LibCompress: Switch `DeflateDecompressor` to a fallible constructor

We don't have anything fallible in there yet, but we will soon switch
the seekback buffer to the new `CircularBuffer`, which has a fallible
constructor.

We have to do the same for the internal `GzipDecompressor::Member`
class, as it needs to construct a `DeflateCompressor` from its received
stream.

Userland/Libraries/LibCompress/Deflate.cpp

@@ -189,6 +189,11 @@ ErrorOr<bool> DeflateDecompressor::UncompressedBlock::try_read_more()
     return true;
 }
 
+ErrorOr<NonnullOwnPtr<DeflateDecompressor>> DeflateDecompressor::construct(Core::Stream::Handle<Core::Stream::Stream> stream)
+{
+    return TRY(adopt_nonnull_own_or_enomem(new (nothrow) DeflateDecompressor(move(stream))));
+}
+
 DeflateDecompressor::DeflateDecompressor(Core::Stream::Handle<Core::Stream::Stream> stream)
     : m_input_stream(make<Core::Stream::LittleEndianInputBitStream>(move(stream)))
 {
@@ -311,12 +316,12 @@ void DeflateDecompressor::close()
 ErrorOr<ByteBuffer> DeflateDecompressor::decompress_all(ReadonlyBytes bytes)
 {
     auto memory_stream = TRY(Core::Stream::FixedMemoryStream::construct(bytes));
-    DeflateDecompressor deflate_stream { move(memory_stream) };
+    auto deflate_stream = TRY(DeflateDecompressor::construct(move(memory_stream)));
     DuplexMemoryStream output_stream;
 
     auto buffer = TRY(ByteBuffer::create_uninitialized(4096));
-    while (!deflate_stream.is_eof()) {
-        auto const slice = TRY(deflate_stream.read(buffer));
+    while (!deflate_stream->is_eof()) {
+        auto const slice = TRY(deflate_stream->read(buffer));
         output_stream.write_or_error(slice);
     }
 

Userland/Libraries/LibCompress/Deflate.h

@@ -76,7 +76,7 @@ public:
     friend CompressedBlock;
     friend UncompressedBlock;
 
-    DeflateDecompressor(Core::Stream::Handle<Core::Stream::Stream> stream);
+    static ErrorOr<NonnullOwnPtr<DeflateDecompressor>> construct(Core::Stream::Handle<Core::Stream::Stream> stream);
     ~DeflateDecompressor();
 
     virtual ErrorOr<Bytes> read(Bytes) override;
@@ -88,6 +88,8 @@ public:
     static ErrorOr<ByteBuffer> decompress_all(ReadonlyBytes);
 
 private:
+    DeflateDecompressor(Core::Stream::Handle<Core::Stream::Stream> stream);
+
     ErrorOr<u32> decode_length(u32);
     ErrorOr<u32> decode_distance(u32);
     ErrorOr<void> decode_codes(CanonicalCode& literal_code, Optional<CanonicalCode>& distance_code);

Userland/Libraries/LibCompress/Gzip.cpp

@@ -39,6 +39,18 @@ bool BlockHeader::supported_by_implementation() const
     return true;
 }
 
+ErrorOr<NonnullOwnPtr<GzipDecompressor::Member>> GzipDecompressor::Member::construct(BlockHeader header, Core::Stream::Stream& stream)
+{
+    auto deflate_stream = TRY(DeflateDecompressor::construct(Core::Stream::Handle<Core::Stream::Stream>(stream)));
+    return TRY(adopt_nonnull_own_or_enomem(new (nothrow) Member(header, move(deflate_stream))));
+}
+
+GzipDecompressor::Member::Member(BlockHeader header, NonnullOwnPtr<DeflateDecompressor> stream)
+    : m_header(header)
+    , m_stream(move(stream))
+{
+}
+
 GzipDecompressor::GzipDecompressor(NonnullOwnPtr<Core::Stream::Stream> stream)
     : m_input_stream(move(stream))
 {
@@ -58,8 +70,8 @@ ErrorOr<Bytes> GzipDecompressor::read(Bytes bytes)
 
         auto slice = bytes.slice(total_read);
 
-        if (m_current_member.has_value()) {
-            auto current_slice = TRY(current_member().m_stream.read(slice));
+        if (m_current_member) {
+            auto current_slice = TRY(current_member().m_stream->read(slice));
             current_member().m_checksum.update(current_slice);
             current_member().m_nread += current_slice.size();
 
@@ -131,7 +143,7 @@ ErrorOr<Bytes> GzipDecompressor::read(Bytes bytes)
                 // FIXME: we should probably verify this instead of just assuming it matches
             }
 
-            m_current_member.emplace(header, *m_input_stream);
+            m_current_member = TRY(Member::construct(header, *m_input_stream));
             continue;
         }
     }

Userland/Libraries/LibCompress/Gzip.h

@@ -56,25 +56,24 @@ public:
 private:
     class Member {
     public:
-        Member(BlockHeader header, Core::Stream::Stream& stream)
-            : m_header(header)
-            , m_stream(Core::Stream::Handle<Core::Stream::Stream>(stream))
-        {
-        }
+        static ErrorOr<NonnullOwnPtr<Member>> construct(BlockHeader header, Core::Stream::Stream&);
 
         BlockHeader m_header;
-        DeflateDecompressor m_stream;
+        NonnullOwnPtr<DeflateDecompressor> m_stream;
         Crypto::Checksum::CRC32 m_checksum;
         size_t m_nread { 0 };
+
+    private:
+        Member(BlockHeader, NonnullOwnPtr<DeflateDecompressor>);
     };
 
-    Member const& current_member() const { return m_current_member.value(); }
-    Member& current_member() { return m_current_member.value(); }
+    Member const& current_member() const { return *m_current_member; }
+    Member& current_member() { return *m_current_member; }
 
     NonnullOwnPtr<Core::Stream::Stream> m_input_stream;
     u8 m_partial_header[sizeof(BlockHeader)];
     size_t m_partial_header_offset { 0 };
-    Optional<Member> m_current_member;
+    OwnPtr<Member> m_current_member {};
 
     bool m_eof { false };
 };