Merge pull request #1 from Muon/master

This PR fixes several bugs and adds support for missing features to the flatbuffers and flatbuffers_reflection crates.

* fixes #8550
* fixes #8548
* adds reflection support for vectors of values of unknown type
* adds verification support for vectors of unions
* makes the unsafe get_field_* functions infallible as their success is implied by the unsafe precondition
* adds the unsafe function Vector::cast() for casting between vector types
* exposes get_type_size()
* adds Struct::bytes() to get a slice to a byte buffer which starts with the struct value

Author: Muon

rust/flatbuffers/src/lib.rs

@@ -56,8 +56,8 @@ pub use crate::push::{Push, PushAlignment};
 pub use crate::table::{buffer_has_identifier, Table};
 pub use crate::vector::{follow_cast_ref, Vector, VectorIter};
 pub use crate::verifier::{
-    ErrorTraceDetail, InvalidFlatbuffer, SimpleToVerifyInSlice, TableVerifier, Verifiable, Verifier,
-    VerifierOptions,
+    ErrorTraceDetail, InvalidFlatbuffer, SimpleToVerifyInSlice, TableVerifier, Verifiable,
+    Verifier, VerifierOptions,
 };
 pub use crate::vtable::field_index_to_field_offset;
 pub use bitflags;

rust/flatbuffers/src/vector.rs

@@ -90,6 +90,14 @@ impl<'a, T: 'a> Vector<'a, T> {
         let len = self.len();
         &self.0[self.1 + SIZE_UOFFSET..self.1 + SIZE_UOFFSET + sz * len]
     }
+
+    /// # Safety
+    ///
+    /// The underlying bytes must be interpretable as a vector of the *same number* of `U`'s.
+    #[inline(always)]
+    pub unsafe fn cast<U: 'a>(&self) -> Vector<'a, U> {
+        Vector::new(self.0, self.1)
+    }
 }
 
 impl<'a, T: Follow<'a> + 'a> Vector<'a, T> {
@@ -123,11 +131,11 @@ impl<'a, T: Follow<'a> + 'a> Vector<'a, T> {
                 Ordering::Equal => return Some(value),
                 Ordering::Less => left = mid + 1,
                 Ordering::Greater => {
-                  if mid == 0 {
-                    return None;
-                  }
-                  right = mid - 1;
-                },
+                    if mid == 0 {
+                        return None;
+                    }
+                    right = mid - 1;
+                }
             }
         }
 

rust/flatbuffers/src/verifier.rs

@@ -560,7 +560,10 @@ impl<'ver, 'opts, 'buf> TableVerifier<'ver, 'opts, 'buf> {
                 )?;
                 Ok(self)
             }
-            _ => InvalidFlatbuffer::new_inconsistent_union(key_field_name.into(), val_field_name.into()),
+            _ => InvalidFlatbuffer::new_inconsistent_union(
+                key_field_name.into(),
+                val_field_name.into(),
+            ),
         }
     }
     pub fn finish(self) -> &'ver mut Verifier<'opts, 'buf> {

rust/reflection/src/lib.rs

@@ -16,7 +16,9 @@
 
 mod reflection_generated;
 mod reflection_verifier;
-mod safe_buffer;
+pub mod safe_buffer;
+mod vector_of_any;
+pub use vector_of_any::VectorOfAny;
 mod r#struct;
 pub use crate::r#struct::Struct;
 pub use crate::reflection_generated::reflection;
@@ -50,8 +52,12 @@ pub enum FlatbufferError {
     SetStringPolluted,
     #[error("Invalid schema: Polluted buffer or the schema doesn't match the buffer.")]
     InvalidSchema,
-    #[error("Type not supported: {0}")]
-    TypeNotSupported(String),
+    #[error("Unsupported table field type: {0:?}")]
+    UnsupportedTableFieldType(BaseType),
+    #[error("Unsupported vector element type: {0:?}")]
+    UnsupportedVectorElementType(BaseType),
+    #[error("Unsupported union element type: {0:?}")]
+    UnsupportedUnionElementType(BaseType),
     #[error("No type or invalid type found in union enum")]
     InvalidUnionEnum,
     #[error("Table or Struct doesn't belong to the buffer")]
@@ -80,21 +86,17 @@ pub unsafe fn get_any_root(data: &[u8]) -> Table {
 pub unsafe fn get_field_integer<T: for<'a> Follow<'a, Inner = T> + PrimInt + FromPrimitive>(
     table: &Table,
     field: &Field,
-) -> FlatbufferResult<Option<T>> {
-    if size_of::<T>() != get_type_size(field.type_().base_type()) {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            std::any::type_name::<T>().to_string(),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
+) -> Option<T> {
+    debug_assert_eq!(
+        size_of::<T>(),
+        get_type_size(field.type_().base_type()),
+        "Type size mismatch: {} vs {}",
+        std::any::type_name::<T>(),
+        field.type_().base_type().variant_name().unwrap_or_default()
+    );
 
     let default = T::from_i64(field.default_integer());
-    Ok(table.get::<T>(field.offset(), default))
+    table.get::<T>(field.offset(), default)
 }
 
 /// Gets a floating point table field given its exact type. Returns default float value if the field is not set. Returns [None] if no default value is found. Returns error if the type doesn't match.
@@ -105,121 +107,98 @@ pub unsafe fn get_field_integer<T: for<'a> Follow<'a, Inner = T> + PrimInt + Fro
 pub unsafe fn get_field_float<T: for<'a> Follow<'a, Inner = T> + Float>(
     table: &Table,
     field: &Field,
-) -> FlatbufferResult<Option<T>> {
-    if size_of::<T>() != get_type_size(field.type_().base_type()) {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            std::any::type_name::<T>().to_string(),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
+) -> Option<T> {
+    debug_assert_eq!(
+        size_of::<T>(),
+        get_type_size(field.type_().base_type()),
+        "Type size mismatch: {} vs {}",
+        std::any::type_name::<T>(),
+        field.type_().base_type().variant_name().unwrap_or_default()
+    );
 
     let default = T::from(field.default_real());
-    Ok(table.get::<T>(field.offset(), default))
+    table.get::<T>(field.offset(), default)
 }
 
 /// Gets a String table field given its exact type. Returns empty string if the field is not set. Returns [None] if no default value is found. Returns error if the type size doesn't match.
 ///
 /// # Safety
 ///
 /// The value of the corresponding slot must have type String
-pub unsafe fn get_field_string<'a>(
-    table: &Table<'a>,
-    field: &Field,
-) -> FlatbufferResult<Option<&'a str>> {
-    if field.type_().base_type() != BaseType::String {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            String::from("String"),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
-
-    Ok(table.get::<ForwardsUOffset<&'a str>>(field.offset(), Some("")))
+pub unsafe fn get_field_string<'a>(table: &Table<'a>, field: &Field) -> &'a str {
+    debug_assert_eq!(field.type_().base_type(), BaseType::String);
+    table
+        .get::<ForwardsUOffset<&'a str>>(field.offset(), Some(""))
+        .unwrap()
 }
 
-/// Gets a [Struct] table field given its exact type. Returns [None] if the field is not set. Returns error if the type doesn't match.
+/// Gets a [Struct] table field given its exact type. Returns [None] if the field is not set.
 ///
 /// # Safety
 ///
 /// The value of the corresponding slot must have type Struct
-pub unsafe fn get_field_struct<'a>(
-    table: &Table<'a>,
-    field: &Field,
-) -> FlatbufferResult<Option<Struct<'a>>> {
+pub unsafe fn get_field_struct<'a>(table: &Table<'a>, field: &Field) -> Option<Struct<'a>> {
     // TODO inherited from C++: This does NOT check if the field is a table or struct, but we'd need
     // access to the schema to check the is_struct flag.
-    if field.type_().base_type() != BaseType::Obj {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            String::from("Obj"),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
+    debug_assert_eq!(field.type_().base_type(), BaseType::Obj);
 
-    Ok(table.get::<Struct>(field.offset(), None))
+    table.get::<Struct>(field.offset(), None)
 }
 
-/// Gets a Vector table field given its exact type. Returns empty vector if the field is not set. Returns error if the type doesn't match.
+/// Get a vector table field, whose elements have type `T`.
+///
+/// Returns an empty vector if the field is not set.
+///
+/// Non-scalar values such as tables or strings are not stored inline. In such cases, you should use
+/// `ForwardsUOffset`. So for example, use `T = ForwardsUOffset<Table<'a>>` for a vector of tables,
+/// or `T = ForwardsUOffset<&'a str>` for a vector of strings.
 ///
 /// # Safety
 ///
-/// The value of the corresponding slot must have type Vector
-pub unsafe fn get_field_vector<'a, T: Follow<'a, Inner = T>>(
+/// The value of the corresponding slot must be a vector of elements of type `T` which are stored
+/// inline.
+pub unsafe fn get_field_vector<'a, T: Follow<'a>>(
     table: &Table<'a>,
     field: &Field,
-) -> FlatbufferResult<Option<Vector<'a, T>>> {
-    if field.type_().base_type() != BaseType::Vector
-        || core::mem::size_of::<T>() != get_type_size(field.type_().element())
-    {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            std::any::type_name::<T>().to_string(),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
+) -> Vector<'a, T> {
+    debug_assert_eq!(field.type_().base_type(), BaseType::Vector);
+    if field.type_().element() != BaseType::Obj {
+        // Skip this check in the case that it is a vector of structs, because the struct element's
+        // size cannot be checked on older schema versions without access to the schema.
+        debug_assert_eq!(
+            core::mem::size_of::<T>(),
+            get_type_size(field.type_().element())
+        );
     }
 
-    Ok(table.get::<ForwardsUOffset<Vector<'a, T>>>(field.offset(), Some(Vector::<T>::default())))
+    table
+        .get::<ForwardsUOffset<Vector<'a, T>>>(field.offset(), Some(Vector::<T>::default()))
+        .unwrap()
 }
 
-/// Gets a Table table field given its exact type. Returns [None] if the field is not set. Returns error if the type doesn't match.
+/// Get a vector table field, whose elements have unknown type.
+///
+/// Returns an empty vector if the field is not set.
+///
+/// # Safety
+///
+/// The value of the corresponding slot must be a vector of elements of type `T`.
+pub unsafe fn get_field_vector_of_any<'a>(table: &Table<'a>, field: &Field) -> VectorOfAny<'a> {
+    debug_assert_eq!(field.type_().base_type(), BaseType::Vector);
+    table
+        .get::<ForwardsUOffset<VectorOfAny<'a>>>(field.offset(), Some(VectorOfAny::default()))
+        .unwrap()
+}
+
+/// Gets a Table table field given its exact type. Returns [None] if the field is not set.
 ///
 /// # Safety
 ///
 /// The value of the corresponding slot must have type Table
-pub unsafe fn get_field_table<'a>(
-    table: &Table<'a>,
-    field: &Field,
-) -> FlatbufferResult<Option<Table<'a>>> {
-    if field.type_().base_type() != BaseType::Obj {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            String::from("Obj"),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
+pub unsafe fn get_field_table<'a>(table: &Table<'a>, field: &Field) -> Option<Table<'a>> {
+    debug_assert_eq!(field.type_().base_type(), BaseType::Obj);
 
-    Ok(table.get::<ForwardsUOffset<Table<'a>>>(field.offset(), None))
+    table.get::<ForwardsUOffset<Table<'a>>>(field.offset(), None)
 }
 
 /// Returns the value of any table field as a 64-bit int, regardless of what type it is. Returns default integer if the field is not set or error if the value cannot be parsed as integer.
@@ -273,25 +252,12 @@ pub unsafe fn get_any_field_string(table: &Table, field: &Field, schema: &Schema
 /// # Safety
 ///
 /// The value of the corresponding slot must have type Struct.
-pub unsafe fn get_field_struct_in_struct<'a>(
-    st: &Struct<'a>,
-    field: &Field,
-) -> FlatbufferResult<Struct<'a>> {
+pub unsafe fn get_field_struct_in_struct<'a>(st: &Struct<'a>, field: &Field) -> Struct<'a> {
     // TODO inherited from C++: This does NOT check if the field is a table or struct, but we'd need
     // access to the schema to check the is_struct flag.
-    if field.type_().base_type() != BaseType::Obj {
-        return Err(FlatbufferError::FieldTypeMismatch(
-            String::from("Obj"),
-            field
-                .type_()
-                .base_type()
-                .variant_name()
-                .unwrap_or_default()
-                .to_string(),
-        ));
-    }
+    debug_assert_eq!(field.type_().base_type(), BaseType::Obj);
 
-    Ok(st.get::<Struct>(field.offset() as usize))
+    st.get::<Struct>(field.offset() as usize)
 }
 
 /// Returns the value of any struct field as a 64-bit int, regardless of what type it is. Returns error if the value cannot be parsed as integer.
@@ -576,7 +542,7 @@ pub unsafe fn set_string(
 }
 
 /// Returns the size of a scalar type in the `BaseType` enum. In the case of structs, returns the size of their offset (`UOffsetT`) in the buffer.
-fn get_type_size(base_type: BaseType) -> usize {
+pub fn get_type_size(base_type: BaseType) -> usize {
     match base_type {
         BaseType::UType | BaseType::Bool | BaseType::Byte | BaseType::UByte => 1,
         BaseType::Short | BaseType::UShort => 2,