1 files changed, 72 insertions, 0 deletions
diff --git a/Libraries/LibCompress/Zlib.cpp b/Libraries/LibCompress/Zlib.cpp
new file mode 100644
index 0000000000..7aadc2d5ea
--- /dev/null
+++ b/Libraries/LibCompress/Zlib.cpp
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Span.h>
+#include <AK/Types.h>
+#include <AK/Vector.h>
+#include <LibCompress/Deflate.h>
+#include <LibCompress/Zlib.h>
+
+namespace Compress {
+
+Zlib::Zlib(ReadonlyBytes data)
+{
+    m_input_data = data;
+
+    u8 compression_info = data.at(0);
+    u8 flags = data.at(1);
+
+    m_compression_method = compression_info & 0xF;
+    m_compression_info = (compression_info >> 4) & 0xF;
+    m_check_bits = flags & 0xF;
+    m_has_dictionary = (flags >> 5) & 0x1;
+    m_compression_level = (flags >> 6) & 0x3;
+
+    ASSERT(m_compression_method == 8);
+    ASSERT(m_compression_info == 7);
+    ASSERT(!m_has_dictionary);
+    ASSERT((compression_info * 256 + flags) % 31 == 0);
+
+    m_data_bytes = data.slice(2, data.size() - 2 - 4);
+}
+
+Vector<u8> Zlib::decompress()
+{
+    return Deflate(m_data_bytes).decompress();
+}
+
+u32 Zlib::checksum()
+{
+    if (!m_checksum) {
+        auto bytes = m_input_data.slice(m_input_data.size() - 4, 4);
+        m_checksum = bytes.at(0) << 24 | bytes.at(1) << 16 | bytes.at(2) << 8 || bytes.at(3);
+    }
+
+    return m_checksum;
+}
+
+}