From 655452d663f6f9b32d450cc5d00c3005b7588ea1 Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.xyz>
Date: Mon, 18 Jan 2021 21:32:00 -0600
Subject: kernel: finish implementing string functions

Finish implementing the functions from string.h in string.c.

Signed-off-by: Danny Holman <dholman@gymli.xyz>
---
 kernel/string.c | 42 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 38 insertions(+), 4 deletions(-)

diff --git a/kernel/string.c b/kernel/string.c
index 3610909..5b5957c 100644
--- a/kernel/string.c
+++ b/kernel/string.c
@@ -1,19 +1,53 @@
 #include <kernel/string.h>
 
 int memcmp(const void *str1, const void *str2, size_t n) {
-        return 0;
+        unsigned char *p1 = str1;
+        unsigned char *p2 = str2;
+        int ret = 0;
+
+        if (str1 == str2)
+                return 0;
+
+        while (n > 0) {
+                if (*p1 != *p2) {
+                        ret = (*p1 > *p2)?1:-1;
+                        break;
+                }
+                n--;
+                p1++;
+                p2++;
+        }
+        return ret;
 }
 
 void* memcpy(void* __restrict dest, const void* __restrict src, size_t n) {
-        return NULL;
+        if (dest == src)
+                return dest;
+
+        unsigned char *pdest = dest;
+        unsigned char const *psrc = src;
+        for (size_t i = 0; i < n; i++)
+                pdest[i] = psrc[i];
+        return dest;
 }
 
 void* memmove(void* __restrict dest, const void* __restrict src, size_t n) {
-        return NULL;
+        if (dest == src)
+                return dest;
+
+        unsigned char const *psrc = src;
+        unsigned char buffer[n];
+
+        for (size_t i = 0; i < n; i++)
+                buffer[i] = psrc[i];
+        return memcpy(dest, (void*)buffer, n);
 }
 
 void* memset(void *str, int c, size_t n) {
-        return NULL;
+        unsigned char *p = str;
+        for (size_t i = 0; i < n; i++)
+                p[i] = (unsigned char)c;
+        return str;
 }
 
 size_t strlen(const char *str) {
-- 
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