Bytevectors represent blocks of binary data. They are
fixed-length sequences of bytes, where a byte
is an exact
integer in the range [0, 255]. A bytevector is typically more
space-efficient than a vector containing the same values.
The length of a bytevector is the number of elements that it contains. This number is a non-negative integer that is fixed when the bytevector is created. The valid indexes of a bytevector are the exact non-negative integers less than the length of the bytevector, starting at index zero as with vectors.
The bytevector
type is equivalent to the u8vector
uniform vector type, but is specified
by the R7RS standard.
Bytevectors are written using the notation #u8(byte . . . )
.
For example, a bytevector of length 3 containing the byte
0 in element 0, the byte 10 in element 1, and the byte 5 in
element 2 can be written as following:
#u8(0 10 5)
Bytevector constants are self-evaluating, so they do not need to be quoted in programs.
The type of bytevector objects.
Constructor: bytevector
byte
…
Return a newly allocated bytevector whose elements contain the given arguments. Analogous to
vector
.(bytevector 1 3 5 1 3 5) ⇒ #u8(1 3 5 1 3 5) (bytevector) ⇒ #u8()
Return
#t
ifobj
is a bytevector,#f
otherwise.
Procedure: make-bytevector
k
byte
The
make-bytevector
procedure returns a newly allocated bytevector of lengthk
. Ifbyte
is given, then all elements of the bytevector are initialized tobyte
, otherwise the contents of each element are unspecified.(make-bytevector 2 12) ⇒ #u8(12 12)
Procedure: bytevector-length
bytevector
Returns the length of
bytevector
in bytes as an exact integer.
Procedure: bytevector-u8-ref
bytevector
k
It is an error if
k
is not a valid index ofbytevector
. Returns thek
th byte ofbytevector
.(bytevector-u8-ref ’#u8(1 1 2 3 5 8 13 21) 5) ⇒ 8
Procedure: bytevector-u8-set!
bytevector
k
byte
It is an error if
k
is not a valid index ofbytevector
. Storesbyte
as thek
th byte ofbytevector
.(let ((bv (bytevector 1 2 3 4) (bytevector-u8-set! bv 1 3) bv) ⇒ #u8(1 3 3 4)
Procedure: bytevector-copy
bytevector
[start
[end
]]
Returns a newly allocated bytevector containing the bytes in
bytevector
betweenstart
andend
.(define a #u8(1 2 3 4 5)) (bytevector-copy a 2 4)) ⇒ #u8(3 4)
Procedure: bytevector-copy!
to
at
from
[start
[end
]]
Copies the bytes of bytevector
from
betweenstart
andend
to bytevectorto
, starting atat
. The order in which bytes are copied is unspecified, except that if the source and destination overlap, copying takes place as if the source is first copied into a temporary bytevector and then into the destination. This is achieved without allocating storage by making sure to copy in the correct direction in such circumstances.It is an error if
at
is less than zero or greater than the length ofto
. It is also an error if(- (bytevector-length
is less thanto
)at
)(-
.end
start
)(define a (bytevector 1 2 3 4 5)) (define b (bytevector 10 20 30 40 50)) (bytevector-copy! b 1 a 0 2) b ⇒ #u8(10 1 2 40 50)
Procedure: bytevector-append
bytevector...
Returns a newly allocated bytevector whose elements are the concatenation of the elements in the given bytevectors.
(bytevector-append #u8(0 1 2) #u8(3 4 5)) ⇒ #u8(0 1 2 3 4 5)
Procedure: utf8->string
bytevector
[start
[end
]]
This procedure decodes the bytes of a bytevector between
start
andend
, interpreting as a UTF-8-encoded string, and returns the corresponding string. It is an error forbytevector
to contain invalid UTF-8 byte sequences.(utf8->string #u8(#x41)) ⇒ "A"
Procedure: string->utf8
string
[start
[end
]]
This procedure encodes the characters of a string between
start
andend
and returns the corresponding bytevector, in UTF-8 encoding.(string->utf8 "λ") ⇒ " #u8(#xCE #xBB)