Storing 2 longs in a single variable
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How can i store 2 longs in a single variable. Similare to storing 2 shorts in a long with the MAKELONG macro. Can i do this with Long64? Thanks
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A structure would solve the issue would it not? #pragma pack(1) typedef struct two_longs_dont_make_a_right { long one; long erone; } two_longs; ? Why in 'one' variable? Ryan Baillargeon Software Specialist Fuel Cell Technologies Inc.
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I need to save an Array of 2 shorts and long to a text file. I just figured it would be easier to save them in one variable that to seperate them with commas or something like that.
Why not use a structure in combination with a union, like so:
typedef struct tagTwoLongs
{
union
{
struct
{
long Long1;
long Long2;
};
__int64 OneVariable;
};
}TwoLongs;Now you can refer to the two longs separately, via Long1 and Long2, or together, via OneVariable. Chris Richardson
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Why not use a structure in combination with a union, like so:
typedef struct tagTwoLongs
{
union
{
struct
{
long Long1;
long Long2;
};
__int64 OneVariable;
};
}TwoLongs;Now you can refer to the two longs separately, via Long1 and Long2, or together, via OneVariable. Chris Richardson
Make sure that the pack pragma is 4 or less for the union technique to work. You might want to ensure this by temporarily specifying the packing alignment:
#pragma pack(push,4) typedef struct tagTwoLongs { union { struct { long Long1; long Long2; }; __int64 OneVariable; }; }TwoLongs; #pragma pack(pop)P.S. Is there a way to get a compile time assertion that sizeof(long)==4? -
Make sure that the pack pragma is 4 or less for the union technique to work. You might want to ensure this by temporarily specifying the packing alignment:
#pragma pack(push,4) typedef struct tagTwoLongs { union { struct { long Long1; long Long2; }; __int64 OneVariable; }; }TwoLongs; #pragma pack(pop)P.S. Is there a way to get a compile time assertion that sizeof(long)==4?Good call on the packing. I forgot about that. Scott H. Settlemier wrote: P.S. Is there a way to get a compile time assertion that sizeof(long)==4? Yeah, in winnt.h, there's a macro called C_ASSERT. Here's it's definition, and the comment that describes it:
//
// C_ASSERT() can be used to perform many compile-time assertions:
// type sizes, field offsets, etc.
//
// An assertion failure results in error C2118: negative subscript.
//#define C_ASSERT(e) typedef char __C_ASSERT__[(e)?1:-1]
Chris Richardson
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Good call on the packing. I forgot about that. Scott H. Settlemier wrote: P.S. Is there a way to get a compile time assertion that sizeof(long)==4? Yeah, in winnt.h, there's a macro called C_ASSERT. Here's it's definition, and the comment that describes it:
//
// C_ASSERT() can be used to perform many compile-time assertions:
// type sizes, field offsets, etc.
//
// An assertion failure results in error C2118: negative subscript.
//#define C_ASSERT(e) typedef char __C_ASSERT__[(e)?1:-1]
Chris Richardson
ooh, nice. thanks. I've been wanting that ability for a long time. I see they just sorta kludged one up there. (neg index error. :laugh:) Too bad this wasn't added to the language.
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Make sure that the pack pragma is 4 or less for the union technique to work. You might want to ensure this by temporarily specifying the packing alignment:
#pragma pack(push,4) typedef struct tagTwoLongs { union { struct { long Long1; long Long2; }; __int64 OneVariable; }; }TwoLongs; #pragma pack(pop)P.S. Is there a way to get a compile time assertion that sizeof(long)==4? -
Why not use a structure in combination with a union, like so:
typedef struct tagTwoLongs
{
union
{
struct
{
long Long1;
long Long2;
};
__int64 OneVariable;
};
}TwoLongs;Now you can refer to the two longs separately, via Long1 and Long2, or together, via OneVariable. Chris Richardson
You mean the Win32 LARGE_INTEGER structure defined in WinNT.h
CPUA 0x5041 Sonork 100.11743 Chicken Little "So it can now be written in stone as a testament to humanities achievments "PJ did Pi at CP"." Colin Davies Within you lies the power for good - Use it!
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You mean the Win32 LARGE_INTEGER structure defined in WinNT.h
CPUA 0x5041 Sonork 100.11743 Chicken Little "So it can now be written in stone as a testament to humanities achievments "PJ did Pi at CP"." Colin Davies Within you lies the power for good - Use it!
I only replied to him an idea and a simple definition. I suppose I could have used (and would have used) LARGE_INTEGER as my example, but I didn't think of it at the time. Chris Richardson
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longOne = i64 / (unsigned long)-1; longTwo = i64 - (longOne * (unsigned long)-1); or something similar -c
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