mirror of
https://gitee.com/johng/gf.git
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73 lines
1.6 KiB
Go
73 lines
1.6 KiB
Go
// Copyright 2018 gf Author(https://github.com/gogf/gf). All Rights Reserved.
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//
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// This Source Code Form is subject to the terms of the MIT License.
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// If a copy of the MIT was not distributed with this file,
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// You can obtain one at https://github.com/gogf/gf.
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package grand
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import (
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"crypto/rand"
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"encoding/binary"
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"os"
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)
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const (
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// Buffer size for uint32 random number.
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gBUFFER_SIZE = 10000
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)
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var (
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// Buffer chan.
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bufferChan = make(chan uint32, gBUFFER_SIZE)
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)
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// It uses a asychronous goroutine to produce the random number,
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// and a buffer chan to store the random number. So it has high performance
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// to generate random number.
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func init() {
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step := 0
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buffer := make([]byte, 1024)
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go func() {
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for {
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if n, err := rand.Read(buffer); err != nil {
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panic(err)
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os.Exit(1)
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} else {
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// 使用缓冲区数据进行一次完整的随机数生成
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for i := 0; i < n-4; {
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bufferChan <- binary.LittleEndian.Uint32(buffer[i : i+4])
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i++
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}
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// 充分利用缓冲区数据，随机索引递增
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for i := 0; i < n; i++ {
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step = int(buffer[0]) % 10
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if step != 0 {
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break
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}
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}
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if step == 0 {
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step = 2
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}
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for i := 0; i < n-4; {
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bufferChan <- binary.BigEndian.Uint32(buffer[i : i+4])
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i += step
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}
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}
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}
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}()
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}
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// Intn returns a int number which is between 0 and max - [0, max).
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//
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// Note:
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// 1. The result is greater than or equal to 0, but less than <max>;
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// 2. The result number is 32bit and less than math.MaxUint32.
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func Intn(max int) int {
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n := int(<-bufferChan) % max
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if (max > 0 && n < 0) || (max < 0 && n > 0) {
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return -n
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}
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return n
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}
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