VFS: Add a size() method to inodes to implement seeking to the end of a file

kernel/src/fs/VFS.h

@@ -28,6 +28,8 @@ namespace VFS
 
         virtual Result<void> truncate(usize size) = 0;
 
+        virtual usize size() = 0;
+
         // Generic methods
         virtual FileSystem& fs() const = 0;
 

kernel/src/fs/tmpfs/FileSystem.cpp

@@ -129,4 +129,9 @@ namespace TmpFS
 
         return {};
     }
+
+    usize FileInode::size()
+    {
+        return m_data_buffer.size();
+    }
 }

kernel/src/fs/tmpfs/FileSystem.h

@@ -65,6 +65,8 @@ namespace TmpFS
 
         Result<void> truncate(usize size) override;
 
+        usize size() override;
+
         virtual ~FileInode() = default;
 
       private:
@@ -110,6 +112,11 @@ namespace TmpFS
             return err(EISDIR);
         }
 
+        usize size() override
+        {
+            return 0;
+        }
+
         VFS::FileSystem& fs() const override
         {
             return *m_fs;

kernel/src/sys/file.cpp

@@ -42,7 +42,7 @@ Result<u64> sys_write(Registers*, SyscallArgs args)
 
     if (!descriptor.is_writable()) return err(EBADF);
 
-    if (descriptor.should_append()) todo();
+    if (descriptor.should_append()) descriptor.offset = descriptor.inode->size();
 
     usize nwritten = TRY(descriptor.inode->write(buf, descriptor.offset, size));
 
@@ -67,7 +67,7 @@ Result<u64> sys_lseek(Registers*, SyscallArgs args)
     {
     case SEEK_SET: new_offset = offset; break;
     case SEEK_CUR: new_offset = TRY(safe_add((long)descriptor.offset, offset)); break;
-    case SEEK_END: todo();
+    case SEEK_END: new_offset = TRY(safe_add((long)descriptor.inode->size(), offset)); break;
     default: return err(EINVAL);
     }