process control and context switch

common.c

@@ -1,5 +1,41 @@
 #include "common.h"
 
+void *memcpy(void *dst, const void *src, size_t n) {
+  uint8_t *d = (uint8_t *) dst;
+  const uint8_t *s = (const uint8_t *) src;
+  while (n--)
+      *d++ = *s++;
+  return dst;
+}
+
+void *memset(void *buf, char c, size_t n) {
+  uint8_t *p = (uint8_t *) buf;
+  while (n--)
+      *p++ = c;
+  return buf;
+}
+
+char *strcpy(char *dst, const char *src) {
+  char *d = dst;
+  while (*src)
+      *d++ = *src++;
+  *d = '\0';
+  return dst;
+} // The strcpy function continues copying even if
+  // src is longer than the memory area of dst. 
+  // This can easily lead to bugs and vulnerabilities
+
+int strcmp(const char *s1, const char *s2) {
+  while (*s1 && *s2) {
+    if (*s1 != *s2)
+        break;
+    s1++;
+    s2++;
+  }
+
+  return *(unsigned char *)s1 - *(unsigned char *)s2;
+}
+
 void putchar(char ch);
 
 void printf(const char *fmt, ...) {
@@ -62,39 +98,3 @@ void printf(const char *fmt, ...) {
 end:
   va_end(vargs);
 }
-
-void *memcpy(void *dst, const void *src, size_t n) {
-  uint8_t *d = (uint8_t *) dst;
-  const uint8_t *s = (const uint8_t *) src;
-  while (n--)
-    *d++ = *s++;
-  return dst;
-}
-
-void *memset(void *buf, char c, size_t n) {
-  uint8_t *p = (uint8_t *) buf;
-  while (n--)
-    *p++ = c;
-  return buf;
-}
-
-char *strcpy(char *dst, const char *src) {
-  char *d = dst;
-  while (*src)
-    *d++ = *src++;
-  *d = '\0';
-  return dst;
-} // The strcpy function continues copying even if
-  // src is longer than the memory area of dst. 
-  // This can easily lead to bugs and vulnerabilities
-
-int strcmp(const char *s1, const char *s2) {
-  while (*s1 && *s2) {
-    if (*s1 != *s2)
-      break;
-    s1++;
-    s2++;
-  }
-
-  return *(unsigned char *)s1 - *(unsigned char *)s2;
-}