simsong
commented
3 years ago Here is the flex-generated NFA:
#define YY_NUM_RULES 3
#define YY_END_OF_BUFFER 4
/* This struct is not used in this scanner,
but its presence is necessary. */
struct yy_trans_info
{
flex_int32_t yy_verify;
flex_int32_t yy_nxt;
};
static yyconst flex_int16_t yy_accept[44] =
{ 0,
0, 0, 4, 2, 2, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 1, 0, 0, 0, 0,
0, 1, 0
} ;
static yyconst flex_int32_t yy_ec[256] =
{ 0,
1, 1, 1, 1, 1, 1, 1, 1, 1, 2,
1, 1, 3, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 4, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 5, 5, 5,
5, 5, 5, 5, 5, 5, 5, 1, 1, 1,
1, 1, 1, 1, 5, 5, 5, 5, 5, 5,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 5, 5, 5, 5,
5, 5, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
1, 1, 1, 1, 1
} ;
static yyconst flex_int32_t yy_meta[6] =
{ 0,
1, 2, 1, 1, 3
} ;
static yyconst flex_int16_t yy_base[70] =
{ 0,
75, 74, 78, 81, 0, 0, 4, 0, 0, 0,
0, 8, 12, 0, 0, 0, 0, 16, 20, 0,
0, 0, 0, 24, 28, 0, 0, 0, 0, 32,
36, 0, 0, 0, 0, 40, 44, 0, 0, 0,
0, 0, 81, 49, 74, 74, 72, 71, 71, 70,
68, 67, 67, 66, 64, 63, 63, 62, 60, 59,
59, 58, 56, 55, 55, 54, 52, 51, 51
} ;
static yyconst flex_int16_t yy_def[70] =
{ 0,
44, 44, 43, 43, 45, 43, 43, 46, 47, 48,
49, 43, 43, 50, 51, 52, 53, 43, 43, 54,
55, 56, 57, 43, 43, 58, 59, 60, 61, 43,
43, 62, 63, 64, 65, 43, 43, 66, 67, 68,
69, 36, 0, 43, 43, 43, 43, 43, 43, 43,
43, 43, 43, 43, 43, 43, 43, 43, 43, 43,
43, 43, 43, 43, 43, 43, 43, 43, 43
} ;
static yyconst flex_int16_t yy_nxt[87] =
{ 0,
43, 7, 8, 7, 9, 10, 11, 10, 9, 13,
14, 13, 15, 16, 17, 16, 15, 19, 20, 19,
21, 22, 23, 22, 21, 25, 26, 25, 27, 28,
29, 28, 27, 31, 32, 31, 33, 34, 35, 34,
33, 37, 38, 37, 39, 40, 41, 40, 39, 4,
4, 4, 40, 39, 42, 37, 34, 33, 36, 31,
28, 27, 30, 25, 22, 21, 24, 19, 16, 15,
18, 13, 10, 9, 12, 7, 6, 43, 5, 5,
3, 43, 43, 43, 43, 43
} ;
static yyconst flex_int16_t yy_chk[87] =
{ 0,
0, 6, 6, 6, 6, 7, 7, 7, 7, 12,
12, 12, 12, 13, 13, 13, 13, 18, 18, 18,
18, 19, 19, 19, 19, 24, 24, 24, 24, 25,
25, 25, 25, 30, 30, 30, 30, 31, 31, 31,
31, 36, 36, 36, 36, 37, 37, 37, 37, 44,
44, 44, 69, 68, 67, 66, 65, 64, 63, 62,
61, 60, 59, 58, 57, 56, 55, 54, 53, 52,
51, 50, 49, 48, 47, 46, 45, 3, 2, 1,
43, 43, 43, 43, 43, 43
} ;That's pretty small, and I think that it's super-efficient. My feeling is to leave this as it is, as it works.
jonstewart
scan_base16.flex is a good candidate for a hard-coded implementation of a bit-parallel automaton. The matching alphabet is relatively small and repeated, and the number of states should be small. Such an implementation can likely identify and decode hex data faster than a general-purpose regexp library, or Flex.
This should only be done if timing data indicates that scan_base16.flex has significant runtime overhead compared to other scanners. It could happen post-2.0.