d3769b2fbc
UnsafeStrToBytes is currently not safe for -d=checkptr=2, since when it cast from smaller struct (string) to bigger struct ([]byte). That causes checkptr complains as the casting straddle multiple heap objects. To fix this, we have to get the string header first, then use its fields to construct the slice. New implementation performs the same speed with the old (wrong) one. name old time/op new time/op delta UnsafeStrToBytes-8 25.7ns ± 1% 25.7ns ± 3% ~ (p=0.931 n=10+17) name old alloc/op new alloc/op delta UnsafeStrToBytes-8 7.00B ± 0% 7.00B ± 0% ~ (all equal) name old allocs/op new allocs/op delta UnsafeStrToBytes-8 0.00 0.00 ~ (all equal) While at it, also simplify UnsafeBytesToStr implementation, since when we can pass the slice directly to unsafe.Pointer, instead of getting the slice header first.
27 lines
768 B
Go
27 lines
768 B
Go
package conv
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import (
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"reflect"
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"unsafe"
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)
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// UnsafeStrToBytes uses unsafe to convert string into byte array. Returned bytes
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// must not be altered after this function is called as it will cause a segmentation fault.
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func UnsafeStrToBytes(s string) []byte {
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var buf []byte
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sHdr := (*reflect.StringHeader)(unsafe.Pointer(&s))
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bufHdr := (*reflect.SliceHeader)(unsafe.Pointer(&buf))
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bufHdr.Data = sHdr.Data
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bufHdr.Cap = sHdr.Len
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bufHdr.Len = sHdr.Len
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return buf
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}
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// UnsafeBytesToStr is meant to make a zero allocation conversion
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// from []byte -> string to speed up operations, it is not meant
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// to be used generally, but for a specific pattern to delete keys
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// from a map.
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func UnsafeBytesToStr(b []byte) string {
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return *(*string)(unsafe.Pointer(&b))
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}
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