[libcalamares] Add a convenience for reading mtab

- used by umount and cleartempmounts (in future)

src/libcalamares/partition/Mount.cpp

@@ -14,6 +14,7 @@
 #include "partition/Sync.h"
 #include "utils/CalamaresUtilsSystem.h"
 #include "utils/Logger.h"
+#include "utils/String.h"
 
 #include <QDir>
 #include <QTemporaryDir>
@@ -123,5 +124,32 @@ TemporaryMount::path() const
     return m_d ? m_d->m_mountDir.path() : QString();
 }
 
+QList< MtabInfo >
+MtabInfo::fromMtabFilteredByPrefix( const QString& mountPrefix, const QString& mtabPath )
+{
+    QFile f( mtabPath.isEmpty() ? "/etc/mtab" : mtabPath );
+    if ( !f.open( QIODevice::ReadOnly ) )
+    {
+        return {};
+    }
+
+    QTextStream in( &f );
+    QList< MtabInfo > l;
+    while ( !f.atEnd() )
+    {
+        QStringList line = in.readLine().split( ' ', SplitSkipEmptyParts );
+        if ( line.length() == 3 && !line[ 0 ].startsWith( '#' ) )
+        {
+            // Lines have format: <device> <mountpoint> <options>, so check
+            // the mountpoint field. Everything starts with an empty string.
+            if ( line[ 1 ].startsWith( mountPrefix ) )
+            {
+                l.append( { line[ 0 ], line[ 1 ] } );
+            }
+        }
+    }
+    return l;
+}
+
 }  // namespace Partition
 }  // namespace CalamaresUtils

src/libcalamares/partition/Mount.h

@@ -14,6 +14,7 @@
 
 #include "DllMacro.h"
 
+#include <QList>
 #include <QString>
 #include <QStringList>
 
@@ -50,6 +51,13 @@ DLLEXPORT int mount( const QString& devicePath,
  */
 DLLEXPORT int unmount( const QString& path, const QStringList& options = QStringList() );
 
+
+/** @brief Mount and automatically unmount a device
+ *
+ * The TemporaryMount object mounts a filesystem, and is like calling
+ * the mount() function, above. When the object is destroyed, unmount()
+ * is called with suitable options to undo the original mount.
+ */
 class DLLEXPORT TemporaryMount
 {
 public:
@@ -68,6 +76,36 @@ private:
     std::unique_ptr< Private > m_d;
 };
 
+
+/** @brief Information about a mount point from /etc/mtab
+ *
+ * Entries in /etc/mtab are of the form: <device> <mountpoint> <other>
+ * This struct only stores device and mountpoint.
+ *
+ * The main way of getting these structs is to call fromMtab() to read
+ * an /etc/mtab-like file and storing all of the entries from it.
+ */
+struct DLLEXPORT MtabInfo
+{
+    QString device;
+    QString mountPoint;
+
+    /** @brief Reads an mtab-like file and returns the entries from it
+     *
+     * When @p mtabPath is given, that file is read. If the given name is
+     * empty (e.g. the default) then /etc/mtab is read, instead.
+     *
+     * If @p mountPrefix is given, then only entries that have a mount point
+     * that starts with that prefix are returned.
+     */
+    static QList< MtabInfo > fromMtabFilteredByPrefix( const QString& mountPrefix = QString(),
+                                                       const QString& mtabPath = QString() );
+    /// @brief Predicate to sort MtabInfo objects by device-name
+    static bool deviceOrder( const MtabInfo& a, const MtabInfo& b ) { return a.device > b.device; }
+    /// @brief Predicate to sort MtabInfo objects by mount-point
+    static bool mountPointOrder( const MtabInfo& a, const MtabInfo& b ) { return a.mountPoint > b.mountPoint; }
+};
+
 }  // namespace Partition
 }  // namespace CalamaresUtils