1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
#include "upbc/message_layout.h"
namespace upbc {
namespace protobuf = ::google::protobuf;
static int64_t DivRoundUp(int64_t a, int64_t b) {
ABSL_ASSERT(a >= 0);
ABSL_ASSERT(b > 0);
return (a + b - 1) / b;
}
MessageLayout::Size MessageLayout::Place(
MessageLayout::SizeAndAlign size_and_align) {
Size offset = size_;
offset.AlignUp(size_and_align.align);
size_ = offset;
size_.Add(size_and_align.size);
//maxalign_.MaxFrom(size_and_align.align);
maxalign_.MaxFrom(size_and_align.size);
return offset;
}
bool MessageLayout::HasHasbit(const protobuf::FieldDescriptor* field) {
return field->file()->syntax() == protobuf::FileDescriptor::SYNTAX_PROTO2 &&
field->label() != protobuf::FieldDescriptor::LABEL_REPEATED &&
!field->containing_oneof();
}
MessageLayout::SizeAndAlign MessageLayout::SizeOf(
const protobuf::FieldDescriptor* field) {
if (field->is_repeated()) {
return {{4, 8}, {4, 8}}; // Pointer to array object.
} else {
return SizeOfUnwrapped(field);
}
}
MessageLayout::SizeAndAlign MessageLayout::SizeOfUnwrapped(
const protobuf::FieldDescriptor* field) {
switch (field->cpp_type()) {
case protobuf::FieldDescriptor::CPPTYPE_MESSAGE:
return {{4, 8}, {4, 8}}; // Pointer to message.
case protobuf::FieldDescriptor::CPPTYPE_STRING:
return {{8, 16}, {4, 8}}; // upb_stringview
case protobuf::FieldDescriptor::CPPTYPE_BOOL:
return {{1, 1}, {1, 1}};
case protobuf::FieldDescriptor::CPPTYPE_FLOAT:
case protobuf::FieldDescriptor::CPPTYPE_INT32:
case protobuf::FieldDescriptor::CPPTYPE_UINT32:
return {{4, 4}, {4, 4}};
default:
return {{8, 8}, {8, 8}};
}
}
int64_t MessageLayout::FieldLayoutRank(const protobuf::FieldDescriptor* field) {
// Order:
// 1, 2, 3. primitive fields (8, 4, 1 byte)
// 4. string fields
// 5. submessage fields
// 6. repeated fields
//
// This has the following nice properties:
//
// 1. padding alignment is (nearly) minimized.
// 2. fields that might have defaults (1-4) are segregated
// from fields that are always zero-initialized (5-7).
//
// We skip oneof fields, because they are emitted in a separate pass.
int64_t rank;
if (field->containing_oneof()) {
fprintf(stderr, "shouldn't have oneofs here.\n");
abort();
} else if (field->label() == protobuf::FieldDescriptor::LABEL_REPEATED) {
rank = 6;
} else {
switch (field->cpp_type()) {
case protobuf::FieldDescriptor::CPPTYPE_MESSAGE:
rank = 5;
break;
case protobuf::FieldDescriptor::CPPTYPE_STRING:
rank = 4;
break;
case protobuf::FieldDescriptor::CPPTYPE_BOOL:
rank = 3;
break;
case protobuf::FieldDescriptor::CPPTYPE_FLOAT:
case protobuf::FieldDescriptor::CPPTYPE_INT32:
case protobuf::FieldDescriptor::CPPTYPE_UINT32:
rank = 2;
break;
default:
rank = 1;
break;
}
}
// Break ties with field number.
return (rank << 29) | field->number();
}
void MessageLayout::ComputeLayout(const protobuf::Descriptor* descriptor) {
size_ = Size{0, 0};
maxalign_ = Size{0, 0};
PlaceNonOneofFields(descriptor);
PlaceOneofFields(descriptor);
// Align overall size up to max size.
size_.AlignUp(maxalign_);
}
void MessageLayout::PlaceNonOneofFields(
const protobuf::Descriptor* descriptor) {
std::vector<const protobuf::FieldDescriptor*> field_order;
for (int i = 0; i < descriptor->field_count(); i++) {
const protobuf::FieldDescriptor* field = descriptor->field(i);
if (!field->containing_oneof()) {
field_order.push_back(descriptor->field(i));
}
}
std::sort(field_order.begin(), field_order.end(),
[](const protobuf::FieldDescriptor* a,
const protobuf::FieldDescriptor* b) {
return FieldLayoutRank(a) < FieldLayoutRank(b);
});
// Place/count hasbits.
int hasbit_count = 0;
for (auto field : field_order) {
if (HasHasbit(field)) {
// We don't use hasbit 0, so that 0 can indicate "no presence" in the
// table. This wastes one hasbit, but we don't worry about it for now.
hasbit_indexes_[field] = ++hasbit_count;
}
}
// Place hasbits at the beginning.
int64_t hasbit_bytes = DivRoundUp(hasbit_count, 8);
Place(SizeAndAlign{{hasbit_bytes, hasbit_bytes}, {1, 1}});
// Place non-oneof fields.
for (auto field : field_order) {
field_offsets_[field] = Place(SizeOf(field));
}
}
void MessageLayout::PlaceOneofFields(const protobuf::Descriptor* descriptor) {
std::vector<const protobuf::OneofDescriptor*> oneof_order;
for (int i = 0; i < descriptor->oneof_decl_count(); i++) {
oneof_order.push_back(descriptor->oneof_decl(i));
}
std::sort(oneof_order.begin(), oneof_order.end(),
[](const protobuf::OneofDescriptor* a,
const protobuf::OneofDescriptor* b) {
return a->full_name() < b->full_name();
});
for (auto oneof : oneof_order) {
SizeAndAlign oneof_maxsize{{0, 0}, {0, 0}};
// Calculate max size.
for (int i = 0; i < oneof->field_count(); i++) {
oneof_maxsize.MaxFrom(SizeOf(oneof->field(i)));
}
// Place discriminator enum and data.
Size data = Place(oneof_maxsize);
Size discriminator = Place(SizeAndAlign{{4, 4}, {4, 4}});
oneof_case_offsets_[oneof] = discriminator;
for (int i = 0; i < oneof->field_count(); i++) {
field_offsets_[oneof->field(i)] = data;
}
}
}
} // namespace upbc
|
