1 /*

     2  * Copyright 1997-2005 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  *

    23  */

    24 

    25 // A symbolOop is a canonicalized string.

    26 // All symbolOops reside in global symbolTable.

    27 // See oopFactory::new_symbol for how to allocate a symbolOop

    28 

    29 class symbolOopDesc : public oopDesc {

    30   friend class VMStructs;

    31  private:

    32   unsigned short _length; // number of UTF8 characters in the symbol

    33   jbyte _body[1];

    34 

    35   enum {

    36     // max_symbol_length is constrained by type of _length

    37     max_symbol_length = (1 << 16) -1

    38   };

    39  public:

    40 

    41   // Low-level access (used with care, since not GC-safe)

    42   jbyte* base() { return &_body[0]; }

    43 

    44 

    45   // Returns the largest size symbol we can safely hold.

    46   static int max_length() {

    47     return max_symbol_length;

    48   }

    49 

    50   static int object_size(int length) {

    51     int size = header_size() + (sizeof(unsigned short) + length + HeapWordSize - 1) / HeapWordSize;

    52     return align_object_size(size);

    53   }

    54 

    55   int object_size() { return object_size(utf8_length()); }

    56 

    57   int byte_at(int index) const {

    58     assert(index >=0 && index < _length, "symbol index overflow");

    59     return ((symbolOopDesc*)this)->base()[index];

    60   }

    61 

    62   void byte_at_put(int index, int value) {

    63     assert(index >=0 && index < _length, "symbol index overflow");

    64     ((symbolOopDesc*)this)->base()[index] = value;

    65   }

    66 

    67   jbyte* bytes() { return base(); }

    68 

    69   int utf8_length() const { return _length; }

    70 

    71   void set_utf8_length(int len) { _length = len; }

    72 

    73   // Compares the symbol with a string

    74   bool equals(const char* str, int len) const;

    75 

    76   // Three-way compare for sorting; returns -1/0/1 if receiver is </==/> than arg

    77   // note that the ordering is not alfabetical

    78   inline int fast_compare(symbolOop other) const;

    79 

    80   // Returns receiver converted to null-terminated UTF-8 string; string is

    81   // allocated in resource area, or in the char buffer provided by caller.

    82   char* as_C_string() const;

    83   char* as_C_string(char* buf, int size) const;

    84   // Use buf if needed buffer length is <= size.

    85   char* as_C_string_flexible_buffer(Thread* t, char* buf, int size) const;

    86 

    87 

    88   // Returns a null terminated utf8 string in a resource array

    89   char* as_utf8() const { return as_C_string(); }

    90   char* as_utf8_flexible_buffer(Thread* t, char* buf, int size) const {

    91     return as_C_string_flexible_buffer(t, buf, size);

    92   }

    93 

    94   jchar* as_unicode(int& length) const;

    95 

    96   // Treating this symbol as a class name, returns the Java name for the class.

    97   // String is allocated in resource area if buffer is not provided.

    98   // See Klass::external_name()

    99   const char* as_klass_external_name() const;

   100   const char* as_klass_external_name(char* buf, int size) const;

   101 

   102   bool object_is_parsable() const {

   103     return (utf8_length() > 0 || (oop)this == Universe::emptySymbol());

   104   }

   105 

   106   // Printing

   107   void print_symbol_on(outputStream* st = NULL);

   108 };

   109 

   110 

   111 // Note: this comparison is used for vtable sorting only; it doesn't matter

   112 // what order it defines, as long as it is a total, time-invariant order

   113 // Since symbolOops are in permSpace, their relative order in memory never changes,

   114 // so use address comparison for speed

   115 int symbolOopDesc::fast_compare(symbolOop other) const {

   116  return (((uintptr_t)this < (uintptr_t)other) ? -1

   117    : ((uintptr_t)this == (uintptr_t) other) ? 0 : 1);

   118 }