streams.h

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2020 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 <span.h>
#include <support/allocators/zeroafterfree.h>

#include <algorithm>
#include <assert.h>
#include <ios>
#include <limits>
#include <optional>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#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; }
    size_t size() const { return stream->size(); }
    void ignore(size_t size) { return stream->ignore(size); }
};

/* 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<unsigned char>& 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<unsigned char>& 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 unsigned char*>(pch), nOverwrite);
        }
        if (nOverwrite < nSize) {
            vchData.insert(vchData.end(), reinterpret_cast<const unsigned char*>(pch) + nOverwrite, reinterpret_cast<const unsigned char*>(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;
    }
private:
    const int nType;
    const int nVersion;
    std::vector<unsigned char>& 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<unsigned char>& 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<unsigned char>& 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<unsigned char>& 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:
    using vector_type = SerializeData;
    vector_type vch;
    unsigned int nReadPos{0};

    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)
        : nType{nTypeIn},
          nVersion{nVersionIn} {}

    explicit CDataStream(Span<const uint8_t> sp, int nTypeIn, int nVersionIn)
        : vch(sp.data(), sp.data() + sp.size()),
          nType{nTypeIn},
          nVersion{nVersionIn} {}

    template <typename... Args>
    CDataStream(int nTypeIn, int nVersionIn, Args&&... args)
        : nType{nTypeIn},
          nVersion{nVersionIn}
    {
        ::SerializeMany(*this, std::forward<Args>(args)...);
    }

    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 uint8_t x) { return vch.insert(it, x); }
    void insert(iterator it, size_type n, const uint8_t 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<uint8_t>::const_iterator first, std::vector<uint8_t>::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(std::optional<size_type> n = std::nullopt)
    {
        // Total rewind if no size is passed
        if (!n) {
            nReadPos = 0;
            return true;
        }
        // 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);
    }

    /**
     * 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<unsigned char>& 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");
        unsigned char 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;

    FILE *src;            //!< source file
    uint64_t nSrcPos;     //!< how many bytes have been read from source
    uint64_t nReadPos;    //!< how many bytes have been read from this
    uint64_t nReadLimit;  //!< up to which position we're allowed to read
    uint64_t nRewind;     //!< how many bytes we guarantee to rewind
    std::vector<char> vchBuf; //!< the buffer

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");
        }
        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");
        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) {
        size_t bufsize = vchBuf.size();
        if (nPos + bufsize < nSrcPos) {
            // rewinding too far, rewind as far as possible
            nReadPos = nSrcPos - bufsize;
            return false;
        }
        if (nPos > nSrcPos) {
            // can't go this far forward, go as far as possible
            nReadPos = nSrcPos;
            return false;
        }
        nReadPos = nPos;
        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