FileBucket

FileBucket implements a simple mechanism to store and recover a large quantity of data for the duration of the hosting process. It is intended to act as a local-cache for a remote data-source, or as a spillover area for large in-memory cache instances.

Note that any and all stored data is rendered invalid the moment a FileBucket object is garbage-collected.

The implementation follows a fixed-capacity record scheme, where content can be rewritten in-place until said capacity is reached. At such time, the altered content is moved to a larger capacity record at end-of-file, and a hole remains at the prior location. These holes are not collected, since the lifespan of a FileBucket is limited to that of the host process.

All index keys must be unique. Writing to the FileBucket with an existing key will overwrite any previous content. What follows is a contrived example:

class FileBucket {

struct BlockSize;

static

enum BlockSize EighthK;

static

enum BlockSize HalfK;

static

enum BlockSize OneK;

static

enum BlockSize TwoK;

static

enum BlockSize FourK;

static

enum BlockSize EightK;

static

enum BlockSize SixteenK;

static

enum BlockSize ThirtyTwoK;

static

enum BlockSize SixtyFourK;

this(const(char)[] path, BlockSize block, uint initialRecords);

int getBufferSize();

const(char)[] getFilePath();

long length();

void[] get(const(char)[] key);

void remove(const(char)[] key);

void put(const(char)[] key, const(char)[] data);

void close();

}

Constructors

this this(const(char)[] path, BlockSize block, uint initialRecords): Construct a FileBucket with the provided path, record-size, and inital record count. The latter causes records to be pre-allocated, saving a certain amount of growth activity. Selecting a record size that roughly matches the serialized content will limit 'thrashing'.

Members

Functions

close void close(): Close this FileBucket -- all content is lost.
get void[] get(const(char)[] key): Return the serialized data for the provided key. Returns null if the key was not found.
getBufferSize int getBufferSize(): Return the block-size in use for this FileBucket
getFilePath const(char)[] getFilePath(): Return where the FileBucket is located
length long length(): Return the currently populated size of this FileBucket
put void put(const(char)[] key, const(char)[] data): Write a serialized block of data, and associate it with the provided key. All keys must be unique, and it is the responsibility of the programmer to ensure this. Reusing an existing key will overwrite previous data.
remove void remove(const(char)[] key): Remove the provided key from this FileBucket.

Static variables

EightK enum BlockSize EightK;: Undocumented in source.
EighthK enum BlockSize EighthK;
FourK enum BlockSize FourK;
HalfK enum BlockSize HalfK;
OneK enum BlockSize OneK;
SixteenK enum BlockSize SixteenK;
SixtyFourK enum BlockSize SixtyFourK;
ThirtyTwoK enum BlockSize ThirtyTwoK;
TwoK enum BlockSize TwoK;: Undocumented in source.

Structs

BlockSize struct BlockSize: Define the capacity (block-size) of each record

Examples

const(char)[] text = "this is a test";

auto bucket = new FileBucket ("bucket.bin", FileBucket.FileBucket.HalfK);

// insert some data, and retrieve it again
bucket.put ("a key", text);
char[] b = cast(char[]) bucket.get ("a key");

assert (b == text);
bucket.close;

FileBucket

Constructors

Members

Functions

Static variables

Structs

Examples

Meta

Source