41 lines
1.0 KiB
V
41 lines
1.0 KiB
V
// Copyright (c) 2019-2020 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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import math
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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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pub fn read(bytes_needed int) ?[]byte {
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buffer := malloc(bytes_needed)
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mut bytes_read := 0
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// getrandom syscall wont block if requesting <= 256 bytes
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if bytes_needed > read_batch_size {
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no_batches := int(math.floor(f64(bytes_needed/read_batch_size)))
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for i:=0; i<no_batches; i++ {
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if getrandom(read_batch_size, buffer+bytes_read) == -1 {
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return read_error
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}
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bytes_read += read_batch_size
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}
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}
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if getrandom(bytes_needed-bytes_read, buffer+bytes_read) == -1 {
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return read_error
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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 C.syscall(C.SYS_getrandom, buffer, bytes_needed, 0)
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}
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