Add memchr

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## Unreleased
 
-* None
+* [#26] - Add `memchr` 
 
 ## v0.4.0 (2024-03-22)
 

Cargo.toml

@@ -43,6 +43,7 @@ all = [
     "isdigit",
     "isalpha",
     "isupper",
+    "memchr",
 ]
 abs = []
 strcmp = []
@@ -68,5 +69,6 @@ isdigit = []
 isalpha = []
 isupper = []
 alloc = []
+memchr = []
 signal = ["dep:portable-atomic"]
 signal-cs = ["portable-atomic/critical-section"]

README.md

@@ -15,6 +15,7 @@ This crate basically came about so that the [nrfxlib](https://github.com/NordicP
 * isdigit
 * isalpha
 * isupper
+* memchr
 * strcmp
 * strncmp
 * strncasecmp

src/lib.rs

@@ -87,6 +87,11 @@ mod signal;
 #[cfg(feature = "signal")]
 pub use self::signal::{abort, raise, signal};
 
+#[cfg(feature = "memchr")]
+mod memchr;
+#[cfg(feature = "memchr")]
+pub use self::memchr::memchr;
+
 mod snprintf;
 
 mod ctype;

src/memchr.rs

@@ -0,0 +1,45 @@
+//! Rust implementation of C library function `memchr`
+//!
+//! Licensed under the Blue Oak Model Licence 1.0.0
+
+use crate::{CChar, CInt, CSizeT, CVoid};
+
+/// Rust implementation of C library function `memchr`
+#[cfg_attr(feature = "memchr", no_mangle)]
+pub unsafe extern "C" fn memchr(s: *const CVoid, c: CInt, n: CSizeT) -> *const CVoid {
+	let s = s as *const CChar;
+	for i in 0..n {
+		if *s.add(i) as CInt == c {
+			return s.add(i) as *const CVoid;
+		}
+	}
+	core::ptr::null()
+}
+
+#[cfg(test)]
+mod test {
+	use super::*;
+
+	#[test]
+	fn null() {
+		unsafe { assert_eq!(memchr(core::ptr::null(), 0, 0), core::ptr::null()) };
+	}
+
+	#[test]
+	fn normal() {
+		let s = b"hello world";
+		assert_eq!(
+			unsafe { memchr(s.as_ptr() as *const CVoid, b'w' as CInt, s.len() as CSizeT) },
+			unsafe { s.as_ptr().offset(6) } as *const CVoid
+		);
+	}
+
+	#[test]
+	fn not_found() {
+		let s = b"hello world";
+		assert_eq!(
+			unsafe { memchr(s.as_ptr() as *const CVoid, b'x' as CInt, s.len() as CSizeT) },
+			core::ptr::null()
+		)
+	}
+}