# In Buffers, the internal sequence of character is mutable
# Thus, `chars` can be used to modify the buffer.
redef fun chars: Sequence[Char] is abstract
+
+ # Appends `length` chars from `s` starting at index `from`
+ #
+ # ~~~nit
+ # var b = new Buffer
+ # b.append_substring("abcde", 1, 2)
+ # assert b == "bc"
+ # b.append_substring("vwxyz", 2, 3)
+ # assert b == "bcxyz"
+ # b.append_substring("ABCDE", 4, 300)
+ # assert b == "bcxyzE"
+ # b.append_substring("VWXYZ", 400, 1)
+ # assert b == "bcxyzE"
+ # ~~~
+ fun append_substring(s: Text, from, length: Int) do
+ if from < 0 then
+ length += from
+ from = 0
+ end
+ var ln = s.length
+ if (length + from) > ln then length = ln - from
+ if length <= 0 then return
+ append_substring_impl(s, from, length)
+ end
+
+ # Unsafe version of `append_substring` for performance
+ #
+ # NOTE: Use only if sure about `from` and `length`, no checks
+ # or bound recalculation is done
+ fun append_substring_impl(s: Text, from, length: Int) do
+ var pos = from
+ for i in [0 .. length[ do
+ self.add s[pos]
+ pos += 1
+ end
+ end
end
# View for chars on Buffer objects, extends Sequence
return cp >= 0xD800 and cp <= 0xDFFF
end
+ # Is `self` a UTF-16 high surrogate ?
+ fun is_hi_surrogate: Bool do
+ var cp = code_point
+ return cp >= 0xD800 and cp <= 0xDBFF
+ end
+
+ # Is `self` a UTF-16 low surrogate ?
+ fun is_lo_surrogate: Bool do
+ var cp = code_point
+ return cp >= 0xDC00 and cp <= 0xDFFF
+ end
+
# Length of `self` in a UTF-8 String
fun u8char_len: Int do
var c = self.code_point