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#ifndef _GZFILEBUF_H_
#define _GZFILEBUF_H_
#include <streambuf>
#include <zlib.h>
class gzfilebuf : public std::streambuf {
public:
gzfilebuf(const char *filename)
{ _gzf = gzopen(filename, "rb");
setg (_buff+sizeof(int), // beginning of putback area
_buff+sizeof(int), // read position
_buff+sizeof(int)); // end position
}
~gzfilebuf() { gzclose(_gzf); }
protected:
virtual int_type overflow (int_type c) {
throw;
}
// write multiple characters
virtual
std::streamsize xsputn (const char* s,
std::streamsize num) {
throw;
}
virtual std::streampos seekpos ( std::streampos sp, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out ){ throw;
}
//read one character
virtual int_type underflow () {
// is read position before end of _buff?
if (gptr() < egptr()) {
return traits_type::to_int_type(*gptr());
}
/* process size of putback area
* - use number of characters read
* - but at most four
*/
unsigned int numPutback = gptr() - eback();
if (numPutback > sizeof(int)) {
numPutback = sizeof(int);
}
/* copy up to four characters previously read into
* the putback _buff (area of first four characters)
*/
std::memmove (_buff+(sizeof(int)-numPutback), gptr()-numPutback,
numPutback);
// read new characters
int num = gzread(_gzf, _buff+sizeof(int), _buffsize-sizeof(int));
if (num <= 0) {
// ERROR or EOF
return EOF;
}
// reset _buff pointers
setg (_buff+(sizeof(int)-numPutback), // beginning of putback area
_buff+sizeof(int), // read position
_buff+sizeof(int)+num); // end of buffer
// return next character
return traits_type::to_int_type(*gptr());
}
std::streamsize xsgetn (char* s,
std::streamsize num) {
return gzread(_gzf,s,num);
}
private:
gzFile _gzf;
static const unsigned int _buffsize = 1024;
char _buff[_buffsize];
};
#endif
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