AK: Make SeekableStream::truncate() take a size_t

Similar to the return values earlier, a signed value doesn't really make
sense here. Relying on the much more standard `size_t` makes it easier
to use Stream in all contexts.

AK/BufferedStream.h

@@ -295,7 +295,7 @@ public:
 
         return result;
     }
-    virtual ErrorOr<void> truncate(off_t length) override
+    virtual ErrorOr<void> truncate(size_t length) override
     {
         return m_helper.stream().truncate(length);
     }

AK/MemoryStream.cpp

@@ -48,7 +48,7 @@ void FixedMemoryStream::close()
     // FIXME: It doesn't make sense to close a memory stream. Therefore, we don't do anything here. Is that fine?
 }
 
-ErrorOr<void> FixedMemoryStream::truncate(off_t)
+ErrorOr<void> FixedMemoryStream::truncate(size_t)
 {
     return Error::from_errno(EBADF);
 }

AK/MemoryStream.h

@@ -22,7 +22,7 @@ public:
     virtual bool is_eof() const override;
     virtual bool is_open() const override;
     virtual void close() override;
-    virtual ErrorOr<void> truncate(off_t) override;
+    virtual ErrorOr<void> truncate(size_t) override;
     virtual ErrorOr<Bytes> read(Bytes bytes) override;
 
     virtual ErrorOr<size_t> seek(i64 offset, SeekMode seek_mode = SeekMode::SetPosition) override;

AK/Stream.h

@@ -120,7 +120,7 @@ public:
     virtual ErrorOr<size_t> size();
     /// Shrinks or extends the stream to the given size. Returns an errno in
     /// the case of an error.
-    virtual ErrorOr<void> truncate(off_t length) = 0;
+    virtual ErrorOr<void> truncate(size_t length) = 0;
     /// Seeks until after the given amount of bytes to be discarded instead of
     /// reading and discarding everything manually;
     virtual ErrorOr<void> discard(size_t discarded_bytes) override;

Userland/Libraries/LibCore/Stream.cpp

@@ -184,8 +184,11 @@ ErrorOr<size_t> File::seek(i64 offset, SeekMode mode)
     return seek_result;
 }
 
-ErrorOr<void> File::truncate(off_t length)
+ErrorOr<void> File::truncate(size_t length)
 {
+    if (length > static_cast<size_t>(NumericLimits<off_t>::max()))
+        return Error::from_string_literal("Length is larger than the maximum supported length");
+
     return System::ftruncate(m_fd, length);
 }
 

Userland/Libraries/LibCore/Stream.h

@@ -169,7 +169,7 @@ public:
     virtual bool is_open() const override;
     virtual void close() override;
     virtual ErrorOr<size_t> seek(i64 offset, SeekMode) override;
-    virtual ErrorOr<void> truncate(off_t length) override;
+    virtual ErrorOr<void> truncate(size_t length) override;
 
     int leak_fd(Badge<::IPC::File>)
     {