Class ByteArrayCombinerStream

java.lang.Object
java.io.InputStream
org.apache.derby.client.am.ByteArrayCombinerStream
All Implemented Interfaces:
Closeable, AutoCloseable

public class ByteArrayCombinerStream extends InputStream
A stream whose source is a list of byte arrays. This class was created when first implementing the JDBC 4 length less overloads in the client driver. The reason was missing support for streaming data with unknown length from the client to the server. The purpose of the stream is to avoid having to repeatedly copy data to grow the byte buffer, or doing a single big copy to combine the byte arrays in the end. This is important for the temporary solution, since we must materialize the stream to find the length anyway. If there is less data available than the specified length, an exception is thrown. Available data is determined by the length of the byte arrays, not the contents of them. A byte array with all 0's is considered valid data. Besides from truncation, this stream does not change the underlying data in any way.
  • Field Details

    • arrays

      private final ArrayList<byte[]> arrays
      A list of the arrays to combine.
    • specifiedLength

      private final long specifiedLength
      Length of the stream.
    • gOffset

      private long gOffset
      Global offset into the whole stream.
    • arrayIndex

      private int arrayIndex
      Index of the array we are currently reading from.
    • curArray

      private byte[] curArray
      The array we are currently reading from.
    • off

      private int off
      The local offset into the current array.
  • Constructor Details

    • ByteArrayCombinerStream

      public ByteArrayCombinerStream(ArrayList<byte[]> arraysIn, long length)
      Create a stream whose source is a list of byte arrays.
      Parameters:
      arraysIn - an ArrayList with references to the source byte arrays. The references are copied to a new ArrayList instance.
      length - the length of the stream. Never published outside this object. Note that the length specified can be shorter than the actual number of bytes in the byte arrays.
      Throws:
      IllegalArgumentException - if there is less data available than specified by length, or length is negative.
  • Method Details

    • read

      public int read() throws IOException
      Read a single byte.
      Specified by:
      read in class InputStream
      Returns:
      a byte, or -1 if the end-of-stream is reached
      Throws:
      IOException
    • read

      public int read(byte[] buf, int offset, int length) throws IOException
      Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read. The number of bytes actually read is returned as an integer.
      Overrides:
      read in class InputStream
      Parameters:
      buf - the array to copy bytes into
      offset - offset into the array
      length - the maximum number of bytes to read
      Returns:
      the number of bytes read, or -1 if end-of-stream is reached
      Throws:
      IOException
    • available

      public int available()
      Return the number of available bytes. The method assumes the specified length of the stream is correct.
      Overrides:
      available in class InputStream
      Returns:
      number of available bytes
    • nextArray

      private byte[] nextArray()
      Fetch the next array to read data from. The reference in the ArrayList is cleared when the array is "taken out".
      Returns:
      a byte[]-object, or null if there are no more arrays