From 59e902394af94d57fcd83fb1c70c97768c275567 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <daniel.goodliffe@pressassociation.com>
Date: Fri, 28 Aug 2015 00:09:51 +0100
Subject: Add ProcessPipes as a container for a child process with FDs for
 stdin, out and err

---
 libadhocutil/processPipes.cpp               | 138 ++++++++++++++++++++++++++++
 libadhocutil/processPipes.h                 |  33 +++++++
 libadhocutil/unittests/Jamfile.jam          |  13 +++
 libadhocutil/unittests/testProcessPipes.cpp |  23 +++++
 4 files changed, 207 insertions(+)
 create mode 100644 libadhocutil/processPipes.cpp
 create mode 100644 libadhocutil/processPipes.h
 create mode 100644 libadhocutil/unittests/testProcessPipes.cpp

diff --git a/libadhocutil/processPipes.cpp b/libadhocutil/processPipes.cpp
new file mode 100644
index 0000000..55050ae
--- /dev/null
+++ b/libadhocutil/processPipes.cpp
@@ -0,0 +1,138 @@
+#include "processPipes.h"
+#include <unistd.h>
+#include <poll.h>
+#include <string.h>
+#include <sys/resource.h>
+#include <stdexcept>
+
+ProcessPipes::ProcessPipes(const std::vector<std::string> & args, bool i, bool o, bool e) :
+	in(-1),
+	out(-1),
+	error(-1)
+{
+	int ipipes[2], opipes[2], epipes[2];
+	if (i) {
+		if (pipe(ipipes)) {
+			throw std::runtime_error("Failed to create stdin pipe");
+		}
+	}
+	if (o) {
+		if (pipe(opipes)) {
+			if (i) {
+				close(ipipes[0]);
+				close(ipipes[1]);
+			}
+			throw std::runtime_error("Failed to create stdout pipe");
+		}
+	}
+	if (e) {
+		if (pipe(epipes)) {
+			if (i) {
+				close(ipipes[0]);
+				close(ipipes[1]);
+			}
+			if (o) {
+				close(opipes[0]);
+				close(opipes[1]);
+			}
+			throw std::runtime_error("Failed to create stderr pipe");
+		}
+	}
+	switch (child = fork()) {
+		case -1: // fail
+			if (i) {
+				close(ipipes[0]);
+				close(ipipes[1]);
+			}
+			if (o) {
+				close(opipes[0]);
+				close(opipes[1]);
+			}
+			if (e) {
+				close(epipes[0]);
+				close(epipes[1]);
+			}
+			throw std::runtime_error("Failed to fork");
+		default: // parent
+			if (i) {
+				close(ipipes[0]);
+				in = ipipes[1];
+			}
+			if (o) {
+				close(opipes[1]);
+				out = opipes[0];
+			}
+			if (e) {
+				close(epipes[1]);
+				error = epipes[0];
+			}
+			break;
+		case 0: // in child
+			rlimit lim;
+			getrlimit(RLIMIT_NOFILE, &lim);
+			if (i) {
+				close(ipipes[1]);
+				dup2(ipipes[0], 0);
+			}
+			if (o) {
+				close(opipes[0]);
+				dup2(opipes[1], 1);
+			}
+			if (e) {
+				close(epipes[0]);
+				dup2(epipes[1], 2);
+			}
+			std::vector<struct pollfd> fds;
+			fds.reserve(lim.rlim_max);
+			for (int n = 3; n < (int)lim.rlim_max; n += 1) {
+				fds.push_back({n, 0, 0});
+			}
+			poll(&fds.front(), fds.size(), 0);
+			for(const auto & pfd : fds) {
+				if (!(pfd.revents & POLLNVAL)) {
+					close(pfd.fd);
+				}
+			}
+			char * buf[100];
+			char ** w = &buf[0];
+			for (const auto & p : args) {
+				*w++ = strdup(p.c_str());
+			}
+			*w = NULL;
+			execv(buf[0], buf);
+			abort();
+			break;
+	}
+}
+
+ProcessPipes::~ProcessPipes()
+{
+	if (in) close(in);
+	if (out) close(out);
+	if (error) close(error);
+}
+
+int
+ProcessPipes::fdIn() const
+{
+	return in;
+}
+
+int
+ProcessPipes::fdOut() const
+{
+	return out;
+}
+
+int
+ProcessPipes::fdError() const
+{
+	return error;
+}
+
+pid_t
+ProcessPipes::pid() const
+{
+	return child;
+}
+
diff --git a/libadhocutil/processPipes.h b/libadhocutil/processPipes.h
new file mode 100644
index 0000000..a1d0800
--- /dev/null
+++ b/libadhocutil/processPipes.h
@@ -0,0 +1,33 @@
+#ifndef ADHOCUTIL_PROCESSPIPES_H
+#define ADHOCUTIL_PROCESSPIPES_H
+
+#include <vector>
+#include <string>
+#include "visibility.h"
+
+/**
+ * Spawn a new process, providing access to it's stdin and stdout
+ * @param params path and arguments to spawn (copied and passed to execv)
+ * @param fds (out) the FDs on the childs stdin(0) and stdout(1)
+ * @return the process ID of the child
+ */
+class DLL_PUBLIC ProcessPipes {
+	public:
+		ProcessPipes(const std::vector<std::string> & args, bool in, bool out, bool err);
+		~ProcessPipes();
+
+		ProcessPipes(const ProcessPipes &) = delete;
+		void operator=(const ProcessPipes &) = delete;
+
+		int fdIn() const;
+		int fdOut() const;
+		int fdError() const;
+		pid_t pid() const;
+
+	private:
+		int in, out, error;
+		pid_t child;
+};
+
+#endif
+
diff --git a/libadhocutil/unittests/Jamfile.jam b/libadhocutil/unittests/Jamfile.jam
index 8332544..de5336e 100644
--- a/libadhocutil/unittests/Jamfile.jam
+++ b/libadhocutil/unittests/Jamfile.jam
@@ -40,3 +40,16 @@ run
 	testBuffer
 	;
 
+run
+	testProcessPipes.cpp
+	: : :
+	<define>BOOST_TEST_DYN_LINK
+	<define>ROOT=\"$(me)\"
+	<library>..//adhocutil
+	<library>boost_utf
+	<library>boost_filesystem
+	<library>boost_system
+	:
+	testProcessPipes
+	;
+
diff --git a/libadhocutil/unittests/testProcessPipes.cpp b/libadhocutil/unittests/testProcessPipes.cpp
new file mode 100644
index 0000000..7131e70
--- /dev/null
+++ b/libadhocutil/unittests/testProcessPipes.cpp
@@ -0,0 +1,23 @@
+#define BOOST_TEST_MODULE ProcessPipes
+#include <boost/test/unit_test.hpp>
+
+#include "processPipes.h"
+#include "definedDirs.h"
+#include <sys/wait.h>
+
+BOOST_AUTO_TEST_CASE ( readfind )
+{
+	ProcessPipes pp({"/usr/bin/find", RootDir.string(), "-maxdepth", "1"}, false, true, true);
+	BOOST_REQUIRE_EQUAL(pp.fdIn(), -1);
+	BOOST_REQUIRE(pp.fdOut() != -1);
+	BOOST_REQUIRE(pp.fdError() != -1);
+	char buf[BUFSIZ];
+	ssize_t bytes = read(pp.fdOut(), buf, BUFSIZ);
+	BOOST_REQUIRE_MESSAGE(bytes > 0, "bytes = " << bytes);
+	buf[bytes] = '\0';
+	char * lnf = strstr(buf, "testProcessPipes.cpp");
+	BOOST_REQUIRE_MESSAGE(lnf, buf);
+	int status;
+	waitpid(pp.pid(), &status, 0);
+}
+
-- 
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