Get file position when attaching an open file descriptor to QFile

This was already being done when attaching to FILE* streams. Doing the
same here makes the API consistent and more usable. Namely, one can use
QFile::pos() to obtain the file position.

Test case verifies this doesn't break support for sequential files. More
thorough test case included in large file support test.

Reviewed-by: Thiago Macieira

2 files changed, 61 insertions, 1 deletions

diff --git a/src/corelib/io/qfile.cpp b/src/corelib/io/qfile.cpp
index 64d8ef3..4dd6185 100644
--- a/src/corelib/io/qfile.cpp
+++ b/src/corelib/io/qfile.cpp
@@ -1120,8 +1120,13 @@ bool QFile::open(int fd, OpenMode mode)
     }
     if(d->openExternalFile(mode, fd)) {
         QIODevice::open(mode);
-        if (mode & Append)
+        if (mode & Append) {
             seek(size());
+        } else {
+            qint64 pos = (qint64)QT_LSEEK(fd, QT_OFF_T(0), SEEK_CUR);
+            if (pos != -1)
+                seek(pos);
+        }
         return true;
     }
     return false;
diff --git a/tests/auto/qfile/tst_qfile.cpp b/tests/auto/qfile/tst_qfile.cpp
index 19fbecd..bbb6280 100644
--- a/tests/auto/qfile/tst_qfile.cpp
+++ b/tests/auto/qfile/tst_qfile.cpp
@@ -187,6 +187,8 @@ private slots:
     void mapOpenMode_data();
     void mapOpenMode();
 
+    void openStandardStreams();
+
     // --- Task related tests below this line
     void task167217();
 
@@ -2634,5 +2636,58 @@ void tst_QFile::openDirectory()
     QVERIFY(!f1.open(QIODevice::ReadOnly|QIODevice::Unbuffered));
 }
 
+void tst_QFile::openStandardStreams()
+{
+    // Using file descriptors
+    {
+        QFile in;
+        in.open(STDIN_FILENO, QIODevice::ReadOnly);
+        QCOMPARE( in.pos(), (qint64)0 );
+        QCOMPARE( in.size(), (qint64)0 );
+        QVERIFY( in.isSequential() );
+    }
+
+    {
+        QFile out;
+        out.open(STDOUT_FILENO, QIODevice::WriteOnly);
+        QCOMPARE( out.pos(), (qint64)0 );
+        QCOMPARE( out.size(), (qint64)0 );
+        QVERIFY( out.isSequential() );
+    }
+
+    {
+        QFile err;
+        err.open(STDERR_FILENO, QIODevice::WriteOnly);
+        QCOMPARE( err.pos(), (qint64)0 );
+        QCOMPARE( err.size(), (qint64)0 );
+        QVERIFY( err.isSequential() );
+    }
+
+    // Using streams
+    {
+        QFile in;
+        in.open(stdin, QIODevice::ReadOnly);
+        QCOMPARE( in.pos(), (qint64)0 );
+        QCOMPARE( in.size(), (qint64)0 );
+        QVERIFY( in.isSequential() );
+    }
+
+    {
+        QFile out;
+        out.open(stdout, QIODevice::WriteOnly);
+        QCOMPARE( out.pos(), (qint64)0 );
+        QCOMPARE( out.size(), (qint64)0 );
+        QVERIFY( out.isSequential() );
+    }
+
+    {
+        QFile err;
+        err.open(stderr, QIODevice::WriteOnly);
+        QCOMPARE( err.pos(), (qint64)0 );
+        QCOMPARE( err.size(), (qint64)0 );
+        QVERIFY( err.isSequential() );
+    }
+}
+
 QTEST_MAIN(tst_QFile)
 #include "tst_qfile.moc"