method

ungetc

v1_8_7_330 - 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.

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/*
 * call-seq:
 *   strio.ungetc(integer)   -> nil
 *
 * 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.
 */
static VALUE
strio_ungetc(self, ch)
    VALUE self, ch;
{
    struct StringIO *ptr = readable(StringIO(self));
    int cc = NUM2INT(ch);
    long len, pos = ptr->pos;

    if (cc != EOF) {
        len = RSTRING(ptr->string)->len;
        if (pos == 0) {
            char *p;
            rb_str_resize(ptr->string, len + 1);
            p = RSTRING(ptr->string)->ptr;
            memmove(p + 1, p, len);
        }
        else {
            if (len < pos-- ||
                (unsigned char)RSTRING(ptr->string)->ptr[pos] !=
                (unsigned char)cc) {
                strio_extend(ptr, pos, 1);
            }
            --ptr->pos;
        }
        RSTRING(ptr->string)->ptr[pos] = cc;
        OBJ_INFECT(ptr->string, self);
        ptr->flags &= ~STRIO_EOF;
    }
    return Qnil;
}

ungetc

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