[iproute2,json,v2,04/27] ip: ip_print: add new API to print JSON or regular format output

diff --git a/ip/Makefile b/ip/Makefile
index a754c04d..8ed2686c 100644
--- a/ip/Makefile
+++ b/ip/Makefile
@@ -9,7 +9,7 @@  IPOBJ=ip.o ipaddress.o ipaddrlabel.o iproute.o iprule.o ipnetns.o \
     link_iptnl.o link_gre6.o iplink_bond.o iplink_bond_slave.o iplink_hsr.o \
     iplink_bridge.o iplink_bridge_slave.o ipfou.o iplink_ipvlan.o \
     iplink_geneve.o iplink_vrf.o iproute_lwtunnel.o ipmacsec.o ipila.o \
-    ipvrf.o iplink_xstats.o ipseg6.o
+    ipvrf.o iplink_xstats.o ipseg6.o ip_print.o
 
 RTMONOBJ=rtmon.o
 
diff --git a/ip/ip_common.h b/ip/ip_common.h
index 77e9dd06..efc789cb 100644
--- a/ip/ip_common.h
+++ b/ip/ip_common.h
@@ -140,3 +140,59 @@  int name_is_vrf(const char *name);
 #endif
 
 void print_num(FILE *fp, unsigned int width, uint64_t count);
+
+#include "json_writer.h"
+
+json_writer_t   *get_json_writer(void);
+/*
+ * use:
+ *      - PRINT_ANY for context based output
+ *      - PRINT_FP for non json specific output
+ *      - PRINT_JSON for json specific output
+ */
+enum output_type {
+	PRINT_FP = 1,
+	PRINT_JSON = 2,
+	PRINT_ANY = 4,
+};
+
+void new_json_obj(int json, FILE *fp);
+void delete_json_obj(void);
+
+bool is_json_context(void);
+
+void set_current_fp(FILE *fp);
+
+void fflush_fp(void);
+
+void open_json_object(const char *str);
+void close_json_object(void);
+void open_json_array(enum output_type type, const char *delim);
+void close_json_array(enum output_type type, const char *delim);
+
+#include "color.h"
+
+#define _PRINT_FUNC(type_name, type)					\
+	void print_color_##type_name(enum output_type t,		\
+				     enum color_attr color,		\
+				     const char *key,			\
+				     const char *fmt,			\
+				     type value);			\
+									\
+	static inline void print_##type_name(enum output_type t,	\
+					     const char *key,		\
+					     const char *fmt,		\
+					     type value)		\
+	{								\
+		print_color_##type_name(t, -1, key, fmt, value);	\
+	}
+_PRINT_FUNC(int, int);
+_PRINT_FUNC(bool, bool);
+_PRINT_FUNC(null, const char*);
+_PRINT_FUNC(string, const char*);
+_PRINT_FUNC(uint, uint64_t);
+_PRINT_FUNC(hu, unsigned short);
+_PRINT_FUNC(hex, unsigned int);
+_PRINT_FUNC(0xhex, unsigned int);
+_PRINT_FUNC(lluint, unsigned long long int);
+#undef _PRINT_FUNC
diff --git a/ip/ip_print.c b/ip/ip_print.c
new file mode 100644
index 00000000..4cd6a0bc
--- /dev/null
+++ b/ip/ip_print.c
@@ -0,0 +1,233 @@ 
+/*
+ * ip_print.c          "ip print regular or json output".
+ *
+ *             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.
+ *
+ * Authors:    Julien Fortin, <julien@cumulusnetworks.com>
+ *
+ */
+
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "utils.h"
+#include "ip_common.h"
+#include "json_writer.h"
+
+static json_writer_t *_jw;
+static FILE *_fp;
+
+#define _IS_JSON_CONTEXT(type) ((type & PRINT_JSON || type & PRINT_ANY) && _jw)
+#define _IS_FP_CONTEXT(type) (!_jw && (type & PRINT_FP || type & PRINT_ANY))
+
+void new_json_obj(int json, FILE *fp)
+{
+	if (json) {
+		_jw = jsonw_new(fp);
+		if (!_jw) {
+			perror("json object");
+			exit(1);
+		}
+		jsonw_pretty(_jw, true);
+		jsonw_start_array(_jw);
+	}
+	set_current_fp(fp);
+}
+
+void delete_json_obj(void)
+{
+	if (_jw) {
+		jsonw_end_array(_jw);
+		jsonw_destroy(&_jw);
+	}
+}
+
+bool is_json_context(void)
+{
+	return _jw != NULL;
+}
+
+void set_current_fp(FILE *fp)
+{
+	if (!fp) {
+		fprintf(stderr, "Error: invalid file pointer.\n");
+		exit(1);
+	}
+	_fp = fp;
+}
+
+json_writer_t *get_json_writer(void)
+{
+	return _jw;
+}
+
+void open_json_object(const char *str)
+{
+	if (_IS_JSON_CONTEXT(PRINT_JSON)) {
+		if (str)
+			jsonw_name(_jw, str);
+		jsonw_start_object(_jw);
+	}
+}
+
+void close_json_object(void)
+{
+	if (_IS_JSON_CONTEXT(PRINT_JSON))
+		jsonw_end_object(_jw);
+}
+
+/*
+ * Start json array or string array using
+ * the provided string as json key (if not null)
+ * or as array delimiter in non-json context.
+ */
+void open_json_array(enum output_type type, const char *str)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		if (str)
+			jsonw_name(_jw, str);
+		jsonw_start_array(_jw);
+	} else if (_IS_FP_CONTEXT(type)) {
+		fprintf(_fp, "%s", str);
+	}
+}
+
+/*
+ * End json array or string array
+ */
+void close_json_array(enum output_type type, const char *str)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		jsonw_pretty(_jw, false);
+		jsonw_end_array(_jw);
+		jsonw_pretty(_jw, true);
+	} else if (_IS_FP_CONTEXT(type)) {
+		fprintf(_fp, "%s", str);
+	}
+}
+
+/*
+ * pre-processor directive to generate similar
+ * functions handling different types
+ */
+#define _PRINT_FUNC(type_name, type)					\
+	void print_color_##type_name(enum output_type t,		\
+				     enum color_attr color,		\
+				     const char *key,			\
+				     const char *fmt,			\
+				     type value)			\
+	{								\
+		if (_IS_JSON_CONTEXT(t)) {				\
+			if (!key)					\
+				jsonw_##type_name(_jw, value);		\
+			else						\
+				jsonw_##type_name##_field(_jw, key, value); \
+		} else if (_IS_FP_CONTEXT(t)) {				\
+			color_fprintf(_fp, color, fmt, value);          \
+		}							\
+	}
+_PRINT_FUNC(int, int);
+_PRINT_FUNC(hu, unsigned short);
+_PRINT_FUNC(uint, uint64_t);
+_PRINT_FUNC(lluint, unsigned long long int);
+#undef _PRINT_FUNC
+
+void print_color_string(enum output_type type,
+			enum color_attr color,
+			const char *key,
+			const char *fmt,
+			const char *value)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		if (key && !value)
+			jsonw_name(_jw, key);
+		else if (!key && value)
+			jsonw_string(_jw, value);
+		else
+			jsonw_string_field(_jw, key, value);
+	} else if (_IS_FP_CONTEXT(type)) {
+		color_fprintf(_fp, color, fmt, value);
+	}
+}
+
+/*
+ * value's type is bool. When using this function in FP context you can't pass
+ * a value to it, you will need to use "is_json_context()" to have different
+ * branch for json and regular output. grep -r "print_bool" for example
+ */
+void print_color_bool(enum output_type type,
+		      enum color_attr color,
+		      const char *key,
+		      const char *fmt,
+		      bool value)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		if (key)
+			jsonw_bool_field(_jw, key, value);
+		else
+			jsonw_bool(_jw, value);
+	} else if (_IS_FP_CONTEXT(type)) {
+		color_fprintf(_fp, color, fmt, value ? "true" : "false");
+	}
+}
+
+/*
+ * In JSON context uses hardcode %#x format: 42 -> 0x2a
+ */
+void print_color_0xhex(enum output_type type,
+		       enum color_attr color,
+		       const char *key,
+		       const char *fmt,
+		       unsigned int hex)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		SPRINT_BUF(b1);
+
+		snprintf(b1, sizeof(b1), "%#x", hex);
+		print_string(PRINT_JSON, key, NULL, b1);
+	} else if (_IS_FP_CONTEXT(type)) {
+		color_fprintf(_fp, color, fmt, hex);
+	}
+}
+
+void print_color_hex(enum output_type type,
+		     enum color_attr color,
+		     const char *key,
+		     const char *fmt,
+		     unsigned int hex)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		SPRINT_BUF(b1);
+
+		snprintf(b1, sizeof(b1), "%x", hex);
+		if (key)
+			jsonw_string_field(_jw, key, b1);
+		else
+			jsonw_string(_jw, b1);
+	} else if (_IS_FP_CONTEXT(type)) {
+		color_fprintf(_fp, color, fmt, hex);
+	}
+}
+
+/*
+ * In JSON context we don't use the argument "value" we simply call jsonw_null
+ * whereas FP context can use "value" to output anything
+ */
+void print_color_null(enum output_type type,
+		      enum color_attr color,
+		      const char *key,
+		      const char *fmt,
+		      const char *value)
+{
+	if (_IS_JSON_CONTEXT(type)) {
+		if (key)
+			jsonw_null_field(_jw, key);
+		else
+			jsonw_null(_jw);
+	} else if (_IS_FP_CONTEXT(type)) {
+		color_fprintf(_fp, color, fmt, value);
+	}
+}