/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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.
*/
#include "perfetto/protozero/proto_decoder.h"
#include <string.h>
#include "perfetto/base/logging.h"
#include "perfetto/base/utils.h"
#include "perfetto/protozero/proto_utils.h"
namespace protozero {
using namespace proto_utils;
#if __BYTE_ORDER__ != __ORDER_LITTLE_ENDIAN__
#error Unimplemented for big endian archs.
#endif
namespace {
struct ParseFieldResult {
const uint8_t* next;
Field field;
};
// Parses one field and returns the field itself and a pointer to the next
// field to parse. If parsing fails, the returned |next| == |buffer|.
PERFETTO_ALWAYS_INLINE ParseFieldResult
ParseOneField(const uint8_t* const buffer, const uint8_t* const end) {
ParseFieldResult res{buffer, Field{}};
// The first byte of a proto field is structured as follows:
// The least 3 significant bits determine the field type.
// The most 5 significant bits determine the field id. If MSB == 1, the
// field id continues on the next bytes following the VarInt encoding.
const uint8_t kFieldTypeNumBits = 3;
const uint64_t kFieldTypeMask = (1 << kFieldTypeNumBits) - 1; // 0000 0111;
const uint8_t* pos = buffer;
// If we've already hit the end, just return an invalid field.
if (PERFETTO_UNLIKELY(pos >= end))
return res;
uint64_t preamble = 0;
if (PERFETTO_LIKELY(*pos < 0x80)) { // Fastpath for fields with ID < 32.
preamble = *(pos++);
} else {
pos = ParseVarInt(pos, end, &preamble);
}
uint32_t field_id = static_cast<uint32_t>(preamble >> kFieldTypeNumBits);
if (field_id == 0 || pos >= end)
return res;
auto field_type = static_cast<uint8_t>(preamble & kFieldTypeMask);
const uint8_t* new_pos = pos;
uint64_t int_value = 0;
uint32_t size = 0;
switch (field_type) {
case static_cast<uint8_t>(ProtoWireType::kVarInt): {
new_pos = ParseVarInt(pos, end, &int_value);
// new_pos not being greater than pos means ParseVarInt could not fully
// parse the number. This is because we are out of space in the buffer.
// Set the id to zero and return but don't update the offset so a future
// read can read this field.
if (PERFETTO_UNLIKELY(new_pos == pos))
return res;
break;
}
case static_cast<uint8_t>(ProtoWireType::kLengthDelimited): {
uint64_t payload_length;
new_pos = ParseVarInt(pos, end, &payload_length);
if (PERFETTO_UNLIKELY(new_pos == pos))
return res;
// ParseVarInt guarantees that |new_pos| <= |end| when it succeeds;
if (payload_length > static_cast<uint64_t>(end - new_pos))
return res;
// If the message is larger than 256 MiB silently skip it.
if (PERFETTO_LIKELY(payload_length <= proto_utils::kMaxMessageLength)) {
const uintptr_t payload_start = reinterpret_cast<uintptr_t>(new_pos);
int_value = payload_start;
size = static_cast<uint32_t>(payload_length);
}
new_pos += payload_length;
break;
}
case static_cast<uint8_t>(ProtoWireType::kFixed64): {
new_pos = pos + sizeof(uint64_t);
if (PERFETTO_UNLIKELY(new_pos > end))
return res;
memcpy(&int_value, pos, sizeof(uint64_t));
break;
}
case static_cast<uint8_t>(ProtoWireType::kFixed32): {
new_pos = pos + sizeof(uint32_t);
if (PERFETTO_UNLIKELY(new_pos > end))
return res;
memcpy(&int_value, pos, sizeof(uint32_t));
break;
}
default:
PERFETTO_DLOG("Invalid proto field type: %u", field_type);
return res;
}
if (PERFETTO_UNLIKELY(field_id > std::numeric_limits<uint16_t>::max())) {
PERFETTO_DFATAL("Cannot parse proto field ids > 0xFFFF");
return res;
}
res.field.initialize(static_cast<uint16_t>(field_id), field_type, int_value,
size);
res.next = new_pos;
return res;
}
} // namespace
Field ProtoDecoder::FindField(uint32_t field_id) {
Field res{};
auto old_position = read_ptr_;
read_ptr_ = begin_;
for (auto f = ReadField(); f.valid(); f = ReadField()) {
if (f.id() == field_id) {
res = f;
break;
}
}
read_ptr_ = old_position;
return res;
}
PERFETTO_ALWAYS_INLINE
Field ProtoDecoder::ReadField() {
ParseFieldResult res = ParseOneField(read_ptr_, end_);
read_ptr_ = res.next;
return res.field;
}
void TypedProtoDecoderBase::ParseAllFields() {
const uint8_t* cur = begin_;
ParseFieldResult res;
for (;;) {
res = ParseOneField(cur, end_);
if (res.next == cur)
break;
PERFETTO_DCHECK(res.field.valid());
cur = res.next;
auto field_id = res.field.id();
if (PERFETTO_UNLIKELY(field_id >= num_fields_))
continue;
Field* fld = &fields_[field_id];
if (PERFETTO_LIKELY(!fld->valid())) {
// This is the first time we see this field.
*fld = std::move(res.field);
} else {
// Repeated field case.
// In this case we need to:
// 1. Append the last value of the field to end of the repeated field
// storage.
// 2. Replace the default instance at offset |field_id| with the current
// value. This is because in case of repeated field a call to Get(X) is
// supposed to return the last value of X, not the first one.
// This is so that the RepeatedFieldIterator will iterate in the right
// order, see comments on RepeatedFieldIterator.
if (PERFETTO_UNLIKELY(size_ >= capacity_)) {
ExpandHeapStorage();
// ExpandHeapStorage moves fields_ so we need to update the ptr to fld:
fld = &fields_[field_id];
PERFETTO_DCHECK(size_ < capacity_);
}
fields_[size_++] = *fld;
*fld = std::move(res.field);
}
}
read_ptr_ = res.next;
}
void TypedProtoDecoderBase::ExpandHeapStorage() {
uint32_t new_capacity = capacity_ * 2;
PERFETTO_CHECK(new_capacity > size_);
std::unique_ptr<Field[]> new_storage(new Field[new_capacity]);
static_assert(PERFETTO_IS_TRIVIALLY_COPYABLE(Field),
"Field must be trivially copyable");
memcpy(&new_storage[0], fields_, sizeof(Field) * size_);
heap_storage_ = std::move(new_storage);
fields_ = &heap_storage_[0];
capacity_ = new_capacity;
}
} // namespace protozero