libscio/fdiobuf.cpp

//
// fdiobuf.cpp
// libscio
//
// Created by Bob Polis at 2020-02-14
// Copyright (c) 2020 SwiftCoder. All rights reserved.
//

#include "libscio.hpp"

#ifdef _MSC_VER
#include <io.h>
#else
#include <unistd.h>
#endif

std::streambuf::int_type sc::io::fdiobuf::underflow() {
	int num = ::read(_fd, &_ch, 1);
	if (num <= 0) {
		return EOF;
	}
	setg(&_ch, &_ch, &_ch + 1);
	return _ch;
}

std::streamsize sc::io::fdiobuf::xsgetn(char* s, std::streamsize n) {
	std::streamsize tot_read = 0;
	std::streamsize next_amount = n;
	while (next_amount) {
		ssize_t num_read = ::read(_fd, s, next_amount);
		if (num_read == -1) {
			if (errno == EINTR) { // interrupted => restart
				continue;
			} else {
				return -1; // real error
			}
		} else if (num_read == 0) { // EOF
			break;
		} else {
			tot_read += num_read;
			next_amount -= num_read;
		}
	}
	return tot_read;
}

std::streambuf::int_type sc::io::fdiobuf::overflow(std::streambuf::int_type c) {
	if (c != EOF) {
		int res;
		if ((res = ::write(_fd, &c, 1)) != 1) {
			return EOF;
		}
		else {
			std::cerr << "write result = " << res << ", errno = " << errno << '\n';
		}
	}
	_ch = c;
	setp(&_ch, &_ch + 1);
	return c;
}

std::streamsize sc::io::fdiobuf::xsputn(const char* s, std::streamsize num) {
	int res = ::write(_fd, s, num);
	if (res != num) {
		std::cerr << "write result = " << res << ", errno = " << errno << '\n';
		return EOF;
	}
	return res;
}

std::streambuf::pos_type sc::io::fdiobuf::seekoff(std::streambuf::off_type off,
												  std::ios_base::seekdir dir,
												  std::ios_base::openmode /*which*/) {
	int whence;
	switch (dir) {
		case std::ios_base::beg: whence = SEEK_SET; break;
		case std::ios_base::end: whence = SEEK_END; break;
		case std::ios_base::cur: whence = SEEK_CUR; break;
		default: throw std::runtime_error("invalid seekdir");
	}
	return ::lseek(_fd, off, whence);
}

std::streambuf::pos_type sc::io::fdiobuf::seekpos(std::streambuf::pos_type pos,
												  std::ios_base::openmode /*which*/) {
	return ::lseek(_fd, pos, SEEK_SET);
}

std::streambuf::int_type sc::io::fdiobuf::pbackfail(std::streambuf::int_type /*c*/) {
	if (::lseek(_fd, -1, SEEK_CUR) == -1) {
		return EOF;
	}
	return 0;
}