github.com/spotmaxtech/k8s-apimachinery-v0260@v0.0.1/pkg/util/rand/rand.go (about)

     1  /*
     2  Copyright 2015 The Kubernetes Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  // Package rand provides utilities related to randomization.
    18  package rand
    19  
    20  import (
    21  	"math/rand"
    22  	"sync"
    23  	"time"
    24  )
    25  
    26  var rng = struct {
    27  	sync.Mutex
    28  	rand *rand.Rand
    29  }{
    30  	rand: rand.New(rand.NewSource(time.Now().UnixNano())),
    31  }
    32  
    33  // Int returns a non-negative pseudo-random int.
    34  func Int() int {
    35  	rng.Lock()
    36  	defer rng.Unlock()
    37  	return rng.rand.Int()
    38  }
    39  
    40  // Intn generates an integer in range [0,max).
    41  // By design this should panic if input is invalid, <= 0.
    42  func Intn(max int) int {
    43  	rng.Lock()
    44  	defer rng.Unlock()
    45  	return rng.rand.Intn(max)
    46  }
    47  
    48  // IntnRange generates an integer in range [min,max).
    49  // By design this should panic if input is invalid, <= 0.
    50  func IntnRange(min, max int) int {
    51  	rng.Lock()
    52  	defer rng.Unlock()
    53  	return rng.rand.Intn(max-min) + min
    54  }
    55  
    56  // IntnRange generates an int64 integer in range [min,max).
    57  // By design this should panic if input is invalid, <= 0.
    58  func Int63nRange(min, max int64) int64 {
    59  	rng.Lock()
    60  	defer rng.Unlock()
    61  	return rng.rand.Int63n(max-min) + min
    62  }
    63  
    64  // Seed seeds the rng with the provided seed.
    65  func Seed(seed int64) {
    66  	rng.Lock()
    67  	defer rng.Unlock()
    68  
    69  	rng.rand = rand.New(rand.NewSource(seed))
    70  }
    71  
    72  // Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n)
    73  // from the default Source.
    74  func Perm(n int) []int {
    75  	rng.Lock()
    76  	defer rng.Unlock()
    77  	return rng.rand.Perm(n)
    78  }
    79  
    80  const (
    81  	// We omit vowels from the set of available characters to reduce the chances
    82  	// of "bad words" being formed.
    83  	alphanums = "bcdfghjklmnpqrstvwxz2456789"
    84  	// No. of bits required to index into alphanums string.
    85  	alphanumsIdxBits = 5
    86  	// Mask used to extract last alphanumsIdxBits of an int.
    87  	alphanumsIdxMask = 1<<alphanumsIdxBits - 1
    88  	// No. of random letters we can extract from a single int63.
    89  	maxAlphanumsPerInt = 63 / alphanumsIdxBits
    90  )
    91  
    92  // String generates a random alphanumeric string, without vowels, which is n
    93  // characters long.  This will panic if n is less than zero.
    94  // How the random string is created:
    95  // - we generate random int63's
    96  // - from each int63, we are extracting multiple random letters by bit-shifting and masking
    97  // - if some index is out of range of alphanums we neglect it (unlikely to happen multiple times in a row)
    98  func String(n int) string {
    99  	b := make([]byte, n)
   100  	rng.Lock()
   101  	defer rng.Unlock()
   102  
   103  	randomInt63 := rng.rand.Int63()
   104  	remaining := maxAlphanumsPerInt
   105  	for i := 0; i < n; {
   106  		if remaining == 0 {
   107  			randomInt63, remaining = rng.rand.Int63(), maxAlphanumsPerInt
   108  		}
   109  		if idx := int(randomInt63 & alphanumsIdxMask); idx < len(alphanums) {
   110  			b[i] = alphanums[idx]
   111  			i++
   112  		}
   113  		randomInt63 >>= alphanumsIdxBits
   114  		remaining--
   115  	}
   116  	return string(b)
   117  }
   118  
   119  // SafeEncodeString encodes s using the same characters as rand.String. This reduces the chances of bad words and
   120  // ensures that strings generated from hash functions appear consistent throughout the API.
   121  func SafeEncodeString(s string) string {
   122  	r := make([]byte, len(s))
   123  	for i, b := range []rune(s) {
   124  		r[i] = alphanums[(int(b) % len(alphanums))]
   125  	}
   126  	return string(r)
   127  }