forked from BigfootDev/flatbuffers
3c54fd964b
This is a port of FlatBuffers to Rust. It provides code generation and a runtime library derived from the C++ implementation. It utilizes the Rust type system to provide safe and fast traversal of FlatBuffers data. There are 188 tests, including many fuzz tests of roundtrips for various serialization scenarios. Initial benchmarks indicate that the canonical example payload can be written in ~700ns, and traversed in ~100ns. Rustaceans may be interested in the Follow, Push, and SafeSliceAccess traits. These traits lift traversals, reads, writes, and slice accesses into the type system, providing abstraction with no runtime penalty.
96 lines
2.9 KiB
Rust
96 lines
2.9 KiB
Rust
/*
|
|
* 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 endian_scalar::read_scalar_at;
|
|
use follow::Follow;
|
|
use primitives::*;
|
|
|
|
/// VTable encapsulates read-only usage of a vtable. It is only to be used
|
|
/// by generated code.
|
|
#[derive(Debug)]
|
|
pub struct VTable<'a> {
|
|
buf: &'a [u8],
|
|
loc: usize,
|
|
}
|
|
|
|
impl<'a> PartialEq for VTable<'a> {
|
|
fn eq(&self, other: &VTable) -> bool {
|
|
self.as_bytes().eq(other.as_bytes())
|
|
}
|
|
}
|
|
|
|
impl<'a> VTable<'a> {
|
|
pub fn init(buf: &'a [u8], loc: usize) -> Self {
|
|
VTable {
|
|
buf: buf,
|
|
loc: loc,
|
|
}
|
|
}
|
|
pub fn num_fields(&self) -> usize {
|
|
(self.num_bytes() / SIZE_VOFFSET) - 2
|
|
}
|
|
pub fn num_bytes(&self) -> usize {
|
|
read_scalar_at::<VOffsetT>(self.buf, self.loc) as usize
|
|
}
|
|
pub fn object_inline_num_bytes(&self) -> usize {
|
|
let n = read_scalar_at::<VOffsetT>(self.buf, self.loc + SIZE_VOFFSET);
|
|
n as usize
|
|
}
|
|
pub fn get_field(&self, idx: usize) -> VOffsetT {
|
|
// TODO(rw): distinguish between None and 0?
|
|
if idx > self.num_fields() {
|
|
return 0;
|
|
}
|
|
read_scalar_at::<VOffsetT>(
|
|
self.buf,
|
|
self.loc + SIZE_VOFFSET + SIZE_VOFFSET + SIZE_VOFFSET * idx,
|
|
)
|
|
}
|
|
pub fn get(&self, byte_loc: VOffsetT) -> VOffsetT {
|
|
// TODO(rw): distinguish between None and 0?
|
|
if byte_loc as usize >= self.num_bytes() {
|
|
return 0;
|
|
}
|
|
read_scalar_at::<VOffsetT>(self.buf, self.loc + byte_loc as usize)
|
|
}
|
|
pub fn as_bytes(&self) -> &[u8] {
|
|
let len = self.num_bytes();
|
|
&self.buf[self.loc..self.loc + len]
|
|
}
|
|
}
|
|
|
|
|
|
#[allow(dead_code)]
|
|
pub fn field_index_to_field_offset(field_id: VOffsetT) -> VOffsetT {
|
|
// Should correspond to what end_table() below builds up.
|
|
let fixed_fields = 2; // Vtable size and Object Size.
|
|
((field_id + fixed_fields) * (SIZE_VOFFSET as VOffsetT)) as VOffsetT
|
|
}
|
|
|
|
#[allow(dead_code)]
|
|
pub fn field_offset_to_field_index(field_o: VOffsetT) -> VOffsetT {
|
|
debug_assert!(field_o >= 2);
|
|
let fixed_fields = 2; // VTable size and Object Size.
|
|
(field_o / (SIZE_VOFFSET as VOffsetT)) - fixed_fields
|
|
}
|
|
|
|
impl<'a> Follow<'a> for VTable<'a> {
|
|
type Inner = VTable<'a>;
|
|
fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
|
|
VTable::init(buf, loc)
|
|
}
|
|
}
|