JSON parser written in C

使用json-c來parse json
Install:

1.  libtool, autoconf, automake, doxygen
2. sudo apt-get install libtool
3. sudo apt-get install autoconf

Build:

1.  git clone https://github.com/json-c/json-c.git
2.  cd json-c
3.  ./autogen.sh
4.  ./configure
5.  make
6.  make install
7.  make check
8.  在 /usr/local/lib/ 會看到 libjson-c.so.4.0.0 以及連結檔

Use - parser: (比較常用的)

1. json_object_object_foreach
2. json_object_get_type
3. json_tokener_parse
4. json_object_get_string
5. json_object_object_get_ex
6. json_object_object_get (gcc:不建議使用)
7. json_object_put  //free
   
   example

Compiler:

1. LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
2. export LD_LIBRARY_PATH
3. gcc  xx.c -o xx -ljson-c

example:

#include <json-c/json.h>
#include <stdio.h>
#include <unistd.h>
#include <mcheck.h>

int main()
{
    //check memory leek
    setenv("MALLOC_TRACE", "output_file_name", 1);
    mtrace();

    struct json_object *Object =     json_object_new_object();
    struct json_object *CpObject =   json_object_new_object();
    struct json_object *CpArray =    json_object_new_array();
    json_object_object_add(Object, "Time",      json_object_new_string("yyyy_mm_dd"));
    json_object_object_add(Object, "Name",      json_object_new_string("123"));
    json_object_object_add(Object, "Action",    json_object_new_string("456"));

    json_object_object_add(CpObject, "Code", json_object_new_string("11"));
    json_object_object_add(CpObject, "Type",     json_object_new_string("22"));
    json_object_object_add(CpObject, "SubType",  json_object_new_string("33"));
    json_object_array_add(CpArray, CpObject);

    json_object_object_add(Object, "CpCommands", CpArray);

    printf ("%s\n",json_object_to_json_string(Object));

    //free memory
    json_object_put(Object);
    json_object_put(CpObject);
}

example:
text.txt

{ "district" : "hello" }

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <mcheck.h>
#include <json-c/json.h>

#define READ_FILE_BUF 256
#define ONE_LOAD 16
#define READ_FILE_PATH "test.txt"

int test(char *dist)
{
    FILE *fp=NULL;
    char buf[READ_FILE_BUF]={0};
    char str[ONE_LOAD];
    char *tname="district"; //target_name
    const char *gstr=NULL; //get string
    if ((fp = fopen (READ_FILE_PATH, "r")) == NULL)
    {
        fprintf(stderr, "Can't open file\n");
    }
    while(!feof(fp) && !ferror(fp))
    {
        if(strlen(buf)>READ_FILE_BUF-ONE_LOAD)
        {
            fprintf(stdout,"buf oversize\n");
            goto end;
        }
        if(fgets(str,16,fp)!=NULL)
        {
            str[strlen(str)-1]=0x20;
            strncat(buf, str, ONE_LOAD);
            fprintf(stdout, "buf=%s\n",buf);
        }
    }
    json_object *jobj = json_tokener_parse(buf);
    if(!jobj)
        goto end;

    json_object *val_obj = NULL;
    if(json_object_object_get_ex(jobj, tname, &val_obj))
    {
        gstr = json_object_get_string(val_obj);
        fprintf(stdout, "%s, %s: %s\n", __FUNCTION__, tname, gstr);
        if(gstr==NULL)
        {
            fprintf(stderr, "Can't find target keyname in the file\n");
            return 1;
        }
        else
        {
            strcpy(dist, gstr);
        }
    }
    json_object_put(jobj);
    fprintf(stdout, "dist=%s\n", dist);
    fclose(fp);
    return 0;
end:
    json_object_put(jobj);
    fclose(fp);
}

int main()
{
    char dist[16];
    test(dist);
    return 0;
}