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/*
* Contributed to the public domain by James K. Lowden
* Tuesday October 17, 2023
*
* This stand-in for std::regex was written because the implementation provided
* by the GCC libstdc++ in GCC 11 proved too slow, where "slow" means "appears
* not to terminate". Some invocations of std::regex_search took over 5
* seconds (or minutes) and used over 1900 stack frames, and "never" returned.
* Because the same patterns and input presented no difficulty to the C standad
* library regex functions, I recast the C++ implementation in terms of
* regex(3).
*
* Unlike std::regex, this dts version supports only Posix EREs, and requires
* the input to be NUL-terminated.
*
* It is my hope and expectation to replace this implementation with the
* standard one when it is improved.
*/
#include <stdexcept>
#include <vector>
#include <regex.h>
namespace dts {
class csub_match : public regmatch_t {
const char *input;
public:
const char *first, *second;
bool matched;
explicit csub_match( const char *input = NULL)
: input(input)
, first(NULL), second(NULL), matched(false)
{
static regmatch_t empty = { -1, -1 };
regmatch_t& self(*this);
self = empty;
}
csub_match( const char input[], const regmatch_t& m )
: input(input)
{
regmatch_t& self(*this);
self = m;
matched = rm_so != -1;
first = rm_so == -1? NULL : input + rm_so;
second = rm_eo == -1? NULL : input + rm_eo;
}
int length() const { return rm_eo - rm_so; }
};
typedef std::vector<csub_match> cmatch;
class regex : public regex_t {
size_t nsubexpr;
const char *pattern;
public:
enum cflag_t { extended = REG_EXTENDED, icase = REG_ICASE };
regex( const char pattern[], int flags ) : pattern(pattern) {
nsubexpr = 1 + std::count(pattern, pattern + strlen(pattern), '(');
int erc = regcomp(this, pattern, flags);
if( erc != 0 ) {
char msg[80];
regerror(erc, this, msg, sizeof msg);
#if __cpp_exceptions
throw std::logic_error(msg);
#else
pattern = NULL;
cbl_errx("%s", msg);
#endif
}
}
~regex() { regfree(this); }
size_t size() const { return nsubexpr; }
bool ready() const { return pattern != NULL; }
private:
regex( const regex& ) {}
};
inline bool regex_search( const char input[], const char *eoinput,
cmatch& cm, regex& re ) {
if( eoinput != NULL && *eoinput != '\0' ) {
#if __cpp_exceptions
static const char msg[] = "input not NUL-terminated";
throw std::domain_error( msg );
#else
eoinput = strchr(input, '\0');
#endif
}
if( eoinput == NULL ) eoinput = strchr(input, '\0');
auto ncm = re.size();
cm.resize(ncm);
std::vector <regmatch_t> cms(ncm);
int erc = regexec( &re, input, ncm, cms.data(), 0 );
if( erc != 0 ) return false;
std::transform( cms.begin(), cms.end(), cm.begin(),
[input]( const regmatch_t& m ) {
return csub_match( input, m );
} );
return true;
}
};
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