Date:   Wed, 24 Jun 2020 03:01:52 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     netdev <netdev@...r.kernel.org>, Chris Healy <cphealy@...il.com>,
        Andrew Lunn <andrew@...n.ch>
Subject: [PATCH ethtool v1 3/6] json_writer: Import the iproute2 helper code for JSON output

In general, Linux network tools use JSON for machine readable output.
See for example -json for iproute2 and devlink. In order to support
JSON output from ethtool, import the iproute2 helper code.

Maybe some time in the future it would make sense to either have a
shared library, or to merge ethtool into the iproute2 source
distribution?

Signed-off-by: Andrew Lunn <andrew@...n.ch>
---
 Makefile.am   |   3 +-
 json_writer.c | 389 ++++++++++++++++++++++++++++++++++++++++++++++++++
 json_writer.h |  76 ++++++++++
 3 files changed, 467 insertions(+), 1 deletion(-)
 create mode 100644 json_writer.c
 create mode 100644 json_writer.h

diff --git a/Makefile.am b/Makefile.am
index a818cf8..7edbd5b 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -7,7 +7,8 @@ EXTRA_DIST = LICENSE ethtool.8 ethtool.spec.in aclocal.m4 ChangeLog autogen.sh
 
 sbin_PROGRAMS = ethtool
 ethtool_SOURCES = ethtool.c uapi/linux/ethtool.h internal.h \
-		  uapi/linux/net_tstamp.h rxclass.c common.c common.h
+		  uapi/linux/net_tstamp.h rxclass.c common.c common.h \
+		  json_writer.c  json_writer.h
 if ETHTOOL_ENABLE_PRETTY_DUMP
 ethtool_SOURCES += \
 		  amd8111e.c de2104x.c dsa.c e100.c e1000.c et131x.c igb.c	\
diff --git a/json_writer.c b/json_writer.c
new file mode 100644
index 0000000..88c5eb8
--- /dev/null
+++ b/json_writer.c
@@ -0,0 +1,389 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) */
+/*
+ * Simple streaming JSON writer
+ *
+ * This takes care of the annoying bits of JSON syntax like the commas
+ * after elements
+ *
+ * Authors:	Stephen Hemminger <stephen@...workplumber.org>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <stdarg.h>
+#include <assert.h>
+#include <malloc.h>
+#include <inttypes.h>
+#include <stdint.h>
+
+#include "json_writer.h"
+
+struct json_writer {
+	FILE		*out;	/* output file */
+	unsigned	depth;  /* nesting */
+	bool		pretty; /* optional whitepace */
+	char		sep;	/* either nul or comma */
+};
+
+/* indentation for pretty print */
+static void jsonw_indent(json_writer_t *self)
+{
+	unsigned i;
+	for (i = 0; i < self->depth; ++i)
+		fputs("    ", self->out);
+}
+
+/* end current line and indent if pretty printing */
+static void jsonw_eol(json_writer_t *self)
+{
+	if (!self->pretty)
+		return;
+
+	putc('\n', self->out);
+	jsonw_indent(self);
+}
+
+/* If current object is not empty print a comma */
+static void jsonw_eor(json_writer_t *self)
+{
+	if (self->sep != '\0')
+		putc(self->sep, self->out);
+	self->sep = ',';
+}
+
+
+/* Output JSON encoded string */
+/* Handles C escapes, does not do Unicode */
+static void jsonw_puts(json_writer_t *self, const char *str)
+{
+	putc('"', self->out);
+	for (; *str; ++str)
+		switch (*str) {
+		case '\t':
+			fputs("\\t", self->out);
+			break;
+		case '\n':
+			fputs("\\n", self->out);
+			break;
+		case '\r':
+			fputs("\\r", self->out);
+			break;
+		case '\f':
+			fputs("\\f", self->out);
+			break;
+		case '\b':
+			fputs("\\b", self->out);
+			break;
+		case '\\':
+			fputs("\\\\", self->out);
+			break;
+		case '"':
+			fputs("\\\"", self->out);
+			break;
+		case '\'':
+			fputs("\\\'", self->out);
+			break;
+		default:
+			putc(*str, self->out);
+		}
+	putc('"', self->out);
+}
+
+/* Create a new JSON stream */
+json_writer_t *jsonw_new(FILE *f)
+{
+	json_writer_t *self = malloc(sizeof(*self));
+	if (self) {
+		self->out = f;
+		self->depth = 0;
+		self->pretty = false;
+		self->sep = '\0';
+	}
+	return self;
+}
+
+/* End output to JSON stream */
+void jsonw_destroy(json_writer_t **self_p)
+{
+	json_writer_t *self = *self_p;
+
+	assert(self->depth == 0);
+	fputs("\n", self->out);
+	fflush(self->out);
+	free(self);
+	*self_p = NULL;
+}
+
+void jsonw_pretty(json_writer_t *self, bool on)
+{
+	self->pretty = on;
+}
+
+/* Basic blocks */
+static void jsonw_begin(json_writer_t *self, int c)
+{
+	jsonw_eor(self);
+	putc(c, self->out);
+	++self->depth;
+	self->sep = '\0';
+}
+
+static void jsonw_end(json_writer_t *self, int c)
+{
+	assert(self->depth > 0);
+
+	--self->depth;
+	if (self->sep != '\0')
+		jsonw_eol(self);
+	putc(c, self->out);
+	self->sep = ',';
+}
+
+
+/* Add a JSON property name */
+void jsonw_name(json_writer_t *self, const char *name)
+{
+	jsonw_eor(self);
+	jsonw_eol(self);
+	self->sep = '\0';
+	jsonw_puts(self, name);
+	putc(':', self->out);
+	if (self->pretty)
+		putc(' ', self->out);
+}
+
+__attribute__((format(printf, 2, 3)))
+void jsonw_printf(json_writer_t *self, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	jsonw_eor(self);
+	vfprintf(self->out, fmt, ap);
+	va_end(ap);
+}
+
+/* Collections */
+void jsonw_start_object(json_writer_t *self)
+{
+	jsonw_begin(self, '{');
+}
+
+void jsonw_end_object(json_writer_t *self)
+{
+	jsonw_end(self, '}');
+}
+
+void jsonw_start_array(json_writer_t *self)
+{
+	jsonw_begin(self, '[');
+	if (self->pretty)
+		putc(' ', self->out);
+}
+
+void jsonw_end_array(json_writer_t *self)
+{
+	if (self->pretty && self->sep)
+		putc(' ', self->out);
+	self->sep = '\0';
+	jsonw_end(self, ']');
+}
+
+/* JSON value types */
+void jsonw_string(json_writer_t *self, const char *value)
+{
+	jsonw_eor(self);
+	jsonw_puts(self, value);
+}
+
+void jsonw_bool(json_writer_t *self, bool val)
+{
+	jsonw_printf(self, "%s", val ? "true" : "false");
+}
+
+void jsonw_null(json_writer_t *self)
+{
+	jsonw_printf(self, "null");
+}
+
+void jsonw_float(json_writer_t *self, double num)
+{
+	jsonw_printf(self, "%g", num);
+}
+
+void jsonw_hhu(json_writer_t *self, unsigned char num)
+{
+	jsonw_printf(self, "%hhu", num);
+}
+
+void jsonw_hu(json_writer_t *self, unsigned short num)
+{
+	jsonw_printf(self, "%hu", num);
+}
+
+void jsonw_uint(json_writer_t *self, unsigned int num)
+{
+	jsonw_printf(self, "%u", num);
+}
+
+void jsonw_u64(json_writer_t *self, uint64_t num)
+{
+	jsonw_printf(self, "%"PRIu64, num);
+}
+
+void jsonw_xint(json_writer_t *self, uint64_t num)
+{
+	jsonw_printf(self, "%"PRIx64, num);
+}
+
+void jsonw_luint(json_writer_t *self, unsigned long num)
+{
+	jsonw_printf(self, "%lu", num);
+}
+
+void jsonw_lluint(json_writer_t *self, unsigned long long num)
+{
+	jsonw_printf(self, "%llu", num);
+}
+
+void jsonw_int(json_writer_t *self, int num)
+{
+	jsonw_printf(self, "%d", num);
+}
+
+void jsonw_s64(json_writer_t *self, int64_t num)
+{
+	jsonw_printf(self, "%"PRId64, num);
+}
+
+/* Basic name/value objects */
+void jsonw_string_field(json_writer_t *self, const char *prop, const char *val)
+{
+	jsonw_name(self, prop);
+	jsonw_string(self, val);
+}
+
+void jsonw_bool_field(json_writer_t *self, const char *prop, bool val)
+{
+	jsonw_name(self, prop);
+	jsonw_bool(self, val);
+}
+
+void jsonw_float_field(json_writer_t *self, const char *prop, double val)
+{
+	jsonw_name(self, prop);
+	jsonw_float(self, val);
+}
+
+void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num)
+{
+	jsonw_name(self, prop);
+	jsonw_uint(self, num);
+}
+
+void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_u64(self, num);
+}
+
+void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_xint(self, num);
+}
+
+void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num)
+{
+	jsonw_name(self, prop);
+	jsonw_hhu(self, num);
+}
+
+void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num)
+{
+	jsonw_name(self, prop);
+	jsonw_hu(self, num);
+}
+
+void jsonw_luint_field(json_writer_t *self,
+			const char *prop,
+			unsigned long num)
+{
+	jsonw_name(self, prop);
+	jsonw_luint(self, num);
+}
+
+void jsonw_lluint_field(json_writer_t *self,
+			const char *prop,
+			unsigned long long num)
+{
+	jsonw_name(self, prop);
+	jsonw_lluint(self, num);
+}
+
+void jsonw_int_field(json_writer_t *self, const char *prop, int num)
+{
+	jsonw_name(self, prop);
+	jsonw_int(self, num);
+}
+
+void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num)
+{
+	jsonw_name(self, prop);
+	jsonw_s64(self, num);
+}
+
+void jsonw_null_field(json_writer_t *self, const char *prop)
+{
+	jsonw_name(self, prop);
+	jsonw_null(self);
+}
+
+#ifdef TEST
+int main(int argc, char **argv)
+{
+	json_writer_t *wr = jsonw_new(stdout);
+
+	jsonw_start_object(wr);
+	jsonw_pretty(wr, true);
+	jsonw_name(wr, "Vyatta");
+	jsonw_start_object(wr);
+	jsonw_string_field(wr, "url", "http://vyatta.com");
+	jsonw_uint_field(wr, "downloads", 2000000ul);
+	jsonw_float_field(wr, "stock", 8.16);
+
+	jsonw_name(wr, "ARGV");
+	jsonw_start_array(wr);
+	while (--argc)
+		jsonw_string(wr, *++argv);
+	jsonw_end_array(wr);
+
+	jsonw_name(wr, "empty");
+	jsonw_start_array(wr);
+	jsonw_end_array(wr);
+
+	jsonw_name(wr, "NIL");
+	jsonw_start_object(wr);
+	jsonw_end_object(wr);
+
+	jsonw_null_field(wr, "my_null");
+
+	jsonw_name(wr, "special chars");
+	jsonw_start_array(wr);
+	jsonw_string_field(wr, "slash", "/");
+	jsonw_string_field(wr, "newline", "\n");
+	jsonw_string_field(wr, "tab", "\t");
+	jsonw_string_field(wr, "ff", "\f");
+	jsonw_string_field(wr, "quote", "\"");
+	jsonw_string_field(wr, "tick", "\'");
+	jsonw_string_field(wr, "backslash", "\\");
+	jsonw_end_array(wr);
+
+	jsonw_end_object(wr);
+
+	jsonw_end_object(wr);
+	jsonw_destroy(&wr);
+	return 0;
+}
+
+#endif
diff --git a/json_writer.h b/json_writer.h
new file mode 100644
index 0000000..b52dc2d
--- /dev/null
+++ b/json_writer.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) */
+/*
+ * Simple streaming JSON writer
+ *
+ * This takes care of the annoying bits of JSON syntax like the commas
+ * after elements
+ *
+ * Authors:	Stephen Hemminger <stephen@...workplumber.org>
+ */
+
+#ifndef _JSON_WRITER_H_
+#define _JSON_WRITER_H_
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/* Opaque class structure */
+typedef struct json_writer json_writer_t;
+
+/* Create a new JSON stream */
+json_writer_t *jsonw_new(FILE *f);
+/* End output to JSON stream */
+void jsonw_destroy(json_writer_t **self_p);
+
+/* Cause output to have pretty whitespace */
+void jsonw_pretty(json_writer_t *self, bool on);
+
+/* Add property name */
+void jsonw_name(json_writer_t *self, const char *name);
+
+/* Add value  */
+__attribute__((format(printf, 2, 3)))
+void jsonw_printf(json_writer_t *self, const char *fmt, ...);
+void jsonw_string(json_writer_t *self, const char *value);
+void jsonw_bool(json_writer_t *self, bool value);
+void jsonw_float(json_writer_t *self, double number);
+void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num);
+void jsonw_uint(json_writer_t *self, unsigned int number);
+void jsonw_u64(json_writer_t *self, uint64_t number);
+void jsonw_xint(json_writer_t *self, uint64_t number);
+void jsonw_hhu(json_writer_t *self, unsigned char num);
+void jsonw_hu(json_writer_t *self, unsigned short number);
+void jsonw_int(json_writer_t *self, int number);
+void jsonw_s64(json_writer_t *self, int64_t number);
+void jsonw_null(json_writer_t *self);
+void jsonw_luint(json_writer_t *self, unsigned long num);
+void jsonw_lluint(json_writer_t *self, unsigned long long num);
+
+/* Useful Combinations of name and value */
+void jsonw_string_field(json_writer_t *self, const char *prop, const char *val);
+void jsonw_bool_field(json_writer_t *self, const char *prop, bool value);
+void jsonw_float_field(json_writer_t *self, const char *prop, double num);
+void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num);
+void jsonw_u64_field(json_writer_t *self, const char *prop, uint64_t num);
+void jsonw_xint_field(json_writer_t *self, const char *prop, uint64_t num);
+void jsonw_hhu_field(json_writer_t *self, const char *prop, unsigned char num);
+void jsonw_hu_field(json_writer_t *self, const char *prop, unsigned short num);
+void jsonw_int_field(json_writer_t *self, const char *prop, int num);
+void jsonw_s64_field(json_writer_t *self, const char *prop, int64_t num);
+void jsonw_null_field(json_writer_t *self, const char *prop);
+void jsonw_luint_field(json_writer_t *self, const char *prop,
+			unsigned long num);
+void jsonw_lluint_field(json_writer_t *self, const char *prop,
+			unsigned long long num);
+
+/* Collections */
+void jsonw_start_object(json_writer_t *self);
+void jsonw_end_object(json_writer_t *self);
+
+void jsonw_start_array(json_writer_t *self);
+void jsonw_end_array(json_writer_t *self);
+
+/* Override default exception handling */
+typedef void (jsonw_err_handler_fn)(const char *);
+
+#endif /* _JSON_WRITER_H_ */
-- 
2.26.2

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