77 lines
3.3 KiB
Racket
77 lines
3.3 KiB
Racket
#lang scribble/doc
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@(require "mz.rkt")
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@title[#:tag "stringport"]{String Ports}
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A @deftech{string port} reads or writes from a @tech{byte string}. An
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input @tech{string port} can be created from either a @tech{byte string} or a
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@tech{string}; in the latter case, the @tech{string} is effectively converted to
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a @tech{byte string} using @racket[string->bytes/utf-8]. An output @tech{string port}
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collects output into a @tech{byte string}, but @racket[get-output-string]
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conveniently converts the accumulated bytes to a @tech{string}.
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Input and output @tech{string ports} do not need to be explicitly
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closed. The @racket[file-position] procedure works for @tech{string
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ports} in position-setting mode.
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@defproc[(open-input-bytes [bstr bytes?] [name any/c 'string]) input-port?]{
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Creates an input @tech{string port} that reads characters from @racket[bstr] (see
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@secref["bytestrings"]). Modifying @racket[bstr] afterward does not
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affect the byte stream produced by the port. The optional
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@racket[name] argument is used as the name for the returned port.}
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@defproc[(open-input-string [str string?] [name any/c 'string]) input-port?]{
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Creates an input @tech{string port} that reads bytes from the UTF-8 encoding (see
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@secref["encodings"]) of @racket[str]. The optional @racket[name]
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argument is used as the name for the returned port.}
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@defproc[(open-output-bytes [name any/c 'string]) output-port?]{
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Creates an output @tech{string port} that accumulates the output into a byte
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string. The optional @racket[name] argument is used as the name for
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the returned port.}
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@defproc[(open-output-string [name any/c 'string]) output-port?]{The
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same as @racket[open-output-bytes].}
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@defproc[(get-output-bytes [out output-port?]
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[reset? any/c #f]
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[start-pos exact-nonnegative-integer? 0]
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[end-pos exact-nonnegative-integer? #f])
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bytes?]{
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Returns the bytes accumulated in the @tech{string port} @racket[out] so far in a
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freshly allocated @tech{byte string} (including any bytes written after the
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port's current position, if any). The @racket[out] port must be an
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output @tech{string port} produced by @racket[open-output-bytes] (or
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@racket[open-output-string]) or a structure whose
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@racket[prop:output-port] property refers to such an output port
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(transitively).
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If @racket[reset?] is true, then all bytes are removed from the port,
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and the port's position is reset to @racket[0]; if @racket[reset?] is
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@racket[#f], then all bytes remain in the port for further
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accumulation (so they are returned for later calls to
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@racket[get-output-bytes] or @racket[get-output-string]), and the
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port's position is unchanged.
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The @racket[start-pos] and @racket[end-pos] arguments specify the
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range of bytes in the port to return; supplying @racket[start-pos] and
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@racket[end-pos] is the same as using @racket[subbytes] on the result
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of @racket[get-output-bytes], but supplying them to
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@racket[get-output-bytes] can avoid an allocation. The
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@racket[end-pos] argument can be @racket[#f], which corresponds to not
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passing a second argument to @racket[subbytes].}
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@defproc[(get-output-string [out output-port?]) string?]{
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Returns @racket[(bytes->string/utf-8 (get-output-bytes out) #\?)].}
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@examples[
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(define i (open-input-string "hello world"))
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(define o (open-output-string))
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(write (read i) o)
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(get-output-string o)
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]
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