Use the configuration slot to test GRF static safety

[openttd/fttd.git] / src / newgrf_config.cpp

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD 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 for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file newgrf_config.cpp Finding NewGRFs and configuring them. */

#include "stdafx.h"
#include "debug.h"
#include "3rdparty/md5/md5.h"
#include "newgrf.h"
#include "network/network_func.h"
#include "gfx_func.h"
#include "newgrf_text.h"
#include "window_func.h"
#include "progress.h"
#include "video/video_driver.hpp"
#include "strings_func.h"
#include "textfile.h"

#include "fileio_func.h"
#include "fios.h"


/**
 * Create a new GRFConfig.
 * @param filename Set the filename of this GRFConfig to filename. The argument
 *   is copied so the original string isn't needed after the constructor.
 */
GRFConfig::GRFConfig(const char *filename) :
        name(new GRFTextMap),
        info(new GRFTextMap),
        url(new GRFTextMap),
        num_valid_params(lengthof(param))
{
        if (filename != NULL) this->filename = xstrdup(filename);
}

/**
 * Create a new GRFConfig that is a deep copy of an existing config.
 * @param config The GRFConfig object to make a copy of.
 */
GRFConfig::GRFConfig(const GRFConfig &config) :
        ZeroedMemoryAllocator(),
        ident(config.ident),
        name(config.name),
        info(config.info),
        url(config.url),
        version(config.version),
        min_loadable_version(config.min_loadable_version),
        flags(config.flags & ~(1 << GCF_COPY)),
        status(config.status),
        grf_bugs(config.grf_bugs),
        num_params(config.num_params),
        num_valid_params(config.num_valid_params),
        palette(config.palette),
        has_param_defaults(config.has_param_defaults)
{
        MemCpyT<uint8>(this->original_md5sum, config.original_md5sum, lengthof(this->original_md5sum));
        MemCpyT<uint32>(this->param, config.param, lengthof(this->param));
        if (config.filename != NULL) this->filename = xstrdup(config.filename);
        if (config.error != NULL) this->error = new GRFError(*config.error);
        for (uint i = 0; i < config.param_info.Length(); i++) {
                if (config.param_info[i] == NULL) {
                        *this->param_info.Append() = NULL;
                } else {
                        *this->param_info.Append() = new GRFParameterInfo(*config.param_info[i]);
                }
        }
}

/** Cleanup a GRFConfig object. */
GRFConfig::~GRFConfig()
{
        /* GCF_COPY as in NOT strdupped/alloced the filename */
        if (!HasBit(this->flags, GCF_COPY)) {
                free(this->filename);
                delete this->error;
        }

        for (uint i = 0; i < this->param_info.Length(); i++) delete this->param_info[i];
}

/**
 * Copy the parameter information from the \a src config.
 * @param src Source config.
 */
void GRFConfig::CopyParams(const GRFConfig &src)
{
        this->num_params = src.num_params;
        this->num_valid_params = src.num_valid_params;
        MemCpyT<uint32>(this->param, src.param, lengthof(this->param));
}

/**
 * Get the name of this grf. In case the name isn't known
 * the filename is returned.
 * @return The name of filename of this grf.
 */
const char *GRFConfig::GetName() const
{
        const char *name = this->name->get_string();
        return StrEmpty(name) ? this->filename : name;
}

/**
 * Get the grf info.
 * @return A string with a description of this grf.
 */
const char *GRFConfig::GetDescription() const
{
        return this->info->get_string();
}

/**
 * Get the grf url.
 * @return A string with an url of this grf.
 */
const char *GRFConfig::GetURL() const
{
        return this->url->get_string();
}

/** Set the default value for all parameters as specified by action14. */
void GRFConfig::SetParameterDefaults()
{
        this->num_params = 0;
        MemSetT<uint32>(this->param, 0, lengthof(this->param));

        if (!this->has_param_defaults) return;

        for (uint i = 0; i < this->param_info.Length(); i++) {
                if (this->param_info[i] == NULL) continue;
                this->param_info[i]->SetValue(this, this->param_info[i]->def_value);
        }
}

/**
 * Set the palette of this GRFConfig to something suitable.
 * That is either the setting coming from the NewGRF or
 * the globally used palette.
 */
void GRFConfig::SetSuitablePalette()
{
        PaletteType pal;
        switch (this->palette & GRFP_GRF_MASK) {
                case GRFP_GRF_DOS:     pal = PAL_DOS;      break;
                case GRFP_GRF_WINDOWS: pal = PAL_WINDOWS;  break;
                default:               pal = _settings_client.gui.newgrf_default_palette == 1 ? PAL_WINDOWS : PAL_DOS; break;
        }
        SB(this->palette, GRFP_USE_BIT, 1, pal == PAL_WINDOWS ? GRFP_USE_WINDOWS : GRFP_USE_DOS);
}

/**
 * Finalize Action 14 info after file scan is finished.
 */
void GRFConfig::FinalizeParameterInfo()
{
        for (GRFParameterInfo **info = this->param_info.Begin(); info != this->param_info.End(); ++info) {
                if (*info == NULL) continue;
                (*info)->Finalize();
        }
}

GRFConfig *_all_grfs;
GRFConfig *_grfconfig;
GRFConfig *_grfconfig_newgame;
GRFConfig *_grfconfig_static;

/**
 * Construct a new GRFError.
 * @param severity The severity of this error.
 * @param message The actual error-string.
 */
GRFError::GRFError(StringID severity, StringID message) :
        message(message),
        severity(severity)
{
}

/**
 * Create a new GRFError that is a deep copy of an existing error message.
 * @param error The GRFError object to make a copy of.
 */
GRFError::GRFError(const GRFError &error) :
        ZeroedMemoryAllocator(),
        custom_message(error.custom_message),
        data(error.data),
        message(error.message),
        severity(error.severity)
{
        if (error.custom_message != NULL) this->custom_message = xstrdup(error.custom_message);
        if (error.data           != NULL) this->data           = xstrdup(error.data);
        memcpy(this->param_value, error.param_value, sizeof(this->param_value));
}

GRFError::~GRFError()
{
        free(this->custom_message);
        free(this->data);
}

/**
 * Create a new empty GRFParameterInfo object.
 * @param nr The newgrf parameter that is changed.
 */
GRFParameterInfo::GRFParameterInfo(uint nr) :
        name(),
        desc(),
        type(PTYPE_UINT_ENUM),
        min_value(0),
        max_value(UINT32_MAX),
        def_value(0),
        param_nr(nr),
        first_bit(0),
        num_bit(32),
        complete_labels(false)
{}

/**
 * Create a new GRFParameterInfo object that is a deep copy of an existing
 *   parameter info object.
 * @param info The GRFParameterInfo object to make a copy of.
 */
GRFParameterInfo::GRFParameterInfo(GRFParameterInfo &info) :
        name(info.name),
        desc(info.desc),
        type(info.type),
        min_value(info.min_value),
        max_value(info.max_value),
        def_value(info.def_value),
        param_nr(info.param_nr),
        first_bit(info.first_bit),
        num_bit(info.num_bit),
        value_names(info.value_names),
        complete_labels(info.complete_labels)
{
}

/** Cleanup all parameter info. */
GRFParameterInfo::~GRFParameterInfo()
{
}

/**
 * Get the value of this user-changeable parameter from the given config.
 * @param config The GRFConfig to get the value from.
 * @return The value of this parameter.
 */
uint32 GRFParameterInfo::GetValue(struct GRFConfig *config) const
{
        /* GB doesn't work correctly with nbits == 32, so handle that case here. */
        if (this->num_bit == 32) return config->param[this->param_nr];
        return GB(config->param[this->param_nr], this->first_bit, this->num_bit);
}

/**
 * Set the value of this user-changeable parameter in the given config.
 * @param config The GRFConfig to set the value in.
 * @param value The new value.
 */
void GRFParameterInfo::SetValue(struct GRFConfig *config, uint32 value)
{
        /* SB doesn't work correctly with nbits == 32, so handle that case here. */
        if (this->num_bit == 32) {
                config->param[this->param_nr] = value;
        } else {
                SB(config->param[this->param_nr], this->first_bit, this->num_bit, value);
        }
        config->num_params = max<uint>(config->num_params, this->param_nr + 1);
        SetWindowDirty(WC_GAME_OPTIONS, WN_GAME_OPTIONS_NEWGRF_STATE);
}

/**
 * Finalize Action 14 info after file scan is finished.
 */
void GRFParameterInfo::Finalize()
{
        this->complete_labels = true;
        for (uint32 value = this->min_value; value <= this->max_value; value++) {
                if (this->value_names.count(value) == 0) {
                        this->complete_labels = false;
                        break;
                }
        }
}

/**
 * Update the palettes of the graphics from the config file.
 * Called when changing the default palette in advanced settings.
 * @param p1 Unused.
 * @return Always true.
 */
bool UpdateNewGRFConfigPalette(int32 p1)
{
        for (GRFConfig *c = _grfconfig_newgame; c != NULL; c = c->next) c->SetSuitablePalette();
        for (GRFConfig *c = _grfconfig_static;  c != NULL; c = c->next) c->SetSuitablePalette();
        for (GRFConfig *c = _all_grfs;          c != NULL; c = c->next) c->SetSuitablePalette();
        return true;
}

/**
 * Get the data section size of a GRF.
 * @param f GRF.
 * @return Size of the data section or SIZE_MAX if the file has no separate data section.
 */
size_t GRFGetSizeOfDataSection(FILE *f)
{
        extern const byte _grf_cont_v2_sig[];
        static const uint header_len = 14;

        byte data[header_len];
        if (fread(data, 1, header_len, f) == header_len) {
                if (data[0] == 0 && data[1] == 0 && MemCmpT(data + 2, _grf_cont_v2_sig, 8) == 0) {
                        /* Valid container version 2, get data section size. */
                        size_t offset = ((size_t)data[13] << 24) | ((size_t)data[12] << 16) | ((size_t)data[11] << 8) | (size_t)data[10];
                        if (offset >= 1 * 1024 * 1024 * 1024) {
                                DEBUG(grf, 0, "Unexpectedly large offset for NewGRF");
                                /* Having more than 1 GiB of data is very implausible. Mostly because then
                                 * all pools in OpenTTD are flooded already. Or it's just Action C all over.
                                 * In any case, the offsets to graphics will likely not work either. */
                                return SIZE_MAX;
                        }
                        return header_len + offset;
                }
        }

        return SIZE_MAX;
}

/**
 * Calculate the MD5 sum for a GRF, and store it in the config.
 * @param config GRF to compute.
 * @param subdir The subdirectory to look in.
 * @return MD5 sum was successfully computed
 */
static bool CalcGRFMD5Sum(GRFConfig *config, Subdirectory subdir)
{
        FILE *f;
        Md5 checksum;
        uint8 buffer[1024];
        size_t len, size;

        /* open the file */
        f = FioFOpenFile(config->filename, "rb", subdir, &size);
        if (f == NULL) return false;

        long start = ftell(f);
        size = min(size, GRFGetSizeOfDataSection(f));

        if (start < 0 || fseek(f, start, SEEK_SET) < 0) {
                FioFCloseFile(f);
                return false;
        }

        /* calculate md5sum */
        while ((len = fread(buffer, 1, (size > sizeof(buffer)) ? sizeof(buffer) : size, f)) != 0 && size != 0) {
                size -= len;
                checksum.Append(buffer, len);
        }
        checksum.Finish(config->ident.md5sum);

        FioFCloseFile(f);

        return true;
}


/**
 * Find the GRFID of a given grf, and calculate its md5sum.
 * @param config    grf to fill.
 * @param is_static grf is static.
 * @param subdir    the subdirectory to search in.
 * @return Operation was successfully completed.
 */
bool FillGRFDetails(GRFConfig *config, bool is_static, Subdirectory subdir)
{
        if (!FioCheckFileExists(config->filename, subdir)) {
                config->status = GCS_NOT_FOUND;
                return false;
        }

        /* Find and load the Action 8 information */
        LoadNewGRFFile(config, CONFIG_SLOT, GLS_FILESCAN, subdir);
        config->SetSuitablePalette();
        config->FinalizeParameterInfo();

        /* Skip if the grfid is 0 (not read) or 0xFFFFFFFF (ttdp system grf) */
        if (config->ident.grfid == 0 || config->ident.grfid == 0xFFFFFFFF || config->IsOpenTTDBaseGRF()) return false;

        if (is_static) {
                /* Perform a 'safety scan' for static GRFs */
                LoadNewGRFFile(config, CONFIG_SLOT, GLS_SAFETYSCAN, subdir);

                /* GCF_UNSAFE is set if GLS_SAFETYSCAN finds unsafe actions */
                if (HasBit(config->flags, GCF_UNSAFE)) return false;
        }

        return CalcGRFMD5Sum(config, subdir);
}


/**
 * Clear a GRF Config list, freeing all nodes.
 * @param config Start of the list.
 * @post \a config is set to \c NULL.
 */
void ClearGRFConfigList(GRFConfig **config)
{
        GRFConfig *c, *next;
        for (c = *config; c != NULL; c = next) {
                next = c->next;
                delete c;
        }
        *config = NULL;
}


/**
 * Copy a GRF Config list
 * @param dst pointer to destination list
 * @param src pointer to source list values
 * @param init_only the copied GRF will be processed up to GLS_INIT
 * @return pointer to the last value added to the destination list
 */
GRFConfig **CopyGRFConfigList(GRFConfig **dst, const GRFConfig *src, bool init_only)
{
        /* Clear destination as it will be overwritten */
        ClearGRFConfigList(dst);
        for (; src != NULL; src = src->next) {
                GRFConfig *c = new GRFConfig(*src);

                ClrBit(c->flags, GCF_INIT_ONLY);
                if (init_only) SetBit(c->flags, GCF_INIT_ONLY);

                *dst = c;
                dst = &c->next;
        }

        return dst;
}

/**
 * Removes duplicates from lists of GRFConfigs. These duplicates
 * are introduced when the _grfconfig_static GRFs are appended
 * to the _grfconfig on a newgame or savegame. As the parameters
 * of the static GRFs could be different that the parameters of
 * the ones used non-statically. This can result in desyncs in
 * multiplayers, so the duplicate static GRFs have to be removed.
 *
 * This function _assumes_ that all static GRFs are placed after
 * the non-static GRFs.
 *
 * @param list the list to remove the duplicates from
 */
static void RemoveDuplicatesFromGRFConfigList(GRFConfig *list)
{
        GRFConfig *prev;
        GRFConfig *cur;

        if (list == NULL) return;

        for (prev = list, cur = list->next; cur != NULL; prev = cur, cur = cur->next) {
                if (cur->ident.grfid != list->ident.grfid) continue;

                prev->next = cur->next;
                delete cur;
                cur = prev; // Just go back one so it continues as normal later on
        }

        RemoveDuplicatesFromGRFConfigList(list->next);
}

/**
 * Appends the static GRFs to a list of GRFs
 * @param dst the head of the list to add to
 */
void AppendStaticGRFConfigs(GRFConfig **dst)
{
        GRFConfig **tail = dst;
        while (*tail != NULL) tail = &(*tail)->next;

        CopyGRFConfigList(tail, _grfconfig_static, false);
        RemoveDuplicatesFromGRFConfigList(*dst);
}

/**
 * Appends an element to a list of GRFs
 * @param dst the head of the list to add to
 * @param el the new tail to be
 */
void AppendToGRFConfigList(GRFConfig **dst, GRFConfig *el)
{
        GRFConfig **tail = dst;
        while (*tail != NULL) tail = &(*tail)->next;
        *tail = el;

        RemoveDuplicatesFromGRFConfigList(*dst);
}


/** Reset the current GRF Config to either blank or newgame settings. */
void ResetGRFConfig(bool defaults)
{
        CopyGRFConfigList(&_grfconfig, _grfconfig_newgame, !defaults);
        AppendStaticGRFConfigs(&_grfconfig);
}


/**
 * Check if all GRFs in the GRF config from a savegame can be loaded.
 * @param grfconfig GrfConfig to check
 * @return will return any of the following 3 values:<br>
 * <ul>
 * <li> GLC_ALL_GOOD: No problems occurred, all GRF files were found and loaded
 * <li> GLC_COMPATIBLE: For one or more GRF's no exact match was found, but a
 *     compatible GRF with the same grfid was found and used instead
 * <li> GLC_NOT_FOUND: For one or more GRF's no match was found at all
 * </ul>
 */
GRFListCompatibility IsGoodGRFConfigList(GRFConfig *grfconfig)
{
        GRFListCompatibility res = GLC_ALL_GOOD;

        for (GRFConfig *c = grfconfig; c != NULL; c = c->next) {
                const GRFConfig *f = FindGRFConfig(c->ident.grfid, FGCM_EXACT, c->ident.md5sum);
                if (f == NULL || HasBit(f->flags, GCF_INVALID)) {
                        char buf [36];
                        md5sumToString (buf, c->ident.md5sum);

                        /* If we have not found the exactly matching GRF try to find one with the
                         * same grfid, as it most likely is compatible */
                        f = FindGRFConfig(c->ident.grfid, FGCM_COMPATIBLE, NULL, c->version);
                        if (f == NULL) {
                                /* No compatible grf was found, mark it as disabled */
                                DEBUG(grf, 0, "NewGRF %08X (%s) not found; checksum %s", BSWAP32(c->ident.grfid), c->filename, buf);

                                c->status = GCS_NOT_FOUND;
                                res = GLC_NOT_FOUND;
                                continue;
                        }

                        DEBUG(grf, 1, "NewGRF %08X (%s) not found; checksum %s. Compatibility mode on", BSWAP32(c->ident.grfid), c->filename, buf);
                        if (!HasBit(c->flags, GCF_COMPATIBLE)) {
                                /* Preserve original_md5sum after it has been assigned */
                                SetBit(c->flags, GCF_COMPATIBLE);
                                memcpy(c->original_md5sum, c->ident.md5sum, sizeof(c->original_md5sum));
                        }

                        /* Non-found has precedence over compatibility load */
                        if (res != GLC_NOT_FOUND) res = GLC_COMPATIBLE;
                }

                DEBUG(grf, 1, "Loading GRF %08X from %s", BSWAP32(f->ident.grfid), f->filename);
                /* The filename could be the filename as in the savegame. As we need
                 * to load the GRF here, we need the correct filename, so overwrite that
                 * in any case and set the name and info when it is not set already.
                 * When the GCF_COPY flag is set, it is certain that the filename is
                 * already a local one, so there is no need to replace it. */
                if (!HasBit(c->flags, GCF_COPY)) {
                        free(c->filename);
                        c->filename = xstrdup(f->filename);
                        memcpy(c->ident.md5sum, f->ident.md5sum, sizeof(c->ident.md5sum));
                        c->name = f->name;
                        c->info = f->info;
                        c->error = NULL;
                        c->version = f->version;
                        c->min_loadable_version = f->min_loadable_version;
                        c->num_valid_params = f->num_valid_params;
                        c->has_param_defaults = f->has_param_defaults;
                        for (uint i = 0; i < f->param_info.Length(); i++) {
                                if (f->param_info[i] == NULL) {
                                        *c->param_info.Append() = NULL;
                                } else {
                                        *c->param_info.Append() = new GRFParameterInfo(*f->param_info[i]);
                                }
                        }
                }
        }

        return res;
}

/** Helper for scanning for files with GRF as extension */
class GRFFileScanner : FileScanner {
        uint next_update; ///< The next (realtime tick) we do update the screen.
        uint num_scanned; ///< The number of GRFs we have scanned.

public:
        GRFFileScanner() : next_update(_realtime_tick), num_scanned(0)
        {
        }

        /* virtual */ bool AddFile(const char *filename, size_t basepath_length, const char *tar_filename);

        /** Do the scan for GRFs. */
        static uint DoScan()
        {
                GRFFileScanner fs;
                int ret = fs.Scan(".grf", NEWGRF_DIR);
                /* The number scanned and the number returned may not be the same;
                 * duplicate NewGRFs and base sets are ignored in the return value. */
                _settings_client.gui.last_newgrf_count = fs.num_scanned;
                return ret;
        }
};

bool GRFFileScanner::AddFile(const char *filename, size_t basepath_length, const char *tar_filename)
{
        GRFConfig *c = new GRFConfig(filename + basepath_length);

        bool added = true;
        if (FillGRFDetails(c, false)) {
                if (_all_grfs == NULL) {
                        _all_grfs = c;
                } else {
                        /* Insert file into list at a position determined by its
                         * name, so the list is sorted as we go along */
                        GRFConfig **pd, *d;
                        bool stop = false;
                        for (pd = &_all_grfs; (d = *pd) != NULL; pd = &d->next) {
                                if (c->ident.matches (d->ident)) added = false;
                                /* Because there can be multiple grfs with the same name, make sure we checked all grfs with the same name,
                                 *  before inserting the entry. So insert a new grf at the end of all grfs with the same name, instead of
                                 *  just after the first with the same name. Avoids doubles in the list. */
                                if (strcasecmp(c->GetName(), d->GetName()) <= 0) {
                                        stop = true;
                                } else if (stop) {
                                        break;
                                }
                        }
                        if (added) {
                                c->next = d;
                                *pd = c;
                        }
                }
        } else {
                added = false;
        }

        this->num_scanned++;
        if (this->next_update <= _realtime_tick) {
                _modal_progress_work_mutex->EndCritical();
                _modal_progress_paint_mutex->BeginCritical();

                const char *name = c->name->get_string();
                if (name == NULL) name = c->filename;
                UpdateNewGRFScanStatus(this->num_scanned, name);

                _modal_progress_work_mutex->BeginCritical();
                _modal_progress_paint_mutex->EndCritical();

                this->next_update = _realtime_tick + 200;
        }

        if (!added) {
                /* File couldn't be opened, or is either not a NewGRF or is a
                 * 'system' NewGRF or it's already known, so forget about it. */
                delete c;
        }

        return added;
}

/**
 * Simple sorter for GRFS
 * @param p1 the first GRFConfig *
 * @param p2 the second GRFConfig *
 * @return the same strcmp would return for the name of the NewGRF.
 */
static int CDECL GRFSorter(GRFConfig * const *p1, GRFConfig * const *p2)
{
        const GRFConfig *c1 = *p1;
        const GRFConfig *c2 = *p2;

        return strnatcmp(c1->GetName(), c2->GetName());
}

/**
 * Really perform the scan for all NewGRFs.
 * @param callback The callback to call after the scanning is complete.
 */
void DoScanNewGRFFiles(void *callback)
{
        _modal_progress_work_mutex->BeginCritical();

        ClearGRFConfigList(&_all_grfs);
        TarScanner::DoScan(TarScanner::NEWGRF);

        DEBUG(grf, 1, "Scanning for NewGRFs");
        uint num = GRFFileScanner::DoScan();

        DEBUG(grf, 1, "Scan complete, found %d files", num);
        if (num != 0 && _all_grfs != NULL) {
                /* Sort the linked list using quicksort.
                 * For that we first have to make an array, then sort and
                 * then remake the linked list. */
                GRFConfig **to_sort = xmalloct<GRFConfig*>(num);

                uint i = 0;
                for (GRFConfig *p = _all_grfs; p != NULL; p = p->next, i++) {
                        to_sort[i] = p;
                }
                /* Number of files is not necessarily right */
                num = i;

                QSortT(to_sort, num, &GRFSorter);

                for (i = 1; i < num; i++) {
                        to_sort[i - 1]->next = to_sort[i];
                }
                to_sort[num - 1]->next = NULL;
                _all_grfs = to_sort[0];

                free(to_sort);

#ifdef ENABLE_NETWORK
                NetworkAfterNewGRFScan();
#endif
        }

        _modal_progress_work_mutex->EndCritical();
        _modal_progress_paint_mutex->BeginCritical();

        /* Yes... these are the NewGRF windows */
        InvalidateWindowClassesData(WC_SAVELOAD, 0, true);
        InvalidateWindowData(WC_GAME_OPTIONS, WN_GAME_OPTIONS_NEWGRF_STATE, GOID_NEWGRF_RESCANNED, true);
        if (callback != NULL) ((NewGRFScanCallback*)callback)->OnNewGRFsScanned();

        DeleteWindowByClass(WC_MODAL_PROGRESS);
        SetModalProgress(false);
        MarkWholeScreenDirty();
        _modal_progress_paint_mutex->EndCritical();
}

/**
 * Scan for all NewGRFs.
 * @param callback The callback to call after the scanning is complete.
 */
void ScanNewGRFFiles(NewGRFScanCallback *callback)
{
        /* First set the modal progress. This ensures that it will eventually let go of the paint mutex. */
        SetModalProgress(true);
        /* Only then can we really start, especially by marking the whole screen dirty. Get those other windows hidden!. */
        MarkWholeScreenDirty();

        if (!VideoDriver::GetActiveDriver()->HasGUI() || !ThreadObject::New(&DoScanNewGRFFiles, callback, NULL, "ottd:newgrf-scan")) {
                _modal_progress_work_mutex->EndCritical();
                _modal_progress_paint_mutex->EndCritical();
                DoScanNewGRFFiles(callback);
                _modal_progress_paint_mutex->BeginCritical();
                _modal_progress_work_mutex->BeginCritical();
        } else {
                UpdateNewGRFScanStatus(0, NULL);
        }
}

/**
 * Find a NewGRF in the scanned list.
 * @param grfid GRFID to look for,
 * @param mode Restrictions for matching grfs
 * @param md5sum Expected MD5 sum
 * @param desired_version Requested version
 * @return The matching grf, if it exists in #_all_grfs, else \c NULL.
 */
const GRFConfig *FindGRFConfig(uint32 grfid, FindGRFConfigMode mode, const uint8 *md5sum, uint32 desired_version)
{
        assert((mode == FGCM_EXACT) != (md5sum == NULL));
        const GRFConfig *best = NULL;
        for (const GRFConfig *c = _all_grfs; c != NULL; c = c->next) {
                /* if md5sum is set, we look for an exact match and continue if not found */
                if (!c->ident.matches (grfid, md5sum)) continue;
                /* return it, if the exact same newgrf is found, or if we do not care about finding "the best" */
                if (md5sum != NULL || mode == FGCM_ANY) return c;
                /* Skip incompatible stuff, unless explicitly allowed */
                if (mode != FGCM_NEWEST && HasBit(c->flags, GCF_INVALID)) continue;
                /* check version compatibility */
                if (mode == FGCM_COMPATIBLE && (c->version < desired_version || c->min_loadable_version > desired_version)) continue;
                /* remember the newest one as "the best" */
                if (best == NULL || c->version > best->version) best = c;
        }

        return best;
}

#ifdef ENABLE_NETWORK

/** Structure for UnknownGRFs; this is a lightweight variant of GRFConfig */
struct UnknownGRF : public GRFIdentifier {
        UnknownGRF *next;     ///< The next unknown GRF.
        ttd_shared_ptr<GRFTextMap> name; ///< Name of the GRF.
};

/**
 * Finds the name of a NewGRF in the list of names for unknown GRFs. An
 * unknown GRF is a GRF where the .grf is not found during scanning.
 *
 * The names are resolved via UDP calls to servers that should know the name,
 * though the replies may not come. This leaves "<Unknown>" as name, though
 * that shouldn't matter _very_ much as they need GRF crawler or so to look
 * up the GRF anyway and that works better with the GRF ID.
 *
 * @param ident  the GRF identifier
 * @param create whether to create a new GRFConfig if the GRFConfig did not
 *               exist in the fake list of GRFConfigs.
 *               If true, a GRFConfig will be returned unconditionally, and
 *               it will be created if it does not exist yet.
 *               If false, a GRFConfig will be returned only if it already
 *               existed and is still unknown; otherwise, NULL will be returned.
 * @return The shared GRFTextMap of the name of the GRFConfig with the given GRF ID
 *         and MD5 checksum or NULL when it does not exist and create is false.
 *         This value must NEVER be freed by the caller.
 */
ttd_shared_ptr<GRFTextMap> *FindUnknownGRFName (const GRFIdentifier &ident, bool create)
{
        UnknownGRF *grf;
        static UnknownGRF *unknown_grfs = NULL;

        for (grf = unknown_grfs; grf != NULL; grf = grf->next) {
                if (grf->matches (ident)) {
                        return (create || strcmp (grf->name->get_string(), UNKNOWN_GRF_NAME_PLACEHOLDER) == 0) ? &grf->name : NULL;
                }
        }

        if (!create) return NULL;

        grf = new UnknownGRF;
        grf->grfid = ident.grfid;
        memcpy (grf->md5sum, ident.md5sum, sizeof(grf->md5sum));
        grf->next  = unknown_grfs;

        GRFTextMap *map = new GRFTextMap;
        map->add_default (UNKNOWN_GRF_NAME_PLACEHOLDER);
        grf->name.reset (map);

        unknown_grfs = grf;
        return &grf->name;
}

#endif /* ENABLE_NETWORK */


/**
 * Retrieve a NewGRF from the current config by its grfid.
 * @param grfid grf to look for.
 * @param mask  GRFID mask to allow for partial matching.
 * @return The grf config, if it exists, else \c NULL.
 */
GRFConfig *GetGRFConfig(uint32 grfid, uint32 mask)
{
        GRFConfig *c;

        for (c = _grfconfig; c != NULL; c = c->next) {
                if ((c->ident.grfid & mask) == (grfid & mask)) return c;
        }

        return NULL;
}


/** Build a string containing space separated parameter values, and terminate */
void GRFBuildParamList (stringb *dst, const GRFConfig *c)
{
        /* Return an empty string if there are no parameters */
        if (c->num_params == 0) {
                dst->clear();
                return;
        }

        dst->fmt ("%d", c->param[0]);

        for (uint i = 1; i < c->num_params; i++) {
                dst->append_fmt (" %d", c->param[i]);
        }
}

/** Base GRF ID for OpenTTD's base graphics GRFs. */
static const uint32 OPENTTD_GRAPHICS_BASE_GRF_ID = BSWAP32(0xFF4F5400);

/**
 * Checks whether this GRF is a OpenTTD base graphic GRF.
 * @return true if and only if it is a base GRF.
 */
bool GRFConfig::IsOpenTTDBaseGRF() const
{
        return (this->ident.grfid & 0x00FFFFFF) == OPENTTD_GRAPHICS_BASE_GRF_ID;
}

/**
 * Search a textfile file next to this NewGRF.
 * @param type The type of the textfile to search for.
 * @return A description for the textfile.
 */
TextfileDesc GRFConfig::GetTextfile (TextfileType type) const
{
        return TextfileDesc (type, NEWGRF_DIR, this->filename);
}