ungetc

static VALUE rb_gzreader_ungetc(VALUE obj, VALUE s) { struct gzfile *gz; if (FIXNUM_P(s)) return rb_gzreader_ungetbyte(obj, s); gz = get_gzfile(obj); StringValue(s); if (gz->enc2 && gz->enc2 != rb_ascii8bit_encoding()) { s = rb_str_conv_enc(s, rb_enc_get(s), gz->enc2); } gzfile_ungets(gz, (const Bytef*)RSTRING_PTR(s), RSTRING_LEN(s)); RB_GC_GUARD(s); return Qnil; }