getrandom/
error.rs

1#[cfg(feature = "std")]
2extern crate std;
3
4use core::{fmt, num::NonZeroU32};
5
6// This private alias mirrors `std::io::RawOsError`:
7// https://doc.rust-lang.org/std/io/type.RawOsError.html)
8cfg_if::cfg_if!(
9    if #[cfg(target_os = "uefi")] {
10        type RawOsError = usize;
11    } else {
12        type RawOsError = i32;
13    }
14);
15
16/// A small and `no_std` compatible error type
17///
18/// The [`Error::raw_os_error()`] will indicate if the error is from the OS, and
19/// if so, which error code the OS gave the application. If such an error is
20/// encountered, please consult with your system documentation.
21///
22/// Internally this type is a NonZeroU32, with certain values reserved for
23/// certain purposes, see [`Error::INTERNAL_START`] and [`Error::CUSTOM_START`].
24///
25/// *If this crate's `"std"` Cargo feature is enabled*, then:
26/// - [`getrandom::Error`][Error] implements
27///   [`std::error::Error`](https://doc.rust-lang.org/std/error/trait.Error.html)
28/// - [`std::io::Error`](https://doc.rust-lang.org/std/io/struct.Error.html) implements
29///   [`From<getrandom::Error>`](https://doc.rust-lang.org/std/convert/trait.From.html).
30#[derive(Copy, Clone, Eq, PartialEq)]
31pub struct Error(NonZeroU32);
32
33impl Error {
34    /// This target/platform is not supported by `getrandom`.
35    pub const UNSUPPORTED: Error = Self::new_internal(0);
36    /// The platform-specific `errno` returned a non-positive value.
37    pub const ERRNO_NOT_POSITIVE: Error = Self::new_internal(1);
38    /// Encountered an unexpected situation which should not happen in practice.
39    pub const UNEXPECTED: Error = Self::new_internal(2);
40
41    /// Codes below this point represent OS Errors (i.e. positive i32 values).
42    /// Codes at or above this point, but below [`Error::CUSTOM_START`] are
43    /// reserved for use by the `rand` and `getrandom` crates.
44    pub const INTERNAL_START: u32 = 1 << 31;
45
46    /// Codes at or above this point can be used by users to define their own
47    /// custom errors.
48    pub const CUSTOM_START: u32 = (1 << 31) + (1 << 30);
49
50    /// Creates a new instance of an `Error` from a particular OS error code.
51    ///
52    /// This method is analogous to [`std::io::Error::from_raw_os_error()`][1],
53    /// except that it works in `no_std` contexts and `code` will be
54    /// replaced with `Error::UNEXPECTED` if it isn't in the range
55    /// `1..Error::INTERNAL_START`. Thus, for the result `r`,
56    /// `r == Self::UNEXPECTED || r.raw_os_error().unsigned_abs() == code`.
57    ///
58    /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.from_raw_os_error
59    #[allow(dead_code)]
60    pub(super) fn from_os_error(code: u32) -> Self {
61        match NonZeroU32::new(code) {
62            Some(code) if code.get() < Self::INTERNAL_START => Self(code),
63            _ => Self::UNEXPECTED,
64        }
65    }
66
67    /// Extract the raw OS error code (if this error came from the OS)
68    ///
69    /// This method is identical to [`std::io::Error::raw_os_error()`][1], except
70    /// that it works in `no_std` contexts. On most targets this method returns
71    /// `Option<i32>`, but some platforms (e.g. UEFI) may use a different primitive
72    /// type like `usize`. Consult with the [`RawOsError`] docs for more information.
73    ///
74    /// If this method returns `None`, the error value can still be formatted via
75    /// the `Display` implementation.
76    ///
77    /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error
78    /// [`RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
79    #[inline]
80    pub fn raw_os_error(self) -> Option<RawOsError> {
81        let code = self.0.get();
82        if code >= Self::INTERNAL_START {
83            return None;
84        }
85        let errno = RawOsError::try_from(code).ok()?;
86        #[cfg(target_os = "solid_asp3")]
87        let errno = -errno;
88        Some(errno)
89    }
90
91    /// Creates a new instance of an `Error` from a particular custom error code.
92    pub const fn new_custom(n: u16) -> Error {
93        // SAFETY: code > 0 as CUSTOM_START > 0 and adding n won't overflow a u32.
94        let code = Error::CUSTOM_START + (n as u32);
95        Error(unsafe { NonZeroU32::new_unchecked(code) })
96    }
97
98    /// Creates a new instance of an `Error` from a particular internal error code.
99    pub(crate) const fn new_internal(n: u16) -> Error {
100        // SAFETY: code > 0 as INTERNAL_START > 0 and adding n won't overflow a u32.
101        let code = Error::INTERNAL_START + (n as u32);
102        Error(unsafe { NonZeroU32::new_unchecked(code) })
103    }
104
105    fn internal_desc(&self) -> Option<&'static str> {
106        let desc = match *self {
107            Error::UNSUPPORTED => "getrandom: this target is not supported",
108            Error::ERRNO_NOT_POSITIVE => "errno: did not return a positive value",
109            Error::UNEXPECTED => "unexpected situation",
110            #[cfg(any(
111                target_os = "ios",
112                target_os = "visionos",
113                target_os = "watchos",
114                target_os = "tvos",
115            ))]
116            Error::IOS_RANDOM_GEN => "SecRandomCopyBytes: iOS Security framework failure",
117            #[cfg(all(windows, target_vendor = "win7"))]
118            Error::WINDOWS_RTL_GEN_RANDOM => "RtlGenRandom: Windows system function failure",
119            #[cfg(all(feature = "wasm_js", getrandom_backend = "wasm_js"))]
120            Error::WEB_CRYPTO => "Web Crypto API is unavailable",
121            #[cfg(target_os = "vxworks")]
122            Error::VXWORKS_RAND_SECURE => "randSecure: VxWorks RNG module is not initialized",
123
124            #[cfg(any(
125                getrandom_backend = "rdrand",
126                all(target_arch = "x86_64", target_env = "sgx")
127            ))]
128            Error::FAILED_RDRAND => "RDRAND: failed multiple times: CPU issue likely",
129            #[cfg(any(
130                getrandom_backend = "rdrand",
131                all(target_arch = "x86_64", target_env = "sgx")
132            ))]
133            Error::NO_RDRAND => "RDRAND: instruction not supported",
134
135            #[cfg(getrandom_backend = "rndr")]
136            Error::RNDR_FAILURE => "RNDR: Could not generate a random number",
137            #[cfg(getrandom_backend = "rndr")]
138            Error::RNDR_NOT_AVAILABLE => "RNDR: Register not supported",
139            _ => return None,
140        };
141        Some(desc)
142    }
143}
144
145impl fmt::Debug for Error {
146    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
147        let mut dbg = f.debug_struct("Error");
148        if let Some(errno) = self.raw_os_error() {
149            dbg.field("os_error", &errno);
150            #[cfg(feature = "std")]
151            dbg.field("description", &std::io::Error::from_raw_os_error(errno));
152        } else if let Some(desc) = self.internal_desc() {
153            dbg.field("internal_code", &self.0.get());
154            dbg.field("description", &desc);
155        } else {
156            dbg.field("unknown_code", &self.0.get());
157        }
158        dbg.finish()
159    }
160}
161
162impl fmt::Display for Error {
163    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
164        if let Some(errno) = self.raw_os_error() {
165            cfg_if! {
166                if #[cfg(feature = "std")] {
167                    std::io::Error::from_raw_os_error(errno).fmt(f)
168                } else {
169                    write!(f, "OS Error: {}", errno)
170                }
171            }
172        } else if let Some(desc) = self.internal_desc() {
173            f.write_str(desc)
174        } else {
175            write!(f, "Unknown Error: {}", self.0.get())
176        }
177    }
178}
179
180#[cfg(test)]
181mod tests {
182    use super::Error;
183    use core::mem::size_of;
184
185    #[test]
186    fn test_size() {
187        assert_eq!(size_of::<Error>(), 4);
188        assert_eq!(size_of::<Result<(), Error>>(), 4);
189    }
190}
getrandom/error.rs

getrandom/
error.rs
