arena := mheap_.arenas[ai.l1()][ai.l2()]
		bitmap := arena.checkmarks

		if bitmap == nil {
			// Allocate bitmap on first use.
			bitmap = (*checkmarksMap)(persistentalloc(unsafe.Sizeof(*bitmap), 0, &memstats.gcMiscSys))
			if bitmap == nil {
				throw("out of memory allocating checkmarks bitmap")
			}
			arena.checkmarks = bitmap
		} else {
			// Otherwise clear the existing bitmap.
			clear(bitmap.b[:])
		}
	}

// then s.heapBits() returns a slice containing the bitmap for the whole span.
// That is, s.heapBits()[0] holds the goarch.PtrSize*8 bits for the first
// goarch.PtrSize*8 words from "start" through "start+63*ptrSize" in the span.
// On a related note, small objects are always small enough that their bitmap
// fits in goarch.PtrSize*8 bits, so writing out bitmap data takes two bitmap
// writes at most (because object boundaries don't generally lie on

// license that can be found in the LICENSE file.

package runtime

import (
	"runtime/internal/sys"
)

// pageBits is a bitmap representing one bit per page in a palloc chunk.
type pageBits [pallocChunkPages / 64]uint64

// get returns the value of the i'th bit in the bitmap.
func (b *pageBits) get(i uint) uint {
	return uint((b[i/64] >> (i % 64)) & 1)
}

	// Flush mask to the memory bitmap.
	idx := h.offset / (ptrBits * goarch.PtrSize)
	m := uintptr(1)<<h.low - 1
	bitmap := s.heapBits()
	bitmap[idx] = bswapIfBigEndian(bswapIfBigEndian(bitmap[idx])&m | data)
	// Note: no synchronization required for this write because
	// the allocator has exclusive access to the page, and the bitmap
	// entries are all for a single page. Also, visibility of these

	argSize = abid.stackCallArgsSize
	retOffset = abid.retOffset
	frametype = toType(ft)

	// Expand stack pointer bitmap into byte-map.
	for i := uint32(0); i < abid.stackPtrs.n; i++ {
		stack = append(stack, abid.stackPtrs.data[i/8]>>(i%8)&1)
	}

	// Expand register pointer bitmaps into byte-maps.
	bool2byte := func(b bool) byte {
		if b {
			return 1
		}
		return 0
	}
	for i := 0; i < intArgRegs; i++ {

	stackCallArgsSize, retOffset, spill uintptr

	// stackPtrs is a bitmap that indicates whether
	// each word in the ABI stack space (stack-assigned
	// args + return values) is a pointer. Used
	// as the heap pointer bitmap for stack space
	// passed to reflectcall.
	stackPtrs *bitVector

	// inRegPtrs is a bitmap whose i'th bit indicates
	// whether the i'th integer argument register contains

//
// Pages are managed using a bitmap that is sharded into chunks.
// In the bitmap, 1 means in-use, and 0 means free. The bitmap spans the
// process's address space. Chunks are managed in a sparse-array-style structure
// similar to mheap.arenas, since the bitmap may be large on some systems.
//
// The bitmap is efficiently searched by using a radix tree in combination

}

// return current length of bitmap in bits.
func (bm Bitmap) Len() int {
	return len(bm) * 32
}

// return the number of bits set.
func (bm Bitmap) Count() int {
	s := 0
	for _, x := range bm {
		s += bits.OnesCount32(x)
	}
	return s
}

func MakeBitmap(n int) Bitmap {
	return make(Bitmap, (n+31)/32)
}

// growBitmap insures that the specified bitmap has enough capacity,

)

// MaxPtrmaskBytes is the maximum length of a GC ptrmask bitmap,
// which holds 1-bit entries describing where pointers are in a given type.
// Above this length, the GC information is recorded as a GC program,
// which can express repetition compactly. In either form, the
// information is used by the runtime to initialize the heap bitmap,
// and for large types (like 128 or more words), they are roughly the

	}

	// Allocate a port inside the valid port range
	if err := storage.Allocate(30100); err != nil {
		t.Fatal(err)
	}

	// Try to allocate the same port in the local bitmap
	// The local bitmap stores the offset of the port
	// offset = port - base (30100 - 30000 = 100)
	ok, err := backing.Allocate(100)
	if err != nil {
		t.Fatal(err)
	}