Initial sketch.

internal/platform/implementation/linux/BUILD

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+licenses(["notice"])
+
+cc_library(
+	name = "types",
+    hdrs = [
+        "device_info.h",
+    ],
+	srcs = [
+	    "device_info.cc",
+	],
+    deps = [
+        "//internal/platform/implementation:types",
+        "//internal/platform:logging",
+        "@com_google_absl//absl/strings",
+        "@libsystemd//:lib",
+    ],
+)
+

internal/platform/implementation/linux/device_info.cc

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+#include <cstring>
+#include <optional>
+#include <string>
+
+#include <pwd.h>
+#include <sys/types.h>
+#include <systemd/sd-bus.h>
+
+#include "internal/platform/implementation/device_info.h"
+#include "internal/platform/implementation/linux/device_info.h"
+#include "internal/platform/logging.h"
+
+namespace nearby {
+
+namespace linux {
+
+const char *HOSTNAME_DEST = "org.freedesktop.hostname1";
+const char *HOSTNAME_PATH = "/org/freedesktop/hostname1";
+const char *HOSTNAME_INTERFACE = "org.freedesktop.hostname1";
+
+std::optional<std::u16string> DeviceInfo::GetOsDeviceName() const {
+  sd_bus *bus = nullptr;
+  if (sd_bus_default_system(&bus) < 0) {
+    NEARBY_LOGS(ERROR) << __func__ << ": Error connecting to systemd bus.";
+    return std::nullopt;
+  }
+
+  sd_bus_error err = SD_BUS_ERROR_NULL;
+
+  char *hostname = nullptr;
+  if (sd_bus_get_property_string(bus, HOSTNAME_DEST, HOSTNAME_PATH,
+                                 HOSTNAME_INTERFACE, "PrettyHostname", &err,
+                                 &hostname) < 0) {
+    NEARBY_LOGS(ERROR)
+        << __func__
+        << ": Error getting PrettyHostname from org.freedesktop.hostname1: "
+        << err.message;
+  }
+  if (!hostname || hostname[0] == '\0') {
+    int ret = sd_bus_get_property_string(bus, HOSTNAME_DEST, HOSTNAME_PATH,
+                                         HOSTNAME_INTERFACE, "Hostname", &err,
+                                         &hostname);
+    if (ret < 0) {
+      NEARBY_LOGS(ERROR)
+          << __func__
+          << ": Error getting Hostname from org.freedesktop.hostname1: "
+          << err.message;
+      sd_bus_error_free(&err);
+      sd_bus_unref(bus);
+      return std::nullopt;
+    }
+  }
+
+  sd_bus_error_free(&err);
+  sd_bus_unref(bus);
+
+  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
+
+  std::u16string name = convert.from_bytes(hostname);
+  free(hostname);
+  return name;
+}
+
+api::DeviceInfo::DeviceType DeviceInfo::GetDeviceType() const {
+  sd_bus *bus;
+  if (sd_bus_default_system(&bus) < 0) {
+    NEARBY_LOGS(ERROR) << __func__ << ": Error connecting to systemd bus.";
+    return api::DeviceInfo::DeviceType::kUnknown;
+  }
+  sd_bus_error err = SD_BUS_ERROR_NULL;
+  char *chasis = nullptr;
+
+  if (sd_bus_get_property_string(bus, HOSTNAME_DEST, HOSTNAME_PATH,
+                                 HOSTNAME_INTERFACE, "Chasis", &err,
+                                 &chasis) < 0) {
+    NEARBY_LOGS(ERROR)
+        << __func__ << ": Error getting Chasis from org.freedesktop.hostname1: "
+        << err.message;
+    sd_bus_error_free(&err);
+    sd_bus_unref(bus);
+    return api::DeviceInfo::DeviceType::kUnknown;
+  }
+
+  sd_bus_unref(bus);
+
+  api::DeviceInfo::DeviceType device = api::DeviceInfo::DeviceType::kUnknown;
+
+  if (strcmp(chasis, "phone") == 0) {
+    device = api::DeviceInfo::DeviceType::kPhone;
+  } else if (strcmp(chasis, "laptop") == 0 || strcmp(chasis, "desktop") == 0) {
+    device = api::DeviceInfo::DeviceType::kLaptop;
+  } else if (strcmp(chasis, "tablet") == 0) {
+    device = api::DeviceInfo::DeviceType::kTablet;
+  } else if (strcmp(chasis, "handset") == 0) {
+    device = api::DeviceInfo::DeviceType::kPhone;
+  }
+  free(chasis);
+  return device;
+}
+
+std::optional<std::u16string> DeviceInfo::GetFullName() const {
+  struct passwd *pwd = getpwuid(getuid());
+  if (!pwd) {
+    return std::nullopt;
+  }
+  char *name = strtok(pwd->pw_gecos, ",");
+
+  std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
+  return convert.from_bytes(name ? name : pwd->pw_gecos);
+}
+
+std::optional<std::string> DeviceInfo::GetProfileUserName() const {
+  struct passwd *pwd = getpwuid(getuid());
+  if (!pwd) {
+    return std::nullopt;
+  }
+  char *name = strtok(pwd->pw_gecos, ",");
+  return std::string(name);
+}
+} // namespace linux
+} // namespace nearby

internal/platform/implementation/linux/device_info.h

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+#ifndef PLATFORM_IMPL_LINUX_DEVICE_INFO_H_
+#define PLATFORM_IMPL_LINUX_DEVICE_INFO_H_
+
+#include <systemd/sd-bus.h>
+
+#include <optional>
+#include <string>
+
+#include "absl/strings/string_view.h"
+#include "internal/platform/implementation/device_info.h"
+
+namespace nearby {
+namespace linux {
+
+class DeviceInfo : public api::DeviceInfo {
+public:
+  ~DeviceInfo() override;
+
+  std::optional<std::u16string> GetOsDeviceName() const override;
+  api::DeviceInfo::DeviceType GetDeviceType() const override;
+  api::DeviceInfo::OsType GetOsType() const override {
+    return api::DeviceInfo::OsType::kWindows; // Or ChromeOS?
+  }
+  std::optional<std::u16string> GetFullName() const override;
+  std::optional<std::u16string> GetGivenName() const override {
+    return GetFullName();
+  }
+  std::optional<std::u16string> GetLastName() const override {
+    return GetFullName();
+  }
+  std::optional<std::string> GetProfileUserName() const override;
+
+  std::optional<std::filesystem::path> GetDownloadPath() const override;
+  std::optional<std::filesystem::path> GetLocalAppDataPath() const override;
+  std::optional<std::filesystem::path> GetCommonAppDataPath() const override;
+  std::optional<std::filesystem::path> GetTemporaryPath() const override;
+  std::optional<std::filesystem::path> GetLogPath() const override;
+  std::optional<std::filesystem::path> GetCrashDumpPath() const override;
+
+  bool IsScreenLocked() const override;
+  void RegisterScreenLockedListener(
+      absl::string_view listener_name,
+      std::function<void(api::DeviceInfo::ScreenStatus)> callback) override;
+  void UnregisterScreenLockedListener(absl::string_view listener_name) override;
+
+  sd_bus *system_bus;
+};
+} // namespace linux
+} // namespace nearby
+
+#endif // PLATFORM_IMPL_LINUX_DEVICE_INFO_H_

internal/platform/implementation/linux/platform.cc

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+#include "internal/platform/implementation/platform.h"
+
+#include <filesystem>
+#include <string>
+
+namespace nearby {
+namespace api {
+namespace {
+  std::string ImplementationPlatform::GetCustomSavePath()
+}
+} // namespace api
+} // namespace nearby