When coding a program to use struct of bit fields, i.e.
1) is there any way to fast initialize, i.e. to 0, or must I put each field to 0; (m=0, or, m.f1=0, m.f2=0, etc)....Code:struct m { f1:5; f2:6; f3:7; f4:1; }
2) can I compare structs in the way :
if (m==...)
or the only way to compare is field to field?
thx
1. Use typedef struct instead. They will be automatically initialized.
2. Comparing by field to field is the only way T_T...
If you give an initializer list, all not-listed objects are initialized to zero. You can't use an assignment statement like foo=0. (You could, if you needed to, make a struct m called zero (say) that had all fields zero, and then you could do foo=zero.)
You can only use == with numbers and pointers.
Typedef is irrelevant here.Originally Posted by audinue
To initialize every member of the structure to zero, you could probably use memset(), though I'm not sure how standard that would be.
[edit] Global and static variables are automatically initialized to all zeros, but don't use them just for that reason . . . . [/edit]
It would probably be best to create a function that compares those structures if you do it often.
dwk
Seek and ye shall find. quaere et invenies.
"Simplicity does not precede complexity, but follows it." -- Alan Perlis
"Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
"The only real mistake is the one from which we learn nothing." -- John Powell
Other boards: DaniWeb, TPS
Unofficial Wiki FAQ: cpwiki.sf.net
My website: http://dwks.theprogrammingsite.com/
Projects: codeform, xuni, atlantis, nort, etc.
One solution I've seen before is to do this:
When you want "all" of the data, you use the all.word (or all field if you choose alternative 2). e.g, using alt2:.Code:struct m { union { struct bits { int f1:5; int f2:6; int f3:7; int f4:1; }; // alt 1: struct all { int word:19; } // alt 2: int all; };
--Code:void somefunc() { m var; var.all = 0; ... // You will also need to use the .bits prefix to set the differnet bitfields: var.bits.f1 = 7; var.bits.f4 = 1; }
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
