Solve Exercise 7-2: Format arbitrary input

The solution is technically not 100% correct, but good luck figuring out
a robust solution inside Category-0 restrictions. Unicode characters
like ¬ or ♥ show up as 64-bit hex codes and I couldn't find a way to
shorten them. Then again, UTF-8 supports characters up to 8 bytes long.
Use it with plain ASCII and it looks only minorly off.

1 files changed, 101 insertions, 0 deletions

diff --git a/ch7/7-02_arb-input.c b/ch7/7-02_arb-input.c
new file mode 100644
index 0000000..2c8fbc9
--- /dev/null
+++ b/ch7/7-02_arb-input.c
@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <ctype.h>
+#include <string.h>
+
+/* The C Programming Language: 2nd Edition
+ *
+ * Exercise 7-2: Write a program that will print arbitrary input in a sensible
+ * way. As a minimum, it should print non-graphic characters in octal or
+ * hexadecimal according to local custom, and break long text lines.
+ *
+ * Notes: I spent some time thinking about this one. I'm somewhat picky in how
+ * I expect text to be handled, but the requirements are Spartan. Therefore, I
+ * will provide a Spartan solution. :)
+ *
+ * Linux printf formats don't seem to allow for truncation of hex or octal,
+ * so there wasn't an (easy, cat-zero friendly) way to work with the widths
+ * produced by the format strings. However, the program compiles, it has
+ * argument switches, it smartly breaks lines, and expands non-printable
+ * characters. It does exactly what it's supposed to. :)
+ */
+
+#define MAXLINELEN 81
+#define MAXBUF 102400
+
+#define HEX 16
+#define OCT 8
+
+int fmt;
+
+int mygetline(char s[], int max) {
+	int c, i;
+	i = 0;
+	while (max-- > 0 && (c = getchar()) != EOF && c != '\n') {
+		s[i++] = c;
+	}
+	if (c == '\n') {
+		s[i++] = c;
+	}
+	s[i] = '\0';
+	return i;
+}
+
+void fmt_print(char *s) {
+	int i = 0;
+	while (s[i] != '\0') {
+		if (isprint(s[i]) || s[i] == '\n') {
+			putchar(s[i]);
+		} else {
+			if (fmt == HEX) {
+				printf("%4X", s[i]);
+			} else {
+				printf("%3o", s[i]);
+			}
+		}
+		i++;
+	}
+}
+
+void break_lines(char *s) {
+	int fmt = HEX;
+	int c, nl, space;
+	for (c = 0, nl = 0, space = 0; s[c] != '\0'; c++) {
+		/* The position of the last space */
+		if (isspace(s[c])) {
+			space = c;
+		}
+		/* Position of the last new line */
+		if (s[c] == '\n') {
+			nl = c;
+		}
+		if (c == (nl + MAXLINELEN - 1)) {
+			if (space > nl) {
+				s[space] = '\n';
+				nl = space;
+			}
+		}
+	}
+}
+
+void parse_args(int argc, char *argv[]) {
+	int i;
+	while (argc > 1) {
+		--argc;
+		if (argv[argc][0] == '-') {
+			if (argv[argc][1] == 'o' && argv[argc][1] != '\0') {
+				fmt = OCT;
+			} else if (argv[argc][1] == 'h') {
+				fmt = HEX;
+			}
+		}
+	}
+}
+
+int main(int argc, char **argv) {
+	char buffer[MAXBUF];
+	parse_args(argc, argv);
+	while (mygetline(buffer, MAXBUF)) {
+		break_lines(buffer);
+		fmt_print(buffer);
+	}
+}