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1 /* |
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2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
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22 * |
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23 */ |
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24 |
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25 #include "precompiled.hpp" |
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26 #include "code/compressedStream.hpp" |
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27 #include "utilities/ostream.hpp" |
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28 |
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29 // 32-bit one-to-one sign encoding taken from Pack200 |
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30 // converts leading sign bits into leading zeroes with trailing sign bit |
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31 inline juint CompressedStream::encode_sign(jint value) { |
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32 return (value << 1) ^ (value >> 31); |
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33 } |
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34 inline jint CompressedStream::decode_sign(juint value) { |
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35 return (value >> 1) ^ -(jint)(value & 1); |
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36 } |
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37 |
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38 // 32-bit self-inverse encoding of float bits |
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39 // converts trailing zeroes (common in floats) to leading zeroes |
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40 inline juint CompressedStream::reverse_int(juint i) { |
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41 // Hacker's Delight, Figure 7-1 |
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42 i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555; |
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43 i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333; |
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44 i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f; |
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45 i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24); |
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46 return i; |
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47 } |
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48 |
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49 |
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50 jint CompressedReadStream::read_signed_int() { |
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51 return decode_sign(read_int()); |
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52 } |
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53 |
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54 // Compressing floats is simple, because the only common pattern |
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55 // is trailing zeroes. (Compare leading sign bits on ints.) |
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56 // Since floats are left-justified, as opposed to right-justified |
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57 // ints, we can bit-reverse them in order to take advantage of int |
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58 // compression. |
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59 |
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60 jfloat CompressedReadStream::read_float() { |
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61 int rf = read_int(); |
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62 int f = reverse_int(rf); |
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63 return jfloat_cast(f); |
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64 } |
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65 |
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66 jdouble CompressedReadStream::read_double() { |
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67 jint rh = read_int(); |
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68 jint rl = read_int(); |
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69 jint h = reverse_int(rh); |
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70 jint l = reverse_int(rl); |
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71 return jdouble_cast(jlong_from(h, l)); |
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72 } |
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73 |
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74 jlong CompressedReadStream::read_long() { |
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75 jint low = read_signed_int(); |
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76 jint high = read_signed_int(); |
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77 return jlong_from(high, low); |
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78 } |
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79 |
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80 CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) { |
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81 _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size); |
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82 _size = initial_size; |
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83 _position = 0; |
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84 } |
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85 |
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86 void CompressedWriteStream::grow() { |
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87 u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2); |
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88 memcpy(_new_buffer, _buffer, _position); |
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89 _buffer = _new_buffer; |
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90 _size = _size * 2; |
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91 } |
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92 |
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93 void CompressedWriteStream::write_signed_int(jint value) { |
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94 // this encoding, called SIGNED5, is taken from Pack200 |
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95 write_int(encode_sign(value)); |
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96 } |
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97 |
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98 void CompressedWriteStream::write_float(jfloat value) { |
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99 juint f = jint_cast(value); |
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100 juint rf = reverse_int(f); |
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101 assert(f == reverse_int(rf), "can re-read same bits"); |
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102 write_int(rf); |
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103 } |
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104 |
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105 void CompressedWriteStream::write_double(jdouble value) { |
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106 juint h = high(jlong_cast(value)); |
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107 juint l = low( jlong_cast(value)); |
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108 juint rh = reverse_int(h); |
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109 juint rl = reverse_int(l); |
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110 assert(h == reverse_int(rh), "can re-read same bits"); |
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111 assert(l == reverse_int(rl), "can re-read same bits"); |
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112 write_int(rh); |
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113 write_int(rl); |
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114 } |
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115 |
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116 void CompressedWriteStream::write_long(jlong value) { |
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117 write_signed_int(low(value)); |
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118 write_signed_int(high(value)); |
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119 } |
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120 |
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121 |
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122 /// The remaining details |
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123 |
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124 #ifndef PRODUCT |
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125 // set this to trigger unit test |
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126 void test_compressed_stream(int trace); |
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127 bool test_compressed_stream_enabled = false; |
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128 #endif |
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129 |
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130 // This encoding, called UNSIGNED5, is taken from J2SE Pack200. |
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131 // It assumes that most values have lots of leading zeroes. |
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132 // Very small values, in the range [0..191], code in one byte. |
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133 // Any 32-bit value (including negatives) can be coded, in |
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134 // up to five bytes. The grammar is: |
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135 // low_byte = [0..191] |
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136 // high_byte = [192..255] |
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137 // any_byte = low_byte | high_byte |
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138 // coding = low_byte |
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139 // | high_byte low_byte |
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140 // | high_byte high_byte low_byte |
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141 // | high_byte high_byte high_byte low_byte |
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142 // | high_byte high_byte high_byte high_byte any_byte |
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143 // Each high_byte contributes six bits of payload. |
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144 // The encoding is one-to-one (except for integer overflow) |
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145 // and easy to parse and unparse. |
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146 |
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147 jint CompressedReadStream::read_int_mb(jint b0) { |
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148 int pos = position() - 1; |
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149 u_char* buf = buffer() + pos; |
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150 assert(buf[0] == b0 && b0 >= L, "correctly called"); |
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151 jint sum = b0; |
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152 // must collect more bytes: b[1]...b[4] |
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153 int lg_H_i = lg_H; |
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154 for (int i = 0; ; ) { |
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155 jint b_i = buf[++i]; // b_i = read(); ++i; |
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156 sum += b_i << lg_H_i; // sum += b[i]*(64**i) |
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157 if (b_i < L || i == MAX_i) { |
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158 set_position(pos+i+1); |
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159 return sum; |
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160 } |
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161 lg_H_i += lg_H; |
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162 } |
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163 } |
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164 |
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165 void CompressedWriteStream::write_int_mb(jint value) { |
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166 debug_only(int pos1 = position()); |
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167 juint sum = value; |
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168 for (int i = 0; ; ) { |
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169 if (sum < L || i == MAX_i) { |
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170 // remainder is either a "low code" or the 5th byte |
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171 assert(sum == (u_char)sum, "valid byte"); |
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172 write((u_char)sum); |
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173 break; |
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174 } |
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175 sum -= L; |
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176 int b_i = L + (sum % H); // this is a "high code" |
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177 sum >>= lg_H; // extracted 6 bits |
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178 write(b_i); ++i; |
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179 } |
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180 |
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181 #ifndef PRODUCT |
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182 if (test_compressed_stream_enabled) { // hack to enable this stress test |
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183 test_compressed_stream_enabled = false; |
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184 test_compressed_stream(0); |
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185 } |
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186 #endif |
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187 } |
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188 |
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189 |
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190 #ifndef PRODUCT |
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191 /// a unit test (can be run by hand from a debugger) |
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192 |
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193 // Avoid a VS2005 compiler stack overflow w/ fastdebug build. |
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194 // The following pragma optimize turns off optimization ONLY |
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195 // for this block (a matching directive turns it back on later). |
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196 // These directives can be removed once the MS VS.NET 2005 |
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197 // compiler stack overflow is fixed. |
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198 #if defined(_MSC_VER) && _MSC_VER >=1400 && !defined(_WIN64) |
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199 #pragma optimize("", off) |
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200 #pragma warning(disable: 4748) |
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201 #endif |
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202 |
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203 // generator for an "interesting" set of critical values |
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204 enum { stretch_limit = (1<<16) * (64-16+1) }; |
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205 static jlong stretch(jint x, int bits) { |
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206 // put x[high 4] into place |
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207 jlong h = (jlong)((x >> (16-4))) << (bits - 4); |
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208 // put x[low 12] into place, sign extended |
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209 jlong l = ((jlong)x << (64-12)) >> (64-12); |
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210 // move l upwards, maybe |
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211 l <<= (x >> 16); |
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212 return h ^ l; |
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213 } |
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214 |
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215 PRAGMA_DIAG_PUSH |
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216 PRAGMA_FORMAT_IGNORED // Someone needs to deal with this. |
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217 void test_compressed_stream(int trace) { |
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218 CompressedWriteStream bytes(stretch_limit * 100); |
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219 jint n; |
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220 int step = 0, fails = 0; |
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221 #define CHECKXY(x, y, fmt) { \ |
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222 ++step; \ |
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223 int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \ |
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224 if (trace > 0 && (step % trace) == 0) { \ |
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225 tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \ |
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226 step, n, x, xlen); } \ |
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227 if (x != y) { \ |
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228 tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \ |
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229 fails++; \ |
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230 } } |
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231 for (n = 0; n < (1<<8); n++) { |
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232 jbyte x = (jbyte)n; |
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233 bytes.write_byte(x); ++step; |
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234 } |
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235 for (n = 0; n < stretch_limit; n++) { |
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236 jint x = (jint)stretch(n, 32); |
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237 bytes.write_int(x); ++step; |
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238 bytes.write_signed_int(x); ++step; |
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239 bytes.write_float(jfloat_cast(x)); ++step; |
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240 } |
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241 for (n = 0; n < stretch_limit; n++) { |
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242 jlong x = stretch(n, 64); |
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243 bytes.write_long(x); ++step; |
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244 bytes.write_double(jdouble_cast(x)); ++step; |
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245 } |
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246 int length = bytes.position(); |
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247 if (trace != 0) |
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248 tty->print_cr("set up test of %d stream values, size %d", step, length); |
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249 step = 0; |
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250 // now decode it all |
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251 CompressedReadStream decode(bytes.buffer()); |
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252 int pos, lastpos = decode.position(); |
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253 for (n = 0; n < (1<<8); n++) { |
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254 jbyte x = (jbyte)n; |
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255 jbyte y = decode.read_byte(); |
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256 CHECKXY(x, y, "%db"); |
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257 } |
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258 for (n = 0; n < stretch_limit; n++) { |
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259 jint x = (jint)stretch(n, 32); |
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260 jint y1 = decode.read_int(); |
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261 CHECKXY(x, y1, "%du"); |
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262 jint y2 = decode.read_signed_int(); |
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263 CHECKXY(x, y2, "%di"); |
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264 jint y3 = jint_cast(decode.read_float()); |
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265 CHECKXY(x, y3, "%df"); |
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266 } |
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267 for (n = 0; n < stretch_limit; n++) { |
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268 jlong x = stretch(n, 64); |
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269 jlong y1 = decode.read_long(); |
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270 CHECKXY(x, y1, INT64_FORMAT "l"); |
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271 jlong y2 = jlong_cast(decode.read_double()); |
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272 CHECKXY(x, y2, INT64_FORMAT "d"); |
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273 } |
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274 int length2 = decode.position(); |
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275 if (trace != 0) |
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276 tty->print_cr("finished test of %d stream values, size %d", step, length2); |
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277 guarantee(length == length2, "bad length"); |
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278 guarantee(fails == 0, "test failures"); |
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279 } |
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280 PRAGMA_DIAG_POP |
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281 |
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282 #if defined(_MSC_VER) &&_MSC_VER >=1400 && !defined(_WIN64) |
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283 #pragma warning(default: 4748) |
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284 #pragma optimize("", on) |
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285 #endif |
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286 |
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287 #endif // PRODUCT |