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/endian_scalar.rs b/rust/flatbuffers/src/endian_scalar.rs
new file mode 100644
index 0000000..df0b384
--- /dev/null
+++ b/rust/flatbuffers/src/endian_scalar.rs
@@ -0,0 +1,179 @@
+/*
+ * 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::mem::size_of;
+
+/// Trait for values that must be stored in little-endian byte order, but
+/// might be represented in memory as big-endian. Every type that implements
+/// EndianScalar is a valid FlatBuffers scalar value.
+///
+/// The Rust stdlib does not provide a trait to represent scalars, so this trait
+/// serves that purpose, too.
+///
+/// Note that we do not use the num-traits crate for this, because it provides
+/// "too much". For example, num-traits provides i128 support, but that is an
+/// invalid FlatBuffers type.
+pub trait EndianScalar: Sized + PartialEq + Copy + Clone {
+ fn to_little_endian(self) -> Self;
+ fn from_little_endian(self) -> Self;
+}
+
+/// Macro for implementing a no-op endian conversion. This is used for types
+/// that are one byte wide.
+macro_rules! impl_endian_scalar_noop {
+ ($ty:ident) => {
+ impl EndianScalar for $ty {
+ #[inline]
+ fn to_little_endian(self) -> Self {
+ self
+ }
+ #[inline]
+ fn from_little_endian(self) -> Self {
+ self
+ }
+ }
+ };
+}
+
+/// Macro for implementing an endian conversion using the stdlib `to_le` and
+/// `from_le` functions. This is used for integer types. It is not used for
+/// floats, because the `to_le` and `from_le` are not implemented for them in
+/// the stdlib.
+macro_rules! impl_endian_scalar_stdlib_le_conversion {
+ ($ty:ident) => {
+ impl EndianScalar for $ty {
+ #[inline]
+ fn to_little_endian(self) -> Self {
+ Self::to_le(self)
+ }
+ #[inline]
+ fn from_little_endian(self) -> Self {
+ Self::from_le(self)
+ }
+ }
+ };
+}
+
+impl_endian_scalar_noop!(bool);
+impl_endian_scalar_noop!(u8);
+impl_endian_scalar_noop!(i8);
+
+impl_endian_scalar_stdlib_le_conversion!(u16);
+impl_endian_scalar_stdlib_le_conversion!(u32);
+impl_endian_scalar_stdlib_le_conversion!(u64);
+impl_endian_scalar_stdlib_le_conversion!(i16);
+impl_endian_scalar_stdlib_le_conversion!(i32);
+impl_endian_scalar_stdlib_le_conversion!(i64);
+
+impl EndianScalar for f32 {
+ /// Convert f32 from host endian-ness to little-endian.
+ #[inline]
+ fn to_little_endian(self) -> Self {
+ #[cfg(target_endian = "little")]
+ {
+ self
+ }
+ #[cfg(not(target_endian = "little"))]
+ {
+ byte_swap_f32(self)
+ }
+ }
+ /// Convert f32 from little-endian to host endian-ness.
+ #[inline]
+ fn from_little_endian(self) -> Self {
+ #[cfg(target_endian = "little")]
+ {
+ self
+ }
+ #[cfg(not(target_endian = "little"))]
+ {
+ byte_swap_f32(self)
+ }
+ }
+}
+
+impl EndianScalar for f64 {
+ /// Convert f64 from host endian-ness to little-endian.
+ #[inline]
+ fn to_little_endian(self) -> Self {
+ #[cfg(target_endian = "little")]
+ {
+ self
+ }
+ #[cfg(not(target_endian = "little"))]
+ {
+ byte_swap_f64(self)
+ }
+ }
+ /// Convert f64 from little-endian to host endian-ness.
+ #[inline]
+ fn from_little_endian(self) -> Self {
+ #[cfg(target_endian = "little")]
+ {
+ self
+ }
+ #[cfg(not(target_endian = "little"))]
+ {
+ byte_swap_f64(self)
+ }
+ }
+}
+
+/// Swaps the bytes of an f32.
+#[allow(dead_code)]
+#[inline]
+pub fn byte_swap_f32(x: f32) -> f32 {
+ f32::from_bits(x.to_bits().swap_bytes())
+}
+
+/// Swaps the bytes of an f64.
+#[allow(dead_code)]
+#[inline]
+pub fn byte_swap_f64(x: f64) -> f64 {
+ f64::from_bits(x.to_bits().swap_bytes())
+}
+
+/// Place an EndianScalar into the provided mutable byte slice. Performs
+/// endian conversion, if necessary.
+#[inline]
+pub fn emplace_scalar<T: EndianScalar>(s: &mut [u8], x: T) {
+ let sz = size_of::<T>();
+ let mut_ptr = (&mut s[..sz]).as_mut_ptr() as *mut T;
+ let val = x.to_little_endian();
+ unsafe {
+ *mut_ptr = val;
+ }
+}
+
+/// Read an EndianScalar from the provided byte slice at the specified location.
+/// Performs endian conversion, if necessary.
+#[inline]
+pub fn read_scalar_at<T: EndianScalar>(s: &[u8], loc: usize) -> T {
+ let buf = &s[loc..loc + size_of::<T>()];
+ read_scalar(buf)
+}
+
+/// Read an EndianScalar from the provided byte slice. Performs endian
+/// conversion, if necessary.
+#[inline]
+pub fn read_scalar<T: EndianScalar>(s: &[u8]) -> T {
+ let sz = size_of::<T>();
+
+ let p = (&s[..sz]).as_ptr() as *const T;
+ let x = unsafe { *p };
+
+ x.from_little_endian()
+}