internal static int HandlePageUnderflow(StorageImpl db, Page pg, int r, int type, BtreeKey rem, int height)
{
int nItems = GetItemsCount(pg);
if (type == ClassDescriptor.tpString)
{
Page a = db.PutPage(GetKeyStrOid(pg, r));
int an = GetItemsCount(a);
if (r < nItems)
{
// exists greater page
Page b = db.GetPage(GetKeyStrOid(pg, r + 1));
int bn = GetItemsCount(b);
int merged_size = (an + bn) * strKeySize + GetSize(a) + GetSize(b);
if (height != 1)
{
merged_size += GetKeyStrSize(pg, r) * 2 + strKeySize * 2;
}
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i, j, k;
db.pool.Unfix(b);
b = db.PutPage(GetKeyStrOid(pg, r + 1));
int size_a = GetSize(a);
int size_b = GetSize(b);
int addSize, subSize;
if (height != 1)
{
addSize = GetKeyStrSize(pg, r);
subSize = GetKeyStrSize(b, 0);
}
else
{
addSize = subSize = GetKeyStrSize(b, 0);
}
i = 0;
int prevDelta = (an * strKeySize + size_a) - (bn * strKeySize + size_b);
while (true)
{
i += 1;
int delta = ((an + i) * strKeySize + size_a + addSize * 2) - ((bn - i) * strKeySize + size_b - subSize * 2);
if (delta >= 0)
{
if (delta >= -prevDelta)
{
i -= 1;
}
break;
}
size_a += addSize * 2;
size_b -= subSize * 2;
prevDelta = delta;
if (height != 1)
{
addSize = subSize;
subSize = GetKeyStrSize(b, i);
}
else
{
addSize = subSize = GetKeyStrSize(b, i);
}
}
int result = Btree.op_done;
if (i > 0)
{
k = i;
if (height != 1)
{
int len = GetKeyStrSize(pg, r);
SetSize(a, GetSize(a) + len * 2);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
SetKeyStrSize(a, an, len);
MemCopy(a, GetKeyStrOffs(a, an), pg, GetKeyStrOffs(pg, r), len * 2, 1);
k -= 1;
an += 1;
SetKeyStrOid(a, an + k, GetKeyStrOid(b, k));
SetSize(b, GetSize(b) - GetKeyStrSize(b, k) * 2);
}
for (j = 0; j < k; j++)
{
int len = GetKeyStrSize(b, j);
SetSize(a, GetSize(a) + len * 2);
SetSize(b, GetSize(b) - len * 2);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
SetKeyStrSize(a, an, len);
SetKeyStrOid(a, an, GetKeyStrOid(b, j));
MemCopy(a, GetKeyStrOffs(a, an), b, GetKeyStrOffs(b, j), len * 2, 1);
an += 1;
}
rem.GetStr(b, i - 1);
result = ReplaceStrKey(db, pg, r, rem, height);
SetItemsCount(a, an);
SetItemsCount(b, CompactifyStrings(b, i));
}
db.pool.Unfix(a);
db.pool.Unfix(b);
return result;
}
else
{
// merge page b to a
if (height != 1)
{
int r_len = GetKeyStrSize(pg, r);
SetKeyStrSize(a, an, r_len);
SetSize(a, GetSize(a) + r_len * 2);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
MemCopy(a, GetKeyStrOffs(a, an), pg, GetKeyStrOffs(pg, r), r_len * 2, 1);
an += 1;
SetKeyStrOid(a, an + bn, GetKeyStrOid(b, bn));
}
for (int i = 0; i < bn; i++, an++)
{
SetKeyStrSize(a, an, GetKeyStrSize(b, i));
SetKeyStrOffs(a, an, GetKeyStrOffs(b, i) - GetSize(a));
SetKeyStrOid(a, an, GetKeyStrOid(b, i));
}
SetSize(a, GetSize(a) + GetSize(b));
SetItemsCount(a, an);
MemCopy(a, keySpace - GetSize(a), b, keySpace - GetSize(b), GetSize(b), 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
db.FreePage(GetKeyStrOid(pg, r + 1));
SetKeyStrOid(pg, r + 1, GetKeyStrOid(pg, r));
return RemoveStrKey(pg, r);
}
}
else
{
// page b is before a
Page b = db.GetPage(GetKeyStrOid(pg, r - 1));
int bn = GetItemsCount(b);
int merged_size = (an + bn) * strKeySize + GetSize(a) + GetSize(b);
if (height != 1)
{
merged_size += GetKeyStrSize(pg, r - 1) * 2 + strKeySize * 2;
}
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i, j, k, len;
db.pool.Unfix(b);
b = db.PutPage(GetKeyStrOid(pg, r - 1));
int size_a = GetSize(a);
int size_b = GetSize(b);
int addSize, subSize;
if (height != 1)
{
addSize = GetKeyStrSize(pg, r - 1);
subSize = GetKeyStrSize(b, bn - 1);
}
else
{
addSize = subSize = GetKeyStrSize(b, bn - 1);
}
i = 0;
int prevDelta = (an * strKeySize + size_a) - (bn * strKeySize + size_b);
while (true)
{
i += 1;
int delta = ((an + i) * strKeySize + size_a + addSize * 2) - ((bn - i) * strKeySize + size_b - subSize * 2);
if (delta >= 0)
{
if (delta >= -prevDelta)
{
i -= 1;
}
break;
}
prevDelta = delta;
size_a += addSize * 2;
size_b -= subSize * 2;
if (height != 1)
{
addSize = subSize;
subSize = GetKeyStrSize(b, bn - i - 1);
}
else
{
addSize = subSize = GetKeyStrSize(b, bn - i - 1);
}
}
int result = Btree.op_done;
if (i > 0)
{
k = i;
Assert.That(i < bn);
if (height != 1)
{
SetSize(b, GetSize(b) - GetKeyStrSize(b, bn - k) * 2);
MemCopy(a, i, a, 0, an + 1, strKeySize);
k -= 1;
SetKeyStrOid(a, k, GetKeyStrOid(b, bn));
len = GetKeyStrSize(pg, r - 1);
SetKeyStrSize(a, k, len);
SetSize(a, GetSize(a) + len * 2);
SetKeyStrOffs(a, k, keySpace - GetSize(a));
MemCopy(a, GetKeyStrOffs(a, k), pg, GetKeyStrOffs(pg, r - 1), len * 2, 1);
}
else
{
MemCopy(a, i, a, 0, an, strKeySize);
}
for (j = 0; j < k; j++)
{
len = GetKeyStrSize(b, bn - k + j);
SetSize(a, GetSize(a) + len * 2);
SetSize(b, GetSize(b) - len * 2);
SetKeyStrOffs(a, j, keySpace - GetSize(a));
SetKeyStrSize(a, j, len);
SetKeyStrOid(a, j, GetKeyStrOid(b, bn - k + j));
MemCopy(a, GetKeyStrOffs(a, j), b, GetKeyStrOffs(b, bn - k + j), len * 2, 1);
}
an += i;
SetItemsCount(a, an);
rem.GetStr(b, bn - k - 1);
result = ReplaceStrKey(db, pg, r - 1, rem, height);
SetItemsCount(b, CompactifyStrings(b, -i));
}
db.pool.Unfix(a);
db.pool.Unfix(b);
return result;
}
else
{
// merge page b to a
if (height != 1)
{
MemCopy(a, bn + 1, a, 0, an + 1, strKeySize);
int len = GetKeyStrSize(pg, r - 1);
SetKeyStrSize(a, bn, len);
SetSize(a, GetSize(a) + len * 2);
SetKeyStrOffs(a, bn, keySpace - GetSize(a));
SetKeyStrOid(a, bn, GetKeyStrOid(b, bn));
MemCopy(a, GetKeyStrOffs(a, bn), pg, GetKeyStrOffs(pg, r - 1), len * 2, 1);
an += 1;
}
else
{
MemCopy(a, bn, a, 0, an, strKeySize);
}
for (int i = 0; i < bn; i++)
{
SetKeyStrOid(a, i, GetKeyStrOid(b, i));
SetKeyStrSize(a, i, GetKeyStrSize(b, i));
SetKeyStrOffs(a, i, GetKeyStrOffs(b, i) - GetSize(a));
}
an += bn;
SetItemsCount(a, an);
SetSize(a, GetSize(a) + GetSize(b));
MemCopy(a, keySpace - GetSize(a), b, keySpace - GetSize(b), GetSize(b), 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
db.FreePage(GetKeyStrOid(pg, r - 1));
return RemoveStrKey(pg, r - 1);
}
}
}
else if (type == ClassDescriptor.tpArrayOfByte)
{
Page a = db.PutPage(GetKeyStrOid(pg, r));
int an = GetItemsCount(a);
if (r < nItems)
{
// exists greater page
Page b = db.GetPage(GetKeyStrOid(pg, r + 1));
int bn = GetItemsCount(b);
int merged_size = (an + bn) * strKeySize + GetSize(a) + GetSize(b);
if (height != 1)
{
merged_size += GetKeyStrSize(pg, r) + strKeySize * 2;
}
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i, j, k;
db.pool.Unfix(b);
b = db.PutPage(GetKeyStrOid(pg, r + 1));
int size_a = GetSize(a);
int size_b = GetSize(b);
int addSize, subSize;
if (height != 1)
{
addSize = GetKeyStrSize(pg, r);
subSize = GetKeyStrSize(b, 0);
}
else
{
addSize = subSize = GetKeyStrSize(b, 0);
}
i = 0;
int prevDelta = (an * strKeySize + size_a) - (bn * strKeySize + size_b);
while (true)
{
i += 1;
int delta = ((an + i) * strKeySize + size_a + addSize) - ((bn - i) * strKeySize + size_b - subSize);
if (delta >= 0)
{
if (delta >= -prevDelta)
{
i -= 1;
}
break;
}
size_a += addSize;
size_b -= subSize;
prevDelta = delta;
if (height != 1)
{
addSize = subSize;
subSize = GetKeyStrSize(b, i);
}
else
{
addSize = subSize = GetKeyStrSize(b, i);
}
}
int result = Btree.op_done;
if (i > 0)
{
k = i;
if (height != 1)
{
int len = GetKeyStrSize(pg, r);
SetSize(a, GetSize(a) + len);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
SetKeyStrSize(a, an, len);
MemCopy(a, GetKeyStrOffs(a, an), pg, GetKeyStrOffs(pg, r), len, 1);
k -= 1;
an += 1;
SetKeyStrOid(a, an + k, GetKeyStrOid(b, k));
SetSize(b, GetSize(b) - GetKeyStrSize(b, k));
}
for (j = 0; j < k; j++)
{
int len = GetKeyStrSize(b, j);
SetSize(a, GetSize(a) + len);
SetSize(b, GetSize(b) - len);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
SetKeyStrSize(a, an, len);
SetKeyStrOid(a, an, GetKeyStrOid(b, j));
MemCopy(a, GetKeyStrOffs(a, an), b, GetKeyStrOffs(b, j), len, 1);
an += 1;
}
rem.GetByteArray(b, i - 1);
result = ReplaceByteArrayKey(db, pg, r, rem, height);
SetItemsCount(a, an);
SetItemsCount(b, CompactifyByteArrays(b, i));
}
db.pool.Unfix(a);
db.pool.Unfix(b);
return result;
}
else
{
// merge page b to a
if (height != 1)
{
int r_len = GetKeyStrSize(pg, r);
SetKeyStrSize(a, an, r_len);
SetSize(a, GetSize(a) + r_len);
SetKeyStrOffs(a, an, keySpace - GetSize(a));
MemCopy(a, GetKeyStrOffs(a, an), pg, GetKeyStrOffs(pg, r), r_len, 1);
an += 1;
SetKeyStrOid(a, an + bn, GetKeyStrOid(b, bn));
}
for (int i = 0; i < bn; i++, an++)
{
SetKeyStrSize(a, an, GetKeyStrSize(b, i));
SetKeyStrOffs(a, an, GetKeyStrOffs(b, i) - GetSize(a));
SetKeyStrOid(a, an, GetKeyStrOid(b, i));
}
SetSize(a, GetSize(a) + GetSize(b));
SetItemsCount(a, an);
MemCopy(a, keySpace - GetSize(a), b, keySpace - GetSize(b), GetSize(b), 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
db.FreePage(GetKeyStrOid(pg, r + 1));
SetKeyStrOid(pg, r + 1, GetKeyStrOid(pg, r));
return RemoveByteArrayKey(pg, r);
}
}
else
{
// page b is before a
Page b = db.GetPage(GetKeyStrOid(pg, r - 1));
int bn = GetItemsCount(b);
int merged_size = (an + bn) * strKeySize + GetSize(a) + GetSize(b);
if (height != 1)
{
merged_size += GetKeyStrSize(pg, r - 1) + strKeySize * 2;
}
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i, j, k, len;
db.pool.Unfix(b);
b = db.PutPage(GetKeyStrOid(pg, r - 1));
int size_a = GetSize(a);
int size_b = GetSize(b);
int addSize, subSize;
if (height != 1)
{
addSize = GetKeyStrSize(pg, r - 1);
subSize = GetKeyStrSize(b, bn - 1);
}
else
{
addSize = subSize = GetKeyStrSize(b, bn - 1);
}
i = 0;
int prevDelta = (an * strKeySize + size_a) - (bn * strKeySize + size_b);
while (true)
{
i += 1;
int delta = ((an + i) * strKeySize + size_a + addSize) - ((bn - i) * strKeySize + size_b - subSize);
if (delta >= 0)
{
if (delta >= -prevDelta)
{
i -= 1;
}
break;
}
prevDelta = delta;
size_a += addSize;
size_b -= subSize;
if (height != 1)
{
addSize = subSize;
subSize = GetKeyStrSize(b, bn - i - 1);
}
else
{
addSize = subSize = GetKeyStrSize(b, bn - i - 1);
}
}
int result = Btree.op_done;
if (i > 0)
{
k = i;
Assert.That(i < bn);
if (height != 1)
{
SetSize(b, GetSize(b) - GetKeyStrSize(b, bn - k));
MemCopy(a, i, a, 0, an + 1, strKeySize);
k -= 1;
SetKeyStrOid(a, k, GetKeyStrOid(b, bn));
len = GetKeyStrSize(pg, r - 1);
SetKeyStrSize(a, k, len);
SetSize(a, GetSize(a) + len);
SetKeyStrOffs(a, k, keySpace - GetSize(a));
MemCopy(a, GetKeyStrOffs(a, k), pg, GetKeyStrOffs(pg, r - 1), len, 1);
}
else
{
MemCopy(a, i, a, 0, an, strKeySize);
}
for (j = 0; j < k; j++)
{
len = GetKeyStrSize(b, bn - k + j);
SetSize(a, GetSize(a) + len);
SetSize(b, GetSize(b) - len);
SetKeyStrOffs(a, j, keySpace - GetSize(a));
SetKeyStrSize(a, j, len);
SetKeyStrOid(a, j, GetKeyStrOid(b, bn - k + j));
MemCopy(a, GetKeyStrOffs(a, j), b, GetKeyStrOffs(b, bn - k + j), len, 1);
}
an += i;
SetItemsCount(a, an);
rem.GetByteArray(b, bn - k - 1);
result = ReplaceByteArrayKey(db, pg, r - 1, rem, height);
SetItemsCount(b, CompactifyByteArrays(b, -i));
}
db.pool.Unfix(a);
db.pool.Unfix(b);
return result;
}
else
{
// merge page b to a
if (height != 1)
{
MemCopy(a, bn + 1, a, 0, an + 1, strKeySize);
int len = GetKeyStrSize(pg, r - 1);
SetKeyStrSize(a, bn, len);
SetSize(a, GetSize(a) + len);
SetKeyStrOffs(a, bn, keySpace - GetSize(a));
SetKeyStrOid(a, bn, GetKeyStrOid(b, bn));
MemCopy(a, GetKeyStrOffs(a, bn), pg, GetKeyStrOffs(pg, r - 1), len, 1);
an += 1;
}
else
{
MemCopy(a, bn, a, 0, an, strKeySize);
}
for (int i = 0; i < bn; i++)
{
SetKeyStrOid(a, i, GetKeyStrOid(b, i));
SetKeyStrSize(a, i, GetKeyStrSize(b, i));
SetKeyStrOffs(a, i, GetKeyStrOffs(b, i) - GetSize(a));
}
an += bn;
SetItemsCount(a, an);
SetSize(a, GetSize(a) + GetSize(b));
MemCopy(a, keySpace - GetSize(a), b, keySpace - GetSize(b), GetSize(b), 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
db.FreePage(GetKeyStrOid(pg, r - 1));
return RemoveByteArrayKey(pg, r - 1);
}
}
}
else
{
// scalar types
Page a = db.PutPage(GetReference(pg, maxItems - r - 1));
int an = GetItemsCount(a);
int itemSize = ClassDescriptor.Sizeof[type];
if (r < nItems)
{
// exists greater page
Page b = db.GetPage(GetReference(pg, maxItems - r - 2));
int bn = GetItemsCount(b);
Assert.That(bn >= an);
if (height != 1)
{
MemCopy(a, an, pg, r, 1, itemSize);
an += 1;
bn += 1;
}
int merged_size = (an + bn) * (4 + itemSize);
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i = bn - ((an + bn) >> 1);
db.pool.Unfix(b);
b = db.PutPage(GetReference(pg, maxItems - r - 2));
MemCopy(a, an, b, 0, i, itemSize);
MemCopy(b, 0, b, i, bn - i, itemSize);
MemCopy(a, maxItems - an - i, b, maxItems - i, i, 4);
MemCopy(b, maxItems - bn + i, b, maxItems - bn, bn - i, 4);
MemCopy(pg, r, a, an + i - 1, 1, itemSize);
SetItemsCount(b, GetItemsCount(b) - i);
SetItemsCount(a, GetItemsCount(a) + i);
db.pool.Unfix(a);
db.pool.Unfix(b);
return Btree.op_done;
}
else
{
// merge page b to a
MemCopy(a, an, b, 0, bn, itemSize);
MemCopy(a, maxItems - an - bn, b, maxItems - bn, bn, 4);
db.FreePage(GetReference(pg, maxItems - r - 2));
MemCopy(pg, maxItems - nItems, pg, maxItems - nItems - 1, nItems - r - 1, 4);
MemCopy(pg, r, pg, r + 1, nItems - r - 1, itemSize);
SetItemsCount(a, GetItemsCount(a) + bn);
SetItemsCount(pg, nItems - 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
return nItems * (itemSize + 4) < keySpace / 2 ? Btree.op_underflow : Btree.op_done;
}
}
else
{
// page b is before a
Page b = db.GetPage(GetReference(pg, maxItems - r));
int bn = GetItemsCount(b);
Assert.That(bn >= an);
if (height != 1)
{
an += 1;
bn += 1;
}
int merged_size = (an + bn) * (4 + itemSize);
if (merged_size > keySpace)
{
// reallocation of nodes between pages a and b
int i = bn - ((an + bn) >> 1);
db.pool.Unfix(b);
b = db.PutPage(GetReference(pg, maxItems - r));
MemCopy(a, i, a, 0, an, itemSize);
MemCopy(a, 0, b, bn - i, i, itemSize);
MemCopy(a, maxItems - an - i, a, maxItems - an, an, 4);
MemCopy(a, maxItems - i, b, maxItems - bn, i, 4);
if (height != 1)
{
MemCopy(a, i - 1, pg, r - 1, 1, itemSize);
}
MemCopy(pg, r - 1, b, bn - i - 1, 1, itemSize);
SetItemsCount(b, GetItemsCount(b) - i);
SetItemsCount(a, GetItemsCount(a) + i);
db.pool.Unfix(a);
db.pool.Unfix(b);
return Btree.op_done;
}
else
{
// merge page b to a
MemCopy(a, bn, a, 0, an, itemSize);
MemCopy(a, 0, b, 0, bn, itemSize);
MemCopy(a, maxItems - an - bn, a, maxItems - an, an, 4);
MemCopy(a, maxItems - bn, b, maxItems - bn, bn, 4);
if (height != 1)
{
MemCopy(a, bn - 1, pg, r - 1, 1, itemSize);
}
db.FreePage(GetReference(pg, maxItems - r));
SetReference(pg, maxItems - r, GetReference(pg, maxItems - r - 1));
SetItemsCount(a, GetItemsCount(a) + bn);
SetItemsCount(pg, nItems - 1);
db.pool.Unfix(a);
db.pool.Unfix(b);
return nItems * (itemSize + 4) < keySpace / 2 ? Btree.op_underflow : Btree.op_done;
}
}
}
}
internal static int InsertByteArrayKey(StorageImpl db, Page pg, int r, BtreeKey ins, int height)
{
int nItems = GetItemsCount(pg);
int size = GetSize(pg);
int n = (height != 0) ? nItems + 1 : nItems;
byte[] bval = (byte[]) ins.key.oval;
// insert before e[r]
int len = bval.Length;
if (size + len + (n + 1) * strKeySize <= keySpace)
{
MemCopy(pg, r + 1, pg, r, n - r, strKeySize);
size += len;
SetKeyStrOffs(pg, r, keySpace - size);
SetKeyStrSize(pg, r, len);
SetKeyStrOid(pg, r, ins.oid);
SetKeyBytes(pg, keySpace - size, bval);
nItems += 1;
}
else
{
// page is full then divide page
int pageId = db.AllocatePage();
Page b = db.PutPage(pageId);
int moved = 0;
int inserted = len + strKeySize;
int prevDelta = (1 << 31) + 1;
for (int bn = 0, i = 0; ; bn += 1)
{
int addSize, subSize;
int j = nItems - i - 1;
int keyLen = GetKeyStrSize(pg, i);
if (bn == r)
{
keyLen = len;
inserted = 0;
addSize = len;
if (height == 0)
{
subSize = 0;
j += 1;
}
else
{
subSize = GetKeyStrSize(pg, i);
}
}
else
{
addSize = subSize = keyLen;
if (height != 0)
{
if (i + 1 != r)
{
subSize += GetKeyStrSize(pg, i + 1);
j -= 1;
}
else
{
inserted = 0;
}
}
}
int delta = (moved + addSize + (bn + 1) * strKeySize) - (j * strKeySize + size - subSize + inserted);
if (delta >= -prevDelta)
{
if (height == 0)
{
ins.GetByteArray(b, bn - 1);
}
else
{
Assert.That("String fits in the B-Tree page", moved + (bn + 1) * strKeySize <= keySpace);
if (bn != r)
{
ins.GetByteArray(pg, i);
SetKeyStrOid(b, bn, GetKeyStrOid(pg, i));
size -= keyLen;
i += 1;
}
else
{
SetKeyStrOid(b, bn, ins.oid);
}
}
nItems = CompactifyByteArrays(pg, i);
if (bn < r || (bn == r && height == 0))
{
MemCopy(pg, r - i + 1, pg, r - i, n - r, strKeySize);
size += len;
nItems += 1;
Assert.That("String fits in the B-Tree page", size + (n - i + 1) * strKeySize <= keySpace);
SetKeyStrOffs(pg, r - i, keySpace - size);
SetKeyStrSize(pg, r - i, len);
SetKeyStrOid(pg, r - i, ins.oid);
SetKeyBytes(pg, keySpace - size, bval);
}
SetItemsCount(b, bn);
SetSize(b, moved);
SetSize(pg, size);
SetItemsCount(pg, nItems);
ins.oid = pageId;
db.pool.Unfix(b);
return Btree.op_overflow;
}
moved += keyLen;
prevDelta = delta;
Assert.That("String fits in the B-Tree page", moved + (bn + 1) * strKeySize <= keySpace);
SetKeyStrSize(b, bn, keyLen);
SetKeyStrOffs(b, bn, keySpace - moved);
if (bn == r)
{
SetKeyStrOid(b, bn, ins.oid);
SetKeyBytes(b, keySpace - moved, bval);
}
else
{
SetKeyStrOid(b, bn, GetKeyStrOid(pg, i));
MemCopy(b, keySpace - moved, pg, GetKeyStrOffs(pg, i), keyLen, 1);
size -= keyLen;
i += 1;
}
}
}
SetItemsCount(pg, nItems);
SetSize(pg, size);
return size + strKeySize * (nItems + 1) < keySpace / 2 ? Btree.op_underflow : Btree.op_done;
}