Show files in tooltips for pieces progress bars

In addition to the current tooltip, which shows color legend, if user
holds the Shift key during hovering we show another tooltip which
contains a table of contents for the piece under the moue cursor. The
table lists file sizes and names. If the cursor points to a part of a
file which spans several pieces, those pieces are highlighted.

src/base/bittorrent/torrentinfo.cpp

@@ -26,6 +26,7 @@
  * exception statement from your version.
  */
 
+#include <QDebug>
 #include <QString>
 #include <QList>
 #include <QUrl>
@@ -138,6 +139,12 @@ int TorrentInfo::pieceLength() const
     return m_nativeInfo->piece_length();
 }
 
+int TorrentInfo::pieceLength(int index) const
+{
+    if (!isValid()) return -1;
+    return m_nativeInfo->piece_size(index);
+}
+
 int TorrentInfo::piecesCount() const
 {
     if (!isValid()) return -1;
@@ -178,7 +185,7 @@ qlonglong TorrentInfo::fileSize(int index) const
 
 qlonglong TorrentInfo::fileOffset(int index) const
 {
-    if (!isValid()) return  -1;
+    if (!isValid()) return -1;
     return m_nativeInfo->file_at(index).offset;
 }
 
@@ -213,24 +220,79 @@ QByteArray TorrentInfo::metadata() const
 
 QStringList TorrentInfo::filesForPiece(int pieceIndex) const
 {
-    if (pieceIndex < 0)
-        return QStringList();
+    // no checks here because fileIndicesForPiece() will return an empty list
+    QVector<int> fileIndices = fileIndicesForPiece(pieceIndex);
 
-    std::vector<libtorrent::file_slice> files(
-        nativeInfo()->map_block(pieceIndex, 0, nativeInfo()->piece_size(pieceIndex)));
     QStringList res;
-    for (const libtorrent::file_slice& s: files) {
-        res.append(filePath(s.file_index));
-    }
+    res.reserve(fileIndices.size());
+    std::transform(fileIndices.begin(), fileIndices.end(), std::back_inserter(res),
+        [this](int i) { return filePath(i); });
+
     return res;
 }
 
+QVector<int> TorrentInfo::fileIndicesForPiece(int pieceIndex) const
+{
+    if (!isValid() || (pieceIndex < 0) || (pieceIndex >= piecesCount()))
+        return QVector<int>();
+
+    std::vector<libt::file_slice> files(
+        nativeInfo()->map_block(pieceIndex, 0, nativeInfo()->piece_size(pieceIndex)));
+    QVector<int> res;
+    res.reserve(files.size());
+    std::transform(files.begin(), files.end(), std::back_inserter(res),
+        [](const libt::file_slice &s) { return s.file_index; });
+
+    return res;
+}
+
+TorrentInfo::PieceRange TorrentInfo::filePieces(const QString& file) const
+{
+    if (!isValid()) // if we do not check here the debug message will be printed, which would be not correct
+        return {};
+
+    int index = fileIndex(file);
+    if (index == -1) {
+        qDebug() << "Filename" << file << "was not found in torrent" << name();
+        return {};
+    }
+    return filePieces(index);
+}
+
+TorrentInfo::PieceRange TorrentInfo::filePieces(int fileIndex) const
+{
+    if (!isValid())
+        return {};
+
+    if ((fileIndex < 0) || (fileIndex >= filesCount())) {
+        qDebug() << "File index (" << fileIndex << ") is out of range for torrent" << name();
+        return {};
+    }
+
+    const libt::file_storage &files = nativeInfo()->files();
+    const auto fileSize = files.file_size(fileIndex);
+    const auto firstOffset = files.file_offset(fileIndex);
+    return makeInterval(static_cast<int>(firstOffset / pieceLength()),
+                        static_cast<int>((firstOffset + fileSize - 1) / pieceLength()));
+}
+
 void TorrentInfo::renameFile(uint index, const QString &newPath)
 {
     if (!isValid()) return;
     nativeInfo()->rename_file(index, Utils::String::toStdString(newPath));
 }
 
+int BitTorrent::TorrentInfo::fileIndex(const QString& fileName) const
+{
+    // the check whether the object valid is not needed here
+    // because filesCount() returns -1 in that case and the loop exits immediately
+    for (int i = 0; i < filesCount(); ++i)
+        if (fileName == filePath(i))
+            return i;
+
+    return -1;
+}
+
 TorrentInfo::NativePtr TorrentInfo::nativeInfo() const
 {
     return m_nativeInfo;