add directory study

study/linux-travel/minix-386/estdio21.tar/estdio21/_open3.c

@@ -0,0 +1,76 @@
+/*                               _ o p e n 3                               */
+
+/* For those ancient systems without three argument opens, we fake it.
+ * The following code works for:
+ *
+ *		r  O_RDONLY
+ *		w  O_WRONLY | O_CREAT | O_TRUNC
+ *		a  O_WRONLY | O_CREAT | O_APPEND
+ *		r+ O_RDWR
+ *		w+ O_RDWR   | O_CREAT | O_TRUNC
+ *		a+ O_RDWR   | O_CREAT | O_APPEND
+ *	other modes may not work
+ *
+ * Code based on open3.c from Bruce Evan's stdio. It is necessary to
+ * set the umask to zero so that creat works implies that open works.
+ * The O_APPEND mode is ignored since two argument opens don't support
+ * it at all.
+ */
+
+#include "stdiolib.h"
+
+/*LINTLIBRARY*/
+/*VARARGS2*/
+/*ARGSUSED*/
+
+#ifndef		OPEN3
+
+#undef open
+
+int __open3 F2V(CONST char *, path, int, mode,
+
+{
+  VA_LIST, arg,				/* argument vector */
+  register int fd;			/* file descriptor */
+  register int fmode;			/* file mode */
+  int mask;				/* saved umask */
+  int perms;				/* permissions */
+
+  VA_START(arg, mode);)
+
+/* Take fast local copy of mode */
+  fmode = mode;
+
+/* r, a, r+ and a+ modes */
+  if ((fmode & O_TRUNC) == 0) {
+    if ((fd = open(path, fmode & (O_WRONLY|O_RDONLY|O_RDWR))) >= 0 ||
+	(fmode & O_CREAT) == 0                                     ||
+	errno != ENOENT)
+      goto Done;
+
+/* Fall through on a and a+ modes => couldn't open because ENOENT */
+  }
+
+/* Extract file permissions */
+  perms = VA_ARG(arg, int);
+
+/* w and a modes */
+  if ((fmode & (O_WRONLY|O_RDONLY|O_RDWR)) != O_RDWR)
+      fd = creat(path, perms);
+
+/* w+ and a+ modes */
+  else {
+      mask = umask(0);
+      if ((fd = creat(path, perms)) >= 0) {
+	  (void) close(fd);
+	  fd = open(path, O_RDWR);
+	  (void) chmod(path, ~mask & perms);
+      }
+      (void) umask(mask);
+  }
+
+Done:
+  VA_END(arg);
+  return fd;
+}
+#endif