1 /* 2 * Copyright (c) 1997, 2010, 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 #ifndef SHARE_VM_CODE_COMPRESSEDSTREAM_HPP 26 #define SHARE_VM_CODE_COMPRESSEDSTREAM_HPP 27 28 #include "memory/allocation.hpp" 29 30 // Simple interface for filing out and filing in basic types 31 // Used for writing out and reading in debugging information. 32 33 class CompressedStream : public ResourceObj { 34 friend class VMStructs; 35 protected: 36 u_char* _buffer; 37 int _position; 38 39 enum { 40 // Constants for UNSIGNED5 coding of Pack200 41 lg_H = 6, H = 1<<lg_H, // number of high codes (64) 42 L = (1<<BitsPerByte)-H, // number of low codes (192) 43 MAX_i = 4 // bytes are numbered in (0..4), max 5 bytes 44 }; 45 46 // these inlines are defined only in compressedStream.cpp 47 static inline juint encode_sign(jint value); // for Pack200 SIGNED5 48 static inline jint decode_sign(juint value); // for Pack200 SIGNED5 49 static inline juint reverse_int(juint bits); // to trim trailing float 0's 50 51 public: CompressedStream(u_char * buffer,int position=0)52 CompressedStream(u_char* buffer, int position = 0) { 53 _buffer = buffer; 54 _position = position; 55 } 56 buffer() const57 u_char* buffer() const { return _buffer; } 58 59 // Positioning position() const60 int position() const { return _position; } set_position(int position)61 void set_position(int position) { _position = position; } 62 }; 63 64 65 class CompressedReadStream : public CompressedStream { 66 private: read()67 inline u_char read() { return _buffer[_position++]; } 68 69 // This encoding, called UNSIGNED5, is taken from J2SE Pack200. 70 // It assumes that most values have lots of leading zeroes. 71 // Very small values, in the range [0..191], code in one byte. 72 // Any 32-bit value (including negatives) can be coded, in 73 // up to five bytes. The grammar is: 74 // low_byte = [0..191] 75 // high_byte = [192..255] 76 // any_byte = low_byte | high_byte 77 // coding = low_byte 78 // | high_byte low_byte 79 // | high_byte high_byte low_byte 80 // | high_byte high_byte high_byte low_byte 81 // | high_byte high_byte high_byte high_byte any_byte 82 // Each high_byte contributes six bits of payload. 83 // The encoding is one-to-one (except for integer overflow) 84 // and easy to parse and unparse. 85 read_int_mb(jint b0)86 jint read_int_mb(jint b0) { 87 int pos = position() - 1; 88 u_char* buf = buffer() + pos; 89 assert(buf[0] == b0 && b0 >= L, "correctly called"); 90 jint sum = b0; 91 // must collect more bytes: b[1]...b[4] 92 int lg_H_i = lg_H; 93 for (int i = 0; ; ) { 94 jint b_i = buf[++i]; // b_i = read(); ++i; 95 sum += b_i << lg_H_i; // sum += b[i]*(64**i) 96 if (b_i < L || i == MAX_i) { 97 set_position(pos+i+1); 98 return sum; 99 } 100 lg_H_i += lg_H; 101 } 102 } 103 104 public: CompressedReadStream(u_char * buffer,int position=0)105 CompressedReadStream(u_char* buffer, int position = 0) 106 : CompressedStream(buffer, position) {} 107 read_bool()108 jboolean read_bool() { return (jboolean) read(); } read_byte()109 jbyte read_byte() { return (jbyte ) read(); } read_char()110 jchar read_char() { return (jchar ) read_int(); } read_short()111 jshort read_short() { return (jshort ) read_signed_int(); } read_int()112 jint read_int() { jint b0 = read(); 113 if (b0 < L) return b0; 114 else return read_int_mb(b0); 115 } 116 jint read_signed_int(); 117 jfloat read_float(); // jfloat_cast(reverse_int(read_int())) 118 jdouble read_double(); // jdouble_cast(2*reverse_int(read_int)) 119 jlong read_long(); // jlong_from(2*read_signed_int()) 120 }; 121 122 123 class CompressedWriteStream : public CompressedStream { 124 private: full()125 bool full() { 126 return _position >= _size; 127 } store(u_char b)128 void store(u_char b) { 129 _buffer[_position++] = b; 130 } write(u_char b)131 void write(u_char b) { 132 if (full()) grow(); 133 store(b); 134 } 135 void grow(); 136 137 void write_int_mb(jint value); // UNSIGNED5 coding, 1-5 byte cases 138 139 protected: 140 int _size; 141 142 public: 143 CompressedWriteStream(int initial_size); CompressedWriteStream(u_char * buffer,int initial_size,int position=0)144 CompressedWriteStream(u_char* buffer, int initial_size, int position = 0) 145 : CompressedStream(buffer, position) { _size = initial_size; } 146 write_bool(jboolean value)147 void write_bool(jboolean value) { write(value); } write_byte(jbyte value)148 void write_byte(jbyte value) { write(value); } write_char(jchar value)149 void write_char(jchar value) { write_int(value); } write_short(jshort value)150 void write_short(jshort value) { write_signed_int(value); } write_int(jint value)151 void write_int(jint value) { if ((juint)value < L && !full()) 152 store((u_char)value); 153 else write_int_mb(value); } 154 void write_signed_int(jint value); // write_int(encode_sign(value)) 155 void write_float(jfloat value); // write_int(reverse_int(jint_cast(v))) 156 void write_double(jdouble value); // write_int(reverse_int(<low,high>)) 157 void write_long(jlong value); // write_signed_int(<low,high>) 158 }; 159 160 #endif // SHARE_VM_CODE_COMPRESSEDSTREAM_HPP 161