130 lines
4.4 KiB
C
130 lines
4.4 KiB
C
/****************************************************************************
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* libs/libc/string/lib_strverscmp.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <ctype.h>
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#include <string.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: strverscmp
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*
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* Description:
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* Often one has files jan1, jan2, ..., jan9, jan10, ... and it feels
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* wrong when ls orders them jan1, jan10, ..., jan2, ..., jan9. In
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* order to rectify this, GNU introduced the -v option to ls, which is
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* implemented using versionsort, which again uses strverscmp().
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*
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* Thus, the task of strverscmp() is to compare two strings and find the
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* "right" order, while strcmp finds only the lexicographic order. This
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* function does not use the locale category LC_COLLATE, so is meant
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* mostly for situations where the strings are expected to be in ASCII.
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*
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* What this function does is the following. If both strings are
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* equal, return 0. Otherwise, find the position between two bytes with
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* the property that before it both strings are equal, while directly
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* after it there is a difference. Find the largest consecutive digit
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* strings containing (or starting at, or ending at) this position.
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* If one or both of these is empty, then return what strcmp would have
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* returned (numerical ordering of byte values). Otherwise, compare both
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* digit strings numerically, where digit strings with one or more
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* leading zeros are interpreted as if they have a decimal point
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* in front (so that in particular digit strings with more leading zeros
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* come before digit strings with fewer leading zeros). Thus, the
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* ordering is 000, 00, 01, 010, 09, 0, 1, 9, 10.
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*
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* Returned Value:
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* The strverscmp() function returns an integer less than, equal to, or
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* greater than zero if s1 is found, respectively, to be earlier than,
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* equal to, or later than s2.
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*
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****************************************************************************/
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int strverscmp(FAR const char *s1, FAR const char *s2)
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{
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FAR const unsigned char *str1 = (FAR const void *)s1;
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FAR const unsigned char *str2 = (FAR const void *)s2;
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size_t i;
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size_t j;
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size_t dp;
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int z = 1;
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/* Find maximal matching prefix and track its maximal digit
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* suffix and whether those digits are all zeros.
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*/
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for (dp = i = 0; str1[i] == str2[i]; i++)
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{
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int c = str1[i];
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if (c == 0)
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{
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return 0;
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}
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if (!isdigit(c))
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{
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dp = i + 1;
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z = 1;
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}
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else if (c != '0')
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{
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z = 0;
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}
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}
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if (str1[dp] != '0' && str2[dp] != '0')
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{
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/* If we're not looking at a digit sequence that began
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* with a zero, longest digit string is greater.
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*/
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for (j = i; isdigit(str1[j]); j++)
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{
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if (!isdigit(str2[j]))
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{
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return 1;
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}
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}
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if (isdigit(str2[j]))
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{
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return -1;
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}
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}
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else if (z && dp < i && (isdigit(str1[i]) || isdigit(str2[i])))
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{
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/* Otherwise, if common prefix of digit sequence is
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* all zeros, digits order less than non-digits.
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*/
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return (unsigned char)(str1[i] - '0') -
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(unsigned char)(str2[i] - '0');
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}
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return str1[i] - str2[i];
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}
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