libc: Add lseek()

libs/libc/include/bits/seek.h

@@ -0,0 +1,8 @@
+#ifndef _BITS_SEEK_H
+#define _BITS_SEEK_H
+
+#define SEEK_SET 0 // Seek from beginning of file.
+#define SEEK_CUR 1 // Seek from current position.
+#define SEEK_END 2 // Seek from end of file.
+
+#endif

libs/libc/include/stdio.h

@@ -4,7 +4,7 @@
 #include <stdarg.h>
 #include <stddef.h>
 
-#define SEEK_SET 0
+#include <bits/seek.h>
 
 typedef struct
 {

libs/libc/include/unistd.h

@@ -1,6 +1,7 @@
 #ifndef _UNISTD_H
 #define _UNISTD_H
 
+#include <bits/seek.h>
 #include <sys/types.h>
 
 #ifdef __cplusplus
@@ -32,6 +33,9 @@ extern "C"
     /* Closes the file descriptor fd. */
     int close(int fd);
 
+    /* Moves the read/write file offset for fd to offset, depending on whence. */
+    off_t lseek(int fd, off_t offset, int whence);
+
 #ifdef __cplusplus
 }
 #endif

libs/libc/src/unistd.cpp

@@ -89,4 +89,9 @@ extern "C"
     {
         return (int)syscall(SYS_close, fd);
     }
+
+    off_t lseek(int fd, off_t offset, int whence)
+    {
+        return syscall(SYS_seek, fd, offset, whence);
+    }
 }