coffi.mem
Functions for managing native allocations, resource scopes, and (de)serialization.
For any new type to be implemented, three multimethods must be overriden, but which three depends on the native representation of the type.
If the native representation of the type is a primitive (whether or not other data beyond the primitive is associated with it, as e.g. a pointer), then primitive-type must be overriden to return which primitive type it is serialized as, then serialize* and deserialize* should be overriden.
If the native representation of the type is a composite type, like a union, struct, or array, then c-layout must be overriden to return the native layout of the type, and serialize-into and deserialize-from should be overriden to allow marshaling values of the type into and out of memory segments.
When writing code that manipulates a segment, it’s best practice to use with-acquired on the segment-scope in order to ensure it won’t be released during its manipulation.
add-close-action!
(add-close-action! scope action)Adds a 0-arity function to be run when the scope closes.
address-of
(address-of addressable)Gets the address of a given segment.
This value can be used as an argument to functions which take a pointer.
address?
(address? addr)Checks if an object is a memory address.
nil is considered an address.
alloc
(alloc size)(alloc size scope)Allocates size bytes.
If a scope is provided, the allocation will be reclaimed when it is closed.
alloc-instance
(alloc-instance type)(alloc-instance type scope)Allocates a memory segment for the given type.
alloc-with
(alloc-with allocator size)(alloc-with allocator size alignment)Allocates size bytes using the allocator.
as-segment
(as-segment address size scope)(as-segment address size scope cleanup)Dereferences an address into a memory segment associated with the scope.
If cleanup is provided, it is a 0-arity function run when the scope is closed. This can be used to register a free method for the memory, or do other cleanup in a way that doesn’t require modifying the code at the point of freeing, and allows shared or garbage collected resources to be freed correctly.
c-layout
multimethod
Gets the layout object for a given type.
If a type is primitive it will return the appropriate primitive layout (see c-prim-layout).
Otherwise, it should return a GroupLayout for the given type.
clone-segment
(clone-segment segment)(clone-segment segment scope)Clones the content of segment into a new segment of the same size.
connected-scope
(connected-scope)Constructs a new scope to reclaim all connected resources at once.
The scope may be shared across threads, and all resources created with it will be cleaned up at the same time, when all references have been collected.
This type of scope cannot be closed, and therefore should not be created in a with-open clause.
defalias
macro
(defalias new-type aliased-type)Defines a type alias from new-type to aliased-type.
This creates needed serialization and deserialization implementations for the aliased type.
deserialize
(deserialize obj type)Deserializes an arbitrary type.
For types which have a primitive representation, this deserializes the primitive representation. For types which do not, this deserializes out of a segment.
deserialize*
multimethod
Deserializes a primitive object into a Clojure data structure.
This is intended for use with types that are returned as a primitive but which need additional processing before they can be returned.
deserialize-from
multimethod
Deserializes the given segment into a Clojure data structure.
For types that serialize to primitives, a default implementation will deserialize the primitive before calling deserialize*.
Implementations of this should be inside a with-acquired block for the the segment’s scope if they perform multiple memory operations.
global-scope
(global-scope)Constructs the global scope, which will never reclaim its resources.
This scope may be shared across threads, but is intended mainly in cases where memory is allocated with alloc but is either never freed or whose management is relinquished to a native library, such as when returned from a callback.
java-layout
(java-layout type)Gets the Java class to an argument of this type for a method handle.
If a type serializes to a primitive it returns return a Java primitive type. Otherwise, it returns MemorySegment.
primitive-type
multimethod
Gets the primitive type that is used to pass as an argument for the type.
This is for objects which are passed to native functions as primitive types, but which need additional logic to be performed during serialization and deserialization.
Implementations of this method should take into account that type arguments may not always be evaluated before passing to this function.
Returns nil for any type which does not have a primitive representation.
scope-allocator
(scope-allocator scope)Constructs a segment allocator from the given scope.
This is primarily used when working with unwrapped downcall functions. When a downcall function returns a non-primitive type, it must be provided with an allocator.
seq-of
(seq-of type segment)Constructs a lazy sequence of type elements deserialized from segment.
serialize
(serialize obj type)(serialize obj type scope)Serializes an arbitrary type.
For types which have a primitive representation, this serializes into that representation. For types which do not, it allocates a new segment and serializes into that.
serialize*
multimethod
Constructs a serialized version of the obj and returns it.
Any new allocations made during the serialization should be tied to the given scope, except in extenuating circumstances.
This method should only be implemented for types that serialize to primitives.
serialize-into
multimethod
Writes a serialized version of the obj to the given segment.
Any new allocations made during the serialization should be tied to the given scope, except in extenuating circumstances.
This method should be implemented for any type which does not override c-layout.
For any other type, this will serialize it as serialize* before writing the result value into the segment.
Implementations of this should be inside a with-acquired block for the scope if they perform multiple memory operations.
slice
(slice segment offset)(slice segment offset size)Get a slice over the segment with the given offset.
slice-global
(slice-global address size)Gets a slice of the global address space.
Because this fetches from the global segment, it has no associated scope, and therefore the reference created here cannot prevent the value from being freed. Be careful to ensure that you are not retaining an object incorrectly.
slice-into
(slice-into address segment)(slice-into address segment size)Get a slice into the segment starting at the address.
slice-segments
(slice-segments segment size)Constructs a lazy seq of size-length memory segments, sliced from segment.
stack-scope
(stack-scope)Constructs a new scope for use only in this thread.
The memory allocated within this scope is cheap to allocate, like a native stack.
with-acquired
macro
(with-acquired scopes & body)Acquires one or more scopes until the body completes.
This is only necessary to do on shared scopes, however if you are operating on an arbitrary passed scope, it is best practice to wrap code that interacts with it wrapped in this.