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fat: add template function randomKubernetesName (#48)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| /* | ||
| Copyright 2015 The Kubernetes 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 util provides utilities related to randomization. | ||
| package util | ||
|
|
||
| import ( | ||
| "math/rand" | ||
| "sync" | ||
| "time" | ||
| ) | ||
|
|
||
| var rng = struct { | ||
| sync.Mutex | ||
| rand *rand.Rand | ||
| }{ | ||
| rand: rand.New(rand.NewSource(time.Now().UnixNano())), | ||
| } | ||
|
|
||
| const ( | ||
| // We omit vowels from the set of available characters to reduce the chances | ||
| // of "bad words" being formed. | ||
| alphanums = "bcdfghjklmnpqrstvwxz2456789" | ||
| // No. of bits required to index into alphanums string. | ||
| alphanumsIdxBits = 5 | ||
| // Mask used to extract last alphanumsIdxBits of an int. | ||
| alphanumsIdxMask = 1<<alphanumsIdxBits - 1 | ||
| // No. of random letters we can extract from a single int63. | ||
| maxAlphanumsPerInt = 63 / alphanumsIdxBits | ||
| ) | ||
|
|
||
| // String generates a random alphanumeric string, without vowels, which is n | ||
| // characters long. This will panic if n is less than zero. | ||
| // How the random string is created: | ||
| // - we generate random int63's | ||
| // - from each int63, we are extracting multiple random letters by bit-shifting and masking | ||
| // - if some index is out of range of alphanums we neglect it (unlikely to happen multiple times in a row) | ||
| func String(n int) string { | ||
| b := make([]byte, n) | ||
| rng.Lock() | ||
| defer rng.Unlock() | ||
|
|
||
| randomInt63 := rng.rand.Int63() | ||
| remaining := maxAlphanumsPerInt | ||
| for i := 0; i < n; { | ||
| if remaining == 0 { | ||
| randomInt63, remaining = rng.rand.Int63(), maxAlphanumsPerInt | ||
| } | ||
| if idx := int(randomInt63 & alphanumsIdxMask); idx < len(alphanums) { | ||
| b[i] = alphanums[idx] | ||
| i++ | ||
| } | ||
| randomInt63 >>= alphanumsIdxBits | ||
| remaining-- | ||
| } | ||
| return string(b) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,54 @@ | ||
| /* | ||
| Copyright 2015 The Kubernetes 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 util | ||
|
|
||
| import ( | ||
| "strings" | ||
| "testing" | ||
| ) | ||
|
|
||
| const ( | ||
| maxRangeTestCount = 500 | ||
| testStringLength = 32 | ||
| ) | ||
|
|
||
| func TestString(t *testing.T) { | ||
| valid := "bcdfghjklmnpqrstvwxz2456789" | ||
| for _, l := range []int{0, 1, 2, 10, 123} { | ||
| s := String(l) | ||
| if len(s) != l { | ||
| t.Errorf("expected string of size %d, got %q", l, s) | ||
| } | ||
| for _, c := range s { | ||
| if !strings.ContainsRune(valid, c) { | ||
| t.Errorf("expected valid characters, got %v", c) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| func BenchmarkRandomStringGeneration(b *testing.B) { | ||
| b.ResetTimer() | ||
| var s string | ||
| for i := 0; i < b.N; i++ { | ||
| s = String(testStringLength) | ||
| } | ||
| b.StopTimer() | ||
| if len(s) == 0 { | ||
| b.Fatal(s) | ||
| } | ||
| } |
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