27.2.16 Replicate and rotate

Function: %xsubbytevector-s8 from to str start past

Function: %xsubbytevector-u8 from to str start past

Macro: xsubbytevector-s8 S from to

Macro: xsubbytevector-u8 S from to

Extended subvector procedure replicating the selected subvector “up and down” index space, in both the positive and negative directions.

The call:

(%xsubstring from to 'vu8(0 1 2 3 4 5 6) 3 6)

selects the subvector 3 4 5 and defines the conceptual bidirectionally–infinite bytevector:

...  4  5  3  4  5  3  4  5  3  4  5 ...
... -5 -4 -3 -2 -1  0 +1 +2 +3 +4 +5 ...
                    ^

that is 3 4 5 repeated in both directions. This function returns the subvector of this bytevector beginning at index from, and ending at to.

Note that:

• The from/to indices give a half–open range; the bytes from index from up to, but not including, index to.
• The from/to indices are not in terms of the index space for the bytevector bv. They are in terms of the replicated index space of the subvector defined by bv, start, and past.

It is an error if start equals past.

Function: xbytevector-s8-xcopy! from to target target-start source source-start source-past

Function: xbytevector-u8-xcopy! from to target target-start source source-start source-past

Macro: bytevector-s8-xcopy! target-B source-B from to

Macro: bytevector-u8-xcopy! target-B source-B from to

Exactly the same as %xsubbytevector-u8, but the extracted data is written into the selected subvector of target.

This operation is not defined if (eq? target start); we cannot copy a bytevector on top of itself.