Aegisub/libaegisub/lua/modules/re.cpp

// Copyright (c) 2014, Thomas Goyne <plorkyeran@aegisub.org>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
// Aegisub Project http://www.aegisub.org/

#include "libaegisub/lua/ffi.h"
#include "libaegisub/make_unique.h"

#include <boost/regex/icu.hpp>

using boost::u32regex;
namespace {
// A cmatch with a match range attached to it so that we can return a pointer to
// an int pair without an extra heap allocation each time (LuaJIT can't compile
// ffi calls which return aggregates by value)
struct agi_re_match {
	boost::cmatch m;
	int range[2];
};

struct agi_re_flag {
	const char *name;
	int value;
};
}

namespace agi {
	AGI_DEFINE_TYPE_NAME(u32regex);
	AGI_DEFINE_TYPE_NAME(agi_re_match);
	AGI_DEFINE_TYPE_NAME(agi_re_flag);
}

namespace {
using match = agi_re_match;
bool search(u32regex& re, const char *str, size_t len, int start, boost::cmatch& result) {
	return u32regex_search(str + start, str + len, result, re,
		start > 0 ? boost::match_prev_avail | boost::match_not_bob : boost::match_default);
}

match *regex_match(u32regex& re, const char *str, size_t len, int start) {
	auto result = agi::make_unique<match>();
	if (!search(re, str, len, start, result->m))
		return nullptr;
	return result.release();
}

int *regex_get_match(match& match, size_t idx) {
	if (idx > match.m.size() || !match.m[idx].matched)
		return nullptr;
	match.range[0] = std::distance(match.m.prefix().first, match.m[idx].first + 1);
	match.range[1] = std::distance(match.m.prefix().first, match.m[idx].second);
	return match.range;
}

int *regex_search(u32regex& re, const char *str, size_t len, size_t start) {
	boost::cmatch result;
	if (!search(re, str, len, start, result))
		return nullptr;

	auto ret = static_cast<int *>(malloc(sizeof(int) * 2));
	ret[0] = start + result.position() + 1;
	ret[1] = start + result.position() + result.length();
	return ret;
}

char *regex_replace(u32regex& re, const char *replacement, const char *str, size_t len, int max_count) {
	// Can't just use regex_replace here since it can only do one or infinite replacements
	auto match = boost::u32regex_iterator<const char *>(str, str + len, re);
	auto end_it = boost::u32regex_iterator<const char *>();

	auto suffix = str;

	std::string ret;
	auto out = back_inserter(ret);
	while (match != end_it && max_count > 0) {
		copy(suffix, match->prefix().second, out);
		match->format(out, replacement);
		suffix = match->suffix().first;
		++match;
		--max_count;
	}

	ret += suffix;
	return agi::lua::strndup(ret);
}

u32regex *regex_compile(const char *pattern, int flags, char **err) {
	auto re = agi::make_unique<u32regex>();
	try {
		*re = boost::make_u32regex(pattern, boost::u32regex::perl | flags);
		return re.release();
	}
	catch (std::exception const& e) {
		*err = strdup(e.what());
		return nullptr;
	}
}

void regex_free(u32regex *re) { delete re; }
void match_free(match *m) { delete m; }

const agi_re_flag *get_regex_flags() {
	static const agi_re_flag flags[] = {
		{"ICASE", boost::u32regex::icase},
		{"NOSUB", boost::u32regex::nosubs},
		{"COLLATE", boost::u32regex::collate},
		{"NEWLINE_ALT", boost::u32regex::newline_alt},
		{"NO_MOD_M", boost::u32regex::no_mod_m},
		{"NO_MOD_S", boost::u32regex::no_mod_s},
		{"MOD_S", boost::u32regex::mod_s},
		{"MOD_X", boost::u32regex::mod_x},
		{"NO_EMPTY_SUBEXPRESSIONS", boost::u32regex::no_empty_expressions},
		{nullptr, 0}
	};
	return flags;
}
}

extern "C" int luaopen_re_impl(lua_State *L) {
	agi::lua::register_lib_table(L, {"agi_re_match", "u32regex"},
		"search", regex_search,
		"match", regex_match,
		"get_match", regex_get_match,
		"replace", regex_replace,
		"compile", regex_compile,
		"get_flags", get_regex_flags,
		"match_free", match_free,
		"regex_free", regex_free);
	return 1;
}