【解决一个小问题】golang 的 `-race`选项导致 unsafe代码 panic
作者:张富春(ahfuzhang)，转载时请注明作者和引用链接，谢谢！[*]cnblogs博客
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https://img2022.cnblogs.com/blog/1457949/202202/1457949-20220216153819145-1193738712.png
为了提升性能，使用 unsafe 代码来重构了凯撒加密的代码。代码如下：
const (
lowerCaseAlphabet = "abcdefghijklmnopqrstuvwxyz"
upperCaseAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
)
var (
lowerCaseAlphabetArr = []byte(lowerCaseAlphabet)
upperCaseAlphabetArr = []byte(upperCaseAlphabet)
tableOflowerCaseAlphabet = unsafe.Pointer(&lowerCaseAlphabetArr)
tableOfupperCaseAlphabe= unsafe.Pointer(&upperCaseAlphabetArr)
)
// CaesarFastEncode fast version
func CaesarFastEncode(in []byte, out []byte, rot int) {
start := unsafe.Pointer(&in)
target := unsafe.Pointer(&out)
for i := 0; i < len(in); i++ {
c := *((*byte)(start))
if c == '.' {
*((*byte)(target)) = '='
} else if c >= 'a' && c <= 'z' {
idx := (int(26+(c-'a')) + rot) % 26
*((*byte)(target)) = *((*byte)(unsafe.Pointer(uintptr(tableOflowerCaseAlphabet) + uintptr(idx))))
} else if c >= 'A' && c <= 'Z' {
idx := (int(26+(c-'A')) + rot) % 26
*((*byte)(target)) = *((*byte)(unsafe.Pointer(uintptr(tableOfupperCaseAlphabe) + uintptr(idx))))
} else {
*((*byte)(target)) = *((*byte)(start))
}
start = unsafe.Pointer(uintptr(start) + uintptr(1))
target = unsafe.Pointer(uintptr(target) + uintptr(1))
}
}由此看来，只要使用了 unsafe 代码，都应该加上-race选项。
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