From 8b51499900e125a55dcdc425d29550b98a8064b4 Mon Sep 17 00:00:00 2001
From: Jan Sucan <jan@jansucan.com>
Date: Sat, 18 Jan 2025 07:57:57 +0100
Subject: Initial implementation of diff file format v2

---
 src/format_v2.h | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 src/format_v2.h

(limited to 'src/format_v2.h')

diff --git a/src/format_v2.h b/src/format_v2.h
new file mode 100644
index 0000000..708a252
--- /dev/null
+++ b/src/format_v2.h
@@ -0,0 +1,119 @@
+/* Copyright 2024 Ján Sučan <jan@jansucan.com>
+ *
+ * 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 <endian.h>
+
+#include <vector>
+
+namespace FormatV2
+{
+
+const size_t RecordHeaderSize{sizeof(uint64_t) + sizeof(uint32_t)};
+
+struct RecordData {
+    size_t size;
+    std::shared_ptr<char[]> data;
+};
+
+class Writer
+{
+  public:
+    Writer(std::ostream &ostream, size_t buffer_size)
+        : m_writer{BufferedFileWriter{ostream, buffer_size}} {};
+
+    void writeDiffRecord(
+        uint64_t offset, size_t size,
+        std::vector<RecordData> data) // cppcheck-suppress passedByValue
+    {
+        writeOffset(offset);
+        writeSize(size);
+        for (auto it = data.begin(); it != data.end(); ++it) {
+            writeData(*it);
+        }
+    }
+
+  private:
+    BufferedFileWriter m_writer;
+
+    void writeOffset(uint64_t offset)
+    {
+        uint64_t val{htobe64(offset)};
+        m_writer.write(reinterpret_cast<char *>(&val), sizeof(val));
+    };
+
+    void writeSize(size_t size)
+    {
+        uint32_t val{htobe32(size)};
+        m_writer.write(reinterpret_cast<char *>(&val), sizeof(val));
+    };
+
+    void writeData(RecordData data)
+    {
+        m_writer.write(reinterpret_cast<char *>(data.data.get()), data.size);
+    };
+};
+
+class Reader
+{
+  public:
+    Reader(std::istream &istream, size_t buffer_size)
+        : m_reader{BufferedFileReader{istream, buffer_size}}, m_eof{false} {};
+
+    bool eof() { return m_eof; };
+
+    uint64_t readOffset()
+    {
+        uint64_t raw_offset;
+        const size_t r{m_reader.read(reinterpret_cast<char *>(&raw_offset),
+                                     sizeof(raw_offset))};
+        if (r != sizeof(raw_offset)) {
+            m_eof = true;
+        }
+        return be64toh(raw_offset);
+    };
+
+    size_t readSize()
+    {
+        uint32_t raw_size;
+        const size_t r{m_reader.read(reinterpret_cast<char *>(&raw_size),
+                                     sizeof(raw_size))};
+        if (r != sizeof(raw_size)) {
+            m_eof = true;
+        }
+        return be32toh(raw_size);
+    };
+
+    size_t readData(size_t size, char **return_data)
+    {
+        return m_reader.tryRead(size, return_data);
+    };
+
+  private:
+    BufferedFileReader m_reader;
+    bool m_eof;
+};
+
+} // namespace FormatV2
-- 
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