Crate

Crate is an extensible C library providing a set of common data structures and a way to persist them to disk.

A desire to have python-like serialization features, i.e. pickle, but in a C environment spurred the creation of this library.

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The Crate Interface

This libraries central concept is storing data in crates. Crates may be persisted to a file on disk at any time and then loaded from that file at any point in the future. The dsCrate structure implements this central concept with the public API in crate.h.

Use dsOpen() and dsClose() to open an existing crate file, create a new one or close a crate.

dsCrate *crate = dsOpen("path/to/myCrate", 1, 0);

dsClose(crate);

Instead of having to pass the dsCrate handle to nearly every function in the library, you set the 'active' crate once and then operate on it many times. The 'active' crate can be set using dsSet().

dsSet(crate);

A program may have several crates open simultaneously. Since the dsCrate interface is thread-safe and the dsSet() API uses thread-local storage, each thread may set a different 'active' crate. But, there can be only one 'active' crate per-thread.

Use dsAlloc() and dsFree() to add and remove data from a create.

int *data = dsAlloc(sizeof(*data));

*data = 42;

dsFree(data);

Using dsSetIndex() and dsGetIndex(), ...

int *data = dsAlloc(sizeof(*data));

dsSetIndex(data, sizeof(*data));
data = dsGetIndex();

As data is added and removed from a crate it is asynchronously flushed to the crate file given to dsOpen(). Given an undefined amount of time, all changes will "eventually" be flushed to the file. The changes may be flushed synchronously and on-demand by calling either dsSync() or dsClose().

dsSync(1);
dsClose(crate);

Using dsSnapshot() a snapshot-in-time of a crate may be created at any time. This affectively makes a copy of a crate.

dsSnapshot("path/to/snapshot");

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Data Structures

This library also provides a set of common data structures that all sit on top of the dsCrate interface. That means each data structure is persisted to a crate file and snapshots be taken.

List example:

dsCrate *crate = dsOpen("path/to/myCrate", 1, 1);

dsList *list = dsListAlloc();

dsSetIndex(list, sizeof(*list));

int i;
for (i = 0; i < 10; i++) {
	int *data = dsAlloc(sizeof(*data));
	*data = i;
	dsListAdd(list, data);
}

dsListEntry *e;
for (e = dsListBegin(list); e != NULL; e = dsListNext(e)) {
	int *data = dsListData(e);
	printf("%d\n", *data);
}