This is xnu-8019. See this file in:
/*
 * Copyright (c) 2015 Apple 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@
 */

#import "KCDBasicTypeDescription.h"

const char * name_for_subtype(uint8_t elem_type);

const char * name_for_subtype(uint8_t elem_type)
{
    char * retval = "unknown";
    
    switch (elem_type) {
        case KC_ST_CHAR: retval = "char"; break;
        case KC_ST_INT8: retval = "int8_t"; break;
        case KC_ST_UINT8: retval = "uint8_t"; break;
        case KC_ST_INT16: retval = "int16_t"; break;
        case KC_ST_UINT16: retval = "uint16_t"; break;
        case KC_ST_INT32: retval = "int32_t"; break;
        case KC_ST_UINT32: retval = "uint32_t"; break;
        case KC_ST_INT64: retval = "int64_t"; break;
        case KC_ST_UINT64: retval = "uint64_t"; break;
            
        default: retval = "Unknown"; break;
    }
    
    return retval;
}


@interface
KCDBasicTypeDescription () {
	unsigned int _typeID;
	uint32_t _size;
	uint32_t _count;
	NSString * _name;
	struct kcdata_subtype_descriptor _subtype_desc;
}

@end

@implementation KCDBasicTypeDescription

- (id)initWithKCTypeDesc:(kcdata_subtype_descriptor_t)sub_type_desc
{
	_typeID = sub_type_desc->kcs_elem_type;
	_count = kcs_get_elem_count(sub_type_desc);
	_size = kcs_get_elem_size(sub_type_desc);

	memcpy(&_subtype_desc, sub_type_desc, sizeof(_subtype_desc));
	_name = [NSString stringWithFormat:@"%s", _subtype_desc.kcs_name];

	return self;
}

- (id)createDefaultForType:(uint32_t)typeID
{
	struct kcdata_subtype_descriptor subtype;
	subtype.kcs_flags = KCS_SUBTYPE_FLAGS_ARRAY;
	subtype.kcs_elem_type = KC_ST_UINT8;
	subtype.kcs_elem_offset = 0;
	subtype.kcs_elem_size = KCS_SUBTYPE_PACK_SIZE(UINT16_MAX, (uint16_t)sizeof(uint8_t));
	subtype.kcs_name[0] = '\0';
	(void)[self initWithKCTypeDesc:&subtype];
	_name = [NSString stringWithFormat:@"Type_0x%x", typeID];
	return self;
}

#define read_unaligned(type, data) ({ \
    type x; \
    memcpy((void*)&x, (void*)(data), sizeof(type)); \
    x; })

- (NSObject *)objectForType:(kctype_subtype_t)elem_type withData:(uint8_t *)data
{
	NSObject * obj;

	switch (elem_type) {
	case KC_ST_CHAR: obj = [NSString stringWithFormat:@"%c", *(char *)data]; break;
	case KC_ST_INT8: obj =   [NSNumber numberWithInt:read_unaligned(int8_t, data)]; break;
	case KC_ST_UINT8: obj =  [NSNumber numberWithInt:read_unaligned(uint8_t, data)]; break;
	case KC_ST_INT16: obj =  [NSNumber numberWithShort:read_unaligned(int16_t, data)]; break;
	case KC_ST_UINT16: obj = [NSNumber numberWithUnsignedShort:read_unaligned(uint16_t, data)]; break;
	case KC_ST_INT32: obj =  [NSNumber numberWithInt:read_unaligned(int32_t, data)]; break;
	case KC_ST_UINT32: obj = [NSNumber numberWithUnsignedInt:read_unaligned(uint32_t, data)]; break;
	case KC_ST_INT64: obj =  [NSNumber numberWithLongLong:read_unaligned(int64_t, data)]; break;
	case KC_ST_UINT64: obj = [NSNumber numberWithUnsignedLongLong:read_unaligned(uint64_t, data)]; break;

	default: obj = @"<Unknown error occurred>"; break;
	}

	return obj;
}

- (NSDictionary *)parseData:(void *)dataBuffer ofLength:(uint32_t)length
{
	NSMutableDictionary * retval = [[NSMutableDictionary alloc] init];
	if (length <= _subtype_desc.kcs_elem_offset)
		return retval;
	uint8_t * data = (uint8_t *)dataBuffer;
	/*
	 * Calculate the maximum number of data elements we can parse, Taking into
	 * account the maximum size specified by the type description, and also the
	 * actual length of the data buffer and the offset into the buffer where we
	 * begin parsing.
	 */
	uint32_t elem_count = MIN(_count, (length - _subtype_desc.kcs_elem_offset) / (_size / _count));
	uint32_t elem_size = _size / _count;
	if (elem_count == 0) {
		return retval;
	}  else if (elem_count == 1) {
		retval[_name] = [self objectForType:_subtype_desc.kcs_elem_type withData:&data[_subtype_desc.kcs_elem_offset]];
	} else if (_subtype_desc.kcs_elem_type == KC_ST_CHAR) {
		char *s = (char *)&data[_subtype_desc.kcs_elem_offset];
		if (!(strnlen(s, length) < length)) {
			return nil;
		}
		retval[_name] = [NSString stringWithFormat:@"%s", s];
	} else {
		NSMutableArray * objArray = [NSMutableArray arrayWithCapacity:elem_count];
		for (unsigned int i = 0; i < elem_count; i++) {
			[objArray addObject:[self objectForType:_subtype_desc.kcs_elem_type
			                                  withData:&data[(_subtype_desc.kcs_elem_offset + (elem_size * i))]]];
		}
		retval[_name] = objArray;
	}
	return retval;
}

- (NSString *)description
{
    if (_subtype_desc.kcs_flags & KCS_SUBTYPE_FLAGS_ARRAY) {
        return  [NSString stringWithFormat:@"[%d,%d] %s  %s[%d];", _subtype_desc.kcs_elem_offset, kcs_get_elem_size(&_subtype_desc), name_for_subtype(_subtype_desc.kcs_elem_type), _subtype_desc.kcs_name, kcs_get_elem_count(&_subtype_desc) ];
    }else {
        return [NSString stringWithFormat:@"[%d,%d] %s  %s;", _subtype_desc.kcs_elem_offset, kcs_get_elem_size(&_subtype_desc), name_for_subtype(_subtype_desc.kcs_elem_type), _subtype_desc.kcs_name ];
    }
	//return [NSString stringWithFormat:@"type: %d => \"%@\" ", [self typeID], [self name]];
}

- (NSString *)name
{
	return _name;
}

- (uint32_t)count
{
	return _count;
}

- (unsigned int)typeID
{
	return _typeID;
}

- (BOOL) shouldMergeData
{
	return TRUE;
}

@end