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reference clarifications on string ports

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Closes PR 12365
This commit is contained in:
Matthew Flatt 2011-11-26 16:59:05 -07:00
parent 48d5d6fca3
commit 1175964a78
2 changed files with 26 additions and 18 deletions
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17
collects/scribblings/reference/port-buffers.scrbl
View File

@ -81,26 +81,27 @@ If @racket[mode] is not provided, the current mode is returned, or
Returns or sets the current read/write position of @racket[port].
Calling @racket[file-position] without a position on a
non-file/non-string input port returns the number of bytes that have
Calling @racket[file-position] without a position on a port other
than a @tech{file-stream port} or @tech{string port}
returns the number of bytes that have
been read from that port if the position is known (see
@secref["linecol"]), otherwise the @exnraise[exn:fail:filesystem].
For @tech{file-stream ports} and string ports, the position-setting
For @tech{file-stream ports} and @tech{string ports}, the position-setting
variant sets the read/write position to @racket[pos] relative to the
beginning of the file/string if @racket[pos] is a number, or to the
current end of the file/string if @racket[pos] is @racket[eof]. In
beginning of the file or (byte) string if @racket[pos] is a number, or to the
current end of the file or (byte) string if @racket[pos] is @racket[eof]. In
position-setting mode, @racket[file-position] raises the
@racket[exn:fail:contract] exception for port kinds other than
file-stream and string ports. Furthermore, not all @tech{file-stream
@tech{file-stream ports} and @tech{string ports}. Furthermore, not all @tech{file-stream
ports} support setting the position; if @racket[file-position] is
called with a position argument on such a @tech{file-stream port}, the
@exnraise[exn:fail:filesystem].
When @racket[file-position] sets the position @racket[pos] beyond the
current size of an output file or string, the file/string is enlarged
current size of an output file or (byte) string, the file/string is enlarged
to size @racket[pos] and the new region is filled with @racket[0]
bytes. If @racket[pos] is beyond the end of an input file or string,
bytes. If @racket[pos] is beyond the end of an input file or (byte) string,
then reading thereafter returns @racket[eof] without changing the
port's position.

27
collects/scribblings/reference/string-ports.scrbl
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@ -3,26 +3,33 @@
@title[#:tag "stringport"]{String Ports}
String input and output ports do not need to be explicitly closed. The
@racket[file-position] procedure works for string ports in
position-setting mode.
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.
@defproc[(open-input-bytes [bstr bytes?] [name any/c 'string]) input-port?]{
Creates an input port that reads characters from @racket[bstr] (see
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.}
@defproc[(open-input-string [str string?] [name any/c 'string]) input-port?]{
Creates an input port that reads bytes from the UTF-8 encoding (see
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.}
@defproc[(open-output-bytes [name any/c 'string]) output-port?]{
Creates an output port that accumulates the output into a byte
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.}
@ -35,10 +42,10 @@ same as @racket[open-output-bytes].}
[end-pos exact-nonnegative-integer? #f])
bytes?]{
Returns the bytes accumulated in @racket[out] so far in a
freshly allocated byte string (including any bytes written after the
port's current position, if any). The @racket[out] port must be a
string output port produced by @racket[open-output-bytes] (or
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).