这批代码介绍如何使用iPhone的三轴感应器

#include <IOKit/IOKitLib.h>

#include <CoreFoundation/CoreFoundation.h>

typedef struct
{} *IOHIDEventSystemRef;

typedef struct
{} *IOHIDEventRef;

float IOHIDEventGetFloatValue(IOHIDEventRef ref,
int param);

void handleHIDEvent(int a,
int b, int c, IOHIDEventRef ptr)
{

int type = IOHIDEventGetType(ptr);

if (type
== 12)
{

float x,y,z;

x = IOHIDEventGetFloatValue(ptr, 0xc0000);

y = IOHIDEventGetFloatValue(ptr, 0xc0001);

z = IOHIDEventGetFloatValue(ptr, 0xc0002);

// do whatever you need to do with the gravity

ballSetAccel(x, y);

}

}

#define expect(x) if(!x) { printf("failed: %s\n", #x); return; }

void initialize(int hz)
{

mach_port_t master;

expect(0 == IOMasterPort(MACH_PORT_NULL,
&master));

int page = 0xff00, usage
= 3;

CFNumberRef nums[2];

CFStringRef keys[2];

keys[0]
= CFStringCreateWithCString(0,
"PrimaryUsagePage", 0);

keys[1]
= CFStringCreateWithCString(0,
"PrimaryUsage", 0);

nums[0]
= CFNumberCreate(0, kCFNumberSInt32Type,
&page);

nums[1]
= CFNumberCreate(0, kCFNumberSInt32Type,
&usage);

CFDictionaryRef dict = CFDictionaryCreate(0,
(const void**)keys,

(const void**)nums,
2, &kCFTypeDictionaryKeyCallBacks,
&kCFTypeDictionaryValueCallBacks);

expect(dict);

IOHIDEventSystemRef sys = (IOHIDEventSystemRef) IOHIDEventSystemCreate(0);

expect(sys);

CFArrayRef srvs = (CFArrayRef)IOHIDEventSystemCopyMatchingServices(sys, dict,
0, 0, 0);

expect(CFArrayGetCount(srvs)==1);

io_registry_entry_t serv = (io_registry_entry_t)CFArrayGetValueAtIndex(srvs,
0);

expect(serv);

CFStringRef cs = CFStringCreateWithCString(0,
"ReportInterval", 0);

int rv = 1000000/hz;

CFNumberRef cn = CFNumberCreate(0, kCFNumberSInt32Type,
&rv);

int res = IOHIDServiceSetProperty(serv, cs, cn);

expect(res ==
1);

res = IOHIDEventSystemOpen(sys, handleHIDEvent,
0, 0);

expect(res !=
0);

}