From 0e4faead440021d608c9321a8cae2e3cd8392639 Mon Sep 17 00:00:00 2001
From: emma <emma@tebibyte.media>
Date: Tue, 29 Aug 2023 13:17:35 -0600
Subject: [PATCH] tail(1p): segfaults for some reason lol

---
 src/tail.c | 89 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 72 insertions(+), 17 deletions(-)

diff --git a/src/tail.c b/src/tail.c
index d27829f..61b9f89 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -22,26 +22,78 @@
 #include <sysexits.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <unistd.h>
 
 #include "yac.h"
 
-void tail(FILE *file, bool c, bool f, long num) {
-	long offset;
-	if (c) { fseek(file, offset, SEEK_END); }
-	else {
-		for 
+void tailc(FILE *file, long num) {
+	int byte;
+	char buf[num];
+	long offset = -num;
+
+	fseek(file, offset, SEEK_END);
+	for (int i = 0; (byte = fgetc(file)) != EOF; i++) {
+		buf[i] = byte;
 	}
 
+	fputs(buf, stdout);
+}
+
+void tailf(FILE *file) {
+	int byte;
+
+	while(true) {
+		if ((byte = fgetc(file)) != EOF) { putchar(byte); }
+	}
+}
+
+void tailn(FILE *file, long num) {
+	char *buf = calloc(4096, 1);
+	char *lines[num];
+	int byte;
+	int lc = 0;
+
+	for (int bc = 0; (byte = fgetc(file)) != EOF; bc++) {
+		if (bc == sizeof(buf)) {
+			int err;
+			if (err = realloc(buf, sizeof(buf) * 2) == NULL) {
+				// TODO: error handling
+			}
+		}
+
+		buf[bc] = byte;
+
+		if (byte == '\n') {
+			lines[lc] = buf;
+			bc = 0;
+			lc++;
+		}
+
+		if (lc == num) {
+			for (int i = 0; i < lc; i++) {
+				lines[i] = lines[i + 1];
+			}
+			lc--;
+		}
+	}
+
+	int i;
+	if ((i = lc - num) < 0) { i = 0; }
+
+	for (; i < lc; i++) {
+		fputs(lines[i], stdout);
+	}
 }
 
 int main(int argc, char *argv[]) {
 	bool c = false;
 	bool f = false;
 	bool n = false;
-	long num;
-	int opt;
 	int i;
+	int opt;
+	long num;
+	void (*fn)(FILE *, long) = tailn;
 
 	extern int optind;
 	while ((opt = getopt(argc, argv, "c:fn:")) != -1) {
@@ -87,6 +139,7 @@ int main(int argc, char *argv[]) {
 		 */
 			case 'c':
 				c = true;
+				fn = tailc;
 				num = (long)optarg;
 				break;
 			case 'f':
@@ -116,19 +169,21 @@ int main(int argc, char *argv[]) {
 		return EX_USAGE;
 	}
 
-	if (optind = argc) {
-		tail(stdin, c, f, num);
-	}
-	
 	FILE *file;
 
-	for (i = optind; i < argc; i++) {
-		file = rfile(argv0, argv[i]);
-		if file != NULL {
-			tail(file, c, f, num);
-			if (file != stdin) { fclose(file); }
+	if (optind = argc) {
+		fn(stdin, num);
+
+		if (f) { tailf(stdin); }
+	} else {
+		for (i = optind; i < argc; i++) {
+			if ((file = rpath(argv[0], argv[i])) != NULL) {
+				fn(file, num);
+				fclose(file);
+			}
+
+			if (f) { tailf(file); }
 		}
 	}
-
 	return EX_OK;
 }