Ns_ConnReturnOpenFd(3) Routines to send open file content

Other Alias

Ns_ConnReturnOpenChannel, Ns_ConnReturnFdEx, Ns_ConnReturnOpenFile


#include "ns.h"

Ns_ConnReturnOpenChannel(conn, status, type, chan, len)

Ns_ConnReturnOpenFd(conn, status, type, fd, len)

Ns_ConnReturnOpenFdex(conn, status, type, fd, off, len)

Ns_ConnReturnOpenFile(conn, status, type, fp, len)


Tcl_Channel    chan    (in)
Pointer to Tcl_Channel open for read.
Ns_Conn    conn    (in)
Pointer to open connection.
FILE    *fp    (in)
Pointer to stdio FILE open for read.
off_t    off    (in)
Seek offset.
int    fd    (int)
File descriptor open for read.
int    status    (in)
HTTP status code.
char    *type    (in)
Pointer to mimetype string.


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 status code, a content-type header with the given type, and a content-length header with the length specified by len. No character output encoding or gzip compression is performed on the content.

For Ns_ConnReturnOpenFdEx, copying begins at the offset specified by the off 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.


Windows Support
The Ns_ConnReturnOpenFdEx routine is not currently supported on Windows. When called on Windows, it will always return NS_ERROR.

Truncated Result
The server will construct a content-length header based on the given len argument. However, the server will send the content with an underlying call to a cooresponding Ns_ConnSend function, e.g., Ns_ConnSendFd for Ns_ConnReturnOpenFd. 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 content-length 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 len to supress the content-length header entirely. Most browsers will accept this resonse and simply calculate the length from the bytes receieved up until the socket is closed.

Performance Consideration
As mentioned, these routines use underlying Ns_ConnSendFd 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 Ns_ConnReturnFile 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.


connnection, response, file