Function SetClientEncoding

src/backend/utils/mb/mbutils.c:209–276

* Set the active client encoding and set up the conversion-function pointers. * PrepareClientEncoding should have been called previously for this encoding. * * Returns 0 if okay, -1 if not (bad encoding or can't support conversion) */

 * Returns 0 if okay, -1 if not (bad encoding or can't support conversion)
 */
int
SetClientEncoding(int encoding)
{
	int			current_server_encoding;
	bool		found;
	ListCell   *lc;

	if (!PG_VALID_FE_ENCODING(encoding))
		return -1;

	/* Can't do anything during startup, per notes above */
	if (!backend_startup_complete)
	{
		pending_client_encoding = encoding;
		return 0;
	}

	current_server_encoding = GetDatabaseEncoding();

	/*
	 * Check for cases that require no conversion function.
	 */
	if (current_server_encoding == encoding ||
		current_server_encoding == PG_SQL_ASCII ||
		encoding == PG_SQL_ASCII)
	{
		ClientEncoding = &pg_enc2name_tbl[encoding];
		ToServerConvProc = NULL;
		ToClientConvProc = NULL;
		return 0;
	}

	/*
	 * Search the cache for the entry previously prepared by
	 * PrepareClientEncoding; if there isn't one, we lose.  While at it,
	 * release any duplicate entries so that repeated Prepare/Set cycles don't
	 * leak memory.
	 */
	found = false;
	foreach(lc, ConvProcList)
	{
		ConvProcInfo *convinfo = (ConvProcInfo *) lfirst(lc);

		if (convinfo->s_encoding == current_server_encoding &&
			convinfo->c_encoding == encoding)
		{
			if (!found)
			{
				/* Found newest entry, so set up */
				ClientEncoding = &pg_enc2name_tbl[encoding];
				ToServerConvProc = &convinfo->to_server_info;
				ToClientConvProc = &convinfo->to_client_info;
				found = true;
			}
			else
			{
				/* Duplicate entry, release it */
				ConvProcList = foreach_delete_current(ConvProcList, lc);