ObjectInputStream.read(byte[], int, int) missing data?

Question

I'm trying to serialize/deserialize a bitmap. The answers at android how to save a bitmap - buggy code are very helpful. However, when I go to read my array:

private void readObject(ObjectInputStream in) throws IOException,
    ClassNotFoundException {
  int rowBytes = in.readInt();
  int height = in.readInt();
  int width = in.readInt();
  int bmSize = rowBytes * height;    // Ends up being 398208

  ByteBuffer byteBuffer = ByteBuffer.allocate(bmSize);
  int bytesRead = in.read(byteBuffer.array(), 0, bmSize);
  // Use array to create bitmap here
}

it is reading 1008 bytes, not the 398208 bytes that I wrote. I've replaced the call with a loop, which works fine:

for (int i = 0; i < bmSize; i++) {
  byteBuffer.array()[i] = in.readByte();
}

What could be going wrong? No exception is thrown. The documentation for ObjectInputStream.read(byte[], int, int) indicates the only reason it should return early is if it hits the end of the stream, which clearly it isn't because my work-around doesn't throw any exceptions.

why are not you using loop if its work fine.its not necessary that it read all data at once — Tofeeq Ahmad
– Tofeeq Ahmad, Commented May 4, 2012 at 4:56
The loop works fine, I just wanted to know why the built-in method wasn't working. Also I suspect the appropriate method will be faster - it might be able to use native calls, etc. — Brad
– Brad, Commented May 6, 2012 at 3:00

dagalpin · Accepted Answer · 2012-05-04 04:38:20Z

2

The documentation is wrong. ObjectInputStream just calls inputStream to read the bytes. Use readFully if you want it to block until the data is read.

answered May 4, 2012 at 4:38

dagalpin

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2 Comments

user207421 Over a year ago

+1. The Google documentation is not only wrong but meaningless. It says it blocks until count bytes have been read without defining count. The Java Javadoc is correct.

Brad Over a year ago

Many (many) thanks! I've posted updated documentation at android-review.googlesource.com/#/c/36320.

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