refactor: resolve c pointers const

Signed-off-by: tison <wander4096@gmail.com>

bindings/c/README.md

@@ -32,13 +32,13 @@ int main()
 
     /* We can read it out, make sure the data is the same */
     opendal_result_read r = opendal_operator_read(op, "/testpath");
-    opendal_bytes* read_bytes = r.data;
+    opendal_bytes read_bytes = r.data;
     assert(r.error == NULL);
-    assert(read_bytes->len == 24);
+    assert(read_bytes.len == 24);
 
     /* Lets print it out */
     for (int i = 0; i < 24; ++i) {
-        printf("%c", read_bytes->data[i]);
+        printf("%c", read_bytes.data[i]);
     }
     printf("\n");
 

bindings/c/examples/basic.c

@@ -42,13 +42,13 @@ int main()
 
     /* We can read it out, make sure the data is the same */
     opendal_result_read r = opendal_operator_read(op, "/testpath");
-    opendal_bytes* read_bytes = r.data;
+    opendal_bytes read_bytes = r.data;
     assert(r.error == NULL);
-    assert(read_bytes->len == 24);
+    assert(read_bytes.len == 24);
 
     /* Lets print it out */
     for (int i = 0; i < 24; ++i) {
-        printf("%c", read_bytes->data[i]);
+        printf("%c", read_bytes.data[i]);
     }
     printf("\n");
 

bindings/c/src/error.rs

@@ -114,18 +114,6 @@ impl opendal_error {
     #[no_mangle]
     pub unsafe extern "C" fn opendal_error_free(ptr: *mut opendal_error) {
         if !ptr.is_null() {
-            let message_ptr = &(*ptr).message;
-            let message_ptr = message_ptr as *const opendal_bytes as *mut opendal_bytes;
-            if !message_ptr.is_null() {
-                let data_mut = (*message_ptr).data as *mut u8;
-                drop(Vec::from_raw_parts(
-                    data_mut,
-                    (*message_ptr).len,
-                    (*message_ptr).len,
-                ));
-            }
-
-            // free the pointer
             drop(Box::from_raw(ptr))
         }
     }

bindings/c/src/operator.rs

@@ -47,7 +47,7 @@ static RUNTIME: Lazy<tokio::runtime::Runtime> = Lazy::new(|| {
 pub struct opendal_operator {
     /// The pointer to the opendal::BlockingOperator in the Rust code.
     /// Only touch this on judging whether it is NULL.
-    inner: *const c_void,
+    inner: *mut c_void,
 }
 
 impl opendal_operator {
@@ -263,8 +263,9 @@ pub unsafe extern "C" fn opendal_operator_write(
 /// opendal_result_read r = opendal_operator_read(op, "testpath");
 /// assert(r.error == NULL);
 ///
-/// opendal_bytes *bytes = r.data;
-/// assert(bytes->len == 13);
+/// opendal_bytes bytes = r.data;
+/// assert(bytes.len == 13);
+/// opendal_bytes_free(bytes);
 /// ```
 ///
 /// # Safety
@@ -286,15 +287,12 @@ pub unsafe extern "C" fn opendal_operator_read(
         .to_str()
         .expect("malformed path");
     match op.deref().read(path) {
-        Ok(d) => {
-            let v = Box::new(opendal_bytes::new(d));
-            opendal_result_read {
-                data: Box::into_raw(v),
-                error: std::ptr::null_mut(),
-            }
-        }
+        Ok(b) => opendal_result_read {
+            data: opendal_bytes::new(b),
+            error: std::ptr::null_mut(),
+        },
         Err(e) => opendal_result_read {
-            data: std::ptr::null_mut(),
+            data: opendal_bytes::empty(),
             error: opendal_error::new(e),
         },
     }

bindings/c/src/result.rs

@@ -49,7 +49,7 @@ pub struct opendal_result_operator_new {
 #[repr(C)]
 pub struct opendal_result_read {
     /// The byte array with length returned by read operations
-    pub data: *mut opendal_bytes,
+    pub data: opendal_bytes,
     /// The error, if ok, it is null
     pub error: *mut opendal_error,
 }

bindings/c/src/types.rs

@@ -31,40 +31,49 @@ use opendal::Buffer;
 #[repr(C)]
 pub struct opendal_bytes {
     /// Pointing to the byte array on heap
-    pub data: *const u8,
+    pub data: *mut u8,
     /// The length of the byte array
     pub len: usize,
     /// The capacity of the byte array
     pub capacity: usize,
 }
 
 impl opendal_bytes {
+    pub(crate) fn empty() -> Self {
+        Self {
+            data: std::ptr::null_mut(),
+            len: 0,
+            capacity: 0,
+        }
+    }
+
     /// Construct a [`opendal_bytes`] from the Rust [`Vec`] of bytes
-    pub(crate) fn new(buf: Buffer) -> Self {
-        let vec = buf.to_vec();
-        let mut buf = std::mem::ManuallyDrop::new(vec);
-        let data = buf.as_mut_ptr();
-        let len = buf.len();
-        let capacity = buf.capacity();
+    pub(crate) fn new(b: Buffer) -> Self {
+        let mut b = std::mem::ManuallyDrop::new(b.to_vec());
         Self {
-            data,
-            len,
-            capacity,
+            data: b.as_mut_ptr(),
+            len: b.len(),
+            capacity: b.capacity(),
         }
     }
 
     /// \brief Frees the heap memory used by the opendal_bytes
     #[no_mangle]
-    pub unsafe extern "C" fn opendal_bytes_free(ptr: *mut opendal_bytes) {
-        if !ptr.is_null() {
-            // transmuting `*const u8` to `*mut u8` is undefined behavior in any cases
-            // however, fields type of `opendal_bytes` is already related to the zig binding
-            // it should be fixed later
-            let _ = Vec::from_raw_parts((*ptr).data as *mut u8, (*ptr).len, (*ptr).capacity);
-            // it is too weird that call `Box::new` outside `opendal_bytes::new` but dealloc it here
-            // also, boxing `opendal_bytes` might not be necessary
-            // `data` points to heap, so `opendal_bytes` could be passed as a stack value
-            let _ = Box::from_raw(ptr);
+    pub unsafe extern "C" fn opendal_bytes_free(bs: opendal_bytes) {
+        if !bs.data.is_null() {
+            drop(Vec::from_raw_parts(bs.data, bs.len, bs.capacity));
+        }
+    }
+}
+
+impl Drop for opendal_bytes {
+    fn drop(&mut self) {
+        if !self.data.is_null() {
+            unsafe {
+                // Safety: the data is not null, and the capacity is correct
+                drop(Vec::from_raw_parts(self.data, self.len, self.capacity));
+            }
+            self.data = std::ptr::null_mut();
         }
     }
 }

bindings/c/tests/bdd.cpp

@@ -85,9 +85,9 @@ TEST_F(OpendalBddTest, FeatureTest)
     // The blocking file "test" must have content "Hello, World!"
     struct opendal_result_read r = opendal_operator_read(this->p, this->path.c_str());
     EXPECT_EQ(r.error, nullptr);
-    EXPECT_EQ(r.data->len, this->content.length());
-    for (int i = 0; i < r.data->len; i++) {
-        EXPECT_EQ(this->content[i], (char)(r.data->data[i]));
+    EXPECT_EQ(r.data.len, this->content.length());
+    for (int i = 0; i < r.data.len; i++) {
+        EXPECT_EQ(this->content[i], (char)(r.data.data[i]));
     }
 
     // The blocking file should be deleted

bindings/go/operator.go

@@ -285,12 +285,12 @@ type bytesFree func(b *opendalBytes)
 var withBytesFree = withFFI(ffiOpts{
 	sym:    symBytesFree,
 	rType:  &ffi.TypeVoid,
-	aTypes: []*ffi.Type{&ffi.TypePointer},
+	aTypes: []*ffi.Type{&typeBytes},
 }, func(_ context.Context, ffiCall func(rValue unsafe.Pointer, aValues ...unsafe.Pointer)) bytesFree {
-	return func(b *opendalBytes) {
+	return func(b opendalBytes) {
 		ffiCall(
 			nil,
-			unsafe.Pointer(&b),
+			b,
 		)
 	}
 })

bindings/go/stat.go

@@ -96,7 +96,6 @@ func (op *Operator) Stat(path string) (*Metadata, error) {
 //	} else {
 //		fmt.Println("The file does not exist")
 //	}
-//
 func (op *Operator) IsExist(path string) (bool, error) {
 	isExist := getFFI[operatorIsExist](op.ctx, symOperatorIsExist)
 	return isExist(op.inner, path)

bindings/swift/OpenDAL/Sources/OpenDAL/Data+OpenDAL.swift

@@ -25,7 +25,7 @@ extension Data {
     /// This can be used to read data from Rust with zero-copying.
     /// The underlying buffer will be freed when the data gets
     /// deallocated.
-    init(openDALBytes: UnsafeMutablePointer<opendal_bytes>) {
+    init(openDALBytes: opendal_bytes) {
         let address = UnsafeRawPointer(openDALBytes.pointee.data)!
         let length = Int(openDALBytes.pointee.len)
         self.init(

bindings/zig/test/bdd.zig

@@ -24,7 +24,7 @@ test "Opendal BDD test" {
     const c_str = [*:0]const u8; // define a type for 'const char*' in C
 
     const OpendalBDDTest = struct {
-        p: [*c]const opendal.c.opendal_operator,
+        p: [*c]opendal.c.opendal_operator,
         scheme: c_str,
         path: c_str,
         content: c_str,
@@ -60,8 +60,8 @@ test "Opendal BDD test" {
     // When Blocking write path "test" with content "Hello, World!"
     const data: opendal.c.opendal_bytes = .{
         .data = testkit.content,
-        // c_str does not have len field (.* is ptr)
         .len = std.mem.len(testkit.content),
+        .capacity = std.mem.len(testkit.content),
     };
     const result = opendal.c.opendal_operator_write(testkit.p, testkit.path, data);
     try testing.expectEqual(result, null);