LibCompress: Implement gzip.

Libraries/LibCompress/Gzip.cpp

@@ -0,0 +1,186 @@
+/*
+ * 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 <LibCompress/Gzip.h>
+
+#include <AK/String.h>
+
+namespace Compress {
+
+bool GzipDecompressor::BlockHeader::valid_magic_number() const
+{
+    return identification_1 == 0x1f && identification_2 == 0x8b;
+}
+
+bool GzipDecompressor::BlockHeader::supported_by_implementation() const
+{
+    if (compression_method != 0x08) {
+        // RFC 1952 does not define any compression methods other than deflate.
+        return false;
+    }
+
+    if (flags > Flags::MAX) {
+        // RFC 1952 does not define any more flags.
+        return false;
+    }
+
+    if (flags & Flags::FHCRC) {
+        TODO();
+    }
+
+    return true;
+}
+
+GzipDecompressor::GzipDecompressor(InputStream& stream)
+    : m_input_stream(stream)
+{
+}
+
+GzipDecompressor::~GzipDecompressor()
+{
+    m_current_member.clear();
+}
+
+// FIXME: Again, there are surely a ton of bugs because the code doesn't check for read errors.
+size_t GzipDecompressor::read(Bytes bytes)
+{
+    if (m_current_member.has_value()) {
+        size_t nread = current_member().m_stream.read(bytes);
+        current_member().m_checksum.update(bytes.trim(nread));
+        current_member().m_nread += nread;
+
+        if (nread < bytes.size()) {
+            LittleEndian<u32> crc32, input_size;
+            m_input_stream >> crc32 >> input_size;
+
+            if (crc32 != current_member().m_checksum.digest()) {
+                m_error = true;
+                return 0;
+            }
+
+            if (input_size != current_member().m_nread) {
+                m_error = true;
+                return 0;
+            }
+
+            m_current_member.clear();
+
+            return nread + read(bytes.slice(nread));
+        }
+
+        return nread;
+    } else {
+        if (m_input_stream.eof())
+            return 0;
+
+        // FIXME: This fails with the new changes?
+        BlockHeader header;
+        m_input_stream >> Bytes { &header, sizeof(header) };
+
+        if (!header.valid_magic_number() || !header.supported_by_implementation()) {
+            m_error = true;
+            return 0;
+        }
+
+        if (header.flags & Flags::FEXTRA) {
+            LittleEndian<u16> subfield_id, length;
+            m_input_stream >> subfield_id >> length;
+            m_input_stream.discard_or_error(length);
+        }
+
+        if (header.flags & Flags::FNAME) {
+            String original_filename;
+            m_input_stream >> original_filename;
+        }
+
+        if (header.flags & Flags::FCOMMENT) {
+            String comment;
+            m_input_stream >> comment;
+        }
+
+        m_current_member.emplace(header, m_input_stream);
+        return read(bytes);
+    }
+}
+
+bool GzipDecompressor::read_or_error(Bytes bytes)
+{
+    if (read(bytes) < bytes.size()) {
+        m_error = true;
+        return false;
+    }
+
+    return true;
+}
+
+bool GzipDecompressor::discard_or_error(size_t count)
+{
+    u8 buffer[4096];
+
+    size_t ndiscarded = 0;
+    while (ndiscarded < count) {
+        if (eof()) {
+            m_error = true;
+            return false;
+        }
+
+        ndiscarded += read({ buffer, min<size_t>(count - ndiscarded, sizeof(buffer)) });
+    }
+
+    return true;
+}
+
+ByteBuffer GzipDecompressor::decompress_all(ReadonlyBytes bytes)
+{
+    InputMemoryStream memory_stream { bytes };
+    GzipDecompressor gzip_stream { memory_stream };
+
+    auto buffer = ByteBuffer::create_uninitialized(4096);
+
+    size_t nread = 0;
+    while (!gzip_stream.eof()) {
+        nread += gzip_stream.read(buffer.bytes().slice(nread));
+
+        if (buffer.size() - nread < 4096)
+            buffer.grow(buffer.size() + 4096);
+    }
+
+    buffer.trim(nread);
+    return buffer;
+}
+
+bool GzipDecompressor::eof() const
+{
+    if (m_current_member.has_value()) {
+        // FIXME: There is an ugly edge case where we read the whole deflate block
+        //        but haven't read CRC32 and ISIZE.
+        return current_member().m_stream.eof() && m_input_stream.eof();
+    } else {
+        return m_input_stream.eof();
+    }
+}
+
+}