Add Coprocess class

It provides a convenient way to spawn a process and read from/write to
its stdin/stdout.

fhstream.hpp

@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2012, 2015 Andrew Ayer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name(s) of the above copyright
+ * holders shall not be used in advertising or otherwise to promote the
+ * sale, use or other dealings in this Software without prior written
+ * authorization.
+ */
+
+#ifndef GIT_CRYPT_FHSTREAM_HPP
+#define GIT_CRYPT_FHSTREAM_HPP
+
+#include <ostream>
+#include <istream>
+#include <streambuf>
+
+/*
+ * ofhstream
+ */
+class ofhbuf : public std::streambuf {
+	enum { default_buffer_size = 8192 };
+
+	void*			handle;
+	size_t			(*write_fun)(void*, const void*, size_t);
+	char*			buffer;
+	size_t			buffer_size;
+
+	inline void reset_buffer ()
+	{
+		std::streambuf::setp(buffer, buffer + buffer_size - 1);
+	}
+	static inline bool is_eof (int_type ch) { return traits_type::eq_int_type(ch, traits_type::eof()); }
+
+	// Disallow copy
+#if __cplusplus >= 201103L /* C++11 */
+	ofhbuf (const ofhbuf&) = delete;
+	ofhbuf& operator= (const ofhbuf&) = delete;
+#else
+	ofhbuf (const ofhbuf&);
+	ofhbuf& operator= (const ofhbuf&);
+#endif
+
+protected:
+	virtual int_type	overflow (int_type ch =traits_type::eof());
+	virtual int		sync ();
+	virtual std::streamsize	xsputn (const char*, std::streamsize);
+	virtual	std::streambuf*	setbuf (char*, std::streamsize);
+
+public:
+	ofhbuf (void*, size_t (*)(void*, const void*, size_t));
+	~ofhbuf (); // WARNING: calls sync() and ignores exceptions
+};
+
+class ofhstream : public std::ostream {
+	mutable ofhbuf	buf;
+public:
+	ofhstream (void* handle, size_t (*write_fun)(void*, const void*, size_t))
+	: std::ostream(0), buf(handle, write_fun)
+	{
+		std::ostream::rdbuf(&buf);
+	}
+
+	ofhbuf*	rdbuf () const { return &buf; }
+};
+
+
+/*
+ * ifhstream
+ */
+class ifhbuf : public std::streambuf {
+	enum {
+		default_buffer_size = 8192,
+		putback_size = 4
+	};
+
+	void*			handle;
+	size_t			(*read_fun)(void*, void*, size_t);
+	char*			buffer;
+	size_t			buffer_size;
+
+	inline void reset_buffer (size_t nputback, size_t nread)
+	{
+		std::streambuf::setg(buffer + (putback_size - nputback), buffer + putback_size, buffer + putback_size + nread);
+	}
+	// Disallow copy
+#if __cplusplus >= 201103L /* C++11 */
+	ifhbuf (const ifhbuf&) = delete;
+	ifhbuf& operator= (const ifhbuf&) = delete;
+#else
+	ifhbuf (const ifhbuf&);
+	ifhbuf& operator= (const ifhbuf&);
+#endif
+
+protected:
+	virtual int_type	underflow ();
+	virtual std::streamsize	xsgetn (char*, std::streamsize);
+	virtual	std::streambuf*	setbuf (char*, std::streamsize);
+
+public:
+	ifhbuf (void*, size_t (*)(void*, void*, size_t));
+	~ifhbuf (); // Can't fail
+};
+
+class ifhstream : public std::istream {
+	mutable ifhbuf	buf;
+public:
+	explicit ifhstream (void* handle, size_t (*read_fun)(void*, void*, size_t))
+	: std::istream(0), buf(handle, read_fun)
+	{
+		std::istream::rdbuf(&buf);
+	}
+
+	ifhbuf*	rdbuf () const { return &buf; }
+};
+
+#endif