1 files changed, 96 insertions, 0 deletions
diff --git a/src/flatfile.h b/src/flatfile.h
new file mode 100644
index 0000000000..374ceff411
--- /dev/null
+++ b/src/flatfile.h
@@ -0,0 +1,96 @@
+// Copyright (c) 2009-2010 Satoshi Nakamoto
+// Copyright (c) 2009-2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_FLATFILE_H
+#define BITCOIN_FLATFILE_H
+
+#include <string>
+
+#include <fs.h>
+#include <serialize.h>
+
+struct FlatFilePos
+{
+    int nFile;
+    unsigned int nPos;
+
+    ADD_SERIALIZE_METHODS;
+
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action) {
+        READWRITE(VARINT(nFile, VarIntMode::NONNEGATIVE_SIGNED));
+        READWRITE(VARINT(nPos));
+    }
+
+    FlatFilePos() : nFile(-1), nPos(0) {}
+
+    FlatFilePos(int nFileIn, unsigned int nPosIn) :
+        nFile(nFileIn),
+        nPos(nPosIn)
+    {}
+
+    friend bool operator==(const FlatFilePos &a, const FlatFilePos &b) {
+        return (a.nFile == b.nFile && a.nPos == b.nPos);
+    }
+
+    friend bool operator!=(const FlatFilePos &a, const FlatFilePos &b) {
+        return !(a == b);
+    }
+
+    void SetNull() { nFile = -1; nPos = 0; }
+    bool IsNull() const { return (nFile == -1); }
+
+    std::string ToString() const;
+};
+
+/**
+ * FlatFileSeq represents a sequence of numbered files storing raw data. This class facilitates
+ * access to and efficient management of these files.
+ */
+class FlatFileSeq
+{
+private:
+    const fs::path m_dir;
+    const char* const m_prefix;
+    const size_t m_chunk_size;
+
+public:
+    /**
+     * Constructor
+     *
+     * @param dir The base directory that all files live in.
+     * @param prefix A short prefix given to all file names.
+     * @param chunk_size Disk space is pre-allocated in multiples of this amount.
+     */
+    FlatFileSeq(fs::path dir, const char* prefix, size_t chunk_size);
+
+    /** Get the name of the file at the given position. */
+    fs::path FileName(const FlatFilePos& pos) const;
+
+    /** Open a handle to the file at the given position. */
+    FILE* Open(const FlatFilePos& pos, bool read_only = false);
+
+    /**
+     * Allocate additional space in a file after the given starting position. The amount allocated
+     * will be the minimum multiple of the sequence chunk size greater than add_size.
+     *
+     * @param[in] pos The starting position that bytes will be allocated after.
+     * @param[in] add_size The minimum number of bytes to be allocated.
+     * @param[out] out_of_space Whether the allocation failed due to insufficient disk space.
+     * @return The number of bytes successfully allocated.
+     */
+    size_t Allocate(const FlatFilePos& pos, size_t add_size, bool& out_of_space);
+
+    /**
+     * Commit a file to disk, and optionally truncate off extra pre-allocated bytes if final.
+     *
+     * @param[in] pos The first unwritten position in the file to be flushed.
+     * @param[in] finalize True if no more data will be written to this file.
+     * @return true on success, false on failure.
+     */
+    bool Flush(const FlatFilePos& pos, bool finalize = false);
+};
+
+#endif // BITCOIN_FLATFILE_H