Class that implements Lempel-Ziv compression.
LZ compression, also known as sliding window compression, uses redundancy to compress data. As input data is read, a dictionary of previous data is kept in memory. If a string of characters in the input data matches an entry in the dictionary, a code pointing to the dictionary entry is written to the output. If a match is not found in the dictionary the plain character is sent to the output.
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Procedure Name
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Type
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Description
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(Declarations)
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Declarations
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Declarations and private variables for the CLZ class
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InputFileName
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Property
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Sets the name of the input file
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OutputFileName
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Property
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Gets the name of the output file
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BitSetByte
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Private
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Sets a bit in a byte variable
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BufLength
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Private
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Returns the length of an entry
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BufPosition
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Private
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Returns the window position of an entry
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Compress
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Method
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Compresses the input file to the output file
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CompressionInitialize
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Private
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Initializes the module variables for the compression and decompression routines
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CompressString
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Method
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Compresses an input string
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dblToLong
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Private
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Performs an unsigned conversion from a Double value to a Long value.
This function correctly handles doubles greater than 2,147,483,647 and less than or equal to 4,294,967,295.
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Decompress
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Method
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Decompresses the input file to the output file
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DecompressString
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Method
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Decompresses a string that was previously compressed with the CompressString method of this class
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DeletePosition
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Private
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Removes a character from the window
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FindMatch
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Private
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Searches for a match in the window
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HiByte
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Private
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Returns the high byte of the passed integer
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HiWord
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Private
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Returns the high integer of the passed long
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InsertPosition
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Private
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Insert a character into the window
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IntToByte
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Private
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Perform an unsigned conversion from an integer value to a byte. This handles any integer value.
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IntToLong
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Private
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This routine converts an integer value to a long value, treating the integer as unsigned.
For example, performing the following assignment
lngNumber = -1
assigns -1 to the variable lngNumber. However, This assignment
lngNumber = IntToLong(-1)
assigns 65,535 to lngNumber.
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LoByte
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Private
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Returns the low byte of the passed integer
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LongToInt
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Private
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This routine does an unsigned conversion from a long value to an integer value.
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LoWord
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Private
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Returns the low integer of the passed long
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Shlb
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Private
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Shifts a numeric value left the specified number of bits.
Left shifting can be defined as a multiplication operation. For the number of bits we want to shift a value to the left, we need to raise two to that power, then multiply the result by our original value.
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Shli
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Private
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Shifts a numeric value left the specified number of bits.
Left shifting can be defined as a multiplication operation. For the number of bits we want to shift a value to the left, we need to raise two to that power, then multiply the result by our original value.
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Shll
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Private
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Shifts a numeric Value left the specified number of bits.
Left shifting can be defined as a multiplication operation. For the number of bits we want to shift a value to the left, we need to raise two to that power, then multiply the result by our original value.
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Shri
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Private
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Shifts a Long value right the selected number of places.
Right shifting can be defined as a division operation. For the number of bits we want to shift a value to the right, we need to raise two to that power, then our original value by the result
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WriteBufferByte
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Private
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Writes a single byte to the output buffer
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WriteBufferEntry
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Private
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Writes a window entry to the output buffer
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WriteBufferFinish
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Private
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Flushes any remaining data to the output buffer
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WriteByte
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Private
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Writes a single byte to the output file
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WriteEntry
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Private
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Writes a window entry to the output file
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WriteFinish
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Private
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Flushes any remaining data to the output file
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