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'\" $Header: /cvsroot/aolserver/aolserver/doc/Ns_ConnReturnOpen.3,v 1.1 2006/04/19 17:37:30 jgdavidson Exp $
'\"
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.TH Ns_ConnReturnOpen 3aolserver 4.0 AOLserver "AOLserver Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Ns_ConnReturnOpenChannel, Ns_ConnReturnOpenFd, Ns_ConnReturnFdEx, Ns_ConnReturnOpenFile \- Routines to send open file content
.SH SYNOPSIS
.nf
\fB#include "ns.h"\fR
int
.sp
int
\fBNs_ConnReturnOpenChannel\fR(\fIconn, status, type, chan, len\fR)
.sp
int
\fBNs_ConnReturnOpenFd\fR(\fIconn, status, type, fd, len\fR)
.sp
int
\fBNs_ConnReturnOpenFdex\fR(\fIconn, status, type, fd, off, len\fR)
.sp
int
\fBNs_ConnReturnOpenFile\fR(\fIconn, status, type, fp, len\fR)
.SH ARGUMENTS
.AS Tcl_Channel chan in
.AP Tcl_Channel chan in
Pointer to Tcl_Channel open for read.
.AP Ns_Conn conn in
Pointer to open connection.
.AP FILE *fp in
Pointer to stdio FILE open for read.
.AP off_t off in
Seek offset.
.AP int fd int
File descriptor open for read.
.AP int status in
HTTP status code.
.AP char *type in
Pointer to mimetype string.
.BE

.SH DESCRIPTION
.PP
These routines are used to generate complete responses, including
headers, status codes, content types, and the content copied from
the given open file. They all return a status code which is NS_OK
if the response was sent or NS_ERROR if an underlying call to sent
the content failed.  The response will include the given HTTP
\fIstatus\fR code, a \fIcontent-type\fR header with the given
\fItype\fR, and a \fIcontent-length\fR header with the length
specified by \fIlen\fR.  No character output encoding or gzip
compression is performed on the content.
.PP
For \fBNs_ConnReturnOpenFdEx\fR, copying begins at the offset
specified by the \fIoff\fR argument
Otherwise,
these routines copy from the current read offset in the underlying
open file.  No attempt is made to serialize access to the underlying
object so independent open file objects and/or mutex locking is
necessary if the same file is being sent simultaneously to multiple
clients.

.SH NOTES
.TP
Windows Support
The \fBNs_ConnReturnOpenFdEx\fR routine is not currently supported
on Windows.  When called on Windows, it will always return NS_ERROR.

.TP
Truncated Result
The server will construct a \fIcontent-length\fR header based on
the given \fIlen\fR argument. However, the server will send the
content with an underlying call to a cooresponding \fBNs_ConnSend\fR
function, e.g., \fBNs_ConnSendFd\fR for \fBNs_ConnReturnOpenFd\fR.
These functions will send the requested content or all remaining
content in the open file if less bytes are avilable without reporting
an error due to the truncated response.  As the headers will have
already been flushed before sending the content in this case, the
\fIcontent-length\fR header will not be consistent with the actual
bytes sent.  If it is not possible to ensure the remaining bytes
will be equal or greater to the requested bytes to send, it is
possible to specify -1 for \fIlen\fR to supress the \fIcontent-length\fR
header entirely.  Most browsers will accept this resonse and simply
calculate the length from the bytes receieved up until the socket
is closed.

.TP
Performance Consideration
As mentioned, these routines use underlying \fBNs_ConnSendFd\fR
style routines to copy and send the content from open files.  This
is not the approach used by the builtin file-serving code (aka the
"fastpath").  The fastpath operates with filenames, not open file
objects, and maintains a cached of pre-read or memory mapped regions
to accelerate the common case of rapidly sending reasonably sized
content to multiple, simultaneous clients.  The \fBNs_ConnReturnFile\fR
routine utilizes the underlying fastpath and thus could be a faster
means to send static files than directly opening files and calling
these API's.

.SH "SEE ALSO"
Ns_ConnReturnFile(3), Ns_ConnFlush(3), Ns_ConnSendFd(3), Ns_ConnReturnData(3)

.SH KEYWORDS
connnection, response, file