Thread: Split a Byte Array

man page strtod section 3
man page strtol section 3
Will naturally stop at any delimiter, and also update a pointer to where it stopped converting the string.

This makes it very easy to walk the length of a string without any prior need to tokenise the string.

If you don't know the order of the data, you can't use sscanf or Salem's method.

I thought this would be a good way to get my brain working this morning, so I wrote a little "state machine" parser. It might seem like overkill or it might be something with some potential depending on the details of the task.

Code:

#include <stdio.h>
#include <stdlib.h>

enum {
	ERR,
	INT,
	FLOAT
};

typedef struct {
	union {
		int i;
		float f;
	} value;
	int type;
} Number;

#define MAX 8

void getValue (char *raw, int type, Number *data) {
	if (type == INT) data->value.i = atoi(raw);
	else if (type == FLOAT) data->value.f = strtof(raw, NULL);
	data->type = type;
}

int main(void) {
	char in[] = "178.50|125|1070", *p = in, *cur = NULL;
	int state = INT, count = 0, i;
	Number data[MAX];

	while (*p && count < MAX) {
		if (*p == '|') {
			*p = '\0';
			if (cur) {
				getValue (cur, state, &data[count++]);
				cur = NULL;
				state = INT;
			}
		} else if (*p == '.') {
			if (state == FLOAT || state == ERR) state = ERR;
			else state = FLOAT;
		} else if (*p >= '0' && *p <= '9') {
			if (!cur) cur = p;
		} else state = ERR;
		p++;
	}
	if (cur  && count < MAX) getValue (cur, state, &data[count++]);

// output
	for (i = 0; i < count; i++) {
		switch (data[i].type) {
			case ERR:
				printf("Bad value in packet!\n");
				break;
			case INT:
				printf("Integer: %d\n", data[i].value.i);
				break;
			case FLOAT:
				printf("Float: %f\n", data[i].value.f);
				break;
			default: 
				printf("WTF?\n");
		}
	}

	return 0;
}