Copying the contents of a struct from a pointer
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Hi, here's my problem: I have a pointer to a struct (in C++, using VC++ .NET 2005 with MFC). The struct has been allocated from heap memory and contains many fields that are also allocated from the heap (character arrays, etc). How can I copy this straight to another struct? These are the two things I've tried, neither have worked: This is where oldData is a pointer to a MyStruct that has been allocated from the heap:
struct MyStruct *newData = new MyStruct; memcpy(newData, oldData, sizeof(struct MyStruct)); // Do stuff, then copy the data back memcpy(oldData, newData, sizeof(struct MyStruct)); delete newData;And:struct MyStruct newData; newData = *oldData; // Do stuff, then copy the data back oldData = &newData;Neither of these methods work. Is there a way to do this or do I have to copy field by field with the proper memory allocations in newData etc? Thanks!KR
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Hi, here's my problem: I have a pointer to a struct (in C++, using VC++ .NET 2005 with MFC). The struct has been allocated from heap memory and contains many fields that are also allocated from the heap (character arrays, etc). How can I copy this straight to another struct? These are the two things I've tried, neither have worked: This is where oldData is a pointer to a MyStruct that has been allocated from the heap:
struct MyStruct *newData = new MyStruct; memcpy(newData, oldData, sizeof(struct MyStruct)); // Do stuff, then copy the data back memcpy(oldData, newData, sizeof(struct MyStruct)); delete newData;And:struct MyStruct newData; newData = *oldData; // Do stuff, then copy the data back oldData = &newData;Neither of these methods work. Is there a way to do this or do I have to copy field by field with the proper memory allocations in newData etc? Thanks!KR
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Hi, here's my problem: I have a pointer to a struct (in C++, using VC++ .NET 2005 with MFC). The struct has been allocated from heap memory and contains many fields that are also allocated from the heap (character arrays, etc). How can I copy this straight to another struct? These are the two things I've tried, neither have worked: This is where oldData is a pointer to a MyStruct that has been allocated from the heap:
struct MyStruct *newData = new MyStruct; memcpy(newData, oldData, sizeof(struct MyStruct)); // Do stuff, then copy the data back memcpy(oldData, newData, sizeof(struct MyStruct)); delete newData;And:struct MyStruct newData; newData = *oldData; // Do stuff, then copy the data back oldData = &newData;Neither of these methods work. Is there a way to do this or do I have to copy field by field with the proper memory allocations in newData etc? Thanks!KR
KellyR wrote:
Neither of these methods work.
No surprise there, since
memcpy()has no way of getting to that other heap data. It only knows about the data in theMyStructstructure.KellyR wrote:
Is there a way to do this or do I have to copy field by field with the proper memory allocations in newData etc?
I would implement an assignemnt operator in the structure:
const MyStruct& operator=( const MyStruct &b )
{
...
return *this;
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