1 /*
   2  * Copyright (c) 1997, 2005, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // Input stream for reading .class file
  26 //
  27 // The entire input stream is present in a buffer allocated by the caller.
  28 // The caller is responsible for deallocating the buffer and for using
  29 // ResourceMarks appropriately when constructing streams.
  30 
  31 class ClassFileStream: public ResourceObj {
  32  private:
  33   u1*   _buffer_start; // Buffer bottom
  34   u1*   _buffer_end;   // Buffer top (one past last element)
  35   u1*   _current;      // Current buffer position
  36   char* _source;       // Source of stream (directory name, ZIP/JAR archive name)
  37   bool  _need_verify;  // True if verification is on for the class file
  38 
  39   void truncated_file_error(TRAPS);
  40  public:
  41   // Constructor
  42   ClassFileStream(u1* buffer, int length, char* source);
  43 
  44   // Buffer access
  45   u1* buffer() const           { return _buffer_start; }
  46   int length() const           { return _buffer_end - _buffer_start; }
  47   u1* current() const          { return _current; }
  48   void set_current(u1* pos)    { _current = pos; }
  49   char* source() const         { return _source; }
  50   void set_verify(bool flag)   { _need_verify = flag; }
  51 
  52   void check_truncated_file(bool b, TRAPS) {
  53     if (b) {
  54       truncated_file_error(THREAD);
  55     }
  56   }
  57 
  58   void guarantee_more(int size, TRAPS) {
  59     size_t remaining = (size_t)(_buffer_end - _current);
  60     unsigned int usize = (unsigned int)size;
  61     check_truncated_file(usize > remaining, CHECK);
  62   }
  63 
  64   // Read u1 from stream
  65   u1 get_u1(TRAPS);
  66   u1 get_u1_fast() {
  67     return *_current++;
  68   }
  69 
  70   // Read u2 from stream
  71   u2 get_u2(TRAPS);
  72   u2 get_u2_fast() {
  73     u2 res = Bytes::get_Java_u2(_current);
  74     _current += 2;
  75     return res;
  76   }
  77 
  78   // Read u4 from stream
  79   u4 get_u4(TRAPS);
  80   u4 get_u4_fast() {
  81     u4 res = Bytes::get_Java_u4(_current);
  82     _current += 4;
  83     return res;
  84   }
  85 
  86   // Read u8 from stream
  87   u8 get_u8(TRAPS);
  88   u8 get_u8_fast() {
  89     u8 res = Bytes::get_Java_u8(_current);
  90     _current += 8;
  91     return res;
  92   }
  93 
  94   // Get direct pointer into stream at current position.
  95   // Returns NULL if length elements are not remaining. The caller is
  96   // responsible for calling skip below if buffer contents is used.
  97   u1* get_u1_buffer() {
  98     return _current;
  99   }
 100 
 101   u2* get_u2_buffer() {
 102     return (u2*) _current;
 103   }
 104 
 105   // Skip length u1 or u2 elements from stream
 106   void skip_u1(int length, TRAPS);
 107   void skip_u1_fast(int length) {
 108     _current += length;
 109   }
 110 
 111   void skip_u2(int length, TRAPS);
 112   void skip_u2_fast(int length) {
 113     _current += 2 * length;
 114   }
 115 
 116   // Tells whether eos is reached
 117   bool at_eos() const          { return _current == _buffer_end; }
 118 };