Question

I have a couple of array’s:

const string a_strs[] = {'cr=1', 'ag=2', 'gnd=U', 'prl=12', 'av=123', 'sz=345', 'rc=6', 'pc=12345'}; const string b_strs[] = {'cr=2', 'sz=345', 'ag=10', 'gnd=M', 'prl=11', 'rc=6', 'cp=34', 'cv=54', 'av=654', 'ct=77', 'pc=12345'}; 

which i then need to parse out for ‘=’ and then put the values in the struct. (the rc key maps to the fc key in the struct), which is in the form of:

struct predict_cache_key {     pck() :         av_id(0),         sz_id(0),         cr_id(0),         cp_id(0),         cv_id(0),         ct_id(0),         fc(0),         gnd(0),         ag(0),         pc(0),         prl_id(0)     { }      int av_id;     int sz_id;     int cr_id;     int cp_id;      int cv_id;     int ct_id;     int fc;     char gnd;     int ag;     int pc;     long prl_id; }; 

The problem I am encountering is that the array’s are not in sequence or in the same sequence as the struct fields. So, I need to check each and then come up with a scheme to put the same into the struct.

Any help in using C or C++ to solve the above?

Answer 1

This shouldn’t be too hard. Your first problem is that you don’t have a fixed sized array, so you’d have to pass the size of the array, or what I’d prefer you make the arrays NULL-terminated, e.g.

const string a_strs[] = {'cr=1', 'ag=2', 'gnd=U', NULL};

Then I would write a (private) helper function that parse the string:

 bool parse_string(const string &str, char *buffer, size_t b_size, int *num) {     char *ptr;      strncpy(buffer, str.c_str(), b_size);     buffer[b_size - 1] = 0;      /* find the '=' */     ptr = strchr(buffer, '=');      if (!ptr) return false;      *ptr = '\0';     ptr++;      *num = atoi(ptr);      return true; } 

then you can do what qrdl has suggested.

in a simple for loop:

 for (const string *cur_str = array; *cur_str; cur_str++) {    char key[128];    int value = 0;     if (!parse_string(*cur_string, key, sizeof(key), &value)        continue;     /* and here what qrdl suggested */    if (!strcmp(key, 'cr')) cr_id = value;    else if ... } 

EDIT: you should probably use long instead of int and atol instead of atoi, because your prl_id is of the type long. Second if there could be wrong formated numbers after the ‘=’, you should use strtol, which can catch errors.