Fleece Delta Compression

These functions implement a fairly-efficient "delta" encoding that encapsulates the changes needed to transform one Fleece value into another. More...

Functions
FLSliceResult	FLCreateJSONDelta (FLValue old, FLValue nuu)
	Returns JSON that encodes the changes to turn the value old into nuu. More...
bool	FLEncodeJSONDelta (FLValue old, FLValue nuu, FLEncoder jsonEncoder)
	Writes JSON that describes the changes to turn the value old into nuu. More...
FLSliceResult	FLApplyJSONDelta (FLValue old, FLSlice jsonDelta, FLError *error)
	Applies the JSON data created by CreateJSONDelta to the value old, which must be equal to the old value originally passed to FLCreateJSONDelta, and returns a Fleece document equal to the original nuu value. More...
bool	FLEncodeApplyingJSONDelta (FLValue old, FLSlice jsonDelta, FLEncoder encoder)
	Applies the (parsed) JSON data created by CreateJSONDelta to the value old, which must be equal to the old value originally passed to FLCreateJSONDelta, and writes the corresponding nuu value to the encoder. More...

Detailed Description

These functions implement a fairly-efficient "delta" encoding that encapsulates the changes needed to transform one Fleece value into another.

The delta is expressed in JSON form.

A delta can be stored or transmitted as an efficient way to produce the second value, when the first is already present. Deltas are frequently used in version-control systems and efficient network protocols.

Function Documentation

FLApplyJSONDelta()

FLSliceResult FLApplyJSONDelta	(	FLValue	old,
		FLSlice	jsonDelta,
		FLError *	error
	)

Applies the JSON data created by CreateJSONDelta to the value old, which must be equal to the old value originally passed to FLCreateJSONDelta, and returns a Fleece document equal to the original nuu value.

Parameters

old	A value that's typically the old/original state of some data. This must be equal to the old value used when creating the jsonDelta.
jsonDelta	A JSON-encoded delta created by FLCreateJSONDelta or FLEncodeJSONDelta.
error	On failure, error information will be stored where this points, if non-null.

Returns

The corresponding nuu value, encoded as Fleece, or null if an error occurred.

FLCreateJSONDelta()

FLSliceResult FLCreateJSONDelta	(	FLValue	old,
		FLValue	nuu
	)

Returns JSON that encodes the changes to turn the value old into nuu.

(The format is documented in Fleece.md, but you should treat it as a black box.)

Parameters

old	A value that's typically the old/original state of some data.
nuu	A value that's typically the new/changed state of the old data.

Returns

JSON data representing the changes from old to nuu, or NULL on (extremely unlikely) failure.

FLEncodeApplyingJSONDelta()

bool FLEncodeApplyingJSONDelta	(	FLValue	old,
		FLSlice	jsonDelta,
		FLEncoder	encoder
	)

Applies the (parsed) JSON data created by CreateJSONDelta to the value old, which must be equal to the old value originally passed to FLCreateJSONDelta, and writes the corresponding nuu value to the encoder.

Parameters

old	A value that's typically the old/original state of some data. This must be equal to the old value used when creating the jsonDelta.
jsonDelta	A JSON-encoded delta created by FLCreateJSONDelta or FLEncodeJSONDelta.
encoder	A Fleece encoder to write the decoded nuu value to. (JSON encoding is not supported.)

Returns

True on success, false on error; call FLEncoder_GetError for details.

FLEncodeJSONDelta()

bool FLEncodeJSONDelta	(	FLValue	old,
		FLValue	nuu,
		FLEncoder	jsonEncoder
	)

Writes JSON that describes the changes to turn the value old into nuu.

(The format is documented in Fleece.md, but you should treat it as a black box.)

Parameters

old	A value that's typically the old/original state of some data.
nuu	A value that's typically the new/changed state of the old data.
jsonEncoder	An encoder to write the JSON to. Must have been created using FLEncoder_NewWithOptions, with JSON or JSON5 format.

Returns

True on success, false on (extremely unlikely) failure.