From de371a94a561b251821c110c69ed87e0a8fe39da Mon Sep 17 00:00:00 2001
From: Bob Polis <rpb.polis@avans.nl>
Date: Sat, 25 Apr 2020 16:40:42 +0200
Subject: [PATCH] fixed and improved single buffer version, added seeking as
 well

---
 fdiobuf.cpp | 59 ++++++++++++++++++++++++++++++++++++++---------------
 libscio.hpp |  9 ++++++++
 2 files changed, 52 insertions(+), 16 deletions(-)

diff --git a/fdiobuf.cpp b/fdiobuf.cpp
index 7780d90..1529b99 100644
--- a/fdiobuf.cpp
+++ b/fdiobuf.cpp
@@ -28,23 +28,50 @@ std::streamsize sc::io::fdiobuf::xsgetn(char* s, std::streamsize n) {
 }
 
 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';
-        }
-    }
-    return 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;
+	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;
 }
diff --git a/libscio.hpp b/libscio.hpp
index 70480ad..e5ce3a1 100644
--- a/libscio.hpp
+++ b/libscio.hpp
@@ -40,6 +40,15 @@ namespace sc {
 				// output
 				int_type overflow(int_type c) override;
 				std::streamsize xsputn(const char* s, std::streamsize num) override;
+
+				// stream offset positioning
+				pos_type seekoff(off_type off,
+								 std::ios_base::seekdir dir,
+								 std::ios_base::openmode which
+								 = std::ios_base::in | std::ios_base::out) override;
+				pos_type seekpos(pos_type pos, std::ios_base::openmode which
+								 = std::ios_base::in | std::ios_base::out) override;
+				int_type pbackfail(int_type c = EOF) override;
 		};
 
 		class fdostream : public std::ostream {