40 lines
1.1 KiB
V
40 lines
1.1 KiB
V
// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
|
|
// Use of this source code is governed by an MIT license
|
|
// that can be found in the LICENSE file.
|
|
module rand
|
|
|
|
#include <sys/syscall.h>
|
|
|
|
const (
|
|
read_batch_size = 256
|
|
)
|
|
|
|
// read returns an array of `bytes_needed` random bytes read from the OS.
|
|
pub fn read(bytes_needed int) ?[]byte {
|
|
mut buffer := unsafe { malloc_noscan(bytes_needed) }
|
|
mut bytes_read := 0
|
|
mut remaining_bytes := bytes_needed
|
|
// getrandom syscall wont block if requesting <= 256 bytes
|
|
for bytes_read < bytes_needed {
|
|
batch_size := if remaining_bytes > rand.read_batch_size {
|
|
rand.read_batch_size
|
|
} else {
|
|
remaining_bytes
|
|
}
|
|
rbytes := unsafe { getrandom(batch_size, buffer + bytes_read) }
|
|
if rbytes == -1 {
|
|
unsafe { free(buffer) }
|
|
return IError(&ReadError{})
|
|
}
|
|
bytes_read += rbytes
|
|
}
|
|
return unsafe { buffer.vbytes(bytes_needed) }
|
|
}
|
|
|
|
fn getrandom(bytes_needed int, buffer voidptr) int {
|
|
if bytes_needed > rand.read_batch_size {
|
|
panic('getrandom() dont request more than $rand.read_batch_size bytes at once.')
|
|
}
|
|
return unsafe { C.syscall(C.SYS_getrandom, buffer, bytes_needed, 0) }
|
|
}
|