Golang 合并 byte 的性能比较，选择比较快的方式合并 byte
concat.go
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package concat
func concatCopyPreAllocate(slices [][]byte) []byte {
var totalLen int
for _, s := range slices {
totalLen += len(s)
}
tmp := make([]byte, totalLen)
var i int
for _, s := range slices {
i += copy(tmp[i:], s)
}
return tmp
}
func concatAppend(slices [][]byte) []byte {
var tmp []byte
for _, s := range slices {
tmp = append(tmp, s...)
}
return tmp
}
concat_test.go
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package concat
import "testing"
var slices = [][]byte{
[]byte("my first slice"),
[]byte("second slice"),
[]byte("third slice"),
[]byte("fourth slice"),
[]byte("fifth slice"),
}
var B []byte
func BenchmarkConcatCopyPreAllocate(b *testing.B) {
for n := 0; n < b.N; n++ {
B = concatCopyPreAllocate(slices)
}
}
func BenchmarkConcatAppend(b *testing.B) {
for n := 0; n < b.N; n++ {
B = concatAppend(slices)
}
}
运行结果
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$ go test . -bench=. -benchmem
goos: darwin
goarch: amd64
BenchmarkConcatCopyPreAllocate-8 20000000 59.2 ns/op 64 B/op 1 allocs/op
BenchmarkConcatAppend-8 10000000 128 ns/op 112 B/op 3 allocs/op
PASS
ok _/Users/yourname/tmp/golang/concat 2.683s
第一种 concatCopyPreAllocate 的速度是第二种 concatAppend 的两倍。
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