Unsafe pointer/array notation in C#

Question

Suppose I have:

unsafe {
    byte* start = GetStartLocation();
    int something = start[4];
}

What is something? The value of the memory address 4 bytes down from start?

RichieHindle · Accepted Answer · 2009-06-22 22:21:56Z

6

Say start points to memory location 0x12345678, and memory looks like this:

  0x12345678   0x12
  0x12345679   0x34
  0x1234567a   0x56
  0x1234567b   0x78
  0x1234567c   0x9a
  0x1234567d   0xbc

then something equals 0x9a.

The fact that something has type int doesn't matter to how start[4] is interpreted - it gets the byte value of the byte 4 locations away from start.

edited Jun 22, 2009 at 22:21

answered Jun 22, 2009 at 22:16

RichieHindle

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2 Comments

xofz Over a year ago

Thank you! I need to enter 15 characters to post this, which leads me to believe that 'thank you's in general are not allowed, which means this will be deleted shortly, so I hope you see this! Thanks!

RichieHindle Over a year ago

@Sam: Personally, I think the more "thank you"s on SO the better. Feel free to pad them with smileys as necessary. 8-)

JaredPar · Accepted Answer · 2009-06-22 22:14:10Z

2

The value of something is the byte value of offset 4 from start widened to an int type.

It's equivalent to the following code

byte temp = start[4];
int something = temp;

answered Jun 22, 2009 at 22:14

JaredPar

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Comments

i_am_jorf · Accepted Answer · 2009-06-22 22:15:03Z

2

start[4] will evaluate to:

*(start + 4)

answered Jun 22, 2009 at 22:15

i_am_jorf

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