os: implement cp for nix

vlib/builtin/cfns.c.v

@@ -411,3 +411,6 @@ fn C.pthread_mutex_init(voidptr, voidptr) int
 fn C.pthread_mutex_lock(voidptr) int
 fn C.pthread_mutex_unlock(voidptr) int
 
+fn C.read(fd int, buf voidptr, count size_t) int
+fn C.write(fd int, buf voidptr, count size_t) int
+fn C.close(fd int) int

vlib/net/socket.v

@@ -62,12 +62,8 @@ fn C.send() int
 
 fn C.recv() int
 
-fn C.read() int
-
 fn C.shutdown() int
 
-fn C.close() int
-
 fn C.ntohs() int
 
 fn C.getsockname() int

vlib/net/websocket/io.v

@@ -1,7 +1,5 @@
 module websocket
 
-fn C.write() int
-
 fn (mut ws Client) write_to_server(buf voidptr, len int) int {
 	mut bytes_written := 0
 	ws.write_lock.lock()

vlib/os/os.v

@@ -207,7 +207,6 @@ pub fn mv(old, new string) {
 }
 
 fn C.CopyFile(&u32, &u32, int) int
-// TODO implement actual cp for linux
 pub fn cp(old, new string) ?bool {
 	$if windows {
 		w_old := old.replace('/', '\\')
@@ -221,8 +220,34 @@ pub fn cp(old, new string) ?bool {
 			return error_with_code('failed to copy $old to $new', int(result))
 		}
 	} $else {
-		os.system('cp "$old" "$new"')
+		fp_from := C.open(old.str, C.O_RDONLY)
-		return true // TODO make it return true or error when cp for linux is implemented
+		if fp_from < 0 { // Check if file opened
+			return error_with_code('cp: failed to open $old', int(fp_from))
+		}
+		fp_to := C.open(new.str, C.O_WRONLY | C.O_CREAT | C.O_TRUNC)
+		if fp_to < 0 { // Check if file opened (permissions problems ...)
+			C.close(fp_from)
+			return error_with_code('cp: failed to write to $new', int(fp_to))
+		}
+		mut buf := [1024]byte
+		mut count := 0
+		for {
+			// FIXME: use sizeof, bug: 'os__buf' undeclared
+			//count = C.read(fp_from, buf, sizeof(buf))
+			count = C.read(fp_from, buf, 1024)
+			if count == 0 {
+				break
+			}
+			if C.write(fp_to, buf, count) < 0 {
+				return error_with_code('cp: failed to write to $new', int(-1))
+			}
+		}
+		from_attr := C.stat{}
+		C.stat(old.str, &from_attr)
+		if C.chmod(new.str, from_attr.st_mode) < 0 {
+			return error_with_code('failed to set permissions for $new', int(-1))
+		}
+		return true
 	}
 }