//
// See malloc.go for overview.

package runtime

import (
	"runtime/internal/sys"
	"unsafe"
)

// fixalloc is a simple free-list allocator for fixed size objects.
// Malloc uses a FixAlloc wrapped around sysAlloc to manage its
// mcache and mspan objects.
//
// Memory returned by fixalloc.alloc is zeroed by default, but the
// caller may take responsibility for zeroing allocations by setting

// to these types must always fail the `runtime.inheap` check. The type may be used
// for global variables, or for objects in unmanaged memory (e.g., allocated with
// `sysAlloc`, `persistentalloc`, r`fixalloc`, or from a manually-managed span).
//
// Specifically:
//
// 1. `new(T)`, `make([]T)`, `append([]T, ...)` and implicit heap
// allocation of T are disallowed. (Though implicit allocations are

  sysAlloc to avoid fragmentation. However, there is no way to free
  persistentalloced objects (hence the name).

* fixalloc is a SLAB-style allocator that allocates objects of a fixed
  size. fixalloced objects can be freed, but this memory can only be
  reused by the same fixalloc pool, so it can only be reused for
  objects of the same type.

In general, types that are allocated using any of these should be

	}

	spanalloc              fixalloc // allocator for span*
	cachealloc             fixalloc // allocator for mcache*
	specialfinalizeralloc  fixalloc // allocator for specialfinalizer*
	specialprofilealloc    fixalloc // allocator for specialprofile*
	specialReachableAlloc  fixalloc // allocator for specialReachable
	specialPinCounterAlloc fixalloc // allocator for specialPinCounter

	// maxAlloc is the maximum size of an allocation. On 64-bit,
	// it's theoretically possible to allocate 1<<heapAddrBits bytes. On
	// 32-bit, however, this is one less than 1<<32 because the
	// number of bytes in the address space doesn't actually fit
	// in a uintptr.
	maxAlloc = (1 << heapAddrBits) - (1-_64bit)*1

		capmem = roundupsize(uintptr(newcap), noscan)
		overflow = uintptr(newcap) > maxAlloc
		newcap = int(capmem)
	case et.Size_ == goarch.PtrSize:
		lenmem = uintptr(oldLen) * goarch.PtrSize
		newlenmem = uintptr(newLen) * goarch.PtrSize
		capmem = roundupsize(uintptr(newcap)*goarch.PtrSize, noscan)
		overflow = uintptr(newcap) > maxAlloc/goarch.PtrSize
		newcap = int(capmem / goarch.PtrSize)
	case isPowerOfTwo(et.Size_):

	*(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)}
	return
}

// rawruneslice allocates a new rune slice. The rune slice is not zeroed.
func rawruneslice(size int) (b []rune) {
	if uintptr(size) > maxAlloc/4 {
		throw("out of memory")
	}
	mem := roundupsize(uintptr(size)*4, true)
	p := mallocgc(mem, nil, false)
	if mem != uintptr(size)*4 {
		memclrNoHeapPointers(add(p, uintptr(size)*4), mem-uintptr(size)*4)
	}

	return alloc
}

func TestFairAlloc(t *testing.T) {
	if e, a := []float64{0, 0}, fairAlloc([]float64{0, 0}, 42); !reflect.DeepEqual(e, a) {
		t.Errorf("Expected %#+v, got #%+v", e, a)
	}
	if e, a := []float64{42, 0}, fairAlloc([]float64{47, 0}, 42); !reflect.DeepEqual(e, a) {
		t.Errorf("Expected %#+v, got #%+v", e, a)
	}
	if e, a := []float64{1, 41}, fairAlloc([]float64{1, 47}, 42); !reflect.DeepEqual(e, a) {

	// If we are running on the system stack then dst might be an
	// address on the stack, which is OK.
	gp := getg()
	if gp == gp.m.g0 || gp == gp.m.gsignal {
		return
	}

	// Allocating memory can write to various mfixalloc structs
	// that look like they are non-Go memory.
	if gp.m.mallocing != 0 {
		return
	}

	// If the object is pinned, it's safe to store it in C memory. The GC
	// ensures it will not be moved or freed.

    kFree = 1,
    kRead = 2,
    kWrite = 3
  };

 public:
  bool IsAlloc() const { return effects_.test(kAlloc); }
  bool IsFree() const { return effects_.test(kFree); }
  bool IsRead() const { return effects_.test(kRead); }
  bool IsWrite() const { return effects_.test(kWrite); }
  bool IsAllocOnly() const { return IsAlloc() && effects_.count() == 1; }
  bool IsReadOnly() const { return IsRead() && effects_.count() == 1; }