assemble_vintf: refactor to prepare for test

* Abstract out an API used by assemble_vintf_main
* split main() to a different file
* rename files.
* Wrap getenv() calls so that values can be fake.

Test: libvintf_test

Change-Id: I515012c005a8b6010fbf455b84baef4c398b5817
diff --git a/AssembleVintf.cpp b/AssembleVintf.cpp
new file mode 100644
index 0000000..a624157
--- /dev/null
+++ b/AssembleVintf.cpp
@@ -0,0 +1,668 @@
+/*
+ * 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 <stdlib.h>
+#include <unistd.h>
+
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <unordered_map>
+
+#include <android-base/file.h>
+#include <android-base/parseint.h>
+
+#include <vintf/AssembleVintf.h>
+#include <vintf/KernelConfigParser.h>
+#include <vintf/parse_string.h>
+#include <vintf/parse_xml.h>
+#include "utils.h"
+
+#define BUFFER_SIZE sysconf(_SC_PAGESIZE)
+
+namespace android {
+namespace vintf {
+
+static const std::string gConfigPrefix = "android-base-";
+static const std::string gConfigSuffix = ".cfg";
+static const std::string gBaseConfig = "android-base.cfg";
+
+// An input stream with a name.
+// The input stream may be an actual file, or a stringstream for testing.
+// It takes ownership on the istream.
+class NamedIstream {
+   public:
+    NamedIstream(const std::string& name, std::unique_ptr<std::istream>&& stream)
+        : mName(name), mStream(std::move(stream)) {}
+    const std::string& name() const { return mName; }
+    std::istream& stream() { return *mStream; }
+
+   private:
+    std::string mName;
+    std::unique_ptr<std::istream> mStream;
+};
+
+/**
+ * Slurps the device manifest file and add build time flag to it.
+ */
+class AssembleVintfImpl : public AssembleVintf {
+    using Condition = std::unique_ptr<KernelConfig>;
+    using ConditionedConfig = std::pair<Condition, std::vector<KernelConfig> /* configs */>;
+
+   public:
+    void setFakeEnv(const std::string& key, const std::string& value) { mFakeEnv[key] = value; }
+
+    std::string getEnv(const std::string& key) const {
+        auto it = mFakeEnv.find(key);
+        if (it != mFakeEnv.end()) {
+            return it->second;
+        }
+        const char* envValue = getenv(key.c_str());
+        return envValue != nullptr ? std::string(envValue) : std::string();
+    }
+
+    template <typename T>
+    bool getFlag(const std::string& key, T* value) const {
+        std::string envValue = getEnv(key);
+        if (envValue.empty()) {
+            std::cerr << "Warning: " << key << " is missing, defaulted to " << (*value) << "."
+                      << std::endl;
+            return true;
+        }
+
+        if (!parse(envValue, value)) {
+            std::cerr << "Cannot parse " << envValue << "." << std::endl;
+            return false;
+        }
+        return true;
+    }
+
+    /**
+     * Set *out to environment variable if *out is not a dummy value (i.e. default constructed).
+     */
+    template <typename T>
+    bool getFlagIfUnset(const std::string& envKey, T* out) const {
+        bool hasExistingValue = !(*out == T{});
+
+        bool hasEnvValue = false;
+        T envValue;
+        std::string envStrValue = getEnv(envKey);
+        if (!envStrValue.empty()) {
+            if (!parse(envStrValue, &envValue)) {
+                std::cerr << "Cannot parse " << envValue << "." << std::endl;
+                return false;
+            }
+            hasEnvValue = true;
+        }
+
+        if (hasExistingValue) {
+            if (hasEnvValue) {
+                std::cerr << "Warning: cannot override existing value " << *out << " with "
+                          << envKey << " (which is " << envValue << ")." << std::endl;
+            }
+            return false;
+        }
+        if (!hasEnvValue) {
+            std::cerr << "Warning: " << envKey << " is not specified. Default to " << T{} << "."
+                      << std::endl;
+            return false;
+        }
+        *out = envValue;
+        return true;
+    }
+
+    bool getBooleanFlag(const std::string& key) const { return getEnv(key) == std::string("true"); }
+
+    size_t getIntegerFlag(const std::string& key, size_t defaultValue = 0) const {
+        std::string envValue = getEnv(key);
+        if (envValue.empty()) {
+            return defaultValue;
+        }
+        size_t value;
+        if (!base::ParseUint(envValue, &value)) {
+            std::cerr << "Error: " << key << " must be a number." << std::endl;
+            return defaultValue;
+        }
+        return value;
+    }
+
+    static std::string read(std::basic_istream<char>& is) {
+        std::stringstream ss;
+        ss << is.rdbuf();
+        return ss.str();
+    }
+
+    static bool isCommonConfig(const std::string& path) {
+        return ::android::base::Basename(path) == gBaseConfig;
+    }
+
+    static Level convertFromApiLevel(size_t apiLevel) {
+        if (apiLevel < 26) {
+            return Level::LEGACY;
+        } else if (apiLevel == 26) {
+            return Level::O;
+        } else if (apiLevel == 27) {
+            return Level::O_MR1;
+        } else {
+            return Level::UNSPECIFIED;
+        }
+    }
+
+    // nullptr on any error, otherwise the condition.
+    static Condition generateCondition(const std::string& path) {
+        std::string fname = ::android::base::Basename(path);
+        if (fname.size() <= gConfigPrefix.size() + gConfigSuffix.size() ||
+            !std::equal(gConfigPrefix.begin(), gConfigPrefix.end(), fname.begin()) ||
+            !std::equal(gConfigSuffix.rbegin(), gConfigSuffix.rend(), fname.rbegin())) {
+            return nullptr;
+        }
+
+        std::string sub = fname.substr(gConfigPrefix.size(),
+                                       fname.size() - gConfigPrefix.size() - gConfigSuffix.size());
+        if (sub.empty()) {
+            return nullptr;  // should not happen
+        }
+        for (size_t i = 0; i < sub.size(); ++i) {
+            if (sub[i] == '-') {
+                sub[i] = '_';
+                continue;
+            }
+            if (isalnum(sub[i])) {
+                sub[i] = toupper(sub[i]);
+                continue;
+            }
+            std::cerr << "'" << fname << "' (in " << path
+                      << ") is not a valid kernel config file name. Must match regex: "
+                      << "android-base(-[0-9a-zA-Z-]+)?\\.cfg" << std::endl;
+            return nullptr;
+        }
+        sub.insert(0, "CONFIG_");
+        return std::make_unique<KernelConfig>(std::move(sub), Tristate::YES);
+    }
+
+    static bool parseFileForKernelConfigs(std::basic_istream<char>& stream,
+                                          std::vector<KernelConfig>* out) {
+        KernelConfigParser parser(true /* processComments */, true /* relaxedFormat */);
+        std::string content = read(stream);
+        status_t err = parser.process(content.c_str(), content.size());
+        if (err != OK) {
+            std::cerr << parser.error();
+            return false;
+        }
+        err = parser.finish();
+        if (err != OK) {
+            std::cerr << parser.error();
+            return false;
+        }
+
+        for (auto& configPair : parser.configs()) {
+            out->push_back({});
+            KernelConfig& config = out->back();
+            config.first = std::move(configPair.first);
+            if (!parseKernelConfigTypedValue(configPair.second, &config.second)) {
+                std::cerr << "Unknown value type for key = '" << config.first << "', value = '"
+                          << configPair.second << "'\n";
+                return false;
+            }
+        }
+        return true;
+    }
+
+    static bool parseFilesForKernelConfigs(std::vector<NamedIstream>* streams,
+                                           std::vector<ConditionedConfig>* out) {
+        out->clear();
+        ConditionedConfig commonConfig;
+        bool foundCommonConfig = false;
+        bool ret = true;
+
+        for (auto& namedStream : *streams) {
+            if (isCommonConfig(namedStream.name())) {
+                ret &= parseFileForKernelConfigs(namedStream.stream(), &commonConfig.second);
+                foundCommonConfig = true;
+            } else {
+                Condition condition = generateCondition(namedStream.name());
+                ret &= (condition != nullptr);
+
+                std::vector<KernelConfig> kernelConfigs;
+                if ((ret &= parseFileForKernelConfigs(namedStream.stream(), &kernelConfigs)))
+                    out->emplace_back(std::move(condition), std::move(kernelConfigs));
+            }
+        }
+
+        if (!foundCommonConfig) {
+            std::cerr << "No android-base.cfg is found in these paths:" << std::endl;
+            for (auto& namedStream : *streams) {
+                std::cerr << "    " << namedStream.name() << std::endl;
+            }
+        }
+        ret &= foundCommonConfig;
+        // first element is always common configs (no conditions).
+        out->insert(out->begin(), std::move(commonConfig));
+        return ret;
+    }
+
+    static std::string getFileNameFromPath(std::string path) {
+        auto idx = path.find_last_of("\\/");
+        if (idx != std::string::npos) {
+            path.erase(0, idx + 1);
+        }
+        return path;
+    }
+
+    std::basic_ostream<char>& out() const { return mOutRef == nullptr ? std::cout : *mOutRef; }
+
+    template <typename S>
+    using Schemas = std::vector<std::pair<std::string, S>>;
+    using HalManifests = Schemas<HalManifest>;
+    using CompatibilityMatrices = Schemas<CompatibilityMatrix>;
+
+    bool assembleHalManifest(HalManifests* halManifests) {
+        std::string error;
+        HalManifest* halManifest = &halManifests->front().second;
+        for (auto it = halManifests->begin() + 1; it != halManifests->end(); ++it) {
+            const std::string& path = it->first;
+            HalManifest& halToAdd = it->second;
+
+            if (halToAdd.level() != Level::UNSPECIFIED) {
+                if (halManifest->level() == Level::UNSPECIFIED) {
+                    halManifest->mLevel = halToAdd.level();
+                } else if (halManifest->level() != halToAdd.level()) {
+                    std::cerr << "Inconsistent FCM Version in HAL manifests:" << std::endl
+                              << "    File '" << halManifests->front().first << "' has level "
+                              << halManifest->level() << std::endl
+                              << "    File '" << path << "' has level " << halToAdd.level()
+                              << std::endl;
+                    return false;
+                }
+            }
+
+            if (!halManifest->addAllHals(&halToAdd, &error)) {
+                std::cerr << "File \"" << path << "\" cannot be added: conflict on HAL \"" << error
+                          << "\" with an existing HAL. See <hal> with the same name "
+                          << "in previously parsed files or previously declared in this file."
+                          << std::endl;
+                return false;
+            }
+        }
+
+        if (halManifest->mType == SchemaType::DEVICE) {
+            if (!getFlag("BOARD_SEPOLICY_VERS", &halManifest->device.mSepolicyVersion)) {
+                return false;
+            }
+            if (!setDeviceFcmVersion(halManifest)) {
+                return false;
+            }
+        }
+
+        if (mOutputMatrix) {
+            CompatibilityMatrix generatedMatrix = halManifest->generateCompatibleMatrix();
+            if (!halManifest->checkCompatibility(generatedMatrix, &error)) {
+                std::cerr << "FATAL ERROR: cannot generate a compatible matrix: " << error
+                          << std::endl;
+            }
+            out() << "<!-- \n"
+                     "    Autogenerated skeleton compatibility matrix. \n"
+                     "    Use with caution. Modify it to suit your needs.\n"
+                     "    All HALs are set to optional.\n"
+                     "    Many entries other than HALs are zero-filled and\n"
+                     "    require human attention. \n"
+                     "-->\n"
+                  << gCompatibilityMatrixConverter(generatedMatrix, mSerializeFlags);
+        } else {
+            out() << gHalManifestConverter(*halManifest, mSerializeFlags);
+        }
+        out().flush();
+
+        if (mCheckFile != nullptr) {
+            CompatibilityMatrix checkMatrix;
+            if (!gCompatibilityMatrixConverter(&checkMatrix, read(*mCheckFile))) {
+                std::cerr << "Cannot parse check file as a compatibility matrix: "
+                          << gCompatibilityMatrixConverter.lastError() << std::endl;
+                return false;
+            }
+            if (!halManifest->checkCompatibility(checkMatrix, &error)) {
+                std::cerr << "Not compatible: " << error << std::endl;
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    bool assembleFrameworkCompatibilityMatrixKernels(CompatibilityMatrix* matrix) {
+        for (auto& pair : mKernels) {
+            std::vector<ConditionedConfig> conditionedConfigs;
+            if (!parseFilesForKernelConfigs(&pair.second, &conditionedConfigs)) {
+                return false;
+            }
+            for (ConditionedConfig& conditionedConfig : conditionedConfigs) {
+                MatrixKernel kernel(KernelVersion{pair.first.majorVer, pair.first.minorVer, 0u},
+                                    std::move(conditionedConfig.second));
+                if (conditionedConfig.first != nullptr)
+                    kernel.mConditions.push_back(std::move(*conditionedConfig.first));
+                matrix->framework.mKernels.push_back(std::move(kernel));
+            }
+        }
+        return true;
+    }
+
+    bool setDeviceFcmVersion(HalManifest* manifest) {
+        size_t shippingApiLevel = getIntegerFlag("PRODUCT_SHIPPING_API_LEVEL");
+
+        if (manifest->level() != Level::UNSPECIFIED) {
+            return true;
+        }
+        if (!getBooleanFlag("PRODUCT_ENFORCE_VINTF_MANIFEST")) {
+            manifest->mLevel = Level::LEGACY;
+            return true;
+        }
+        // TODO(b/70628538): Do not infer from Shipping API level.
+        if (shippingApiLevel) {
+            std::cerr << "Warning: Shipping FCM Version is inferred from Shipping API level. "
+                      << "Declare Shipping FCM Version in device manifest directly." << std::endl;
+            manifest->mLevel = convertFromApiLevel(shippingApiLevel);
+            if (manifest->mLevel == Level::UNSPECIFIED) {
+                std::cerr << "Error: Shipping FCM Version cannot be inferred from Shipping API "
+                          << "level " << shippingApiLevel << "."
+                          << "Declare Shipping FCM Version in device manifest directly."
+                          << std::endl;
+                return false;
+            }
+            return true;
+        }
+        // TODO(b/69638851): should be an error if Shipping API level is not defined.
+        // For now, just leave it empty; when framework compatibility matrix is built,
+        // lowest FCM Version is assumed.
+        std::cerr << "Warning: Shipping FCM Version cannot be inferred, because:" << std::endl
+                  << "    (1) It is not explicitly declared in device manifest;" << std::endl
+                  << "    (2) PRODUCT_ENFORCE_VINTF_MANIFEST is set to true;" << std::endl
+                  << "    (3) PRODUCT_SHIPPING_API_LEVEL is undefined." << std::endl
+                  << "Assuming 'unspecified' Shipping FCM Version. " << std::endl
+                  << "To remove this warning, define 'level' attribute in device manifest."
+                  << std::endl;
+        return true;
+    }
+
+    Level getLowestFcmVersion(const CompatibilityMatrices& matrices) {
+        Level ret = Level::UNSPECIFIED;
+        for (const auto& e : matrices) {
+            if (ret == Level::UNSPECIFIED || ret > e.second.level()) {
+                ret = e.second.level();
+            }
+        }
+        return ret;
+    }
+
+    bool assembleCompatibilityMatrix(CompatibilityMatrices* matrices) {
+        std::string error;
+        CompatibilityMatrix* matrix = nullptr;
+        KernelSepolicyVersion kernelSepolicyVers;
+        Version sepolicyVers;
+        std::unique_ptr<HalManifest> checkManifest;
+        if (matrices->front().second.mType == SchemaType::DEVICE) {
+            matrix = &matrices->front().second;
+        }
+
+        if (matrices->front().second.mType == SchemaType::FRAMEWORK) {
+            Level deviceLevel = Level::UNSPECIFIED;
+            std::vector<std::string> fileList;
+            if (mCheckFile != nullptr) {
+                checkManifest = std::make_unique<HalManifest>();
+                if (!gHalManifestConverter(checkManifest.get(), read(*mCheckFile))) {
+                    std::cerr << "Cannot parse check file as a HAL manifest: "
+                              << gHalManifestConverter.lastError() << std::endl;
+                    return false;
+                }
+                deviceLevel = checkManifest->level();
+            }
+
+            if (deviceLevel == Level::UNSPECIFIED) {
+                // For GSI build, legacy devices that do not have a HAL manifest,
+                // and devices in development, merge all compatibility matrices.
+                deviceLevel = getLowestFcmVersion(*matrices);
+            }
+
+            for (auto& e : *matrices) {
+                if (e.second.level() == deviceLevel) {
+                    fileList.push_back(e.first);
+                    matrix = &e.second;
+                }
+            }
+            if (matrix == nullptr) {
+                std::cerr << "FATAL ERROR: cannot find matrix with level '" << deviceLevel << "'"
+                          << std::endl;
+                return false;
+            }
+            for (auto& e : *matrices) {
+                if (e.second.level() <= deviceLevel) {
+                    continue;
+                }
+                fileList.push_back(e.first);
+                if (!matrix->addAllHalsAsOptional(&e.second, &error)) {
+                    std::cerr << "File \"" << e.first << "\" cannot be added: " << error
+                              << ". See <hal> with the same name "
+                              << "in previously parsed files or previously declared in this file."
+                              << std::endl;
+                    return false;
+                }
+            }
+
+            if (!getFlag("BOARD_SEPOLICY_VERS", &sepolicyVers)) {
+                return false;
+            }
+            if (!getFlag("POLICYVERS", &kernelSepolicyVers)) {
+                return false;
+            }
+
+            if (!assembleFrameworkCompatibilityMatrixKernels(matrix)) {
+                return false;
+            }
+
+            matrix->framework.mSepolicy =
+                Sepolicy(kernelSepolicyVers, {{sepolicyVers.majorVer, sepolicyVers.minorVer}});
+
+            Version avbMetaVersion;
+            if (!getFlag("FRAMEWORK_VBMETA_VERSION", &avbMetaVersion)) {
+                return false;
+            }
+            matrix->framework.mAvbMetaVersion = avbMetaVersion;
+
+            out() << "<!--" << std::endl;
+            out() << "    Input:" << std::endl;
+            for (const auto& path : fileList) {
+                out() << "        " << getFileNameFromPath(path) << std::endl;
+            }
+            out() << "-->" << std::endl;
+        }
+        out() << gCompatibilityMatrixConverter(*matrix, mSerializeFlags);
+        out().flush();
+
+        if (checkManifest != nullptr && getBooleanFlag("PRODUCT_ENFORCE_VINTF_MANIFEST") &&
+            !checkManifest->checkCompatibility(*matrix, &error)) {
+            std::cerr << "Not compatible: " << error << std::endl;
+            return false;
+        }
+
+        return true;
+    }
+
+    enum AssembleStatus { SUCCESS, FAIL_AND_EXIT, TRY_NEXT };
+    template <typename Schema, typename AssembleFunc>
+    AssembleStatus tryAssemble(const XmlConverter<Schema>& converter, const std::string& schemaName,
+                               AssembleFunc assemble) {
+        Schemas<Schema> schemas;
+        Schema schema;
+        if (!converter(&schema, read(mInFiles.front().stream()))) {
+            return TRY_NEXT;
+        }
+        auto firstType = schema.type();
+        schemas.emplace_back(mInFiles.front().name(), std::move(schema));
+
+        for (auto it = mInFiles.begin() + 1; it != mInFiles.end(); ++it) {
+            Schema additionalSchema;
+            const std::string& fileName = it->name();
+            if (!converter(&additionalSchema, read(it->stream()))) {
+                std::cerr << "File \"" << fileName << "\" is not a valid " << firstType << " "
+                          << schemaName << " (but the first file is a valid " << firstType << " "
+                          << schemaName << "). Error: " << converter.lastError() << std::endl;
+                return FAIL_AND_EXIT;
+            }
+            if (additionalSchema.type() != firstType) {
+                std::cerr << "File \"" << fileName << "\" is a " << additionalSchema.type() << " "
+                          << schemaName << " (but a " << firstType << " " << schemaName
+                          << " is expected)." << std::endl;
+                return FAIL_AND_EXIT;
+            }
+
+            schemas.emplace_back(fileName, std::move(additionalSchema));
+        }
+        return assemble(&schemas) ? SUCCESS : FAIL_AND_EXIT;
+    }
+
+    bool assemble() override {
+        using std::placeholders::_1;
+        if (mInFiles.empty()) {
+            std::cerr << "Missing input file." << std::endl;
+            return false;
+        }
+
+        auto status = tryAssemble(gHalManifestConverter, "manifest",
+                                  std::bind(&AssembleVintfImpl::assembleHalManifest, this, _1));
+        if (status == SUCCESS) return true;
+        if (status == FAIL_AND_EXIT) return false;
+
+        resetInFiles();
+
+        status = tryAssemble(gCompatibilityMatrixConverter, "compatibility matrix",
+                             std::bind(&AssembleVintfImpl::assembleCompatibilityMatrix, this, _1));
+        if (status == SUCCESS) return true;
+        if (status == FAIL_AND_EXIT) return false;
+
+        std::cerr << "Input file has unknown format." << std::endl
+                  << "Error when attempting to convert to manifest: "
+                  << gHalManifestConverter.lastError() << std::endl
+                  << "Error when attempting to convert to compatibility matrix: "
+                  << gCompatibilityMatrixConverter.lastError() << std::endl;
+        return false;
+    }
+
+    std::ostream& setOutputStream(Ostream&& out) override {
+        mOutRef = std::move(out);
+        return *mOutRef;
+    }
+
+    std::istream& addInputStream(const std::string& name, Istream&& in) override {
+        auto it = mInFiles.emplace(mInFiles.end(), name, std::move(in));
+        return it->stream();
+    }
+
+    std::istream& setCheckInputStream(Istream&& in) override {
+        mCheckFile = std::move(in);
+        return *mCheckFile;
+    }
+
+    bool hasKernelVersion(const Version& kernelVer) const override {
+        return mKernels.find(kernelVer) != mKernels.end();
+    }
+
+    std::istream& addKernelConfigInputStream(const Version& kernelVer, const std::string& name,
+                                             Istream&& in) override {
+        auto&& kernel = mKernels[kernelVer];
+        auto it = kernel.emplace(kernel.end(), name, std::move(in));
+        return it->stream();
+    }
+
+    void resetInFiles() {
+        for (auto& inFile : mInFiles) {
+            inFile.stream().clear();
+            inFile.stream().seekg(0);
+        }
+    }
+
+    void setOutputMatrix() override { mOutputMatrix = true; }
+
+    bool setHalsOnly() override {
+        if (mSerializeFlags) return false;
+        mSerializeFlags |= SerializeFlag::HALS_ONLY;
+        return true;
+    }
+
+    bool setNoHals() override {
+        if (mSerializeFlags) return false;
+        mSerializeFlags |= SerializeFlag::NO_HALS;
+        return true;
+    }
+
+   private:
+    std::vector<NamedIstream> mInFiles;
+    Ostream mOutRef;
+    Istream mCheckFile;
+    bool mOutputMatrix = false;
+    SerializeFlags mSerializeFlags = SerializeFlag::EVERYTHING;
+    std::map<Version, std::vector<NamedIstream>> mKernels;
+    std::map<std::string, std::string> mFakeEnv;
+};
+
+bool AssembleVintf::openOutFile(const std::string& path) {
+    return static_cast<std::ofstream&>(setOutputStream(std::make_unique<std::ofstream>(path)))
+        .is_open();
+}
+
+bool AssembleVintf::openInFile(const std::string& path) {
+    return static_cast<std::ifstream&>(addInputStream(path, std::make_unique<std::ifstream>(path)))
+        .is_open();
+}
+
+bool AssembleVintf::openCheckFile(const std::string& path) {
+    return static_cast<std::ifstream&>(setCheckInputStream(std::make_unique<std::ifstream>(path)))
+        .is_open();
+}
+
+bool AssembleVintf::addKernel(const std::string& kernelArg) {
+    auto tokens = details::tokenize(kernelArg);
+    if (tokens.size() <= 1) {
+        std::cerr << "Unrecognized --kernel option '" << kernelArg << "'" << std::endl;
+        return false;
+    }
+    Version kernelVer;
+    if (!parse(tokens.front(), &kernelVer)) {
+        std::cerr << "Unrecognized kernel version '" << tokens.front() << "'" << std::endl;
+        return false;
+    }
+    if (hasKernelVersion(kernelVer)) {
+        std::cerr << "Multiple --kernel for " << kernelVer << " is specified." << std::endl;
+        return false;
+    }
+    for (auto it = tokens.begin() + 1; it != tokens.end(); ++it) {
+        bool opened =
+            static_cast<std::ifstream&>(
+                addKernelConfigInputStream(kernelVer, *it, std::make_unique<std::ifstream>(*it)))
+                .is_open();
+        if (!opened) {
+            std::cerr << "Cannot open file '" << *it << "'." << std::endl;
+            return false;
+        }
+    }
+    return true;
+}
+
+std::unique_ptr<AssembleVintf> AssembleVintf::newInstance() {
+    return std::make_unique<AssembleVintfImpl>();
+}
+
+}  // namespace vintf
+}  // namespace android