mmap on ios

test_mmap_ios.m

// It's tested on ios 8.2 ..

// Apple document about virtual memory: 
//    Both OS X and iOS include a fully-integrated virtual memory system that you cannot turn off; it is always on. 
//    https://developer.apple.com/library/mac/documentation/Performance/Conceptual/ManagingMemory/Articles/AboutMemory.html
// Discussing mmap on ios:
//    http://stackoverflow.com/questions/13425558/why-does-mmap-fail-on-ios
//    http://stackoverflow.com/questions/9184773/is-there-a-practical-limit-on-the-number-of-memory-mapped-files-in-ios

#include <sys/mman.h>
void test_mmap_ios(NSURL* url) {
    
    FILE *fd = fopen([[url path] UTF8String], "r");

    fseek(fd, 0, SEEK_END);
    int len = (int)ftell(fd);
    fseek( fd, 0, SEEK_SET );
    
    void *map = mmap(0, len, PROT_READ, MAP_SHARED, fileno( fd), 0);
    
    if (map == MAP_FAILED) {
        fclose(fd);
        printf( "MAP_FAILED. errno=%d", errno );
        return;

    } else {
        printf( "MAP SUCCEEDED.");
    }
    
    munmap(map, len);
    fclose(fd);

    return;
}