start string.h

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