JCL Help:ReverseBits@Byte
JCL Help: ReverseBits Function
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Summary
Reverses the bits of Value.
Pascal
function ReverseBits(Value: Byte): Byte; overload;
function ReverseBits(Value: Shortint): Shortint; overload;
function ReverseBits(Value: Smallint): Smallint; overload;
function ReverseBits(Value: Word): Word; overload;
function ReverseBits(Value: Integer): Integer; overload;
function ReverseBits(Value: Cardinal): Cardinal; overload;
function ReverseBits(Value: Int64): Int64; overload;
function ReverseBits(P: Pointer; Count: Integer): Pointer; overload;
Parameters
| Parameters | Description |
| Value: Byte | The integer type whose bits to reverse. |
| P: Pointer | Address of a buffer whose bits to reverse. |
| Count: Integer | Size of the buffer, in bytes, specified by P. |
Return Value
Copy of Value with it's bits reversed.
Description
ReverseBits reverses the bits in the passed parameter. That is, assuming a byte, bit 0 is swapped with bit 7, bit 1 is swapped with bit 6 and so on. This function exists in 5 forms, one for each Integer type. The last overload is a generalisation of this which reverses the bits in the supplied buffer. Note that all overloads use a table based approach to reversing the bits. The simple types overloads use only a 15 byte table while the pointer overload uses a 255 byte table. Due to this the pointer overload is much faster when used on large buffers.
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Notes
Warning Keep in mind that some of the ReverseBits overloads accept signed integers as their argument but that reversing the bits of a signed integer is somewhat akward. Be sure that you understand the meaning of reversing the bits in a signed integer and that's what you want. The pointer returned by the Pointer overload points to the same buffer passed in as it's argument, iow it's not a newly allocated buffer. The ReverseBits(Pointer, Integer) overload was originally written by Mike Lischke. Reversing is not the same as toggling. To toggle bits use the ToggleBit function.
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