ForwardIterator
scan_keyword(InputIterator& b, InputIterator e,
ForwardIterator kb, ForwardIterator ke,
std::ios_base::iostate& err
)
{
typedef typename std::iterator_traits<InputIterator>::value_type CharT;
size_t nkw = std::distance(kb, ke);
const unsigned char doesnt_match = '\0';
const unsigned char might_match = '\1';
const unsigned char does_match = '\2';
unsigned char statbuf[100];
unsigned char* status = statbuf;
// Change free by free_aux to avoid
// Error: Could not find a match for boost::interprocess::unique_ptr<unsigned char, void(*)(void*)>::unique_ptr(int, extern "C" void(void*))
unique_ptr<unsigned char, void(*)(void*)> stat_hold(0, free_aux);
if (nkw > sizeof(statbuf))
{
status = (unsigned char*)malloc(nkw);
if (status == 0)
throw_exception(std::bad_alloc());
stat_hold.reset(status);
}
size_t n_might_match = nkw; // At this point, any keyword might match
size_t n_does_match = 0; // but none of them definitely do
// Initialize all statuses to might_match, except for "" keywords are does_match
unsigned char* st = status;
for (ForwardIterator ky = kb; ky != ke; ++ky, ++st)
{
if (!ky->empty())
*st = might_match;
else
{
*st = does_match;
--n_might_match;
++n_does_match;
}
}
// While there might be a match, test keywords against the next CharT
for (size_t indx = 0; b != e && n_might_match > 0; ++indx)
{
// Peek at the next CharT but don't consume it
CharT c = *b;
bool consume = false;
// For each keyword which might match, see if the indx character is c
// If a match if found, consume c
// If a match is found, and that is the last character in the keyword,
// then that keyword matches.
// If the keyword doesn't match this character, then change the keyword
// to doesn't match
st = status;
for (ForwardIterator ky = kb; ky != ke; ++ky, ++st)
{
if (*st == might_match)
{
CharT kc = (*ky)[indx];
if (c == kc)
{
consume = true;
if (ky->size() == indx+1)
{
*st = does_match;
--n_might_match;
++n_does_match;
}
}
else
{
*st = doesnt_match;
--n_might_match;
}
}
}
// consume if we matched a character
if (consume)
{
++b;
// If we consumed a character and there might be a matched keyword that
// was marked matched on a previous iteration, then such keywords
// which are now marked as not matching.
if (n_might_match + n_does_match > 1)
{
st = status;
for (ForwardIterator ky = kb; ky != ke; ++ky, ++st)
{
if (*st == does_match && ky->size() != indx+1)
{
*st = doesnt_match;
--n_does_match;
}
}
}
}
}
// We've exited the loop because we hit eof and/or we have no more "might matches".
if (b == e)
err |= std::ios_base::eofbit;
// Return the first matching result
for (st = status; kb != ke; ++kb, ++st)
if (*st == does_match)
break;
if (kb == ke)
err |= std::ios_base::failbit;
return kb;
}
