Converting unsigned chars to signed integer

Question

I have an unsigned char array with 2 elements that represents a signed integer. How can I convert these 2 bytes into a signed integer?

Edit: The unsigne

Answer 1

For maximum safety, use

int i = *(signed char *)(&c[0]);
i *= 1 << CHAR_BIT;
i |= c[1];

for big endian. Swap c[0] and c[1] for little endian.

(Explanation: we interpret the byte at c[0] as a signed char, then arithmetically left shift it in a portable way, then add in c[1].)