Dive pictures: Move metadata functions into own translation unit

Move all metadata function into new core/metadata.cpp file.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

core/metadata.cpp

@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "metadata.h"
+#include "exif.h"
+#include "qthelper.h"
+#include <QString>
+#include <QFile>
+#include <QDateTime>
+
+// Fetch quint16 in big endian mode from QFile and return 0 on error.
+// This is a very specialized function for parsing JPEGs, therefore we can get away with such an in-band error code.
+static inline quint16 getShortBE(QFile &f)
+{
+	unsigned char buf[2];
+	if (f.read(reinterpret_cast<char *>(buf), 2) != 2)
+		return 0;
+	return (buf[0] << 8) | buf[1];
+}
+
+static bool parseExif(QFile &f, struct metadata *metadata)
+{
+	if (getShortBE(f) != 0xffd8)
+		return false;
+	for (;;) {
+		switch (getShortBE(f)) {
+		case 0xffc0:
+		case 0xffc2:
+		case 0xffc4:
+		case 0xffd0 ... 0xffd7:
+		case 0xffdb:
+		case 0xffdd:
+		case 0xffe0:
+		case 0xffe2 ... 0xffef:
+		case 0xfffe: {
+			quint16 len = getShortBE(f);
+			if (len < 2)
+				return false;
+			f.seek(f.pos() + len - 2); // TODO: switch to QFile::skip()
+			break;
+		}
+		case 0xffe1: {
+			quint16 len = getShortBE(f);
+			if (len < 2)
+				return false;
+			len -= 2;
+			QByteArray data = f.read(len);
+			if (data.size() != len)
+				return false;
+			easyexif::EXIFInfo exif;
+			if (exif.parseFromEXIFSegment(reinterpret_cast<const unsigned char *>(data.constData()), len) != PARSE_EXIF_SUCCESS)
+				return false;
+			metadata->longitude.udeg = lrint(1000000.0 * exif.GeoLocation.Longitude);
+			metadata->latitude.udeg = lrint(1000000.0 * exif.GeoLocation.Latitude);
+			metadata->timestamp = exif.epoch();
+			return true;
+		}
+		case 0xffda:
+		case 0xffd9:
+			// We expect EXIF data before any scan data
+			return false;
+		default:
+			return false;
+		}
+	}
+}
+
+static bool parseMP4(QFile &, metadata *)
+{
+	// TODO: Implement MP4 parsing
+	return false;
+}
+
+extern "C" mediatype_t get_metadata(const char *filename_in, metadata *data)
+{
+	data->timestamp = 0;
+	data->latitude.udeg = 0;
+	data->longitude.udeg = 0;
+
+	QString filename = localFilePath(QString(filename_in));
+	QFile f(filename);
+	if (!f.open(QIODevice::ReadOnly))
+		return MEDIATYPE_IO_ERROR;
+
+	if (parseExif(f, data)) {
+		return MEDIATYPE_PICTURE;
+	} else if(parseMP4(f, data)) {
+		return MEDIATYPE_VIDEO;
+	} else {
+		// If we couldn't parse EXIF or MP4 data, use file creation date.
+		// TODO: QFileInfo::created is deprecated in newer Qt versions.
+		data->timestamp = QFileInfo(filename).created().toMSecsSinceEpoch() / 1000;
+		return MEDIATYPE_UNKNOWN;
+	}
+}
+
+extern "C" timestamp_t picture_get_timestamp(const char *filename)
+{
+	struct metadata data;
+	get_metadata(filename, &data);
+	return data.timestamp;
+}
+
+extern "C" void picture_load_exif_data(struct picture *p)
+{
+	struct metadata data;
+	if (get_metadata(p->filename, &data) == MEDIATYPE_IO_ERROR)
+		return;
+	p->longitude = data.longitude;
+	p->latitude = data.latitude;
+}