Implement a much more capable vuprintf()

New support as well as some buggy support fixed.

Still no floating point support if ever that would be desired.

Support (*):
* Flags: '-', '+', ' ', '#', '0'

* Width and precision: 'n', '.n', '*' and '.*'

* Length modifiers: 'hh', 'h', 'j', 'l', 'll', 't', 'z'

* Radix: 'c', 'd', 'i', 'n', 'o', 'p/P', 's', 'u', 'x/X'

(*) Provision exists to switch lesser-used stuff on or off or when
certain functionality isn't desired (bootloader?). The compulsory
radixes are everything but 'o', 'n', 'p/P' and 'x/X' with length
modifiers being optional. The default setup is 'l', 'z', 'c', 'd',
'p/P', 's', 'u', 'x/X'.

* Move fdprintf() to its own file. It was in a strange place.

* Make callers compatible and fix a couple snprintf() bugs while
at it.

Could smush it down in size but I'm gonna get over the binsize
neurosis and just the let optimizer do its thing.

Change-Id: Ibdc613a9b6775802c188b29b9dd46c568c94f7c3

firmware/common/fdprintf.c

@@ -0,0 +1,56 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2002 by Felix Arends
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include <limits.h>
+#include "file.h"
+#include "vuprintf.h"
+
+struct for_fprintf {
+    int fd;  /* where to store it */
+    int rem; /* amount remaining */
+};
+
+static int fprfunc(void *pr, int letter)
+{
+    struct for_fprintf *fpr  = (struct for_fprintf *)pr;
+
+    /* TODO: add a small buffer to reduce write() calls */
+    if (write(fpr->fd, &(char){ letter }, 1) > 0) {
+        return --fpr->rem;
+    }
+
+    return -1;
+}
+
+int fdprintf(int fd, const char *fmt, ...)
+{
+    int bytes;
+    struct for_fprintf fpr;
+    va_list ap;
+
+    fpr.fd  = fd;
+    fpr.rem = INT_MAX;
+
+    va_start(ap, fmt);
+    bytes = vuprintf(fprfunc, &fpr, fmt, ap);
+    va_end(ap);
+
+    return bytes;
+}