Add an extensible version of our *printf(3) implementation to libc

on probationary terms:  it may go away again if it transpires it is
a bad idea.

This extensible printf version will only be used if either
    environment variable USE_XPRINTF is defined
or
    one of the extension functions are called.
or
    the global variable __use_xprintf is set greater than zero.

In all other cases our traditional printf implementation will
be used.

The extensible version is slower than the default printf, mostly
because less opportunity for combining I/O operation exists when
faced with extensions.  The default printf on the other hand
is a bad case of spaghetti code.

The extension API has a GLIBC compatible part and a FreeBSD version
of same.  The FreeBSD version exists because the GLIBC version may
run afoul of our FILE * locking in multithreaded programs and it
even further eliminate the opportunities for combining I/O operations.

Include three demo extensions which can be enabled if desired: time
(%T), hexdump (%H) and strvis (%V).

%T can format time_t (%T), struct timeval (%lT) and struct timespec (%llT)
   in one of two human readable duration formats:
	"%.3llT" -> "20349.245"
	"%#.3llT" -> "5h39m9.245"

%H will hexdump a sequence of bytes and takes a pointer and a length
   argument.  The width specifies number of bytes per line.
	"%4H" -> "65 72 20 65"
	"%+4H" -> "0000 65 72 20 65"
	"%#4H" -> "65 72 20 65  |er e|"
	"%+#4H" -> "0000 65 72 20 65  |er e|"

%V will dump a string in strvis format.
	"%V" -> "Hello\tWor\377ld"	(C-style)
	"%0V" -> "Hello\011Wor\377ld"	(octal)
	"%+V" -> "Hello%09Wor%FFld"	(http-style)

Tests, comments, bugreports etc are most welcome.

1 files changed, 76 insertions, 0 deletions

diff --git a/lib/libc/stdio/xprintf_vis.c b/lib/libc/stdio/xprintf_vis.c
new file mode 100644
index 0000000..2f8d63e
--- /dev/null
+++ b/lib/libc/stdio/xprintf_vis.c
@@ -0,0 +1,76 @@
+/*-
+ * Copyright (c) 2005 Poul-Henning Kamp
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include <namespace.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <wchar.h>
+#include <vis.h>
+#include <assert.h>
+#include <sys/time.h>
+#include "printf.h"
+
+int
+__printf_arginfo_vis(const struct printf_info *pi, size_t n, int *argt)
+{
+
+	assert(n >= 1);
+	argt[0] = PA_POINTER;
+	return (1);
+}
+
+int
+__printf_render_vis(struct __printf_io *io, const struct printf_info *pi, const void *const *arg)
+{
+	char *p, *buf;
+	unsigned l;
+	int ret;
+
+	ret = 0;
+	p = *((char **)arg[0]);
+	if (pi->prec >= 0)
+		l = pi->prec;
+	else
+		l = strlen(p);
+	buf = malloc(l * 4 + 1);
+	if (buf == NULL)
+		return (-1);
+	if (pi->showsign)
+		ret = strvisx(buf, p, l, VIS_WHITE | VIS_HTTPSTYLE);
+	else if (pi->pad == '0')
+		ret = strvisx(buf, p, l, VIS_WHITE | VIS_OCTAL);
+	else if (pi->alt)
+		ret = strvisx(buf, p, l, VIS_WHITE);
+	else
+		ret = strvisx(buf, p, l, VIS_WHITE | VIS_CSTYLE | VIS_OCTAL);
+	ret += __printf_out(io, pi, buf, ret);
+	__printf_flush(io);
+	free(buf);
+	return(ret);
+}