rdseed/
lib.rs

1// Rust interface to RDSEED / RDRAND
2//
3// Written by Radim Kolar <hsn@sendmail.cz> 2026
4//
5// SPDX-License-Identifier: CC0-1.0 OR Unlicense
6
7/// Attempts to get a 64-bit seed from the hardware.
8///
9/// ## Returns
10///   Some(u64) if successful
11///   None if the hardware was busy or operation is not supported
12///
13/// ## See also
14///
15/// 1. [is_available] - checks if hardware supports RDSEED instruction.
16/// 1. [get32] - get 32-bit seed from the hardware.
17/// 1. [get16] - get 16-bit seed from the hardware.
18pub fn get64() -> Option<u64> {
19   #[cfg(target_arch = "x86_64")]
20   {
21      use std::arch::x86_64::_rdseed64_step;
22
23      // Check if the CPU supports RDSEED at runtime is recommended,
24      // but for the raw instruction call:
25      let mut seed = 0u64;
26      unsafe {
27         // _rdseed64_step returns 1 if a valid value was obtained
28         if _rdseed64_step(&mut seed) == 1 {
29            return Some(seed);
30         }
31      }
32   }
33   None
34}
35
36/// Attempts to get a 32-bit seed from the hardware.
37///
38/// ## Returns
39///   Some(u32) if successful
40///   None if the hardware was busy or operation is not supported
41///
42/// ## See also
43///
44/// 1. [is_available] - checks if hardware supports RDSEED instruction.
45/// 1. [get64] - get 64-bit seed from the hardware.
46/// 1. [get16] - get 16-bit seed from the hardware.
47
48pub fn get32() -> Option<u32> {
49   #[cfg(target_arch = "x86_64")]
50   {
51      use std::arch::x86_64::_rdseed32_step;
52
53      // Check if the CPU supports RDSEED at runtime is recommended,
54      // but for the raw instruction call:
55      let mut seed = 0u32;
56      unsafe {
57         // _rdseed32_step returns 1 if a valid value was obtained
58         if _rdseed32_step(&mut seed) == 1 {
59            return Some(seed);
60         }
61      }
62   }
63   None
64}
65
66/// Attempts to get a 16-bit seed from the hardware.
67///
68/// ## Returns
69///   Some(u16) if successful
70///   None if the hardware was busy or operation is not supported
71///
72/// ## See also
73///
74/// 1. [is_available] - checks if hardware supports RDSEED instruction.
75/// 1. [get64] - get 64-bit seed from the hardware.
76/// 1. [get32] - get 32-bit seed from the hardware.
77pub fn get16() -> Option<u16> {
78   #[cfg(target_arch = "x86_64")]
79   {
80      use std::arch::x86_64::_rdseed16_step;
81
82      // Check if the CPU supports RDSEED at runtime is recommended,
83      // but for the raw instruction call:
84      let mut seed = 0u16;
85      unsafe {
86         // _rdseed16_step returns 1 if a valid value was obtained
87         if _rdseed16_step(&mut seed) == 1 {
88            return Some(seed);
89         }
90      }
91   }
92   None
93}
94
95
96/// Checks if hardware supports RDSEED instruction.
97///
98/// ## Returns
99///   true if the current CPU supports the RDSEED instruction.
100pub fn is_available() -> bool {
101   #[cfg(target_arch = "x86_64")]
102   {
103      // This macro performs a runtime check using the CPUID instruction
104      if is_x86_feature_detected!("rdseed") {
105         return true;
106      }
107   }
108
109   // Always return false if not on x86_64 or if feature is missing
110   false
111}
112
113#[path = "lib_rand.rs"]
114pub mod rand;
rdseed/lib.rs

rdseed/
lib.rs
