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v/vlib/crypto/rand/rand_lin.v
2019-10-24 14:48:20 +03:00

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V

// Copyright (c) 2019 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
import math
#include <sys/syscall.h>
const (
read_batch_size = 256
)
pub fn read(bytes_needed int) ?[]byte {
mut buffer := malloc(bytes_needed)
mut bytes_read := 0
// getrandom syscall wont block if requesting <= 256 bytes
if bytes_needed > read_batch_size {
no_batches := int(math.floor(f64(bytes_needed/read_batch_size)))
for i:=0; i<no_batches; i++ {
if getrandom(read_batch_size, buffer+bytes_read) == -1 {
return read_error
}
bytes_read += read_batch_size
}
}
if getrandom(bytes_needed-bytes_read, buffer+bytes_read) == -1 {
return read_error
}
return c_array_to_bytes_tmp(bytes_needed, buffer)
}
fn getrandom(bytes_needed int, buffer voidptr) int {
if bytes_needed > read_batch_size {
panic('getrandom() dont request more thane $read_batch_size bytes at once.')
}
return C.syscall(C.SYS_getrandom, buffer, bytes_needed, 0)
}