Solve Exercise 7-4: minscanf()

This one wasn't too bad, either! There's a minor bug in the code, but
I'm not sure how to fix it. It *technically* meets muster, though. :P

1 files changed, 70 insertions, 0 deletions

diff --git a/ch7/7-04_minscanf.c b/ch7/7-04_minscanf.c
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+++ b/ch7/7-04_minscanf.c
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+#include <stdio.h>
+#include <stdarg.h>
+
+/* The C Programming Language, 2nd Edition
+ *
+ * Exercise 7-4: Write a private version of `scanf` analagous to minprintf
+ * from the previous section.
+ *
+ * Notes: Again, it doesn't specify which facilities, so we'll choose a few
+ * of the more important ones:
+ *
+ *     d - decimal number
+ *     s - string
+ *     f - floating point number
+ *
+ * Then pass things off to scanf().
+ */
+
+void minscanf(char *fmt, ...) {
+	va_list ap;
+	char *p, *sval, *rval;
+	int *ival;
+	float *fval;
+	va_start(ap, fmt);
+	for (p = fmt; *p; p++) {
+		if (*p != '%') {
+			putchar(*p);
+			continue;
+		}
+		switch (*++p) {
+			case 'd':
+				ival = va_arg(ap, int *);
+				scanf("%d", ival);
+				break;
+			case 'f':
+				fval = va_arg(ap, float *);
+				scanf("%f", fval);
+				break;
+			case 's':
+				sval = va_arg(ap, char *);
+				scanf("%s", sval);
+				break;
+			default:
+				putchar(*p);
+				break;
+		}
+	}
+	va_end(ap);
+}
+
+int main(int argc, char *argv[]) {
+	printf("Enter a floating point number: ");
+	float foo;
+	minscanf("%f", &foo);
+	printf("We got a %f...\n", foo);
+	printf("Okay, and a regular number: ");
+	int bar;
+	minscanf("%d", &bar);
+	printf("And you gave me %d\n...", bar);
+	/* Interestingly, if your integer has a floating-point portion,
+	 * it becomes the first string of minscanf()'s next call.
+	 * This is peculiar and I'm not sure how to fix it.
+	 */
+	printf("Lastly, your first and last name, please: ");
+	char baz[80];
+	char biz[80];
+	minscanf("%s %s", &baz, &biz);
+	printf("Nice to meetcha, %s %s!\n", &*baz, &*biz);
+	return 0;
+}