go rotate 源码

golang rotate 代码

文件路径：/test/rotate.go

// skip

// NOTE: the actual tests to run are rotate[0123].go

// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Generate test of shift and rotate by constants.
// The output is compiled and run.
//
// The integer type depends on the value of mode (rotate direction,
// signedness).

package main

import (
	"bufio"
	"flag"
	"fmt"
	"os"
	"strings"
)

func main() {
	flag.Parse()

	b := bufio.NewWriter(os.Stdout)
	defer b.Flush()

	fmt.Fprintf(b, "%s\n", prolog)

	for logBits := uint(3); logBits <= 6; logBits++ {
		typ := fmt.Sprintf("int%d", 1<<logBits)
		fmt.Fprint(b, strings.Replace(checkFunc, "XXX", typ, -1))
		fmt.Fprint(b, strings.Replace(checkFunc, "XXX", "u"+typ, -1))
		gentest(b, 1<<logBits, mode&1 != 0, mode&2 != 0)
	}
}

const prolog = `

package main

import (
	"fmt"
	"os"
)

var (
	i8 int8 = 0x12
	i16 int16 = 0x1234
	i32 int32 = 0x12345678
	i64 int64 = 0x123456789abcdef0
	ui8 uint8 = 0x12
	ui16 uint16 = 0x1234
	ui32 uint32 = 0x12345678
	ui64 uint64 = 0x123456789abcdef0

	ni8 = ^i8
	ni16 = ^i16
	ni32 = ^i32
	ni64 = ^i64
	nui8 = ^ui8
	nui16 = ^ui16
	nui32 = ^ui32
	nui64 = ^ui64
)

var nfail = 0

func main() {
	if nfail > 0 {
		fmt.Printf("BUG\n")
	}
}

`

const checkFunc = `
func check_XXX(desc string, have, want XXX) {
	if have != want {
		nfail++
		fmt.Printf("%s = %T(%#x), want %T(%#x)\n", desc, have, have, want, want)
		if nfail >= 100 {
			fmt.Printf("BUG: stopping after 100 failures\n")
			os.Exit(0)
		}
	}
}
`

var (
	uop = [2]func(x, y uint64) uint64{
		func(x, y uint64) uint64 {
			return x | y
		},
		func(x, y uint64) uint64 {
			return x ^ y
		},
	}
	iop = [2]func(x, y int64) int64{
		func(x, y int64) int64 {
			return x | y
		},
		func(x, y int64) int64 {
			return x ^ y
		},
	}
	cop = [2]byte{'|', '^'}
)

func gentest(b *bufio.Writer, bits uint, unsigned, inverted bool) {
	fmt.Fprintf(b, "func init() {\n")
	defer fmt.Fprintf(b, "}\n")
	n := 0

	// Generate tests for left/right and right/left.
	for l := uint(0); l <= bits; l++ {
		for r := uint(0); r <= bits; r++ {
			for o, op := range cop {
				typ := fmt.Sprintf("int%d", bits)
				v := fmt.Sprintf("i%d", bits)
				if unsigned {
					typ = "u" + typ
					v = "u" + v
				}
				v0 := int64(0x123456789abcdef0)
				if inverted {
					v = "n" + v
					v0 = ^v0
				}
				expr1 := fmt.Sprintf("%s<<%d %c %s>>%d", v, l, op, v, r)
				expr2 := fmt.Sprintf("%s>>%d %c %s<<%d", v, r, op, v, l)

				var result string
				if unsigned {
					v := uint64(v0) >> (64 - bits)
					v = uop[o](v<<l, v>>r)
					v <<= 64 - bits
					v >>= 64 - bits
					result = fmt.Sprintf("%#x", v)
				} else {
					v := int64(v0) >> (64 - bits)
					v = iop[o](v<<l, v>>r)
					v <<= 64 - bits
					v >>= 64 - bits
					result = fmt.Sprintf("%#x", v)
				}

				fmt.Fprintf(b, "\tcheck_%s(%q, %s, %s(%s))\n", typ, expr1, expr1, typ, result)
				fmt.Fprintf(b, "\tcheck_%s(%q, %s, %s(%s))\n", typ, expr2, expr2, typ, result)

				// Chop test into multiple functions so that there's not one
				// enormous function to compile/link.
				// All the functions are named init so we don't have to do
				// anything special to call them.  ☺
				if n++; n >= 50 {
					fmt.Fprintf(b, "}\n")
					fmt.Fprintf(b, "func init() {\n")
					n = 0
				}
			}
		}
	}
}

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