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v/vlib/crypto/rand/rand_linux.c.v

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// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// 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 (
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read_batch_size = 256
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)
// read returns an array of `bytes_needed` random bytes read from the OS.
pub fn read(bytes_needed int) ?[]byte {
mut buffer := &byte(0)
unsafe {
buffer = malloc(bytes_needed)
}
mut bstart := buffer
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mut bytes_read := 0
mut remaining_bytes := bytes_needed
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// getrandom syscall wont block if requesting <= 256 bytes
for bytes_read < bytes_needed {
batch_size := if remaining_bytes > read_batch_size { read_batch_size } else { remaining_bytes }
unsafe {
bstart = buffer + bytes_read
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}
rbytes := getrandom(batch_size, bstart)
if rbytes == -1 {
unsafe { free(buffer) }
return read_error
}
bytes_read += rbytes
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}
return c_array_to_bytes_tmp(bytes_needed, buffer)
}
fn getrandom(bytes_needed int, buffer voidptr) int {
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if bytes_needed > read_batch_size {
panic('getrandom() dont request more than $read_batch_size bytes at once.')
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}
return unsafe { C.syscall(C.SYS_getrandom, buffer, bytes_needed, 0) }
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}