ProcessManager: Add a new per-proces "open files" view showing open FDs

This uses the data from /proc/PID/fds with ease now that it's JSON. :^)

Applications/ProcessManager/ProcessFileDescriptorMapModel.cpp

@@ -0,0 +1,74 @@
+#include "ProcessFileDescriptorMapModel.h"
+#include <AK/JsonObject.h>
+#include <AK/StringBuilder.h>
+#include <LibCore/CFile.h>
+
+void ProcessFileDescriptorMapModel::update()
+{
+    CFile file(String::format("/proc/%d/fds", m_pid));
+    if (!file.open(CIODevice::ReadOnly)) {
+        dbg() << "Unable to open " << file.filename();
+        return;
+    }
+
+    auto json = JsonValue::from_string(file.read_all());
+
+    ASSERT(json.is_array());
+    m_process_fds = json.as_array();
+
+    did_update();
+}
+
+int ProcessFileDescriptorMapModel::row_count(const GModelIndex&) const
+{
+    return m_process_fds.size();
+}
+
+String ProcessFileDescriptorMapModel::column_name(int column) const
+{
+    switch (column) {
+    case Column::FileDescriptor:
+        return "FD";
+    case Column::Path:
+        return "Path";
+    default:
+        ASSERT_NOT_REACHED();
+    }
+}
+
+GModel::ColumnMetadata ProcessFileDescriptorMapModel::column_metadata(int column) const
+{
+    switch (column) {
+    case Column::FileDescriptor:
+        return { 32, TextAlignment::CenterRight };
+    case Column::Path:
+        return { 300, TextAlignment::CenterLeft };
+    default:
+        ASSERT_NOT_REACHED();
+    }
+    return {};
+}
+
+GVariant ProcessFileDescriptorMapModel::data(const GModelIndex& index, Role role) const
+{
+    auto& fd_object = m_process_fds.at(index.row()).as_object();
+    if (role == GModel::Role::Display) {
+        switch (index.column()) {
+        case Column::FileDescriptor:
+            return fd_object.get("fd").to_int();
+        case Column::Path:
+            return fd_object.get("absolute_path").to_string();
+        default:
+            ASSERT_NOT_REACHED();
+        }
+    }
+    return {};
+}
+
+void ProcessFileDescriptorMapModel::set_pid(pid_t pid)
+{
+    if (m_pid == pid)
+        return;
+    m_pid = pid;
+    update();
+}