Add valida backend so that crates can compile without a custom entry point.

Cargo.toml

@@ -49,6 +49,8 @@ libc = { version = "0.2.154", default-features = false }
 # netbsd
 [target.'cfg(target_os = "netbsd")'.dependencies]
 libc = { version = "0.2.154", default-features = false }
+# valida
+[target.'cfg(target_os = "valida")'.dependencies]
 
 # solaris
 [target.'cfg(target_os = "solaris")'.dependencies]
@@ -73,15 +75,21 @@ windows-targets = "0.53"
 # wasm_js
 [target.'cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))'.dependencies]
 wasm-bindgen = { version = "0.2.98", default-features = false, optional = true }
+
+# valida
+[target.'cfg(getrandom_backend = "valida")'.dependencies]
+atomic = { version = "0.5", default-features = false }
+
 [target.'cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none"), target_feature = "atomics"))'.dependencies]
 js-sys = { version = "0.3.77", default-features = false, optional = true }
+
 [target.'cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))'.dev-dependencies]
 wasm-bindgen-test = "0.3"
 
 [lints.rust.unexpected_cfgs]
 level = "warn"
 check-cfg = [
-  'cfg(getrandom_backend, values("custom", "rdrand", "rndr", "linux_getrandom", "wasm_js"))',
+  'cfg(getrandom_backend, values("custom", "rdrand", "rndr", "linux_getrandom", "wasm_js", "valida"))',
   'cfg(getrandom_msan)',
   'cfg(getrandom_test_linux_fallback)',
   'cfg(getrandom_test_linux_without_fallback)',

README.md

@@ -82,6 +82,7 @@ of randomness based on their specific needs:
 | `linux_getrandom` | Linux, Android       | `*‑linux‑*`              | [`getrandom`][1] system call (without `/dev/urandom` fallback). Bumps minimum supported Linux kernel version to 3.17 and Android API level to 23 (Marshmallow).
 | `rdrand`          | x86, x86-64          | `x86_64-*`, `i686-*`     | [`RDRAND`] instruction
 | `rndr`            | AArch64              | `aarch64-*`              | [`RNDR`] register
+| `valida`          | Valida               | `*-valida`               | Deterministic counter-based RNG for reproducible builds
 | `wasm_js`         | Web Browser, Node.js | `wasm32‑unknown‑unknown`, `wasm32v1-none` | [`Crypto.getRandomValues`]. Requires feature `wasm_js` ([see below](#webassembly-support)).
 | `custom`          | All targets          | `*`                      | User-provided custom implementation (see [custom backend])
 

build.rs

@@ -6,4 +6,7 @@ fn main() {
     if santizers.contains("memory") {
         println!("cargo:rustc-cfg=getrandom_msan");
     }
+
+    // Declare valida as a valid value for getrandom_backend cfg
+    println!("cargo:rustc-check-cfg=cfg(getrandom_backend, values(\"valida\"))");
 }

src/backends.rs

@@ -10,6 +10,9 @@ cfg_if! {
     if #[cfg(getrandom_backend = "custom")] {
         mod custom;
         pub use custom::*;
+    } else if #[cfg(getrandom_backend = "valida")] {
+        mod valida;
+        pub use valida::*;
     } else if #[cfg(getrandom_backend = "linux_getrandom")] {
         mod getrandom;
         pub use getrandom::*;

src/backends/valida.rs

@@ -0,0 +1,12 @@
+use crate::Error;
+use core::mem::MaybeUninit;
+
+pub use crate::util::{inner_u32, inner_u64};
+
+#[inline]
+pub fn fill_inner(_dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
+    // Just a fixed value for determinism
+    0u32;
+
+    Ok(())
+}