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Source file src/crypto/rand/rand_windows.go

Documentation: crypto/rand

  // 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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