diff --git a/src/streams.h b/src/streams.h
index 51f89cd15..3b651bd14 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -1,859 +1,862 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 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_STREAMS_H
 #define BITCOIN_STREAMS_H
 
 #include <serialize.h>
 #include <support/allocators/zeroafterfree.h>
 
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <cstdio>
 #include <cstring>
 #include <ios>
 #include <limits>
 #include <string>
 #include <utility>
 #include <vector>
 
 template <typename Stream> class OverrideStream {
     Stream *stream;
 
     const int nType;
     const int nVersion;
 
 public:
     OverrideStream(Stream *stream_, int nType_, int nVersion_)
         : stream(stream_), nType(nType_), nVersion(nVersion_) {}
 
     template <typename T> OverrideStream<Stream> &operator<<(const T &obj) {
         // Serialize to this stream
         ::Serialize(*this, obj);
         return (*this);
     }
 
     template <typename T> OverrideStream<Stream> &operator>>(T &&obj) {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
         return (*this);
     }
 
     void write(const char *pch, size_t nSize) { stream->write(pch, nSize); }
 
     void read(char *pch, size_t nSize) { stream->read(pch, nSize); }
 
     int GetVersion() const { return nVersion; }
     int GetType() const { return nType; }
 };
 
 template <typename S> OverrideStream<S> WithOrVersion(S *s, int nVersionFlag) {
     return OverrideStream<S>(s, s->GetType(), s->GetVersion() | nVersionFlag);
 }
 
 /**
  * Minimal stream for overwriting and/or appending to an existing byte vector.
  *
  * The referenced vector will grow as necessary.
  */
 class CVectorWriter {
 public:
     /**
      * @param[in]  nTypeIn Serialization Type
      * @param[in]  nVersionIn Serialization Version (including any flags)
      * @param[in]  vchDataIn  Referenced byte vector to overwrite/append
      * @param[in]  nPosIn Starting position. Vector index where writes should
      * start. The vector will initially grow as necessary to  max(nPosIn,
      * vec.size()). So to append, use vec.size().
      */
     CVectorWriter(int nTypeIn, int nVersionIn, std::vector<uint8_t> &vchDataIn,
                   size_t nPosIn)
         : nType(nTypeIn), nVersion(nVersionIn), vchData(vchDataIn),
           nPos(nPosIn) {
         if (nPos > vchData.size()) {
             vchData.resize(nPos);
         }
     }
     /**
      * (other params same as above)
      * @param[in]  args  A list of items to serialize starting at nPosIn.
      */
     template <typename... Args>
     CVectorWriter(int nTypeIn, int nVersionIn, std::vector<uint8_t> &vchDataIn,
                   size_t nPosIn, Args &&... args)
         : CVectorWriter(nTypeIn, nVersionIn, vchDataIn, nPosIn) {
         ::SerializeMany(*this, std::forward<Args>(args)...);
     }
     void write(const char *pch, size_t nSize) {
         assert(nPos <= vchData.size());
         size_t nOverwrite = std::min(nSize, vchData.size() - nPos);
         if (nOverwrite) {
             memcpy(vchData.data() + nPos,
                    reinterpret_cast<const uint8_t *>(pch), nOverwrite);
         }
         if (nOverwrite < nSize) {
             vchData.insert(vchData.end(),
                            reinterpret_cast<const uint8_t *>(pch) + nOverwrite,
                            reinterpret_cast<const uint8_t *>(pch) + nSize);
         }
         nPos += nSize;
     }
     template <typename T> CVectorWriter &operator<<(const T &obj) {
         // Serialize to this stream
         ::Serialize(*this, obj);
         return (*this);
     }
     int GetVersion() const { return nVersion; }
     int GetType() const { return nType; }
     void seek(size_t nSize) {
         nPos += nSize;
         if (nPos > vchData.size()) {
             vchData.resize(nPos);
         }
     }
 
 private:
     const int nType;
     const int nVersion;
     std::vector<uint8_t> &vchData;
     size_t nPos;
 };
 
 /**
  * Minimal stream for reading from an existing vector by reference
  */
 class VectorReader {
 private:
     const int m_type;
     const int m_version;
     const std::vector<uint8_t> &m_data;
     size_t m_pos = 0;
 
 public:
     /**
      * @param[in]  type Serialization Type
      * @param[in]  version Serialization Version (including any flags)
      * @param[in]  data Referenced byte vector to overwrite/append
      * @param[in]  pos Starting position. Vector index where reads should start.
      */
     VectorReader(int type, int version, const std::vector<uint8_t> &data,
                  size_t pos)
         : m_type(type), m_version(version), m_data(data), m_pos(pos) {
         if (m_pos > m_data.size()) {
             throw std::ios_base::failure(
                 "VectorReader(...): end of data (m_pos > m_data.size())");
         }
     }
 
     /**
      * (other params same as above)
      * @param[in]  args  A list of items to deserialize starting at pos.
      */
     template <typename... Args>
     VectorReader(int type, int version, const std::vector<uint8_t> &data,
                  size_t pos, Args &&... args)
         : VectorReader(type, version, data, pos) {
         ::UnserializeMany(*this, std::forward<Args>(args)...);
     }
 
     template <typename T> VectorReader &operator>>(T &obj) {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
         return (*this);
     }
 
     int GetVersion() const { return m_version; }
     int GetType() const { return m_type; }
 
     size_t size() const { return m_data.size() - m_pos; }
     bool empty() const { return m_data.size() == m_pos; }
 
     void read(char *dst, size_t n) {
         if (n == 0) {
             return;
         }
 
         // Read from the beginning of the buffer
         size_t pos_next = m_pos + n;
         if (pos_next > m_data.size()) {
             throw std::ios_base::failure("VectorReader::read(): end of data");
         }
         memcpy(dst, m_data.data() + m_pos, n);
         m_pos = pos_next;
     }
 };
 
 /**
  * Double ended buffer combining vector and stream-like interfaces.
  *
  * >> and << read and write unformatted data using the above serialization
  * templates. Fills with data in linear time; some stringstream implementations
  * take N^2 time.
  */
 class CDataStream {
 protected:
     typedef CSerializeData vector_type;
     vector_type vch;
     unsigned int nReadPos;
 
     int nType;
     int nVersion;
 
 public:
     typedef vector_type::allocator_type allocator_type;
     typedef vector_type::size_type size_type;
     typedef vector_type::difference_type difference_type;
     typedef vector_type::reference reference;
     typedef vector_type::const_reference const_reference;
     typedef vector_type::value_type value_type;
     typedef vector_type::iterator iterator;
     typedef vector_type::const_iterator const_iterator;
     typedef vector_type::reverse_iterator reverse_iterator;
 
     explicit CDataStream(int nTypeIn, int nVersionIn) {
         Init(nTypeIn, nVersionIn);
     }
 
     CDataStream(const_iterator pbegin, const_iterator pend, int nTypeIn,
                 int nVersionIn)
         : vch(pbegin, pend) {
         Init(nTypeIn, nVersionIn);
     }
 
     CDataStream(const char *pbegin, const char *pend, int nTypeIn,
                 int nVersionIn)
         : vch(pbegin, pend) {
         Init(nTypeIn, nVersionIn);
     }
 
     CDataStream(const vector_type &vchIn, int nTypeIn, int nVersionIn)
         : vch(vchIn.begin(), vchIn.end()) {
         Init(nTypeIn, nVersionIn);
     }
 
     CDataStream(const std::vector<char> &vchIn, int nTypeIn, int nVersionIn)
         : vch(vchIn.begin(), vchIn.end()) {
         Init(nTypeIn, nVersionIn);
     }
 
     CDataStream(const std::vector<uint8_t> &vchIn, int nTypeIn, int nVersionIn)
         : vch(vchIn.begin(), vchIn.end()) {
         Init(nTypeIn, nVersionIn);
     }
 
     template <typename... Args>
     CDataStream(int nTypeIn, int nVersionIn, Args &&... args) {
         Init(nTypeIn, nVersionIn);
         ::SerializeMany(*this, std::forward<Args>(args)...);
     }
 
     void Init(int nTypeIn, int nVersionIn) {
         nReadPos = 0;
         nType = nTypeIn;
         nVersion = nVersionIn;
     }
 
     CDataStream &operator+=(const CDataStream &b) {
         vch.insert(vch.end(), b.begin(), b.end());
         return *this;
     }
 
     friend CDataStream operator+(const CDataStream &a, const CDataStream &b) {
         CDataStream ret = a;
         ret += b;
         return (ret);
     }
 
     std::string str() const { return (std::string(begin(), end())); }
 
     //
     // Vector subset
     //
     const_iterator begin() const { return vch.begin() + nReadPos; }
     iterator begin() { return vch.begin() + nReadPos; }
     const_iterator end() const { return vch.end(); }
     iterator end() { return vch.end(); }
     size_type size() const { return vch.size() - nReadPos; }
     bool empty() const { return vch.size() == nReadPos; }
     void resize(size_type n, value_type c = 0) { vch.resize(n + nReadPos, c); }
     void reserve(size_type n) { vch.reserve(n + nReadPos); }
     const_reference operator[](size_type pos) const {
         return vch[pos + nReadPos];
     }
     reference operator[](size_type pos) { return vch[pos + nReadPos]; }
     void clear() {
         vch.clear();
         nReadPos = 0;
     }
     iterator insert(iterator it, const char x = char()) {
         return vch.insert(it, x);
     }
     void insert(iterator it, size_type n, const char x) {
         vch.insert(it, n, x);
     }
     value_type *data() { return vch.data() + nReadPos; }
     const value_type *data() const { return vch.data() + nReadPos; }
 
     void insert(iterator it, std::vector<char>::const_iterator first,
                 std::vector<char>::const_iterator last) {
         if (last == first) {
             return;
         }
 
         assert(last - first > 0);
         if (it == vch.begin() + nReadPos &&
             (unsigned int)(last - first) <= nReadPos) {
             // special case for inserting at the front when there's room
             nReadPos -= (last - first);
             memcpy(&vch[nReadPos], &first[0], last - first);
         } else {
             vch.insert(it, first, last);
         }
     }
 
     void insert(iterator it, const char *first, const char *last) {
         if (last == first) {
             return;
         }
 
         assert(last - first > 0);
         if (it == vch.begin() + nReadPos &&
             (unsigned int)(last - first) <= nReadPos) {
             // special case for inserting at the front when there's room
             nReadPos -= (last - first);
             memcpy(&vch[nReadPos], &first[0], last - first);
         } else {
             vch.insert(it, first, last);
         }
     }
 
     iterator erase(iterator it) {
         if (it == vch.begin() + nReadPos) {
             // special case for erasing from the front
             if (++nReadPos >= vch.size()) {
                 // whenever we reach the end, we take the opportunity to clear
                 // the buffer
                 nReadPos = 0;
                 return vch.erase(vch.begin(), vch.end());
             }
             return vch.begin() + nReadPos;
         } else {
             return vch.erase(it);
         }
     }
 
     iterator erase(iterator first, iterator last) {
         if (first == vch.begin() + nReadPos) {
             // special case for erasing from the front
             if (last == vch.end()) {
                 nReadPos = 0;
                 return vch.erase(vch.begin(), vch.end());
             } else {
                 nReadPos = (last - vch.begin());
                 return last;
             }
         } else
             return vch.erase(first, last);
     }
 
     inline void Compact() {
         vch.erase(vch.begin(), vch.begin() + nReadPos);
         nReadPos = 0;
     }
 
     bool Rewind(size_type n) {
         // Rewind by n characters if the buffer hasn't been compacted yet
         if (n > nReadPos) {
             return false;
         }
         nReadPos -= n;
         return true;
     }
 
     //
     // Stream subset
     //
     bool eof() const { return size() == 0; }
     CDataStream *rdbuf() { return this; }
     int in_avail() const { return size(); }
 
     void SetType(int n) { nType = n; }
     int GetType() const { return nType; }
     void SetVersion(int n) { nVersion = n; }
     int GetVersion() const { return nVersion; }
 
     void read(char *pch, size_t nSize) {
         if (nSize == 0) {
             return;
         }
 
         // Read from the beginning of the buffer
         unsigned int nReadPosNext = nReadPos + nSize;
         if (nReadPosNext > vch.size()) {
             throw std::ios_base::failure("CDataStream::read(): end of data");
         }
         memcpy(pch, &vch[nReadPos], nSize);
         if (nReadPosNext == vch.size()) {
             nReadPos = 0;
             vch.clear();
             return;
         }
         nReadPos = nReadPosNext;
     }
 
     void ignore(int nSize) {
         // Ignore from the beginning of the buffer
         if (nSize < 0) {
             throw std::ios_base::failure(
                 "CDataStream::ignore(): nSize negative");
         }
         unsigned int nReadPosNext = nReadPos + nSize;
         if (nReadPosNext >= vch.size()) {
             if (nReadPosNext > vch.size()) {
                 throw std::ios_base::failure(
                     "CDataStream::ignore(): end of data");
             }
             nReadPos = 0;
             vch.clear();
             return;
         }
         nReadPos = nReadPosNext;
     }
 
     void write(const char *pch, size_t nSize) {
         // Write to the end of the buffer
         vch.insert(vch.end(), pch, pch + nSize);
     }
 
     template <typename Stream> void Serialize(Stream &s) const {
         // Special case: stream << stream concatenates like stream += stream
         if (!vch.empty()) {
             s.write((char *)vch.data(), vch.size() * sizeof(value_type));
         }
     }
 
     template <typename T> CDataStream &operator<<(const T &obj) {
         // Serialize to this stream
         ::Serialize(*this, obj);
         return (*this);
     }
 
     template <typename T> CDataStream &operator>>(T &&obj) {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
         return (*this);
     }
 
     void GetAndClear(CSerializeData &d) {
         d.insert(d.end(), begin(), end());
         clear();
     }
 
     /**
      * XOR the contents of this stream with a certain key.
      *
      * @param[in] key    The key used to XOR the data in this stream.
      */
     void Xor(const std::vector<uint8_t> &key) {
         if (key.size() == 0) {
             return;
         }
 
         for (size_type i = 0, j = 0; i != size(); i++) {
             vch[i] ^= key[j++];
 
             // This potentially acts on very many bytes of data, so it's
             // important that we calculate `j`, i.e. the `key` index in this way
             // instead of doing a %, which would effectively be a division for
             // each byte Xor'd -- much slower than need be.
             if (j == key.size()) j = 0;
         }
     }
 };
 
 template <typename IStream> class BitStreamReader {
 private:
     IStream &m_istream;
 
     /// Buffered byte read in from the input stream. A new byte is read into the
     /// buffer when m_offset reaches 8.
     uint8_t m_buffer{0};
 
     /// Number of high order bits in m_buffer already returned by previous
     /// Read() calls. The next bit to be returned is at this offset from the
     /// most significant bit position.
     int m_offset{8};
 
 public:
     explicit BitStreamReader(IStream &istream) : m_istream(istream) {}
 
     /**
      * Read the specified number of bits from the stream. The data is returned
      * in the nbits least significant bits of a 64-bit uint.
      */
     uint64_t Read(int nbits) {
         if (nbits < 0 || nbits > 64) {
             throw std::out_of_range("nbits must be between 0 and 64");
         }
 
         uint64_t data = 0;
         while (nbits > 0) {
             if (m_offset == 8) {
                 m_istream >> m_buffer;
                 m_offset = 0;
             }
 
             int bits = std::min(8 - m_offset, nbits);
             data <<= bits;
             data |= static_cast<uint8_t>(m_buffer << m_offset) >> (8 - bits);
             m_offset += bits;
             nbits -= bits;
         }
         return data;
     }
 };
 
 template <typename OStream> class BitStreamWriter {
 private:
     OStream &m_ostream;
 
     /// Buffered byte waiting to be written to the output stream. The byte is
     /// written buffer when m_offset reaches 8 or Flush() is called.
     uint8_t m_buffer{0};
 
     /// Number of high order bits in m_buffer already written by previous
     /// Write() calls and not yet flushed to the stream. The next bit to be
     /// written to is at this offset from the most significant bit position.
     int m_offset{0};
 
 public:
     explicit BitStreamWriter(OStream &ostream) : m_ostream(ostream) {}
 
     ~BitStreamWriter() { Flush(); }
 
     /**
      * Write the nbits least significant bits of a 64-bit int to the output
      * stream. Data is buffered until it completes an octet.
      */
     void Write(uint64_t data, int nbits) {
         if (nbits < 0 || nbits > 64) {
             throw std::out_of_range("nbits must be between 0 and 64");
         }
 
         while (nbits > 0) {
             int bits = std::min(8 - m_offset, nbits);
             m_buffer |= (data << (64 - nbits)) >> (64 - 8 + m_offset);
             m_offset += bits;
             nbits -= bits;
 
             if (m_offset == 8) {
                 Flush();
             }
         }
     }
 
     /**
      * Flush any unwritten bits to the output stream, padding with 0's to the
      * next byte boundary.
      */
     void Flush() {
         if (m_offset == 0) {
             return;
         }
 
         m_ostream << m_buffer;
         m_buffer = 0;
         m_offset = 0;
     }
 };
 
 /**
  * Non-refcounted RAII wrapper for FILE*
  *
  * Will automatically close the file when it goes out of scope if not null. If
  * you're returning the file pointer, return file.release(). If you need to
  * close the file early, use file.fclose() instead of fclose(file).
  */
 class CAutoFile {
 private:
     const int nType;
     const int nVersion;
 
     FILE *file;
 
 public:
     CAutoFile(FILE *filenew, int nTypeIn, int nVersionIn)
         : nType(nTypeIn), nVersion(nVersionIn) {
         file = filenew;
     }
 
     ~CAutoFile() { fclose(); }
 
     // Disallow copies
     CAutoFile(const CAutoFile &) = delete;
     CAutoFile &operator=(const CAutoFile &) = delete;
 
     void fclose() {
         if (file) {
             ::fclose(file);
             file = nullptr;
         }
     }
 
     /**
      * Get wrapped FILE* with transfer of ownership.
      * @note This will invalidate the CAutoFile object, and makes it the
      * responsibility of the caller of this function to clean up the returned
      * FILE*.
      */
     FILE *release() {
         FILE *ret = file;
         file = nullptr;
         return ret;
     }
 
     /**
      * Get wrapped FILE* without transfer of ownership.
      * @note Ownership of the FILE* will remain with this class. Use this only
      * if the scope of the CAutoFile outlives use of the passed pointer.
      */
     FILE *Get() const { return file; }
 
     /** Return true if the wrapped FILE* is nullptr, false otherwise. */
     bool IsNull() const { return (file == nullptr); }
 
     //
     // Stream subset
     //
     int GetType() const { return nType; }
     int GetVersion() const { return nVersion; }
 
     void read(char *pch, size_t nSize) {
         if (!file) {
             throw std::ios_base::failure(
                 "CAutoFile::read: file handle is nullptr");
         }
         if (fread(pch, 1, nSize, file) != nSize) {
             throw std::ios_base::failure(feof(file)
                                              ? "CAutoFile::read: end of file"
                                              : "CAutoFile::read: fread failed");
         }
     }
 
     void ignore(size_t nSize) {
         if (!file) {
             throw std::ios_base::failure(
                 "CAutoFile::ignore: file handle is nullptr");
         }
         uint8_t data[4096];
         while (nSize > 0) {
             size_t nNow = std::min<size_t>(nSize, sizeof(data));
             if (fread(data, 1, nNow, file) != nNow) {
                 throw std::ios_base::failure(
                     feof(file) ? "CAutoFile::ignore: end of file"
                                : "CAutoFile::read: fread failed");
             }
             nSize -= nNow;
         }
     }
 
     void write(const char *pch, size_t nSize) {
         if (!file) {
             throw std::ios_base::failure(
                 "CAutoFile::write: file handle is nullptr");
         }
         if (fwrite(pch, 1, nSize, file) != nSize) {
             throw std::ios_base::failure("CAutoFile::write: write failed");
         }
     }
 
     template <typename T> CAutoFile &operator<<(const T &obj) {
         // Serialize to this stream
         if (!file) {
             throw std::ios_base::failure(
                 "CAutoFile::operator<<: file handle is nullptr");
         }
         ::Serialize(*this, obj);
         return (*this);
     }
 
     template <typename T> CAutoFile &operator>>(T &&obj) {
         // Unserialize from this stream
         if (!file) {
             throw std::ios_base::failure(
                 "CAutoFile::operator>>: file handle is nullptr");
         }
         ::Unserialize(*this, obj);
         return (*this);
     }
 };
 
 /**
  * Non-refcounted RAII wrapper around a FILE* that implements a ring buffer to
  * deserialize from. It guarantees the ability to rewind a given number of
  * bytes.
  *
  * Will automatically close the file when it goes out of scope if not null. If
  * you need to close the file early, use file.fclose() instead of fclose(file).
  */
 class CBufferedFile {
 private:
     const int nType;
     const int nVersion;
 
     //! source file
     FILE *src;
     //! how many bytes have been read from source
     uint64_t nSrcPos;
     //! how many bytes have been read from this
     uint64_t nReadPos;
     //! up to which position we're allowed to read
     uint64_t nReadLimit;
     //! how many bytes we guarantee to rewind
     uint64_t nRewind;
     //! the buffer
     std::vector<char> vchBuf;
 
 protected:
     //! read data from the source to fill the buffer
     bool Fill() {
         unsigned int pos = nSrcPos % vchBuf.size();
         unsigned int readNow = vchBuf.size() - pos;
         unsigned int nAvail = vchBuf.size() - (nSrcPos - nReadPos) - nRewind;
         if (nAvail < readNow) {
             readNow = nAvail;
         }
         if (readNow == 0) {
             return false;
         }
         size_t nBytes = fread((void *)&vchBuf[pos], 1, readNow, src);
         if (nBytes == 0) {
             throw std::ios_base::failure(
                 feof(src) ? "CBufferedFile::Fill: end of file"
                           : "CBufferedFile::Fill: fread failed");
-        } else {
-            nSrcPos += nBytes;
-            return true;
         }
+        nSrcPos += nBytes;
+        return true;
     }
 
 public:
     CBufferedFile(FILE *fileIn, uint64_t nBufSize, uint64_t nRewindIn,
                   int nTypeIn, int nVersionIn)
         : nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0),
           nReadLimit(std::numeric_limits<uint64_t>::max()), nRewind(nRewindIn),
           vchBuf(nBufSize, 0) {
+        if (nRewindIn >= nBufSize) {
+            throw std::ios_base::failure(
+                "Rewind limit must be less than buffer size");
+        }
         src = fileIn;
     }
 
     ~CBufferedFile() { fclose(); }
 
     // Disallow copies
     CBufferedFile(const CBufferedFile &) = delete;
     CBufferedFile &operator=(const CBufferedFile &) = delete;
 
     int GetVersion() const { return nVersion; }
     int GetType() const { return nType; }
 
     void fclose() {
         if (src) {
             ::fclose(src);
             src = nullptr;
         }
     }
 
     //! check whether we're at the end of the source file
     bool eof() const { return nReadPos == nSrcPos && feof(src); }
 
     //! read a number of bytes
     void read(char *pch, size_t nSize) {
         if (nSize + nReadPos > nReadLimit) {
             throw std::ios_base::failure("Read attempted past buffer limit");
         }
-        if (nSize + nRewind > vchBuf.size()) {
-            throw std::ios_base::failure("Read larger than buffer size");
-        }
         while (nSize > 0) {
             if (nReadPos == nSrcPos) {
                 Fill();
             }
             unsigned int pos = nReadPos % vchBuf.size();
             size_t nNow = nSize;
             if (nNow + pos > vchBuf.size()) {
                 nNow = vchBuf.size() - pos;
             }
             if (nNow + nReadPos > nSrcPos) {
                 nNow = nSrcPos - nReadPos;
             }
             memcpy(pch, &vchBuf[pos], nNow);
             nReadPos += nNow;
             pch += nNow;
             nSize -= nNow;
         }
     }
 
     //! return the current reading position
     uint64_t GetPos() const { return nReadPos; }
 
     //! rewind to a given reading position
     bool SetPos(uint64_t nPos) {
-        nReadPos = nPos;
-        if (nReadPos + nRewind < nSrcPos) {
-            nReadPos = nSrcPos - nRewind;
+        size_t bufsize = vchBuf.size();
+        if (nPos + bufsize < nSrcPos) {
+            // rewinding too far, rewind as far as possible
+            nReadPos = nSrcPos - bufsize;
             return false;
-        } else if (nReadPos > nSrcPos) {
+        }
+        if (nPos > nSrcPos) {
+            // can't go this far forward, go as far as possible
             nReadPos = nSrcPos;
             return false;
-        } else {
-            return true;
         }
+        nReadPos = nPos;
+        return true;
     }
 
     bool Seek(uint64_t nPos) {
         long nLongPos = nPos;
         if (nPos != (uint64_t)nLongPos) {
             return false;
         }
         if (fseek(src, nLongPos, SEEK_SET)) {
             return false;
         }
         nLongPos = ftell(src);
         nSrcPos = nLongPos;
         nReadPos = nLongPos;
         return true;
     }
 
     //! Prevent reading beyond a certain position. No argument removes the
     //! limit.
     bool SetLimit(uint64_t nPos = std::numeric_limits<uint64_t>::max()) {
         if (nPos < nReadPos) {
             return false;
         }
         nReadLimit = nPos;
         return true;
     }
 
     template <typename T> CBufferedFile &operator>>(T &&obj) {
         // Unserialize from this stream
         ::Unserialize(*this, obj);
         return (*this);
     }
 
     //! search for a given byte in the stream, and remain positioned on it
     void FindByte(char ch) {
         while (true) {
             if (nReadPos == nSrcPos) {
                 Fill();
             }
             if (vchBuf[nReadPos % vchBuf.size()] == ch) {
                 break;
             }
             nReadPos++;
         }
     }
 };
 
 #endif // BITCOIN_STREAMS_H
diff --git a/src/test/streams_tests.cpp b/src/test/streams_tests.cpp
index cb612ea85..89bc6ca49 100644
--- a/src/test/streams_tests.cpp
+++ b/src/test/streams_tests.cpp
@@ -1,221 +1,470 @@
 // Copyright (c) 2012-2019 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 <random.h>
 #include <streams.h>
 
 #include <test/util/setup_common.h>
 
 #include <boost/test/unit_test.hpp>
 
 BOOST_FIXTURE_TEST_SUITE(streams_tests, BasicTestingSetup)
 
 BOOST_AUTO_TEST_CASE(streams_vector_writer) {
     uint8_t a(1);
     uint8_t b(2);
     uint8_t bytes[] = {3, 4, 5, 6};
     std::vector<uint8_t> vch;
 
     // Each test runs twice. Serializing a second time at the same starting
     // point should yield the same results, even if the first test grew the
     // vector.
 
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{1, 2}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{1, 2}}));
     vch.clear();
 
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 1, 2}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 1, 2}}));
     vch.clear();
 
     vch.resize(5, 0);
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 1, 2, 0}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 1, 2, 0}}));
     vch.clear();
 
     vch.resize(4, 0);
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 3, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 0, 1, 2}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 3, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 0, 1, 2}}));
     vch.clear();
 
     vch.resize(4, 0);
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 4, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 0, 0, 1, 2}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 4, a, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{0, 0, 0, 0, 1, 2}}));
     vch.clear();
 
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, bytes);
     BOOST_CHECK((vch == std::vector<uint8_t>{{3, 4, 5, 6}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 0, bytes);
     BOOST_CHECK((vch == std::vector<uint8_t>{{3, 4, 5, 6}}));
     vch.clear();
 
     vch.resize(4, 8);
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, bytes, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{8, 8, 1, 3, 4, 5, 6, 2}}));
     CVectorWriter(SER_NETWORK, INIT_PROTO_VERSION, vch, 2, a, bytes, b);
     BOOST_CHECK((vch == std::vector<uint8_t>{{8, 8, 1, 3, 4, 5, 6, 2}}));
     vch.clear();
 }
 
 BOOST_AUTO_TEST_CASE(streams_vector_reader) {
     std::vector<uint8_t> vch = {1, 255, 3, 4, 5, 6};
 
     VectorReader reader(SER_NETWORK, INIT_PROTO_VERSION, vch, 0);
     BOOST_CHECK_EQUAL(reader.size(), 6);
     BOOST_CHECK(!reader.empty());
 
     // Read a single byte as an uint8_t.
     uint8_t a;
     reader >> a;
     BOOST_CHECK_EQUAL(a, 1);
     BOOST_CHECK_EQUAL(reader.size(), 5);
     BOOST_CHECK(!reader.empty());
 
     // Read a single byte as a (signed) int8_t.
     int8_t b;
     reader >> b;
     BOOST_CHECK_EQUAL(b, -1);
     BOOST_CHECK_EQUAL(reader.size(), 4);
     BOOST_CHECK(!reader.empty());
 
     // Read a 4 bytes as an unsigned uint32_t.
     uint32_t c;
     reader >> c;
     // 100992003 = 3,4,5,6 in little-endian base-256
     BOOST_CHECK_EQUAL(c, 100992003);
     BOOST_CHECK_EQUAL(reader.size(), 0);
     BOOST_CHECK(reader.empty());
 
     // Reading after end of byte vector throws an error.
     int32_t d;
     BOOST_CHECK_THROW(reader >> d, std::ios_base::failure);
 
     // Read a 4 bytes as a (signed) int32_t from the beginning of the buffer.
     VectorReader new_reader(SER_NETWORK, INIT_PROTO_VERSION, vch, 0);
     new_reader >> d;
     // 67370753 = 1,255,3,4 in little-endian base-256
     BOOST_CHECK_EQUAL(d, 67370753);
     BOOST_CHECK_EQUAL(new_reader.size(), 2);
     BOOST_CHECK(!new_reader.empty());
 
     // Reading after end of byte vector throws an error even if the reader is
     // not totally empty.
     BOOST_CHECK_THROW(new_reader >> d, std::ios_base::failure);
 }
 
 BOOST_AUTO_TEST_CASE(bitstream_reader_writer) {
     CDataStream data(SER_NETWORK, INIT_PROTO_VERSION);
 
     BitStreamWriter<CDataStream> bit_writer(data);
     bit_writer.Write(0, 1);
     bit_writer.Write(2, 2);
     bit_writer.Write(6, 3);
     bit_writer.Write(11, 4);
     bit_writer.Write(1, 5);
     bit_writer.Write(32, 6);
     bit_writer.Write(7, 7);
     bit_writer.Write(30497, 16);
     bit_writer.Flush();
 
     CDataStream data_copy(data);
     uint32_t serialized_int1;
     data >> serialized_int1;
     // NOTE: Serialized as LE
     BOOST_CHECK_EQUAL(serialized_int1, (uint32_t)0x7700C35A);
     uint16_t serialized_int2;
     data >> serialized_int2;
     // NOTE: Serialized as LE
     BOOST_CHECK_EQUAL(serialized_int2, (uint16_t)0x1072);
 
     BitStreamReader<CDataStream> bit_reader(data_copy);
     BOOST_CHECK_EQUAL(bit_reader.Read(1), 0);
     BOOST_CHECK_EQUAL(bit_reader.Read(2), 2);
     BOOST_CHECK_EQUAL(bit_reader.Read(3), 6);
     BOOST_CHECK_EQUAL(bit_reader.Read(4), 11);
     BOOST_CHECK_EQUAL(bit_reader.Read(5), 1);
     BOOST_CHECK_EQUAL(bit_reader.Read(6), 32);
     BOOST_CHECK_EQUAL(bit_reader.Read(7), 7);
     BOOST_CHECK_EQUAL(bit_reader.Read(16), 30497);
     BOOST_CHECK_THROW(bit_reader.Read(8), std::ios_base::failure);
 }
 
 BOOST_AUTO_TEST_CASE(streams_serializedata_xor) {
     std::vector<char> in;
     std::vector<char> expected_xor;
     std::vector<uint8_t> key;
     CDataStream ds(in, 0, 0);
 
     // Degenerate case
 
     key.push_back('\x00');
     key.push_back('\x00');
     ds.Xor(key);
     BOOST_CHECK_EQUAL(std::string(expected_xor.begin(), expected_xor.end()),
                       std::string(ds.begin(), ds.end()));
 
     in.push_back('\x0f');
     in.push_back('\xf0');
     expected_xor.push_back('\xf0');
     expected_xor.push_back('\x0f');
 
     // Single character key
 
     ds.clear();
     ds.insert(ds.begin(), in.begin(), in.end());
     key.clear();
 
     key.push_back('\xff');
     ds.Xor(key);
     BOOST_CHECK_EQUAL(std::string(expected_xor.begin(), expected_xor.end()),
                       std::string(ds.begin(), ds.end()));
 
     // Multi character key
 
     in.clear();
     expected_xor.clear();
     in.push_back('\xf0');
     in.push_back('\x0f');
     expected_xor.push_back('\x0f');
     expected_xor.push_back('\x00');
 
     ds.clear();
     ds.insert(ds.begin(), in.begin(), in.end());
 
     key.clear();
     key.push_back('\xff');
     key.push_back('\x0f');
 
     ds.Xor(key);
     BOOST_CHECK_EQUAL(std::string(expected_xor.begin(), expected_xor.end()),
                       std::string(ds.begin(), ds.end()));
 }
 
 BOOST_AUTO_TEST_CASE(streams_empty_vector) {
     std::vector<char> in;
     CDataStream ds(in, 0, 0);
 
     // read 0 bytes used to cause a segfault on some older systems.
     BOOST_CHECK_NO_THROW(ds.read(nullptr, 0));
 
     // Same goes for writing 0 bytes from a vector ...
     const std::vector<char> vdata{'f', 'o', 'o', 'b', 'a', 'r'};
     BOOST_CHECK_NO_THROW(ds.insert(ds.begin(), vdata.begin(), vdata.begin()));
     BOOST_CHECK_NO_THROW(ds.insert(ds.begin(), vdata.begin(), vdata.end()));
 
     // ... or an array.
     const char adata[6] = {'f', 'o', 'o', 'b', 'a', 'r'};
     BOOST_CHECK_NO_THROW(ds.insert(ds.begin(), &adata[0], &adata[0]));
     BOOST_CHECK_NO_THROW(ds.insert(ds.begin(), &adata[0], &adata[6]));
 }
 
+BOOST_AUTO_TEST_CASE(streams_buffered_file) {
+    FILE *file = fsbridge::fopen("streams_test_tmp", "w+b");
+    // The value at each offset is the offset.
+    for (uint8_t j = 0; j < 40; ++j) {
+        fwrite(&j, 1, 1, file);
+    }
+    rewind(file);
+
+    // The buffer size (second arg) must be greater than the rewind
+    // amount (third arg).
+    try {
+        CBufferedFile bfbad(file, 25, 25, 222, 333);
+        BOOST_CHECK(false);
+    } catch (const std::exception &e) {
+        BOOST_CHECK(
+            strstr(e.what(), "Rewind limit must be less than buffer size") !=
+            nullptr);
+    }
+
+    // The buffer is 25 bytes, allow rewinding 10 bytes.
+    CBufferedFile bf(file, 25, 10, 222, 333);
+    BOOST_CHECK(!bf.eof());
+
+    // These two members have no functional effect.
+    BOOST_CHECK_EQUAL(bf.GetType(), 222);
+    BOOST_CHECK_EQUAL(bf.GetVersion(), 333);
+
+    uint8_t i;
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 0);
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 1);
+
+    // After reading bytes 0 and 1, we're positioned at 2.
+    BOOST_CHECK_EQUAL(bf.GetPos(), 2);
+
+    // Rewind to offset 0, ok (within the 10 byte window).
+    BOOST_CHECK(bf.SetPos(0));
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 0);
+
+    // We can go forward to where we've been, but beyond may fail.
+    BOOST_CHECK(bf.SetPos(2));
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 2);
+
+    // If you know the maximum number of bytes that should be
+    // read to deserialize the variable, you can limit the read
+    // extent. The current file offset is 3, so the following
+    // SetLimit() allows zero bytes to be read.
+    BOOST_CHECK(bf.SetLimit(3));
+    try {
+        bf >> i;
+        BOOST_CHECK(false);
+    } catch (const std::exception &e) {
+        BOOST_CHECK(strstr(e.what(), "Read attempted past buffer limit") !=
+                    nullptr);
+    }
+    // The default argument removes the limit completely.
+    BOOST_CHECK(bf.SetLimit());
+    // The read position should still be at 3 (no change).
+    BOOST_CHECK_EQUAL(bf.GetPos(), 3);
+
+    // Read from current offset, 3, forward until position 10.
+    for (uint8_t j = 3; j < 10; ++j) {
+        bf >> i;
+        BOOST_CHECK_EQUAL(i, j);
+    }
+    BOOST_CHECK_EQUAL(bf.GetPos(), 10);
+
+    // We're guaranteed (just barely) to be able to rewind to zero.
+    BOOST_CHECK(bf.SetPos(0));
+    BOOST_CHECK_EQUAL(bf.GetPos(), 0);
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 0);
+
+    // We can set the position forward again up to the farthest
+    // into the stream we've been, but no farther. (Attempting
+    // to go farther may succeed, but it's not guaranteed.)
+    BOOST_CHECK(bf.SetPos(10));
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 10);
+    BOOST_CHECK_EQUAL(bf.GetPos(), 11);
+
+    // Now it's only guaranteed that we can rewind to offset 1
+    // (current read position, 11, minus rewind amount, 10).
+    BOOST_CHECK(bf.SetPos(1));
+    BOOST_CHECK_EQUAL(bf.GetPos(), 1);
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 1);
+
+    // We can stream into large variables, even larger than
+    // the buffer size.
+    BOOST_CHECK(bf.SetPos(11));
+    {
+        uint8_t a[40 - 11];
+        bf >> a;
+        for (uint8_t j = 0; j < sizeof(a); ++j) {
+            BOOST_CHECK_EQUAL(a[j], 11 + j);
+        }
+    }
+    BOOST_CHECK_EQUAL(bf.GetPos(), 40);
+
+    // We've read the entire file, the next read should throw.
+    try {
+        bf >> i;
+        BOOST_CHECK(false);
+    } catch (const std::exception &e) {
+        BOOST_CHECK(strstr(e.what(), "CBufferedFile::Fill: end of file") !=
+                    nullptr);
+    }
+    // Attempting to read beyond the end sets the EOF indicator.
+    BOOST_CHECK(bf.eof());
+
+    // Still at offset 40, we can go back 10, to 30.
+    BOOST_CHECK_EQUAL(bf.GetPos(), 40);
+    BOOST_CHECK(bf.SetPos(30));
+    bf >> i;
+    BOOST_CHECK_EQUAL(i, 30);
+    BOOST_CHECK_EQUAL(bf.GetPos(), 31);
+
+    // We're too far to rewind to position zero.
+    BOOST_CHECK(!bf.SetPos(0));
+    // But we should now be positioned at least as far back as allowed
+    // by the rewind window (relative to our farthest read position, 40).
+    BOOST_CHECK(bf.GetPos() <= 30);
+
+    // We can explicitly close the file, or the destructor will do it.
+    bf.fclose();
+
+    fs::remove("streams_test_tmp");
+}
+
+BOOST_AUTO_TEST_CASE(streams_buffered_file_rand) {
+    // Make this test deterministic.
+    SeedInsecureRand(SeedRand::ZEROS);
+
+    for (int rep = 0; rep < 50; ++rep) {
+        FILE *file = fsbridge::fopen("streams_test_tmp", "w+b");
+        size_t fileSize = InsecureRandRange(256);
+        for (uint8_t i = 0; i < fileSize; ++i) {
+            fwrite(&i, 1, 1, file);
+        }
+        rewind(file);
+
+        size_t bufSize = InsecureRandRange(300) + 1;
+        size_t rewindSize = InsecureRandRange(bufSize);
+        CBufferedFile bf(file, bufSize, rewindSize, 222, 333);
+        size_t currentPos = 0;
+        size_t maxPos = 0;
+        for (int step = 0; step < 100; ++step) {
+            if (currentPos >= fileSize) {
+                break;
+            }
+
+            // We haven't read to the end of the file yet.
+            BOOST_CHECK(!bf.eof());
+            BOOST_CHECK_EQUAL(bf.GetPos(), currentPos);
+
+            // Pretend the file consists of a series of objects of varying
+            // sizes; the boundaries of the objects can interact arbitrarily
+            // with the CBufferFile's internal buffer. These first three
+            // cases simulate objects of various sizes (1, 2, 5 bytes).
+            switch (InsecureRandRange(5)) {
+                case 0: {
+                    uint8_t a[1];
+                    if (currentPos + 1 > fileSize) {
+                        continue;
+                    }
+                    bf.SetLimit(currentPos + 1);
+                    bf >> a;
+                    for (uint8_t i = 0; i < 1; ++i) {
+                        BOOST_CHECK_EQUAL(a[i], currentPos);
+                        currentPos++;
+                    }
+                    break;
+                }
+                case 1: {
+                    uint8_t a[2];
+                    if (currentPos + 2 > fileSize) {
+                        continue;
+                    }
+                    bf.SetLimit(currentPos + 2);
+                    bf >> a;
+                    for (uint8_t i = 0; i < 2; ++i) {
+                        BOOST_CHECK_EQUAL(a[i], currentPos);
+                        currentPos++;
+                    }
+                    break;
+                }
+                case 2: {
+                    uint8_t a[5];
+                    if (currentPos + 5 > fileSize) {
+                        continue;
+                    }
+                    bf.SetLimit(currentPos + 5);
+                    bf >> a;
+                    for (uint8_t i = 0; i < 5; ++i) {
+                        BOOST_CHECK_EQUAL(a[i], currentPos);
+                        currentPos++;
+                    }
+                    break;
+                }
+                case 3: {
+                    // Find a byte value (that is at or ahead of the current
+                    // position).
+                    size_t find = currentPos + InsecureRandRange(8);
+                    if (find >= fileSize) {
+                        find = fileSize - 1;
+                    }
+                    bf.FindByte(static_cast<char>(find));
+                    // The value at each offset is the offset.
+                    BOOST_CHECK_EQUAL(bf.GetPos(), find);
+                    currentPos = find;
+
+                    bf.SetLimit(currentPos + 1);
+                    uint8_t i;
+                    bf >> i;
+                    BOOST_CHECK_EQUAL(i, currentPos);
+                    currentPos++;
+                    break;
+                }
+                case 4: {
+                    size_t requestPos = InsecureRandRange(maxPos + 4);
+                    bool okay = bf.SetPos(requestPos);
+                    // The new position may differ from the requested position
+                    // because we may not be able to rewind beyond the rewind
+                    // window, and we may not be able to move forward beyond the
+                    // farthest position we've reached so far.
+                    currentPos = bf.GetPos();
+                    BOOST_CHECK_EQUAL(okay, currentPos == requestPos);
+                    // Check that we can position within the rewind window.
+                    if (requestPos <= maxPos && maxPos > rewindSize &&
+                        requestPos >= maxPos - rewindSize) {
+                        // We requested a position within the rewind window.
+                        BOOST_CHECK(okay);
+                    }
+                    break;
+                }
+            }
+            if (maxPos < currentPos) {
+                maxPos = currentPos;
+            }
+        }
+    }
+    fs::remove("streams_test_tmp");
+}
+
 BOOST_AUTO_TEST_SUITE_END()