On Thu, Jun 02, 2005 at 03:34:17PM -0400, Raymond Hettinger wrote:
The times two operation also occurs twice in nearby code. Are those
also incorrect?
I believe they're correct.
EXPN: The regex engine refers to both 'groups', where group #N means
the corresponding group in the pattern, and 'marks', which is a table
of indexes into the string; group #0 - mark 0 and 1, group #1 - mark
2 and 3, etc. The compiler was storing the mark value, but then the
code for the GROUPREF_EXISTS opcode was doubling it, converting group
to mark:
case SRE_OP_GROUPREF_EXISTS:
TRACE((|%p|%p|GROUPREF_EXISTS %d\n, ctx-pattern,
ctx-ptr, ctx-pattern[0]));
/* GROUPREF_EXISTS group skip codeyes JUMP codeno ... */
i = ctx-pattern[0];
{
int groupref = i+i;
if (groupref = state-lastmark) {
ctx-pattern += ctx-pattern[1];
break;
} else {
...
}
The two other uses of *2 are for the MARK opcode, which stores the
current position in the string in the corresponding entry in the
table; it really does want the mark number, so the doubling is
correct.
The 'groupref = i+i' in the above code is a bit odd -- why not write 2*i? I
thought it might be a typo for i+1, but that wouldn't make sense
either; eventually I decided this was just a stylistic thing.
--amOnly the effbot knows for surek
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