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1 /*
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2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 #include "incls/_precompiled.incl"
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26 #include "incls/_compressedStream.cpp.incl"
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27
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28 // 32-bit one-to-one sign encoding taken from Pack200
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29 // converts leading sign bits into leading zeroes with trailing sign bit
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30 inline juint CompressedStream::encode_sign(jint value) {
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31 return (value << 1) ^ (value >> 31);
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32 }
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33 inline jint CompressedStream::decode_sign(juint value) {
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34 return (value >> 1) ^ -(jint)(value & 1);
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35 }
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36
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37 // 32-bit self-inverse encoding of float bits
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38 // converts trailing zeroes (common in floats) to leading zeroes
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39 inline juint CompressedStream::reverse_int(juint i) {
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40 // Hacker's Delight, Figure 7-1
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41 i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555;
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42 i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333;
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43 i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f;
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44 i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24);
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45 return i;
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46 }
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47
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48
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49 jint CompressedReadStream::read_signed_int() {
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50 return decode_sign(read_int());
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51 }
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52
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53 // Compressing floats is simple, because the only common pattern
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54 // is trailing zeroes. (Compare leading sign bits on ints.)
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55 // Since floats are left-justified, as opposed to right-justified
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56 // ints, we can bit-reverse them in order to take advantage of int
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57 // compression.
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58
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59 jfloat CompressedReadStream::read_float() {
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60 int rf = read_int();
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61 int f = reverse_int(rf);
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62 return jfloat_cast(f);
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63 }
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64
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65 jdouble CompressedReadStream::read_double() {
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66 jint rh = read_int();
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67 jint rl = read_int();
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68 jint h = reverse_int(rh);
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69 jint l = reverse_int(rl);
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70 return jdouble_cast(jlong_from(h, l));
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71 }
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72
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73 jlong CompressedReadStream::read_long() {
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74 jint low = read_signed_int();
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75 jint high = read_signed_int();
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76 return jlong_from(high, low);
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77 }
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78
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79 CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) {
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80 _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size);
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81 _size = initial_size;
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82 _position = 0;
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83 }
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84
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85 void CompressedWriteStream::grow() {
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86 u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2);
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87 memcpy(_new_buffer, _buffer, _position);
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88 _buffer = _new_buffer;
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89 _size = _size * 2;
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90 }
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91
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92 void CompressedWriteStream::write_signed_int(jint value) {
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93 // this encoding, called SIGNED5, is taken from Pack200
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94 write_int(encode_sign(value));
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95 }
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96
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97 void CompressedWriteStream::write_float(jfloat value) {
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98 juint f = jint_cast(value);
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99 juint rf = reverse_int(f);
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100 assert(f == reverse_int(rf), "can re-read same bits");
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101 write_int(rf);
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102 }
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103
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104 void CompressedWriteStream::write_double(jdouble value) {
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105 juint h = high(jlong_cast(value));
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106 juint l = low( jlong_cast(value));
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107 juint rh = reverse_int(h);
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108 juint rl = reverse_int(l);
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109 assert(h == reverse_int(rh), "can re-read same bits");
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110 assert(l == reverse_int(rl), "can re-read same bits");
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111 write_int(rh);
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112 write_int(rl);
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113 }
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114
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115 void CompressedWriteStream::write_long(jlong value) {
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116 write_signed_int(low(value));
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117 write_signed_int(high(value));
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118 }
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119
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120
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121 /// The remaining details
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122
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123 #ifndef PRODUCT
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124 // set this to trigger unit test
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125 void test_compressed_stream(int trace);
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126 bool test_compressed_stream_enabled = false;
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127 #endif
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128
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129 // This encoding, called UNSIGNED5, is taken from J2SE Pack200.
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130 // It assumes that most values have lots of leading zeroes.
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131 // Very small values, in the range [0..191], code in one byte.
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132 // Any 32-bit value (including negatives) can be coded, in
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133 // up to five bytes. The grammar is:
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134 // low_byte = [0..191]
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135 // high_byte = [192..255]
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136 // any_byte = low_byte | high_byte
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137 // coding = low_byte
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138 // | high_byte low_byte
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139 // | high_byte high_byte low_byte
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140 // | high_byte high_byte high_byte low_byte
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141 // | high_byte high_byte high_byte high_byte any_byte
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142 // Each high_byte contributes six bits of payload.
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143 // The encoding is one-to-one (except for integer overflow)
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144 // and easy to parse and unparse.
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145
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146 jint CompressedReadStream::read_int_mb(jint b0) {
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147 int pos = position() - 1;
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148 u_char* buf = buffer() + pos;
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149 assert(buf[0] == b0 && b0 >= L, "correctly called");
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150 jint sum = b0;
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151 // must collect more bytes: b[1]...b[4]
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152 int lg_H_i = lg_H;
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153 for (int i = 0; ; ) {
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154 jint b_i = buf[++i]; // b_i = read(); ++i;
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155 sum += b_i << lg_H_i; // sum += b[i]*(64**i)
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156 if (b_i < L || i == MAX_i) {
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157 set_position(pos+i+1);
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158 return sum;
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159 }
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160 lg_H_i += lg_H;
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161 }
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162 }
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163
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164 void CompressedWriteStream::write_int_mb(jint value) {
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165 debug_only(int pos1 = position());
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166 juint sum = value;
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167 for (int i = 0; ; ) {
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168 if (sum < L || i == MAX_i) {
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169 // remainder is either a "low code" or the 5th byte
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170 assert(sum == (u_char)sum, "valid byte");
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171 write((u_char)sum);
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172 break;
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173 }
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174 sum -= L;
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175 int b_i = L + (sum % H); // this is a "high code"
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176 sum >>= lg_H; // extracted 6 bits
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177 write(b_i); ++i;
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178 }
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179
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180 #ifndef PRODUCT
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181 if (test_compressed_stream_enabled) { // hack to enable this stress test
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182 test_compressed_stream_enabled = false;
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183 test_compressed_stream(0);
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184 }
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185 #endif
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186 }
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187
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188
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189 #ifndef PRODUCT
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190 /// a unit test (can be run by hand from a debugger)
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191
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192 // Avoid a VS2005 compiler stack overflow w/ fastdebug build.
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193 // The following pragma optimize turns off optimization ONLY
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194 // for this block (a matching directive turns it back on later).
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195 // These directives can be removed once the MS VS.NET 2005
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196 // compiler stack overflow is fixed.
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197 #if _MSC_VER >=1400 && !defined(_WIN64)
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198 #pragma optimize("", off)
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199 #endif
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200
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201 // generator for an "interesting" set of critical values
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202 enum { stretch_limit = (1<<16) * (64-16+1) };
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203 static jlong stretch(jint x, int bits) {
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204 // put x[high 4] into place
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205 jlong h = (jlong)((x >> (16-4))) << (bits - 4);
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206 // put x[low 12] into place, sign extended
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207 jlong l = ((jlong)x << (64-12)) >> (64-12);
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208 // move l upwards, maybe
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209 l <<= (x >> 16);
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210 return h ^ l;
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211 }
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212
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213 void test_compressed_stream(int trace) {
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214 CompressedWriteStream bytes(stretch_limit * 100);
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215 jint n;
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216 int step = 0, fails = 0;
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217 #define CHECKXY(x, y, fmt) { \
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218 ++step; \
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219 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \
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220 if (trace > 0 && (step % trace) == 0) { \
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221 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \
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222 step, n, x, xlen); } \
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223 if (x != y) { \
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224 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \
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225 fails++; \
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226 } }
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227 for (n = 0; n < (1<<8); n++) {
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228 jbyte x = (jbyte)n;
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229 bytes.write_byte(x); ++step;
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230 }
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231 for (n = 0; n < stretch_limit; n++) {
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232 jint x = (jint)stretch(n, 32);
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233 bytes.write_int(x); ++step;
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234 bytes.write_signed_int(x); ++step;
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235 bytes.write_float(jfloat_cast(x)); ++step;
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236 }
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237 for (n = 0; n < stretch_limit; n++) {
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238 jlong x = stretch(n, 64);
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239 bytes.write_long(x); ++step;
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240 bytes.write_double(jdouble_cast(x)); ++step;
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241 }
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242 int length = bytes.position();
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243 if (trace != 0)
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244 tty->print_cr("set up test of %d stream values, size %d", step, length);
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245 step = 0;
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246 // now decode it all
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247 CompressedReadStream decode(bytes.buffer());
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248 int pos, lastpos = decode.position();
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249 for (n = 0; n < (1<<8); n++) {
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250 jbyte x = (jbyte)n;
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251 jbyte y = decode.read_byte();
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252 CHECKXY(x, y, "%db");
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253 }
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254 for (n = 0; n < stretch_limit; n++) {
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255 jint x = (jint)stretch(n, 32);
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256 jint y1 = decode.read_int();
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257 CHECKXY(x, y1, "%du");
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258 jint y2 = decode.read_signed_int();
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259 CHECKXY(x, y2, "%di");
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260 jint y3 = jint_cast(decode.read_float());
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261 CHECKXY(x, y3, "%df");
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262 }
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263 for (n = 0; n < stretch_limit; n++) {
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264 jlong x = stretch(n, 64);
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265 jlong y1 = decode.read_long();
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266 CHECKXY(x, y1, INT64_FORMAT "l");
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267 jlong y2 = jlong_cast(decode.read_double());
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268 CHECKXY(x, y2, INT64_FORMAT "d");
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269 }
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270 int length2 = decode.position();
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271 if (trace != 0)
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272 tty->print_cr("finished test of %d stream values, size %d", step, length2);
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273 guarantee(length == length2, "bad length");
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274 guarantee(fails == 0, "test failures");
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275 }
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276
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277 #if _MSC_VER >=1400 && !defined(_WIN64)
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278 #pragma optimize("", on)
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279 #endif
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280
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281 #endif // PRODUCT
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