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#include "GzFileBuf.h"
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <iostream>
GzFileBuf::GzFileBuf(const char* filename)
{
m_gz_file = gzopen(filename, "rb");
if (m_gz_file == NULL) {
std::cerr << "ERROR: Failed to open " << filename << std::endl;
std::exit(1);
}
setg(m_buf + sizeof(int), // beginning of putback area
m_buf + sizeof(int), // read position
m_buf + sizeof(int)); // end position
}
GzFileBuf::~GzFileBuf()
{
gzclose(m_gz_file);
}
int GzFileBuf::overflow(int_type c)
{
throw;
}
// read one character
int GzFileBuf::underflow()
{
// is read position before end of m_buf?
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 num_put_back = static_cast<unsigned int>(gptr() - eback());
if (num_put_back > sizeof(int)) {
num_put_back = sizeof(int);
}
/* copy up to four characters previously read into
* the putback m_buf (area of first four characters)
*/
std::memmove(m_buf + (sizeof(int) - num_put_back),
gptr() - num_put_back, num_put_back);
// read new characters
const int num = gzread(m_gz_file, m_buf + sizeof(int),
kBufSize - sizeof(int));
if (num <= 0) {
// ERROR or EOF
return EOF; // NOTE: the macro EOF defined in stdio.h
}
// reset m_buf pointers
setg(m_buf + (sizeof(int) - num_put_back), // beginning of putback area
m_buf + sizeof(int), // read position
m_buf + sizeof(int) + num); // end of buffer
// return next character
return traits_type::to_int_type(*gptr());
}
std::streampos GzFileBuf::seekpos(
std::streampos sp,
std::ios_base::openmode which)
{
throw;
}
std::streamsize GzFileBuf::xsgetn(char* s,
std::streamsize num)
{
return static_cast<std::streamsize>(gzread(m_gz_file,s,num));
}
std::streamsize GzFileBuf::xsputn(const char* s,
std::streamsize num)
{
throw;
}
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