[Boost-users] [Interprocess] Named objects with 'Managed External Buffer' (newbie)

Subject: [Boost-users] [Interprocess] Named objects with 'Managed External Buffer' (newbie)
From: Jorge Bellon (jbellon_at_[hidden])
Date: 2014-04-25 11:13:06

Good afternoon,
First, I apologize if I'm asking something obvious or outside the acceptable topics. I'm starting to 
use Boost so I'm quite newbie.

I'm interested in using the managed_external_buffer in order to perform buffer copies into a 
created buffer that was created previously. Therefore, I will be storing mostly raw data into that 
buffer.

Basically, I'm trying to do the following:
Suppose a program uses the following int array:
  int numbers[10] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };

Eventually, I have to copy a chunk of that array into a pre-allocated buffer (i.e. the 
managed_external_buffer). Let the chunk be defined with:

typedef struct {
  void* addr;
  size_t size;
} chunk_t;

However, these chunks can overlap, so I will sometimes merge two overlapping chunks into a 
bigger one. Example:
  // Chunk 1
  chunk1_addr = (void*)&numbers[3];
  chunk1_size = 3 * sizeof(int);
  // Chunk 2
  chunk2_addr = (void*) &numbers[4];
  chunk2_size = 4 * sizeof(int);

The desired result is a single chunk containing {3, 4, 5, 6, 7}.

The proposed problem is the merge, but how to find those chunks in the managed_external_buffer, 
so my question is the following:
   - Would it be possible to use named objects with another data type other than CharType and use 
managed_external_buffer::find to look for them? The thing is I could generate a hash or a numerical 
ID to identify the chunk. Generating a string using that number could be done but it would not be 
efficient.

Otherwise, I guess I would have to keep a map (or other collection) with the <chunk ID, chunk 
pointer> pairs, define the managed_external_buffer with boost::interprocess::null_index (since I 
won't be using named objects) and use it through allocate and deallocate. Is this correct?

Thanks in advance,
  Jorge

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