mirror of
https://github.com/TwiN/gatus.git
synced 2024-12-01 20:33:29 +01:00
82 lines
2.4 KiB
Go
82 lines
2.4 KiB
Go
/*
|
|
Copyright 2014 Google Inc. All rights reserved.
|
|
|
|
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 bytesource provides a rand.Source64 that is determined by a slice of bytes.
|
|
package bytesource
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"io"
|
|
"math/rand"
|
|
)
|
|
|
|
// ByteSource implements rand.Source64 determined by a slice of bytes. The random numbers are
|
|
// generated from each 8 bytes in the slice, until the last bytes are consumed, from which a
|
|
// fallback pseudo random source is created in case more random numbers are required.
|
|
// It also exposes a `bytes.Reader` API, which lets callers consume the bytes directly.
|
|
type ByteSource struct {
|
|
*bytes.Reader
|
|
fallback rand.Source
|
|
}
|
|
|
|
// New returns a new ByteSource from a given slice of bytes.
|
|
func New(input []byte) *ByteSource {
|
|
s := &ByteSource{
|
|
Reader: bytes.NewReader(input),
|
|
fallback: rand.NewSource(0),
|
|
}
|
|
if len(input) > 0 {
|
|
s.fallback = rand.NewSource(int64(s.consumeUint64()))
|
|
}
|
|
return s
|
|
}
|
|
|
|
func (s *ByteSource) Uint64() uint64 {
|
|
// Return from input if it was not exhausted.
|
|
if s.Len() > 0 {
|
|
return s.consumeUint64()
|
|
}
|
|
|
|
// Input was exhausted, return random number from fallback (in this case fallback should not be
|
|
// nil). Try first having a Uint64 output (Should work in current rand implementation),
|
|
// otherwise return a conversion of Int63.
|
|
if s64, ok := s.fallback.(rand.Source64); ok {
|
|
return s64.Uint64()
|
|
}
|
|
return uint64(s.fallback.Int63())
|
|
}
|
|
|
|
func (s *ByteSource) Int63() int64 {
|
|
return int64(s.Uint64() >> 1)
|
|
}
|
|
|
|
func (s *ByteSource) Seed(seed int64) {
|
|
s.fallback = rand.NewSource(seed)
|
|
s.Reader = bytes.NewReader(nil)
|
|
}
|
|
|
|
// consumeUint64 reads 8 bytes from the input and convert them to a uint64. It assumes that the the
|
|
// bytes reader is not empty.
|
|
func (s *ByteSource) consumeUint64() uint64 {
|
|
var bytes [8]byte
|
|
_, err := s.Read(bytes[:])
|
|
if err != nil && err != io.EOF {
|
|
panic("failed reading source") // Should not happen.
|
|
}
|
|
return binary.BigEndian.Uint64(bytes[:])
|
|
}
|