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//! Search for a byte in a byte array using libc.
//!
//! When nothing pulls in libc, then just use a trivial implementation. Note
//! that we only depend on libc on unix.
#[cfg(not(all(unix, feature = "libc")))]
pub(crate) fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
haystack.iter().position(|val| needle == *val)
}
#[cfg(all(unix, feature = "libc"))]
pub(crate) fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> {
let start = haystack.as_ptr();
// SAFETY: `start` is valid for `haystack.len()` bytes.
let ptr = unsafe { libc::memchr(start.cast(), needle as _, haystack.len()) };
if ptr.is_null() {
None
} else {
Some(ptr as usize - start as usize)
}
}
#[cfg(test)]
mod tests {
use super::memchr;
#[test]
fn memchr_test() {
let haystack = b"123abc456\0\xffabc\n";
assert_eq!(memchr(b'1', haystack), Some(0));
assert_eq!(memchr(b'2', haystack), Some(1));
assert_eq!(memchr(b'3', haystack), Some(2));
assert_eq!(memchr(b'4', haystack), Some(6));
assert_eq!(memchr(b'5', haystack), Some(7));
assert_eq!(memchr(b'6', haystack), Some(8));
assert_eq!(memchr(b'7', haystack), None);
assert_eq!(memchr(b'a', haystack), Some(3));
assert_eq!(memchr(b'b', haystack), Some(4));
assert_eq!(memchr(b'c', haystack), Some(5));
assert_eq!(memchr(b'd', haystack), None);
assert_eq!(memchr(b'A', haystack), None);
assert_eq!(memchr(0, haystack), Some(9));
assert_eq!(memchr(0xff, haystack), Some(10));
assert_eq!(memchr(0xfe, haystack), None);
assert_eq!(memchr(1, haystack), None);
assert_eq!(memchr(b'\n', haystack), Some(14));
assert_eq!(memchr(b'\r', haystack), None);
}
#[test]
fn memchr_all() {
let mut arr = Vec::new();
for b in 0..=255 {
arr.push(b);
}
for b in 0..=255 {
assert_eq!(memchr(b, &arr), Some(b as usize));
}
arr.reverse();
for b in 0..=255 {
assert_eq!(memchr(b, &arr), Some(255 - b as usize));
}
}
#[test]
fn memchr_empty() {
for b in 0..=255 {
assert_eq!(memchr(b, b""), None);
}
}
}