const (

	// A malloc header is functionally a single type pointer, but
	// we need to use 8 here to ensure 8-byte alignment of allocations
	// on 32-bit platforms. It's wasteful, but a lot of code relies on
	// 8-byte alignment for 8-byte atomics.
	MallocHeaderSize = 8

	// The minimum object size that has a malloc header, exclusive.
	//
	// The size of this value controls overheads from the malloc header.
	// The minimum size is bound by writeHeapBitsSmall, which assumes that the
	// pointer bitmap for objects of a size smaller than this doesn't cross
	// more than one pointer-word boundary. This sets an upper-bound on this
	// value at the number of bits in a uintptr, multiplied by the pointer
	// size in bytes.
	//
	// We choose a value here that has a natural cutover point in terms of memory
	// overheads. This value just happens to be the maximum possible value this
	// can be.
	//
	// A span with heap bits in it will have 128 bytes of heap bits on 64-bit
	// platforms, and 256 bytes of heap bits on 32-bit platforms. The first size
	// class where malloc headers match this overhead for 64-bit platforms is
	// 512 bytes (8 KiB / 512 bytes * 8 bytes-per-header = 128 bytes of overhead).
	// On 32-bit platforms, this same point is the 256 byte size class
	// (8 KiB / 256 bytes * 8 bytes-per-header = 256 bytes of overhead).
	//
	// Guaranteed to be exactly at a size class boundary. The reason this value is
	// an exclusive minimum is subtle. Suppose we're allocating a 504-byte object
	// and its rounded up to 512 bytes for the size class. If minSizeForMallocHeader
	// is 512 and an inclusive minimum, then a comparison against minSizeForMallocHeader
	// by the two values would produce different results. In other words, the comparison
	// would not be invariant to size-class rounding. Eschewing this property means a
	// more complex check or possibly storing additional state to determine whether a
	// span has malloc headers.
	MinSizeForMallocHeader = goarch.PtrSize * ptrBits

	// PageSize is the increment in which spans are managed.
	PageSize = 1 << PageShift
)

const (
	MinHeapAlign   = 8
	MaxSmallSize   = 32768
	SmallSizeDiv   = 8
	SmallSizeMax   = 1024
	LargeSizeDiv   = 128
	NumSizeClasses = 68
	PageShift      = 13
	MaxObjsPerSpan = 1024
)

var SizeClassToDivMagic = [NumSizeClasses]uint32{0, ^uint32(0)/8 + 1, ^uint32(0)/16 + 1, ^uint32(0)/24 + 1, ^uint32(0)/32 + 1, ^uint32(0)/48 + 1, ^uint32(0)/64 + 1, ^uint32(0)/80 + 1, ^uint32(0)/96 + 1, ^uint32(0)/112 + 1, ^uint32(0)/128 + 1, ^uint32(0)/144 + 1, ^uint32(0)/160 + 1, ^uint32(0)/176 + 1, ^uint32(0)/192 + 1, ^uint32(0)/208 + 1, ^uint32(0)/224 + 1, ^uint32(0)/240 + 1, ^uint32(0)/256 + 1, ^uint32(0)/288 + 1, ^uint32(0)/320 + 1, ^uint32(0)/352 + 1, ^uint32(0)/384 + 1, ^uint32(0)/416 + 1, ^uint32(0)/448 + 1, ^uint32(0)/480 + 1, ^uint32(0)/512 + 1, ^uint32(0)/576 + 1, ^uint32(0)/640 + 1, ^uint32(0)/704 + 1, ^uint32(0)/768 + 1, ^uint32(0)/896 + 1, ^uint32(0)/1024 + 1, ^uint32(0)/1152 + 1, ^uint32(0)/1280 + 1, ^uint32(0)/1408 + 1, ^uint32(0)/1536 + 1, ^uint32(0)/1792 + 1, ^uint32(0)/2048 + 1, ^uint32(0)/2304 + 1, ^uint32(0)/2688 + 1, ^uint32(0)/3072 + 1, ^uint32(0)/3200 + 1, ^uint32(0)/3456 + 1, ^uint32(0)/4096 + 1, ^uint32(0)/4864 + 1, ^uint32(0)/5376 + 1, ^uint32(0)/6144 + 1, ^uint32(0)/6528 + 1, ^uint32(0)/6784 + 1, ^uint32(0)/6912 + 1, ^uint32(0)/8192 + 1, ^uint32(0)/9472 + 1, ^uint32(0)/9728 + 1, ^uint32(0)/10240 + 1, ^uint32(0)/10880 + 1, ^uint32(0)/12288 + 1, ^uint32(0)/13568 + 1, ^uint32(0)/14336 + 1, ^uint32(0)/16384 + 1, ^uint32(0)/18432 + 1, ^uint32(0)/19072 + 1, ^uint32(0)/20480 + 1, ^uint32(0)/21760 + 1, ^uint32(0)/24576 + 1, ^uint32(0)/27264 + 1, ^uint32(0)/28672 + 1, ^uint32(0)/32768 + 1}

var SizeClassToNPages = [NumSizeClasses]uint8{0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 3, 2, 3, 1, 3, 2, 3, 4, 5, 6, 1, 7, 6, 5, 4, 3, 5, 7, 2, 9, 7, 5, 8, 3, 10, 7, 4}

var SizeClassToSize = [NumSizeClasses]uint16{0, 8, 16, 24, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, 240, 256, 288, 320, 352, 384, 416, 448, 480, 512, 576, 640, 704, 768, 896, 1024, 1152, 1280, 1408, 1536, 1792, 2048, 2304, 2688, 3072, 3200, 3456, 4096, 4864, 5376, 6144, 6528, 6784, 6912, 8192, 9472, 9728, 10240, 10880, 12288, 13568, 14336, 16384, 18432, 19072, 20480, 21760, 24576, 27264, 28672, 32768}

var SizeToSizeClass128 = [(MaxSmallSize-SmallSizeMax)/LargeSizeDiv + 1]uint8{ /* 249 elements not displayed */ }

var SizeToSizeClass8 = [SmallSizeMax/SmallSizeDiv + 1]uint8{ /* 129 elements not displayed */ }

type ObjMask [MaxObjsPerSpan / (goarch.PtrSize * 8)]uintptr

type PtrMask [PageSize / goarch.PtrSize / (goarch.PtrSize * 8)]uintptr