6 files changed, 80 insertions, 6 deletions
diff --git a/src/Makefile.am b/src/Makefile.am
index d491530ca1..2e297d3dac 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -128,6 +128,7 @@ BITCOIN_CORE_H = \
   core_io.h \
   core_memusage.h \
   cuckoocache.h \
+  flatfile.h \
   fs.h \
   httprpc.h \
   httpserver.h \
@@ -247,6 +248,7 @@ libbitcoin_server_a_SOURCES = \
   chain.cpp \
   checkpoints.cpp \
   consensus/tx_verify.cpp \
+  flatfile.cpp \
   httprpc.cpp \
   httpserver.cpp \
   index/base.cpp \
diff --git a/src/flatfile.cpp b/src/flatfile.cpp
new file mode 100644
index 0000000000..c9ca9aa869
--- /dev/null
+++ b/src/flatfile.cpp
@@ -0,0 +1,23 @@
+// Copyright (c) 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.
+
+#include <stdexcept>
+
+#include <flatfile.h>
+#include <tinyformat.h>
+
+FlatFileSeq::FlatFileSeq(fs::path dir, const char* prefix, size_t chunk_size) :
+    m_dir(std::move(dir)),
+    m_prefix(prefix),
+    m_chunk_size(chunk_size)
+{
+    if (chunk_size == 0) {
+        throw std::invalid_argument("chunk_size must be positive");
+    }
+}
+
+fs::path FlatFileSeq::FileName(const CDiskBlockPos& pos) const
+{
+    return m_dir / strprintf("%s%05u.dat", m_prefix, pos.nFile);
+}
diff --git a/src/flatfile.h b/src/flatfile.h
new file mode 100644
index 0000000000..9c7131d201
--- /dev/null
+++ b/src/flatfile.h
@@ -0,0 +1,36 @@
+// Copyright (c) 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 <chain.h>
+#include <fs.h>
+
+/**
+ * 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 CDiskBlockPos& pos) const;
+};
+
+#endif // BITCOIN_FLATFILE_H
diff --git a/src/init.cpp b/src/init.cpp
index 5111baddd2..66c5995651 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -673,7 +673,7 @@ static void ThreadImport(std::vector<fs::path> vImportFiles)
         int nFile = 0;
         while (true) {
             CDiskBlockPos pos(nFile, 0);
-            if (!fs::exists(GetBlockPosFilename(pos, "blk")))
+            if (!fs::exists(GetBlockPosFilename(pos)))
                 break; // No block files left to reindex
             FILE *file = OpenBlockFile(pos, true);
             if (!file)
diff --git a/src/validation.cpp b/src/validation.cpp
index 06e0e99290..3abe8b2fa1 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -15,6 +15,7 @@
 #include <consensus/tx_verify.h>
 #include <consensus/validation.h>
 #include <cuckoocache.h>
+#include <flatfile.h>
 #include <hash.h>
 #include <index/txindex.h>
 #include <policy/fees.h>
@@ -318,6 +319,8 @@ static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPr
 static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
 bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
 static FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
+static FlatFileSeq BlockFileSeq();
+static FlatFileSeq UndoFileSeq();
 
 bool CheckFinalTx(const CTransaction &tx, int flags)
 {
@@ -3657,8 +3660,8 @@ void UnlinkPrunedFiles(const std::set<int>& setFilesToPrune)
 {
     for (std::set<int>::iterator it = setFilesToPrune.begin(); it != setFilesToPrune.end(); ++it) {
         CDiskBlockPos pos(*it, 0);
-        fs::remove(GetBlockPosFilename(pos, "blk"));
-        fs::remove(GetBlockPosFilename(pos, "rev"));
+        fs::remove(BlockFileSeq().FileName(pos));
+        fs::remove(UndoFileSeq().FileName(pos));
         LogPrintf("Prune: %s deleted blk/rev (%05u)\n", __func__, *it);
     }
 }
@@ -3789,6 +3792,16 @@ static FILE* OpenDiskFile(const CDiskBlockPos &pos, const char *prefix, bool fRe
     return file;
 }
 
+static FlatFileSeq BlockFileSeq()
+{
+    return FlatFileSeq(GetBlocksDir(), "blk", BLOCKFILE_CHUNK_SIZE);
+}
+
+static FlatFileSeq UndoFileSeq()
+{
+    return FlatFileSeq(GetBlocksDir(), "rev", UNDOFILE_CHUNK_SIZE);
+}
+
 FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly) {
     return OpenDiskFile(pos, "blk", fReadOnly);
 }
@@ -3798,9 +3811,9 @@ static FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly) {
     return OpenDiskFile(pos, "rev", fReadOnly);
 }
 
-fs::path GetBlockPosFilename(const CDiskBlockPos &pos, const char *prefix)
+fs::path GetBlockPosFilename(const CDiskBlockPos &pos)
 {
-    return GetBlocksDir() / strprintf("%s%05u.dat", prefix, pos.nFile);
+    return BlockFileSeq().FileName(pos);
 }
 
 CBlockIndex * CChainState::InsertBlockIndex(const uint256& hash)
diff --git a/src/validation.h b/src/validation.h
index 1beee7869f..19f8e8ab7a 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -245,7 +245,7 @@ bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& block, CValidationS
 /** Open a block file (blk?????.dat) */
 FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly = false);
 /** Translation to a filesystem path */
-fs::path GetBlockPosFilename(const CDiskBlockPos &pos, const char *prefix);
+fs::path GetBlockPosFilename(const CDiskBlockPos &pos);
 /** Import blocks from an external file */
 bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskBlockPos *dbp = nullptr);
 /** Ensures we have a genesis block in the block tree, possibly writing one to disk. */