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⏎ sun/invoke/util/BytecodeName.java
/*
* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package sun.invoke.util;
/**
* Utility routines for dealing with bytecode-level names.
* Includes universal mangling rules for the JVM.
*
* <h3>Avoiding Dangerous Characters </h3>
*
* <p>
* The JVM defines a very small set of characters which are illegal
* in name spellings. We will slightly extend and regularize this set
* into a group of <cite>dangerous characters</cite>.
* These characters will then be replaced, in mangled names, by escape sequences.
* In addition, accidental escape sequences must be further escaped.
* Finally, a special prefix will be applied if and only if
* the mangling would otherwise fail to begin with the escape character.
* This happens to cover the corner case of the null string,
* and also clearly marks symbols which need demangling.
* </p>
* <p>
* Dangerous characters are the union of all characters forbidden
* or otherwise restricted by the JVM specification,
* plus their mates, if they are brackets
* (<code><big><b>[</b></big></code> and <code><big><b>]</b></big></code>,
* <code><big><b><</b></big></code> and <code><big><b>></b></big></code>),
* plus, arbitrarily, the colon character <code><big><b>:</b></big></code>.
* There is no distinction between type, method, and field names.
* This makes it easier to convert between mangled names of different
* types, since they do not need to be decoded (demangled).
* </p>
* <p>
* The escape character is backslash <code><big><b>\</b></big></code>
* (also known as reverse solidus).
* This character is, until now, unheard of in bytecode names,
* but traditional in the proposed role.
*
* </p>
* <h3> Replacement Characters </h3>
*
*
* <p>
* Every escape sequence is two characters
* (in fact, two UTF8 bytes) beginning with
* the escape character and followed by a
* <cite>replacement character</cite>.
* (Since the replacement character is never a backslash,
* iterated manglings do not double in size.)
* </p>
* <p>
* Each dangerous character has some rough visual similarity
* to its corresponding replacement character.
* This makes mangled symbols easier to recognize by sight.
* </p>
* <p>
* The dangerous characters are
* <code><big><b>/</b></big></code> (forward slash, used to delimit package components),
* <code><big><b>.</b></big></code> (dot, also a package delimiter),
* <code><big><b>;</b></big></code> (semicolon, used in signatures),
* <code><big><b>$</b></big></code> (dollar, used in inner classes and synthetic members),
* <code><big><b><</b></big></code> (left angle),
* <code><big><b>></b></big></code> (right angle),
* <code><big><b>[</b></big></code> (left square bracket, used in array types),
* <code><big><b>]</b></big></code> (right square bracket, reserved in this scheme for language use),
* and <code><big><b>:</b></big></code> (colon, reserved in this scheme for language use).
* Their replacements are, respectively,
* <code><big><b>|</b></big></code> (vertical bar),
* <code><big><b>,</b></big></code> (comma),
* <code><big><b>?</b></big></code> (question mark),
* <code><big><b>%</b></big></code> (percent),
* <code><big><b>^</b></big></code> (caret),
* <code><big><b>_</b></big></code> (underscore), and
* <code><big><b>{</b></big></code> (left curly bracket),
* <code><big><b>}</b></big></code> (right curly bracket),
* <code><big><b>!</b></big></code> (exclamation mark).
* In addition, the replacement character for the escape character itself is
* <code><big><b>-</b></big></code> (hyphen),
* and the replacement character for the null prefix is
* <code><big><b>=</b></big></code> (equal sign).
* </p>
* <p>
* An escape character <code><big><b>\</b></big></code>
* followed by any of these replacement characters
* is an escape sequence, and there are no other escape sequences.
* An equal sign is only part of an escape sequence
* if it is the second character in the whole string, following a backslash.
* Two consecutive backslashes do <em>not</em> form an escape sequence.
* </p>
* <p>
* Each escape sequence replaces a so-called <cite>original character</cite>
* which is either one of the dangerous characters or the escape character.
* A null prefix replaces an initial null string, not a character.
* </p>
* <p>
* All this implies that escape sequences cannot overlap and may be
* determined all at once for a whole string. Note that a spelling
* string can contain <cite>accidental escapes</cite>, apparent escape
* sequences which must not be interpreted as manglings.
* These are disabled by replacing their leading backslash with an
* escape sequence (<code><big><b>\-</b></big></code>). To mangle a string, three logical steps
* are required, though they may be carried out in one pass:
* </p>
* <ol>
* <li>In each accidental escape, replace the backslash with an escape sequence
* (<code><big><b>\-</b></big></code>).</li>
* <li>Replace each dangerous character with an escape sequence
* (<code><big><b>\|</b></big></code> for <code><big><b>/</b></big></code>, etc.).</li>
* <li>If the first two steps introduced any change, <em>and</em>
* if the string does not already begin with a backslash, prepend a null prefix (<code><big><b>\=</b></big></code>).</li>
* </ol>
*
* To demangle a mangled string that begins with an escape,
* remove any null prefix, and then replace (in parallel)
* each escape sequence by its original character.
* <p>Spelling strings which contain accidental
* escapes <em>must</em> have them replaced, even if those
* strings do not contain dangerous characters.
* This restriction means that mangling a string always
* requires a scan of the string for escapes.
* But then, a scan would be required anyway,
* to check for dangerous characters.
*
* </p>
* <h3> Nice Properties </h3>
*
* <p>
* If a bytecode name does not contain any escape sequence,
* demangling is a no-op: The string demangles to itself.
* Such a string is called <cite>self-mangling</cite>.
* Almost all strings are self-mangling.
* In practice, to demangle almost any name “found in nature”,
* simply verify that it does not begin with a backslash.
* </p>
* <p>
* Mangling is a one-to-one function, while demangling
* is a many-to-one function.
* A mangled string is defined as <cite>validly mangled</cite> if
* it is in fact the unique mangling of its spelling string.
* Three examples of invalidly mangled strings are <code><big><b>\=foo</b></big></code>,
* <code><big><b>\-bar</b></big></code>, and <code><big><b>baz\!</b></big></code>, which demangle to <code><big><b>foo</b></big></code>, <code><big><b>\bar</b></big></code>, and
* <code><big><b>baz\!</b></big></code>, but then remangle to <code><big><b>foo</b></big></code>, <code><big><b>\bar</b></big></code>, and <code><big><b>\=baz\-!</b></big></code>.
* If a language back-end or runtime is using mangled names,
* it should never present an invalidly mangled bytecode
* name to the JVM. If the runtime encounters one,
* it should also report an error, since such an occurrence
* probably indicates a bug in name encoding which
* will lead to errors in linkage.
* However, this note does not propose that the JVM verifier
* detect invalidly mangled names.
* </p>
* <p>
* As a result of these rules, it is a simple matter to
* compute validly mangled substrings and concatenations
* of validly mangled strings, and (with a little care)
* these correspond to corresponding operations on their
* spelling strings.
* </p>
* <ul>
* <li>Any prefix of a validly mangled string is also validly mangled,
* although a null prefix may need to be removed.</li>
* <li>Any suffix of a validly mangled string is also validly mangled,
* although a null prefix may need to be added.</li>
* <li>Two validly mangled strings, when concatenated,
* are also validly mangled, although any null prefix
* must be removed from the second string,
* and a trailing backslash on the first string may need escaping,
* if it would participate in an accidental escape when followed
* by the first character of the second string.</li>
* </ul>
* <p>If languages that include non-Java symbol spellings use this
* mangling convention, they will enjoy the following advantages:
* </p>
* <ul>
* <li>They can interoperate via symbols they share in common.</li>
* <li>Low-level tools, such as backtrace printers, will have readable displays.</li>
* <li>Future JVM and language extensions can safely use the dangerous characters
* for structuring symbols, but will never interfere with valid spellings.</li>
* <li>Runtimes and compilers can use standard libraries for mangling and demangling.</li>
* <li>Occasional transliterations and name composition will be simple and regular,
* for classes, methods, and fields.</li>
* <li>Bytecode names will continue to be compact.
* When mangled, spellings will at most double in length, either in
* UTF8 or UTF16 format, and most will not change at all.</li>
* </ul>
*
*
* <h3> Suggestions for Human Readable Presentations </h3>
*
*
* <p>
* For human readable displays of symbols,
* it will be better to present a string-like quoted
* representation of the spelling, because JVM users
* are generally familiar with such tokens.
* We suggest using single or double quotes before and after
* mangled symbols which are not valid Java identifiers,
* with quotes, backslashes, and non-printing characters
* escaped as if for literals in the Java language.
* </p>
* <p>
* For example, an HTML-like spelling
* <code><big><b><pre></b></big></code> mangles to
* <code><big><b>\^pre\_</b></big></code> and could
* display more cleanly as
* <code><big><b>'<pre>'</b></big></code>,
* with the quotes included.
* Such string-like conventions are <em>not</em> suitable
* for mangled bytecode names, in part because
* dangerous characters must be eliminated, rather
* than just quoted. Otherwise internally structured
* strings like package prefixes and method signatures
* could not be reliably parsed.
* </p>
* <p>
* In such human-readable displays, invalidly mangled
* names should <em>not</em> be demangled and quoted,
* for this would be misleading. Likewise, JVM symbols
* which contain dangerous characters (like dots in field
* names or brackets in method names) should not be
* simply quoted. The bytecode names
* <code><big><b>\=phase\,1</b></big></code> and
* <code><big><b>phase.1</b></big></code> are distinct,
* and in demangled displays they should be presented as
* <code><big><b>'phase.1'</b></big></code> and something like
* <code><big><b>'phase'.1</b></big></code>, respectively.
* </p>
*
* @author John Rose
* @version 1.2, 02/06/2008
* @see http://blogs.sun.com/jrose/entry/symbolic_freedom_in_the_vm
*/
public class BytecodeName {
private BytecodeName() { } // static only class
/** Given a source name, produce the corresponding bytecode name.
* The source name should not be qualified, because any syntactic
* markers (dots, slashes, dollar signs, colons, etc.) will be mangled.
* @param s the source name
* @return a valid bytecode name which represents the source name
*/
public static String toBytecodeName(String s) {
String bn = mangle(s);
assert((Object)bn == s || looksMangled(bn)) : bn;
assert(s.equals(toSourceName(bn))) : s;
return bn;
}
/** Given an unqualified bytecode name, produce the corresponding source name.
* The bytecode name must not contain dangerous characters.
* In particular, it must not be qualified or segmented by colon {@code ':'}.
* @param s the bytecode name
* @return the source name, which may possibly have unsafe characters
* @throws IllegalArgumentException if the bytecode name is not {@link #isSafeBytecodeName safe}
* @see #isSafeBytecodeName(java.lang.String)
*/
public static String toSourceName(String s) {
checkSafeBytecodeName(s);
String sn = s;
if (looksMangled(s)) {
sn = demangle(s);
assert(s.equals(mangle(sn))) : s+" => "+sn+" => "+mangle(sn);
}
return sn;
}
/**
* Given a bytecode name from a classfile, separate it into
* components delimited by dangerous characters.
* Each resulting array element will be either a dangerous character,
* or else a safe bytecode name.
* (The safe name might possibly be mangled to hide further dangerous characters.)
* For example, the qualified class name {@code java/lang/String}
* will be parsed into the array {@code {"java", '/', "lang", '/', "String"}}.
* The name {@code <init>} will be parsed into {@code {'<', "init", '>'}}.
* The name {@code foo/bar$:baz} will be parsed into
* {@code {"foo", '/', "bar", '$', ':', "baz"}}.
* The name {@code ::\=:foo:\=bar\!baz} will be parsed into
* {@code {':', ':', "", ':', "foo", ':', "bar:baz"}}.
*/
public static Object[] parseBytecodeName(String s) {
int slen = s.length();
Object[] res = null;
for (int pass = 0; pass <= 1; pass++) {
int fillp = 0;
int lasti = 0;
for (int i = 0; i <= slen; i++) {
int whichDC = -1;
if (i < slen) {
whichDC = DANGEROUS_CHARS.indexOf(s.charAt(i));
if (whichDC < DANGEROUS_CHAR_FIRST_INDEX) continue;
}
// got to end of string or next dangerous char
if (lasti < i) {
// normal component
if (pass != 0)
res[fillp] = toSourceName(s.substring(lasti, i));
fillp++;
lasti = i+1;
}
if (whichDC >= DANGEROUS_CHAR_FIRST_INDEX) {
if (pass != 0)
res[fillp] = DANGEROUS_CHARS_CA[whichDC];
fillp++;
lasti = i+1;
}
}
if (pass != 0) break;
// between passes, build the result array
res = new Object[fillp];
if (fillp <= 1 && lasti == 0) {
if (fillp != 0) res[0] = toSourceName(s);
break;
}
}
return res;
}
/**
* Given a series of components, create a bytecode name for a classfile.
* This is the inverse of {@link #parseBytecodeName(java.lang.String)}.
* Each component must either be an interned one-character string of
* a dangerous character, or else a safe bytecode name.
* @param components a series of name components
* @return the concatenation of all components
* @throws IllegalArgumentException if any component contains an unsafe
* character, and is not an interned one-character string
* @throws NullPointerException if any component is null
*/
public static String unparseBytecodeName(Object[] components) {
Object[] components0 = components;
for (int i = 0; i < components.length; i++) {
Object c = components[i];
if (c instanceof String) {
String mc = toBytecodeName((String) c);
if (i == 0 && components.length == 1)
return mc; // usual case
if ((Object)mc != c) {
if (components == components0)
components = components.clone();
components[i] = c = mc;
}
}
}
return appendAll(components);
}
private static String appendAll(Object[] components) {
if (components.length <= 1) {
if (components.length == 1) {
return String.valueOf(components[0]);
}
return "";
}
int slen = 0;
for (Object c : components) {
if (c instanceof String)
slen += String.valueOf(c).length();
else
slen += 1;
}
StringBuilder sb = new StringBuilder(slen);
for (Object c : components) {
sb.append(c);
}
return sb.toString();
}
/**
* Given a bytecode name, produce the corresponding display name.
* This is the source name, plus quotes if needed.
* If the bytecode name contains dangerous characters,
* assume that they are being used as punctuation,
* and pass them through unchanged.
* Non-empty runs of non-dangerous characters are demangled
* if necessary, and the resulting names are quoted if
* they are not already valid Java identifiers, or if
* they contain a dangerous character (i.e., dollar sign "$").
* Single quotes are used when quoting.
* Within quoted names, embedded single quotes and backslashes
* are further escaped by prepended backslashes.
*
* @param s the original bytecode name (which may be qualified)
* @return a human-readable presentation
*/
public static String toDisplayName(String s) {
Object[] components = parseBytecodeName(s);
for (int i = 0; i < components.length; i++) {
if (!(components[i] instanceof String))
continue;
String sn = (String) components[i];
// note that the name is already demangled!
//sn = toSourceName(sn);
if (!isJavaIdent(sn) || sn.indexOf('$') >=0 ) {
components[i] = quoteDisplay(sn);
}
}
return appendAll(components);
}
private static boolean isJavaIdent(String s) {
int slen = s.length();
if (slen == 0) return false;
if (!Character.isJavaIdentifierStart(s.charAt(0)))
return false;
for (int i = 1; i < slen; i++) {
if (!Character.isJavaIdentifierPart(s.charAt(i)))
return false;
}
return true;
}
private static String quoteDisplay(String s) {
// TO DO: Replace wierd characters in s by C-style escapes.
return "'"+s.replaceAll("['\\\\]", "\\\\$0")+"'";
}
private static void checkSafeBytecodeName(String s)
throws IllegalArgumentException {
if (!isSafeBytecodeName(s)) {
throw new IllegalArgumentException(s);
}
}
/**
* Report whether a simple name is safe as a bytecode name.
* Such names are acceptable in class files as class, method, and field names.
* Additionally, they are free of "dangerous" characters, even if those
* characters are legal in some (or all) names in class files.
* @param s the proposed bytecode name
* @return true if the name is non-empty and all of its characters are safe
*/
public static boolean isSafeBytecodeName(String s) {
if (s.length() == 0) return false;
// check occurrences of each DANGEROUS char
for (char xc : DANGEROUS_CHARS_A) {
if (xc == ESCAPE_C) continue; // not really that dangerous
if (s.indexOf(xc) >= 0) return false;
}
return true;
}
/**
* Report whether a character is safe in a bytecode name.
* This is true of any unicode character except the following
* <em>dangerous characters</em>: {@code ".;:$[]<>/"}.
* @param c the proposed character
* @return true if the character is safe to use in classfiles
*/
public static boolean isSafeBytecodeChar(char c) {
return DANGEROUS_CHARS.indexOf(c) < DANGEROUS_CHAR_FIRST_INDEX;
}
private static boolean looksMangled(String s) {
return s.charAt(0) == ESCAPE_C;
}
private static String mangle(String s) {
if (s.length() == 0)
return NULL_ESCAPE;
// build this lazily, when we first need an escape:
StringBuilder sb = null;
for (int i = 0, slen = s.length(); i < slen; i++) {
char c = s.charAt(i);
boolean needEscape = false;
if (c == ESCAPE_C) {
if (i+1 < slen) {
char c1 = s.charAt(i+1);
if ((i == 0 && c1 == NULL_ESCAPE_C)
|| c1 != originalOfReplacement(c1)) {
// an accidental escape
needEscape = true;
}
}
} else {
needEscape = isDangerous(c);
}
if (!needEscape) {
if (sb != null) sb.append(c);
continue;
}
// build sb if this is the first escape
if (sb == null) {
sb = new StringBuilder(s.length()+10);
// mangled names must begin with a backslash:
if (s.charAt(0) != ESCAPE_C && i > 0)
sb.append(NULL_ESCAPE);
// append the string so far, which is unremarkable:
sb.append(s, 0, i);
}
// rewrite \ to \-, / to \|, etc.
sb.append(ESCAPE_C);
sb.append(replacementOf(c));
}
if (sb != null) return sb.toString();
return s;
}
private static String demangle(String s) {
// build this lazily, when we first meet an escape:
StringBuilder sb = null;
int stringStart = 0;
if (s.startsWith(NULL_ESCAPE))
stringStart = 2;
for (int i = stringStart, slen = s.length(); i < slen; i++) {
char c = s.charAt(i);
if (c == ESCAPE_C && i+1 < slen) {
// might be an escape sequence
char rc = s.charAt(i+1);
char oc = originalOfReplacement(rc);
if (oc != rc) {
// build sb if this is the first escape
if (sb == null) {
sb = new StringBuilder(s.length());
// append the string so far, which is unremarkable:
sb.append(s, stringStart, i);
}
++i; // skip both characters
c = oc;
}
}
if (sb != null)
sb.append(c);
}
if (sb != null) return sb.toString();
return s.substring(stringStart);
}
static char ESCAPE_C = '\\';
// empty escape sequence to avoid a null name or illegal prefix
static char NULL_ESCAPE_C = '=';
static String NULL_ESCAPE = ESCAPE_C+""+NULL_ESCAPE_C;
static final String DANGEROUS_CHARS = "\\/.;:$[]<>"; // \\ must be first
static final String REPLACEMENT_CHARS = "-|,?!%{}^_";
static final int DANGEROUS_CHAR_FIRST_INDEX = 1; // index after \\
static char[] DANGEROUS_CHARS_A = DANGEROUS_CHARS.toCharArray();
static char[] REPLACEMENT_CHARS_A = REPLACEMENT_CHARS.toCharArray();
static final Character[] DANGEROUS_CHARS_CA;
static {
Character[] dcca = new Character[DANGEROUS_CHARS.length()];
for (int i = 0; i < dcca.length; i++)
dcca[i] = Character.valueOf(DANGEROUS_CHARS.charAt(i));
DANGEROUS_CHARS_CA = dcca;
}
static final long[] SPECIAL_BITMAP = new long[2]; // 128 bits
static {
String SPECIAL = DANGEROUS_CHARS + REPLACEMENT_CHARS;
//System.out.println("SPECIAL = "+SPECIAL);
for (char c : SPECIAL.toCharArray()) {
SPECIAL_BITMAP[c >>> 6] |= 1L << c;
}
}
static boolean isSpecial(char c) {
if ((c >>> 6) < SPECIAL_BITMAP.length)
return ((SPECIAL_BITMAP[c >>> 6] >> c) & 1) != 0;
else
return false;
}
static char replacementOf(char c) {
if (!isSpecial(c)) return c;
int i = DANGEROUS_CHARS.indexOf(c);
if (i < 0) return c;
return REPLACEMENT_CHARS.charAt(i);
}
static char originalOfReplacement(char c) {
if (!isSpecial(c)) return c;
int i = REPLACEMENT_CHARS.indexOf(c);
if (i < 0) return c;
return DANGEROUS_CHARS.charAt(i);
}
static boolean isDangerous(char c) {
if (!isSpecial(c)) return false;
return (DANGEROUS_CHARS.indexOf(c) >= DANGEROUS_CHAR_FIRST_INDEX);
}
static int indexOfDangerousChar(String s, int from) {
for (int i = from, slen = s.length(); i < slen; i++) {
if (isDangerous(s.charAt(i)))
return i;
}
return -1;
}
static int lastIndexOfDangerousChar(String s, int from) {
for (int i = Math.min(from, s.length()-1); i >= 0; i--) {
if (isDangerous(s.charAt(i)))
return i;
}
return -1;
}
}
⏎ sun/invoke/util/BytecodeName.java
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