From c29bc365146cc3800b2bebfaa3dff1461240668f Mon Sep 17 00:00:00 2001
From: pommicket <pommicket@gmail.com>
Date: Wed, 16 Feb 2022 15:57:45 -0500
Subject: start string.h

---
 05/main.c   | 20 +++++-------------
 05/string.h | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 15 deletions(-)

diff --git a/05/main.c b/05/main.c
index d16347e..6757ec7 100644
--- a/05/main.c
+++ b/05/main.c
@@ -3,7 +3,7 @@
 #include <stdio.h>
 #include <signal.h>
 #include <stdlib.h>
-
+#include <string.h>
 
 int compar(const void *a, const void *b) {
 	int i = *(int *)a;
@@ -14,20 +14,10 @@ int compar(const void *a, const void *b) {
 }
 
 int main(int argc, char **argv) {
-	ldiv_t l = ldiv(1000000000007, 5937448);
-	printf("%ld %ld\n",l.quot,l.rem);
-	int nums[10] = {8,34,1086,3872,-123,5873,3843,1762,INT_MAX,INT_MIN};
-	int i;
-	for (i = 0; i < 10; ++i) nums[i] = abs(nums[i]);
-	qsort(nums, 10, sizeof(int), compar);
-	for (i = 0; i < 10; ++i) printf("%d ", nums[i]);
-	printf("\n");
-	int search = 34;
-	int *p = bsearch(&search, nums, 10, sizeof(int), compar);
-	if (p)
-		printf("Found %d\n",*p);
-	else
-		printf("No match\n");
+	char buf[36];
+	memset(buf, 'a', sizeof buf);
+	strncpy(buf, "hello, world!\n",36);
+	printf("%d\n",strcmp(buf, "hello, world!\n"));
 	return 0;
 }
 
diff --git a/05/string.h b/05/string.h
index e585f6b..9b59637 100644
--- a/05/string.h
+++ b/05/string.h
@@ -4,5 +4,72 @@
 #include <stdc_common.h>
 
 
+void *memmove(void *s1, const void *s2, size_t n) {
+	if (s1 < s2) return memcpy(s1, s2, n); // our memcpy does a forwards copy
+	// backwards copy
+	char *p = (char*)s1 + n, *q = (char*)s2 + n;
+	while (p > s1)
+		*--p = *--q;
+	return s1;
+}
+
+char *strcpy(char *s1, const char *s2) {
+	char *p = s1 - 1, *q = s2 - 1;
+	while ((*++p = *++q));
+	return s1;
+}
+
+char *strncpy(char *s1, const char *s2, size_t n) {
+	char *p = s1 - 1, *q = s2 - 1;
+	size_t i;
+	for (i = 0; i < n; ++i)
+		if (!(*++p = *++q))
+			break;
+	for (; i < n; ++i)
+		*++p = 0;
+	return s1;
+}
+
+char *strcat(char *s1, const char *s2) {
+	return strcpy(s1 + strlen(s1), s2);
+}
+
+char *strncat(char *s1, const char *s2, size_t n) {
+	// oddly, not equivalent to strncpy(s1 + strlen(s1), s2, n)
+	char *p = s1 + strlen(s1) - 1, *q = s2 - 1;
+	size_t i;
+	for (i = 0; i < n; ++i)
+		if (!(*++p = *++q))
+			break;
+	*++p = 0;
+	return s1;
+}
+
+int memcmp(const void *s1, const void *s2, size_t n) {
+	char *p = s1, *q = s2;
+	size_t i;
+	for (i = 0; i < n; ++i, ++p, ++q) {
+		if (*p > *q)
+			return 1;
+		if (*p < *q)
+			return -1;
+	}
+	return 0;
+}
+
+int strcmp(const char *s1, const char *s2) {
+	char *p = s1, *q = s2;
+	for (; *p && *q; ++p, ++q) {
+		if (*p > *q)
+			return 1;
+		if (*p < *q)
+			return -1;
+	}
+	if (*p > *q)
+		return 1;
+	if (*p < *q)
+		return -1;
+	return 0;
+}
 
 #endif // _STRING_H
-- 
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