From b7b37e986c7e4ca819f9cbbf683033f149f74e4b Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Thu, 28 Apr 2022 11:36:53 -0400
Subject: implement -Fi

---
 grep.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 47 insertions(+), 11 deletions(-)

diff --git a/grep.c b/grep.c
index 73d9220..56e7769 100644
--- a/grep.c
+++ b/grep.c
@@ -31,11 +31,13 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 struct grep_list {
 	struct grep_list *next;
 	char *string;
+	size_t len;
 	regex_t re;
 };
 
@@ -46,27 +48,55 @@ static int grep_inverse = 0;
 static int grep_silent = 0;
 static int grep_exact = 0;
 
-static int grep_match(struct grep_list *head, const char *buf)
+static int grep_match_re(struct grep_list *head, const char *buf)
 {
 	for (struct grep_list *c = head; c != NULL; c = c->next) {
-		if (c->string) {
-			if (grep_exact && strcmp(buf, c->string) == 0) {
-				return !grep_inverse;
-			}
-			if (!grep_exact && strstr(buf, c->string)) {
-				return !grep_inverse;
-			}
-			continue;
+		if (regexec(&(c->re), buf, 0, NULL, 0) == 0) {
+			return !grep_inverse;
 		}
+	}
 
-		if (regexec(&(c->re), buf, 0, NULL, 0) == 0) {
+	return grep_inverse;
+}
+
+static int grep_match_fixed(struct grep_list *head, const char *buf)
+{
+	for (struct grep_list *c = head; c != NULL; c = c->next) {
+		if (grep_exact && strcmp(buf, c->string) == 0) {
+			return !grep_inverse;
+		}
+		if (!grep_exact && strstr(buf, c->string)) {
 			return !grep_inverse;
 		}
 	}
+	return grep_inverse;
+}
 
+static int grep_match_fixedcase(struct grep_list *head, const char *buf)
+{
+	size_t blen = strlen(buf);
+	for (struct grep_list *c = head; c != NULL; c = c->next) {
+		if (grep_exact && strcasecmp(buf, c->string) == 0) {
+			return !grep_inverse;
+		}
+		if (grep_exact) {
+			continue;
+		}
+		if (blen <= c->len) {
+			continue;
+		}
+		
+		for (size_t i = 0; i < (blen - c->len); i++) {
+			if (strncasecmp(buf + i, c->string, c->len) == 0) {
+				return !grep_inverse;
+			}
+		}
+	}
 	return grep_inverse;
 }
 
+static int (*grep_match)(struct grep_list *head, const char *buf) = grep_match_re;
+
 static uintmax_t grep(struct grep_list *head, const char *path)
 {
 	FILE *f = stdin;
@@ -144,6 +174,7 @@ static struct grep_list * grep_add_list(struct grep_list *head, char *s)
 		}
 
 		node->string = strdup(pattern);
+		node->len = strlen(node->string);
 
 		pattern = strtok(NULL, "\n");
 	}
@@ -176,7 +207,7 @@ int main(int argc, char *argv[])
 
 	int flags = REG_NOSUB;
 	struct grep_list *head = NULL;
-	enum {REGEX, FIXED } type = REGEX;
+	enum { REGEX, FIXED } type = REGEX;
 
 	int c;
 	while ((c = getopt(argc, argv, "EFce:f:ilnqsvx")) != -1) {
@@ -187,6 +218,7 @@ int main(int argc, char *argv[])
 
 		case 'F':
 			type = FIXED;
+			grep_match = grep_match_fixed;
 			break;
 
 		case 'c':
@@ -242,6 +274,10 @@ int main(int argc, char *argv[])
 		head = grep_add_list(head, argv[optind++]);
 	}
 
+	if (type == FIXED && (flags & REG_ICASE)) {
+		grep_match = grep_match_fixedcase;
+	}
+
 	if (type != FIXED) {
 		for (struct grep_list *c = head; c != NULL; c = c->next) {
 			int e = regcomp(&(c->re), c->string, flags);
-- 
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