Question

Is there a function or constant defining the amount of available memory for an app in iPhone OS?

I’m looking for a device-independent way (iPod touch, iPhone, iPad) to know how much memory the app has left.

Answer 1

This function will return the available memory in bytes:

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

natural_t  freeMemory(void) {
    mach_port_t           host_port = mach_host_self();
    mach_msg_type_number_t   host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    vm_size_t               pagesize;
    vm_statistics_data_t     vm_stat;

    host_page_size(host_port, &pagesize);

    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) NSLog(@"Failed to fetch vm statistics");

    natural_t   mem_used = (vm_stat.active_count + vm_stat.inactive_count + vm_stat.wire_count) * pagesize;
    natural_t   mem_free = vm_stat.free_count * pagesize;
    natural_t   mem_total = mem_used + mem_free;

    return mem_free;
}