The iOS _MALLOC(size_t size, int type, int flags) function allocates size bytes on the heap. Internally blocks are represented as a length field followed by a data field:

struct _mhead {
size_t mlen;
char dat[0]; }

The mlen field is used by the free() function to determine how much space needs to be freed. In iOS 4.x the _MALLOC function was implemented as follows:

1 void * _MALLOC(size_t size, int type, int flags) {
2 struct _mhead *hdr;
3 size_t memsize = sizeof (*hdr) + size;
4 hdr = (void *)kalloc(memsize); // allocate memory
5 hdr->mlen = memsize;
6 return (hdr->dat);
7 }

In iOS 5.x the following two lines were added after line 3:

int o = memsize < size ? 1 : 0;
if (o) return (NULL);

Why were these lines added in iOS5.x? Briefly describe an attack that may be possible without these lines.

Write a computer program to calculate the three-phase fault current for a fault at f in figure 1.16, with the network normal, and with one line at a time removedproblems 1.1 write a computer program to calculate the three-phase fault current for a fault at f in figure 1.16, with the network normal, and with one line at a time removed 20 power system relaying from service. the positive-sequence impedance data are given in the accompanying table. use the commonly made assumption that all prefault resistance values are (1.0+j0.0) pu, and neglect all resistance values. calculate the contribution to the fault flowing through the cb b and the voltage at that bus. for each calculated case, consider the two possibilities: cb b2 closed or open. the latter is known as the stub-end fault í• figure 1.16 problem 1.1 system data for figure 1.16 from to positive sequence 0.0+j0.1 0.05j0.15 0.04 j0.2 0.01 jo.i 0.015 + j0.15 0.01 j0.19 0.01 +j0.19 0.03+j0.1 0.0+j0.08 6 6 6 from service. the positive-sequence impedance data are given in the accompanying table. use the commonly made assumption that all prefault resistance values are (1.0 + j 0.0) pu, and neglect all resistance values. calculate the contribution to the fault flowing through the cb b1, and the voltage at that bus. for each calculated case, consider the two possibilities: cb b2 closed or open. the latter is known as the “stub-end” fault.

Designing a mobile web page is a little different from designing a regular web page. name at least three features that should be considered when designing a website that is mobile phone-friendly, and briefly explain why they are important.

In the lab, which of the following displayed a list of all installed services and included a description of the service, the current state, and whether the service started automatically or manually? a. the services manager b. the applications summary c. the recommended services d. list the safe services list