Add CBufferedFile
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144
src/serialize.h
144
src/serialize.h
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@ -1225,4 +1225,148 @@ public:
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}
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};
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/** Wrapper around a FILE* that implements a ring buffer to
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* deserialize from. It guarantees the ability to rewind
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* a given number of bytes. */
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class CBufferedFile
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{
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private:
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FILE *src; // source file
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uint64 nSrcPos; // how many bytes have been read from source
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uint64 nReadPos; // how many bytes have been read from this
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uint64 nReadLimit; // up to which position we're allowed to read
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uint64 nRewind; // how many bytes we guarantee to rewind
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std::vector<char> vchBuf; // the buffer
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short state;
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short exceptmask;
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protected:
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void setstate(short bits, const char *psz) {
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state |= bits;
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if (state & exceptmask)
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throw std::ios_base::failure(psz);
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}
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// read data from the source to fill the buffer
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bool Fill() {
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unsigned int pos = nSrcPos % vchBuf.size();
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unsigned int readNow = vchBuf.size() - pos;
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unsigned int nAvail = vchBuf.size() - (nSrcPos - nReadPos) - nRewind;
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if (nAvail < readNow)
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readNow = nAvail;
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if (readNow == 0)
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return false;
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size_t read = fread((void*)&vchBuf[pos], 1, readNow, src);
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if (read == 0) {
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setstate(std::ios_base::failbit, feof(src) ? "CBufferedFile::Fill : end of file" : "CBufferedFile::Fill : fread failed");
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return false;
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} else {
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nSrcPos += read;
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return true;
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}
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}
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public:
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int nType;
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int nVersion;
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CBufferedFile(FILE *fileIn, uint64 nBufSize, uint64 nRewindIn, int nTypeIn, int nVersionIn) :
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src(fileIn), nSrcPos(0), nReadPos(0), nReadLimit((uint64)(-1)), nRewind(nRewindIn), vchBuf(nBufSize, 0),
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state(0), exceptmask(std::ios_base::badbit | std::ios_base::failbit), nType(nTypeIn), nVersion(nVersionIn) {
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}
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// check whether no error occurred
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bool good() const {
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return state == 0;
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}
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// check whether we're at the end of the source file
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bool eof() const {
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return nReadPos == nSrcPos && feof(src);
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}
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// read a number of bytes
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CBufferedFile& read(char *pch, size_t nSize) {
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if (nSize + nReadPos > nReadLimit)
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throw std::ios_base::failure("Read attempted past buffer limit");
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if (nSize + nRewind > vchBuf.size())
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throw std::ios_base::failure("Read larger than buffer size");
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while (nSize > 0) {
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if (nReadPos == nSrcPos)
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Fill();
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unsigned int pos = nReadPos % vchBuf.size();
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size_t nNow = nSize;
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if (nNow + pos > vchBuf.size())
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nNow = vchBuf.size() - pos;
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if (nNow + nReadPos > nSrcPos)
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nNow = nSrcPos - nReadPos;
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memcpy(pch, &vchBuf[pos], nNow);
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nReadPos += nNow;
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pch += nNow;
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nSize -= nNow;
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}
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return (*this);
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}
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// return the current reading position
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uint64 GetPos() {
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return nReadPos;
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}
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// rewind to a given reading position
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bool SetPos(uint64 nPos) {
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nReadPos = nPos;
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if (nReadPos + nRewind < nSrcPos) {
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nReadPos = nSrcPos - nRewind;
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return false;
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} else if (nReadPos > nSrcPos) {
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nReadPos = nSrcPos;
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return false;
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} else {
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return true;
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}
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}
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bool Seek(uint64 nPos) {
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long nLongPos = nPos;
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if (nPos != (uint64)nLongPos)
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return false;
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if (fseek(src, nLongPos, SEEK_SET))
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return false;
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nLongPos = ftell(src);
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nSrcPos = nLongPos;
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nReadPos = nLongPos;
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state = 0;
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return true;
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}
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// prevent reading beyond a certain position
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// no argument removes the limit
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bool SetLimit(uint64 nPos = (uint64)(-1)) {
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if (nPos < nReadPos)
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return false;
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nReadLimit = nPos;
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return true;
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}
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template<typename T>
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CBufferedFile& operator>>(T& obj) {
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// Unserialize from this stream
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::Unserialize(*this, obj, nType, nVersion);
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return (*this);
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}
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// search for a given byte in the stream, and remain positioned on it
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void FindByte(char ch) {
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while (true) {
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if (nReadPos == nSrcPos)
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Fill();
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if (vchBuf[nReadPos % vchBuf.size()] == ch)
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break;
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nReadPos++;
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}
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}
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};
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#endif
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