[libcalamares] Reading a file from target system

src/libcalamares/utils/CalamaresUtilsSystem.cpp

@@ -147,6 +147,30 @@ System::createTargetFile( const QString& path, const QByteArray& contents, Write
     return CreationResult( QFileInfo( f ).canonicalFilePath() );
 }
 
+QStringList
+System::readTargetFile( const QString& path ) const
+{
+    const QString completePath = targetPath( path );
+    if ( completePath.isEmpty() )
+    {
+        return QStringList();
+    }
+
+    QFile f( completePath );
+    if ( !f.open( QIODevice::ReadOnly ) )
+    {
+        return QStringList();
+    }
+
+    QTextStream in( &f );
+    QStringList l;
+    while ( !f.atEnd() )
+    {
+        l << in.readLine();
+    }
+    return l;
+}
+
 void
 System::removeTargetFile( const QString& path ) const
 {

src/libcalamares/utils/CalamaresUtilsSystem.h

@@ -287,6 +287,24 @@ public:
      */
     DLLEXPORT void removeTargetFile( const QString& path ) const;
 
+    /** @brief Reads a file from the target system.
+     *
+     * @param path Path to the file; this is interpreted from the root of
+     *      the target system (@see targetPath()).
+     *
+     * Does no error checking, and returns an empty list if the file does
+     * not exist.
+     *
+     * NOTE: This function is now basically the same as QFile::readAll(),
+     *       splitting into lines, but Calamares may need to change
+     *       permissions or raise privileges to actually read the file,
+     *       which is why there is an API.
+     *
+     * NOTE: Since this buffers the whole file in memory, reading big files
+     *       is not recommended.
+     */
+    DLLEXPORT QStringList readTargetFile( const QString& path ) const;
+
     /** @brief Ensure that the directory @p path exists
      *
      * @param path a full pathname to a desired directory.