LibCore: Add support for ReadonlyBytes to MemoryStream

Meta/Lagom/Fuzzers/FuzzBrotli.cpp

@@ -10,7 +10,7 @@
 
 extern "C" int LLVMFuzzerTestOneInput(uint8_t const* data, size_t size)
 {
-    auto bufstream_result = Core::Stream::MemoryStream::construct({ const_cast<uint8_t*>(data), size });
+    auto bufstream_result = Core::Stream::MemoryStream::construct({ data, size });
     if (bufstream_result.is_error()) {
         dbgln("MemoryStream::construct() failed.");
         return 1;

Meta/Lagom/Fuzzers/FuzzTar.cpp

@@ -12,8 +12,7 @@
 
 extern "C" int LLVMFuzzerTestOneInput(uint8_t const* data, size_t size)
 {
-    // FIXME: Create a ReadonlyBytes variant of Core::Stream::MemoryStream.
-    auto input_stream_or_error = Core::Stream::MemoryStream::construct(Bytes { const_cast<uint8_t*>(data), size });
+    auto input_stream_or_error = Core::Stream::MemoryStream::construct({ data, size });
 
     if (input_stream_or_error.is_error())
         return 0;

Userland/Libraries/LibCore/MemoryStream.h

@@ -22,6 +22,11 @@ public:
         return adopt_nonnull_own_or_enomem<MemoryStream>(new (nothrow) MemoryStream(bytes));
     }
 
+    static ErrorOr<NonnullOwnPtr<MemoryStream>> construct(ReadonlyBytes bytes)
+    {
+        return adopt_nonnull_own_or_enomem<MemoryStream>(new (nothrow) MemoryStream(bytes));
+    }
+
     virtual bool is_eof() const override { return m_offset >= m_bytes.size(); }
     virtual bool is_open() const override { return true; }
     // FIXME: It doesn't make sense to close an memory stream. Therefore, we don't do anything here. Is that fine?
@@ -67,6 +72,8 @@ public:
 
     virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override
     {
+        VERIFY(m_writing_enabled);
+
         // FIXME: Can this not error?
         auto const nwritten = bytes.copy_trimmed_to(m_bytes.slice(m_offset));
         m_offset += nwritten;
@@ -81,7 +88,11 @@ public:
         return true;
     }
 
-    Bytes bytes() { return m_bytes; }
+    Bytes bytes()
+    {
+        VERIFY(m_writing_enabled);
+        return m_bytes;
+    }
     ReadonlyBytes bytes() const { return m_bytes; }
     size_t offset() const { return m_offset; }
     size_t remaining() const { return m_bytes.size() - m_offset; }
@@ -92,9 +103,16 @@ protected:
     {
     }
 
+    explicit MemoryStream(ReadonlyBytes bytes)
+        : m_bytes({ const_cast<u8*>(bytes.data()), bytes.size() })
+        , m_writing_enabled(false)
+    {
+    }
+
 private:
     Bytes m_bytes;
     size_t m_offset { 0 };
+    bool m_writing_enabled { true };
 };
 
 }

Userland/Libraries/LibHTTP/Job.cpp

@@ -78,8 +78,7 @@ static Optional<ByteBuffer> handle_content_encoding(ByteBuffer const& buf, Strin
     } else if (content_encoding == "br") {
         dbgln_if(JOB_DEBUG, "Job::handle_content_encoding: buf is brotli compressed!");
 
-        // FIXME: MemoryStream is both read and write, however we only need the read part here
-        auto bufstream_result = Core::Stream::MemoryStream::construct({ const_cast<u8*>(buf.data()), buf.size() });
+        auto bufstream_result = Core::Stream::MemoryStream::construct({ buf.data(), buf.size() });
         if (bufstream_result.is_error()) {
             dbgln("Job::handle_content_encoding: MemoryStream::construct() failed.");
             return {};