Packing and Unpacking Data in Java

WiredTiger's data packing uses format strings similar to those specified in the Python struct module: http://docs.python.org/library/struct

The first character of the format string can be used to indicate the byte order, size and alignment of the packed data, according to the following table:

Character	Byte order	Size	Alignment
.	big-endian	packed	none
>	big-endian	standard	none
<	little-endian	standard	none
@	native	native	native

If the first character is not one of these, '.' (big-endian, packed) is assumed: it naturally sorts in lexicographic order, and the packed format uses variable-sized encoding of values to reduce the data size.

Note: little-endian format not yet supported in WiredTiger. Only the default big-endian, packed format is currently supported.

The remaining characters in the format string specify the type of each field to be packed into or unpacked from a byte array. See Column types for the list of supported types.

In Java, data is packed and unpacked using cursor put* and get* operations, for example:

        /* Insert the records into the table. */
        cursor = session.open_cursor("table:poptable", null, "append");
        for (PopRecord p : popData) {
            cursor.putValueString(p.country);
            cursor.putValueShort(p.year);
            cursor.putValueLong(p.population);
            ret = cursor.insert();
        }
        ret = cursor.close();

        /* Update records in the table. */
        cursor = session.open_cursor("table:poptable", null, null);
        while ((ret = cursor.next()) == 0) {
            recno = cursor.getKeyRecord();
            country = cursor.getValueString();
            year = cursor.getValueShort();
            population = cursor.getValueLong();
            cursor.putValueString(country);
            cursor.putValueShort(year);
            cursor.putValueLong(population + 1);
        }
        ret = cursor.close();

        /* List the records in the table. */
        cursor = session.open_cursor("table:poptable", null, null);
        while ((ret = cursor.next()) == 0) {
            recno = cursor.getKeyRecord();
            country = cursor.getValueString();
            year = cursor.getValueShort();
            population = cursor.getValueLong();
            System.out.print("ID " + recno);
            System.out.println(": country " + country + ", year " + year +
                ", population " + population);
        }
        ret = cursor.close();