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