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// Copyright 2020, Chef. All rights reserved.
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// https://github.com/q191201771/naza
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//
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// Use of this source code is governed by a MIT-style license
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// that can be found in the License file.
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//
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// Author: Chef (191201771@qq.com)
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package nazabits
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// TODO chef 这个package的性能可以优化
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// @param pos: 取值范围 [0, 7]，0表示最低位
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func GetBit8(v uint8, pos int) int {
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return GetBits8(v, pos, 1)
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}
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// @param pos: 取值范围 [0, 7]，0表示最低位
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// @param n: 取多少位， 取值范围 [1, 8]
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//
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// 举例，GetBits8(105, 2, 4) = 10（即1010）
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// v: 0110 1001
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// pos: 2
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// n: .. ..
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//
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func GetBits8(v uint8, pos int, n int) int {
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m := []uint8{0, 1, 3, 7, 15, 31, 63, 127, 255} // 0 is dummy
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return int(v >> uint(pos) & m[n])
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}
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func GetBit16(v []byte, pos int) int {
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if pos < 8 {
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return GetBit8(v[1], pos)
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}
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return GetBit8(v[0], pos-8)
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}
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func GetBits16(v []byte, pos int, n int) int {
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if pos < 8 {
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if pos+n < 9 {
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return GetBits8(v[1], pos, n)
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}
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return GetBits8(v[1], pos, 8-pos) | GetBits8(v[0], 0, pos+n-8)<<(8-uint8(pos))
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}
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return GetBits8(v[0], pos-8, n)
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}
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