SystemMonitor: Add a devices tab

This tab combines info from /proc/devices with device file paths from /dev.

Applications/SystemMonitor/DevicesModel.cpp

@@ -0,0 +1,151 @@
+#include "DevicesModel.h"
+#include <AK/JsonArray.h>
+#include <AK/JsonObject.h>
+#include <AK/JsonValue.h>
+#include <LibCore/CDirIterator.h>
+#include <LibCore/CFile.h>
+#include <sys/stat.h>
+
+NonnullRefPtr<DevicesModel> DevicesModel::create()
+{
+    return adopt(*new DevicesModel);
+}
+
+DevicesModel::DevicesModel()
+{
+}
+
+DevicesModel::~DevicesModel()
+{
+}
+
+int DevicesModel::row_count(const GModelIndex&) const
+{
+    return m_devices.size();
+}
+
+int DevicesModel::column_count(const GModelIndex&) const
+{
+    return Column::__Count;
+}
+
+String DevicesModel::column_name(int column) const
+{
+    switch (column) {
+    case Column::Device:
+        return "Device";
+    case Column::Major:
+        return "Major";
+    case Column::Minor:
+        return "Minor";
+    case Column::ClassName:
+        return "Class";
+    case Column::Type:
+        return "Type";
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+GModel::ColumnMetadata DevicesModel::column_metadata(int column) const
+{
+    switch (column) {
+    case Column::Device:
+        return { 70, TextAlignment::CenterLeft };
+    case Column::Major:
+        return { 32, TextAlignment::CenterRight };
+    case Column::Minor:
+        return { 32, TextAlignment::CenterRight };
+    case Column::ClassName:
+        return { 120, TextAlignment::CenterLeft };
+    case Column::Type:
+        return { 120, TextAlignment::CenterLeft };
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+GVariant DevicesModel::data(const GModelIndex& index, Role) const
+{
+    ASSERT(is_valid(index));
+
+    const DeviceInfo& device = m_devices[index.row()];
+    switch (index.column()) {
+    case Column::Device:
+        return device.path;
+    case Column::Major:
+        return device.major;
+    case Column::Minor:
+        return device.minor;
+    case Column::ClassName:
+        return device.class_name;
+    case Column::Type:
+        switch (device.type) {
+        case DeviceInfo::Type::Block:
+            return "Block";
+        case DeviceInfo::Type::Character:
+            return "Character";
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+void DevicesModel::update()
+{
+    CFile proc_devices { "/proc/devices" };
+    if (!proc_devices.open(CIODevice::OpenMode::ReadOnly))
+        ASSERT_NOT_REACHED();
+
+    auto json = JsonValue::from_string(proc_devices.read_all()).as_array();
+
+    m_devices.clear();
+    json.for_each([this](auto& value) {
+        JsonObject device = value.as_object();
+        DeviceInfo device_info;
+
+        device_info.major = device.get("major").to_uint();
+        device_info.minor = device.get("minor").to_uint();
+        device_info.class_name = device.get("class_name").to_string();
+
+        String type_str = device.get("type").to_string();
+        if (type_str == "block")
+            device_info.type = DeviceInfo::Type::Block;
+        else if (type_str == "character")
+            device_info.type = DeviceInfo::Type::Character;
+        else
+            ASSERT_NOT_REACHED();
+
+        m_devices.append(move(device_info));
+    });
+
+    auto fill_in_paths_from_dir = [this](const String& dir) {
+        CDirIterator dir_iter { dir, CDirIterator::Flags::SkipDots };
+        while (dir_iter.has_next()) {
+            auto name = dir_iter.next_path();
+            auto path = String::format("%s/%s", dir.characters(), name.characters());
+            struct stat statbuf;
+            if (lstat(path.characters(), &statbuf) != 0) {
+                ASSERT_NOT_REACHED();
+            }
+            if (!S_ISBLK(statbuf.st_mode) && !S_ISCHR(statbuf.st_mode))
+                continue;
+            unsigned major = ::major(statbuf.st_rdev);
+            unsigned minor = ::minor(statbuf.st_rdev);
+
+            auto it = m_devices.find([major, minor](auto& device_info) {
+                return device_info.major == major && device_info.minor == minor;
+            });
+            if (it != m_devices.end()) {
+                (*it).path = move(path);
+            }
+        }
+    };
+
+    fill_in_paths_from_dir("/dev");
+    fill_in_paths_from_dir("/dev/pts");
+
+    did_update();
+}