lib/jsonwrt: add new functions to write in JSON

We need JSON formatting stuff also outside libsmartcols.

Signed-off-by: Karel Zak <kzak@redhat.com>

include/Makemodule.am

@@ -26,6 +26,7 @@ dist_noinst_HEADERS += \
 	include/idcache.h \
 	include/ismounted.h \
 	include/iso9660.h \
+	include/jsonwrt.h \
 	include/pwdutils.h \
 	include/linux_version.h \
 	include/list.h \

include/jsonwrt.h

@@ -0,0 +1,44 @@
+#ifndef UTIL_LINUX_JSONWRT_H
+#define UTIL_LINUX_JSONWRT_H
+
+enum {
+	UL_JSON_OBJECT,
+	UL_JSON_ARRAY,
+	UL_JSON_VALUE
+};
+
+struct ul_jsonwrt {
+	FILE *out;
+	int indent;
+
+	unsigned int postponed_break :1;
+};
+
+void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent);
+void ul_jsonwrt_indent(struct ul_jsonwrt *fmt);
+void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type);
+void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type, int islast);
+
+#define ul_jsonwrt_root_open(_f)	ul_jsonwrt_open(_f, NULL, UL_JSON_OBJECT)
+#define ul_jsonwrt_root_close(_f)	ul_jsonwrt_close(_f, UL_JSON_OBJECT, 1)
+
+#define ul_jsonwrt_array_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_ARRAY)
+#define ul_jsonwrt_array_close(_f, _l)	ul_jsonwrt_close(_f, UL_JSON_ARRAY, _l)
+
+#define ul_jsonwrt_object_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_OBJECT)
+#define ul_jsonwrt_object_close(_f, _l)	ul_jsonwrt_close(_f, UL_JSON_OBJECT, _l)
+
+#define ul_jsonwrt_value_open(_f, _n)	ul_jsonwrt_open(_f, _n, UL_JSON_VALUE)
+#define ul_jsonwrt_value_close(_f, _l)	ul_jsonwrt_close(_f, UL_JSON_VALUE, _l)
+
+
+void ul_jsonwrt_value_raw(struct ul_jsonwrt *fmt,
+			const char *name, const char *data, int islast);
+void ul_jsonwrt_value_s(struct ul_jsonwrt *fmt,
+			const char *name, const char *data, int islast);
+void ul_jsonwrt_value_u64(struct ul_jsonwrt *fmt,
+			const char *name, uint64_t data, int islast);
+void ul_jsonwrt_value_boolean(struct ul_jsonwrt *fmt,
+			const char *name, int data, int islast);
+
+#endif /* UTIL_LINUX_JSONWRT_H */

lib/Makemodule.am

@@ -22,6 +22,7 @@ libcommon_la_SOURCES = \
 	lib/encode.c \
 	lib/fileutils.c \
 	lib/color-names.c \
+	lib/jsonwrt.c \
 	lib/mangle.c \
 	lib/match.c \
 	lib/mbsalign.c \

lib/jsonwrt.c

@@ -0,0 +1,128 @@
+/*
+ * JSON output formatting functions.
+ *
+ * No copyright is claimed.  This code is in the public domain; do with
+ * it what you wish.
+ *
+ * Written by Karel Zak <kzak@redhat.com>
+ */
+#include <stdio.h>
+#include <inttypes.h>
+
+#include "c.h"
+#include "carefulputc.h"
+#include "jsonwrt.h"
+
+
+void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent)
+{
+	fmt->out = out;
+	fmt->indent = indent;
+}
+
+void ul_jsonwrt_indent(struct ul_jsonwrt *fmt)
+{
+	int i;
+
+	for (i = 0; i < fmt->indent; i++)
+		fputs("   ", fmt->out);
+}
+
+void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
+{
+	if (fmt->postponed_break && !name)
+		;
+	else {
+		ul_jsonwrt_indent(fmt);
+		if (name)
+			fputs_quoted(name, fmt->out);
+	}
+
+	switch (type) {
+	case UL_JSON_OBJECT:
+		fputs(name ? ": {\n" : "{\n", fmt->out);
+		fmt->indent++;
+		break;
+	case UL_JSON_ARRAY:
+		fputs(name ? ": [\n" : "{\n", fmt->out);
+		fmt->indent++;
+		break;
+	case UL_JSON_VALUE:
+		fputs(name ? ": " : " ", fmt->out);
+		break;
+	}
+	fmt->postponed_break = 0;
+}
+
+void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type, int islast)
+{
+	if (fmt->indent == 0) {
+		fputs("}\n", fmt->out);
+		fmt->indent--;
+		return;
+	}
+	assert(fmt->indent > 0);
+
+	switch (type) {
+	case UL_JSON_OBJECT:
+		fmt->indent--;
+		ul_jsonwrt_indent(fmt);
+		fputs(islast ? "}" : "},", fmt->out);
+		break;
+	case UL_JSON_ARRAY:
+		fmt->indent--;
+		ul_jsonwrt_indent(fmt);
+		fputs(islast ? "]" : "],", fmt->out);
+		break;
+	case UL_JSON_VALUE:
+		if (!islast)
+			fputc(',', fmt->out);
+		break;
+	}
+
+	if (!islast && (type == UL_JSON_OBJECT || type == UL_JSON_ARRAY))
+		fmt->postponed_break = 1;
+	else {
+		fputc('\n', fmt->out);
+		fmt->postponed_break = 0;
+	}
+}
+
+void ul_jsonwrt_value_raw(struct ul_jsonwrt *fmt,
+			const char *name, const char *data, int islast)
+{
+	ul_jsonwrt_value_open(fmt, name);
+	if (data && *data)
+		fputs(data, fmt->out);
+	else
+		fputs("null", fmt->out);
+	ul_jsonwrt_value_close(fmt, islast);
+}
+
+void ul_jsonwrt_value_s(struct ul_jsonwrt *fmt,
+			const char *name, const char *data, int islast)
+{
+	ul_jsonwrt_value_open(fmt, name);
+	if (data && *data)
+		fputs_quoted(data, fmt->out);
+	else
+		fputs("null", fmt->out);
+	ul_jsonwrt_value_close(fmt, islast);
+}
+
+void ul_jsonwrt_value_u64(struct ul_jsonwrt *fmt,
+			const char *name, uint64_t data, int islast)
+{
+	ul_jsonwrt_value_open(fmt, name);
+	fprintf(fmt->out, "%"PRIu64, data);
+	ul_jsonwrt_value_close(fmt, islast);
+}
+
+void ul_jsonwrt_value_boolean(struct ul_jsonwrt *fmt,
+			const char *name, int data, int islast)
+{
+	ul_jsonwrt_value_open(fmt, name);
+	fputs(data ? "true" : "false", fmt->out);
+	ul_jsonwrt_value_close(fmt, islast);
+}
+