minimal plan9port to cross-build Jehanne

lib/lib9/getns.c

@@ -0,0 +1,97 @@
+#include <u.h>
+#include <libc.h>
+#include <ctype.h>
+
+static int
+isme(char *uid)
+{
+	int n;
+	char *p;
+
+	n = strtol(uid, &p, 10);
+	if(*p == 0 && p > uid)
+		return n == getuid();
+	return strcmp(getuser(), uid) == 0;
+}
+/*
+ * Absent other hints, it works reasonably well to use
+ * the X11 display name as the name space identifier.
+ * This is how sam's B has worked since the early days.
+ * Since most programs using name spaces are also using X,
+ * this still seems reasonable.  Terminal-only sessions
+ * can set $NAMESPACE.
+ */
+static char*
+nsfromdisplay(void)
+{
+	int fd;
+	Dir *d;
+	char *disp, *p;
+
+	if((disp = getenv("DISPLAY")) == nil){
+#ifdef __APPLE__
+		// Might be running native GUI on OS X.
+		disp = strdup(":0.0");
+		if(disp == nil)
+			return nil;
+#else
+		werrstr("$DISPLAY not set");
+		return nil;
+#endif
+	}
+
+	/* canonicalize: xxx:0.0 => xxx:0 */
+	p = strrchr(disp, ':');
+	if(p){
+		p++;
+		while(isdigit((uchar)*p))
+			p++;
+		if(strcmp(p, ".0") == 0)
+			*p = 0;
+	}
+
+	/* turn /tmp/launch/:0 into _tmp_launch_:0 (OS X 10.5) */
+	for(p=disp; *p; p++)
+		if(*p == '/')
+			*p = '_';
+
+	p = smprint("/tmp/ns.%s.%s", getuser(), disp);
+	free(disp);
+	if(p == nil){
+		werrstr("out of memory");
+		return p;
+	}
+	if((fd=create(p, OREAD, DMDIR|0700)) >= 0){
+		close(fd);
+		return p;
+	}
+	if((d = dirstat(p)) == nil){
+		free(d);
+		werrstr("stat %s: %r", p);
+		free(p);
+		return nil;
+	}
+	if((d->mode&0777) != 0700 || !isme(d->uid)){
+		werrstr("bad name space dir %s", p);
+		free(p);
+		free(d);
+		return nil;
+	}
+	free(d);
+	return p;
+}
+
+char*
+getns(void)
+{
+	char *ns;
+
+	ns = getenv("NAMESPACE");
+	if(ns == nil)
+		ns = nsfromdisplay();
+	if(ns == nil){
+		werrstr("$NAMESPACE not set, %r");
+		return nil;
+	}
+	return ns;
+}