/*

 * Copyright (c) 1997, 2018, 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 "logging/log.hpp"

#include "logging/logStream.hpp"

#include "memory/allocation.inline.hpp"

#include "memory/resourceArea.hpp"

#include "oops/symbol.hpp"

#include "runtime/atomic.hpp"

#include "runtime/os.hpp"

uint32_t Symbol::pack_length_and_refcount(int length, int refcount) {

  STATIC_ASSERT(max_symbol_length == ((1 << 16) - 1));

  STATIC_ASSERT(PERM_REFCOUNT == ((1 << 16) - 1));

  assert(length >= 0, "negative length");

  assert(length <= max_symbol_length, "too long symbol");

  assert(refcount >= 0, "negative refcount");

  assert(refcount <= PERM_REFCOUNT, "invalid refcount");

  uint32_t hi = length;

  uint32_t lo = refcount;

  return (hi << 16) | lo;

}

Symbol::Symbol(const u1* name, int length, int refcount) {

  _length_and_refcount =  pack_length_and_refcount(length, refcount);

  _identity_hash = (short)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)*wordSize;

  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)*wordSize;

  address res = (address)arena->Amalloc_4(alloc_size);

  return res;

}

void Symbol::operator delete(void *p) {

  assert(((Symbol*)p)->refcount() == 0, "should not call this");

  FreeHeap(p);

}

// ------------------------------------------------------------------

// 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_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] = 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);

}

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_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] == '/') {

        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(juint seed) {

  ResourceMark rm;

  // Use alternate hashing algorithm on this symbol.

  return AltHashing::murmur3_32(seed, (const jbyte*)as_C_string(), utf8_length());

}

// 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 = _length_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(old_value + 1, &_length_and_refcount, old_value);

      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 = _length_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(old_value - 1, &_length_and_refcount, old_value);

      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 {

  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", char_at(i));

    }

    st->print("'");

  }

}

// SymbolTable prints this in its statistics

NOT_PRODUCT(size_t Symbol::_total_count = 0;)