From e6c6534a3d68a7cec461f115f14d8a9a2d681a90 Mon Sep 17 00:00:00 2001
From: Mattia Cabrini <dev@mattiacabrini.com>
Date: Tue, 9 Sep 2025 18:45:58 +0200
Subject: [PATCH] +Buffered reading (6.3x times faster)

---
 cmc-find.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 59 insertions(+), 8 deletions(-)

diff --git a/cmc-find.c b/cmc-find.c
index c06cd26..5fa4093 100644
--- a/cmc-find.c
+++ b/cmc-find.c
@@ -11,6 +11,10 @@
 #define MAX_LEN 64
 #endif
 
+#ifndef BUF_LEN
+#define BUF_LEN (64*1024)
+#endif
+
 typedef struct cs_t {
 	char buf[MAX_LEN];
 
@@ -19,11 +23,24 @@ typedef struct cs_t {
 	size_t start;		/* index of firs char */
 } *cs;
 
+typedef struct buf_t {
+	char buf[BUF_LEN];
+
+	FILE *fp;
+	size_t cap /* max string size; <= MAX_LEN */ ;
+	size_t cur;
+} *buf;
+
 static void cs_init(cs S, size_t cap);
 static void cs_add(cs S, char ch);
 static int cs_cmp(cs S, char *ch);
 static void cs_print(cs S);
 
+static void buf_init(buf B, FILE *);
+static void buf_read(buf B);
+static char buf_next_ch(buf B);
+static int buf_eof(buf B);
+
 int main(int argc, char **argv)
 {
 	int ch = 0;
@@ -31,7 +48,8 @@ int main(int argc, char **argv)
 	time_t now;
 
 	char str[MAX_LEN];
-	struct cs_t matcher;
+	struct cs_t S;
+	struct buf_t B;
 
 	if (argc < 2) {
 		printf("Usage: %s <string to find>\n", argv[0]);
@@ -41,15 +59,20 @@ int main(int argc, char **argv)
 	printf("Check against %s\n", str);
 
 	now = time(0);
-	cs_init(&matcher, strlen(str));
+	buf_init(&B, stdin);
+	cs_init(&S, strlen(str));
+
+	for (n = 1;; ++n) {
+		ch = buf_next_ch(&B);
+		if (!ch && buf_eof(&B))
+			break;
 
-	for (n = 1; (ch = fgetc(stdin)) != EOF; ++n) {
-		cs_add(&matcher, ch);
+		cs_add(&S, ch);
 
-		if (matcher.len == matcher.cap) {
-			if (cs_cmp(&matcher, str)) {
-				printf("Found at %llu\t%lu\n", n - matcher.cap, time(0) - now);
-				/* cs_print(&matcher); printf("\n"); */
+		if (S.len == S.cap) {
+			if (cs_cmp(&S, str)) {
+				printf("Found at %llu\t%lu\n", n - S.cap, time(0) - now);
+				/* cs_print(&S); printf("\n"); */
 			}
 		}
 	}
@@ -132,3 +155,31 @@ static void cs_print(cs S)
 		++count;
 	}
 }
+
+static void buf_init(buf B, FILE * fp)
+{
+	B->cap = 0;
+	B->cur = 0;
+	B->fp = fp;
+}
+
+static void buf_read(buf B)
+{
+	B->cap = fread(B->buf, 1, sizeof(B->buf), B->fp);
+	B->cur = 0;
+}
+
+static char buf_next_ch(buf B)
+{
+	if (B->cur >= B->cap) {
+		buf_read(B);
+		if (B->cap == 0)
+			return '\0';
+	}
+	return B->buf[B->cur++];
+}
+
+static int buf_eof(buf B)
+{
+	return feof(B->fp) && B->cur >= B->cap;
+}
-- 
2.43.0