52 lines
1.2 KiB
Go
52 lines
1.2 KiB
Go
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// Copyright (c) 2019 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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import const(
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SYS_getrandom
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)
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// const (
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// SYS_getrandom = 278 // AArch65
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// SYS_getrandom = 384 // ARM
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// SYS_getrandom = 355 // x86
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// SYS_getrandom = 318 // x86_64
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// )
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const (
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ReadBatchSize = 256
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)
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pub fn read(bytes_needed int) ?[]byte {
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mut 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 > ReadBatchSize {
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no_batches := int(math.floor(f64(bytes_needed/ReadBatchSize)))
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for i:=0; i<no_batches; i++ {
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if _getrandom(ReadBatchSize, buffer+bytes_read) == -1 {
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return ReadError
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}
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bytes_read += ReadBatchSize
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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 ReadError
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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 > ReadBatchSize {
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panic('_getrandom() dont request more thane $ReadBatchSize bytes at once.')
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}
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return C.syscall(SYS_getrandom, buffer, bytes_needed, 0)
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}
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