140 lines
4.8 KiB
Racket
140 lines
4.8 KiB
Racket
#lang scribble/doc
|
|
@(require "mz.rkt")
|
|
|
|
@(define sp-eval (make-base-eval))
|
|
@(interaction-eval #:eval sp-eval (require racket/list))
|
|
|
|
@title[#:tag "stringport"]{String Ports}
|
|
|
|
A @deftech{string port} reads or writes from a @tech{byte string}. An
|
|
input @tech{string port} can be created from either a @tech{byte string}
|
|
or a @tech{string}; in the latter case, the @tech{string} is effectively
|
|
converted to a @tech{byte string} using @racket[string->bytes/utf-8]. An
|
|
output @tech{string port} collects output into a @tech{byte string}, but
|
|
@racket[get-output-string] conveniently converts the accumulated bytes
|
|
to a @tech{string}.
|
|
|
|
Input and output @tech{string ports} do not need to be explicitly
|
|
closed. The @racket[file-position] procedure works for @tech{string
|
|
ports} in position-setting mode.
|
|
|
|
@refalso["bytestrings"]{bytestrings}
|
|
|
|
@defproc[(open-input-bytes [bstr bytes?] [name any/c 'string]) input-port?]{
|
|
|
|
Creates an input @tech{string port} that reads characters from
|
|
@racket[bstr] (see @secref["bytestrings"]). Modifying @racket[bstr]
|
|
afterward does not affect the byte stream produced by the port. The
|
|
optional @racket[name] argument is used as the name for the returned
|
|
port.}
|
|
|
|
@examples[#:eval sp-eval
|
|
(define sp (open-input-bytes #"(apples 42 day)"))
|
|
(define sexp1 (read sp))
|
|
(first sexp1)
|
|
(rest sexp1)
|
|
(read-line (open-input-bytes
|
|
#"the cow jumped over the moon\nthe little dog\n"))
|
|
]
|
|
|
|
@refalso["strings"]{strings}
|
|
|
|
@defproc[(open-input-string [str string?] [name any/c 'string]) input-port?]{
|
|
|
|
Creates an input @tech{string port} that reads bytes from the UTF-8
|
|
encoding (see @secref["encodings"]) of @racket[str]. The optional
|
|
@racket[name] argument is used as the name for the returned port.}
|
|
|
|
@examples[#:eval sp-eval
|
|
(define sp (open-input-string "(λ (x) x)"))
|
|
(read sp)
|
|
(define names (open-input-string "Günter Harder\nFrédéric Paulin\n"))
|
|
(read-line names)
|
|
(read-line names)]
|
|
|
|
@defproc[(open-output-bytes [name any/c 'string]) output-port?]{
|
|
|
|
Creates an output @tech{string port} that accumulates the output into a
|
|
byte string. The optional @racket[name] argument is used as the name for
|
|
the returned port.}
|
|
|
|
@examples[ #:eval sp-eval
|
|
(define op1 (open-output-bytes))
|
|
(write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op1)
|
|
(get-output-bytes op1)
|
|
(define op2 (open-output-bytes))
|
|
(write "Hi " op2)
|
|
(write "there" op2)
|
|
(get-output-bytes op2)
|
|
(define op3 (open-output-bytes))
|
|
(write-bytes #"Hi " op3)
|
|
(write-bytes #"there" op3)
|
|
(get-output-bytes op3)
|
|
]
|
|
|
|
@defproc[(open-output-string [name any/c 'string]) output-port?]{The
|
|
same as @racket[open-output-bytes].}
|
|
|
|
@examples[ #:eval sp-eval
|
|
(define op1 (open-output-string))
|
|
(write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op1)
|
|
(get-output-string op1)
|
|
(define op2 (open-output-string))
|
|
(write "Hi " op2)
|
|
(write "there" op2)
|
|
(get-output-string op2)
|
|
(define op3 (open-output-string))
|
|
(write-string "Hi " op3)
|
|
(write-string "there" op3)
|
|
(get-output-string op3)
|
|
]
|
|
|
|
@defproc[(get-output-bytes [out output-port?]
|
|
[reset? any/c #f]
|
|
[start-pos exact-nonnegative-integer? 0]
|
|
[end-pos exact-nonnegative-integer? #f])
|
|
bytes?]{
|
|
|
|
Returns the bytes accumulated in the @tech{string port} @racket[out] so
|
|
far in a freshly allocated @tech{byte string} (including any bytes
|
|
written after the port's current position, if any). The @racket[out]
|
|
port must be an output @tech{string port} produced by
|
|
@racket[open-output-bytes] (or @racket[open-output-string]) or a
|
|
structure whose @racket[prop:output-port] property refers to such an
|
|
output port (transitively).
|
|
|
|
If @racket[reset?] is true, then all bytes are removed from the port,
|
|
and the port's position is reset to @racket[0]; if @racket[reset?] is
|
|
@racket[#f], then all bytes remain in the port for further
|
|
accumulation (so they are returned for later calls to
|
|
@racket[get-output-bytes] or @racket[get-output-string]), and the
|
|
port's position is unchanged.
|
|
|
|
The @racket[start-pos] and @racket[end-pos] arguments specify the
|
|
range of bytes in the port to return; supplying @racket[start-pos] and
|
|
@racket[end-pos] is the same as using @racket[subbytes] on the result
|
|
of @racket[get-output-bytes], but supplying them to
|
|
@racket[get-output-bytes] can avoid an allocation. The
|
|
@racket[end-pos] argument can be @racket[#f], which corresponds to not
|
|
passing a second argument to @racket[subbytes].}
|
|
|
|
@examples[ #:eval sp-eval
|
|
(define op (open-output-bytes))
|
|
(write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op)
|
|
(get-output-bytes op)
|
|
(get-output-bytes op #f 3 16)
|
|
(get-output-bytes op #t)
|
|
(get-output-bytes op)]
|
|
|
|
@defproc[(get-output-string [out output-port?]) string?]{
|
|
Returns @racket[(bytes->string/utf-8 (get-output-bytes out) #\?)].}
|
|
|
|
@examples[
|
|
(define i (open-input-string "hello world"))
|
|
(define o (open-output-string))
|
|
(write (read i) o)
|
|
(get-output-string o)
|
|
]
|
|
|
|
@close-eval[sp-eval]
|