Fix MSRV

Author: ldm0

Diff for: src/offset/local/tzdata.rs

@@ -5,7 +5,7 @@ use std::{
     ffi::CStr,
     fmt::Debug,
     fs::File,
-    io::{Error, Read, Result, Seek, SeekFrom},
+    io::{Error, ErrorKind, Read, Result, Seek, SeekFrom},
 };
 
 /// Get timezone data from the `tzdata` file of HarmonyOS NEXT.
@@ -34,7 +34,7 @@ fn open_android_tz_data_file() -> Result<File> {
             }
         }
     }
-    Err(std::io::Error::from(std::io::ErrorKind::NotFound))
+    Err(Error::from(ErrorKind::NotFound))
 }
 
 /// Get timezone data from the `tzdata` file reader of HarmonyOS NEXT.
@@ -77,7 +77,7 @@ impl TzDataHeader {
             let mut magic = [0; TZDATA_VERSION_SIZE];
             data.read_exact(&mut magic)?;
             if !magic.starts_with(b"tzdata") || magic[TZDATA_VERSION_SIZE - 1] != 0 {
-                return Err(Error::other("invalid tzdata header magic"));
+                return Err(Error::new(ErrorKind::Other, "invalid tzdata header magic"));
             }
             let mut version = [0; 5];
             version.copy_from_slice(&magic[6..11]);
@@ -118,7 +118,7 @@ impl TzDataIndexes {
             indexes: buf
                 .chunks(INDEX_SIZE)
                 .filter_map(|chunk| {
-                    if let Ok(name) = CStr::from_bytes_until_nul(&chunk[..SIZEOF_TZNAME]) {
+                    if let Some(name) = from_bytes_until_nul(&chunk[..SIZEOF_TZNAME]) {
                         let name = name.to_bytes().to_vec().into_boxed_slice();
                         let offset = u32::from_be_bytes(
                             chunk[SIZEOF_TZNAME..SIZEOF_TZNAME + 4].try_into().unwrap(),
@@ -155,6 +155,15 @@ impl TzDataIndexes {
     }
 }
 
+/// Change this `CStr::from_bytes_until_nul` once MSRV was bumped above 1.72.0
+fn from_bytes_until_nul(bytes: &[u8]) -> Option<&CStr> {
+    let nul_pos = bytes.iter().position(|&b| b == 0)?;
+    // SAFETY:
+    // 1. nul_pos + 1 <= bytes.len()
+    // 2. We know there is a nul byte at nul_pos, so this slice (ending at the nul byte) is a well-formed C string.
+    Some(unsafe { CStr::from_bytes_with_nul_unchecked(&bytes[0..=nul_pos]) })
+}
+
 /// Ohos tzdata index entry size: `name + offset + length`
 #[cfg(any(test, target_env = "ohos"))]
 const SIZEOF_INDEX_OHOS: usize = SIZEOF_TZNAME + 2 * size_of::<u32>();