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Rhino is an open-source implementation of JavaScript written entirely in Java. It is typically
embedded into Java applications to provide scripting to end users.
/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
package org.mozilla.javascript;
import org.mozilla.javascript.ast.FunctionNode;
/**
* The following class save decompilation information about the source.
* Source information is returned from the parser as a String
* associated with function nodes and with the toplevel script. When
* saved in the constant pool of a class, this string will be UTF-8
* encoded, and token values will occupy a single byte.
* Source is saved (mostly) as token numbers. The tokens saved pretty
* much correspond to the token stream of a 'canonical' representation
* of the input program, as directed by the parser. (There were a few
* cases where tokens could have been left out where decompiler could
* easily reconstruct them, but I left them in for clarity). (I also
* looked adding source collection to TokenStream instead, where I
* could have limited the changes to a few lines in getToken... but
* this wouldn't have saved any space in the resulting source
* representation, and would have meant that I'd have to duplicate
* parser logic in the decompiler to disambiguate situations where
* newlines are important.) The function decompile expands the
* tokens back into their string representations, using simple
* lookahead to correct spacing and indentation.
*
* Assignments are saved as two-token pairs (Token.ASSIGN, op). Number tokens
* are stored inline, as a NUMBER token, a character representing the type, and
* either 1 or 4 characters representing the bit-encoding of the number. String
* types NAME, STRING and OBJECT are currently stored as a token type,
* followed by a character giving the length of the string (assumed to
* be less than 2^16), followed by the characters of the string
* inlined into the source string. Changing this to some reference to
* to the string in the compiled class' constant pool would probably
* save a lot of space... but would require some method of deriving
* the final constant pool entry from information available at parse
* time.
*/
public class Decompiler
{
/**
* Flag to indicate that the decompilation should omit the
* function header and trailing brace.
*/
public static final int ONLY_BODY_FLAG = 1 << 0;
/**
* Flag to indicate that the decompilation generates toSource result.
*/
public static final int TO_SOURCE_FLAG = 1 << 1;
/**
* Decompilation property to specify initial ident value.
*/
public static final int INITIAL_INDENT_PROP = 1;
/**
* Decompilation property to specify default identation offset.
*/
public static final int INDENT_GAP_PROP = 2;
/**
* Decompilation property to specify identation offset for case labels.
*/
public static final int CASE_GAP_PROP = 3;
// Marker to denote the last RC of function so it can be distinguished from
// the last RC of object literals in case of function expressions
private static final int FUNCTION_END = Token.LAST_TOKEN + 1;
String getEncodedSource()
{
return sourceToString(0);
}
int getCurrentOffset()
{
return sourceTop;
}
int markFunctionStart(int functionType)
{
int savedOffset = getCurrentOffset();
if (functionType != FunctionNode.ARROW_FUNCTION) {
addToken(Token.FUNCTION);
append((char)functionType);
}
return savedOffset;
}
int markFunctionEnd(int functionStart)
{
int offset = getCurrentOffset();
append((char)FUNCTION_END);
return offset;
}
void addToken(int token)
{
if (!(0 <= token && token <= Token.LAST_TOKEN))
throw new IllegalArgumentException();
append((char)token);
}
void addEOL(int token)
{
if (!(0 <= token && token <= Token.LAST_TOKEN))
throw new IllegalArgumentException();
append((char)token);
append((char)Token.EOL);
}
void addName(String str)
{
addToken(Token.NAME);
appendString(str);
}
void addString(String str)
{
addToken(Token.STRING);
appendString(str);
}
void addRegexp(String regexp, String flags)
{
addToken(Token.REGEXP);
appendString('/' + regexp + '/' + flags);
}
void addNumber(double n)
{
addToken(Token.NUMBER);
/* encode the number in the source stream.
* Save as NUMBER type (char | char char char char)
* where type is
* 'D' - double, 'S' - short, 'J' - long.
* We need to retain float vs. integer type info to keep the
* behavior of liveconnect type-guessing the same after
* decompilation. (Liveconnect tries to present 1.0 to Java
* as a float/double)
* OPT: This is no longer true. We could compress the format.
* This may not be the most space-efficient encoding;
* the chars created below may take up to 3 bytes in
* constant pool UTF-8 encoding, so a Double could take
* up to 12 bytes.
*/
long lbits = (long)n;
if (lbits != n) {
// if it's floating point, save as a Double bit pattern.
// (12/15/97 our scanner only returns Double for f.p.)
lbits = Double.doubleToLongBits(n);
append('D');
append((char)(lbits >> 48));
append((char)(lbits >> 32));
append((char)(lbits >> 16));
append((char)lbits);
}
else {
// we can ignore negative values, bc they're already prefixed
// by NEG
if (lbits < 0) Kit.codeBug();
// will it fit in a char?
// this gives a short encoding for integer values up to 2^16.
if (lbits <= Character.MAX_VALUE) {
append('S');
append((char)lbits);
}
else { // Integral, but won't fit in a char. Store as a long.
append('J');
append((char)(lbits >> 48));
append((char)(lbits >> 32));
append((char)(lbits >> 16));
append((char)lbits);
}
}
}
private void appendString(String str)
{
int L = str.length();
int lengthEncodingSize = 1;
if (L >= 0x8000) {
lengthEncodingSize = 2;
}
int nextTop = sourceTop + lengthEncodingSize + L;
if (nextTop > sourceBuffer.length) {
increaseSourceCapacity(nextTop);
}
if (L >= 0x8000) {
// Use 2 chars to encode strings exceeding 32K, were the highest
// bit in the first char indicates presence of the next byte
sourceBuffer[sourceTop] = (char)(0x8000 | (L >>> 16));
++sourceTop;
}
sourceBuffer[sourceTop] = (char)L;
++sourceTop;
str.getChars(0, L, sourceBuffer, sourceTop);
sourceTop = nextTop;
}
private void append(char c)
{
if (sourceTop == sourceBuffer.length) {
increaseSourceCapacity(sourceTop + 1);
}
sourceBuffer[sourceTop] = c;
++sourceTop;
}
private void increaseSourceCapacity(int minimalCapacity)
{
// Call this only when capacity increase is must
if (minimalCapacity <= sourceBuffer.length) Kit.codeBug();
int newCapacity = sourceBuffer.length * 2;
if (newCapacity < minimalCapacity) {
newCapacity = minimalCapacity;
}
char[] tmp = new char[newCapacity];
System.arraycopy(sourceBuffer, 0, tmp, 0, sourceTop);
sourceBuffer = tmp;
}
private String sourceToString(int offset)
{
if (offset < 0 || sourceTop < offset) Kit.codeBug();
return new String(sourceBuffer, offset, sourceTop - offset);
}
/**
* Decompile the source information associated with this js
* function/script back into a string. For the most part, this
* just means translating tokens back to their string
* representations; there's a little bit of lookahead logic to
* decide the proper spacing/indentation. Most of the work in
* mapping the original source to the prettyprinted decompiled
* version is done by the parser.
*
* @param source encoded source tree presentation
*
* @param flags flags to select output format
*
* @param properties indentation properties
*
*/
public static String decompile(String source, int flags,
UintMap properties)
{
int length = source.length();
if (length == 0) { return ""; }
int indent = properties.getInt(INITIAL_INDENT_PROP, 0);
if (indent < 0) throw new IllegalArgumentException();
int indentGap = properties.getInt(INDENT_GAP_PROP, 4);
if (indentGap < 0) throw new IllegalArgumentException();
int caseGap = properties.getInt(CASE_GAP_PROP, 2);
if (caseGap < 0) throw new IllegalArgumentException();
StringBuilder result = new StringBuilder();
boolean justFunctionBody = (0 != (flags & Decompiler.ONLY_BODY_FLAG));
boolean toSource = (0 != (flags & Decompiler.TO_SOURCE_FLAG));
// Spew tokens in source, for debugging.
// as TYPE number char
if (printSource) {
System.err.println("length:" + length);
for (int i = 0; i < length; ++i) {
// Note that tokenToName will fail unless Context.printTrees
// is true.
String tokenname = null;
if (Token.printNames) {
tokenname = Token.name(source.charAt(i));
}
if (tokenname == null) {
tokenname = "---";
}
String pad = tokenname.length() > 7
? "\t"
: "\t\t";
System.err.println
(tokenname
+ pad + (int)source.charAt(i)
+ "\t'" + ScriptRuntime.escapeString
(source.substring(i, i+1))
+ "'");
}
System.err.println();
}
int braceNesting = 0;
boolean afterFirstEOL = false;
int i = 0;
int topFunctionType;
if (source.charAt(i) == Token.SCRIPT) {
++i;
topFunctionType = -1;
} else {
topFunctionType = source.charAt(i + 1);
}
if (!toSource) {
// add an initial newline to exactly match js.
result.append('\n');
for (int j = 0; j < indent; j++)
result.append(' ');
} else {
if (topFunctionType == FunctionNode.FUNCTION_EXPRESSION) {
result.append('(');
}
}
while (i < length) {
switch(source.charAt(i)) {
case Token.GET:
case Token.SET:
case Token.METHOD:
if (source.charAt(i) == Token.GET) {
result.append("get ");
} else if (source.charAt(i) == Token.SET) {
result.append("set ");
}
++i;
i = printSourceString(source, i + 1, false, result);
// Now increment one more to get past the FUNCTION token
++i;
break;
case Token.NAME:
case Token.REGEXP: // re-wrapped in '/'s in parser...
i = printSourceString(source, i + 1, false, result);
continue;
case Token.STRING:
i = printSourceString(source, i + 1, true, result);
continue;
case Token.NUMBER:
i = printSourceNumber(source, i + 1, result);
continue;
case Token.TRUE:
result.append("true");
break;
case Token.FALSE:
result.append("false");
break;
case Token.NULL:
result.append("null");
break;
case Token.THIS:
result.append("this");
break;
case Token.FUNCTION:
++i; // skip function type
result.append("function ");
break;
case FUNCTION_END:
// Do nothing
break;
case Token.COMMA:
result.append(", ");
break;
case Token.LC:
++braceNesting;
if (Token.EOL == getNext(source, length, i))
indent += indentGap;
result.append('{');
break;
case Token.RC: {
--braceNesting;
/* don't print the closing RC if it closes the
* toplevel function and we're called from
* decompileFunctionBody.
*/
if (justFunctionBody && braceNesting == 0)
break;
result.append('}');
switch (getNext(source, length, i)) {
case Token.EOL:
case FUNCTION_END:
indent -= indentGap;
break;
case Token.WHILE:
case Token.ELSE:
indent -= indentGap;
result.append(' ');
break;
}
break;
}
case Token.LP:
result.append('(');
break;
case Token.RP:
result.append(')');
if (Token.LC == getNext(source, length, i))
result.append(' ');
break;
case Token.LB:
result.append('[');
break;
case Token.RB:
result.append(']');
break;
case Token.EOL: {
if (toSource) break;
boolean newLine = true;
if (!afterFirstEOL) {
afterFirstEOL = true;
if (justFunctionBody) {
/* throw away just added 'function name(...) {'
* and restore the original indent
*/
result.setLength(0);
indent -= indentGap;
newLine = false;
}
}
if (newLine) {
result.append('\n');
}
/* add indent if any tokens remain,
* less setback if next token is
* a label, case or default.
*/
if (i + 1 < length) {
int less = 0;
int nextToken = source.charAt(i + 1);
if (nextToken == Token.CASE
|| nextToken == Token.DEFAULT)
{
less = indentGap - caseGap;
} else if (nextToken == Token.RC) {
less = indentGap;
}
/* elaborate check against label... skip past a
* following inlined NAME and look for a COLON.
*/
else if (nextToken == Token.NAME) {
int afterName = getSourceStringEnd(source, i + 2);
if (source.charAt(afterName) == Token.COLON)
less = indentGap;
}
for (; less < indent; less++)
result.append(' ');
}
break;
}
case Token.DOT:
result.append('.');
break;
case Token.NEW:
result.append("new ");
break;
case Token.DELPROP:
result.append("delete ");
break;
case Token.IF:
result.append("if ");
break;
case Token.ELSE:
result.append("else ");
break;
case Token.FOR:
result.append("for ");
break;
case Token.IN:
result.append(" in ");
break;
case Token.WITH:
result.append("with ");
break;
case Token.WHILE:
result.append("while ");
break;
case Token.DO:
result.append("do ");
break;
case Token.TRY:
result.append("try ");
break;
case Token.CATCH:
result.append("catch ");
break;
case Token.FINALLY:
result.append("finally ");
break;
case Token.THROW:
result.append("throw ");
break;
case Token.SWITCH:
result.append("switch ");
break;
case Token.BREAK:
result.append("break");
if (Token.NAME == getNext(source, length, i))
result.append(' ');
break;
case Token.CONTINUE:
result.append("continue");
if (Token.NAME == getNext(source, length, i))
result.append(' ');
break;
case Token.CASE:
result.append("case ");
break;
case Token.DEFAULT:
result.append("default");
break;
case Token.RETURN:
result.append("return");
if (Token.SEMI != getNext(source, length, i))
result.append(' ');
break;
case Token.VAR:
result.append("var ");
break;
case Token.LET:
result.append("let ");
break;
case Token.SEMI:
result.append(';');
if (Token.EOL != getNext(source, length, i)) {
// separators in FOR
result.append(' ');
}
break;
case Token.ASSIGN:
result.append(" = ");
break;
case Token.ASSIGN_ADD:
result.append(" += ");
break;
case Token.ASSIGN_SUB:
result.append(" -= ");
break;
case Token.ASSIGN_MUL:
result.append(" *= ");
break;
case Token.ASSIGN_DIV:
result.append(" /= ");
break;
case Token.ASSIGN_MOD:
result.append(" %= ");
break;
case Token.ASSIGN_BITOR:
result.append(" |= ");
break;
case Token.ASSIGN_BITXOR:
result.append(" ^= ");
break;
case Token.ASSIGN_BITAND:
result.append(" &= ");
break;
case Token.ASSIGN_LSH:
result.append(" <<= ");
break;
case Token.ASSIGN_RSH:
result.append(" >>= ");
break;
case Token.ASSIGN_URSH:
result.append(" >>>= ");
break;
case Token.HOOK:
result.append(" ? ");
break;
case Token.OBJECTLIT:
// pun OBJECTLIT to mean colon in objlit property
// initialization.
// This needs to be distinct from COLON in the general case
// to distinguish from the colon in a ternary... which needs
// different spacing.
result.append(": ");
break;
case Token.COLON:
if (Token.EOL == getNext(source, length, i))
// it's the end of a label
result.append(':');
else
// it's the middle part of a ternary
result.append(" : ");
break;
case Token.OR:
result.append(" || ");
break;
case Token.AND:
result.append(" && ");
break;
case Token.BITOR:
result.append(" | ");
break;
case Token.BITXOR:
result.append(" ^ ");
break;
case Token.BITAND:
result.append(" & ");
break;
case Token.SHEQ:
result.append(" === ");
break;
case Token.SHNE:
result.append(" !== ");
break;
case Token.EQ:
result.append(" == ");
break;
case Token.NE:
result.append(" != ");
break;
case Token.LE:
result.append(" <= ");
break;
case Token.LT:
result.append(" < ");
break;
case Token.GE:
result.append(" >= ");
break;
case Token.GT:
result.append(" > ");
break;
case Token.INSTANCEOF:
result.append(" instanceof ");
break;
case Token.LSH:
result.append(" << ");
break;
case Token.RSH:
result.append(" >> ");
break;
case Token.URSH:
result.append(" >>> ");
break;
case Token.TYPEOF:
result.append("typeof ");
break;
case Token.VOID:
result.append("void ");
break;
case Token.CONST:
result.append("const ");
break;
case Token.YIELD:
result.append("yield ");
break;
case Token.NOT:
result.append('!');
break;
case Token.BITNOT:
result.append('~');
break;
case Token.POS:
result.append('+');
break;
case Token.NEG:
result.append('-');
break;
case Token.INC:
result.append("++");
break;
case Token.DEC:
result.append("--");
break;
case Token.ADD:
result.append(" + ");
break;
case Token.SUB:
result.append(" - ");
break;
case Token.MUL:
result.append(" * ");
break;
case Token.DIV:
result.append(" / ");
break;
case Token.MOD:
result.append(" % ");
break;
case Token.COLONCOLON:
result.append("::");
break;
case Token.DOTDOT:
result.append("..");
break;
case Token.DOTQUERY:
result.append(".(");
break;
case Token.XMLATTR:
result.append('@');
break;
case Token.DEBUGGER:
result.append("debugger;\n");
break;
case Token.ARROW:
result.append(" => ");
break;
default:
// If we don't know how to decompile it, raise an exception.
throw new RuntimeException("Token: " +
Token.name(source.charAt(i)));
}
++i;
}
if (!toSource) {
// add that trailing newline if it's an outermost function.
if (!justFunctionBody)
result.append('\n');
} else {
if (topFunctionType == FunctionNode.FUNCTION_EXPRESSION) {
result.append(')');
}
}
return result.toString();
}
private static int getNext(String source, int length, int i)
{
return (i + 1 < length) ? source.charAt(i + 1) : Token.EOF;
}
private static int getSourceStringEnd(String source, int offset)
{
return printSourceString(source, offset, false, null);
}
private static int printSourceString(String source, int offset,
boolean asQuotedString,
StringBuilder sb)
{
int length = source.charAt(offset);
++offset;
if ((0x8000 & length) != 0) {
length = ((0x7FFF & length) << 16) | source.charAt(offset);
++offset;
}
if (sb != null) {
String str = source.substring(offset, offset + length);
if (!asQuotedString) {
sb.append(str);
} else {
sb.append('"');
sb.append(ScriptRuntime.escapeString(str));
sb.append('"');
}
}
return offset + length;
}
private static int printSourceNumber(String source, int offset,
StringBuilder sb)
{
double number = 0.0;
char type = source.charAt(offset);
++offset;
if (type == 'S') {
if (sb != null) {
int ival = source.charAt(offset);
number = ival;
}
++offset;
} else if (type == 'J' || type == 'D') {
if (sb != null) {
long lbits;
lbits = (long)source.charAt(offset) << 48;
lbits |= (long)source.charAt(offset + 1) << 32;
lbits |= (long)source.charAt(offset + 2) << 16;
lbits |= source.charAt(offset + 3);
if (type == 'J') {
number = lbits;
} else {
number = Double.longBitsToDouble(lbits);
}
}
offset += 4;
} else {
// Bad source
throw new RuntimeException();
}
if (sb != null) {
sb.append(ScriptRuntime.numberToString(number, 10));
}
return offset;
}
private char[] sourceBuffer = new char[128];
// Per script/function source buffer top: parent source does not include a
// nested functions source and uses function index as a reference instead.
private int sourceTop;
// whether to do a debug print of the source information, when decompiling.
private static final boolean printSource = false;
}
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