Eran's Interview Question

mem.c

// Implement a virtual memory manager that takes a large contiguous block of memory and manages allocations
// and deallocations on it.
// The entire buffer needs to be available for allocation. You can use whatever extra memory you need to manage it.
// You do need to consider the case of fragmentation.
// 
// Example test case: 
//   - initialize a buffer of 5 chars: ----- 
//   - allocate 5 blocks of 1 char:    XXXXX
//   - free the 2nd and 4th:           X-X-X 
//   - Can you now call Alloc(2) ? What would you need to change in the interface to be able to do so?
//
// Clearly document design choices, algorithm and possible optimizations.
// While we require you to implement one memory allocation algorithm,
// also document future looking design considerations.
// There are many ways to implement this memory manager. It is important for us to know why you implemented it the way you did, 
// whats the pros and cons to your implementation, etc.
//
// While the interface below is written in C++, feel free to implement the MemoryManager in the language of your choosing. 
// If you need to change the interface due to language limitations (for example, not all languages have pointers) 
// or for any other reason - please explain your reasoning for the change.
// For example:
//   - if we wanted to use a different memory management strategy, how would we make that change.
//   - is your solution thread-safe?  whaat would it take to make it thread safe?
//
// *** Requirements *** 
// 1. Working code (obviously).
// 2. Unit tests (using a unit testing library of your choosing)
// 3. Documentation (as describe in the 2nd paragraph above) 
//

class MemoryManager {
  public:
    // buffer is a large chunk of contiguous memory.
    // num_bytes is the size of the buffer.
    MemoryManager(char * buffer, int num_bytes);

    // Allocate memory of size 'size'. Use malloc() like semantics.
    char* Alloc(int size);

    // Free up previously allocated memory.  Use free() like semantics.
    void Free(char*);
};