Squashed 'third_party/flatbuffers/' content from commit acc9990ab
Change-Id: I48550d40d78fea996ebe74e9723a5d1f910de491
git-subtree-dir: third_party/flatbuffers
git-subtree-split: acc9990abd2206491480291b0f85f925110102ea
diff --git a/rust/flatbuffers/src/vtable_writer.rs b/rust/flatbuffers/src/vtable_writer.rs
new file mode 100644
index 0000000..d1e87dd
--- /dev/null
+++ b/rust/flatbuffers/src/vtable_writer.rs
@@ -0,0 +1,84 @@
+/*
+ * Copyright 2018 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+use std::ptr::write_bytes;
+
+use endian_scalar::{emplace_scalar, read_scalar_at};
+use primitives::*;
+
+/// VTableWriter compartmentalizes actions needed to create a vtable.
+#[derive(Debug)]
+pub struct VTableWriter<'a> {
+ buf: &'a mut [u8],
+}
+
+impl<'a> VTableWriter<'a> {
+ #[inline(always)]
+ pub fn init(buf: &'a mut [u8]) -> Self {
+ VTableWriter { buf: buf }
+ }
+
+ /// Writes the vtable length (in bytes) into the vtable.
+ ///
+ /// Note that callers already need to have computed this to initialize
+ /// a VTableWriter.
+ ///
+ /// In debug mode, asserts that the length of the underlying data is equal
+ /// to the provided value.
+ #[inline(always)]
+ pub fn write_vtable_byte_length(&mut self, n: VOffsetT) {
+ emplace_scalar::<VOffsetT>(&mut self.buf[..SIZE_VOFFSET], n);
+ debug_assert_eq!(n as usize, self.buf.len());
+ }
+
+ /// Writes an object length (in bytes) into the vtable.
+ #[inline(always)]
+ pub fn write_object_inline_size(&mut self, n: VOffsetT) {
+ emplace_scalar::<VOffsetT>(&mut self.buf[SIZE_VOFFSET..2 * SIZE_VOFFSET], n);
+ }
+
+ /// Gets an object field offset from the vtable. Only used for debugging.
+ ///
+ /// Note that this expects field offsets (which are like pointers), not
+ /// field ids (which are like array indices).
+ #[inline(always)]
+ pub fn get_field_offset(&self, vtable_offset: VOffsetT) -> VOffsetT {
+ let idx = vtable_offset as usize;
+ read_scalar_at::<VOffsetT>(&self.buf, idx)
+ }
+
+ /// Writes an object field offset into the vtable.
+ ///
+ /// Note that this expects field offsets (which are like pointers), not
+ /// field ids (which are like array indices).
+ #[inline(always)]
+ pub fn write_field_offset(&mut self, vtable_offset: VOffsetT, object_data_offset: VOffsetT) {
+ let idx = vtable_offset as usize;
+ emplace_scalar::<VOffsetT>(&mut self.buf[idx..idx + SIZE_VOFFSET], object_data_offset);
+ }
+
+ /// Clears all data in this VTableWriter. Used to cleanly undo a
+ /// vtable write.
+ #[inline(always)]
+ pub fn clear(&mut self) {
+ // This is the closest thing to memset in Rust right now.
+ let len = self.buf.len();
+ let p = self.buf.as_mut_ptr() as *mut u8;
+ unsafe {
+ write_bytes(p, 0, len);
+ }
+ }
+}