Removed unnecessary variable from readlines, fixed bug where

EOF terminated line was skipped

k&r/05-pointers-and-arrays/05-07-sort.c

@@ -1,9 +1,10 @@
 #include <stdio.h>
 #include <ctype.h>
+#include <assert.h>
 
 /* array bounds */
 #define MAXLINES 100 
-#define BUFF_SIZE (80 * 100)
+#define BUFF_SIZE (80 * MAXLINES) 
 
 int readlines(char *lines[], int maxlines, char *ln_buff, size_t lb_size);
 void writelines(char *lines[], int n);
@@ -16,16 +17,15 @@ int main()
     char buffer[BUFF_SIZE];
     
     int line_count = readlines(lines, MAXLINES, buffer, BUFF_SIZE);
-    if (line_count >= 0) {
+    if (line_count < 0) {
+        line_count = -line_count - 1;
+        printf("warning: buffer overflow occured, read %d lines\n", line_count);
+    } else if (line_count > MAXLINES) {
+        line_count = MAXLINES;
+        printf("warning: too many lines, read %d lines\n", line_count);
+    }
     qsort_string(lines, 0, line_count-1);
     writelines(lines, line_count);
-    } else if (line_count == -1) {
-        puts("error: lines overflow");
-        return 1;
-    } else if (line_count == -2) {
-        puts("error: buffer overflow");
-        return 2;
-    }
     return 0;
 }
 
@@ -39,40 +39,40 @@ void writelines(char *lines[], int n)
 }
 
 /* readlines: reads lines from input, writing them to ln_buff
- * and line pointers to lines. returns number of lines read,
+ * and line pointers to lines. 
- * -1 on lines overflow
+ * returns number of lines read,
- *  -2 on buffer overflow */
+ * -lines_read-1 < 0 on buffer overflow
+ * maxlines+1 on lines overflow */
 int readlines(char *lines[], int maxlines, char *buffer, size_t buff_size)
 {
+    assert(maxlines > 0);
     char ** const fst_line = lines;
-    char *ln_start = buffer;
     int c, not_empty = 0;
 
-    for (; (c = getchar()) != EOF && buff_size; --buff_size) {
+    for (*lines = buffer; (c = getchar()) != EOF && buff_size; --buff_size) {
         not_empty |= !isspace(c);
         if (c == '\n') {
             if (!not_empty) { /* skip empty lines */
-                buff_size += buffer - ln_start;
+                buff_size += buffer - *lines;
-                buffer = ln_start;
+                buffer = *lines;
                 continue;
             }
+            not_empty = 0;
             *buffer++ = '\0';
-            *lines++ = ln_start;
             if (!--maxlines)
                 break;
-            not_empty = 0;
+            *++lines = buffer;
-            ln_start = buffer;
         } else
             *buffer++ = c; 
     }
-    /* ignore trailing whitespace and emepty lines */
+    /* ignore trailing whitespace and empty lines */
     while (c != EOF && isspace(c))
             c = getchar();
-    if (!maxlines && c != EOF) /* lines overflow */
+    if (c != EOF && !buff_size) /* buffer overflow, return -lines_read-1 */
-        return -1;
+        return fst_line - lines - 1;
-    if (!buff_size && c != EOF) /* buffer overflow */
+    if (c != EOF && !maxlines) /* lines overflow, return maxlines+1 */
-        return -2;
+        return lines - fst_line + 2;
-    return lines - fst_line;
+    return lines - fst_line + not_empty;
 }
 
 /* ---------- string quicksort */