// Initializes the content of a page.
func (page *Page) Init(specialSize uintptr) {
copy(page.bytes[:], _PageZero)
specialSize = system.MaxAlign(specialSize)
offsetSpecial := uint16(system.BlockSize - specialSize)
page.SetLower(sizeOfPageHeader)
page.SetUpper(offsetSpecial)
page.SetSpecial(offsetSpecial)
page.SetPageSizeAndVersion(system.BlockSize, LayoutVersion)
}
func FormHeapTuple(values []system.Datum, tupdesc *TupleDesc) *HeapTuple {
natts := len(tupdesc.Attrs)
hasnull := false
for _, value := range values {
if value == nil {
hasnull = true
//} else if att.attlen == -1
// TODO: flatten toast value
}
}
length := unsafe.Offsetof(HeapTupleHeader{}.bits)
if hasnull {
length += uintptr(bitmapLength(natts))
}
if tupdesc.hasOid {
length += unsafe.Sizeof(system.Oid(0))
}
length = system.MaxAlign(length)
hoff := uint8(length)
data_len := computeHeapDataSize(values, tupdesc)
length += data_len
tuple_data := make([]byte, length)
tuple := &HeapTuple{
tupdesc: tupdesc,
tableOid: system.InvalidOid,
}
tuple.SetData(tuple_data, system.InvalidItemPointer)
td := tuple.data
td.SetNatts(system.AttrNumber(natts))
td.hoff = hoff
if tupdesc.hasOid {
td.infomask = heapHasOid
}
bits := []byte(nil)
if hasnull {
bits = tuple.bytes[unsafe.Offsetof(td.bits):hoff]
}
data := tuple.bytes[hoff:]
td.fill(values, tupdesc, bits, data)
return tuple
}
func (page *Page) AddItem(item []byte, offset system.OffsetNumber, overwrite, is_heap bool) system.OffsetNumber {
// Be wary about corrupted page pointers
if page.Lower() < sizeOfPageHeader ||
page.Lower() > page.Upper() ||
page.Upper() > page.Special() ||
page.Special() > system.BlockSize {
log.Panicf("corrupted page pointers: lower = %d, upper = %d, special = %d",
page.Lower(), page.Upper(), page.Special())
}
// Select offset to place the new item at
limit := page.MaxOffsetNumber().Next()
needshuffle := false
// was offset passed in?
if offset.IsValid() {
// yes, check it
if overwrite {
if offset < limit {
itemId := page.ItemId(offset)
if itemId.IsUsed() || itemId.HasStorage() {
log.Println("WARNING: will not overwrite a used ItemId")
return system.InvalidOffsetNumber
}
}
} else {
if offset < limit {
// need to move existing linp's
needshuffle = true
}
}
} else {
if page.HasFreeLinePointers() {
for offset = 1; offset < limit; offset = offset.Next() {
itemId := page.ItemId(offset)
if !itemId.IsUsed() && !itemId.HasStorage() {
break
}
}
if offset >= limit {
page.ClearHasFreeLinePointers()
}
} else {
// don't bother searching if hint says there's no free slot
offset = limit
}
}
if offset > limit {
log.Println("WARNING: specified item offset is too large")
return system.InvalidOffsetNumber
}
// if is_heap && offset > MaxHeapTuplesPerPage {
// log.Println("WARNING: can't put more than MaxHeapTuplesPerPage items in a heap page")
// return InvalidOffsetNumber
// }
// Compute new lower and upper pointers for page, see if it'll fit.
// Note: do arithmetic as signed ints, to avoid mistakes if, say,
// alignedSize > upper.
lower := int(page.Lower())
if offset == limit || needshuffle {
lower = lower + int(unsafe.Sizeof(ItemId(0)))
}
alignedSize := system.MaxAlign(uintptr(len(item)))
upper := int(page.Upper()) - int(alignedSize)
if lower > upper {
return system.InvalidOffsetNumber
}
// OK to insert the item. First, shuffle the existing pointers if needed.
itemId := page.ItemId(offset)
if needshuffle {
destItemId := page.ItemId(offset + 1)
base := uintptr(unsafe.Pointer(&page.bytes[0]))
destStart := uintptr(unsafe.Pointer(destItemId)) - base
srcStart := uintptr(unsafe.Pointer(itemId)) - base
copyLen := uintptr(limit-offset) * unsafe.Sizeof(ItemId(0))
dest := page.bytes[destStart : destStart+copyLen]
src := page.bytes[srcStart : srcStart+copyLen]
copy(dest, src)
}
// set the item pointer
itemId.SetNormal(uint(upper), uint(len(item)))
// copy the item's data onto the page
if l := copy(page.bytes[upper:], item); l != len(item) {
panic("unexpected copy result")
}
page.SetLower(uint16(lower))
page.SetUpper(uint16(upper))
return offset
}
