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Commit 6b296db8 authored by Bart Van Assche's avatar Bart Van Assche
Browse files

libdm: Make ExtractBlockDeviceName() return its result 

From https://engdoc.corp.google.com/eng/doc/devguide/cpp/styleguide.md

:
"Prefer using return values over output parameters: they improve
readability, and often provide the same or better performance (see the C++
Primer)." Implement this advice for ExtractBlockDeviceName(). This patch
does not change any functionality.

Bug: 194450129
Test: mm libfs_mgr libdm_test
Change-Id: I6363781163eba08e6128507b403200f472f68a59
Signed-off-by: default avatarBart Van Assche <bvanassche@google.com>
parent c5c532fc

fs_mgr/libdm/dm.cpp

+13 −17
Original line number Diff line number Diff line
@@ -578,34 +578,30 @@ std::string DeviceMapper::GetTargetType(const struct dm_target_spec& spec) { 
    return std::string{spec.target_type, sizeof(spec.target_type)};

}



static bool ExtractBlockDeviceName(const std::string& path, std::string* name) {

static std::optional<std::string> ExtractBlockDeviceName(const std::string& path) {

    static constexpr std::string_view kDevBlockPrefix("/dev/block/");

    if (android::base::StartsWith(path, kDevBlockPrefix)) {

        *name = path.substr(kDevBlockPrefix.length());

        return true;

        return path.substr(kDevBlockPrefix.length());

    }

    return false;

    return {};

}



bool DeviceMapper::IsDmBlockDevice(const std::string& path) {

    std::string name;

    if (!ExtractBlockDeviceName(path, &name)) {

        return false;

    }

    return android::base::StartsWith(name, "dm-");

    std::optional<std::string> name = ExtractBlockDeviceName(path);

    return name && android::base::StartsWith(*name, "dm-");

}



std::optional<std::string> DeviceMapper::GetDmDeviceNameByPath(const std::string& path) {

    std::string name;

    if (!ExtractBlockDeviceName(path, &name)) {

    std::optional<std::string> name = ExtractBlockDeviceName(path);

    if (!name) {

        LOG(WARNING) << path << " is not a block device";

        return std::nullopt;

    }

    if (!android::base::StartsWith(name, "dm-")) {

    if (!android::base::StartsWith(*name, "dm-")) {

        LOG(WARNING) << path << " is not a dm device";

        return std::nullopt;

    }

    std::string dm_name_file = "/sys/block/" + name + "/dm/name";

    std::string dm_name_file = "/sys/block/" + *name + "/dm/name";

    std::string dm_name;

    if (!android::base::ReadFileToString(dm_name_file, &dm_name)) {

        PLOG(ERROR) << "Failed to read file " << dm_name_file;
@@ -616,16 +612,16 @@ std::optional<std::string> DeviceMapper::GetDmDeviceNameByPath(const std::string 
}



std::optional<std::string> DeviceMapper::GetParentBlockDeviceByPath(const std::string& path) {

    std::string name;

    if (!ExtractBlockDeviceName(path, &name)) {

    std::optional<std::string> name = ExtractBlockDeviceName(path);

    if (!name) {

        LOG(WARNING) << path << " is not a block device";

        return std::nullopt;

    }

    if (!android::base::StartsWith(name, "dm-")) {

    if (!android::base::StartsWith(*name, "dm-")) {

        // Reached bottom of the device mapper stack.

        return std::nullopt;

    }

    auto slaves_dir = "/sys/block/" + name + "/slaves";

    auto slaves_dir = "/sys/block/" + *name + "/slaves";

    auto dir = std::unique_ptr<DIR, decltype(&closedir)>(opendir(slaves_dir.c_str()), closedir);

    if (dir == nullptr) {

        PLOG(ERROR) << "Failed to open: " << slaves_dir;