--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lib/string.c	Fri May 26 23:11:05 2017 +0900
@@ -0,0 +1,144 @@
+#include "types.h"
+#include "arm.h"
+
+
+void* memset(void *dst, int v, int n)
+{
+    uint8	*p;
+    uint8	c;
+    uint32	val;
+    uint32	*p4;
+
+    p   = dst;
+    c   = v & 0xff;
+    val = (c << 24) | (c << 16) | (c << 8) | c;
+
+    // set bytes before whole uint32
+    for (; (n > 0) && ((uint)p % 4); n--, p++){
+        *p = c;
+    }
+
+    // set memory 4 bytes a time
+    p4 = (uint*)p;
+
+    for (; n >= 4; n -= 4, p4++) {
+        *p4 = val;
+    }
+
+    // set leftover one byte a time
+    p = (uint8*)p4;
+
+    for (; n > 0; n--, p++) {
+        *p = c;
+    }
+
+    return dst;
+}
+
+
+int memcmp(const void *v1, const void *v2, uint n)
+{
+    const uchar *s1, *s2;
+
+    s1 = v1;
+    s2 = v2;
+
+    while(n-- > 0){
+        if(*s1 != *s2) {
+            return *s1 - *s2;
+        }
+
+        s1++, s2++;
+    }
+
+    return 0;
+}
+
+void* memmove(void *dst, const void *src, uint n)
+{
+    const char *s;
+    char *d;
+
+    s = src;
+    d = dst;
+
+    if(s < d && s + n > d){
+        s += n;
+        d += n;
+
+        while(n-- > 0) {
+            *--d = *--s;
+        }
+
+    } else {
+        while(n-- > 0) {
+            *d++ = *s++;
+        }
+    }
+
+    return dst;
+}
+
+// memcpy exists to placate GCC.  Use memmove.
+void* memcpy(void *dst, const void *src, uint n)
+{
+    return memmove(dst, src, n);
+}
+
+int strncmp(const char *p, const char *q, uint n)
+{
+    while(n > 0 && *p && *p == *q) {
+        n--, p++, q++;
+    }
+
+    if(n == 0) {
+        return 0;
+    }
+
+    return (uchar)*p - (uchar)*q;
+}
+
+char* strncpy(char *s, const char *t, int n)
+{
+    char *os;
+
+    os = s;
+
+    while(n-- > 0 && (*s++ = *t++) != 0)
+        ;
+
+    while(n-- > 0) {
+        *s++ = 0;
+    }
+
+    return os;
+}
+
+// Like strncpy but guaranteed to NUL-terminate.
+char* safestrcpy(char *s, const char *t, int n)
+{
+    char *os;
+
+    os = s;
+
+    if(n <= 0) {
+        return os;
+    }
+
+    while(--n > 0 && (*s++ = *t++) != 0)
+        ;
+
+    *s = 0;
+    return os;
+}
+
+int strlen(const char *s)
+{
+    int n;
+
+    for(n = 0; s[n]; n++)
+        ;
+
+    return n;
+}
+