Fix a bug in FileChannel.map.

Found by a Harmony test.

Change-Id: I1f2ba191242dd6236549e6ed4ef77021ad7ae628

1 files changed, 7 insertions, 1 deletions

diff --git a/luni/src/main/java/java/nio/FileChannelImpl.java b/luni/src/main/java/java/nio/FileChannelImpl.java
index 53c1e4d..bc13efd 100644
--- a/luni/src/main/java/java/nio/FileChannelImpl.java
+++ b/luni/src/main/java/java/nio/FileChannelImpl.java
@@ -228,7 +228,13 @@ final class FileChannelImpl extends FileChannel {
             throw new NonReadableChannelException();
         }
         if (position + size > size()) {
-            truncate(position + size);
+            // We can't defer to FileChannel.truncate because that will only make a file shorter,
+            // and we only care about making our backing file longer here.
+            try {
+                Libcore.os.ftruncate(fd, position + size);
+            } catch (ErrnoException errnoException) {
+                throw errnoException.rethrowAsIOException();
+            }
         }
         long alignment = position - position % Libcore.os.sysconf(_SC_PAGE_SIZE);
         int offset = (int) (position - alignment);