1 /*
2 * Copyright (C) 2022 The Android Open Source Project
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 #ifndef INCLUDE_PERFETTO_PUBLIC_PB_UTILS_H_
18 #define INCLUDE_PERFETTO_PUBLIC_PB_UTILS_H_
19
20 #include <assert.h>
21 #include <stdint.h>
22 #include <string.h>
23
24 #include "perfetto/public/compiler.h"
25
26 // Type of fields that can be found in a protobuf serialized message.
27 enum PerfettoPbWireType {
28 PERFETTO_PB_WIRE_TYPE_VARINT = 0,
29 PERFETTO_PB_WIRE_TYPE_FIXED64 = 1,
30 PERFETTO_PB_WIRE_TYPE_DELIMITED = 2,
31 PERFETTO_PB_WIRE_TYPE_FIXED32 = 5,
32 };
33
34 // Creates a field tag, which encodes the field type and the field id.
PerfettoPbMakeTag(int32_t field_id,enum PerfettoPbWireType wire_type)35 static inline uint32_t PerfettoPbMakeTag(int32_t field_id,
36 enum PerfettoPbWireType wire_type) {
37 return ((PERFETTO_STATIC_CAST(uint32_t, field_id)) << 3) |
38 PERFETTO_STATIC_CAST(uint32_t, wire_type);
39 }
40
41 enum {
42 // Maximum bytes size of a 64-bit integer encoded as a VarInt.
43 PERFETTO_PB_VARINT_MAX_SIZE_64 = 10,
44 // Maximum bytes size of a 32-bit integer encoded as a VarInt.
45 PERFETTO_PB_VARINT_MAX_SIZE_32 = 5,
46 };
47
48 // Encodes `value` as a VarInt into `*dst`.
49 //
50 // `dst` must point into a buffer big enough to represent `value`:
51 // PERFETTO_PB_VARINT_MAX_SIZE_* can help.
PerfettoPbWriteVarInt(uint64_t value,uint8_t * dst)52 static inline uint8_t* PerfettoPbWriteVarInt(uint64_t value, uint8_t* dst) {
53 uint8_t byte;
54 while (value >= 0x80) {
55 byte = (value & 0x7f) | 0x80;
56 *dst++ = byte;
57 value >>= 7;
58 }
59 byte = value & 0x7f;
60 *dst++ = byte;
61
62 return dst;
63 }
64
65 // Encodes `value` as a fixed32 (little endian) into `*dst`.
66 //
67 // `dst` must point into a buffer with at least 4 bytes of space.
PerfettoPbWriteFixed32(uint32_t value,uint8_t * buf)68 static inline uint8_t* PerfettoPbWriteFixed32(uint32_t value, uint8_t* buf) {
69 buf[0] = PERFETTO_STATIC_CAST(uint8_t, value);
70 buf[1] = PERFETTO_STATIC_CAST(uint8_t, value >> 8);
71 buf[2] = PERFETTO_STATIC_CAST(uint8_t, value >> 16);
72 buf[3] = PERFETTO_STATIC_CAST(uint8_t, value >> 24);
73 return buf + 4;
74 }
75
76 // Encodes `value` as a fixed32 (little endian) into `*dst`.
77 //
78 // `dst` must point into a buffer with at least 8 bytes of space.
PerfettoPbWriteFixed64(uint64_t value,uint8_t * buf)79 static inline uint8_t* PerfettoPbWriteFixed64(uint64_t value, uint8_t* buf) {
80 buf[0] = PERFETTO_STATIC_CAST(uint8_t, value);
81 buf[1] = PERFETTO_STATIC_CAST(uint8_t, value >> 8);
82 buf[2] = PERFETTO_STATIC_CAST(uint8_t, value >> 16);
83 buf[3] = PERFETTO_STATIC_CAST(uint8_t, value >> 24);
84 buf[4] = PERFETTO_STATIC_CAST(uint8_t, value >> 32);
85 buf[5] = PERFETTO_STATIC_CAST(uint8_t, value >> 40);
86 buf[6] = PERFETTO_STATIC_CAST(uint8_t, value >> 48);
87 buf[7] = PERFETTO_STATIC_CAST(uint8_t, value >> 56);
88 return buf + 8;
89 }
90
91 // Parses a VarInt from the encoded buffer [start, end). |end| is STL-style and
92 // points one byte past the end of buffer.
93 // The parsed int value is stored in the output arg |value|. Returns a pointer
94 // to the next unconsumed byte (so start < retval <= end) or |start| if the
95 // VarInt could not be fully parsed because there was not enough space in the
96 // buffer.
PerfettoPbParseVarInt(const uint8_t * start,const uint8_t * end,uint64_t * out_value)97 static inline const uint8_t* PerfettoPbParseVarInt(const uint8_t* start,
98 const uint8_t* end,
99 uint64_t* out_value) {
100 const uint8_t* pos = start;
101 uint64_t value = 0;
102 for (uint32_t shift = 0; pos < end && shift < 64u; shift += 7) {
103 // Cache *pos into |cur_byte| to prevent that the compiler dereferences the
104 // pointer twice (here and in the if() below) due to char* aliasing rules.
105 uint8_t cur_byte = *pos++;
106 value |= PERFETTO_STATIC_CAST(uint64_t, cur_byte & 0x7f) << shift;
107 if ((cur_byte & 0x80) == 0) {
108 // In valid cases we get here.
109 *out_value = value;
110 return pos;
111 }
112 }
113 *out_value = 0;
114 return start;
115 }
116
PerfettoPbZigZagEncode32(int32_t value)117 static inline uint32_t PerfettoPbZigZagEncode32(int32_t value) {
118 #if defined(__cplusplus) || \
119 (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L)
120 // Right-shift of negative values is implementation specific.
121 // Assert the implementation does what we expect, which is that shifting an
122 // positive int32_t by 31 gives an all 0 bitmap, and a negative int32_t gives
123 // an all 1 bitmap.
124 static_assert(
125 PERFETTO_STATIC_CAST(uint32_t, INT32_C(-1) >> 31) == ~UINT32_C(0),
126 "implementation does not support assumed rightshift");
127 static_assert(PERFETTO_STATIC_CAST(uint32_t, INT32_C(1) >> 31) == UINT32_C(0),
128 "implementation does not support assumed rightshift");
129 #endif
130
131 return (PERFETTO_STATIC_CAST(uint32_t, value) << 1) ^
132 PERFETTO_STATIC_CAST(uint32_t, value >> 31);
133 }
134
PerfettoPbZigZagEncode64(int64_t value)135 static inline uint64_t PerfettoPbZigZagEncode64(int64_t value) {
136 #if defined(__cplusplus) || \
137 (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L)
138 // Right-shift of negative values is implementation specific.
139 // Assert the implementation does what we expect, which is that shifting an
140 // positive int64_t by 63 gives an all 0 bitmap, and a negative int64_t gives
141 // an all 1 bitmap.
142 static_assert(
143 PERFETTO_STATIC_CAST(uint64_t, INT64_C(-1) >> 63) == ~UINT64_C(0),
144 "implementation does not support assumed rightshift");
145 static_assert(PERFETTO_STATIC_CAST(uint64_t, INT64_C(1) >> 63) == UINT64_C(0),
146 "implementation does not support assumed rightshift");
147 #endif
148
149 return (PERFETTO_STATIC_CAST(uint64_t, value) << 1) ^
150 PERFETTO_STATIC_CAST(uint64_t, value >> 63);
151 }
152
PerfettoPbZigZagDecode32(uint32_t value)153 static inline int32_t PerfettoPbZigZagDecode32(uint32_t value) {
154 uint32_t mask =
155 PERFETTO_STATIC_CAST(uint32_t, -PERFETTO_STATIC_CAST(int32_t, value & 1));
156 return PERFETTO_STATIC_CAST(int32_t, ((value >> 1) ^ mask));
157 }
158
PerfettoPbZigZagDecode64(uint64_t value)159 static inline int64_t PerfettoPbZigZagDecode64(uint64_t value) {
160 uint64_t mask =
161 PERFETTO_STATIC_CAST(uint64_t, -PERFETTO_STATIC_CAST(int64_t, value & 1));
162 return PERFETTO_STATIC_CAST(int64_t, ((value >> 1) ^ mask));
163 }
164
PerfettoPbDoubleToFixed64(double value)165 static inline uint64_t PerfettoPbDoubleToFixed64(double value) {
166 uint64_t val;
167 memcpy(&val, &value, sizeof val);
168 return val;
169 }
170
PerfettoPbFloatToFixed32(float value)171 static inline uint32_t PerfettoPbFloatToFixed32(float value) {
172 uint32_t val;
173 memcpy(&val, &value, sizeof val);
174 return val;
175 }
176
177 #endif // INCLUDE_PERFETTO_PUBLIC_PB_UTILS_H_
178