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// Copyright (c) 2019-2024 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 read_batch_size = 256
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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) ![]u8 {
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	mut buffer := unsafe { vcalloc_noscan(bytes_needed) }
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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 {
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			read_batch_size
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		} else {
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			remaining_bytes
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		}
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		rbytes := unsafe { getrandom(batch_size, buffer + bytes_read) }
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		if rbytes == -1 {
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			unsafe { free(buffer) }
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			return &ReadError{}
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		}
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		bytes_read += rbytes
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	}
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	return unsafe { buffer.vbytes(bytes_needed) }
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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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