strnatcmp.hpp

// by https://github.com/Amerge/natsort
// C와 구별하기 위한 C++ 용 header 파일로 만들고 싶으면 *.h 대신에 *.hpp 로 씀
// 컴파일러가 아닌 사람들의 구별 목적임.

/* -*- mode: c; c-file-style: "k&r" -*-
  strnatcmp.c -- Perform 'natural order' comparisons of strings in C.
  Copyright (C) 2000, 2004 by Martin Pool <mbp sourcefrog net>
  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.
  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:
  1. The origin of this software must not be misrepresented; you must not
	 claim that you wrote the original software. If you use this software
	 in a product, an acknowledgment in the product documentation would be
	 appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
	 misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

/***********************************************************************
 * Now let's make some changes:
 *
 * 1. std::string support
 * 2. usable with std::sort and std::vectors
 *
 * ********************************************************************/

#ifndef __STRNATCMP_HPP
#define __STRNATCMP_HPP

#include <cstddef>	/* size_t */
#include <cctype>
#include <string>

typedef char nat_char;

int strnatcmp(nat_char const* a, nat_char const* b);
int strnatcasecmp(nat_char const* a, nat_char const* b);


static inline int nat_isdigit(nat_char a) {
	return isdigit((unsigned char)a);
}


static inline int nat_isspace(nat_char a) {
	return isspace((unsigned char)a);
}


static inline nat_char nat_toupper(nat_char a) {
	return toupper((unsigned char)a);
}


static int compare_right(nat_char const* a, nat_char const* b) {
	int bias = 0;

	/* The longest run of digits wins.  That aside, the greatest
   value wins, but we can't know that it will until we've scanned
   both numbers to know that they have the same magnitude, so we
   remember it in BIAS. */
	for (;; a++, b++) {
		if (!nat_isdigit(*a) && !nat_isdigit(*b))
			return bias;
		if (!nat_isdigit(*a))
			return -1;
		if (!nat_isdigit(*b))
			return +1;
		if (*a < *b) {
			if (!bias)
				bias = -1;
		}
		else if (*a > *b) {
			if (!bias)
				bias = +1;
		}
		else if (!*a && !*b)
			return bias;
	}

	return 0;
}


static int compare_left(nat_char const* a, nat_char const* b) {
	/* Compare two left-aligned numbers: the first to have a
	   different value wins. */
	for (;; a++, b++) {
		if (!nat_isdigit(*a) && !nat_isdigit(*b))
			return 0;
		if (!nat_isdigit(*a))
			return -1;
		if (!nat_isdigit(*b))
			return +1;
		if (*a < *b)
			return -1;
		if (*a > *b)
			return +1;
	}

	return 0;
}


static int strnatcmp0(nat_char const* a, nat_char const* b, int fold_case) {
	int ai, bi;
	nat_char ca, cb;
	int fractional, result;

	ai = bi = 0;
	while (1) {
		ca = a[ai]; cb = b[bi];

		/* skip over leading spaces or zeros */
		while (nat_isspace(ca))
			ca = a[++ai];

		while (nat_isspace(cb))
			cb = b[++bi];

		/* process run of digits */
		if (nat_isdigit(ca) && nat_isdigit(cb)) {
			fractional = (ca == '0' || cb == '0');

			if (fractional) {
				if ((result = compare_left(a + ai, b + bi)) != 0)
					return result;
			}
			else {
				if ((result = compare_right(a + ai, b + bi)) != 0)
					return result;
			}
		}

		if (!ca && !cb) {
			/* The strings compare the same.  Perhaps the caller
				   will want to call strcmp to break the tie. */
			return 0;
		}

		if (fold_case) {
			ca = nat_toupper(ca);
			cb = nat_toupper(cb);
		}

		if (ca < cb)
			return -1;

		if (ca > cb)
			return +1;

		++ai; ++bi;
	}
}

/*The following doesn't consider case of string*/
int strnatcmp(nat_char const* a, nat_char const* b) {
	return strnatcmp0(a, b, 0);
}


/* Compare, recognizing numeric string and ignoring case.
 * This one is the general case where lower-case and upper-
 * case are considered as same.
 *  */
int strnatcasecmp(nat_char const* a, nat_char const* b) {
	return strnatcmp0(a, b, 1);
}

//You can use this function with std::sort and vector
bool compareNat(const std::string& a, const std::string& b) {
	if (strnatcasecmp(a.c_str(), b.c_str()) == -1) return true;
	else return false;
}

//You can use this function with qsort
int compareNatq(const void* a, const void* b) {
	char const* pa = *(char const**)a, * pb = *(char const**)b;
	return strnatcasecmp(pa, pb);
}


#endif