Add Coprocess class

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

fhstream.cpp

@@ -0,0 +1,227 @@
+/*
+ * 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.
+ */
+
+#include <cstring>
+#include <algorithm> // for std::min
+
+#include "fhstream.hpp"
+
+/*
+ * ofhstream
+ */
+
+ofhbuf::ofhbuf (void* arg_handle, size_t (*arg_write_fun)(void*, const void*, size_t))
+: handle(arg_handle),
+  write_fun(arg_write_fun),
+  buffer(new char[default_buffer_size]),
+  buffer_size(default_buffer_size)
+{
+	reset_buffer();
+}
+
+ofhbuf::~ofhbuf ()
+{
+	if (handle) {
+		try {
+			sync();
+		} catch (...) {
+			// Ignore exception since we're in the destructor.
+			// To catch write errors, call sync() explicitly.
+		}
+	}
+	delete[] buffer;
+}
+
+ofhbuf::int_type	ofhbuf::overflow (ofhbuf::int_type c)
+{
+	const char*	p = pbase();
+	std::streamsize	bytes_to_write = pptr() - p;
+
+	if (!is_eof(c)) {
+	      *pptr() = c;
+	      ++bytes_to_write;
+	}
+
+	while (bytes_to_write > 0) {
+		const size_t	bytes_written = write_fun(handle, p, bytes_to_write);
+		bytes_to_write -= bytes_written;
+		p += bytes_written;
+	}
+
+	reset_buffer();
+
+	return traits_type::to_int_type(0);
+}
+
+int		ofhbuf::sync ()
+{
+	return !is_eof(overflow(traits_type::eof())) ? 0 : -1;
+}
+
+std::streamsize	ofhbuf::xsputn (const char* s, std::streamsize n)
+{
+	// Use heuristic to decide whether to write directly or just use buffer
+	// Write directly only if n >= MIN(4096, available buffer capacity)
+	// (this is similar to what basic_filebuf does)
+
+	if (n < std::min<std::streamsize>(4096, epptr() - pptr())) {
+		// Not worth it to do a direct write
+		return std::streambuf::xsputn(s, n);
+	}
+
+	// Before we can do a direct write of this string, we need to flush
+	// out the current contents of the buffer.
+	if (pbase() != pptr()) {
+		overflow(traits_type::eof()); // throws an exception or it succeeds
+	}
+
+	// Now we can go ahead and write out the string.
+	size_t		bytes_to_write = n;
+
+	while (bytes_to_write > 0) {
+		const size_t	bytes_written = write_fun(handle, s, bytes_to_write);
+		bytes_to_write -= bytes_written;
+		s += bytes_written;
+	}
+
+	return n; // Return the total bytes written
+}
+
+std::streambuf*	ofhbuf::setbuf (char* s, std::streamsize n)
+{
+	if (s == 0 && n == 0) {
+		// Switch to unbuffered
+		// This won't take effect until the next overflow or sync
+		// (We defer it taking effect so that write errors can be properly reported)
+		// To cause it to take effect as soon as possible, we artificially reduce the
+		// size of the buffer so it has no space left.  This will trigger an overflow
+		// on the next put.
+		std::streambuf::setp(pbase(), pptr());
+		std::streambuf::pbump(pptr() - pbase());
+		buffer_size = 1;
+	}
+	return this;
+}
+
+
+
+/*
+ * ifhstream
+ */
+
+ifhbuf::ifhbuf (void* arg_handle, size_t (*arg_read_fun)(void*, void*, size_t))
+: handle(arg_handle),
+  read_fun(arg_read_fun),
+  buffer(new char[default_buffer_size + putback_size]),
+  buffer_size(default_buffer_size)
+{
+	reset_buffer(0, 0);
+}
+
+ifhbuf::~ifhbuf ()
+{
+	delete[] buffer;
+}
+
+ifhbuf::int_type	ifhbuf::underflow ()
+{
+	if (gptr() >= egptr()) { // A true underflow (no bytes in buffer left to read)
+
+		// Move the putback_size most-recently-read characters into the putback area
+		size_t		nputback = std::min<size_t>(gptr() - eback(), putback_size);
+		std::memmove(buffer + (putback_size - nputback), gptr() - nputback, nputback);
+
+		// Now read new characters from the file descriptor
+		const size_t	nread = read_fun(handle, buffer + putback_size, buffer_size);
+		if (nread == 0) {
+			// EOF
+			return traits_type::eof();
+		}
+
+		// Reset the buffer
+		reset_buffer(nputback, nread);
+	}
+
+	// Return the next character
+	return traits_type::to_int_type(*gptr());
+}
+
+std::streamsize	ifhbuf::xsgetn (char* s, std::streamsize n)
+{
+	// Use heuristic to decide whether to read directly
+	// Read directly only if n >= bytes_available + 4096
+
+	std::streamsize	bytes_available = egptr() - gptr();
+
+	if (n < bytes_available + 4096) {
+		// Not worth it to do a direct read
+		return std::streambuf::xsgetn(s, n);
+	}
+
+	std::streamsize	total_bytes_read = 0;
+
+	// First, copy out the bytes currently in the buffer
+	std::memcpy(s, gptr(), bytes_available);
+
+	s += bytes_available;
+	n -= bytes_available;
+	total_bytes_read += bytes_available;
+
+	// Now do the direct read
+	while (n > 0) {
+		const size_t	bytes_read = read_fun(handle, s, n);
+		if (bytes_read == 0) {
+			// EOF
+			break;
+		}
+
+		s += bytes_read;
+		n -= bytes_read;
+		total_bytes_read += bytes_read;
+	}
+
+	// Fill up the putback area with the most recently read characters
+	size_t		nputback = std::min<size_t>(total_bytes_read, putback_size);
+	std::memcpy(buffer + (putback_size - nputback), s - nputback, nputback);
+
+	// Reset the buffer with no bytes available for reading, but with some putback characters
+	reset_buffer(nputback, 0);
+
+	// Return the total number of bytes read
+	return total_bytes_read;
+}
+
+std::streambuf*	ifhbuf::setbuf (char* s, std::streamsize n)
+{
+	if (s == 0 && n == 0) {
+		// Switch to unbuffered
+		// This won't take effect until the next underflow (we don't want to
+		// lose what's currently in the buffer!)
+		buffer_size = 1;
+	}
+	return this;
+}