From 8d64674314e55a1c2fa044cf9552886a4e852ec9 Mon Sep 17 00:00:00 2001
From: zlg <zlg@zlg.space>
Date: Sun, 13 Oct 2013 03:24:07 -0500
Subject: Solve Exercise 5-12: flexible `detab` and `entab`

---
 ch5/5-12_detab-spec.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 ch5/5-12_detab-spec.c

(limited to 'ch5/5-12_detab-spec.c')

diff --git a/ch5/5-12_detab-spec.c b/ch5/5-12_detab-spec.c
new file mode 100644
index 0000000..ba22619
--- /dev/null
+++ b/ch5/5-12_detab-spec.c
@@ -0,0 +1,75 @@
+#include <stdio.h>
+#include <ctype.h>
+
+/* The C Programming Language: 2nd Edition
+ *
+ * Exercise 5-12: Extend `entab` and `detab` to accept the shorthand
+ * `entab -m +n` to mean tab stops every n columns, starting at column m.
+ * Choose convenient (for the user) default behavior.
+ */
+
+#define DEFAULTTAB 8
+
+int main(int argc, char *argv[]) {
+	int column, c;
+	int tabstart = (-1);
+	int tabevery = (-1);
+	char arg[4];
+	column = 0;
+
+	if (argc > 1) {
+		int i = 1;
+		int j = 0;
+		while (--argc > 0) {
+			c = argv[i][j++];
+			if (c == '-' || c == '+') {
+				while (isdigit(argv[i][j])) {
+					arg[j - 1] = argv[i][j];
+					j++;
+				}
+				arg[3] = '\0';
+				if (c == '-') {
+					tabstart = atoi(arg);
+				} else {
+					tabevery = atoi(arg);
+				}
+				j = 0;
+			} else {
+				printf("detab: unrecognized argument %s\n", *argv);
+			}
+			i++;
+		}
+	}
+	/* Clean up the mess if either argument hasn't been set to something sane */
+	if (tabstart == -1) {
+		tabstart = 0;
+	}
+	if (tabevery == -1) {
+		tabevery = DEFAULTTAB;
+	}
+
+	while ((c = getchar()) != EOF) {
+		column++;
+
+		if (c == '\t') {
+			/* No point in processing our tabs until we're after the offset */
+			if (column > tabstart) {
+				putchar(' ');
+				while ((column - tabstart) % tabevery != 0) {
+					putchar(' ');
+					column++;
+				}
+			} else {
+				putchar(' ');
+			}
+		} else {
+			/* reset the counts on a newline */
+			if (c == '\n') {
+				column = 0;
+			}
+			putchar(c);
+		}
+	}
+	
+	return 0;
+}
-- 
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