scope, index, orig) { +function SymbolDef(scope, orig) { this.name = orig.name; this.orig = [ orig ]; this.eliminated = 0; @@ -53,7 +53,6 @@ function SymbolDef(scope, index, orig) { this.global = false; this.mangled_name = null; this.undeclared = false; - this.index = index; this.id = SymbolDef.next_id++; }; @@ -253,7 +252,7 @@ AST_Toplevel.DEFMETHOD("def_global", function(node){ if (globals.has(name)) { return globals.get(name); } else { - var g = new SymbolDef(this, globals.size(), node); + var g = new SymbolDef(this, node); g.undeclared = true; g.global = true; globals.set(name, g); @@ -314,7 +313,7 @@ AST_Scope.DEFMETHOD("def_function", function(symbol){ AST_Scope.DEFMETHOD("def_variable", function(symbol){ var def; if (!this.variables.has(symbol.name)) { - def = new SymbolDef(this, this.variables.size(), symbol); + def = new SymbolDef(this, symbol); this.variables.set(symbol.name, def); def.global = !this.parent_scope; } else { @@ -332,7 +331,7 @@ AST_Scope.DEFMETHOD("next_mangled", function(options){ // https://github.com/mishoo/UglifyJS2/issues/242 -- do not // shadow a name reserved from mangling. - if (options.reserved.indexOf(m) >= 0) continue; + if (member(m, options.reserved)) continue; // we must ensure that the mangled name does not shadow a name // from some parent scope that is referenced in this or in @@ -384,7 +383,7 @@ AST_Symbol.DEFMETHOD("global", function(){ return this.definition().global; }); -AST_Toplevel.DEFMETHOD("_default_mangler_options", function(options){ +AST_Toplevel.DEFMETHOD("_default_mangler_options", function(options) { options = defaults(options, { eval : false, ie8 : false, @@ -393,15 +392,14 @@ AST_Toplevel.DEFMETHOD("_default_mangler_options", function(options){ toplevel : false, }); if (!Array.isArray(options.reserved)) options.reserved = []; + // Never mangle arguments + push_uniq(options.reserved, "arguments"); return options; }); AST_Toplevel.DEFMETHOD("mangle_names", function(options){ options = this._default_mangler_options(options); - // Never mangle arguments - options.reserved.push('arguments'); - // We only need to mangle declaration nodes. Special logic wired // into the code generator will display the mangled name if it's // present (and for AST_SymbolRef-s it'll use the mangled name of @@ -410,11 +408,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){ var to_mangle = []; if (options.cache) { - this.globals.each(function(symbol){ - if (options.reserved.indexOf(symbol.name) < 0) { - to_mangle.push(symbol); - } - }); + this.globals.each(collect); } var tw = new TreeWalker(function(node, descend){ @@ -426,13 +420,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){ return true; // don't descend again in TreeWalker } if (node instanceof AST_Scope) { - var p = tw.parent(), a = []; - node.variables.each(function(symbol){ - if (options.reserved.indexOf(symbol.name) < 0) { - a.push(symbol); - } - }); - to_mangle.push.apply(to_mangle, a); + node.variables.each(collect); return; } if (node instanceof AST_Label) { @@ -452,6 +440,71 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){ if (options.cache) { options.cache.cname = this.cname; } + + function collect(symbol) { + if (!member(symbol.name, options.reserved)) { + to_mangle.push(symbol); + } + } +}); + +AST_Toplevel.DEFMETHOD("find_unique_prefix", function(options) { + var letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_"; + var cache = options.cache && options.cache.props; + var prefixes = Object.create(null); + options.reserved.forEach(add_prefix); + this.globals.each(add_def); + this.walk(new TreeWalker(function(node) { + if (node instanceof AST_Scope) node.variables.each(add_def); + })); + var prefix, i = 0; + do { + prefix = create_name(i++); + } while (prefixes[prefix]); + return prefix; + + function add_prefix(name) { + if (/[0-9]$/.test(name)) { + prefixes[name.replace(/[0-9]+$/, "")] = true; + } + } + + function add_def(def) { + var name = def.name; + if (def.global && cache && cache.has(name)) name = cache.get(name); + else if (!def.unmangleable(options)) return; + add_prefix(name); + } + + function create_name(num) { + var name = ""; + do { + name += letters[num % letters.length]; + num = Math.floor(num / letters.length); + } while (num); + return name; + } +}); + +AST_Toplevel.DEFMETHOD("expand_names", function(options) { + options = this._default_mangler_options(options); + var prefix = this.find_unique_prefix(options); + this.globals.each(rename); + this.walk(new TreeWalker(function(node) { + if (node instanceof AST_Scope) node.variables.each(rename); + })); + + function rename(def) { + if (def.global || def.unmangleable(options)) return; + if (member(def.name, options.reserved)) return; + var name = prefix + def.id; + def.orig.forEach(function(sym) { + sym.name = name; + }); + def.references.forEach(function(sym) { + sym.name = name; + }); + } }); AST_Toplevel.DEFMETHOD("compute_char_frequency", function(options){ |