g_get_tag_and_length
g_get_tag_and_length(unsigned char **, int, unsigned int, unsigned int *);
if (g_get_tag_and_length(buff_in, (CONTEXT | 0x01),
if (g_get_tag_and_length(&ptr, (CONTEXT | 0x02),
if (g_get_tag_and_length(&ptr, (CONTEXT | 0x03),
if (g_get_tag_and_length(&ptr, (CONTEXT | 0x01), REMAIN, &len) < 0)
if (g_get_tag_and_length(&ptr, ENUMERATED,
if (g_get_tag_and_length(&buf, CONTEXT, cur_size, &seqsize) < 0)