1 files changed, 60 insertions, 0 deletions
diff --git a/src/rsvr.c b/src/rsvr.c
new file mode 100644
index 0000000..01fa845
--- /dev/null
+++ b/src/rsvr.c
@@ -0,0 +1,60 @@
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+
+char buf[128*1024];
+
+int main(int argc, char *argv[])
+{
+	if( 2 > argc ){
+		fprintf(stderr,
+			"Read stdin into a memfd reservoir file and use this as stdin for a subsequently executed command.\n"
+			"usage: %s <command and argument>\n",
+			(argc ? argv[0] : "rsvr") );
+		return EXIT_FAILURE;
+	}
+
+	int rsvr_fd = memfd_create("reservoiur", MFD_CLOEXEC);
+	if( 0 > rsvr_fd ){
+		perror("memfd_create('reservoiur', MFD_CLOEXEC)"); 
+		return EXIT_FAILURE;
+	}
+
+	ssize_t rb = 0, wb = 0;
+	do {
+		rb = read(0, buf, sizeof(buf));
+		if( 0 >= rb ){ continue; }
+
+		for( ssize_t cb = 0
+		   ; 0 <= wb && (cb < rb)
+		   ; cb += ((0 < wb) ? wb : 0)
+		){
+			wb = write(rsvr_fd, (buf+cb), (rb-cb));
+			if( (0 > wb) && (EINTR == errno) ){ wb = 0; }
+		}
+	} while( (0 < rb)
+	      || (0 > rb) && EINTR == errno );
+
+	if( 0 > rb ){ perror("read(stdin)"); }
+	if( 0 > wb ){ perror("write(reservoir)"); }
+	if( 0 > rb || 0 > wb ){ return EXIT_FAILURE; }
+
+	if( 0 > dup2(rsvr_fd, 0) ){
+		perror("dup2(reservoir, stdin)");
+		return EXIT_FAILURE;
+	}
+	close(rsvr_fd);
+
+	memmove(argv, argv+1, sizeof(*argv)*(argc-1));
+	argv[argc-1] = NULL;
+	if( 0 > execvp(argv[0], argv) ){
+		perror("exec(...)");
+	}
+
+	return EXIT_FAILURE;
+}