// SPDX-License-Identifier: 0BSD
// Reduced from https://git.sr.ht/~nabijaczleweli/voreutils/tree/5a9f9f296607494cf3fed7b83d9cef6945e57d28/item/cmd/wc.cpp
// https://101010.pl/@nabijaczleweli/115774904189342717
//   c++            -g -O3 -Wall -Wextra -fPIC -std=c++20 -fno-exceptions -fno-rtti wcl.cpp -o wcl.clang.memchr
//   c++ -DSTDCOUNT -g -O3 -Wall -Wextra -fPIC -std=c++20 -fno-exceptions -fno-rtti wcl.cpp -o wcl.clang.count
//   g++            -g -O3 -Wall -Wextra -fPIC -std=c++20 -fno-exceptions -fno-rtti wcl.cpp -o wcl.gcc.memchr
//   g++ -DSTDCOUNT -g -O3 -Wall -Wextra -fPIC -std=c++20 -fno-exceptions -fno-rtti wcl.cpp -o wcl.gcc.count
// ./wcl.gcc.memchr r2 ran
//   1.01 ± 0.06 times faster than ./wcl.clang.memchr r2
//   2.48 ± 0.14 times faster than ./wcl.clang.count r2
//   2.51 ± 0.12 times faster than ./wcl.gcc.count r2

#include <algorithm>
#include <cstdint>
#include <cstdio>
#include <cstring>
#include <errno.h>
#include <fcntl.h>
#include <initializer_list>
#include <inttypes.h>
#include <optional>
#include <unistd.h>
#include <utility>

struct record {
	std::uint64_t bytes, newlines;
};

int main(int, const char * const * argv) {
	bool err{};
	auto dump = [&](const record & data, const char * file) {
		auto first = true;
		for(auto && r : std::initializer_list<std::uint64_t>{data.newlines, data.bytes}) {
			if(!std::exchange(first, false))
				std::fputc(' ', stdout);
			std::fprintf(stdout, "%6" PRIu64 "", r);
		}

		if(file)
			std::fputc(' ', stdout), std::fputs(file, stdout);
		std::fputc('\n', stdout);
	};
	auto process = [&](const char * file) {
		int fd = open(file, O_RDONLY | O_CLOEXEC);
		if(fd == -1) {
			std::fprintf(stderr, "%s: %s: %s\n", argv[0], file, std::strerror(errno)), err = true;
			return;
		}
		posix_fadvise(fd, 0, 0, POSIX_FADV_SEQUENTIAL);

		record acc{};

		char buf[64 * 1024];
		for(ssize_t rd;;) {
			while((rd = read(fd, buf, sizeof(buf))) == -1 && errno == EINTR)
				;
			if(rd == -1) {
				std::fprintf(stderr, "%s: %s: %s\n", argv[0], file, std::strerror(errno)), err = true;
				return;
			}
			if(!rd)
				break;

			if(true) {
#if STDCOUNT
				acc.newlines += std::count(buf, buf + rd, '\n');
#else
				auto newitr = buf;
				auto len    = rd;
				char * itr;
				// This is still suboptimal: a while(itr != end && *itr == '\n') ++acc; will be better if the data has consecutive needles
				while(len && (newitr = static_cast<char *>(std::memchr(itr = newitr, '\n', len)))) {
					++acc.newlines;
					++newitr;
					len -= newitr - itr;
				}
#endif
			}

			acc.bytes += rd;
		}

		dump(acc, file);
	};

	process(argv[1]);
	return err;
}