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As mentioned, the offset contained in the lower five bits of
the command byte allows for offset values from 0 to 31.
Compression mode allows offsets larger than 31 bytes as
follows:
An offset value of 0-30 indicates that the replacement
bytes are offset from the 1st byte to the 31st byte.
A value of 31 indicates that the next byte following the
command byte is an additional offset byte which adds to
the first (32) offset value. This allows offset values larger
than 31. Also, if this second offset byte is set to 255 (all
ones), additional offset bytes follow until the required
offset value is obtained. When the formatter detects an
offset byte less than 255, it is assumed to be the last
offset value and the offset bytes are then totaled (added).
The following example shows an offset larger than 31:
The total offset is 414, which is the sum of the three offset
values: 31 + 255 + 128.
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