C++ MemSet函数代码示例

//.........这里部分代码省略.........
		 * This loop is called once for every attribute of every tuple in the
		 * page.  At the start of a tuple, we get a NULL dtup; that's our
		 * signal for obtaining and decoding the next one.  If that's not the
		 * case, we output the next attribute.
		 */
		if (state->dtup == NULL)
		{
			BrinTuple	   *tup;
			MemoryContext mctx;
			ItemId		itemId;

			/* deformed tuple must live across calls */
			mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

			/* verify item status: if there's no data, we can't decode */
			itemId = PageGetItemId(state->page, state->offset);
			if (ItemIdIsUsed(itemId))
			{
				tup = (BrinTuple *) PageGetItem(state->page,
											  PageGetItemId(state->page,
															state->offset));
				state->dtup = brin_deform_tuple(state->bdesc, tup);
				state->attno = 1;
				state->unusedItem = false;
			}
			else
				state->unusedItem = true;

			MemoryContextSwitchTo(mctx);
		}
		else
			state->attno++;

		MemSet(nulls, 0, sizeof(nulls));

		if (state->unusedItem)
		{
			values[0] = UInt16GetDatum(state->offset);
			nulls[1] = true;
			nulls[2] = true;
			nulls[3] = true;
			nulls[4] = true;
			nulls[5] = true;
			nulls[6] = true;
		}
		else
		{
			int		att = state->attno - 1;

			values[0] = UInt16GetDatum(state->offset);
			values[1] = UInt32GetDatum(state->dtup->bt_blkno);
			values[2] = UInt16GetDatum(state->attno);
			values[3] = BoolGetDatum(state->dtup->bt_columns[att].bv_allnulls);
			values[4] = BoolGetDatum(state->dtup->bt_columns[att].bv_hasnulls);
			values[5] = BoolGetDatum(state->dtup->bt_placeholder);
			if (!state->dtup->bt_columns[att].bv_allnulls)
			{
				BrinValues   *bvalues = &state->dtup->bt_columns[att];
				StringInfoData	s;
				bool		first;
				int			i;

				initStringInfo(&s);
				appendStringInfoChar(&s, '{');

				first = true;

//.........这里部分代码省略.........
	Assert(log2_num_buckets < HASH_MAX_SPLITPOINTS);

	/*
	 * We initialize the metapage, the first N bucket pages, and the first
	 * bitmap page in sequence, using _hash_getnewbuf to cause smgrextend()
	 * calls to occur.  This ensures that the smgr level has the right idea of
	 * the physical index length.
	 */
	metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, forkNum);
	pg = BufferGetPage(metabuf);

	pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
	pageopaque->hasho_prevblkno = InvalidBlockNumber;
	pageopaque->hasho_nextblkno = InvalidBlockNumber;
	pageopaque->hasho_bucket = -1;
	pageopaque->hasho_flag = LH_META_PAGE;
	pageopaque->hasho_page_id = HASHO_PAGE_ID;

	metap = HashPageGetMeta(pg);

	metap->hashm_magic = HASH_MAGIC;
	metap->hashm_version = HASH_VERSION;
	metap->hashm_ntuples = 0;
	metap->hashm_nmaps = 0;
	metap->hashm_ffactor = ffactor;
	metap->hashm_bsize = HashGetMaxBitmapSize(pg);
	/* find largest bitmap array size that will fit in page size */
	for (i = _hash_log2(metap->hashm_bsize); i > 0; --i)
	{
		if ((1 << i) <= metap->hashm_bsize)
			break;
	}
	Assert(i > 0);
	metap->hashm_bmsize = 1 << i;
	metap->hashm_bmshift = i + BYTE_TO_BIT;
	Assert((1 << BMPG_SHIFT(metap)) == (BMPG_MASK(metap) + 1));

	/*
	 * Label the index with its primary hash support function's OID.  This is
	 * pretty useless for normal operation (in fact, hashm_procid is not used
	 * anywhere), but it might be handy for forensic purposes so we keep it.
	 */
	metap->hashm_procid = index_getprocid(rel, 1, HASHPROC);

	/*
	 * We initialize the index with N buckets, 0 .. N-1, occupying physical
	 * blocks 1 to N.  The first freespace bitmap page is in block N+1. Since
	 * N is a power of 2, we can set the masks this way:
	 */
	metap->hashm_maxbucket = metap->hashm_lowmask = num_buckets - 1;
	metap->hashm_highmask = (num_buckets << 1) - 1;

	MemSet(metap->hashm_spares, 0, sizeof(metap->hashm_spares));
	MemSet(metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));

	/* Set up mapping for one spare page after the initial splitpoints */
	metap->hashm_spares[log2_num_buckets] = 1;
	metap->hashm_ovflpoint = log2_num_buckets;
	metap->hashm_firstfree = 0;

	/*
	 * Release buffer lock on the metapage while we initialize buckets.
	 * Otherwise, we'll be in interrupt holdoff and the CHECK_FOR_INTERRUPTS
	 * won't accomplish anything.  It's a bad idea to hold buffer locks for
	 * long intervals in any case, since that can block the bgwriter.
	 */
	_hash_chgbufaccess(rel, metabuf, HASH_WRITE, HASH_NOLOCK);

	/*
	 * Initialize the first N buckets
	 */
	for (i = 0; i < num_buckets; i++)
	{
		/* Allow interrupts, in case N is huge */
		CHECK_FOR_INTERRUPTS();

		buf = _hash_getnewbuf(rel, BUCKET_TO_BLKNO(metap, i), forkNum);
		pg = BufferGetPage(buf);
		pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
		pageopaque->hasho_prevblkno = InvalidBlockNumber;
		pageopaque->hasho_nextblkno = InvalidBlockNumber;
		pageopaque->hasho_bucket = i;
		pageopaque->hasho_flag = LH_BUCKET_PAGE;
		pageopaque->hasho_page_id = HASHO_PAGE_ID;
		_hash_wrtbuf(rel, buf);
	}

	/* Now reacquire buffer lock on metapage */
	_hash_chgbufaccess(rel, metabuf, HASH_NOLOCK, HASH_WRITE);

	/*
	 * Initialize first bitmap page
	 */
	_hash_initbitmap(rel, metap, num_buckets + 1, forkNum);

	/* all done */
	_hash_wrtbuf(rel, metabuf);

	return num_buckets;
}

/*
 *	visibilitymap_truncate - truncate the visibility map
 *
 * The caller must hold AccessExclusiveLock on the relation, to ensure that
 * other backends receive the smgr invalidation event that this function sends
 * before they access the VM again.
 *
 * nheapblocks is the new size of the heap.
 */
void
visibilitymap_truncate(Relation rel, BlockNumber nheapblocks)
{
	BlockNumber newnblocks;

	/* last remaining block, byte, and bit */
	BlockNumber truncBlock = HEAPBLK_TO_MAPBLOCK(nheapblocks);
	uint32		truncByte = HEAPBLK_TO_MAPBYTE(nheapblocks);
	uint8		truncBit = HEAPBLK_TO_MAPBIT(nheapblocks);

#ifdef TRACE_VISIBILITYMAP
	elog(DEBUG1, "vm_truncate %s %d", RelationGetRelationName(rel), nheapblocks);
#endif

	RelationOpenSmgr(rel);

	/*
	 * If no visibility map has been created yet for this relation, there's
	 * nothing to truncate.
	 */
	if (!smgrexists(rel->rd_smgr, VISIBILITYMAP_FORKNUM))
		return;

	/*
	 * Unless the new size is exactly at a visibility map page boundary, the
	 * tail bits in the last remaining map page, representing truncated heap
	 * blocks, need to be cleared. This is not only tidy, but also necessary
	 * because we don't get a chance to clear the bits if the heap is extended
	 * again.
	 */
	if (truncByte != 0 || truncBit != 0)
	{
		Buffer		mapBuffer;
		Page		page;
		char	   *map;

		newnblocks = truncBlock + 1;

		mapBuffer = vm_readbuf(rel, truncBlock, false);
		if (!BufferIsValid(mapBuffer))
		{
			/* nothing to do, the file was already smaller */
			return;
		}

		page = BufferGetPage(mapBuffer);
		map = PageGetContents(page);

		LockBuffer(mapBuffer, BUFFER_LOCK_EXCLUSIVE);

		/* Clear out the unwanted bytes. */
		MemSet(&map[truncByte + 1], 0, MAPSIZE - (truncByte + 1));

		/*
		 * Mask out the unwanted bits of the last remaining byte.
		 *
		 * ((1 << 0) - 1) = 00000000 ((1 << 1) - 1) = 00000001 ... ((1 << 6) -
		 * 1) = 00111111 ((1 << 7) - 1) = 01111111
		 */
		map[truncByte] &= (1 << truncBit) - 1;

		MarkBufferDirty(mapBuffer);
		UnlockReleaseBuffer(mapBuffer);
	}
	else
		newnblocks = truncBlock;

	if (smgrnblocks(rel->rd_smgr, VISIBILITYMAP_FORKNUM) <= newnblocks)
	{
		/* nothing to do, the file was already smaller than requested size */
		return;
	}

	/* Truncate the unused VM pages, and send smgr inval message */
	smgrtruncate(rel->rd_smgr, VISIBILITYMAP_FORKNUM, newnblocks);

	/*
	 * We might as well update the local smgr_vm_nblocks setting. smgrtruncate
	 * sent an smgr cache inval message, which will cause other backends to
	 * invalidate their copy of smgr_vm_nblocks, and this one too at the next
	 * command boundary.  But this ensures it isn't outright wrong until then.
	 */
	if (rel->rd_smgr)
		rel->rd_smgr->smgr_vm_nblocks = newnblocks;
}

//.........这里部分代码省略.........
		}

		/*
		 * If no (more) held modes to report, see if PROC is waiting for a
		 * lock on this lock.
		 */
		if (!granted)
		{
			if (proc->waitLock == proclock->tag.myLock)
			{
				/* Yes, so report it with proper mode */
				mode = proc->waitLockMode;

				/*
				 * We are now done with this PROCLOCK, so advance pointer to
				 * continue with next one on next call.
				 */
				mystatus->currIdx++;
			}
			else
			{
				/*
				 * Okay, we've displayed all the locks associated with this
				 * PROCLOCK, proceed to the next one.
				 */
				mystatus->currIdx++;
				continue;
			}
		}

		/*
		 * Form tuple with appropriate data.
		 */
		MemSet(values, 0, sizeof(values));
		MemSet(nulls, false, sizeof(nulls));

		if (lock->tag.locktag_type <= LOCKTAG_ADVISORY)
			locktypename = LockTagTypeNames[lock->tag.locktag_type];
		else
		{
			snprintf(tnbuf, sizeof(tnbuf), "unknown %d",
					 (int) lock->tag.locktag_type);
			locktypename = tnbuf;
		}
		values[0] = CStringGetTextDatum(locktypename);

		switch (lock->tag.locktag_type)
		{
			case LOCKTAG_RELATION:
			case LOCKTAG_RELATION_EXTEND:
			case LOCKTAG_RELATION_RESYNCHRONIZE:
				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
				values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
				nulls[3] = true;
				nulls[4] = true;
				nulls[5] = true;
				nulls[6] = true;
				nulls[7] = true;
				nulls[8] = true;
				break;
			case LOCKTAG_PAGE:
				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
				values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
				values[3] = UInt32GetDatum(lock->tag.locktag_field3);
				nulls[4] = true;
				nulls[5] = true;

/*
 * Create a table space
 *
 * Only superusers can create a tablespace. This seems a reasonable restriction
 * since we're determining the system layout and, anyway, we probably have
 * root if we're doing this kind of activity
 */
Oid
CreateTableSpace(CreateTableSpaceStmt *stmt)
{
#ifdef HAVE_SYMLINK
	Relation	rel;
	Datum		values[Natts_pg_tablespace];
	bool		nulls[Natts_pg_tablespace];
	HeapTuple	tuple;
	Oid			tablespaceoid;
	char	   *location;
	Oid			ownerId;

	/* Must be super user */
	if (!superuser())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied to create tablespace \"%s\"",
						stmt->tablespacename),
				 errhint("Must be superuser to create a tablespace.")));

	/* However, the eventual owner of the tablespace need not be */
	if (stmt->owner)
		ownerId = get_role_oid(stmt->owner, false);
	else
		ownerId = GetUserId();

	/* Unix-ify the offered path, and strip any trailing slashes */
	location = pstrdup(stmt->location);
	canonicalize_path(location);

	/* disallow quotes, else CREATE DATABASE would be at risk */
	if (strchr(location, '\''))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_NAME),
				 errmsg("tablespace location cannot contain single quotes")));

	/*
	 * Allowing relative paths seems risky
	 *
	 * this also helps us ensure that location is not empty or whitespace
	 */
	if (!is_absolute_path(location))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("tablespace location must be an absolute path")));

	/*
	 * Check that location isn't too long. Remember that we're going to append
	 * 'PG_XXX/<dboid>/<relid>.<nnn>'.	FYI, we never actually reference the
	 * whole path, but mkdir() uses the first two parts.
	 */
	if (strlen(location) + 1 + strlen(TABLESPACE_VERSION_DIRECTORY) + 1 +
		OIDCHARS + 1 + OIDCHARS + 1 + OIDCHARS > MAXPGPATH)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("tablespace location \"%s\" is too long",
						location)));

	/*
	 * Disallow creation of tablespaces named "pg_xxx"; we reserve this
	 * namespace for system purposes.
	 */
	if (!allowSystemTableMods && IsReservedName(stmt->tablespacename))
		ereport(ERROR,
				(errcode(ERRCODE_RESERVED_NAME),
				 errmsg("unacceptable tablespace name \"%s\"",
						stmt->tablespacename),
		errdetail("The prefix \"pg_\" is reserved for system tablespaces.")));

	/*
	 * Check that there is no other tablespace by this name.  (The unique
	 * index would catch this anyway, but might as well give a friendlier
	 * message.)
	 */
	if (OidIsValid(get_tablespace_oid(stmt->tablespacename, true)))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_OBJECT),
				 errmsg("tablespace \"%s\" already exists",
						stmt->tablespacename)));

	/*
	 * Insert tuple into pg_tablespace.  The purpose of doing this first is to
	 * lock the proposed tablename against other would-be creators. The
	 * insertion will roll back if we find problems below.
	 */
	rel = heap_open(TableSpaceRelationId, RowExclusiveLock);

	MemSet(nulls, false, sizeof(nulls));

	values[Anum_pg_tablespace_spcname - 1] =
		DirectFunctionCall1(namein, CStringGetDatum(stmt->tablespacename));
	values[Anum_pg_tablespace_spcowner - 1] =
		ObjectIdGetDatum(ownerId);
//.........这里部分代码省略.........

/*
 * MarkAsPreparing
 *		Reserve the GID for the given transaction.
 *
 * Internally, this creates a gxact struct and puts it into the active array.
 * NOTE: this is also used when reloading a gxact after a crash; so avoid
 * assuming that we can use very much backend context.
 */
GlobalTransaction
MarkAsPreparing(TransactionId xid, const char *gid,
				TimestampTz prepared_at, Oid owner, Oid databaseid)
{
	GlobalTransaction gxact;
	int			i;

	if (strlen(gid) >= GIDSIZE)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("transaction identifier \"%s\" is too long",
						gid)));

	LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);

	/*
	 * First, find and recycle any gxacts that failed during prepare. We do
	 * this partly to ensure we don't mistakenly say their GIDs are still
	 * reserved, and partly so we don't fail on out-of-slots unnecessarily.
	 */
	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		gxact = TwoPhaseState->prepXacts[i];
		if (!gxact->valid && !TransactionIdIsActive(gxact->locking_xid))
		{
			/* It's dead Jim ... remove from the active array */
			TwoPhaseState->numPrepXacts--;
			TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
			/* and put it back in the freelist */
			gxact->proc.links.next = TwoPhaseState->freeGXacts;
			TwoPhaseState->freeGXacts = MAKE_OFFSET(gxact);
			/* Back up index count too, so we don't miss scanning one */
			i--;
		}
	}

	/* Check for conflicting GID */
	for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
	{
		gxact = TwoPhaseState->prepXacts[i];
		if (strcmp(gxact->gid, gid) == 0)
		{
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_OBJECT),
					 errmsg("transaction identifier \"%s\" is already in use",
							gid)));
		}
	}

	/* Get a free gxact from the freelist */
	if (TwoPhaseState->freeGXacts == INVALID_OFFSET)
		ereport(ERROR,
				(errcode(ERRCODE_OUT_OF_MEMORY),
				 errmsg("maximum number of prepared transactions reached"),
				 errhint("Increase max_prepared_transactions (currently %d).",
						 max_prepared_xacts)));
	gxact = (GlobalTransaction) MAKE_PTR(TwoPhaseState->freeGXacts);
	TwoPhaseState->freeGXacts = gxact->proc.links.next;

	/* Initialize it */
	MemSet(&gxact->proc, 0, sizeof(PGPROC));
	SHMQueueElemInit(&(gxact->proc.links));
	gxact->proc.waitStatus = STATUS_OK;
	gxact->proc.xid = xid;
	gxact->proc.xmin = InvalidTransactionId;
	gxact->proc.pid = 0;
	gxact->proc.databaseId = databaseid;
	gxact->proc.roleId = owner;
	gxact->proc.inVacuum = false;
	gxact->proc.lwWaiting = false;
	gxact->proc.lwExclusive = false;
	gxact->proc.lwWaitLink = NULL;
	gxact->proc.waitLock = NULL;
	gxact->proc.waitProcLock = NULL;
	for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
		SHMQueueInit(&(gxact->proc.myProcLocks[i]));
	/* subxid data must be filled later by GXactLoadSubxactData */
	gxact->proc.subxids.overflowed = false;
	gxact->proc.subxids.nxids = 0;

	gxact->prepared_at = prepared_at;
	/* initialize LSN to 0 (start of WAL) */
	gxact->prepare_lsn.xlogid = 0;
	gxact->prepare_lsn.xrecoff = 0;
	gxact->owner = owner;
	gxact->locking_xid = xid;
	gxact->valid = false;
	strcpy(gxact->gid, gid);

	/* And insert it into the active array */
	Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts);
	TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact;
//.........这里部分代码省略.........

Datum
hstore_from_record(PG_FUNCTION_ARGS)
{
	HeapTupleHeader rec;
	int4		buflen;
	HStore	   *out;
	Pairs	   *pairs;
	Oid			tupType;
	int32		tupTypmod;
	TupleDesc	tupdesc;
	HeapTupleData tuple;
	RecordIOData *my_extra;
	int			ncolumns;
	int			i,
				j;
	Datum	   *values;
	bool	   *nulls;

	if (PG_ARGISNULL(0))
	{
		Oid			argtype = get_fn_expr_argtype(fcinfo->flinfo, 0);

		/*
		 * have no tuple to look at, so the only source of type info is the
		 * argtype. The lookup_rowtype_tupdesc call below will error out if we
		 * don't have a known composite type oid here.
		 */
		tupType = argtype;
		tupTypmod = -1;

		rec = NULL;
	}
	else
	{
		rec = PG_GETARG_HEAPTUPLEHEADER(0);

		/* Extract type info from the tuple itself */
		tupType = HeapTupleHeaderGetTypeId(rec);
		tupTypmod = HeapTupleHeaderGetTypMod(rec);
	}

	tupdesc = lookup_rowtype_tupdesc(tupType, tupTypmod);
	ncolumns = tupdesc->natts;

	/*
	 * We arrange to look up the needed I/O info just once per series of
	 * calls, assuming the record type doesn't change underneath us.
	 */
	my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
	if (my_extra == NULL ||
		my_extra->ncolumns != ncolumns)
	{
		fcinfo->flinfo->fn_extra =
			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
							   sizeof(RecordIOData) - sizeof(ColumnIOData)
							   + ncolumns * sizeof(ColumnIOData));
		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
		my_extra->record_type = InvalidOid;
		my_extra->record_typmod = 0;
	}

	if (my_extra->record_type != tupType ||
		my_extra->record_typmod != tupTypmod)
	{
		MemSet(my_extra, 0,
			   sizeof(RecordIOData) - sizeof(ColumnIOData)
			   + ncolumns * sizeof(ColumnIOData));
		my_extra->record_type = tupType;
		my_extra->record_typmod = tupTypmod;
		my_extra->ncolumns = ncolumns;
	}

	pairs = palloc(ncolumns * sizeof(Pairs));

	if (rec)
	{
		/* Build a temporary HeapTuple control structure */
		tuple.t_len = HeapTupleHeaderGetDatumLength(rec);
		ItemPointerSetInvalid(&(tuple.t_self));
		tuple.t_tableOid = InvalidOid;
		tuple.t_data = rec;

		values = (Datum *) palloc(ncolumns * sizeof(Datum));
		nulls = (bool *) palloc(ncolumns * sizeof(bool));

		/* Break down the tuple into fields */
		heap_deform_tuple(&tuple, tupdesc, values, nulls);
	}
	else
	{
		values = NULL;
		nulls = NULL;
	}

	for (i = 0, j = 0; i < ncolumns; ++i)
	{
		ColumnIOData *column_info = &my_extra->columns[i];
		Oid			column_type = tupdesc->attrs[i]->atttypid;
		char	   *value;

//.........这里部分代码省略.........

//.........这里部分代码省略.........
			neednextpage = false;
		}

		/*
		 * If we have a pre-existing page, see if it is the page we want to
		 * write, or a later one.
		 */
		if (olddata != NULL && olddata->pageno == pageno)
		{
			/*
			 * Update an existing page with fresh data.
			 *
			 * First, load old data into workbuf
			 */
			datafield = &(olddata->data);		/* see note at top of file */
			pfreeit = false;
			if (VARATT_IS_EXTENDED(datafield))
			{
				datafield = (bytea *)
					heap_tuple_untoast_attr((struct varlena *) datafield);
				pfreeit = true;
			}
			len = getbytealen(datafield);
			Assert(len <= LOBLKSIZE);
			memcpy(workb, VARDATA(datafield), len);
			if (pfreeit)
				pfree(datafield);

			/*
			 * Fill any hole
			 */
			off = (int) (obj_desc->offset % LOBLKSIZE);
			if (off > len)
				MemSet(workb + len, 0, off - len);

			/*
			 * Insert appropriate portion of new data
			 */
			n = LOBLKSIZE - off;
			n = (n <= (nbytes - nwritten)) ? n : (nbytes - nwritten);
			memcpy(workb + off, buf + nwritten, n);
			nwritten += n;
			obj_desc->offset += n;
			off += n;
			/* compute valid length of new page */
			len = (len >= off) ? len : off;
			SET_VARSIZE(&workbuf.hdr, len + VARHDRSZ);

			/*
			 * Form and insert updated tuple
			 */
			memset(values, 0, sizeof(values));
			memset(nulls, false, sizeof(nulls));
			memset(replace, false, sizeof(replace));
			values[Anum_pg_largeobject_data - 1] = PointerGetDatum(&workbuf);
			replace[Anum_pg_largeobject_data - 1] = true;
			newtup = heap_modify_tuple(oldtuple, RelationGetDescr(lo_heap_r),
									   values, nulls, replace);
			simple_heap_update(lo_heap_r, &newtup->t_self, newtup);
			CatalogIndexInsert(indstate, newtup);
			heap_freetuple(newtup);

			/*
			 * We're done with this old page.
			 */
			oldtuple = NULL;

void
inv_truncate(LargeObjectDesc *obj_desc, int len)
{
	int32		pageno = (int32) (len / LOBLKSIZE);
	int			off;
	ScanKeyData skey[2];
	SysScanDesc sd;
	HeapTuple	oldtuple;
	Form_pg_largeobject olddata;
	struct
	{
		bytea		hdr;
		char		data[LOBLKSIZE];	/* make struct big enough */
		int32		align_it;	/* ensure struct is aligned well enough */
	}			workbuf;
	char	   *workb = VARDATA(&workbuf.hdr);
	HeapTuple	newtup;
	Datum		values[Natts_pg_largeobject];
	bool		nulls[Natts_pg_largeobject];
	bool		replace[Natts_pg_largeobject];
	CatalogIndexState indstate;

	Assert(PointerIsValid(obj_desc));

	/* enforce writability because snapshot is probably wrong otherwise */
	if ((obj_desc->flags & IFS_WRLOCK) == 0)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("large object %u was not opened for writing",
						obj_desc->id)));

	/* check existence of the target largeobject */
	if (!LargeObjectExists(obj_desc->id))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
			   errmsg("large object %u was already dropped", obj_desc->id)));

	open_lo_relation();

	indstate = CatalogOpenIndexes(lo_heap_r);

	ScanKeyInit(&skey[0],
				Anum_pg_largeobject_loid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(obj_desc->id));

	ScanKeyInit(&skey[1],
				Anum_pg_largeobject_pageno,
				BTGreaterEqualStrategyNumber, F_INT4GE,
				Int32GetDatum(pageno));

	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
									obj_desc->snapshot, 2, skey);

	/*
	 * If possible, get the page the truncation point is in. The truncation
	 * point may be beyond the end of the LO or in a hole.
	 */
	olddata = NULL;
	if ((oldtuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
	{
		if (HeapTupleHasNulls(oldtuple))		/* paranoia */
			elog(ERROR, "null field found in pg_largeobject");
		olddata = (Form_pg_largeobject) GETSTRUCT(oldtuple);
		Assert(olddata->pageno >= pageno);
	}

	/*
	 * If we found the page of the truncation point we need to truncate the
	 * data in it.	Otherwise if we're in a hole, we need to create a page to
	 * mark the end of data.
	 */
	if (olddata != NULL && olddata->pageno == pageno)
	{
		/* First, load old data into workbuf */
		bytea	   *datafield = &(olddata->data);		/* see note at top of
														 * file */
		bool		pfreeit = false;
		int			pagelen;

		if (VARATT_IS_EXTENDED(datafield))
		{
			datafield = (bytea *)
				heap_tuple_untoast_attr((struct varlena *) datafield);
			pfreeit = true;
		}
		pagelen = getbytealen(datafield);
		Assert(pagelen <= LOBLKSIZE);
		memcpy(workb, VARDATA(datafield), pagelen);
		if (pfreeit)
			pfree(datafield);

		/*
		 * Fill any hole
		 */
		off = len % LOBLKSIZE;
		if (off > pagelen)
			MemSet(workb + pagelen, 0, off - pagelen);

		/* compute length of new page */
//.........这里部分代码省略.........

bool BootpTx(void){
	int			i;
	char		*txPktBuf, *rxPktBuf;
	long		delay;		// delay : 1초 delay후 실패면 재시도.
	time_t now;

	txPktBuf = PktBuf;
	rxPktBuf = PktBuf;

	bootpState = BOOTP_CONTINUE;
	protocol = PROT_BOOTP;

	// make boop packet.
	MemSet(txPktBuf, 0, MAX_PKT_SIZE);
	SetBootpHeader((char *)(txPktBuf+ETHER_HDR_SIZE+IP_HDR_SIZE+UDP_HDR_SIZE));
	SetUdpHeader((char *)(txPktBuf+ETHER_HDR_SIZE+IP_HDR_SIZE), bootps, bootpc, BOOTP_HDR_SIZE);
	SetIPHeader((char *)(txPktBuf+ETHER_HDR_SIZE), noIP, broadcastIP, UDP_HDR_SIZE+BOOTP_HDR_SIZE);
	SetEtherHeader(txPktBuf, broadcastEther, PROT_IP);

	//if (!NetInit()) return false;

	// view info.
	printf("Our Ethernet address    : ");
	PrintEthAddr(clientEther);
	printf(".\n");
	printf("Sending bootp packet...\n");
	
	// bootp operation.
	for (i=0; i<TIMEOUT; i++){
		// transmit bootp packet to host.
		printf(".");
		if (!TxPacket(txPktBuf, ETHER_HDR_SIZE+IP_HDR_SIZE+UDP_HDR_SIZE+BOOTP_HDR_SIZE)) break;
		// receive bootp packet from host.
		delay = GetTime(&now)+HZ;
		while (GetTime(&now)<delay && bootpState==BOOTP_CONTINUE){
			RxPacket(rxPktBuf);
			if (bootpState==BOOTP_SUCCESS) break;

		}
		if (bootpState==BOOTP_SUCCESS) break;
	}
	printf("\n");

	protocol = NOPROTOCOL;

	if (bootpState==BOOTP_SUCCESS){
		printf("Bootp Packet received.\n");
		
		printf("\tHost   (server) Ethernet : ");
		PrintEthAddr(hostEther);
		printf("\n");

		printf("\tHost   (server) IP       : ");
		PrintIPAddr(hostIP);
		printf("\n");

		printf("\tClient (target) Ethernet : ");
		PrintEthAddr(clientEther);
		printf("\n");

		printf("\tClient (target) IP       : ");
		PrintIPAddr(clientIP);
		printf("\n");

		printf("\n");
		return true;
	}
	else {
		printf("Bootp packet is not received.\n\n");
		return false;
	}
	return true;
}	// BootpTx.

int
inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
{
	int			nread = 0;
	int			n;
	int			off;
	int			len;
	int32		pageno = (int32) (obj_desc->offset / LOBLKSIZE);
	uint32		pageoff;
	ScanKeyData skey[2];
	SysScanDesc sd;
	HeapTuple	tuple;

	Assert(PointerIsValid(obj_desc));
	Assert(buf != NULL);

	if (nbytes <= 0)
		return 0;

	open_lo_relation();

	ScanKeyInit(&skey[0],
				Anum_pg_largeobject_loid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(obj_desc->id));

	ScanKeyInit(&skey[1],
				Anum_pg_largeobject_pageno,
				BTGreaterEqualStrategyNumber, F_INT4GE,
				Int32GetDatum(pageno));

	sd = systable_beginscan_ordered(lo_heap_r, lo_index_r,
									obj_desc->snapshot, 2, skey);

	while ((tuple = systable_getnext_ordered(sd, ForwardScanDirection)) != NULL)
	{
		Form_pg_largeobject data;
		bytea	   *datafield;
		bool		pfreeit;

		if (HeapTupleHasNulls(tuple))	/* paranoia */
			elog(ERROR, "null field found in pg_largeobject");
		data = (Form_pg_largeobject) GETSTRUCT(tuple);

		/*
		 * We expect the indexscan will deliver pages in order.  However,
		 * there may be missing pages if the LO contains unwritten "holes". We
		 * want missing sections to read out as zeroes.
		 */
		pageoff = ((uint32) data->pageno) * LOBLKSIZE;
		if (pageoff > obj_desc->offset)
		{
			n = pageoff - obj_desc->offset;
			n = (n <= (nbytes - nread)) ? n : (nbytes - nread);
			MemSet(buf + nread, 0, n);
			nread += n;
			obj_desc->offset += n;
		}

		if (nread < nbytes)
		{
			Assert(obj_desc->offset >= pageoff);
			off = (int) (obj_desc->offset - pageoff);
			Assert(off >= 0 && off < LOBLKSIZE);

			datafield = &(data->data);	/* see note at top of file */
			pfreeit = false;
			if (VARATT_IS_EXTENDED(datafield))
			{
				datafield = (bytea *)
					heap_tuple_untoast_attr((struct varlena *) datafield);
				pfreeit = true;
			}
			len = getbytealen(datafield);
			if (len > off)
			{
				n = len - off;
				n = (n <= (nbytes - nread)) ? n : (nbytes - nread);
				memcpy(buf + nread, VARDATA(datafield) + off, n);
				nread += n;
				obj_desc->offset += n;
			}
			if (pfreeit)
				pfree(datafield);
		}

		if (nread >= nbytes)
			break;
	}

	systable_endscan_ordered(sd);

	return nread;
}

/*
 *	_hash_metapinit() -- Initialize the metadata page of a hash index,
 *				the two buckets that we begin with and the initial
 *				bitmap page.
 *
 * We are fairly cavalier about locking here, since we know that no one else
 * could be accessing this index.  In particular the rule about not holding
 * multiple buffer locks is ignored.
 */
void
_hash_metapinit(Relation rel)
{
	MIRROREDLOCK_BUFMGR_DECLARE;

	HashMetaPage metap;
	HashPageOpaque pageopaque;
	Buffer		metabuf;
	Buffer		buf;
	Page		pg;
	int32		data_width;
	int32		item_width;
	int32		ffactor;
	uint16		i;

	/* safety check */
	if (RelationGetNumberOfBlocks(rel) != 0)
		elog(ERROR, "cannot initialize non-empty hash index \"%s\"",
			 RelationGetRelationName(rel));

	/*
	 * Determine the target fill factor (in tuples per bucket) for this index.
	 * The idea is to make the fill factor correspond to pages about as full
	 * as the user-settable fillfactor parameter says.	We can compute it
	 * exactly if the index datatype is fixed-width, but for var-width there's
	 * some guessing involved.
	 */
	data_width = get_typavgwidth(RelationGetDescr(rel)->attrs[0]->atttypid,
								 RelationGetDescr(rel)->attrs[0]->atttypmod);
	item_width = MAXALIGN(sizeof(IndexTupleData)) + MAXALIGN(data_width) +
		sizeof(ItemIdData);		/* include the line pointer */
	ffactor = RelationGetTargetPageUsage(rel, HASH_DEFAULT_FILLFACTOR) / item_width;
	/* keep to a sane range */
	if (ffactor < 10)
		ffactor = 10;

	/*
	 * We initialize the metapage, the first two bucket pages, and the
	 * first bitmap page in sequence, using _hash_getnewbuf to cause
	 * smgrextend() calls to occur.  This ensures that the smgr level
	 * has the right idea of the physical index length.
	 */
	
	// -------- MirroredLock ----------
	MIRROREDLOCK_BUFMGR_LOCK;
	
	metabuf = _hash_getnewbuf(rel, HASH_METAPAGE, HASH_WRITE);
	pg = BufferGetPage(metabuf);
	_hash_pageinit(pg, BufferGetPageSize(metabuf));

	pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
	pageopaque->hasho_prevblkno = InvalidBlockNumber;
	pageopaque->hasho_nextblkno = InvalidBlockNumber;
	pageopaque->hasho_bucket = -1;
	pageopaque->hasho_flag = LH_META_PAGE;
	pageopaque->hasho_filler = HASHO_FILL;

	metap = (HashMetaPage) pg;

	metap->hashm_magic = HASH_MAGIC;
	metap->hashm_version = HASH_VERSION;
	metap->hashm_ntuples = 0;
	metap->hashm_nmaps = 0;
	metap->hashm_ffactor = ffactor;
	metap->hashm_bsize = BufferGetPageSize(metabuf);
	/* find largest bitmap array size that will fit in page size */
	for (i = _hash_log2(metap->hashm_bsize); i > 0; --i)
	{
		if ((1 << i) <= (metap->hashm_bsize -
						 (MAXALIGN(sizeof(PageHeaderData)) +
						  MAXALIGN(sizeof(HashPageOpaqueData)))))
			break;
	}
	Assert(i > 0);
	metap->hashm_bmsize = 1 << i;
	metap->hashm_bmshift = i + BYTE_TO_BIT;
	Assert((1 << BMPG_SHIFT(metap)) == (BMPG_MASK(metap) + 1));

	metap->hashm_procid = index_getprocid(rel, 1, HASHPROC);

	/*
	 * We initialize the index with two buckets, 0 and 1, occupying physical
	 * blocks 1 and 2.	The first freespace bitmap page is in block 3.
	 */
	metap->hashm_maxbucket = metap->hashm_lowmask = 1;	/* nbuckets - 1 */
	metap->hashm_highmask = 3;	/* (nbuckets << 1) - 1 */

	MemSet(metap->hashm_spares, 0, sizeof(metap->hashm_spares));
	MemSet(metap->hashm_mapp, 0, sizeof(metap->hashm_mapp));

	metap->hashm_spares[1] = 1; /* the first bitmap page is only spare */
//.........这里部分代码省略.........

/*
 * parseInput subroutine to read a 'B' or 'D' (row data) message.
 * We add another tuple to the existing PGresult structure.
 * Returns: 0 if completed message, EOF if error or not enough data yet.
 *
 * Note that if we run out of data, we have to suspend and reprocess
 * the message after more data is received.  We keep a partially constructed
 * tuple in conn->curTuple, and avoid reallocating already-allocated storage.
 */
static int
getAnotherTuple(PGconn *conn, bool binary)
{
	PGresult   *result = conn->result;
	int			nfields = result->numAttributes;
	PGresAttValue *tup;

	/* the backend sends us a bitmap of which attributes are null */
	char		std_bitmap[64]; /* used unless it doesn't fit */
	char	   *bitmap = std_bitmap;
	int			i;
	size_t		nbytes;			/* the number of bytes in bitmap  */
	char		bmap;			/* One byte of the bitmap */
	int			bitmap_index;	/* Its index */
	int			bitcnt;			/* number of bits examined in current byte */
	int			vlen;			/* length of the current field value */

	result->binary = binary;

	/* Allocate tuple space if first time for this data message */
	if (conn->curTuple == NULL)
	{
		conn->curTuple = (PGresAttValue *)
			pqResultAlloc(result, nfields * sizeof(PGresAttValue), TRUE);
		if (conn->curTuple == NULL)
			goto outOfMemory;
		MemSet(conn->curTuple, 0, nfields * sizeof(PGresAttValue));

		/*
		 * If it's binary, fix the column format indicators.  We assume the
		 * backend will consistently send either B or D, not a mix.
		 */
		if (binary)
		{
			for (i = 0; i < nfields; i++)
				result->attDescs[i].format = 1;
		}
	}
	tup = conn->curTuple;

	/* Get the null-value bitmap */
	nbytes = (nfields + BITS_PER_BYTE - 1) / BITS_PER_BYTE;
	/* malloc() only for unusually large field counts... */
	if (nbytes > sizeof(std_bitmap))
	{
		bitmap = (char *) malloc(nbytes);
		if (!bitmap)
			goto outOfMemory;
	}

	if (pqGetnchar(bitmap, nbytes, conn))
		goto EOFexit;

	/* Scan the fields */
	bitmap_index = 0;
	bmap = bitmap[bitmap_index];
	bitcnt = 0;

	for (i = 0; i < nfields; i++)
	{
		if (!(bmap & 0200))
		{
			/* if the field value is absent, make it a null string */
			tup[i].value = result->null_field;
			tup[i].len = NULL_LEN;
		}
		else
		{
			/* get the value length (the first four bytes are for length) */
			if (pqGetInt(&vlen, 4, conn))
				goto EOFexit;
			if (!binary)
				vlen = vlen - 4;
			if (vlen < 0)
				vlen = 0;
			if (tup[i].value == NULL)
			{
				tup[i].value = (char *) pqResultAlloc(result, vlen + 1, binary);
				if (tup[i].value == NULL)
					goto outOfMemory;
			}
			tup[i].len = vlen;
			/* read in the value */
			if (vlen > 0)
				if (pqGetnchar((char *) (tup[i].value), vlen, conn))
					goto EOFexit;
			/* we have to terminate this ourselves */
			tup[i].value[vlen] = '\0';
		}
		/* advance the bitmap stuff */
		bitcnt++;
//.........这里部分代码省略.........

/*
 * parseInput subroutine to read a 'T' (row descriptions) message.
 * We build a PGresult structure containing the attribute data.
 * Returns: 0 if completed message, EOF if not enough data yet.
 *
 * Note that if we run out of data, we have to release the partially
 * constructed PGresult, and rebuild it again next time.  Fortunately,
 * that shouldn't happen often, since 'T' messages usually fit in a packet.
 */
static int
getRowDescriptions(PGconn *conn)
{
	PGresult   *result = NULL;
	int			nfields;
	int			i;

	result = PQmakeEmptyPGresult(conn, PGRES_TUPLES_OK);
	if (!result)
		goto failure;

	/* parseInput already read the 'T' label. */
	/* the next two bytes are the number of fields	*/
	if (pqGetInt(&(result->numAttributes), 2, conn))
		goto failure;
	nfields = result->numAttributes;

	/* allocate space for the attribute descriptors */
	if (nfields > 0)
	{
		result->attDescs = (PGresAttDesc *)
			pqResultAlloc(result, nfields * sizeof(PGresAttDesc), TRUE);
		if (!result->attDescs)
			goto failure;
		MemSet(result->attDescs, 0, nfields * sizeof(PGresAttDesc));
	}

	/* get type info */
	for (i = 0; i < nfields; i++)
	{
		int			typid;
		int			typlen;
		int			atttypmod;

		if (pqGets(&conn->workBuffer, conn) ||
			pqGetInt(&typid, 4, conn) ||
			pqGetInt(&typlen, 2, conn) ||
			pqGetInt(&atttypmod, 4, conn))
			goto failure;

		/*
		 * Since pqGetInt treats 2-byte integers as unsigned, we need to
		 * coerce the result to signed form.
		 */
		typlen = (int) ((int16) typlen);

		result->attDescs[i].name = pqResultStrdup(result,
												  conn->workBuffer.data);
		if (!result->attDescs[i].name)
			goto failure;
		result->attDescs[i].tableid = 0;
		result->attDescs[i].columnid = 0;
		result->attDescs[i].format = 0;
		result->attDescs[i].typid = typid;
		result->attDescs[i].typlen = typlen;
		result->attDescs[i].atttypmod = atttypmod;
	}

	/* Success! */
	conn->result = result;
	return 0;

failure:
	if (result)
		PQclear(result);
	return EOF;
}

/*
 * get_next_id
 *
 * Gets the smallest possible id to assign to the next continuous view.
 * We keep this minimal so that we can minimize the size of bitmaps used
 * to tag stream buffer events with.
 */
static Oid
get_next_id(Relation rel)
{
	HeapScanDesc scandesc;
	HeapTuple tup;
	List *ids_list = NIL;
	int num_ids;

	Assert(MAX_CQS % 32 == 0);

	scandesc = heap_beginscan_catalog(rel, 0, NULL);

	while ((tup = heap_getnext(scandesc, ForwardScanDirection)) != NULL)
	{
		Form_pipeline_query row = (Form_pipeline_query) GETSTRUCT(tup);
		ids_list = lappend_oid(ids_list, row->id);
	}

	heap_endscan(scandesc);

	num_ids = list_length(ids_list);

	if (num_ids)
	{
		Oid ids[num_ids];
		int counts_per_combiner[continuous_query_num_combiners];
		int i = 0;
		Oid max;
		ListCell *lc;
		int j;
		int target_combiner;
		List *potential_ids;

		MemSet(counts_per_combiner, 0, sizeof(counts_per_combiner));

		foreach(lc, ids_list)
		{
			ids[i] = lfirst_oid(lc);
			counts_per_combiner[ids[i] % continuous_query_num_combiners] += 1;
			i++;
		}

		qsort(ids, num_ids, sizeof(Oid), &compare_oid);

		if (num_ids == MAX_CQS - 1) /* -1 because 0 is an invalid id */
			ereport(ERROR,
					(errcode(ERRCODE_TOO_MANY_CONTINUOUS_VIEWS),
					errmsg("maximum number of continuous views exceeded"),
					errhint("Please drop a existing continuous view before trying to create a new one.")));

		max = ids[num_ids - 1];
		Assert(max >= num_ids);

		/*
		 * FIXME(usmanm): We do some randomization of ID generation here to make sure that CQs that
		 * are created and dropped in quick succession don't read an event that was not for them.
		 */

		/*
		 * Collect any unused ids in [1, max].
		 */
		list_free(ids_list);
		ids_list = NIL;

		for (i = 1, j = 0; j < num_ids; i++)
		{
			if (ids[j] > i)
				ids_list = lappend_oid(ids_list, (Oid) i);
			else
				j++;
		}

		/*
		 * Add all IDs between max and the next multiple of 32.
		 */
		j = Min((max / 32 + 1) * 32, MAX_CQS);
		for (i = max + 1; i < j; i++)
			ids_list = lappend_oid(ids_list, (Oid) i);

		/*
		 * Less than 16 options? Throw in some more.
		 */
		if (list_length(ids_list) < 16 && j < MAX_CQS)
			for (i = j; i < j + 32; i++)
				ids_list = lappend_oid(ids_list, (Oid) i);

		/*
		 * Figure out the target combiner (one with least IDs allocated) and try to allocate
		 * an ID that belongs to it.
		 */
		target_combiner = 0;
		for (i = 0; i < continuous_query_num_combiners; i++)
			if (counts_per_combiner[i] < counts_per_combiner[target_combiner])
//.........这里部分代码省略.........