|
/*
* Copyright (c) 1997, 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "cds/metaspaceShared.hpp"
#include "classfile/altHashing.hpp"
#include "classfile/classLoaderData.hpp"
#include "classfile/vmSymbols.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/symbol.hpp"
#include "runtime/atomic.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/os.hpp"
#include "runtime/signature.hpp"
#include "utilities/stringUtils.hpp"
#include "utilities/utf8.hpp"
Symbol* Symbol::_vm_symbols[vmSymbols::number_of_symbols()];
uint32_t Symbol::pack_hash_and_refcount(short hash, int refcount) {
STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1));
assert(refcount >= 0, "negative refcount");
assert(refcount <= PERM_REFCOUNT, "invalid refcount");
uint32_t hi = hash;
uint32_t lo = refcount;
return (hi << 16) | lo;
}
Symbol::Symbol(const u1* name, int length, int refcount) {
_hash_and_refcount = pack_hash_and_refcount((short)os::random(), refcount);
_length = length;
// _body[0..1] are allocated in the header just by coincidence in the current
// implementation of Symbol. They are read by identity_hash(), so make sure they
// are initialized.
// No other code should assume that _body[0..1] are always allocated. E.g., do
// not unconditionally read base()[0] as that will be invalid for an empty Symbol.
_body[0] = _body[1] = 0;
memcpy(_body, name, length);
}
void* Symbol::operator new(size_t sz, int len) throw() {
#if INCLUDE_CDS
if (DumpSharedSpaces) {
MutexLocker ml(DumpRegion_lock, Mutex::_no_safepoint_check_flag);
// To get deterministic output from -Xshare:dump, we ensure that Symbols are allocated in
// increasing addresses. When the symbols are copied into the archive, we preserve their
// relative address order (sorted, see ArchiveBuilder::gather_klasses_and_symbols).
//
// We cannot use arena because arena chunks are allocated by the OS. As a result, for example,
// the archived symbol of "java/lang/Object" may sometimes be lower than "java/lang/String", and
// sometimes be higher. This would cause non-deterministic contents in the archive.
DEBUG_ONLY(static void* last = 0);
void* p = (void*)MetaspaceShared::symbol_space_alloc(size(len)*wordSize);
assert(p > last, "must increase monotonically");
DEBUG_ONLY(last = p);
return p;
}
#endif
int alloc_size = size(len)*wordSize;
address res = (address) AllocateHeap(alloc_size, mtSymbol);
return res;
}
void* Symbol::operator new(size_t sz, int len, Arena* arena) throw() {
int alloc_size = size(len)*wordSize;
address res = (address)arena->AmallocWords(alloc_size);
return res;
}
void Symbol::operator delete(void *p) {
assert(((Symbol*)p)->refcount() == 0, "should not call this");
FreeHeap(p);
}
#if INCLUDE_CDS
void Symbol::update_identity_hash() {
// This is called at a safepoint during dumping of a static CDS archive. The caller should have
// called os::init_random() with a deterministic seed and then iterate all archived Symbols in
// a deterministic order.
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
_hash_and_refcount = pack_hash_and_refcount((short)os::random(), PERM_REFCOUNT);
}
void Symbol::set_permanent() {
// This is called at a safepoint during dumping of a dynamic CDS archive.
assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
_hash_and_refcount = pack_hash_and_refcount(extract_hash(_hash_and_refcount), PERM_REFCOUNT);
}
#endif
// ------------------------------------------------------------------
// Symbol::index_of
//
// Test if we have the give substring at or after the i-th char of this
// symbol's utf8 bytes.
// Return -1 on failure. Otherwise return the first index where substr occurs.
int Symbol::index_of_at(int i, const char* substr, int substr_len) const {
assert(i >= 0 && i <= utf8_length(), "oob");
if (substr_len <= 0) return 0;
char first_char = substr[0];
address bytes = (address) ((Symbol*)this)->base();
address limit = bytes + utf8_length() - substr_len; // inclusive limit
address scan = bytes + i;
if (scan > limit)
return -1;
for (; scan <= limit; scan++) {
scan = (address) memchr(scan, first_char, (limit + 1 - scan));
if (scan == NULL)
return -1; // not found
assert(scan >= bytes+i && scan <= limit, "scan oob");
if (substr_len <= 2
? (char) scan[substr_len-1] == substr[substr_len-1]
: memcmp(scan+1, substr+1, substr_len-1) == 0) {
return (int)(scan - bytes);
}
}
return -1;
}
bool Symbol::is_star_match(const char* pattern) const {
if (strchr(pattern, '*') == NULL) {
return equals(pattern);
} else {
ResourceMark rm;
char* buf = as_C_string();
return StringUtils::is_star_match(pattern, buf);
}
}
char* Symbol::as_C_string(char* buf, int size) const {
if (size > 0) {
int len = MIN2(size - 1, utf8_length());
for (int i = 0; i < len; i++) {
buf[i] = char_at(i);
}
buf[len] = '\0';
}
return buf;
}
char* Symbol::as_C_string() const {
int len = utf8_length();
char* str = NEW_RESOURCE_ARRAY(char, len + 1);
return as_C_string(str, len + 1);
}
void Symbol::print_utf8_on(outputStream* st) const {
st->print("%s", as_C_string());
}
void Symbol::print_symbol_on(outputStream* st) const {
char *s;
st = st ? st : tty;
{
// ResourceMark may not affect st->print(). If st is a string
// stream it could resize, using the same resource arena.
ResourceMark rm;
s = as_quoted_ascii();
s = os::strdup(s);
}
if (s == NULL) {
st->print("(null)");
} else {
st->print("%s", s);
os::free(s);
}
}
char* Symbol::as_quoted_ascii() const {
const char *ptr = (const char *)&_body[0];
int quoted_length = UTF8::quoted_ascii_length(ptr, utf8_length());
char* result = NEW_RESOURCE_ARRAY(char, quoted_length + 1);
UTF8::as_quoted_ascii(ptr, utf8_length(), result, quoted_length + 1);
return result;
}
jchar* Symbol::as_unicode(int& length) const {
Symbol* this_ptr = (Symbol*)this;
length = UTF8::unicode_length((char*)this_ptr->bytes(), utf8_length());
jchar* result = NEW_RESOURCE_ARRAY(jchar, length);
if (length > 0) {
UTF8::convert_to_unicode((char*)this_ptr->bytes(), result, length);
}
return result;
}
const char* Symbol::as_klass_external_name(char* buf, int size) const {
if (size > 0) {
char* str = as_C_string(buf, size);
int length = (int)strlen(str);
// Turn all '/'s into '.'s (also for array klasses)
for (int index = 0; index < length; index++) {
if (str[index] == JVM_SIGNATURE_SLASH) {
str[index] = JVM_SIGNATURE_DOT;
}
}
return str;
} else {
return buf;
}
}
const char* Symbol::as_klass_external_name() const {
char* str = as_C_string();
int length = (int)strlen(str);
// Turn all '/'s into '.'s (also for array klasses)
for (int index = 0; index < length; index++) {
if (str[index] == JVM_SIGNATURE_SLASH) {
str[index] = JVM_SIGNATURE_DOT;
}
}
return str;
}
static void print_class(outputStream *os, const SignatureStream& ss) {
int sb = ss.raw_symbol_begin(), se = ss.raw_symbol_end();
for (int i = sb; i < se; ++i) {
int ch = ss.raw_char_at(i);
if (ch == JVM_SIGNATURE_SLASH) {
os->put(JVM_SIGNATURE_DOT);
} else {
os->put(ch);
}
}
}
static void print_array(outputStream *os, SignatureStream& ss) {
int dimensions = ss.skip_array_prefix();
assert(dimensions > 0, "");
if (ss.is_reference()) {
print_class(os, ss);
} else {
os->print("%s", type2name(ss.type()));
}
for (int i = 0; i < dimensions; ++i) {
os->print("[]");
}
}
void Symbol::print_as_signature_external_return_type(outputStream *os) {
for (SignatureStream ss(this); !ss.is_done(); ss.next()) {
if (ss.at_return_type()) {
if (ss.is_array()) {
print_array(os, ss);
} else if (ss.is_reference()) {
print_class(os, ss);
} else {
os->print("%s", type2name(ss.type()));
}
}
}
}
void Symbol::print_as_signature_external_parameters(outputStream *os) {
bool first = true;
for (SignatureStream ss(this); !ss.is_done(); ss.next()) {
if (ss.at_return_type()) break;
if (!first) { os->print(", "); }
if (ss.is_array()) {
print_array(os, ss);
} else if (ss.is_reference()) {
print_class(os, ss);
} else {
os->print("%s", type2name(ss.type()));
}
first = false;
}
}
// Increment refcount while checking for zero. If the Symbol's refcount becomes zero
// a thread could be concurrently removing the Symbol. This is used during SymbolTable
// lookup to avoid reviving a dead Symbol.
bool Symbol::try_increment_refcount() {
uint32_t found = _hash_and_refcount;
while (true) {
uint32_t old_value = found;
int refc = extract_refcount(old_value);
if (refc == PERM_REFCOUNT) {
return true; // sticky max or created permanent
} else if (refc == 0) {
return false; // dead, can't revive.
} else {
found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value + 1);
if (found == old_value) {
return true; // successfully updated.
}
// refcount changed, try again.
}
}
}
// The increment_refcount() is called when not doing lookup. It is assumed that you
// have a symbol with a non-zero refcount and it can't become zero while referenced by
// this caller.
void Symbol::increment_refcount() {
if (!try_increment_refcount()) {
#ifdef ASSERT
print();
fatal("refcount has gone to zero");
#endif
}
#ifndef PRODUCT
if (refcount() != PERM_REFCOUNT) { // not a permanent symbol
NOT_PRODUCT(Atomic::inc(&_total_count);)
}
#endif
}
// Decrement refcount potentially while racing increment, so we need
// to check the value after attempting to decrement so that if another
// thread increments to PERM_REFCOUNT the value is not decremented.
void Symbol::decrement_refcount() {
uint32_t found = _hash_and_refcount;
while (true) {
uint32_t old_value = found;
int refc = extract_refcount(old_value);
if (refc == PERM_REFCOUNT) {
return; // refcount is permanent, permanent is sticky
} else if (refc == 0) {
#ifdef ASSERT
print();
fatal("refcount underflow");
#endif
return;
} else {
found = Atomic::cmpxchg(&_hash_and_refcount, old_value, old_value - 1);
if (found == old_value) {
return; // successfully updated.
}
// refcount changed, try again.
}
}
}
void Symbol::make_permanent() {
uint32_t found = _hash_and_refcount;
while (true) {
uint32_t old_value = found;
int refc = extract_refcount(old_value);
if (refc == PERM_REFCOUNT) {
return; // refcount is permanent, permanent is sticky
} else if (refc == 0) {
#ifdef ASSERT
print();
fatal("refcount underflow");
#endif
return;
} else {
int hash = extract_hash(old_value);
found = Atomic::cmpxchg(&_hash_and_refcount, old_value, pack_hash_and_refcount(hash, PERM_REFCOUNT));
if (found == old_value) {
return; // successfully updated.
}
// refcount changed, try again.
}
}
}
void Symbol::metaspace_pointers_do(MetaspaceClosure* it) {
if (log_is_enabled(Trace, cds)) {
LogStream trace_stream(Log(cds)::trace());
trace_stream.print("Iter(Symbol): %p ", this);
print_value_on(&trace_stream);
trace_stream.cr();
}
}
void Symbol::print_on(outputStream* st) const {
st->print("Symbol: '");
print_symbol_on(st);
st->print("'");
st->print(" count %d", refcount());
}
void Symbol::print() const { print_on(tty); }
// The print_value functions are present in all builds, to support the
// disassembler and error reporting.
void Symbol::print_value_on(outputStream* st) const {
st->print("'");
for (int i = 0; i < utf8_length(); i++) {
st->print("%c", char_at(i));
}
st->print("'");
}
void Symbol::print_value() const { print_value_on(tty); }
bool Symbol::is_valid(Symbol* s) {
if (!is_aligned(s, sizeof(MetaWord))) return false;
if ((size_t)s < os::min_page_size()) return false;
if (!os::is_readable_range(s, s + 1)) return false;
// Symbols are not allocated in Java heap.
if (Universe::heap()->is_in(s)) return false;
int len = s->utf8_length();
if (len < 0) return false;
jbyte* bytes = (jbyte*) s->bytes();
return os::is_readable_range(bytes, bytes + len);
}
// SymbolTable prints this in its statistics
NOT_PRODUCT(size_t Symbol::_total_count = 0;)
#ifndef PRODUCT
bool Symbol::is_valid_id(vmSymbolID vm_symbol_id) {
return vmSymbols::is_valid_id(vm_symbol_id);
}
#endif
¤ Dauer der Verarbeitung: 0.25 Sekunden
(vorverarbeitet)
¤
|
Haftungshinweis
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.
|
