Added duckdb string type

Author: Swoorup

crates/duckdb/src/core/vector.rs

@@ -264,14 +264,11 @@ impl StructVector {
     }
 
     /// Get the name of the child by idx.
-    pub fn child_name(&self, idx: usize) -> String {
+    pub fn child_name(&self, idx: usize) -> DuckDbString {
         let logical_type = self.logical_type();
         unsafe {
             let child_name_ptr = duckdb_struct_type_child_name(logical_type.ptr, idx as u64);
-            let c_str = CString::from_raw(child_name_ptr);
-            let name = c_str.to_str().unwrap();
-            // duckdb_free(child_name_ptr.cast());
-            name.to_string()
+            DuckDbString::from_ptr(child_name_ptr)
         }
     }
 

crates/libduckdb-sys/src/string.rs

@@ -0,0 +1,60 @@
+use std::{
+    ffi::{c_char, CStr},
+    ops::Deref,
+};
+
+use crate::duckdb_free;
+
+pub struct DuckDbString {
+    // Invariant: ptr[0..len+1] is valid C string, i.e. ptr[len] is NUL byte.
+    ptr: core::ptr::NonNull<c_char>,
+    len: usize,
+}
+
+impl DuckDbString {
+    /// Creates a `DuckDbString` from a raw pointer to a C string.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that the pointer is valid and points to a null-terminated C string.
+    /// The memory must remain valid for the lifetime of the returned `DuckDbString`.
+    pub unsafe fn from_ptr(ptr: *const c_char) -> Self {
+        let len = unsafe { CStr::from_ptr(ptr) }.to_bytes().len();
+        unsafe { Self::from_raw_parts(ptr, len) }
+    }
+
+    /// Creates a `DuckDbString` from raw parts.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure that:
+    /// - `ptr` is a valid pointer to a null-terminated C string.
+    /// - `len` accurately represents the length of the string (excluding the null terminator).
+    /// - The memory referenced by `ptr` remains valid for the lifetime of the returned `DuckDbString`.
+    /// - The string data is not mutated for the lifetime of the returned `DuckDbString`.
+    pub unsafe fn from_raw_parts(ptr: *const c_char, len: usize) -> Self {
+        let ptr = unsafe { core::ptr::NonNull::new_unchecked(ptr as *mut c_char) };
+        Self { ptr, len }
+    }
+
+    fn to_bytes_with_nul(&self) -> &[u8] {
+        let ptr = self.ptr.as_ptr() as *const u8;
+        unsafe { core::slice::from_raw_parts(ptr, self.len + 1) }
+    }
+}
+
+impl Deref for DuckDbString {
+    type Target = std::ffi::CStr;
+
+    fn deref(&self) -> &Self::Target {
+        let bytes = self.to_bytes_with_nul();
+        unsafe { CStr::from_bytes_with_nul_unchecked(bytes) }
+    }
+}
+
+impl Drop for DuckDbString {
+    fn drop(&mut self) {
+        let ptr = self.ptr.as_ptr() as *mut core::ffi::c_void;
+        unsafe { duckdb_free(ptr) };
+    }
+}