Re-solve Exercise 1-16: arbitrarily long maxline

A completely rewritten solution which follows the spec given in the book
exactly; make the program work for arbitrarily long input lines while
modifying `main()` only. I've only changed the name of the macro MAXLINE
to BUFFSIZE for clarity - otherwise the code is typed up exactly as
found in the book.

It demonstrates the use of a buffer without modifying any of the helper
functions.

1 files changed, 60 insertions, 44 deletions

diff --git a/ch1/1-16_longest-line.c b/ch1/1-16_longest-line.c
index 137bb11..450d990 100644
--- a/ch1/1-16_longest-line.c
+++ b/ch1/1-16_longest-line.c
@@ -9,55 +9,71 @@
  * Answer: The key to arbitrary limits is buffering. Using a buffer allows you
  * to tackle a problem in chunks of memory instead of all at once. It's
  * slightly more complicated, but adds usefulness to a program.
+ *
+ * This solution, which was contributed by Isa (ibnIrshad), follows the spec
+ * exactly, by only modifying main(), unlike many other solutions on the
+ * internet.
+ *
+ * Assumptions:
+ * 1. "arbitrarily long" is interpreted to mean upto the maximum size of an
+ * integer on the given architechture, e.g. 2^32 unsigned on a 32-bit machine.
+ * Indeed a string of that size would be larger than 4 gigabytes.
+ * It is possible to deal with numbers larger than that, but it involves a great
+ * deal of work abstracting away the concept of an integer, similar to
+ * dynamically sized arrays.
+ *
+ * 2. EOF signal (Ctrl-D) must be given on an empty line
  */
+#define BUFFSIZE 5 /* renamed MAXLINE and reduced it to 5 to demonstrate
+we can handle lines much greater than this number*/
+
+int getlinelen(char line[], int maxline);
+void copy(char to[], char from[]);
+
+/* print longest input line */
+main()
+{
+    /* len of current line, max len seen so far, templen of buffer */
+    int len, max, templen;
+    char buffer[BUFFSIZE];
 
-#define MAXLENGTH 100
-
-int get_line(char s[], int lim) {
-	/* Put as much as possible into a temp string, and count its length */
-	int c, i;
-
-	for (i = 0; i < lim && (c = getchar()) != EOF && c != '\n'; ++i) {
-		s[i] = c;
-	}
-	if (c == '\n') {
-		s[i] = c;
-		++i;
-	}
-	s[i] = '\0';
-	return i;
+    max = len = 0;
+
+    while ((templen = getlinelen(buffer, BUFFSIZE)) > 0) {
+        len += templen;
+
+        if (buffer[templen-1] == '\n'){
+            if (len > max)
+                max = len;
+            len = 0;
+        }
+    }
+    printf("\nLen of longest line: %d\n", max);
+    return 0;
 }
 
-void copy(char from[], char to[]) {
-	int i = 0;
+/* getlinelen: read a line into s, return length */
+int getlinelen(char s[], int lim)
+{
+    int c, i;
 
-	while ((to[i] = from[i]) != '\0') {
-		++i;
-	}
+    for (i=0; i<lim-1 && (c=getchar()) != EOF && c!='\n'; ++i)
+        s[i] = c;
+    if (c == '\n') {
+        s[i] = c;
+        ++i;
+    }
+    s[i] = '\0';
+    return i;
 }
 
-int main() {
-	int len, max;
-
-	char line[MAXLENGTH];
-	char longest[MAXLENGTH];
-
-	max = 0;
-	while ((len = get_line(line, MAXLENGTH)) > 0) {
-		if (len > max) {
-			max = len;
-			copy(line, longest);
-		}
-	}
-
-	printf("\nThe longest line is %3d characters long.\n", max);
-	printf("----------------------------------------\n");
-	if (max > 0) {
-		printf("%-s", longest);
-		if (max == MAXLENGTH && longest[max - 1] != '\n') {
-			printf("\n");
-		}
-	}
-
-	return 0;
+
+/* copy: copy 'from into 'to'; assume to is big enough */
+void copy(char to[], char from[])
+{
+    int i;
+
+    i = 0;
+    while ((to[i] = from[i]) != '\0')
+        ++i;
 }