[Objective-C]空きメモリのサイズを取得する

#import <Foundation/Foundation.h>

@interface F8VmStatistics : NSObject

@property (nonatomic, readonly) NSInteger freeSize;
@property (nonatomic, readonly) NSInteger activeSize;
@property (nonatomic, readonly) NSInteger inactiveSize;

@end

#import "F8VmStatistics.h"
#import <mach/mach.h>
#import <mach/mach_host.h>

@implementation F8VmStatistics {
  vm_statistics_data_t data_;
  vm_size_t pagesize_;
}

#pragma mark - Public ( Readonly Properties )

- (NSInteger)freeSize {
  return data_.free_count * pagesize_;
}

- (NSInteger)activeSize {
  return data_.free_count * pagesize_;
}

- (NSInteger)inactiveSize {
  return data_.inactive_count * pagesize_;
}

#pragma mark - Public ( Override NSObject )

- (id)init {
  self = [super init];
  if ( self ) {
    mach_port_t host_port = mach_host_self();
    mach_msg_type_number_t host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);

    host_page_size(host_port, &pagesize_);

    if (host_statistics(host_port,
                        HOST_VM_INFO,
                        (host_info_t)&data_,
                        &host_size)
        != KERN_SUCCESS) {
      NSLog(@"Failed to fetch vm statistics");
    }
  }
  return self;
}

@end