v/vlib/crypto/rand/rand_lin.v

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// 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 (
// SYS_getrandom = 278 // AArch65
// SYS_getrandom = 384 // ARM
// SYS_getrandom = 355 // x86
// SYS_getrandom = 318 // x86_64
// )
const (
ReadBatchSize = 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 > ReadBatchSize {
no_batches := int(math.floor(f64(bytes_needed/ReadBatchSize)))
for i:=0; i<no_batches; i++ {
if getrandom(ReadBatchSize, buffer+bytes_read) == -1 {
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return ReadError
}
bytes_read += ReadBatchSize
}
}
if getrandom(bytes_needed-bytes_read, buffer+bytes_read) == -1 {
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return ReadError
}
return c_array_to_bytes_tmp(bytes_needed, buffer)
}
fn getrandom(bytes_needed int, buffer voidptr) int {
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if bytes_needed > ReadBatchSize {
panic('getrandom() dont request more thane $ReadBatchSize bytes at once.')
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}
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return C.syscall(C.SYS_getrandom, buffer, bytes_needed, 0)
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}