json_decimate.c

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#include <options/options.h>
#include "../csm/csm_all.h"

int main(int argc, const char * argv[]) {
        sm_set_program_name(argv[0]);
        
    int period; int phase;
        const char*input_filename;
        const char*output_filename;
        
        struct option* ops = options_allocate(3);
        options_int(ops, "period", &period, 1, "Period of objects to extract.");
        options_int(ops, "phase", &phase, 0, "Phase (=0 starts with the first object)");
        options_string(ops, "in", &input_filename, "stdin", "input file (JSON)");
        options_string(ops, "out", &output_filename, "stdout", "output file (JSON)");
        
        if(!options_parse_args(ops, argc, argv)) {
                fprintf(stderr, "%s : decimates a JSON stream."
                        "\n\nOptions:\n", argv[0]);
                options_print_help(ops, stderr);
                return -1;
        }
        
        if(period < 1) {
                sm_error("Period must be >= 1.\n");
                return 2;
        }
        
        FILE * input_stream = open_file_for_reading(input_filename);
        FILE *output_stream = open_file_for_writing(output_filename);
        
        if(!input_stream || !output_stream) return -1;
        
        
        int count = 0;
        while(1) { 
                JO jo = json_read_stream(input_stream);
                if(!jo) {
                        if(feof(input_stream)) break;
                        sm_error("Malformed JSON\n");
                        return -1;
                }
                
                if( (count - phase) % period == 0) {
                        const char * s = json_object_to_json_string(jo);
                        fputs(s,output_stream); fputs("\n",output_stream);
                } 
                
                jo_free(jo);
                count++;
        }
        
        return 0;
}