How add CHAR(") to string using c or python? - json

Question

Now I have a LIKE JSON(NOT JSON) string which saved file:
{"content":["info":{"tid":(uint)123,"pid":(int)456}],"header":{"test":"hello"}}
For compare two this string with python json, I need to format this string, because it decoded wrong using python json, it can run right if (unit)123 were "(uint)123". Now I have written code using c, the bellow:
void dofile(char *filename)
{
FILE *f;
long len;
char *data;
char *head;
char *ptr;
char *value;
f=fopen(filename,"rb");
fseek(f,0,SEEK_END);
len=ftell(f);
fseek(f,0,SEEK_SET);
data=(char*)malloc(len+1);
fread(data,1,len,f);
data[len]='\0';
fclose(f);
head = data;
ptr = data;
while (*ptr)
{
if (*ptr++ == '\\')
continue;
int l = 1;
if (*ptr=='\"' && *++ptr==':' && *++ptr=='(')
{
value = ptr;
while (*ptr++ != ')' && *ptr && ++l)
;
ptr++;
len++;
if (*ptr == '-')
{
ptr++;
l++;
}
while(*ptr >= '0' && *ptr <= '9' && *ptr && ++l)
{
ptr++;
}
char *tmp = (char*)malloc(len+2);
memcpy(tmp, head, value-head);
memset(tmp+(value-head), '\"', 1);
memcpy(tmp+(value-head)+1, value, ptr-value);
memset(tmp+(ptr-head)+1, '\"', 1);
memcpy(tmp+(ptr-head)+2, ptr, len-(ptr-head));
len += 2;
ptr = tmp + (ptr-head)+2;
free(data);
data = tmp;
head = data;
}
}
f = fopen(filename, "wb");
fwrite(data, len-1, 1, f);
fclose(f);
printf("%s\n", data);
free(data);
}
OK, it is OK, but has it problem? Because I think that I use many mem function.