move String#clear to mruby-string-ext; ref #2370

2 files changed, 53 insertions, 0 deletions

diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index f04f12c4b..48146944d 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -239,6 +239,37 @@ mrb_str_lines(mrb_state *mrb, mrb_value self)
   return result;
 }
 
+/*
+ *  call-seq:
+ *     string.clear    ->  string
+ *
+ *  Makes string empty.
+ *
+ *     a = "abcde"
+ *     a.clear    #=> ""
+ */
+static mrb_value
+mrb_str_clear(mrb_state *mrb, mrb_value str)
+{
+  struct RString *s = mrb_str_ptr(str);
+
+  if (!RSTR_SHARED_P(s) && !RSTR_EMBED_P(s)) {
+    if (s->flags & MRB_STR_NOFREE) {
+      s->flags &= ~MRB_STR_NOFREE;
+    }
+    else {
+      mrb_free(mrb, s->as.heap.ptr);
+    }
+    s->as.heap.ptr = 0;
+    s->as.heap.len = 0;
+  }
+  RSTR_UNSET_SHARED_FLAG(s);
+  RSTR_SET_EMBED_FLAG(s);
+  RSTR_SET_EMBED_LEN(s, 0);
+  RSTRING_PTR(str)[0] = '\0';
+  return str;
+}
+
 void
 mrb_mruby_string_ext_gem_init(mrb_state* mrb)
 {
@@ -256,6 +287,7 @@ mrb_mruby_string_ext_gem_init(mrb_state* mrb)
   mrb_define_method(mrb, s, "oct",             mrb_str_oct,             MRB_ARGS_NONE());
   mrb_define_method(mrb, s, "chr",             mrb_str_chr,             MRB_ARGS_NONE());
   mrb_define_method(mrb, s, "lines",           mrb_str_lines,           MRB_ARGS_NONE());
+  mrb_define_method(mrb, s, "clear",           mrb_str_clear,           MRB_ARGS_NONE());
 }
 
 void
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index 0ef92b35a..72c919b35 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -172,3 +172,24 @@ assert('String#lines') do
   assert_equal ["\n", "\n", "\n"], "\n\n\n".lines
   assert_equal [], "".lines
 end
+
+assert('String#clear') do
+  # embed string
+  s = "foo"
+  assert_equal("", s.clear)
+  assert_equal("", s)
+
+  # not embed string and not shared string
+  s = "foo" * 100
+  a = s
+  assert_equal("", s.clear)
+  assert_equal("", s)
+  assert_equal("", a)
+
+  # shared string
+  s = "foo" * 100
+  a = s[10, 90]                # create shared string
+  assert_equal("", s.clear)    # clear
+  assert_equal("", s)          # s is cleared
+  assert_not_equal("", a)      # a should not be affected
+end