Add more to the Utf8CStr family

Better C strings with path operations

native/src/core/daemon.rs

@@ -3,7 +3,7 @@ use std::fs::File;
 use std::io;
 use std::sync::{Mutex, OnceLock};
 
-use base::{copy_str, cstr, Directory, ResultExt, Utf8CStr, WalkResult};
+use base::{cstr, Directory, ResultExt, Utf8CStr, Utf8CStrBuf, Utf8CStrSlice, WalkResult};
 
 use crate::logging::{magisk_logging, zygisk_logging};
 
@@ -36,8 +36,7 @@ impl MagiskD {}
 
 pub fn find_apk_path(pkg: &[u8], data: &mut [u8]) -> usize {
     use WalkResult::*;
-    fn inner(pkg: &[u8], data: &mut [u8]) -> io::Result<usize> {
-        let mut len = 0_usize;
+    fn inner(pkg: &[u8], buf: &mut dyn Utf8CStrBuf) -> io::Result<usize> {
         let pkg = match Utf8CStr::from_bytes(pkg) {
             Ok(pkg) => pkg,
             Err(e) => return Err(io::Error::new(io::ErrorKind::Other, e)),
@@ -49,7 +48,7 @@ pub fn find_apk_path(pkg: &[u8], data: &mut [u8]) -> usize {
             let d_name = e.d_name().to_bytes();
             if d_name.starts_with(pkg.as_bytes()) && d_name[pkg.len()] == b'-' {
                 // Found the APK path, we can abort now
-                len = e.path(data)?;
+                e.path(buf)?;
                 return Ok(Abort);
             }
             if d_name.starts_with(b"~~") {
@@ -57,10 +56,12 @@ pub fn find_apk_path(pkg: &[u8], data: &mut [u8]) -> usize {
             }
             Ok(Skip)
         })?;
-        if len > 0 {
-            len += copy_str(&mut data[len..], "/base.apk");
+        if !buf.is_empty() {
+            buf.append("/base.apk");
         }
-        Ok(len)
+        Ok(buf.len())
     }
-    inner(pkg, data).log().unwrap_or(0)
+    inner(pkg, &mut Utf8CStrSlice::from(data))
+        .log()
+        .unwrap_or(0)
 }