Fix infinite loop on #transferFrom underflow

Fixes marschall#147
guicamest · May 14, 2023 · 3a3b9ab · 3a3b9ab
1 parent 6f33c9f
commit 3a3b9ab
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Showing 2 changed files with 36 additions and 12 deletions.
diff --git a/src/main/java/com/github/marschall/memoryfilesystem/MemoryInode.java b/src/main/java/com/github/marschall/memoryfilesystem/MemoryInode.java
@@ -173,8 +173,11 @@ long transferFrom(ReadableByteChannel src, long position, long count) throws IOE
         // Since ByteBuffer objects are quite small and don't copy the contents
         // of the backing array allocating a ByteBuffer is probably cheaper.
         ByteBuffer buffer = ByteBuffer.wrap(block, startIndexInBlock, lengthInBlock);
-        readFully(buffer, src, lengthInBlock);
-        transferred += lengthInBlock;
+        int read = readFully(buffer, src, lengthInBlock);
+        transferred += read;
+        if (read < lengthInBlock) {
+          break;
+        }
 
         startIndexInBlock = 0;
         currentBlock += 1;
@@ -362,11 +365,15 @@ private static int writeFully(ByteBuffer src, WritableByteChannel target, int to
   }
 
   private static int readFully(ByteBuffer src, ReadableByteChannel target, int toRead) throws IOException {
-    int read = 0;
-    while (read < toRead) {
-      read += target.read(src);
+    int total = 0;
+    while (total < toRead) {
+      int read = target.read(src);
+      if (read <= 0) {
+        return total;
+      }
+      total += read;
     }
-    return read;
+    return total;
   }
 
   private void ensureCapacity(long capacity) {

diff --git a/src/test/java/com/github/marschall/memoryfilesystem/MemoryFileSystemTest.java b/src/test/java/com/github/marschall/memoryfilesystem/MemoryFileSystemTest.java
@@ -634,7 +634,7 @@ void probeContent() throws IOException {
   }
 
   @Test
-  void trasferFrom() throws IOException {
+  void trasferTo() throws IOException {
     FileSystem fileSystem = this.extension.getFileSystem();
 
     Path from = fileSystem.getPath("from.txt");
@@ -654,7 +654,7 @@ void trasferFrom() throws IOException {
   }
 
   @Test
-  void trasferTo() throws IOException {
+  void transferFromExpectedSize() throws IOException {
     FileSystem fileSystem = this.extension.getFileSystem();
 
     Path from = fileSystem.getPath("from.txt");
@@ -674,6 +674,27 @@ void trasferTo() throws IOException {
 
   }
 
+  @Test
+  void transferFromLarger() throws IOException {
+    FileSystem fileSystem = this.extension.getFileSystem();
+
+    Path from = fileSystem.getPath("from.txt");
+    Path to = fileSystem.getPath("to.txt");
+    byte[] content = "How could this be wrong?".getBytes(US_ASCII);
+    Files.write(from, content);
+    long expectedSize = content.length;
+    assertEquals(expectedSize, Files.size(from));
+
+    try (SeekableByteChannel fromChannel = Files.newByteChannel(from);
+         FileChannel toChannel = FileChannel.open(to, READ, WRITE, CREATE_NEW)) {
+      long count = toChannel.transferFrom(fromChannel, 0, content.length * 2);
+
+      assertEquals(expectedSize, count);
+    }
+    assertEquals(expectedSize, Files.size(to));
+    assertArrayEquals(content, Files.readAllBytes(to));
+  }
+
   private void writeBigContents(Path path) throws IOException {
     try (SeekableByteChannel channel = Files.newByteChannel(path, WRITE, CREATE_NEW)) {
       ByteBuffer src = ByteBuffer.wrap(SAMPLE_DATA);
@@ -1760,7 +1781,6 @@ void pathOrderingIncompatible() {
     assertThrows(ClassCastException.class, () -> a.compareTo(b));
   }
 
-
   @Test
   void createDirectories() throws IOException {
     FileSystem fileSystem = this.extension.getFileSystem();
@@ -1975,7 +1995,6 @@ void byteChannelDoubleClose() throws IOException {
     }
   }
 
-
   /**
    * Regression test for <a href="https://github.com/marschall/memoryfilesystem/issues/47">Issue 47</a>.
    */
@@ -1991,8 +2010,6 @@ void symLinkDirectory() throws IOException {
     Files.write(link.resolve("kid"), "hallo".getBytes(US_ASCII));
   }
 
-
-
   /**
    * Regression test for <a href="https://github.com/marschall/memoryfilesystem/issues/55">Issue 55</a>.
    */