vfs_lookup.cpp

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/* Copyright (c) 2013 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * look up directories/files by traversing path components.
 */

#include "precompiled.h"
#include "lib/file/vfs/vfs_lookup.h"

#include "lib/external_libraries/suppress_boost_warnings.h"

#include "lib/sysdep/filesystem.h"
#include "lib/file/file.h"
#include "lib/file/vfs/vfs.h"   // error codes
#include "lib/file/vfs/vfs_tree.h"
#include "lib/file/vfs/vfs_populate.h"

#include "lib/timer.h"


static Status CreateDirectory(const OsPath& path)
{
    {
        const mode_t mode = S_IRWXU; // 0700 as prescribed by XDG basedir
        const int ret = wmkdir(path, mode);
        if(ret == 0)    // success
            return INFO::OK;
    }

    // failed because the directory already exists. this can happen
    // when the first vfs_Lookup has addMissingDirectories &&
    // !createMissingDirectories, and the directory is subsequently
    // created. return 'success' to attach the existing directory..
    if(errno == EEXIST)
    {
        // but first ensure it's really a directory (otherwise, a
        // file is "in the way" and needs to be deleted)
        struct stat s;
        const int ret = wstat(path, &s);
        ENSURE(ret == 0);   // (wmkdir said it existed)
        ENSURE(S_ISDIR(s.st_mode));
        return INFO::OK;
    }

    if (errno == EACCES)
        return ERR::FILE_ACCESS;

    // unexpected failure
    debug_printf(L"wmkdir failed with errno=%d\n", errno);
    DEBUG_WARN_ERR(ERR::LOGIC);
    WARN_RETURN(StatusFromErrno());
}


Status vfs_Lookup(const VfsPath& pathname, VfsDirectory* startDirectory, VfsDirectory*& directory, VfsFile** pfile, size_t flags)
{
    // extract and validate flags (ensure no unknown bits are set)
    const bool addMissingDirectories    = (flags & VFS_LOOKUP_ADD) != 0;
    const bool createMissingDirectories = (flags & VFS_LOOKUP_CREATE) != 0;
    const bool skipPopulate = (flags & VFS_LOOKUP_SKIP_POPULATE) != 0;
    const bool createAlways = (flags & VFS_LOOKUP_CREATE_ALWAYS) != 0;
    ENSURE((flags & ~(VFS_LOOKUP_ADD|VFS_LOOKUP_CREATE|VFS_LOOKUP_SKIP_POPULATE|VFS_LOOKUP_CREATE_ALWAYS)) == 0);

    directory = startDirectory;
    if(pfile)
        *pfile = 0;

    if(!skipPopulate)
        RETURN_STATUS_IF_ERR(vfs_Populate(directory));

    // early-out for pathname == "" when mounting into VFS root
    if(pathname.empty())    // (prevent iterator error in loop end condition)
    {
        if(pfile)   // preserve a guarantee that if pfile then we either return an error or set *pfile
            return ERR::VFS_FILE_NOT_FOUND;
        else
            return INFO::OK;
    }

    // for each directory component:
    size_t pos = 0; // (needed outside of loop)
    for(;;)
    {
        const size_t nextSlash = pathname.string().find_first_of('/', pos);
        if(nextSlash == VfsPath::String::npos)
            break;
        const VfsPath subdirectoryName = pathname.string().substr(pos, nextSlash-pos);
        pos = nextSlash+1;

        VfsDirectory* subdirectory = directory->GetSubdirectory(subdirectoryName);
        if(!subdirectory)
        {
            if(addMissingDirectories)
                subdirectory = directory->AddSubdirectory(subdirectoryName);
            else
                return ERR::VFS_DIR_NOT_FOUND;  // NOWARN
        }

        if(createMissingDirectories && (!subdirectory->AssociatedDirectory()
             || (createAlways && (subdirectory->AssociatedDirectory()->Flags() & VFS_MOUNT_REPLACEABLE) != 0)))
        {
            OsPath currentPath;
            if(directory->AssociatedDirectory())    // (is NULL when mounting into root)
                currentPath = directory->AssociatedDirectory()->Path();
            currentPath = currentPath / subdirectoryName;

            RETURN_STATUS_IF_ERR(CreateDirectory(currentPath));

            PRealDirectory realDirectory(new RealDirectory(currentPath, 0, 0));
            RETURN_STATUS_IF_ERR(vfs_Attach(subdirectory, realDirectory));
        }

        if(!skipPopulate)
            RETURN_STATUS_IF_ERR(vfs_Populate(subdirectory));

        directory = subdirectory;
    }

    if(pfile)
    {
        ENSURE(!pathname.IsDirectory());
        const VfsPath filename = pathname.string().substr(pos);
        *pfile = directory->GetFile(filename);
        if(!*pfile)
            return ERR::VFS_FILE_NOT_FOUND; // NOWARN
    }

    return INFO::OK;
}