Add file operations

builtins/open.go

@@ -0,0 +1,86 @@
+package builtins
+
+import (
+	"fmt"
+	"log"
+	"monkey/object"
+	"monkey/typing"
+	"os"
+	"syscall"
+)
+
+// Close  ...
+func parseMode(mode string) (int, error) {
+	var flag int
+	for _, c := range mode {
+		switch c {
+		case 'r':
+			if (flag & os.O_WRONLY) != 0 {
+				flag |= os.O_RDWR
+			} else {
+				log.Printf("r2")
+				flag |= os.O_RDONLY
+			}
+		case 'w':
+			if (flag & os.O_RDONLY) != 0 {
+				flag |= os.O_RDWR
+			} else {
+				flag |= os.O_WRONLY
+			}
+		case 'a':
+			flag |= os.O_APPEND
+		default:
+			return 0, fmt.Errorf("ValueError: mode string must be one of 'r', 'w', 'a', not '%c'", c)
+		}
+	}
+
+	if (flag&os.O_WRONLY) != 0 || (flag&os.O_RDWR) != 0 {
+		log.Printf("c1")
+		flag |= os.O_CREATE
+		if (flag & os.O_APPEND) == 0 {
+			log.Printf("t1")
+			flag |= os.O_TRUNC
+		}
+	}
+
+	if !((flag == os.O_RDONLY) || (flag&os.O_WRONLY != 0) || (flag&os.O_RDWR != 0)) {
+		return 0, fmt.Errorf("ValueError: mode string must be at least one of 'r', 'w', or 'rw'")
+	}
+
+	return flag, nil
+}
+
+// Open ...
+func Open(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"open", args,
+		typing.RangeOfArgs(1, 2),
+		typing.WithTypes(object.STRING_OBJ, object.STRING_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	var (
+		filename string
+		mode            = "r"
+		perm     uint32 = 0640
+	)
+
+	filename = args[0].(*object.String).Value
+
+	if len(args) == 2 {
+		mode = args[1].(*object.String).Value
+	}
+
+	flag, err := parseMode(mode)
+	if err != nil {
+		return newError(err.Error())
+	}
+
+	fd, err := syscall.Open(filename, flag, perm)
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.Integer{Value: int64(fd)}
+}