[squeak-dev] The Trunk: Kernel-nice.569.mcz

commits at source.squeak.org commits at source.squeak.org
Tue Jun 21 21:22:19 UTC 2011

```Chris Muller uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-nice.569.mcz

==================== Summary ====================

Name: Kernel-nice.569
Author: nice
Time: 12 April 2011, 9:22:32.787 am
UUID: 6fde25b5-ec3e-3146-94b5-d9e228e02776
Ancestors: Kernel-cmm.568

A bit faster bitReverse: for LargePositiveInteger

=============== Diff against Kernel-cmm.568 ===============

+ ----- Method: LargePositiveInteger>>bitReverse: (in category 'bit manipulation') -----
+ bitReverse: highBit
+ 	"This implementation is faster than super"
+
+ 	| digitSize reversed |
+ 	highBit < self highBit ifTrue: [ self error: 'Not enough bits.' ].
+ 	digitSize := highBit + 7 // 8.
+ 	reversed := self class new: digitSize.
+ 	1 to: self digitLength do: [:i |
+ 		reversed digitAt: digitSize + 1 - i put: (self digitAt: i) byteReversed].
+ 	^reversed bitShift: highBit - (digitSize * 8)!

+ ----- Method: SmallInteger>>byteReversed (in category 'bit manipulation') -----
+ byteReversed
+ 	The receiver must be between 0 and 255.
+ 	The constant has been obtained by this snippet:
+ 	(0 to: 255) collect: [:e |
+ 		| r |
+ 		r := ((e bitAnd: 2r11110000) bitShift: -4) + ((e bitAnd: 2r00001111) bitShift: 4).
+ 		r := ((r bitAnd: 2r11001100) bitShift: -2) + ((r bitAnd: 2r00110011) bitShift: 2).
+ 		((r bitAnd: 2r10101010) bitShift: -1) + ((r bitAnd: 2r01010101) bitShift: 1).] as: ByteArray"
+
+ 	^#[0 128 64 192 32 160 96 224 16 144 80 208 48 176 112 240 8 136 72 200 40 168 104 232 24 152 88 216 56 184 120 248 4 132 68 196 36 164 100 228 20 148 84 212 52 180 116 244 12 140 76 204 44 172 108 236 28 156 92 220 60 188 124 252 2 130 66 194 34 162 98 226 18 146 82 210 50 178 114 242 10 138 74 202 42 170 106 234 26 154 90 218 58 186 122 250 6 134 70 198 38 166 102 230 22 150 86 214 54 182 118 246 14 142 78 206 46 174 110 238 30 158 94 222 62 190 126 254 1 129 65 193 33 161 97 225 17 145 81 209 49 177 113 241 9 137 73 201 41 169 105 233 25 153 89 217 57 185 121 249 5 133 69 197 37 165 101 229 21 149 85 213 53 181 117 245 13 141 77 205 45 173 109 237 29 157 93 221 61 189 125 253 3 131 67 195 35 163 99 227 19 147 83 211 51 179 115 243 11 139 75 203 43 171 107 235 27 155 91 219 59 187 123 251 7 135 71 199 39 167 103 231 23 151 87 215 55 183 119 247 15 143 79 207 47 175 111 239 31 159 95 223 63 191 127 255] at: 1 + self!

```