76 lines
2.3 KiB
Go
76 lines
2.3 KiB
Go
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// Copyright 2016 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package local
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import "github.com/prometheus/common/model"
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var (
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// bit masks for consecutive bits in a byte at various offsets.
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bitMask = [][]byte{
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{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // 0 bit
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{0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01}, // 1 bit
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{0xC0, 0x60, 0x30, 0x18, 0x0C, 0x06, 0x03, 0x01}, // 2 bit
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{0xE0, 0x70, 0x38, 0x1C, 0x0E, 0x07, 0x03, 0x01}, // 3 bit
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{0xF0, 0x78, 0x3C, 0x1E, 0x0F, 0x07, 0x03, 0x01}, // 4 bit
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{0xF8, 0x7C, 0x3E, 0x1F, 0x0F, 0x07, 0x03, 0x01}, // 5 bit
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{0xFC, 0x7E, 0x3F, 0x1F, 0x0F, 0x07, 0x03, 0x01}, // 6 bit
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{0xFE, 0x7F, 0x3F, 0x1F, 0x0F, 0x07, 0x03, 0x01}, // 7 bit
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{0xFF, 0x7F, 0x3F, 0x1F, 0x0F, 0x07, 0x03, 0x01}, // 8 bit
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}
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)
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// isInt32 returns true if v can be represented as an int32.
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func isInt32(v model.SampleValue) bool {
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return model.SampleValue(int32(v)) == v
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}
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// countBits returs the number of leading zero bits and the number of
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// significant bits after that in the given bit pattern. The maximum number of
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// leading zeros is 31 (so that it can be represented by a 5bit number). Leading
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// zeros beyond that are considered part of the significant bits.
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func countBits(pattern uint64) (leading, significant byte) {
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// TODO(beorn7): This would probably be faster with ugly endless switch
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// statements.
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if pattern == 0 {
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return
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}
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for pattern < 1<<63 {
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leading++
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pattern <<= 1
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}
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for pattern > 0 {
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significant++
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pattern <<= 1
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}
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if leading > 31 { // 5 bit limit.
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significant += leading - 31
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leading = 31
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}
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return
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}
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// isSignedIntN returns if n can be represented as a signed int with the given
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// bit length.
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func isSignedIntN(i int64, n byte) bool {
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upper := int64(1) << (n - 1)
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if i >= upper {
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return false
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}
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lower := upper - (1 << n)
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if i < lower {
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return false
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}
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return true
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}
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