method

ungetc

v1_9_1_378 - Show latest stable - 0 notes - Class: StringIO

ungetc(p1) public

Pushes back one character (passed as a parameter) onto strio such that a subsequent buffered read will return it. Pushing back behind the beginning of the buffer string is not possible. Nothing will be done if such an attempt is made. In other case, there is no limitation for multiple pushbacks.

Show source

static VALUE
strio_ungetc(VALUE self, VALUE c)
{
    struct StringIO *ptr = readable(StringIO(self));
    long lpos, clen;
    char *p, *pend;
    rb_encoding *enc, *enc2;

    if (NIL_P(c)) return Qnil;
    if (FIXNUM_P(c)) {
        int cc = FIX2INT(c);
        char buf[16];

        enc = rb_enc_get(ptr->string);
        rb_enc_mbcput(cc, buf, enc);
        c = rb_enc_str_new(buf, rb_enc_codelen(cc, enc), enc);
    }
    else {
        SafeStringValue(c);
        enc = rb_enc_get(ptr->string);
        enc2 = rb_enc_get(c);
        if (enc != enc2 && enc != rb_ascii8bit_encoding()) {
            c = rb_str_conv_enc(c, enc2, enc);
        }
    }
    /* get logical position */
    lpos = 0; p = RSTRING_PTR(ptr->string); pend = p + ptr->pos;
    for (;;) {
        clen = rb_enc_mbclen(p, pend, enc);
        if (p+clen >= pend) break;
        p += clen;
        lpos++;
    }
    clen = p - RSTRING_PTR(ptr->string);
    rb_str_update(ptr->string, lpos, ptr->pos ? 1 : 0, c);
    ptr->pos = clen;

    return Qnil;
}

ungetc

Related methods