Standalone POSIX pipe utility

Pipe between files using POSIX stdio. This facilitates raw transfers
between arbitrary resources exposed by the VFS library.

Fix #2708

repos/gems/recipes/src/pipe/content.mk

@@ -0,0 +1,2 @@
+SRC_DIR = src/app/pipe
+include $(GENODE_DIR)/repos/base/recipes/src/content.inc

repos/gems/recipes/src/pipe/hash

@@ -0,0 +1 @@
+-

repos/gems/recipes/src/pipe/used_apis

@@ -0,0 +1,3 @@
+base
+libc
+posix

repos/gems/run/pipe.run

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+create_boot_directory
+
+install_config {
+<config>
+	<parent-provides>
+		<service name="CPU"/>
+		<service name="IO_MEM"/>
+		<service name="IO_PORT"/>
+		<service name="IRQ"/>
+		<service name="LOG"/>
+		<service name="PD"/>
+		<service name="RM"/>
+		<service name="ROM"/>
+	</parent-provides>
+	<default-route>
+		<any-service> <parent/> <any-child/> </any-service>
+	</default-route>
+	<start name="pipe" caps="128">
+		<resource name="RAM" quantum="2M"/>
+		<config>
+			<vfs>
+				<rom name="config"/>
+				<dir name="dev"> <log/> </dir>
+			</vfs>
+			<libc stdin="/config" stdout="/dev/log"/>
+		</config>
+	</start>
+</config>
+}
+
+build "core init app/pipe"
+
+build_boot_image {
+	core init pipe
+	ld.lib.so libc.lib.so libm.lib.so posix.lib.so
+}
+
+append qemu_args " -nographic  "
+
+run_genode_until "child .* exited with exit value 0.*\n" 10

repos/gems/src/app/pipe/README

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+The pipe utility is for piping between files using the
+semantics of POSIX stdio.
+
+An example of piping clock jitter to a terminal session:
+
+! <start name="pipe">
+!   <resource name="RAM" quantum="2M"/>
+!   <config>
+!     <vfs>
+!       <jitterentropy name="rng"/>
+!       <terminal name="tty"/>
+!     </vfs>
+!     <libc stdin="/rng" stdout="/tty"/>
+!   </config>
+! </start>

repos/gems/src/app/pipe/main.cc

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+/*
+ * \brief  Standalone POSIX pipe
+ * \author Emery Hemingway
+ * \date   2018-03-06
+ */
+
+/*
+ * Copyright (C) 2018 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+/* Genode includes */
+#include <base/log.h>
+
+/* Libc includes */
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+int main()
+{
+	enum { SIXTEEN_K = 1 << 14 };
+	static char buf[SIXTEEN_K];
+
+	Genode::uint64_t total = 0;
+
+	while (true) {
+
+		auto const nr = fread(buf, 1, sizeof(buf), stdin);
+		if (nr == 0 && feof(stdin))
+			break;
+
+		if (nr < 1 || nr > sizeof(buf)) {
+			int res = errno;
+			Genode::error((char const *)strerror(res));
+			return res;
+		}
+
+		auto remain = nr;
+		auto off = 0;
+		while (remain > 0) {
+			auto const nw = fwrite(buf+off, 1, remain, stdout);
+			if (nw < 1 || nw > remain) {
+				int res = errno;
+				Genode::error((char const *)strerror(res));
+				return res;
+			}
+
+			remain -= nw;
+			off += nw;
+			total += nw;
+		}
+	}
+
+	Genode::log("piped ", total, " bytes");
+	return 0;
+};

repos/gems/src/app/pipe/target.mk

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+TARGET = pipe
+SRC_CC = main.cc
+LIBS   = base libc posix