Switch to bitstream writer

Author: rustaceanrob

src/swiftsync.cpp

@@ -17,6 +17,17 @@
 
 using namespace swiftsync;
 
+void BitsWriter::WriteBitInternal(uint8_t is_not_spent) noexcept
+{
+    m_curr_byte <<= 1;
+    m_curr_byte |= (is_not_spent & 0x01);
+    ++m_bits_written;
+    if (m_bits_written % 8 == 0) {
+        m_hints.push_back(m_curr_byte);
+        m_curr_byte = 0;
+    }
+}
+
 HintsfileWriter::HintsfileWriter(AutoFile& file, const uint32_t& preallocate) : m_file(file.release())
 {
     uint64_t dummy_file_pos{};
@@ -29,7 +40,7 @@ HintsfileWriter::HintsfileWriter(AutoFile& file, const uint32_t& preallocate) :
     }
 }
 
-bool HintsfileWriter::WriteNextUnspents(const std::vector<uint64_t>& unspent_offsets, const uint32_t& height)
+bool HintsfileWriter::WriteNextUnspents(BitsWriter& writer, const uint32_t& height)
 {
     // First write the current file position for the current height in the header section.
     uint64_t curr_pos = m_file.size();
@@ -39,10 +50,7 @@ bool HintsfileWriter::WriteNextUnspents(const std::vector<uint64_t>& unspent_off
     m_file << curr_pos;
     // Next append the positions of the unspent offsets in the block at this height.
     m_file.seek(curr_pos, SEEK_SET);
-    WriteCompactSize(m_file, unspent_offsets.size());
-    for (const auto& offset : unspent_offsets) {
-        WriteCompactSize(m_file, offset);
-    }
+    writer.EncodeToStream(m_file);
     ++m_index;
     return m_file.Commit();
 }

src/swiftsync.h

@@ -7,11 +7,11 @@
 #include <primitives/transaction.h>
 #include <streams.h>
 #include <uint256.h>
+#include <util/fs.h>
 #include <util/hasher.h>
 #include <array>
 #include <cstdint>
 #include <unordered_map>
-#include <util/fs.h>
 #include <vector>
 
 namespace swiftsync {
@@ -39,6 +39,24 @@ class Aggregate
     void Spend(const COutPoint& outpoint) { m_spent += m_hasher(outpoint); }
 };
 
+class BitsWriter
+{
+private:
+    std::vector<uint8_t> m_hints{};
+    uint8_t m_curr_byte{};
+    uint32_t m_bits_written{};
+    void WriteBitInternal(uint8_t bit) noexcept;
+
+public:
+    void PushHighBit() noexcept { return WriteBitInternal(0x01); }
+    void PushLowBit() noexcept { return WriteBitInternal(0x00); }
+    void EncodeToStream(AutoFile& file)
+    {
+        file << m_bits_written;
+        file << m_hints;
+    };
+};
+
 /**
  * Create a new hint file for writing.
  */
@@ -56,7 +74,7 @@ class HintsfileWriter
         (void)m_file.fclose();
     }
     // Write the next hints to file.
-    bool WriteNextUnspents(const std::vector<uint64_t>& unspent_offsets, const uint32_t& height);
+    bool WriteNextUnspents(BitsWriter& writer, const uint32_t& height);
     // Close the underlying file.
     int Close() { return m_file.fclose(); };
 };