tumble/bitfield/tool/gen.go

// Copyright 2016 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"fmt"
	"os"
)

func main() {
	f, err := os.Create("bf_table.gen.go")
	if err != nil {
		panic(err)
	}
	defer f.Close()

	w := func(format string, a ...interface{}) {
		_, err := fmt.Fprintf(f, format, a...)
		if err != nil {
			panic(err)
		}
	}

	w("// Copyright 2016 The LUCI Authors. All rights reserved.\n")
	w("// Use of this source code is governed under the Apache License, Version 2.0\n")
	w("// that can be found in the LICENSE file.\n\n")
	w("// AUTOGENERATED: DO NOT EDIT\n")
	w("\npackage bitfield\n\n")
	w("var bitCount = [256]byte{")
	tbl := [256]int{}
	for i := 0; i < 256; i++ {
		if i%16 == 0 {
			w("\n\t")
		} else {
			w(" ")
		}
		tbl[i] = (i & 1) + tbl[i/2]
		w("%d,", tbl[i])
	}
	w("\n}\n")
}