tested under Windows, and so it is currently off by default. This may be

changed in the future.

</para>

<para>

These functions leave the socket in a non-blocking state as if

<function>PQsetnonblocking</function> had been called.

</para>

<para>

These functions are not thread-safe.

</para>

Applications that do not like these limitations can instead use the

underlying functions that <function>PQexec</function> is built from:

<function>PQsendQuery</function> and <function>PQgetResult</function>.

</para>

<para>

Older programs that used this functionality as well as

<function>PQputline</function> and <function>PQputnbytes</function>

could block waiting to send data to the backend, to

address that issue, the function <function>PQsetnonblocking</function>

was added.

</para>

<para>

Old applications can neglect to use <function>PQsetnonblocking</function>

and get the older potentially blocking behavior. Newer programs can use

<function>PQsetnonblocking</function> to achieve a completely non-blocking

connection to the backend.

<itemizedlist>

<listitem>

<para>

<function>PQsetnonblocking</function> Sets the state of the connection

to non-blocking.

<synopsis>

int PQsetnonblocking(PGconn *conn)

</synopsis>

this function will ensure that calls to

<function>PQputline</function>, <function>PQputnbytes</function>,

<function>PQsendQuery</function> and <function>PQendcopy</function>

will not block but instead return an error if they need to be called

again.

</para>

<para>

When a database connection has been set to non-blocking mode and

<function>PQexec</function> is called, it will temporarily set the state

of the connection to blocking until the <function>PQexec</function>

completes.

</para>

<para>

More of libpq is expected to be made safe for

<function>PQsetnonblocking</function> functionality in the near future.

</para>

</listitem>

<listitem>

<para>

<function>PQisnonblocking</function>

Returns the blocking status of the database connection.

<synopsis>

int PQisnonblocking(const PGconn *conn)

</synopsis>

Returns TRUE if the connection is set to non-blocking mode,

FALSE if blocking.

</para>

</listitem>

<listitem>

<para>

<function>PQsendQuery</function>

</para>

</listitem>

<listitem>

<para>

<function>PQflush</function> Attempt to flush any data queued to the backend,

returns 0 if successful (or if the send queue is empty) or EOF if it failed for

some reason.

<synopsis>

int PQflush(PGconn *conn);

</synopsis>

<function>PQflush</function> needs to be called on a non-blocking connection

before calling <function>select</function> to determine if a responce has

arrived. If 0 is returned it ensures that there is no data queued to the

backend that has not actually been sent. Only applications that have used

<function>PQsetnonblocking</function> have a need for this.

</para>

</listitem>

<listitem>

<para>

<function>PQsocket</function>

Obtain the file descriptor number for the backend connection socket.

A valid descriptor will be>= 0; a result of -1 indicates that

A valid descriptor will be&gt;= 0; a result of -1 indicates that

no backend connection is currently open.

<synopsis>

int PQsocket(const PGconn *conn);

</synopsis>

<function>PQsocket</function> should be used to obtain the backend socket descriptor

in preparation for executing <function>select</function>(2). This allows an

application to wait for either backend responses or other conditions.

application using a blocking connection to wait for either backend responses or

other conditions.

If the result of <function>select</function>(2) indicates that data can be read from

the backend socket, then <function>PQconsumeInput</function> should be called to read the

data; after which, <function>PQisBusy</function>, <function>PQgetResult</function>,

and/or <function>PQnotifies</function> can be used to process the response.

</para>

<para>

Non-blocking connections (that have used <function>PQsetnonblocking</function>)

should not use <function>select</function> until <function>PQflush</function>

has returned 0 indicating that there is no buffered data waiting to be sent

to the backend.

</para>

</listitem>

</itemizedlist>

return0;

}

connectMakeNonblocking(PGconn*conn)

{

if (fcntl(conn->sock,F_SETFL,O_NONBLOCK)<0)

if (ioctlsocket(conn->sock,FIONBIO,&on)!=0)

{

printfPQExpBuffer(&conn->errorMessage,

"connectMakeNonblocking -- fcntl() failed: errno=%d\n%s\n",

errno,strerror(errno));

return0;

}

return1;

}

#if (!defined(WIN32)|| defined(WIN32_NON_BLOCKING_CONNECTIONS))&& !defined(USE_SSL)

if (!connectMakeNonblocking(conn))

if (PQsetnonblocking(conn, TRUE)!=0)

gotoconnect_errReturn;

#if (defined(WIN32)&& !defined(WIN32_NON_BLOCKING_CONNECTIONS))|| defined(USE_SSL)

if (!connectMakeNonblocking(conn))

if (PQsetnonblocking(conn, TRUE)!=0)

gotoconnect_errReturn;

conn->inBuffer= (char*)malloc(conn->inBufSize);

conn->outBufSize=8*1024;

conn->outBuffer= (char*)malloc(conn->outBufSize);

conn->nonblocking= FALSE;

initPQExpBuffer(&conn->errorMessage);

initPQExpBuffer(&conn->workBuffer);

if (conn->inBuffer==NULL||

conn->lobjfuncs=NULL;

conn->inStart=conn->inCursor=conn->inEnd=0;

conn->outCount=0;

conn->nonblocking= FALSE;

}