Add proper const keywords to sysctl(3) parameters.

The `name' and `newp' arguments can be marked const, because the buffers
they refer to are never changed. While there, perform some other
cleanups:

- Remove K&R from sysctl.c.
- Implement sysctlbyname() using sysctlnametomib() to prevent
  duplication of an undocumented kernel interface.
- Fix some whitespace nits.

It seems the prototypes are now in sync with NetBSD as well.

lib/libc/gen/sysctl.3

@@ -28,7 +28,7 @@
 .\"	@(#)sysctl.3	8.4 (Berkeley) 5/9/95
 .\" $FreeBSD$
 .\"
-.Dd January 28, 2009
+.Dd February 21, 2010
 .Dt SYSCTL 3
 .Os
 .Sh NAME
@@ -42,9 +42,9 @@
 .In sys/types.h
 .In sys/sysctl.h
 .Ft int
-.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
+.Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
 .Ft int
-.Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
+.Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
 .Ft int
 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
 .Sh DESCRIPTION

lib/libc/gen/sysctl.c

@@ -43,15 +43,12 @@ __FBSDID("$FreeBSD$");
 #include <unistd.h>
 #include <string.h>
 
-extern int __sysctl(int *name, u_int namelen, void *oldp, size_t *oldlenp,
-    void *newp, size_t newlen);
+extern int __sysctl(const int *name, u_int namelen, void *oldp,
+    size_t *oldlenp, const void *newp, size_t newlen);
 
 int
-sysctl(name, namelen, oldp, oldlenp, newp, newlen)
-	int *name;
-	u_int namelen;
-	void *oldp, *newp;
-	size_t *oldlenp, newlen;
+sysctl(const int *name, u_int namelen, void *oldp, size_t *oldlenp,
+    const void *newp, size_t newlen)
 {
 	if (name[0] != CTL_USER)
 		return (__sysctl(name, namelen, oldp, oldlenp, newp, newlen));

lib/libc/gen/sysctlbyname.c

@@ -13,26 +13,19 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/types.h>
 #include <sys/sysctl.h>
-#include <string.h>
 
 int
-sysctlbyname(const char *name, void *oldp, size_t *oldlenp, void *newp,
-	     size_t newlen)
+sysctlbyname(const char *name, void *oldp, size_t *oldlenp,
+    const void *newp, size_t newlen)
 {
-	int name2oid_oid[2];
 	int real_oid[CTL_MAXNAME+2];
 	int error;
 	size_t oidlen;
 
-	name2oid_oid[0] = 0;	/* This is magic & undocumented! */
-	name2oid_oid[1] = 3;
-
-	oidlen = sizeof(real_oid);
-	error = sysctl(name2oid_oid, 2, real_oid, &oidlen, (void *)name,
-		       strlen(name));
+	oidlen = sizeof(real_oid) / sizeof(int);
+	error = sysctlnametomib(name, real_oid, &oidlen);
 	if (error < 0) 
-		return error;
-	oidlen /= sizeof (int);
+		return (error);
 	error = sysctl(real_oid, oidlen, oldp, oldlenp, newp, newlen);
 	return (error);
 }

lib/libc/gen/sysctlnametomib.c

@@ -48,8 +48,8 @@ sysctlnametomib(const char *name, int *mibp, size_t *sizep)
 	oid[0] = 0;
 	oid[1] = 3;
 
-	*sizep *= sizeof (int);
-	error = sysctl(oid, 2, mibp, sizep, (void *)name, strlen(name));
-	*sizep /= sizeof (int);
+	*sizep *= sizeof(int);
+	error = sysctl(oid, 2, mibp, sizep, name, strlen(name));
+	*sizep /= sizeof(int);
 	return (error);
 }

sys/sys/sysctl.h

@@ -714,8 +714,8 @@ int	sysctl_wire_old_buffer(struct sysctl_req *req, size_t len);
 #include <sys/cdefs.h>
 
 __BEGIN_DECLS
-int	sysctl(int *, u_int, void *, size_t *, void *, size_t);
-int	sysctlbyname(const char *, void *, size_t *, void *, size_t);
+int	sysctl(const int *, u_int, void *, size_t *, const void *, size_t);
+int	sysctlbyname(const char *, void *, size_t *, const void *, size_t);
 int	sysctlnametomib(const char *, int *, size_t *);
 __END_DECLS
 #endif	/* _KERNEL */