rewrote part of program for lower complexity

k&r/04-funcs-and-prog-struct/04-find/04-find-no-overflow.c

@@ -1,69 +1,48 @@
 #include <stdio.h>
 #include <string.h>
-#include <math.h>
 #include <assert.h>
 
-void println(void);
 int flush_lnbuff(void);
 int getch_lnbuff(void);
-
+void ignoreln_lnbuff(void);
 
 /* find: prints lines containing pattern, returns number of matching lines
- * gracefully handle line overflow */
+ * gracefully handle line overflow 
+ * compile with -O3 */
 int find(char *pattern, char lineno_flag, char except_flag)
 {
-    int found, i, c;
-    const int plen = strlen(pattern);
-    long lineno = 1;
-    i = found = 0;
-    char match = 0;
 
-#define print_lineno() if (lineno_flag) printf("%ld:", lineno)
+    extern long lineno;
+    int i, c, found;
+    const int plen = strlen(pattern);
+    i = found = 0;
+
     while ((c = getch_lnbuff()) != EOF) {
-        if (c == '\n') { /* newline */
-            if (except_flag && !match) {
-                print_lineno();
-                flush_lnbuff();
-                putchar('\n');
-            }
-            match = 0;
-            lineno++;
-        }
-        if (c != pattern[i])
-            i = 0;
-        else if (++i == plen) { // found match
-            if (except_flag) {
-                match = 1;
-                continue;
-            }
-            i = 0;
+        i = (c == pattern[i]) ? i+1 : 0;
+
+        if (except_flag && i == plen)
+            ignoreln_lnbuff();
+        else if (except_flag ? c == '\n' : i == plen) { // match
             found++;
-            print_lineno();
+            if (lineno_flag)
+                printf("%ld:", lineno);
             flush_lnbuff();
-            println(), lineno++; 
         }
     }
+
     return found;
-#undef print_lineno
 }
 
-/* println: prints next line from stdin
- * prints newline on EOF */
-void println()
-{
-    int c;
-    while ((c = getchar()) != EOF && c != '\n')
-        putchar(c);
-    putchar(c);
-}
 
 /* ------------------------ line buffer ---------------------- */
 
-#define LNBUFF_LEN 128
+#define LNBUFF_LEN 1024 
 
 /* the line buffer lenght must be a power of two */
 static_assert(!(LNBUFF_LEN % 2), "Line buffer length is not a power of two!");
 
+
+long lineno;
 /* line_buffer: global overflowing line buffer */
 struct {
     char self[LNBUFF_LEN];
@@ -82,6 +61,7 @@ int getch_lnbuff()
     if (lnbuff.newline) {
         lnbuff.len = 0;
         lnbuff.newline = 0; 
+        lineno++;
     }
     if (c == EOF || c == '\n') // new line
         lnbuff.newline = 1;
@@ -108,9 +88,22 @@ int flush_lnbuff()
     /* handle rest of chars */
     for (i = 0; i < LNBUFF_I; i++)
         putchar(lnbuff.self[i]);
-
-    i = lnbuff.len;
-    lnbuff.len = 0;
-    return i;
+    /* print unbuffered part of line */
+    if (!lnbuff.newline)
+        while ((i = getchar()) != EOF && i != '\n')
+            putchar(i);
+    putchar('\n');
+    lnbuff.newline = 1;
+    return lnbuff.len;
 }
 
+/* ignoreln_lnbuff: ignore line of input */
+void ignoreln_lnbuff()
+{
+    int c;
+    if (lnbuff.newline)
+        return;
+    while ((c = getchar()) != EOF && c != '\n')
+        ;
+    lnbuff.newline = 1;
+}