exif_internal.h

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/*
    This file is part of Ansel,
    Copyright (C) 2026 Aurélien PIERRE.
 
    Ansel 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, either version 3 of the License, or
    (at your option) any later version.
 
    Ansel 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 Ansel.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#ifndef DT_METADATA_EXIF_INTERNAL_H
#define DT_METADATA_EXIF_INTERNAL_H
 
#include "common/image.h"
 
#include <exiv2/exiv2.hpp>
#include <string>
 
/* Windows path handling for exiv2.
 *
 * Every path in Ansel is UTF-8: that is what GLib hands us, what the database stores, and
 * what the film-roll scanner produces. On Windows the narrow CRT reads a `const char *`
 * path in the process ANSI code page instead -- CP-1252, CP-850, whatever the machine is
 * set to -- so a path holding a single byte above 0x7F simply does not resolve. Every
 * library Ansel hands a path to therefore gets a wide one: `libraw_open_wfile()` in
 * `imageio/imageio_libraw.c`, `TIFFOpenW()` in `imageio/imageio_tiff.c`, `g_fopen()` (which
 * is `_wfopen()` underneath) in the XMP sidecar writer. exiv2 is the same case, and
 * WIDEN() is where it happens.
 *
 * exiv2 0.28.0 deleted the wide overloads, and this is where that showed: WIDEN() quietly
 * became the identity, everything still compiled, and Windows users lost all EXIF for any
 * image below a folder with an accent in its name (issue #474, and darktable #15478 and
 * #19572 for the same bug in the same place). So a build that cannot widen is now a build
 * error rather than a silent runtime data loss. `-DUSE_BUNDLED_EXIV2=ON` -- the default --
 * is what supplies the capability; see `doc/exiv2.md`.
 */
#if defined(_WIN32) && !defined(EXV_UNICODE_PATH) && !defined(ANSEL_ALLOW_NARROW_EXIV2_PATHS)
#error "This exiv2 was built without EXV_UNICODE_PATH (EXIV2_ENABLE_WIN_UNICODE), so there is no way to give it a Windows path holding a non-ASCII character: EXIF reads, thumbnail extraction and XMP sidecar writes would all fail at runtime, silently, for those images. Configure with -DUSE_BUNDLED_EXIV2=ON (the default) and see doc/exiv2.md. Define ANSEL_ALLOW_NARROW_EXIV2_PATHS to build anyway and accept that."
#endif
 
#if defined(_WIN32) && defined(EXV_UNICODE_PATH)
 
std::wstring dt_exiv2_widen_path(const char *utf8_path);
 
#define WIDEN(s) dt_exiv2_widen_path(s)
 
#else
 
/* Everywhere else a path is bytes, and those bytes are already UTF-8. */
#define WIDEN(s) (s)
 
#endif
 
/* There used to be a read_metadata_threadsafe() macro here, wrapping readMetadata() in a
 * process-wide lock. The lock is gone -- exiv2 0.27.7's Exif and IPTC code is reentrant and
 * its XMP path serializes itself, so the only entry points that are not thread-safe are
 * XmpParser::initialize() and XmpProperties::registerNs(), which Ansel calls exclusively
 * from dt_exif_init() before any thread exists. See doc/lock-audit.md.
 *
 * The macro is gone with it rather than left as a no-op: a wrapper called "threadsafe" that
 * does nothing is worse than no wrapper, because it reads like a guarantee. Call
 * image->readMetadata() directly. */
 
void dt_remove_exif_keys(Exiv2::ExifData &exif, const char *keys[], unsigned int n_keys);
 
bool dt_exif_read_exif_tag(Exiv2::ExifData &exifData, Exiv2::ExifData::const_iterator *pos,
                           std::string key);
 
bool dt_exif_decode_xmp_data(dt_image_t *img, Exiv2::XmpData &xmpData, int version,
                             bool exif_read);
 
#endif // DT_METADATA_EXIF_INTERNAL_H
 
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