uhhhCmain.c Notes $($C version: see Cmain.c$)-$ PA$7$

This is a relatively short function. Follow the instructions in the starter code. main$()$ calls setup$()$ to parse the command line arguments, open the bookfile and set the func$()$ pointer to point at either ecrypt$()$ or dcrypt$().$ Be aware that when calling setup$()$ there are two output parameters $($you are passing addresses of main$()$ stack variables$)$ to the function setup$()$ to change.

CSE $30$ PA$7-8$

$\frac{10}{15}$

setup$()$ returns RETRN$\_$FAIL if there is an error. Important: If setup$()$ fails, then both output variables, fpbook and func, are set to contain NULL. So you do not fclose$($fpbook$).$

main$()$ I$/$O loop consists of the following three steps:

call rdbuf$()$ to fill the inbuf $($from stdin$)$ and bookbuf $($from bookfp$)$ with the same number of characters. If $0$ is returned EOF was reached on stdin.

Call the function pointed at by func$()$ to encrypt or decrypt inbuf.

Call fwrite$()$ to write inbuf to stdout. You should cast the return value of fwrite to an int to suppress compiler warnings $($int$)$fwrite$()$ and the I$/$O sizes are small.

Make sure to always fclose$($fdbook$)$ regardless of what rdbuf$()$ returns and then return either EXIT$\_$SUCCESS $($if all ok$)$ or EXIT$\_$FAILURE otherwise.