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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/tracing/core/proto_utils.h"
#include <limits>
#include "base/sys_byteorder.h"
#define CHECK_PTR_LE(a, b) \
CHECK_LE(reinterpret_cast<const void*>(a), reinterpret_cast<const void*>(b))
namespace tracing {
namespace v2 {
namespace proto {
const uint8_t* ParseVarInt(const uint8_t* start,
const uint8_t* end,
uint64_t* value) {
const uint8_t* pos = start;
uint64_t shift = 0;
*value = 0;
do {
CHECK_PTR_LE(pos, end - 1);
DCHECK_LT(shift, 64ull);
*value |= static_cast<uint64_t>(*pos & 0x7f) << shift;
shift += 7;
} while (*pos++ & 0x80);
return pos;
}
const uint8_t* ParseField(const uint8_t* start,
const uint8_t* end,
uint32_t* field_id,
FieldType* field_type,
uint64_t* field_intvalue) {
// 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 uint8_t kFieldTypeMask = (1 << kFieldTypeNumBits) - 1; // 0000 0111;
const uint8_t* pos = start;
CHECK_PTR_LE(pos, end - 1);
*field_type = static_cast<FieldType>(*pos & kFieldTypeMask);
uint64_t raw_field_id;
pos = ParseVarInt(pos, end, &raw_field_id);
raw_field_id >>= kFieldTypeNumBits;
DCHECK_LE(raw_field_id, std::numeric_limits<uint32_t>::max());
*field_id = static_cast<uint32_t>(raw_field_id);
switch (*field_type) {
case kFieldTypeFixed64: {
CHECK_PTR_LE(pos + sizeof(uint64_t), end);
memcpy(field_intvalue, pos, sizeof(uint64_t));
*field_intvalue = base::ByteSwapToLE64(*field_intvalue);
pos += sizeof(uint64_t);
break;
}
case kFieldTypeFixed32: {
CHECK_PTR_LE(pos + sizeof(uint32_t), end);
uint32_t tmp;
memcpy(&tmp, pos, sizeof(uint32_t));
*field_intvalue = base::ByteSwapToLE32(tmp);
pos += sizeof(uint32_t);
break;
}
case kFieldTypeVarInt: {
pos = ParseVarInt(pos, end, field_intvalue);
break;
}
case kFieldTypeLengthDelimited: {
pos = ParseVarInt(pos, end, field_intvalue);
pos += *field_intvalue;
CHECK_PTR_LE(pos, end);
break;
}
default:
NOTREACHED() << "Unsupported proto field type " << *field_type;
}
return pos;
}
} // namespace proto
} // namespace v2
} // namespace tracing
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