digitalmars.D.learn - Getting byte size of POD classes and dynamic arrays
- Byron Heads (97/97) May 16 2013 I am working on d-leveldb wrapper (https://github.com/bheads/d-leveldb)
- 1100110 (4/15) May 16 2013 he=20
- Byron Heads (7/22) May 16 2013 I missed that one, in my test it returns 29 bytes,
- bearophile (7/8) May 16 2013 In D global structs are PODs, while classe instances are are not
- Byron Heads (2/13) May 16 2013 Thanks, I will just block them since they are unsafe for a database.
- 1100110 (14/39) May 16 2013 I.
- Byron Heads (5/7) May 16 2013 Any ideas on how to get the element type of an array
- Byron Heads (4/13) May 16 2013 Found ForeachType!T this seems to do the trick. Not the most initiativ...
- bearophile (6/8) May 16 2013 It has a strange name because a string (that is a dynamic array)
- Andrej Mitrovic (2/7) May 16 2013 Try the ElementType template in std.range. There's also ElementEncodingT...
I am working on d-leveldb wrapper (https://github.com/bheads/d-leveldb) and I need to be able to pass blocks of data between D and leveldb API. I am having rouble getting the byte size of dynamic arrays and POD classes. I can get the right size for 1D dynamic arrays, need a way to compute the total size. POD Classes always give me the size of the ref, is it possible? -Byron You can see in my example code: ---------------------------- module sizeof; import std.stdio, std.traits; align(1) struct SBlock { ubyte b[13]; } align(1) class CBlock { ubyte b[13]; } size_t size(P)(in P p) { // Working so far static if(isStaticArray!P || isBasicType!P || isPODStruct!P) return P.sizeof; // works if *p is not another pointer, else static if(isPointer!P) return typeof(*p).sizeof; // works on 1D arrays else static if(isDynamicArray!P) return (p.length ? typeof(p[0]).sizeof * p.length : 0 ); // does not work, only gets size of the class ref else static if(__traits(isPOD, P) && is(P == class)) return typeid(P).tsize; else assert(0); } template isPODStruct(T) { static if(is(T == struct)) enum isPODStruct = __traits(isPOD, T); else enum isPODStruct = false; } property void Size(alias V)() { writeln(V, ": ", size(V)); } void main() { Size!55; Size!"Hello World"; Size!(SBlock()); auto c = new CBlock(); Size!c; real x = 3.14; writeln(x, ": ", size(&x)); auto _x = &x; Size!_x; writeln(x, ": ", size(&_x)); ubyte[5][5] a; Size!a; ubyte[2][2][3] b; Size!b; ubyte[][] d; d ~= [1, 2, 3, 4, 5]; d ~= [6, 7, 8]; Size!d; SBlock[] e; e ~= SBlock(); e ~= SBlock(); Size!e; SBlock[][] f; f ~= [SBlock()]; f ~= [SBlock()]; Size!f; } s ------------------------- 5: 4 Hello World: 11 SBlock([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]): 13 sizeof.CBlock: 8 3.14: 16 7FFF51B64820: 16 3.14: 8 [[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]: 25 [[[0, 0], [0, 0]], [[0, 0], [0, 0]], [[0, 0], [0, 0]]]: 12 [[1, 2, 3, 4, 5], [6, 7, 8]]: 32 [SBlock([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]), SBlock([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])]: 26 [[SBlock([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])], [SBlock([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0])]]: 32
May 16 2013
On 05/16/2013 08:09 AM, Byron Heads wrote:I am working on d-leveldb wrapper (https://github.com/bheads/d-leveldb)==20and I need to be able to pass blocks of data between D and leveldb API.=I am having rouble getting the byte size of dynamic arrays and POD=20 classes. =20 I can get the right size for 1D dynamic arrays, need a way to compute t=he=20total size. =20 POD Classes always give me the size of the ref, is it possible? =20 -Byron__traits(classInstanceSize, MyClass); ?
May 16 2013
On Thu, 16 May 2013 08:11:35 -0500, 1100110 wrote:On 05/16/2013 08:09 AM, Byron Heads wrote:I missed that one, in my test it returns 29 bytes, 8 for __vptr 8 for __monitor 13 for data now I am wondering way a POD has a vtable. Either way its not safe to store a byte copy in to leveldbI am working on d-leveldb wrapper (https://github.com/bheads/d-leveldb) and I need to be able to pass blocks of data between D and leveldb API. I am having rouble getting the byte size of dynamic arrays and POD classes. I can get the right size for 1D dynamic arrays, need a way to compute the total size. POD Classes always give me the size of the ref, is it possible? -Byron__traits(classInstanceSize, MyClass); ?
May 16 2013
Byron Heads:now I am wondering way a POD has a vtable.In D global structs are PODs, while classe instances are are not PODs. All classes have a vtable because they inherit some methods from the Object class. Bye, bearophile
May 16 2013
Byron Heads <byron.heads gmail.com> On Thu, 16 May 2013 15:32:35 +0200, bearophile wrote:Byron Heads:Thanks, I will just block them since they are unsafe for a database.now I am wondering way a POD has a vtable.In D global structs are PODs, while classe instances are are not PODs. All classes have a vtable because they inherit some methods from the Object class. Bye, bearophile
May 16 2013
On 05/16/2013 08:21 AM, Byron Heads wrote:On Thu, 16 May 2013 08:11:35 -0500, 1100110 wrote: =20b)On 05/16/2013 08:09 AM, Byron Heads wrote:I am working on d-leveldb wrapper (https://github.com/bheads/d-leveld=I.and I need to be able to pass blocks of data between D and leveldb AP=I am having rouble getting the byte size of dynamic arrays and POD classes. I can get the right size for 1D dynamic arrays, need a way to compute==20 I missed that one, in my test it returns 29 bytes, 8 for __vptr 8 for __monitor 13 for data =20 now I am wondering way a POD has a vtable. Either way its not safe to =the total size. POD Classes always give me the size of the ref, is it possible? -Byron__traits(classInstanceSize, MyClass); ?store a byte copy in to leveldbWhy not just use a struct? .sizeof gives those accurately. Oh you wanted both... Maybe take a look at vibe's rest interface? It extracts the members of classes and does funny things with them. Can't say I understand it. Over my head... https://github.com/rejectedsoftware/vibe.d/blob/master/source/vibe/http/r= est.d or final class MyPodClass {} ? And yeah, if you get stuck, std.traits is a really rich resource. =3DD Good luck!
May 16 2013
On Thu, 16 May 2013 08:11:35 -0500, 1100110 wrote:__traits(classInstanceSize, MyClass); ?Any ideas on how to get the element type of an array ie: int[] -> int int[][] -> int[] I am going to block dynamic arrays with more then 1D, since they are holding pointers in the data block
May 16 2013
On Thu, 16 May 2013 13:49:51 +0000, Byron Heads wrote:On Thu, 16 May 2013 08:11:35 -0500, 1100110 wrote:Found ForeachType!T this seems to do the trick. Not the most initiative name for the function but works for my case. Thanks for the help__traits(classInstanceSize, MyClass); ?Any ideas on how to get the element type of an array ie: int[] -> int int[][] -> int[] I am going to block dynamic arrays with more then 1D, since they are holding pointers in the data block
May 16 2013
Byron Heads:Not the most initiative name for the function but works for my case.<It has a strange name because a string (that is a dynamic array) iterated as range (like by map()) has a type different from the same iterated on default with foreach... Bye, bearophile
May 16 2013
On 5/16/13, Byron Heads <byron.heads gmail.com> wrote:On Thu, 16 May 2013 08:11:35 -0500, 1100110 wrote:Try the ElementType template in std.range. There's also ElementEncodingType__traits(classInstanceSize, MyClass); ?Any ideas on how to get the element type of an array ie: int[] -> int int[][] -> int[]
May 16 2013