Add strverscmp(3).

libc/Makefile

@@ -122,6 +122,7 @@ string/strspn.o \
 string/strstr.o \
 string/strtok.o \
 string/strtok_r.o \
+string/strverscmp.o \
 string/strxfrm.o \
 strtod.o \
 strtof.o \

libc/include/string.h

@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
 
     This file is part of the Sortix C Library.
 
@@ -22,8 +22,8 @@
 
 *******************************************************************************/
 
-#ifndef _STRING_H
-#define _STRING_H 1
+#ifndef INCLUDE_STRING_H
+#define INCLUDE_STRING_H
 
 #include <features.h>
 #include <strings.h>
@@ -61,6 +61,7 @@ size_t strspn(const char*, const char*);
 char* strstr(const char*, const char*);
 char* strtok(char* __restrict, const char* __restrict);
 char* strtok_r(char* __restrict, const char* __restrict, char** __restrict);
+int strverscmp(const char*, const char*);
 size_t strxfrm(char* __restrict, const char* __restrict, size_t);
 
 /* TODO: These are not implemented in sortix libc yet. */

libc/string/strverscmp.cpp

@@ -0,0 +1,115 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    string/strverscmp.cpp
+    Compares two version strings.
+
+*******************************************************************************/
+
+#include <string.h>
+
+static bool is_number(char c)
+{
+	return '0' <= c && c <= '9';
+}
+
+static int to_number(char c)
+{
+	return c - '0';
+}
+
+extern "C" int strverscmp(const char* a, const char* b)
+{
+	for ( size_t i = 0; true; i++ )
+	{
+		// Be a regular strcmp if the strings are equal.
+		if ( a[i] == '\0' && b[i] == '\0' )
+			return 0;
+		if ( a[i] == b[i] )
+			continue;
+
+		// Be a regular strcmp if no digits are involed when they differ.
+		bool version_string = is_number(a[i]) && is_number(b[i]);
+		if ( !version_string && a[i] < b[i] )
+			return -1;
+		if ( !version_string && a[i] > b[i] )
+			return 1;
+
+		// Because the number of leading zeroes matter, we have to find the
+		// entire numeric block we are currently within. We know the strings are
+		// equal until i, so we can simply find the number of shared digits by
+		// looking in the first string.
+		size_t digits_start = i;
+		while ( digits_start && is_number(a[digits_start-1]) )
+			digits_start--;
+		size_t shared_digits = i - digits_start;
+
+		// Find the number of shared leading zeroes.
+		size_t shared_zeroes = 0;
+		while ( shared_zeroes < shared_digits &&
+		        to_number(a[digits_start + shared_zeroes]) == 0 )
+			shared_zeroes++;
+
+		// Try to expand the leading zeroes amount into a.
+		size_t a_zeroes = shared_zeroes;
+		while ( is_number(a[digits_start + a_zeroes]) == 0 )
+			a_zeroes++;
+
+		// Try to expand the leading zeroes amount into b.
+		size_t b_zeroes = shared_zeroes;
+		while ( is_number(b[digits_start + b_zeroes]) == 0 )
+			b_zeroes++;
+
+		// We treat strings with leading zeroes as if they have a decimal point
+		// in front of them, so strings with more zeroes sort lower.
+		if ( a_zeroes > b_zeroes )
+			return -1;
+		if ( b_zeroes > a_zeroes )
+			return 1;
+
+		// Find the number of consecutive digits in a where the strings differ.
+		size_t a_digits = a_zeroes;
+		while ( is_number(a[digits_start + a_digits]) )
+			a_digits++;
+
+		// Find the number of consecutive digits in b where the strings differ.
+		size_t b_digits = b_zeroes;
+		while ( is_number(b[digits_start + b_digits]) )
+			b_digits++;
+
+		// We know the strings have the same amount of leading zeroes, so we
+		// so if a a block is longer than the other, then the value must be
+		// longer as well.
+		if ( a_digits < b_digits )
+			return -1;
+		if ( b_digits < a_digits )
+			return 1;
+
+		// Finally run through the strings from where they differ and sort them
+		// numerically. We know this terminates because the strings differ. The
+		// strings have the same amount of digits, so comparing them is easy.
+		for ( size_t n = shared_zeroes; true; n++ )
+		{
+			if ( a[digits_start + n] < b[digits_start + n] )
+				return -1;
+			if ( b[digits_start + n] < a[digits_start + n] )
+				return 1;
+		}
+	}
+}