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/*
* Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The names of the authors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "readlink.h"
#include <string>
#include <errno.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <unistd.h>
/**
* This differs from realpath(3) mainly in its behavior when a path element does not exist or can
* not be searched. realpath(3) treats that as an error and gives up, but we have Java-compatible
* behavior where we just assume the path element was not a symbolic link. This leads to a textual
* treatment of ".." from that point in the path, which may actually lead us back to a path we
* can resolve (as in "/tmp/does-not-exist/../blah.txt" which would be an error for realpath(3)
* but "/tmp/blah.txt" under the traditional Java interpretation).
*
* This implementation also removes all the fixed-length buffers of the C original.
*/
bool canonicalize_path(const char* path, std::string& resolved) {
// 'path' must be an absolute path.
if (path[0] != '/') {
errno = EINVAL;
return false;
}
resolved = "/";
if (path[1] == '\0') {
return true;
}
// Iterate over path components in 'left'.
int symlinkCount = 0;
std::string left(path + 1);
while (!left.empty()) {
// Extract the next path component.
size_t nextSlash = left.find('/');
std::string nextPathComponent = left.substr(0, nextSlash);
if (nextSlash != std::string::npos) {
left.erase(0, nextSlash + 1);
} else {
left.clear();
}
if (nextPathComponent.empty()) {
continue;
} else if (nextPathComponent == ".") {
continue;
} else if (nextPathComponent == "..") {
// Strip the last path component except when we have single "/".
if (resolved.size() > 1) {
resolved.erase(resolved.rfind('/'));
}
continue;
}
// Append the next path component.
if (resolved[resolved.size() - 1] != '/') {
resolved += '/';
}
resolved += nextPathComponent;
// See if we've got a symbolic link, and resolve it if so.
struct stat sb;
if (lstat(resolved.c_str(), &sb) == 0 && S_ISLNK(sb.st_mode)) {
if (symlinkCount++ > MAXSYMLINKS) {
errno = ELOOP;
return false;
}
std::string symlink;
if (!readlink(resolved.c_str(), symlink)) {
return false;
}
if (symlink[0] == '/') {
// The symbolic link is absolute, so we need to start from scratch.
resolved = "/";
} else if (resolved.size() > 1) {
// The symbolic link is relative, so we just lose the last path component (which
// was the link).
resolved.erase(resolved.rfind('/'));
}
if (!left.empty()) {
const char* maybeSlash = (symlink[symlink.size() - 1] != '/') ? "/" : "";
left = symlink + maybeSlash + left;
} else {
left = symlink;
}
}
}
// Remove trailing slash except when the resolved pathname is a single "/".
if (resolved.size() > 1 && resolved[resolved.size() - 1] == '/') {
resolved.erase(resolved.size() - 1, 1);
}
return true;
}
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