1 /*

     2 * Copyright (c) 1997-2009 Nokia Corporation and/or its subsidiary(-ies).

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

     5 * under the terms of "Eclipse Public License v1.0"

     6 * which accompanies this distribution, and is available

     7 * at the URL "http://www.eclipse.org/legal/epl-v10.html".

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description:

    15 * FUNCTION

    16 * <<strncmp>>---character string compare

    17 * INDEX

    18 * strncmp

    19 * ANSI_SYNOPSIS

    20 * #include <string.h>

    21 * int strncmp(const char *<[a]>, const char * <[b]>, size_t <[length]>);

    22 * TRAD_SYNOPSIS

    23 * #include <string.h>

    24 * int strncmp(<[a]>, <[b]>, <[length]>)

    25 * char *<[a]>;

    26 * char *<[b]>;

    27 * size_t <[length]>

    28 * <<strncmp>> compares up to <[length]> characters

    29 * from the string at <[a]> to the string at <[b]>.

    30 * RETURNS

    31 * If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,

    32 * <<strncmp>> returns a number greater than zero.  If the two

    33 * strings are equivalent, <<strncmp>> returns zero.  If <<*<[a]>>>

    34 * sorts lexicographically before <<*<[b]>>>, <<strncmp>> returns a

    35 * number less than zero.

    36 * PORTABILITY

    37 * <<strncmp>> is ANSI C.

    38 * <<strncmp>> requires no supporting OS subroutines.

    39 * QUICKREF

    40 * strncmp ansi pure

    41 * 

    42 *

    43 */

    44 

    45 

    46 

    47 #include <string.h>

    48 

    49 /**

    50 Compare some characters of two strings.

    51 Compares the first num characters of string1 to the first num characters of string2.

    52 The comparison is performed character by character. 

    53 If a character that is not equal in both strings is found the function ends 

    54 and returns a value that determines which of them was greater.

    55 @return a value indicating the lexicographical relation between the strings.

    56 @param s1 Null-terminated string to compare 

    57 @param s2 Null-terminated string to compare. 

    58 @param n Maximum number of characters to compare.

    59 */

    60 EXPORT_C int 

    61 strncmp (const char *s1, const char *s2, size_t n)

    62 {

    63 	const unsigned char* p1 = (const unsigned char*)s1;

    64 	const unsigned char* p2 = (const unsigned char*)s2;

    65 

    66 	if (n == 0)

    67 		return 0;

    68 

    69 	for (;;)

    70 	{

    71 		int c1 = *p1++;

    72 		int d = c1 - *p2++;

    73 		if (d != 0)

    74 			return d;

    75 		if (c1 == 0)

    76 			return d;

    77 		if (--n == 0)

    78 			return d;

    79 	}

    80 }