Introduce core ProtoZero support classes (Part 1)

Introduces the core classes to deal with zero-copy
zero-malloc append-only protobuf generation.
The actual ProtoZeroMessage will come in a separate
CL.

Change-Id: I4b278cfec6409f745532b17e9adaf2bb09ee2c92
diff --git a/protozero/src/proto_utils_unittest.cc b/protozero/src/proto_utils_unittest.cc
new file mode 100644
index 0000000..45f03ca
--- /dev/null
+++ b/protozero/src/proto_utils_unittest.cc
@@ -0,0 +1,203 @@
+/*
+ * Copyright (C) 2017 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 "protozero/proto_utils.h"
+
+#include <limits>
+
+#include "cpp_common/base.h"
+#include "gtest/gtest.h"
+
+namespace protozero {
+namespace proto_utils {
+namespace {
+
+struct VarIntExpectation {
+  const char* encoded;
+  size_t encoded_size;
+  uint64_t int_value;
+};
+
+const VarIntExpectation kVarIntExpectations[] = {
+    {"\x00", 1, 0},
+    {"\x01", 1, 0x1},
+    {"\x7f", 1, 0x7F},
+    {"\xFF\x01", 2, 0xFF},
+    {"\xFF\x7F", 2, 0x3FFF},
+    {"\x80\x80\x01", 3, 0x4000},
+    {"\xFF\xFF\x7F", 3, 0x1FFFFF},
+    {"\x80\x80\x80\x01", 4, 0x200000},
+    {"\xFF\xFF\xFF\x7F", 4, 0xFFFFFFF},
+    {"\x80\x80\x80\x80\x01", 5, 0x10000000},
+    {"\xFF\xFF\xFF\xFF\x0F", 5, 0xFFFFFFFF},
+    {"\x80\x80\x80\x80\x10", 5, 0x100000000},
+    {"\xFF\xFF\xFF\xFF\x7F", 5, 0x7FFFFFFFF},
+    {"\x80\x80\x80\x80\x80\x01", 6, 0x800000000},
+    {"\xFF\xFF\xFF\xFF\xFF\x7F", 6, 0x3FFFFFFFFFF},
+    {"\x80\x80\x80\x80\x80\x80\x01", 7, 0x40000000000},
+    {"\xFF\xFF\xFF\xFF\xFF\xFF\x7F", 7, 0x1FFFFFFFFFFFF},
+    {"\x80\x80\x80\x80\x80\x80\x80\x01", 8, 0x2000000000000},
+    {"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x7F", 8, 0xFFFFFFFFFFFFFF},
+    {"\x80\x80\x80\x80\x80\x80\x80\x80\x01", 9, 0x100000000000000},
+    {"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x7F", 9, 0x7FFFFFFFFFFFFFFF},
+    {"\x80\x80\x80\x80\x80\x80\x80\x80\x80\x01", 10, 0x8000000000000000},
+    {"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x01", 10, 0xFFFFFFFFFFFFFFFF},
+};
+
+TEST(ProtoUtilsTest, FieldPreambleEncoding) {
+  // According to C++ standard, right shift of negative value has
+  // implementation-defined resulting value.
+  if ((static_cast<int32_t>(0x80000000u) >> 31) != -1)
+    FAIL() << "Platform has unsupported negative number format or arithmetic";
+
+  EXPECT_EQ(0x08u, MakeTagVarInt(1));
+  EXPECT_EQ(0x09u, MakeTagFixed<uint64_t>(1));
+  EXPECT_EQ(0x0Au, MakeTagLengthDelimited(1));
+  EXPECT_EQ(0x0Du, MakeTagFixed<uint32_t>(1));
+
+  EXPECT_EQ(0x03F8u, MakeTagVarInt(0x7F));
+  EXPECT_EQ(0x03F9u, MakeTagFixed<int64_t>(0x7F));
+  EXPECT_EQ(0x03FAu, MakeTagLengthDelimited(0x7F));
+  EXPECT_EQ(0x03FDu, MakeTagFixed<int32_t>(0x7F));
+
+  EXPECT_EQ(0x0400u, MakeTagVarInt(0x80));
+  EXPECT_EQ(0x0401u, MakeTagFixed<double>(0x80));
+  EXPECT_EQ(0x0402u, MakeTagLengthDelimited(0x80));
+  EXPECT_EQ(0x0405u, MakeTagFixed<float>(0x80));
+
+  EXPECT_EQ(0x01FFF8u, MakeTagVarInt(0x3fff));
+  EXPECT_EQ(0x01FFF9u, MakeTagFixed<int64_t>(0x3fff));
+  EXPECT_EQ(0x01FFFAu, MakeTagLengthDelimited(0x3fff));
+  EXPECT_EQ(0x01FFFDu, MakeTagFixed<int32_t>(0x3fff));
+
+  EXPECT_EQ(0x020000u, MakeTagVarInt(0x4000));
+  EXPECT_EQ(0x020001u, MakeTagFixed<int64_t>(0x4000));
+  EXPECT_EQ(0x020002u, MakeTagLengthDelimited(0x4000));
+  EXPECT_EQ(0x020005u, MakeTagFixed<int32_t>(0x4000));
+}
+
+TEST(ProtoUtilsTest, ZigZagEncoding) {
+  EXPECT_EQ(0u, ZigZagEncode(0));
+  EXPECT_EQ(1u, ZigZagEncode(-1));
+  EXPECT_EQ(2u, ZigZagEncode(1));
+  EXPECT_EQ(3u, ZigZagEncode(-2));
+  EXPECT_EQ(4294967293u, ZigZagEncode(-2147483647));
+  EXPECT_EQ(4294967294u, ZigZagEncode(2147483647));
+  EXPECT_EQ(std::numeric_limits<uint32_t>::max(),
+            ZigZagEncode(std::numeric_limits<int32_t>::min()));
+  EXPECT_EQ(std::numeric_limits<uint64_t>::max(),
+            ZigZagEncode(std::numeric_limits<int64_t>::min()));
+}
+
+TEST(ProtoUtilsTest, VarIntEncoding) {
+  for (size_t i = 0; i < arraysize(kVarIntExpectations); ++i) {
+    const VarIntExpectation& exp = kVarIntExpectations[i];
+    uint8_t buf[32];
+    uint8_t* res = WriteVarInt<uint64_t>(exp.int_value, buf);
+    ASSERT_EQ(exp.encoded_size, static_cast<size_t>(res - buf));
+    ASSERT_EQ(0, memcmp(buf, exp.encoded, exp.encoded_size));
+
+    if (exp.int_value <= std::numeric_limits<uint32_t>::max()) {
+      uint8_t* res_32 =
+          WriteVarInt<uint32_t>(static_cast<uint32_t>(exp.int_value), buf);
+      ASSERT_EQ(exp.encoded_size, static_cast<size_t>(res_32 - buf));
+      ASSERT_EQ(0, memcmp(buf, exp.encoded, exp.encoded_size));
+    }
+  }
+}
+
+TEST(ProtoUtilsTest, RedundantVarIntEncoding) {
+  uint8_t buf[kMessageLengthFieldSize];
+
+  WriteRedundantVarInt(0, buf);
+  EXPECT_EQ(0, memcmp("\x80\x80\x80\x00", buf, sizeof(buf)));
+
+  WriteRedundantVarInt(1, buf);
+  EXPECT_EQ(0, memcmp("\x81\x80\x80\x00", buf, sizeof(buf)));
+
+  WriteRedundantVarInt(0x80, buf);
+  EXPECT_EQ(0, memcmp("\x80\x81\x80\x00", buf, sizeof(buf)));
+
+  WriteRedundantVarInt(0x332211, buf);
+  EXPECT_EQ(0, memcmp("\x91\xC4\xCC\x01", buf, sizeof(buf)));
+
+  // Largest allowed length.
+  WriteRedundantVarInt(0x0FFFFFFF, buf);
+  EXPECT_EQ(0, memcmp("\xFF\xFF\xFF\x7F", buf, sizeof(buf)));
+}
+
+TEST(ProtoUtilsTest, VarIntDecoding) {
+  for (size_t i = 0; i < arraysize(kVarIntExpectations); ++i) {
+    const VarIntExpectation& exp = kVarIntExpectations[i];
+    uint64_t value = std::numeric_limits<uint64_t>::max();
+    const uint8_t* res = ParseVarInt(
+        reinterpret_cast<const uint8_t*>(exp.encoded),
+        reinterpret_cast<const uint8_t*>(exp.encoded + exp.encoded_size),
+        &value);
+    ASSERT_EQ(reinterpret_cast<const void*>(exp.encoded + exp.encoded_size),
+              reinterpret_cast<const void*>(res));
+    ASSERT_EQ(exp.int_value, value);
+  }
+}
+
+TEST(ProtoUtilsTest, FieldDecoding) {
+  struct FieldExpectation {
+    const char* encoded;
+    size_t encoded_size;
+    uint32_t id;
+    FieldType type;
+    uint64_t int_value;
+  };
+
+  const FieldExpectation kFieldExpectations[] = {
+      {"\x08\x00", 2, 1, kFieldTypeVarInt, 0},
+      {"\x08\x42", 2, 1, kFieldTypeVarInt, 0x42},
+      {"\xF8\x07\x42", 3, 127, kFieldTypeVarInt, 0x42},
+      {"\x90\x4D\xFF\xFF\xFF\xFF\x0F", 7, 1234, kFieldTypeVarInt, 0xFFFFFFFF},
+      {"\x7D\x42\x00\x00\x00", 5, 15, kFieldTypeFixed32, 0x42},
+      {"\x95\x4D\x78\x56\x34\x12", 6, 1234, kFieldTypeFixed32, 0x12345678},
+      {"\x79\x42\x00\x00\x00\x00\x00\x00\x00", 9, 15, kFieldTypeFixed64, 0x42},
+      {"\x91\x4D\x08\x07\x06\x05\x04\x03\x02\x01", 10, 1234, kFieldTypeFixed64,
+       0x0102030405060708},
+      {"\x0A\x00", 2, 1, kFieldTypeLengthDelimited, 0},
+      {"\x0A\x04|abc", 6, 1, kFieldTypeLengthDelimited, 4},
+      {"\x92\x4D\x04|abc", 7, 1234, kFieldTypeLengthDelimited, 4},
+      {"\x92\x4D\x83\x01|abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzab"
+       "cdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstu"
+       "vwx",
+       135, 1234, kFieldTypeLengthDelimited, 131},
+  };
+
+  for (size_t i = 0; i < arraysize(kFieldExpectations); ++i) {
+    const FieldExpectation& exp = kFieldExpectations[i];
+    FieldType field_type = kFieldTypeVarInt;
+    uint32_t field_id = std::numeric_limits<uint32_t>::max();
+    uint64_t field_intvalue = std::numeric_limits<uint64_t>::max();
+    const uint8_t* res = ParseField(
+        reinterpret_cast<const uint8_t*>(exp.encoded),
+        reinterpret_cast<const uint8_t*>(exp.encoded + exp.encoded_size),
+        &field_id, &field_type, &field_intvalue);
+    ASSERT_EQ(reinterpret_cast<const void*>(exp.encoded + exp.encoded_size),
+              reinterpret_cast<const void*>(res));
+    ASSERT_EQ(exp.id, field_id);
+    ASSERT_EQ(exp.type, field_type);
+    ASSERT_EQ(exp.int_value, field_intvalue);
+  }
+}
+
+}  // namespace
+}  // namespace proto_utils
+}  // namespace protozero