Any cryptographic primitives use memory to store stuff. This class abstracts all types that hold some memory. Cryptographic application often requires securing the memory from being swapped out (think of memory used to store private keys or passwords). This abstraction supports memory securing. If your platform supports memory locking, then securing a memory will prevent the memory from being swapped to the disk. Once secured the memory location is overwritten by nonsense before being freed.

While some basic memory elements like MemoryCell are exposed from the library, often we require compound memory objects built out of simpler ones. The Applicative instance of the Alloc can be made use of in such situation to simplify such instance declaration as illustrated in the instance declaration for a pair of memory elements.

instance (Memory ma, Memory mb) => Memory (ma, mb) where

   memoryAlloc             = (,) <$> memoryAlloc <*> memoryAlloc

   unsafeToPointer (ma, _) =  unsafeToPointer ma

A memory element that holds nothing.

Apply some low level action on the underlying buffer of the memory.

Perform an action which makes use of this memory. The memory allocated will automatically be freed when the action finishes either gracefully or with some exception. Besides being safer, this method might be more efficient as the memory might be allocated from the stack directly and will have very little GC overhead.

Similar to withMemory but allocates a secure memory for the action. Secure memories are never swapped on to disk and will be wiped clean of sensitive data after use. However, be careful when using this function in a child thread. Due to the daemonic nature of Haskell threads, if the main thread exists before the child thread is done with its job, sensitive data can leak. This is essentially a limitation of the bracket which is used internally.

A memory allocator for the memory type mem. The Applicative instance of Alloc can be used to build allocations for complicated memory elements from simpler ones and takes care of handling the size/offset calculations involved.

Allocates a buffer of size l and returns the pointer to it pointer.

Memories that can be initialised with a pure value. The pure value resides in the Haskell heap and hence can potentially be swapped. Therefore, this class should be avoided if compromising the initialisation value can be dangerous. Look into the type class WriteAccessible instead.

Memories from which pure values can be extracted. Much like the case of the Initialisable class, avoid using this interface if you do not want the data extracted to be swapped. Use the ReadAccessible class instead.

Apply the given function to the value in the cell. For a function f :: b -> a, the action modify f first extracts a value of type b from the memory element, applies f to it and puts the result back into the memory.

modifyMem f mem = do b <- extract mem
                     initialise (f b) mem

Data type that gives an access buffer to portion of the memory.

This class captures memories from which bytes can be extracted directly from (portions of) its buffer.

This class captures memories that can be initialised by writing bytes to (portions of) its buffer.

Transfer the bytes from the source memory to the destination memory. The total bytes transferred is the minimum of the bytes available at the source and the space available at the destination.

A memory location to store a value of type having Storable instance.

Copy the contents of one memory cell to another.

Work with the underlying pointer of the memory cell. Useful while working with ffi functions.

The location where the actual storing of element happens. This pointer is guaranteed to be aligned to the alignment restriction of a