package bzip2

import "bytes"
import "testing"

const mask  = 0xffffffffffff
const magic = 0x314159265359

var filter = func() (c [256]bool) {
    for i := uint(0); i < 8; i++ {
        c[0xff&(magic>>i)] = true
    }
    return c
}()

func BenchmarkSync(b *testing.B) {
    buf := bytes.Repeat([]byte{0x31, 0x41, 0x59, 0x26, 0x53, 0x59}, 1<<18)

    b.SetBytes(int64(len(buf)))
    b.ResetTimer()

    var ofs []int64
    for n := 0; n < b.N; n++ {
        ofs = ofs[:0]

        var sync uint64
        for i, b := range buf {
            sync = sync<<8 | uint64(b)
            if filter[byte(sync>>8)] && i >= 6 && (false ||
                sync&(mask<<7) == magic<<7 || sync&(mask<<8) == magic<<8 ||
                sync&(mask<<5) == magic<<5 || sync&(mask<<6) == magic<<6 ||
                sync&(mask<<3) == magic<<3 || sync&(mask<<4) == magic<<4 ||
                sync&(mask<<1) == magic<<1 || sync&(mask<<2) == magic<<2) {
                ofs = append(ofs, int64(i-6))
            }
        }
    }
}