diff options
Diffstat (limited to 'vendor/github.com/golang/geo/s2/bits_go18.go')
-rw-r--r-- | vendor/github.com/golang/geo/s2/bits_go18.go | 53 |
1 files changed, 0 insertions, 53 deletions
diff --git a/vendor/github.com/golang/geo/s2/bits_go18.go b/vendor/github.com/golang/geo/s2/bits_go18.go deleted file mode 100644 index 10a674da5..000000000 --- a/vendor/github.com/golang/geo/s2/bits_go18.go +++ /dev/null @@ -1,53 +0,0 @@ -// Copyright 2018 Google Inc. All rights reserved. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// +build !go1.9 - -package s2 - -// This file is for the bit manipulation code pre-Go 1.9. - -// findMSBSetNonZero64 returns the index (between 0 and 63) of the most -// significant set bit. Passing zero to this function returns zero. -func findMSBSetNonZero64(x uint64) int { - val := []uint64{0x2, 0xC, 0xF0, 0xFF00, 0xFFFF0000, 0xFFFFFFFF00000000} - shift := []uint64{1, 2, 4, 8, 16, 32} - var msbPos uint64 - for i := 5; i >= 0; i-- { - if x&val[i] != 0 { - x >>= shift[i] - msbPos |= shift[i] - } - } - return int(msbPos) -} - -const deBruijn64 = 0x03f79d71b4ca8b09 -const digitMask = uint64(1<<64 - 1) - -var deBruijn64Lookup = []byte{ - 0, 1, 56, 2, 57, 49, 28, 3, 61, 58, 42, 50, 38, 29, 17, 4, - 62, 47, 59, 36, 45, 43, 51, 22, 53, 39, 33, 30, 24, 18, 12, 5, - 63, 55, 48, 27, 60, 41, 37, 16, 46, 35, 44, 21, 52, 32, 23, 11, - 54, 26, 40, 15, 34, 20, 31, 10, 25, 14, 19, 9, 13, 8, 7, 6, -} - -// findLSBSetNonZero64 returns the index (between 0 and 63) of the least -// significant set bit. Passing zero to this function returns zero. -// -// This code comes from trailingZeroBits in https://golang.org/src/math/big/nat.go -// which references (Knuth, volume 4, section 7.3.1). -func findLSBSetNonZero64(x uint64) int { - return int(deBruijn64Lookup[((x&-x)*(deBruijn64&digitMask))>>58]) -} |