Adaptive data compression apparatus including run length encoding for a tape drive system

A data compression apparatus for efficiently compressing a user data block into a bit compressed data block for storage on a data storage medium comprising:

• means for dividing said user data block into a plurality of equal sized segments of data;
• means for compressing each of said segments of data independent of all other segments of data in said user data file comprising:
• means responsive to a received user data byte in one of said segments of data for determining whether said received user data byte is identical to the n previous data bytes, the last byte of a string or a single user data byte in said one segment of data;
• means responsive to said determining means for assigning one of a plurality of run length reference values to a user data byte that is identical to at least the n previous user data bytes, where n is an integer >2;
• means responsive to said determining means for assigning one of a plurality of byte compression reference values to a user data byte;
• means responsive to said determining means for assigning one of a plurality of string compression reference values to a suer data byte that comprises the last byte of a data string;
• means for writing each of said reference values successively received from said compressing means on to a data storage medium;
• means for storing each received data byte;
• means responsive to said storing means storing the last byte of said one segment of data for calculating the byte length of said reference values written on to said data storage medium representative of said one segment of data;
• and
• means responsive to said byte length exceeding the byte length of said one segment of data for writing said one segment of data in place of said reference values written on to said data storage medium.

A method of efficiently compressing a user data block into a bit compressed data block for storage on a data storage medium comprising the steps of:

• dividing said user data block into a plurality of equal sized segments of data;
• compressing each of said segments of data independent of all other segments of data in said user data block comprising:
• determining whether said received user data byte in one of said segments of data is identical to the n previous data bytes, the last byte of a string or a single user data byte in said one segment of data;
• assigning one of a plurality of run length reference values to a user data byte that is identical to at least the n previous user data bytes, where n is an integer >2;
• assigning one of a plurality of byte compression reference values to a user data byte;
• assigning one of a plurality of string compression reference values to a user data byte that comprises the last byte of a data string;
• and
• writing each of said reference values successively received from said compressing means on to a data storage medium.

A method of efficiently compressing a user data block into a bit compressed data block for storage on a data storage medium comprising the steps of:

• dividing said user data block into a plurality of equal sized segments of data;
• compressing each of said segments of data independent of all other segments of data in said user data block comprising:
• determining in response to a received user data byte in one of said segments of data whether said received user data byte is identical to the n previous data bytes;
• the last byte of a string or a single user data byte in said one segment of data;
• assigning one of a plurality of run length reference values to a user data byte that is identical to at least the n previous user data bytes, where n is an integer >2;
• assigning one of a plurality of byte compression reference values to a user data byte;
• assigning one of a plurality of string compression reference values to a user data byte that comprises the last byte of a data string;
• writing each of said reference values successively received from said compressing means on to a data storage medium;
• storing each received data byte;
• calculating, in response to said storing means storing the last byte of said one segment of data, the byte length of said reference values written on to said data storage medium representative of said one segment of data;
• and
• writing, in response to said byte length exceeding the byte length of said one segment of data, said one segment of data in place of said reference values written on to said data storage medium.