1 /*
2 * Copyright 2018 Google Inc. All rights reserved.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 use endian_scalar::read_scalar_at;
18 use follow::Follow;
19 use primitives::*;
20
21 /// VTable encapsulates read-only usage of a vtable. It is only to be used
22 /// by generated code.
23 #[derive(Debug)]
24 pub struct VTable<'a> {
25 buf: &'a [u8],
26 loc: usize,
27 }
28
29 impl<'a> PartialEq for VTable<'a> {
eq(&self, other: &VTable) -> bool30 fn eq(&self, other: &VTable) -> bool {
31 self.as_bytes().eq(other.as_bytes())
32 }
33 }
34
35 impl<'a> VTable<'a> {
init(buf: &'a [u8], loc: usize) -> Self36 pub fn init(buf: &'a [u8], loc: usize) -> Self {
37 VTable {
38 buf: buf,
39 loc: loc,
40 }
41 }
num_fields(&self) -> usize42 pub fn num_fields(&self) -> usize {
43 (self.num_bytes() / SIZE_VOFFSET) - 2
44 }
num_bytes(&self) -> usize45 pub fn num_bytes(&self) -> usize {
46 read_scalar_at::<VOffsetT>(self.buf, self.loc) as usize
47 }
object_inline_num_bytes(&self) -> usize48 pub fn object_inline_num_bytes(&self) -> usize {
49 let n = read_scalar_at::<VOffsetT>(self.buf, self.loc + SIZE_VOFFSET);
50 n as usize
51 }
get_field(&self, idx: usize) -> VOffsetT52 pub fn get_field(&self, idx: usize) -> VOffsetT {
53 // TODO(rw): distinguish between None and 0?
54 if idx > self.num_fields() {
55 return 0;
56 }
57 read_scalar_at::<VOffsetT>(
58 self.buf,
59 self.loc + SIZE_VOFFSET + SIZE_VOFFSET + SIZE_VOFFSET * idx,
60 )
61 }
get(&self, byte_loc: VOffsetT) -> VOffsetT62 pub fn get(&self, byte_loc: VOffsetT) -> VOffsetT {
63 // TODO(rw): distinguish between None and 0?
64 if byte_loc as usize >= self.num_bytes() {
65 return 0;
66 }
67 read_scalar_at::<VOffsetT>(self.buf, self.loc + byte_loc as usize)
68 }
as_bytes(&self) -> &[u8]69 pub fn as_bytes(&self) -> &[u8] {
70 let len = self.num_bytes();
71 &self.buf[self.loc..self.loc + len]
72 }
73 }
74
75
76 #[allow(dead_code)]
field_index_to_field_offset(field_id: VOffsetT) -> VOffsetT77 pub fn field_index_to_field_offset(field_id: VOffsetT) -> VOffsetT {
78 // Should correspond to what end_table() below builds up.
79 let fixed_fields = 2; // Vtable size and Object Size.
80 ((field_id + fixed_fields) * (SIZE_VOFFSET as VOffsetT)) as VOffsetT
81 }
82
83 #[allow(dead_code)]
field_offset_to_field_index(field_o: VOffsetT) -> VOffsetT84 pub fn field_offset_to_field_index(field_o: VOffsetT) -> VOffsetT {
85 debug_assert!(field_o >= 2);
86 let fixed_fields = 2; // VTable size and Object Size.
87 (field_o / (SIZE_VOFFSET as VOffsetT)) - fixed_fields
88 }
89
90 impl<'a> Follow<'a> for VTable<'a> {
91 type Inner = VTable<'a>;
follow(buf: &'a [u8], loc: usize) -> Self::Inner92 fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
93 VTable::init(buf, loc)
94 }
95 }
96