简要：Xstring和String的字符串长度 可变，可以指定最大长度，而且最大长度没上限。
函数：STRING 转XSTRING
DATA: i_str TYPE STRING,
e_xstr TYPE XTRING.
CALL FUNCTION ‘SCMS_STRING_TO_XSTRING’
EXPORTING
text = i_str
IMPORTING
buffer = e_xstr.

函数：XSTRING转STRING

DATA: i_str TYPE STRING,
e_xstr TYPE XTRING.
data: lv_bin_size type i.
data: lt_bin_tab like gt_bin_tab[].

call function ‘SCMS_XSTRING_TO_BINARY’
exporting
BUFFER = i_xstr
importing
OUTPUT_LENGTH = Lv_bin_SIZE
tables
BINARY_TAB = lt_bin_tab.

• 将二进制内表转换（拼接）成一个字符串
  CALL FUNCTION ‘SCMS_BINARY_TO_STRING’
  EXPORTING
  input_length = lv_bin_size
  IMPORTING
  text_buffer = e_str
  TABLES
  binary_tab = lt_bin_tab.