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><H1
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>php_stream_make_seekable</H1
><DIV
CLASS="refnamediv"
><A
NAME="AEN252871"
></A
>php_stream_make_seekable -- Convert a stream into a stream is seekable</DIV
><DIV
CLASS="refsect1"
><A
NAME="AEN252874"
></A
><H2
>Description</H2
>int <B
CLASS="methodname"
>php_stream_make_seekable</B
> ( php_stream * origstream, php_stream ** newstream, int flags )<BR
></BR
><P
> <B
CLASS="function"
>php_stream_make_seekable()</B
> checks if <CODE
CLASS="parameter"
>origstream</CODE
> is
seekable. If it is not, it will copy the data into a new temporary stream.
If successful, <CODE
CLASS="parameter"
>newstream</CODE
> is always set to the stream that is valid to use, even if the original
stream was seekable.
</P
><P
> <CODE
CLASS="parameter"
>flags</CODE
> allows you to specify your preference for the seekable stream that is
returned: use <TT
CLASS="constant"
><B
>PHP_STREAM_NO_PREFERENCE</B
></TT
> to use the default seekable stream
(which uses a dynamically expanding memory buffer, but switches to temporary file backed storage
when the stream size becomes large), or use <TT
CLASS="constant"
><B
>PHP_STREAM_PREFER_STDIO</B
></TT
> to
use "regular" temporary file backed storage.
</P
><P
> <DIV
CLASS="table"
><A
NAME="AEN252897"
></A
><P
><B
>表 44-1. <B
CLASS="function"
>php_stream_make_seekable()</B
> return values</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><THEAD
><TR
><TH
>Value</TH
><TH
>Meaning</TH
></TR
></THEAD
><TBODY
><TR
><TD
>PHP_STREAM_UNCHANGED</TD
><TD
>Original stream was seekable anyway. <CODE
CLASS="parameter"
>newstream</CODE
> is set to the value
of <CODE
CLASS="parameter"
>origstream</CODE
>.
</TD
></TR
><TR
><TD
>PHP_STREAM_RELEASED</TD
><TD
>Original stream was not seekable and has been released. <CODE
CLASS="parameter"
>newstream</CODE
> is set to the
new seekable stream. You should not access <CODE
CLASS="parameter"
>origstream</CODE
> anymore.
</TD
></TR
><TR
><TD
>PHP_STREAM_FAILED</TD
><TD
>An error occurred while attempting conversion. <CODE
CLASS="parameter"
>newstream</CODE
> is set to NULL;
<CODE
CLASS="parameter"
>origstream</CODE
> is still valid.
</TD
></TR
><TR
><TD
>PHP_STREAM_CRITICAL</TD
><TD
>An error occurred while attempting conversion that has left <CODE
CLASS="parameter"
>origstream</CODE
> in
an indeterminate state. <CODE
CLASS="parameter"
>newstream</CODE
> is set to NULL and it is highly recommended
that you close <CODE
CLASS="parameter"
>origstream</CODE
>.
</TD
></TR
></TBODY
></TABLE
></DIV
>
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
If you need to seek and write to the stream, it does not make sense to use this function, because the stream
it returns is not guaranteed to be bound to the same resource as the original stream.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
If you only need to seek forwards, there is no need to call this function, as the streams API will emulate
forward seeks when the whence parameter is <TT
CLASS="constant"
><B
>SEEK_CUR</B
></TT
>.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
If <CODE
CLASS="parameter"
>origstream</CODE
> is network based, this function will block until the whole contents
have been downloaded.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
NEVER call this function with an <CODE
CLASS="parameter"
>origstream</CODE
> that is reference by a file pointer
in a PHP script! This function may cause the underlying stream to be closed which could cause a crash
when the script next accesses the file pointer!
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>注意: </B
>
In many cases, this function can only succeed when <CODE
CLASS="parameter"
>origstream</CODE
> is a newly opened
stream with no data buffered in the stream layer. For that reason, and because this function is complicated to
use correctly, it is recommended that you use <B
CLASS="function"
>php_stream_open_wrapper()</B
> and pass in
<TT
CLASS="constant"
><B
>PHP_STREAM_MUST_SEEK</B
></TT
> in your options instead of calling this function directly.
</P
></BLOCKQUOTE
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