C++ Symbol::byte_at方法代码示例

 virtual void print_method_on(outputStream* st) {
   int limit;
   int i;
   Method* m = method();
   Symbol* k = m->klass_name();
   // Print the class name with dots instead of slashes
   limit = k->utf8_length();
   for (i = 0 ; i < limit ; i += 1) {
     char c = (char) k->byte_at(i);
     if (c == '/') {
       c = '.';
     }
     st->print("%c", c);
   }
   if (limit > 0) {
     st->print(".");
   }
   Symbol* n = m->name();
   limit = n->utf8_length();
   for (i = 0 ; i < limit ; i += 1) {
     char c = (char) n->byte_at(i);
     st->print("%c", c);
   }
   if (Verbose || WizardMode) {
     // Disambiguate overloaded methods
     Symbol* sig = m->signature();
     sig->print_symbol_on(st);
   } else if (MethodHandles::is_signature_polymorphic(m->intrinsic_id()))
     // compare with Method::print_short_name
     MethodHandles::print_as_basic_type_signature_on(st, m->signature(), true);
 }

  void next() {
    Symbol* sig = _signature;
    int len = sig->utf8_length();
    if (_end >= len) {
      _end = len + 1;
      return;
    }

    _begin = _end;
    int t = sig->byte_at(_begin);
    switch (t) {
      case 'B': _type = T_BYTE;    break;
      case 'C': _type = T_CHAR;    break;
      case 'D': _type = T_DOUBLE;  break;
      case 'F': _type = T_FLOAT;   break;
      case 'I': _type = T_INT;     break;
      case 'J': _type = T_LONG;    break;
      case 'S': _type = T_SHORT;   break;
      case 'Z': _type = T_BOOLEAN; break;
      case 'V': _type = T_VOID;    break;
      default : next_non_primitive(t);
                return;
    }
    _end++;
  }

char* NativeLookup::long_jni_name(methodHandle method) {
  // Signature ignore the wrapping parenteses and the trailing return type
  stringStream st;
  Symbol* signature = method->signature();
  st.print("__");
  // find ')'
  int end;
  for (end = 0; end < signature->utf8_length() && signature->byte_at(end) != ')'; end++);
  // skip first '('
  mangle_name_on(&st, signature, 1, end);
  return st.as_string();
}

// Check all the formats of native implementation name to see if there is one
// for the specified method.
address NativeLookup::lookup_critical_entry(methodHandle method) {
  if (!CriticalJNINatives) return NULL;

  if (method->is_synchronized() ||
      !method->is_static()) {
    // Only static non-synchronized methods are allowed
    return NULL;
  }

  ResourceMark rm;
  address entry = NULL;

  Symbol* signature = method->signature();
  for (int end = 0; end < signature->utf8_length(); end++) {
    if (signature->byte_at(end) == 'L') {
      // Don't allow object types
      return NULL;
    }
  }

  // Compute critical name
  char* critical_name = critical_jni_name(method);

  // Compute argument size
  int args_size = 1                             // JNIEnv
                + (method->is_static() ? 1 : 0) // class for static methods
                + method->size_of_parameters(); // actual parameters


  // 1) Try JNI short style
  entry = lookup_critical_style(method, critical_name, "",        args_size, true);
  if (entry != NULL) return entry;

  // Compute long name
  char* long_name = long_jni_name(method);

  // 2) Try JNI long style
  entry = lookup_critical_style(method, critical_name, long_name, args_size, true);
  if (entry != NULL) return entry;

  // 3) Try JNI short style without os prefix/suffix
  entry = lookup_critical_style(method, critical_name, "",        args_size, false);
  if (entry != NULL) return entry;

  // 4) Try JNI long style without os prefix/suffix
  entry = lookup_critical_style(method, critical_name, long_name, args_size, false);

  return entry; // NULL indicates not found
}

// ------------------------------------------------------------------
// ciEnv::get_klass_by_name_impl
ciKlass* ciEnv::get_klass_by_name_impl(ciKlass* accessing_klass,
                                       constantPoolHandle cpool,
                                       ciSymbol* name,
                                       bool require_local) {
  ASSERT_IN_VM;
  EXCEPTION_CONTEXT;

  // Now we need to check the SystemDictionary
  Symbol* sym = name->get_symbol();
  if (sym->byte_at(0) == 'L' &&
    sym->byte_at(sym->utf8_length()-1) == ';') {
    // This is a name from a signature.  Strip off the trimmings.
    // Call recursive to keep scope of strippedsym.
    TempNewSymbol strippedsym = SymbolTable::new_symbol(sym->as_utf8()+1,
                    sym->utf8_length()-2,
                    KILL_COMPILE_ON_FATAL_(_unloaded_ciinstance_klass));
    ciSymbol* strippedname = get_symbol(strippedsym);
    return get_klass_by_name_impl(accessing_klass, cpool, strippedname, require_local);
  }

  // Check for prior unloaded klass.  The SystemDictionary's answers
  // can vary over time but the compiler needs consistency.
  ciKlass* unloaded_klass = check_get_unloaded_klass(accessing_klass, name);
  if (unloaded_klass != NULL) {
    if (require_local)  return NULL;
    return unloaded_klass;
  }

  Handle loader(THREAD, (oop)NULL);
  Handle domain(THREAD, (oop)NULL);
  if (accessing_klass != NULL) {
    loader = Handle(THREAD, accessing_klass->loader());
    domain = Handle(THREAD, accessing_klass->protection_domain());
  }

  // setup up the proper type to return on OOM
  ciKlass* fail_type;
  if (sym->byte_at(0) == '[') {
    fail_type = _unloaded_ciobjarrayklass;
  } else {
    fail_type = _unloaded_ciinstance_klass;
  }
  KlassHandle found_klass;
  {
    ttyUnlocker ttyul;  // release tty lock to avoid ordering problems
    MutexLocker ml(Compile_lock);
    Klass* kls;
    if (!require_local) {
      kls = SystemDictionary::find_constrained_instance_or_array_klass(sym, loader,
                                                                       KILL_COMPILE_ON_FATAL_(fail_type));
    } else {
      kls = SystemDictionary::find_instance_or_array_klass(sym, loader, domain,
                                                           KILL_COMPILE_ON_FATAL_(fail_type));
    }
    found_klass = KlassHandle(THREAD, kls);
  }

  // If we fail to find an array klass, look again for its element type.
  // The element type may be available either locally or via constraints.
  // In either case, if we can find the element type in the system dictionary,
  // we must build an array type around it.  The CI requires array klasses
  // to be loaded if their element klasses are loaded, except when memory
  // is exhausted.
  if (sym->byte_at(0) == '[' &&
      (sym->byte_at(1) == '[' || sym->byte_at(1) == 'L')) {
    // We have an unloaded array.
    // Build it on the fly if the element class exists.
    TempNewSymbol elem_sym = SymbolTable::new_symbol(sym->as_utf8()+1,
                                                 sym->utf8_length()-1,
                                                 KILL_COMPILE_ON_FATAL_(fail_type));

    // Get element ciKlass recursively.
    ciKlass* elem_klass =
      get_klass_by_name_impl(accessing_klass,
                             cpool,
                             get_symbol(elem_sym),
                             require_local);
    if (elem_klass != NULL && elem_klass->is_loaded()) {
      // Now make an array for it
      return ciObjArrayKlass::make_impl(elem_klass);
    }
  }

  if (found_klass() == NULL && !cpool.is_null() && cpool->has_preresolution()) {
    // Look inside the constant pool for pre-resolved class entries.
    for (int i = cpool->length() - 1; i >= 1; i--) {
      if (cpool->tag_at(i).is_klass()) {
        Klass* kls = cpool->resolved_klass_at(i);
        if (kls->name() == sym) {
          found_klass = KlassHandle(THREAD, kls);
          break;
        }
      }
    }
  }

  if (found_klass() != NULL) {
    // Found it.  Build a CI handle.
//.........这里部分代码省略.........