Add JSON support to v.info module

Use parson to add json output format support to the v.info module. The module has
various flags to control the fields being output in case of plain format. The current
prototype ignores the flags and always outputs all data for the JSON output.

vector/v.info/Makefile

@@ -3,7 +3,7 @@ MODULE_TOPDIR = ../..
 
 PGM = v.info
 
-LIBES = $(VECTORLIB) $(DIG2LIB) $(DBMILIB) $(GISLIB)
+LIBES = $(VECTORLIB) $(DIG2LIB) $(DBMILIB) $(GISLIB) $(PARSONLIB)
 DEPENDENCIES = $(VECTORDEP) $(DIG2DEP) $(DBMIDEP) $(GISDEP)
 EXTRA_INC = $(VECT_INC)
 EXTRA_CFLAGS = $(VECT_CFLAGS)

vector/v.info/local_proto.h

@@ -1,20 +1,23 @@
 #include <grass/vector.h>
+#include <grass/parson.h>
 
 #define SHELL_NO     0x00
 #define SHELL_BASIC  0x02
 #define SHELL_REGION 0x04
 #define SHELL_TOPO   0x08
 
+enum OutputFormat { PLAIN, JSON };
+
 /* level1.c */
 int level_one_info(struct Map_info *);
 
 /* parse.c */
-void parse_args(int, char **, char **, char **, int *, int *, int *);
+void parse_args(int, char **, char **, char **, int *, int *, int *, enum OutputFormat *);
 
 /* print.c */
 void format_double(double, char *);
-void print_region(struct Map_info *);
-void print_topo(struct Map_info *);
+void print_region(struct Map_info *, enum OutputFormat, JSON_Object *);
+void print_topo(struct Map_info *, enum OutputFormat, JSON_Object *);
 void print_columns(struct Map_info *, const char *, const char *);
 void print_info(struct Map_info *);
-void print_shell(struct Map_info *, const char *);
+void print_shell(struct Map_info *, const char *, enum OutputFormat, JSON_Object *);

vector/v.info/main.c

@@ -29,6 +29,11 @@ int main(int argc, char *argv[])
     char *input_opt, *field_opt;
     int hist_flag, col_flag, shell_flag;
 
+    enum OutputFormat format;
+
+    JSON_Value *root_value;
+    JSON_Object *root_object;
+
     struct Map_info Map;
 
     G_gisinit(argv[0]);
@@ -47,7 +52,13 @@ int main(int argc, char *argv[])
     G_debug(1, "LFS is %s", sizeof(off_t) == 8 ? "available" : "not available");
 
     parse_args(argc, argv, &input_opt, &field_opt, &hist_flag, &col_flag,
-               &shell_flag);
+               &shell_flag, &format);
+
+    if (format == JSON) {
+        root_value = json_value_init_object();
+        root_object = json_value_get_object(root_value);
+        json_set_float_serialization_format("%lf");
+    }
 
     /* try to open head-only on level 2 */
     if (Vect_open_old_head2(&Map, input_opt, "", field_opt) < 2) {
@@ -82,19 +93,30 @@ int main(int argc, char *argv[])
         return (EXIT_SUCCESS);
     }
 
-    if (shell_flag & SHELL_BASIC) {
-        print_shell(&Map, field_opt);
+    if ((shell_flag & SHELL_BASIC) || format == JSON) {
+        print_shell(&Map, field_opt, format, root_object);
     }
-    if (shell_flag & SHELL_REGION) {
-        print_region(&Map);
+    if ((shell_flag & SHELL_REGION) || format == JSON) {
+        print_region(&Map, format, root_object);
     }
-    if (shell_flag & SHELL_TOPO) {
-        print_topo(&Map);
+    if ((shell_flag & SHELL_TOPO) || format == JSON) {
+        print_topo(&Map, format, root_object);
     }
-    if (shell_flag == 0) {
+    if (shell_flag == 0 && format == PLAIN) {
         print_info(&Map);
     }
 
+    if (format == JSON) {
+        char *serialized_string = NULL;
+        serialized_string = json_serialize_to_string_pretty(root_value);
+        if (serialized_string == NULL) {
+            G_fatal_error(_("Failed to initialize pretty JSON string."));
+        }
+        puts(serialized_string);
+        json_free_serialized_string(serialized_string);
+        json_value_free(root_value);
+    }
+
     Vect_close(&Map);
 
     return (EXIT_SUCCESS);

vector/v.info/parse.c

@@ -6,9 +6,9 @@
 #include "local_proto.h"
 
 void parse_args(int argc, char **argv, char **input, char **field, int *history,
-                int *columns, int *shell)
+                int *columns, int *shell, enum OutputFormat *format_ptr)
 {
-    struct Option *input_opt, *field_opt;
+    struct Option *input_opt, *field_opt, *format_opt;
     struct Flag *hist_flag, *col_flag, *shell_flag, *region_flag, *topo_flag;
 
     input_opt = G_define_standard_option(G_OPT_V_MAP);
@@ -42,6 +42,9 @@ void parse_args(int argc, char **argv, char **input, char **field, int *history,
     topo_flag->description = _("Print topology info in shell script style");
     topo_flag->guisection = _("Print");
 
+    format_opt = G_define_standard_option(G_OPT_F_FORMAT);
+    format_opt->guisection = _("Print");
+
     if (G_parser(argc, argv))
         exit(EXIT_FAILURE);
 
@@ -56,4 +59,9 @@ void parse_args(int argc, char **argv, char **input, char **field, int *history,
         *shell |= SHELL_REGION;
     if (topo_flag->answer)
         *shell |= SHELL_TOPO;
+
+    if (strcmp(format_opt->answer, "json") == 0)
+        *format_ptr = JSON;
+    else
+        *format_ptr = PLAIN;
 }