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/**************************************************************************/
/* */
/* The Why platform for program certification */
/* Copyright (C) 2002-2008 */
/* Romain BARDOU */
/* Jean-Franois COUCHOT */
/* Mehdi DOGGUY */
/* Jean-Christophe FILLITRE */
/* Thierry HUBERT */
/* Claude MARCH */
/* Yannick MOY */
/* Christine PAULIN */
/* Yann RGIS-GIANAS */
/* Nicolas ROUSSET */
/* Xavier URBAIN */
/* */
/* This software is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU General Public */
/* License version 2, as published by the Free Software Foundation. */
/* */
/* This software 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 General Public License version 2 for more details */
/* (enclosed in the file GPL). */
/* */
/**************************************************************************/
/*@ predicate is_string(char *s) {
\exists int n; \valid_range(s,0,n) && s[n] == 0
} */
/*@ logic int length(char *s) reads s[..] */
/*@ axiom length_non_negative :
\forall char *s; is_string(s) => 0 <= length(s) */
/*@ axiom length_not_zero :
\forall char *s; is_string(s) =>
\forall int i; 0 <= i < length(s) => s[i] != 0 */
/*@ axiom length_zero :
\forall char *s; is_string(s) => s[length(s)] == 0 */
/*@ axiom is_string_valid :
\forall char *s; is_string(s) =>
\forall int i; 0 <= i <= length(s) => \valid(s+i) */
/*@ requires is_string(s)
ensures \valid(s+\result) && s[\result] == 0
// && \forall int i; 0 <= i < \result => s[i] != 0
*/
int strlen(char * s) {
int len = 0;
/*@ invariant \valid(s + len) && len <= length(s)
variant length(s) - len */
while (s[len] != 0) len++;
return len;
}
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