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Java example source code file (symbol.cpp)

This example Java source code file (symbol.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

allocateheap, althashing\:\:murmur3_32, min2, new_resource_array, not_product, null, resourcemark, symbol::operator, symbol\*, symbol\:\:as_c_string, symbol\:\:as_klass_external_name, symbol\:\:new_hash, traps, utf8\:\:quoted_ascii_length

The symbol.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, 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 "classfile/altHashing.hpp"
#include "classfile/classLoaderData.hpp"
#include "oops/symbol.hpp"
#include "runtime/atomic.inline.hpp"
#include "runtime/os.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"

Symbol::Symbol(const u1* name, int length, int refcount) {
  _refcount = refcount;
  _length = length;
  _identity_hash = os::random();
  for (int i = 0; i < _length; i++) {
    byte_at_put(i, name[i]);
  }
}

void* Symbol::operator new(size_t sz, int len, TRAPS) throw() {
  int alloc_size = size(len)*HeapWordSize;
  address res = (address) AllocateHeap(alloc_size, mtSymbol);
  return res;
}

void* Symbol::operator new(size_t sz, int len, Arena* arena, TRAPS) throw() {
  int alloc_size = size(len)*HeapWordSize;
  address res = (address)arena->Amalloc(alloc_size);
  return res;
}

void* Symbol::operator new(size_t sz, int len, ClassLoaderData* loader_data, TRAPS) throw() {
  address res;
  int alloc_size = size(len)*HeapWordSize;
  res = (address) Metaspace::allocate(loader_data, size(len), true,
                                      MetaspaceObj::SymbolType, CHECK_NULL);
  return res;
}

void Symbol::operator delete(void *p) {
  assert(((Symbol*)p)->refcount() == 0, "should not call this");
  FreeHeap(p);
}

// ------------------------------------------------------------------
// Symbol::equals
//
// Compares the symbol with a string of the given length.
bool Symbol::equals(const char* str, int len) const {
  int l = utf8_length();
  if (l != len) return false;
  while (l-- > 0) {
    if (str[l] != (char) byte_at(l))
      return false;
  }
  assert(l == -1, "we should be at the beginning");
  return true;
}


// ------------------------------------------------------------------
// Symbol::starts_with
//
// Tests if the symbol starts with the specified prefix of the given
// length.
bool Symbol::starts_with(const char* prefix, int len) const {
  if (len > utf8_length()) return false;
  while (len-- > 0) {
    if (prefix[len] != (char) byte_at(len))
      return false;
  }
  assert(len == -1, "we should be at the beginning");
  return true;
}


// ------------------------------------------------------------------
// Symbol::index_of
//
// Finds if the given string is a substring of this symbol's utf8 bytes.
// Return -1 on failure.  Otherwise return the first index where str occurs.
int Symbol::index_of_at(int i, const char* str, int len) const {
  assert(i >= 0 && i <= utf8_length(), "oob");
  if (len <= 0)  return 0;
  char first_char = str[0];
  address bytes = (address) ((Symbol*)this)->base();
  address limit = bytes + utf8_length() - 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 (memcmp(scan, str, len) == 0)
      return (int)(scan - bytes);
  }
  return -1;
}


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] = byte_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);
}

char* Symbol::as_C_string_flexible_buffer(Thread* t,
                                                 char* buf, int size) const {
  char* str;
  int len = utf8_length();
  int buf_len = len + 1;
  if (size < buf_len) {
    str = NEW_RESOURCE_ARRAY(char, buf_len);
  } else {
    str = buf;
  }
  return as_C_string(str, buf_len);
}

void Symbol::print_symbol_on(outputStream* st) const {
  ResourceMark rm;
  st = st ? st : tty;
  st->print("%s", as_quoted_ascii());
}

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] == '/') {
        str[index] = '.';
      }
    }
    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] == '/') {
      str[index] = '.';
    }
  }
  return str;
}

// Alternate hashing for unbalanced symbol tables.
unsigned int Symbol::new_hash(jint seed) {
  ResourceMark rm;
  // Use alternate hashing algorithm on this symbol.
  return AltHashing::murmur3_32(seed, (const jbyte*)as_C_string(), utf8_length());
}

void Symbol::increment_refcount() {
  // Only increment the refcount if positive.  If negative either
  // overflow has occurred or it is a permanent symbol in a read only
  // shared archive.
  if (_refcount >= 0) {
    Atomic::inc(&_refcount);
    NOT_PRODUCT(Atomic::inc(&_total_count);)
  }
}

void Symbol::decrement_refcount() {
  if (_refcount >= 0) {
    Atomic::dec(&_refcount);
#ifdef ASSERT
    if (_refcount < 0) {
      print();
      assert(false, "reference count underflow for symbol");
    }
#endif
  }
}

void Symbol::print_on(outputStream* st) const {
  if (this == NULL) {
    st->print_cr("NULL");
  } else {
    st->print("Symbol: '");
    print_symbol_on(st);
    st->print("'");
    st->print(" count %d", refcount());
  }
}

// The print_value functions are present in all builds, to support the
// disassembler and error reporting.
void Symbol::print_value_on(outputStream* st) const {
  if (this == NULL) {
    st->print("NULL");
  } else {
    st->print("'");
    for (int i = 0; i < utf8_length(); i++) {
      st->print("%c", byte_at(i));
    }
    st->print("'");
  }
}

// SymbolTable prints this in its statistics
NOT_PRODUCT(int Symbol::_total_count = 0;)

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