aya: preallocate the vector

This code badly needs tests :(

aya/src/programs/uprobe.rs

@@ -337,8 +337,8 @@ impl LdSoCache {
             0
         };
 
-        let mut entries = Vec::new();
-        for _ in 0..num_entries {
+        let entries = (0..num_entries)
+            .map(|_: u32| {
                 let flags = read_i32(&mut cursor)?;
                 let k_pos = read_u32(&mut cursor)? as usize;
                 let v_pos = read_u32(&mut cursor)? as usize;
@@ -347,23 +347,24 @@ impl LdSoCache {
                     cursor.consume(12);
                 }
 
-            let key = unsafe {
-                CStr::from_ptr(cursor.get_ref()[offset + k_pos..].as_ptr() as *const c_char)
+                let read_str = |pos| {
+                    unsafe {
+                        CStr::from_ptr(cursor.get_ref()[offset + pos..].as_ptr() as *const c_char)
                     }
                     .to_string_lossy()
-            .into_owned();
-            let value = unsafe {
-                CStr::from_ptr(cursor.get_ref()[offset + v_pos..].as_ptr() as *const c_char)
-            }
-            .to_string_lossy()
-            .into_owned();
+                    .into_owned()
+                };
+
+                let key = read_str(k_pos);
+                let value = read_str(v_pos);
 
-            entries.push(CacheEntry {
+                Ok::<_, io::Error>(CacheEntry {
                     key,
                     value,
                     _flags: flags,
-            });
-        }
+                })
+            })
+            .collect::<Result<_, _>>()?;
 
         Ok(LdSoCache { entries })
     }