method

ungetc

v1_9_2_180 - 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. There is no limitation for multiple pushbacks including pushing back behind the beginning of the buffer string.

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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);
        }
    }
    if (RSTRING_LEN(ptr->string) < ptr->pos) {
        long len = RSTRING_LEN(ptr->string);
        rb_str_resize(ptr->string, ptr->pos - 1);
        memset(RSTRING_PTR(ptr->string) + len, 0, ptr->pos - len - 1);
        rb_str_concat(ptr->string, c);
        ptr->pos--;
    }
    else {
        /* 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

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