From e9feced041e1855327a01c2905a7353031ceaa91 Mon Sep 17 00:00:00 2001
From: Ali Mohammad Pur <ali.mpfard@gmail.com>
Date: Mon, 16 Aug 2021 06:32:48 +0430
Subject: [PATCH] Kernel: Add a Process::FileDescriptions::get_if_valid(index)
 API

Note that this is not the same as ::at(index), which has a different
precondition ("allocated" vs "valid").
---
 Kernel/Process.cpp | 23 +++++++++++++++++++++++
 Kernel/Process.h   |  3 +++
 2 files changed, 26 insertions(+)

diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index a3ad914a69..f197cb4f92 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -428,6 +428,29 @@ RefPtr<Process> Process::from_pid(ProcessID pid)
     });
 }
 
+const Process::FileDescriptionAndFlags* Process::FileDescriptions::get_if_valid(size_t i) const
+{
+    ScopedSpinLock lock(m_fds_lock);
+    if (m_fds_metadatas.size() <= i)
+        return nullptr;
+
+    if (auto& metadata = m_fds_metadatas[i]; metadata.is_valid())
+        return &metadata;
+
+    return nullptr;
+}
+Process::FileDescriptionAndFlags* Process::FileDescriptions::get_if_valid(size_t i)
+{
+    ScopedSpinLock lock(m_fds_lock);
+    if (m_fds_metadatas.size() <= i)
+        return nullptr;
+
+    if (auto& metadata = m_fds_metadatas[i]; metadata.is_valid())
+        return &metadata;
+
+    return nullptr;
+}
+
 const Process::FileDescriptionAndFlags& Process::FileDescriptions::at(size_t i) const
 {
     ScopedSpinLock lock(m_fds_lock);
diff --git a/Kernel/Process.h b/Kernel/Process.h
index a5d1bc9c1c..6c0d57b58c 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -643,6 +643,9 @@ public:
         const FileDescriptionAndFlags& at(size_t i) const;
         FileDescriptionAndFlags& at(size_t i);
 
+        FileDescriptionAndFlags const* get_if_valid(size_t i) const;
+        FileDescriptionAndFlags* get_if_valid(size_t i);
+
         void enumerate(Function<void(const FileDescriptionAndFlags&)>) const;
         void change_each(Function<void(FileDescriptionAndFlags&)>);