Need help understanding usage of bitwise operators

I inherited some code and can't figure out one piece of it:

byte[] b = new byte[4] { 3, 2, 5, 7 };
int c = (b[0] & 0x7f) &开发者_开发百科lt;< 24 | b[1] << 16 | b[2] << 8 | b[3];

Can anyone tell what's happening here?

---

Basically it converts the lower 31 bits of a 4 byte array into an integer using a big-endian conversion.

So a byte array of { 0, 0, 0, 1 } would be converted to 1; a byte array of { 0, 0, 1, 0 } would be converted to 256 etc.

It does this through a mixture of bitwise operators:

• & is bitwise "and"
• | is bitwise "or"
• << is the left shift operator

---

haven't done bit math in a minute so..for fun:
[extra parenthesis to show order of ops]

((b[0] & 0x7f) << 24) | (b[1] << 16) | (b[2] << 8) | b[3]

(b[0] & 0x7f) << 24 =  11 0000 0000 0000 0000 0000 0000
b[1] << 16 = . . . . . . . . . . 10 0000 0000 0000 0000
b[2] << 8 = . . . . . . . . . . . . . . . 101 0000 0000
b[3] = .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 0111

now OR these together, and you get

0011 0000 0010 0000 0101 0000 0111 = 50,464,007