How can I do it smarter? - c

Question

I must read and extract some values from string.
These values are coded like this:
k="11,3,1" v="140.3"
I have defined the codes and created struct with all field as well as a temp one where I store k and v. In fillFields proc I transfer values from temp struct to the right one (with the valid types).
It works but I have many fields and fillFields would need to have many if-conditions. Maybe someone could give me any hint how to write it smarter.
The simplified code now:
#define ASK "11,3,1"
#define BID "11,2,1"
#define CLOSE "3,1,1"
typedef struct tic {
float ask;
float bid;
float close;
}tic, *ticP;
typedef struct pElem {
char * k;
char * v;
}pElem, *pElemP;
void fillFields(ticP t, pElemP p)
{
if (strcmp( ASK, p->k)==0)
{
printf ("ASK %s\n", p->v);
t->ask = atof(p->v);
}
if (strcmp( BID, p->k)==0)
{
printf ("BID %s\n", p->v);
t->bid = atof(p->v);
}
if (strcmp( CLOSE, p->k)==0)
{
printf("CLOSE >>>%s<<<\n", p->v) ;
t->close = atof (p->v);
}
}

Answer 1

Rather than save the text value in pElem, save the converted values.
This creates an extra step in parsing k="11,3,1" v="140.3", to convert text to an enumerated type, but it's paid once. The fillFields() calls then run simpler. Assuming you have more ticP variables, it's a win.
typedef enum pElem_type {
pElem_None, pElem_ASK, pElem_BID, pElem_CLOSE, pElem_N
} pElem_type;
typedef struct pElem {
pElem_type type;
float value;
} pElem;
void fillFields(ticP t, const pElem *p) {
switch (p->type) {
case pElem_ASK:
printf("ASK %f\n", p->value);
t->ask = p->value;
break;
case pElem_BID:
printf("BID %f\n", p->value);
t->bid = p->value;
break;
case pElem_CLOSE:
printf("Close %f\n", p->value);
t->close = p->value;
break;
default:
printf("Error\n");
}
}
// Further simplifications possible
typedef struct tic {
float field[pElem_N];
}tic, *ticP;
static const char *FieldName[pElem_N] = {
"None", "ASK", "BID", "Close"
};
void fillFields(ticP t, const pElem *p) {
if (p->type < pElem_N) {
printf("%s %f\n", FieldName[p->type], p->value);
t->field[p->type] = p->value;
}
}