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// Copyright 2010 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.
// Windows cryptographically secure pseudorandom number
// generator.
package rand
import (
"os"
"sync"
"syscall"
)
// Implemented by using Windows CryptoAPI 2.0.
func init() { Reader = &rngReader{} }
// A rngReader satisfies reads by reading from the Windows CryptGenRandom API.
type rngReader struct {
prov syscall.Handle
mu sync.Mutex
}
func (r *rngReader) Read(b []byte) (n int, err error) {
r.mu.Lock()
if r.prov == 0 {
const provType = syscall.PROV_RSA_FULL
const flags = syscall.CRYPT_VERIFYCONTEXT | syscall.CRYPT_SILENT
err := syscall.CryptAcquireContext(&r.prov, nil, nil, provType, flags)
if err != nil {
r.mu.Unlock()
return 0, os.NewSyscallError("CryptAcquireContext", err)
}
}
r.mu.Unlock()
if len(b) == 0 {
return 0, nil
}
err = syscall.CryptGenRandom(r.prov, uint32(len(b)), &b[0])
if err != nil {
return 0, os.NewSyscallError("CryptGenRandom", err)
}
return len(b), nil
}
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