kernel: add stdlib.[ch]

3 files changed, 49 insertions, 2 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 7250696..431c01a 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -1,7 +1,7 @@
 all: kernel.elf
 
-OBJS=entry.o tty.o
-HEADERS=tty.h
+OBJS=entry.o stdlib.o tty.o
+HEADERS=stdlib.h tty.h
 
 .SUFFIXES: .asm
 
@@ -20,6 +20,8 @@ kernel.elf: kernel.o $(OBJS) $(HEADERS)
 
 entry.o: entry.asm
 
+stdlib.o: stdlib.c stdlib.h
+
 tty.o: tty.c tty.h
 
 
diff --git a/kernel/stdlib.c b/kernel/stdlib.c
new file mode 100644
index 0000000..92fdec2
--- /dev/null
+++ b/kernel/stdlib.c
@@ -0,0 +1,33 @@
+#include "stdlib.h"
+
+void *memset(void *s, int c, size_t n)
+{
+    char *p = (char *) s;
+
+    for (size_t i = 0; i < n; i++, p++)
+        *p = (char) c;
+
+    return s;
+}
+
+/* overlap is not handled */
+void *memcpy(void *dest, void *src, size_t n)
+{
+    char *s = (char *) src;
+    char *d = (char *) dest;
+
+    for (size_t i = 0; i < n; i++, s++, d++)
+        *d = *s;
+
+    return dest;
+}
+
+int strncmp(const char *s1, const char *s2, size_t n)
+{
+    for (size_t i = 0; i < n; i++, s1++, s2++) {
+        if (*s1 < *s2) return -1;
+        if (*s1 > *s2) return 1;
+    }
+
+    return 0;
+}
diff --git a/kernel/stdlib.h b/kernel/stdlib.h
new file mode 100644
index 0000000..58bc3fa
--- /dev/null
+++ b/kernel/stdlib.h
@@ -0,0 +1,12 @@
+#ifndef _STDLIB_H_
+#define _STDLIB_H_
+
+#include "types.h"
+
+void *memset(void *s, int c, size_t n);
+
+void *memcpy(void *dest, void *src, size_t n);
+
+int strncmp(const char *s1, const char *s2, size_t n);
+
+#endif