</listitem>

</varlistentry>

<varlistentry id="libpq-PQsocketPoll">

<term><function>PQsocketPoll</function><indexterm><primary>PQsocketPoll</primary></indexterm></term>

<listitem>

<para>

<indexterm><primary>nonblocking connection</primary></indexterm>

Poll a connection&apos;s underlying socket descriptor retrieved with <xref linkend="libpq-PQsocket"/>.

<synopsis>

int PQsocketPoll(int sock, int forRead, int forWrite, time_t end_time);

</synopsis>

</para>

<para>

This function sets up polling of a file descriptor. The underlying function is either

<function>poll(2)</function> or <function>select(2)</function>, depending on platform

support. The primary use of this function is iterating through the connection sequence

described in the documentation of <xref linkend="libpq-PQconnectStartParams"/>. If

<parameter>forRead</parameter> is specified, the function waits for the socket to be ready

for reading. If <parameter>forWrite</parameter> is specified, the function waits for the

socket to be ready for write. See <literal>POLLIN</literal> and <literal>POLLOUT</literal>

from <function>poll(2)</function>, or <parameter>readfds</parameter> and

<parameter>writefds</parameter> from <function>select(2)</function> for more information. If

<parameter>end_time</parameter> is not <literal>-1</literal>, it specifies the time at which

this function should stop waiting for the condition to be met.

</para>

<para>

The function returns a value greater than <literal>0</literal> if the specified condition

is met, <literal>0</literal> if a timeout occurred, or <literal>-1</literal> if an error

occurred. The error can be retrieved by checking the <literal>errno(3)</literal> value. In

the event <literal>forRead</literal> and <literal>forWrite</literal> are not set, the

function immediately returns a timeout condition.

</para>

</listitem>

</varlistentry>

<varlistentry id="libpq-PQconnectStartParams">

<term><function>PQconnectStartParams</function><indexterm><primary>PQconnectStartParams</primary></indexterm></term>

<term><function>PQconnectStart</function><indexterm><primary>PQconnectStart</primary></indexterm></term>

Loop thus: If <function>PQconnectPoll(conn)</function> last returned

<symbol>PGRES_POLLING_READING</symbol>, wait until the socket is ready to

read (as indicated by <function>select()</function>, <function>poll()</function>, or

similar system function).

similar system function). Note that <function>PQsocketPoll</function>

can help reduce boilerplate by abstracting the setup of

<function>select(2)</function> or <function>poll(2)</function> if it is

available on your system.

Then call <function>PQconnectPoll(conn)</function> again.

Conversely, if <function>PQconnectPoll(conn)</function> last returned

<symbol>PGRES_POLLING_WRITING</symbol>, wait until the socket is ready

PQcancelErrorMessage 200

PQcancelReset 201

PQcancelFinish 202

PQsocketPoll 203

staticintpqSendSome(PGconn*conn,intlen);

staticintpqSocketCheck(PGconn*conn,intforRead,intforWrite,

time_tend_time);

staticintpqSocketPoll(intsock,intforRead,intforWrite,time_tend_time);

result=pqSocketPoll(conn->sock,forRead,forWrite,end_time);

result=PQsocketPoll(conn->sock,forRead,forWrite,end_time);

while (result<0&&SOCK_ERRNO==EINTR);

if (result<0)

pqSocketPoll(intsock,intforRead,intforWrite,time_tend_time)

PQsocketPoll(intsock,intforRead,intforWrite,time_tend_time)

{

externintPQlibVersion(void);

externintPQsocketPoll(intsock,intforRead,intforWrite,time_tend_time);

externintPQmblen(constchar*s,intencoding);