com.google.javascript.jscomp

Class RenameVars

java.lang.Object

com.google.javascript.jscomp.RenameVars

All Implemented Interfaces:

CompilerPass

final class RenameVars
extends java.lang.Object
implements CompilerPass

RenameVars renames all the variables names into short names, to reduce code size and also to obfuscate the code.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
(package private) class	RenameVars.Assignment
(package private) class	RenameVars.ProcessVars Iterate through the nodes, collect all the NAME nodes that need to be renamed, and count how many times each variable name is referenced.

Field Summary

Fields

Modifier and Type	Field and Description
private int	assignmentCount Counter for each assignment
private java.lang.StringBuilder	assignmentLog Logs all name assignments
private java.util.Map<java.lang.String,RenameVars.Assignment>	assignments Maps an old name to a new name assignment
private AbstractCompiler	compiler
private java.util.Set<java.lang.String>	externNames Set of extern variable names
private static java.util.Comparator<RenameVars.Assignment>	FREQUENCY_COMPARATOR Sorts Assignment objects by their count, breaking ties by their order of occurrence in the source to ensure a deterministic total ordering.
private java.util.ArrayList<Node>	globalNameNodes List of global NAME nodes
static java.lang.String	LOCAL_VAR_PREFIX A prefix to distinguish temporary local names from global names
private java.util.Set<Var>	localBleedingFunctions
private com.google.common.collect.ArrayListMultimap<Scope,Var>	localBleedingFunctionsPerScope
private java.util.ArrayList<Node>	localNameNodes List of local NAME nodes
private boolean	localRenamingOnly Whether renaming should apply to local variables only.
private static int	MAX_LOCALS_IN_SCOPE_TO_TEMP_RENAME Limit on number of locals in a scope for temporary local renaming when preferStableNames is true.
private NameGenerator	nameGenerator
private static java.util.Comparator<RenameVars.Assignment>	ORDER_OF_OCCURRENCE_COMPARATOR Sorts Assignment objects by the order the variable name first appears in the source.
private boolean	preferStableNames
private java.lang.String	prefix The global name prefix
private boolean	preserveFunctionExpressionNames Whether function expression names should be preserved.
private VariableMap	prevUsedRenameMap The previously used rename map.
private java.util.Map<Node,java.lang.String>	pseudoNameMap Maps a name node to its pseudo name, null if we are not generating so there will be no overhead unless we are debugging.
private java.util.Map<java.lang.String,java.lang.String>	renameMap The renaming map
private char[]	reservedCharacters Characters that shouldn't be used in variable names.
private java.util.Set<java.lang.String>	reservedNames Set of reserved variable names
private boolean	shouldShadow

Constructor Summary

Constructors

Constructor and Description
RenameVars(AbstractCompiler compiler, java.lang.String prefix, boolean localRenamingOnly, boolean preserveFunctionExpressionNames, boolean generatePseudoNames, boolean shouldShadow, boolean preferStableNames, VariableMap prevUsedRenameMap, char[] reservedCharacters, java.util.Set<java.lang.String> reservedNames, NameGenerator nameGenerator)

Method Summary

Modifier and Type	Method and Description
private void	assignNames(java.util.SortedSet<RenameVars.Assignment> varsToRename) Determines which new names to substitute for the original names.
private void	finalizeNameAssignment(RenameVars.Assignment a, java.lang.String newName) Makes a final name assignment.
private int	getLocalVarIndex(Var v) Returns the index within the scope stack.
private java.lang.String	getNewGlobalName(Node n)
private java.lang.String	getNewLocalName(Node n)
(package private) VariableMap	getVariableMap() Gets the variable map.
private boolean	okToRenameVar(java.lang.String name, boolean isLocal) Determines whether a variable name is okay to rename.
void	process(Node externs, Node root) Process the JS with root node root.
private void	recordPseudoName(Node n)
private void	reusePreviouslyUsedVariableMap() Runs through the assignments and reuses as many names as possible from the previously used variable map.
private boolean	shouldTemporarilyRenameLocalsInScope(Scope s) Returns true if the local variables in a scope should be given temporary names (eg, 'L 123') prior to renaming to allow reuse of names across scopes.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

MAX_LOCALS_IN_SCOPE_TO_TEMP_RENAME

private static final int MAX_LOCALS_IN_SCOPE_TO_TEMP_RENAME

Limit on number of locals in a scope for temporary local renaming when preferStableNames is true.

See Also:

Constant Field Values

compiler

private final AbstractCompiler compiler

globalNameNodes

private final java.util.ArrayList<Node> globalNameNodes

List of global NAME nodes

localNameNodes

private final java.util.ArrayList<Node> localNameNodes

List of local NAME nodes

pseudoNameMap

private final java.util.Map<Node,java.lang.String> pseudoNameMap

Maps a name node to its pseudo name, null if we are not generating so there will be no overhead unless we are debugging.

externNames

private final java.util.Set<java.lang.String> externNames

Set of extern variable names

reservedNames

private final java.util.Set<java.lang.String> reservedNames

Set of reserved variable names

renameMap

private final java.util.Map<java.lang.String,java.lang.String> renameMap

The renaming map

prevUsedRenameMap

private final VariableMap prevUsedRenameMap

The previously used rename map.

prefix

private final java.lang.String prefix

The global name prefix

assignmentCount

private int assignmentCount

Counter for each assignment

assignmentLog

private java.lang.StringBuilder assignmentLog

Logs all name assignments

localBleedingFunctions

private final java.util.Set<Var> localBleedingFunctions

localBleedingFunctionsPerScope

private final com.google.common.collect.ArrayListMultimap<Scope,Var> localBleedingFunctionsPerScope

assignments

private final java.util.Map<java.lang.String,RenameVars.Assignment> assignments

Maps an old name to a new name assignment

localRenamingOnly

private final boolean localRenamingOnly

Whether renaming should apply to local variables only.

preserveFunctionExpressionNames

private final boolean preserveFunctionExpressionNames

Whether function expression names should be preserved. Typically, for debugging purposes.

See Also:

NameAnonymousFunctions

shouldShadow

private final boolean shouldShadow

preferStableNames

private final boolean preferStableNames

reservedCharacters

private final char[] reservedCharacters

Characters that shouldn't be used in variable names.

LOCAL_VAR_PREFIX

public static final java.lang.String LOCAL_VAR_PREFIX

A prefix to distinguish temporary local names from global names

See Also:

Constant Field Values

nameGenerator

private final NameGenerator nameGenerator

FREQUENCY_COMPARATOR

private static final java.util.Comparator<RenameVars.Assignment> FREQUENCY_COMPARATOR

Sorts Assignment objects by their count, breaking ties by their order of occurrence in the source to ensure a deterministic total ordering.

ORDER_OF_OCCURRENCE_COMPARATOR

private static final java.util.Comparator<RenameVars.Assignment> ORDER_OF_OCCURRENCE_COMPARATOR

Sorts Assignment objects by the order the variable name first appears in the source.

Constructor Detail

RenameVars

RenameVars(AbstractCompiler compiler,
           java.lang.String prefix,
           boolean localRenamingOnly,
           boolean preserveFunctionExpressionNames,
           boolean generatePseudoNames,
           boolean shouldShadow,
           boolean preferStableNames,
           VariableMap prevUsedRenameMap,
           @Nullable
           char[] reservedCharacters,
           @Nullable
           java.util.Set<java.lang.String> reservedNames,
           NameGenerator nameGenerator)

Method Detail

process

public void process(Node externs,
                    Node root)

Description copied from interface: CompilerPass

Process the JS with root node root. Can modify the contents of each Node tree

Specified by:

process in interface CompilerPass

Parameters:

externs - Top of external JS tree

root - Top of JS tree

getNewGlobalName

private java.lang.String getNewGlobalName(Node n)

getNewLocalName

private java.lang.String getNewLocalName(Node n)

recordPseudoName

private void recordPseudoName(Node n)

reusePreviouslyUsedVariableMap

private void reusePreviouslyUsedVariableMap()

Runs through the assignments and reuses as many names as possible from the previously used variable map. Updates reservedNames with the set of names that were reused.

assignNames

private void assignNames(java.util.SortedSet<RenameVars.Assignment> varsToRename)

Determines which new names to substitute for the original names.

finalizeNameAssignment

private void finalizeNameAssignment(RenameVars.Assignment a,
                                    java.lang.String newName)

Makes a final name assignment.

getVariableMap

VariableMap getVariableMap()

Gets the variable map.

okToRenameVar

private boolean okToRenameVar(java.lang.String name,
                              boolean isLocal)

Determines whether a variable name is okay to rename.

getLocalVarIndex

private int getLocalVarIndex(Var v)

Returns the index within the scope stack. e.g. function Foo(a) { var b; function c(d) { } } a = 0, b = 1, c = 2, d = 3

shouldTemporarilyRenameLocalsInScope

private boolean shouldTemporarilyRenameLocalsInScope(Scope s)

Returns true if the local variables in a scope should be given temporary names (eg, 'L 123') prior to renaming to allow reuse of names across scopes. With preferStableNames, temporary renaming is disabled if the number of locals in the scope is above a heuristic threshold to allow effective reuse of rename maps (see prevUsedRenameMap). In scopes with many variables the temporary name given to a variable is unlikely to be the same temporary name used when the rename map was created.