/*
 * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

#define _IOMEMORYDESCRIPTOR_INTERNAL_

#include <IOKit/assert.h>
#include <IOKit/system.h>

#include <IOKit/IOLib.h>
#include <IOKit/IOMapper.h>
#include <IOKit/IOBufferMemoryDescriptor.h>
#include <libkern/OSDebug.h>
#include <mach/mach_vm.h>

#include "IOKitKernelInternal.h"

#ifdef IOALLOCDEBUG
#include <libkern/c++/OSCPPDebug.h>
#endif
#include <IOKit/IOStatisticsPrivate.h>

#if IOKITSTATS
#define IOStatisticsAlloc(type, size) \
do { \
	IOStatistics::countAlloc(type, size); \
} while (0)
#else
#define IOStatisticsAlloc(type, size)
#endif /* IOKITSTATS */


__BEGIN_DECLS
void ipc_port_release_send(ipc_port_t port);
#include <vm/pmap.h>

__END_DECLS

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

enum
{
    kInternalFlagPhysical      = 0x00000001,
    kInternalFlagPageSized     = 0x00000002,
    kInternalFlagPageAllocated = 0x00000004
};

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#if 0
#undef assert
#define assert(ex)  \
	((ex) ? (void)0 : Assert(__FILE__, __LINE__, # ex))
#endif

enum
{
    kIOPageAllocChunkBytes = (PAGE_SIZE / 64),
    kIOPageAllocSignature  = 'iopa'
};

struct io_pagealloc_t
{
    queue_chain_t link;
    uint64_t      avail;
    uint32_t      signature;
};
typedef struct io_pagealloc_t io_pagealloc_t;

typedef char io_pagealloc_t_assert[(sizeof(io_pagealloc_t) <= kIOPageAllocChunkBytes) ? 1 : -1];

IOSimpleLock * gIOPageAllocLock;
queue_head_t   gIOPageAllocList;
vm_size_t      gIOPageAllocCount;
vm_size_t      gIOPageAllocBytes;

static io_pagealloc_t * 
iopa_allocpage(void)
{
    kern_return_t    kr;
    io_pagealloc_t * pa;
    vm_address_t     vmaddr = 0;

    int options = 0; // KMA_LOMEM;
    kr = kernel_memory_allocate(kernel_map, &vmaddr,
				page_size, 0, options);
    if (KERN_SUCCESS != kr) return (0);

    bzero((void *) vmaddr, page_size);
    pa = (typeof(pa)) (vmaddr + page_size - kIOPageAllocChunkBytes);

    pa->signature = kIOPageAllocSignature;
    pa->avail     = -2ULL;

    return (pa);
}

static void 
iopa_freepage(io_pagealloc_t * pa)
{
    kmem_free( kernel_map, trunc_page((uintptr_t) pa), page_size);
}

static uintptr_t
iopa_allocinpage(io_pagealloc_t * pa, uint32_t count, uint64_t align)
{
    uint32_t n, s;
    uint64_t avail = pa->avail;

    assert(avail);

    // find strings of count 1 bits in avail
    for (n = count; n > 1; n -= s)
    {
    	s = n >> 1;
    	avail = avail & (avail << s);
    }
    // and aligned
    avail &= align;

    if (avail)
    {
	n = __builtin_clzll(avail);
	pa->avail &= ~((-1ULL << (64 - count)) >> n);
	if (!pa->avail && pa->link.next)
	{
	    remque(&pa->link);
	    pa->link.next = 0;
	}
	return (n * kIOPageAllocChunkBytes + trunc_page((uintptr_t) pa));
    }

    return (0);
}

static uint32_t 
log2up(uint32_t size)
{
    if (size <= 1) size = 0;
    else size = 32 - __builtin_clz(size - 1);
    return (size);
}

static uintptr_t 
iopa_alloc(vm_size_t bytes, uint32_t balign)
{
    static const uint64_t align_masks[] = {
	0xFFFFFFFFFFFFFFFF,
	0xAAAAAAAAAAAAAAAA,
	0x8888888888888888,
	0x8080808080808080,
	0x8000800080008000,
	0x8000000080000000,
	0x8000000000000000,
    };
    io_pagealloc_t * pa;
    uintptr_t        addr = 0;
    uint32_t         count;
    uint64_t         align;

    if (!bytes) bytes = 1;
    count = (bytes + kIOPageAllocChunkBytes - 1) / kIOPageAllocChunkBytes;
    align = align_masks[log2up((balign + kIOPageAllocChunkBytes - 1) / kIOPageAllocChunkBytes)];

    IOSimpleLockLock(gIOPageAllocLock);
    pa = (typeof(pa)) queue_first(&gIOPageAllocList);
    while (!queue_end(&gIOPageAllocList, &pa->link))
    {
	addr = iopa_allocinpage(pa, count, align);
	if (addr)
	{
	    gIOPageAllocBytes += bytes;
	    break;
	}
	pa = (typeof(pa)) queue_next(&pa->link);
    }
    IOSimpleLockUnlock(gIOPageAllocLock);
    if (!addr)
    {
        pa = iopa_allocpage();
	if (pa)
	{
	    addr = iopa_allocinpage(pa, count, align);
	    IOSimpleLockLock(gIOPageAllocLock);
	    if (pa->avail) enqueue_head(&gIOPageAllocList, &pa->link);
	    gIOPageAllocCount++;
	    if (addr) gIOPageAllocBytes += bytes;
	    IOSimpleLockUnlock(gIOPageAllocLock);
	}
    }

    if (addr)
    {
        assert((addr & ((1 << log2up(balign)) - 1)) == 0);
    	IOStatisticsAlloc(kIOStatisticsMallocAligned, bytes);
#if IOALLOCDEBUG
	debug_iomalloc_size += bytes;
#endif
    }

    return (addr);
}

static void 
iopa_free(uintptr_t addr, vm_size_t bytes)
{
    io_pagealloc_t * pa;
    uint32_t         count;
    uintptr_t        chunk;

    if (!bytes) bytes = 1;

    chunk = (addr & page_mask);
    assert(0 == (chunk & (kIOPageAllocChunkBytes - 1)));

    pa = (typeof(pa)) (addr | (page_size - kIOPageAllocChunkBytes));
    assert(kIOPageAllocSignature == pa->signature);

    count = (bytes + kIOPageAllocChunkBytes - 1) / kIOPageAllocChunkBytes;
    chunk /= kIOPageAllocChunkBytes;

    IOSimpleLockLock(gIOPageAllocLock);
    if (!pa->avail)
    {
	assert(!pa->link.next);
	enqueue_tail(&gIOPageAllocList, &pa->link);
    }
    pa->avail |= ((-1ULL << (64 - count)) >> chunk);
    if (pa->avail != -2ULL) pa = 0;
    else
    {
        remque(&pa->link);
        pa->link.next = 0;
        pa->signature = 0;
	gIOPageAllocCount--;
    }
    gIOPageAllocBytes -= bytes;
    IOSimpleLockUnlock(gIOPageAllocLock);
    if (pa) iopa_freepage(pa);

#if IOALLOCDEBUG
    debug_iomalloc_size -= bytes;
#endif
    IOStatisticsAlloc(kIOStatisticsFreeAligned, bytes);
}

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#define super IOGeneralMemoryDescriptor
OSDefineMetaClassAndStructors(IOBufferMemoryDescriptor,
				IOGeneralMemoryDescriptor);

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef __LP64__
bool IOBufferMemoryDescriptor::initWithOptions(
                               IOOptionBits options,
                               vm_size_t    capacity,
                               vm_offset_t  alignment,
			       task_t	    inTask)
{
    mach_vm_address_t physicalMask = 0;
    return (initWithPhysicalMask(inTask, options, capacity, alignment, physicalMask));
}
#endif /* !__LP64__ */

bool IOBufferMemoryDescriptor::initWithPhysicalMask(
				task_t		  inTask,
				IOOptionBits      options,
				mach_vm_size_t    capacity,
				mach_vm_address_t alignment,
				mach_vm_address_t physicalMask)
{
    kern_return_t 	  kr;
    task_t		  mapTask = NULL;
    vm_map_t 		  vmmap = NULL;
    mach_vm_address_t     highestMask = 0;
    IOOptionBits	  iomdOptions = kIOMemoryTypeVirtual64 | kIOMemoryAsReference;
    IODMAMapSpecification mapSpec;
    bool                  mapped = false;
    bool                  needZero;

    if (!capacity)
        return false;

    _options   	      = options;
    _capacity         = capacity;
    _internalFlags    = 0;
    _internalReserved = 0;
    _buffer	      = 0;

    _ranges.v64 = IONew(IOAddressRange, 1);
    if (!_ranges.v64)
	return (false);
    _ranges.v64->address = 0;
    _ranges.v64->length  = 0;
    //  make sure super::free doesn't dealloc _ranges before super::init
    _flags = kIOMemoryAsReference;

    // Grab IOMD bits from the Buffer MD options
    iomdOptions  |= (options & kIOBufferDescriptorMemoryFlags);

    if (!(kIOMemoryMapperNone & options))
    {
	IOMapper::checkForSystemMapper();
	mapped = (0 != IOMapper::gSystem);
    }
    needZero = mapped;

    if (physicalMask && (alignment <= 1))
    {
	alignment   = ((physicalMask ^ (-1ULL)) & (physicalMask - 1));
	highestMask = (physicalMask | alignment);
	alignment++;
	if (alignment < page_size)
            alignment = page_size;
    }

    if ((options & (kIOMemorySharingTypeMask | kIOMapCacheMask | kIOMemoryClearEncrypt)) && (alignment < page_size))
	alignment = page_size;

    if (alignment >= page_size)
	capacity = round_page(capacity);

    if (alignment > page_size)
	options |= kIOMemoryPhysicallyContiguous;

    _alignment = alignment;

    if ((inTask != kernel_task) && !(options & kIOMemoryPageable))
	return false;

    bzero(&mapSpec, sizeof(mapSpec));
    mapSpec.alignment      = _alignment;
    mapSpec.numAddressBits = 64;
    if (highestMask && mapped)
    {
	if (highestMask <= 0xFFFFFFFF)
	    mapSpec.numAddressBits = (32 - __builtin_clz((unsigned int) highestMask));
	else
	    mapSpec.numAddressBits = (64 - __builtin_clz((unsigned int) (highestMask >> 32)));
	highestMask = 0;
    }

    // set flags for entry + object create
    vm_prot_t memEntryCacheMode = VM_PROT_READ | VM_PROT_WRITE;

    // set memory entry cache mode
    switch (options & kIOMapCacheMask)
    {
	case kIOMapInhibitCache:
	    SET_MAP_MEM(MAP_MEM_IO, memEntryCacheMode);
	    break;

	case kIOMapWriteThruCache:
	    SET_MAP_MEM(MAP_MEM_WTHRU, memEntryCacheMode);
	    break;

	case kIOMapWriteCombineCache:
	    SET_MAP_MEM(MAP_MEM_WCOMB, memEntryCacheMode);
	    break;

	case kIOMapCopybackCache:
	    SET_MAP_MEM(MAP_MEM_COPYBACK, memEntryCacheMode);
	    break;

	case kIOMapCopybackInnerCache:
	    SET_MAP_MEM(MAP_MEM_INNERWBACK, memEntryCacheMode);
	    break;

	case kIOMapDefaultCache:
	default:
	    SET_MAP_MEM(MAP_MEM_NOOP, memEntryCacheMode);
	    break;
    }

    if (options & kIOMemoryPageable)
    {
	iomdOptions |= kIOMemoryBufferPageable;

	// must create the entry before any pages are allocated

	// set flags for entry + object create
	memEntryCacheMode |= MAP_MEM_NAMED_CREATE;

	if (options & kIOMemoryPurgeable)
	    memEntryCacheMode |= MAP_MEM_PURGABLE;
    }
    else
    {
	memEntryCacheMode |= MAP_MEM_NAMED_REUSE;
	vmmap = kernel_map;

	// Buffer shouldn't auto prepare they should be prepared explicitly
	// But it never was enforced so what are you going to do?
	iomdOptions |= kIOMemoryAutoPrepare;

	/* Allocate a wired-down buffer inside kernel space. */

	bool contig = (0 != (options & kIOMemoryHostPhysicallyContiguous));

	if (!contig && (0 != (options & kIOMemoryPhysicallyContiguous)))
	{
	    contig |= (!mapped);
	    contig |= (0 != (kIOMemoryMapperNone & options));
#if 0
	    // treat kIOMemoryPhysicallyContiguous as kIOMemoryHostPhysicallyContiguous for now
	    contig |= true;
#endif
	}

	if (contig || highestMask || (alignment > page_size))
	{
            _internalFlags |= kInternalFlagPhysical;
            if (highestMask)
            {
                _internalFlags |= kInternalFlagPageSized;
                capacity = round_page(capacity);
            }
            _buffer = (void *) IOKernelAllocateWithPhysicalRestrict(
            				capacity, highestMask, alignment, contig);
	}
	else if (needZero
		  && ((capacity + alignment) <= (page_size - kIOPageAllocChunkBytes)))
	{
            _internalFlags |= kInternalFlagPageAllocated;
            needZero        = false;
            _buffer         = (void *) iopa_alloc(capacity, alignment);
	}
	else if (alignment > 1)
	{
            _buffer = IOMallocAligned(capacity, alignment);
	}
	else
	{
            _buffer = IOMalloc(capacity);
	}
	if (!_buffer)
	{
            return false;
	}
	if (needZero) bzero(_buffer, capacity);
    }

    if( (options & (kIOMemoryPageable | kIOMapCacheMask))) {
	ipc_port_t	sharedMem;
	vm_size_t	size = round_page(capacity);

	kr = mach_make_memory_entry(vmmap,
				    &size, (vm_offset_t)_buffer,
				    memEntryCacheMode, &sharedMem,
				    NULL );

	if( (KERN_SUCCESS == kr) && (size != round_page(capacity))) {
	    ipc_port_release_send( sharedMem );
	    kr = kIOReturnVMError;
	}
	if( KERN_SUCCESS != kr)
	    return( false );

	_memEntry = (void *) sharedMem;

	if( options & kIOMemoryPageable) {
#if IOALLOCDEBUG
	    debug_iomallocpageable_size += size;
#endif
	    mapTask = inTask;
	    if (NULL == inTask)
		inTask = kernel_task;
	}
	else if (options & kIOMapCacheMask)
	{
	    // Prefetch each page to put entries into the pmap
	    volatile UInt8 *	startAddr = (UInt8 *)_buffer;
	    volatile UInt8 *	endAddr   = (UInt8 *)_buffer + capacity;

	    while (startAddr < endAddr)
	    {
		*startAddr;
		startAddr += page_size;
 	    }
	}
    }

    _ranges.v64->address = (mach_vm_address_t) _buffer;;
    _ranges.v64->length  = _capacity;

    if (!super::initWithOptions(_ranges.v64, 1, 0,
				inTask, iomdOptions, /* System mapper */ 0))
	return false;

    // give any system mapper the allocation params
    if (kIOReturnSuccess != dmaCommandOperation(kIOMDAddDMAMapSpec, 
    						&mapSpec, sizeof(mapSpec)))
	return false;

    if (mapTask)
    {
	if (!reserved) {
	    reserved = IONew( ExpansionData, 1 );
	    if( !reserved)
		return( false );
	}
	reserved->map = createMappingInTask(mapTask, 0, 
			    kIOMapAnywhere | (options & kIOMapCacheMask), 0, 0);
	if (!reserved->map)
	{
	    _buffer = 0;
	    return( false );
	}
	release();	    // map took a retain on this
	reserved->map->retain();
	removeMapping(reserved->map);
	mach_vm_address_t buffer = reserved->map->getAddress();
	_buffer = (void *) buffer;
	if (kIOMemoryTypeVirtual64 == (kIOMemoryTypeMask & iomdOptions))
	    _ranges.v64->address = buffer;
    }

    setLength(_capacity);

    return true;
}

IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::inTaskWithOptions(
					    task_t       inTask,
                                            IOOptionBits options,
                                            vm_size_t    capacity,
                                            vm_offset_t  alignment)
{
    IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
    
    if (me && !me->initWithPhysicalMask(inTask, options, capacity, alignment, 0)) {
	me->release();
	me = 0;
    }
    return me;
}

IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::inTaskWithPhysicalMask(
					    task_t	      inTask,
                                            IOOptionBits      options,
                                            mach_vm_size_t    capacity,
                                            mach_vm_address_t physicalMask)
{
    IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
    
    if (me && !me->initWithPhysicalMask(inTask, options, capacity, 1, physicalMask))
    {
	me->release();
	me = 0;
    }
    return me;
}

#ifndef __LP64__
bool IOBufferMemoryDescriptor::initWithOptions(
                               IOOptionBits options,
                               vm_size_t    capacity,
                               vm_offset_t  alignment)
{
    return (initWithPhysicalMask(kernel_task, options, capacity, alignment, (mach_vm_address_t)0));
}
#endif /* !__LP64__ */

IOBufferMemoryDescriptor * IOBufferMemoryDescriptor::withOptions(
                                            IOOptionBits options,
                                            vm_size_t    capacity,
                                            vm_offset_t  alignment)
{
    IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
    
    if (me && !me->initWithPhysicalMask(kernel_task, options, capacity, alignment, 0)) {
	me->release();
	me = 0;
    }
    return me;
}


/*
 * withCapacity:
 *
 * Returns a new IOBufferMemoryDescriptor with a buffer large enough to
 * hold capacity bytes.  The descriptor's length is initially set to the capacity.
 */
IOBufferMemoryDescriptor *
IOBufferMemoryDescriptor::withCapacity(vm_size_t   inCapacity,
                                       IODirection inDirection,
                                       bool        inContiguous)
{
    return( IOBufferMemoryDescriptor::withOptions(
               inDirection | kIOMemoryUnshared
                | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
               inCapacity, inContiguous ? inCapacity : 1 ));
}

#ifndef __LP64__
/*
 * initWithBytes:
 *
 * Initialize a new IOBufferMemoryDescriptor preloaded with bytes (copied).
 * The descriptor's length and capacity are set to the input buffer's size.
 */
bool IOBufferMemoryDescriptor::initWithBytes(const void * inBytes,
                                             vm_size_t    inLength,
                                             IODirection  inDirection,
                                             bool         inContiguous)
{
    if (!initWithPhysicalMask(kernel_task, inDirection | kIOMemoryUnshared
			      | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
			      inLength, inLength, (mach_vm_address_t)0))
        return false;

    // start out with no data
    setLength(0);

    if (!appendBytes(inBytes, inLength))
        return false;

    return true;
}
#endif /* !__LP64__ */

/*
 * withBytes:
 *
 * Returns a new IOBufferMemoryDescriptor preloaded with bytes (copied).
 * The descriptor's length and capacity are set to the input buffer's size.
 */
IOBufferMemoryDescriptor *
IOBufferMemoryDescriptor::withBytes(const void * inBytes,
                                    vm_size_t    inLength,
                                    IODirection  inDirection,
                                    bool         inContiguous)
{
    IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;

    if (me && !me->initWithPhysicalMask(
               kernel_task, inDirection | kIOMemoryUnshared
                | (inContiguous ? kIOMemoryPhysicallyContiguous : 0),
               inLength, inLength, 0 ))
    {
	me->release();
	me = 0;
    }

    if (me)
    {
	// start out with no data
	me->setLength(0);

	if (!me->appendBytes(inBytes, inLength))
	{
	    me->release();
	    me = 0;
	}
    }
    return me;
}

/*
 * free:
 *
 * Free resources
 */
void IOBufferMemoryDescriptor::free()
{
    // Cache all of the relevant information on the stack for use
    // after we call super::free()!
    IOOptionBits     flags         = _flags;
    IOOptionBits     internalFlags = _internalFlags;
    IOOptionBits     options   = _options;
    vm_size_t        size      = _capacity;
    void *           buffer    = _buffer;
    IOMemoryMap *    map       = 0;
    IOAddressRange * range     = _ranges.v64;
    vm_offset_t      alignment = _alignment;

    if (alignment >= page_size)
	size = round_page(size);

    if (reserved)
    {
	map = reserved->map;
        IODelete( reserved, ExpansionData, 1 );
	if (map)
	    map->release();
    }

    /* super::free may unwire - deallocate buffer afterwards */
    super::free();

    if (options & kIOMemoryPageable)
    {
#if IOALLOCDEBUG
	debug_iomallocpageable_size -= round_page(size);
#endif
    }
    else if (buffer)
    {
	if (kInternalFlagPageSized & internalFlags) size = round_page(size);

        if (kInternalFlagPhysical & internalFlags)
        {
            IOKernelFreePhysical((mach_vm_address_t) buffer, size);
	}
	else if (kInternalFlagPageAllocated & internalFlags)
	{
            iopa_free((uintptr_t) buffer, size);
	}
        else if (alignment > 1)
	{
            IOFreeAligned(buffer, size);
	}
        else
	{
            IOFree(buffer, size);
	}
    }
    if (range && (kIOMemoryAsReference & flags))
	IODelete(range, IOAddressRange, 1);
}

/*
 * getCapacity:
 *
 * Get the buffer capacity
 */
vm_size_t IOBufferMemoryDescriptor::getCapacity() const
{
    return _capacity;
}

/*
 * setLength:
 *
 * Change the buffer length of the memory descriptor.  When a new buffer
 * is created, the initial length of the buffer is set to be the same as
 * the capacity.  The length can be adjusted via setLength for a shorter
 * transfer (there is no need to create more buffer descriptors when you
 * can reuse an existing one, even for different transfer sizes).   Note
 * that the specified length must not exceed the capacity of the buffer.
 */
void IOBufferMemoryDescriptor::setLength(vm_size_t length)
{
    assert(length <= _capacity);

    _length = length;
    _ranges.v64->length = length;
}

/*
 * setDirection:
 *
 * Change the direction of the transfer.  This method allows one to redirect
 * the descriptor's transfer direction.  This eliminates the need to destroy
 * and create new buffers when different transfer directions are needed.
 */
void IOBufferMemoryDescriptor::setDirection(IODirection direction)
{
    _flags = (_flags & ~kIOMemoryDirectionMask) | direction;
#ifndef __LP64__
    _direction = (IODirection) (_flags & kIOMemoryDirectionMask);
#endif /* !__LP64__ */
}

/*
 * appendBytes:
 *
 * Add some data to the end of the buffer.  This method automatically
 * maintains the memory descriptor buffer length.  Note that appendBytes
 * will not copy past the end of the memory descriptor's current capacity.
 */
bool
IOBufferMemoryDescriptor::appendBytes(const void * bytes, vm_size_t withLength)
{
    vm_size_t   actualBytesToCopy = min(withLength, _capacity - _length);
    IOByteCount offset;

    assert(_length <= _capacity);

    offset = _length;
    _length += actualBytesToCopy;
    _ranges.v64->length += actualBytesToCopy;

    if (_task == kernel_task)
	bcopy(/* from */ bytes, (void *)(_ranges.v64->address + offset),
	      actualBytesToCopy);
    else
	writeBytes(offset, bytes, actualBytesToCopy);

    return true;
}

/*
 * getBytesNoCopy:
 *
 * Return the virtual address of the beginning of the buffer
 */
void * IOBufferMemoryDescriptor::getBytesNoCopy()
{
    if (kIOMemoryTypePhysical64 == (_flags & kIOMemoryTypeMask))
	return _buffer;
    else
	return (void *)_ranges.v64->address;
}


/*
 * getBytesNoCopy:
 *
 * Return the virtual address of an offset from the beginning of the buffer
 */
void *
IOBufferMemoryDescriptor::getBytesNoCopy(vm_size_t start, vm_size_t withLength)
{
    IOVirtualAddress address;
    if (kIOMemoryTypePhysical64 == (_flags & kIOMemoryTypeMask))
	address = (IOVirtualAddress) _buffer;
    else
	address = _ranges.v64->address;

   if (start < _length && (start + withLength) <= _length)
        return (void *)(address + start);
    return 0;
}

#ifndef __LP64__
void * IOBufferMemoryDescriptor::getVirtualSegment(IOByteCount offset,
							IOByteCount * lengthOfSegment)
{
    void * bytes = getBytesNoCopy(offset, 0);
    
    if (bytes && lengthOfSegment)
	*lengthOfSegment = _length - offset;

    return bytes;
}
#endif /* !__LP64__ */

#ifdef __LP64__
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 0);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 1);
#else /* !__LP64__ */
OSMetaClassDefineReservedUsed(IOBufferMemoryDescriptor, 0);
OSMetaClassDefineReservedUsed(IOBufferMemoryDescriptor, 1);
#endif /* !__LP64__ */
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 2);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 3);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 4);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 5);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 6);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 7);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 8);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 9);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 10);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 11);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 12);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 13);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 14);
OSMetaClassDefineReservedUnused(IOBufferMemoryDescriptor, 15);