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POAllocate chunk of memory for array of structs
 

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  1. POAllocate chunk of memory for array of structs
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    <p>I need an array of this struct allocated in one solid chunk of memory. The length of "char *extension" and "char *type" are not known at compile time.</p> <pre><code>struct MIMETYPE { char *extension; char *type; }; </code></pre> <p>If I used the "new" operator to initialize each element by itself, the memory may be scattered. This is how I tried to allocate a single contiguous block of memory for it:</p> <pre><code>//numTypes = total elements of array //maxExtension and maxType are the needed lengths for the (char*) in the struct //std::string ext, type; unsigned int size = (maxExtension+1 + maxType+1) * numTypes; mimeTypes = (MIMETYPE*)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, size); </code></pre> <p>But, when I try to load the data in like this, the data is all out of order and scattered when I try to access it later.</p> <pre><code>for(unsigned int i = 0; i &lt; numTypes; i++) { //get data from file getline(fin, line); stringstream parser.str(line); parser &gt;&gt; ext &gt;&gt; type; //point the pointers at a spot in the memory that I allocated mimeTypes[i].extension = (char*)(&amp;mimeTypes[i]); mimeTypes[i].type = (char*)((&amp;mimeTypes[i]) + maxExtension); //copy the data into the elements strcpy(mimeTypes[i].extension, ext.c_str()); strcpy(mimeTypes[i].type, type.c_str()); } </code></pre> <p>can anyone help me out?</p> <p>EDIT:</p> <pre><code>unsigned int size = (maxExtension+1 + maxType+1); mimeTypes = (MIMETYPE*)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, size * numTypes); for(unsigned int i = 0; i &lt; numTypes; i++) strcpy((char*)(mimeTypes + (i*size)), ext.c_str()); strcpy((char*)(mimeTypes + (i*size) + (maxExtension+1)), type.c_str()); </code></pre>
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      1. VTUpMod
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    1. COIs there a reason you can't just use `std::vector` and `std::string`?
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    2. COI'm with GMan on this. Why do you want to play this trick? Have you measured that this is a necessary optimization?
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    3. COIts for a webserver. There are a total of 646 types that may need to be compared for each request, for each connected user. Could get real slow.
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      1. USbitwise
 

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