From: Tanaka Akira <akr@...>
Date: 2008-01-28T00:59:49+09:00
Subject: [ruby-dev:33428] Re: Binary String

In article <E1JHWLe-0002wx-S6@x61.netlab.jp>,
  Yukihiro Matsumoto <matz@ruby-lang.org> writes:

> みなさんはどう思います？ 私は非対称性が気になるので、
>
>   * b=s.bytes; b[1] = b[1]+1
>   * s.byte(1)=s.byte(1)+1
>   * s.set_byte(1,s.byte(1)+1)
>
> のようなのがいいかなあと思ってますが。

String#byte と String#set_byte ならこんなですかね。

でも、String#byte って String#bytes と名前が似すぎてませんか
ね。get_byte にして bytes とは離したほうがいいような感じが
ちょっと。

Index: string.c
===================================================================
--- string.c	(revision 15281)
+++ string.c	(working copy)
@@ -3074,6 +3074,49 @@ rb_str_chr(VALUE str)
 
 /*
  *  call-seq:
+ *     str.byte(index)          => 0 .. 255
+ *
+ *  returns the <i>index</i>th byte as an integer.
+ */
+static VALUE
+rb_str_byte(VALUE str, VALUE index)
+{
+    long pos = NUM2LONG(index);
+
+    if (pos < 0)
+        pos += RSTRING_LEN(str);
+    if (pos < 0 ||  RSTRING_LEN(str) <= pos)
+        return Qnil;
+
+    return INT2FIX((unsigned char)RSTRING_PTR(str)[pos]);
+}
+
+/*
+ *  call-seq:
+ *     str.set_byte(index, int) => int
+ *
+ *  modifies the <i>index</i>th byte as <i>int</i>.
+ */
+static VALUE
+rb_str_set_byte(VALUE str, VALUE index, VALUE value)
+{
+    long pos = NUM2LONG(index);
+    int byte = NUM2INT(value);
+
+    rb_str_modify(str);
+
+    if (pos < -RSTRING_LEN(str) || RSTRING_LEN(str) <= pos)
+        rb_raise(rb_eIndexError, "index %ld out of string", pos);
+    if (pos < 0)
+        pos += RSTRING_LEN(str);
+
+    RSTRING_PTR(str)[pos] = byte;
+
+    return value;
+}
+
+/*
+ *  call-seq:
  *     str.reverse   => new_str
  *  
  *  Returns a new string with the characters from <i>str</i> in reverse order.
@@ -6054,6 +6097,8 @@ Init_String(void)
     rb_define_method(rb_cString, "replace", rb_str_replace, 1);
     rb_define_method(rb_cString, "clear", rb_str_clear, 0);
     rb_define_method(rb_cString, "chr", rb_str_chr, 0);
+    rb_define_method(rb_cString, "byte", rb_str_byte, 1);
+    rb_define_method(rb_cString, "set_byte", rb_str_set_byte, 2);
 
     rb_define_method(rb_cString, "to_i", rb_str_to_i, -1);
     rb_define_method(rb_cString, "to_f", rb_str_to_f, 0);
-- 
[田中 哲][たなか あきら][Tanaka Akira]