FLSharedKeys represents a mapping from short strings to small integers in the range [0...2047].
It's used by FLDict to abbreviate dictionary keys. A shared key can be stored in a fixed two bytes and is faster to compare against. However, the same mapping has to be used when encoding and when accessing the Dict.
To use shared keys: Call FLSharedKeys_New to create a new empty mapping. After creating an FLEncoder, call FLEncoder_SetSharedKeys so dictionary keys will be added to the mapping and written in integer form. When loading Fleece data, use FLDoc_FromResultData and pass the FLSharedKeys as a parameter. Save the mapping somewhere by calling FLSharedKeys_GetStateData or FLSharedKeys_WriteState. You can later reconstitute the mapping by calling FLSharedKeys_LoadStateData or FLSharedKeys_LoadState on a new empty instance.
typedef bool(* FLSharedKeysReadCallback) (void *FL_NULLABLE context, FLSharedKeys) typedef struct _FLSharedKeyScope * FLSharedKeyScope NODISCARD FLEECE_PUBLIC FLSharedKeys FLSharedKeys_New (void) Creates a new empty FLSharedKeys object, which must eventually be released.key, else NULL.
oldCount.
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.
NODISCARD FLEECE_PUBLIC FLSliceResult FLCreateJSONDelta (FLValue FL_NULLABLE old, FLValue FL_NULLABLE nuu) Returns JSON that encodes the changes to turn the valueold into nuu.
old into nuu.
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.
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.
base value passed to FLEncoder_Amend.
For use with FLDoc_FromResultData.
This option prevents the function from parsing the data at all; you are responsible for locating the FLValues in it. This is for the case where you have trusted data in a custom format that contains Fleece- encoded data within it. You still need an FLDoc to access the data safely (especially to retain FLValues), but it can't be parsed as-is.
◆ FLSharedKeyScope ◆ FLSharedKeysReadCallback ◆ FLApplyJSONDelta()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.
old value used when creating the jsonDelta. jsonDelta A JSON-encoded delta created by FLCreateJSONDelta or FLEncodeJSONDelta. outError On failure, error information will be stored where this points, if non-null.
nuu value, encoded as Fleece, or null if an error occurred.
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.)
old data.
old to nuu, or NULL on (extremely unlikely) failure.
Directly converts JSON data to Fleece-encoded data.
Not commonly needed. Prefer FLDoc_FromJSON instead.
◆ FLData_Dump()Produces a human-readable dump of Fleece-encoded data.
This is only useful if you already know, or want to learn, the encoding format.
◆ FLDump()Debugging function that returns a C string of JSON.
Does not free the string's memory!
◆ FLDumpData()Debugging function that parses Fleece data and returns a C string of JSON.
Does not free the string's memory!
◆ FLEncodeApplyingJSONDelta()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.
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.)
FLEncoder_GetError for details.
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.)
old data. jsonEncoder An encoder to write the JSON to. Must have been created using FLEncoder_NewWithOptions, with JSON or JSON5 format.
Tells the encoder to logically append to the given Fleece document, rather than making a standalone document.
Any calls to FLEncoder_WriteValue() where the value points inside the base data will write a pointer back to the original value. The resulting data returned by FLEncoder_FinishDoc() will NOT be standalone; it can only be used by first appending it to the base data.
extern flag. This allows them to be resolved using the FLResolver_Begin function, so that when the delta is used the base document can be anywhere in memory, not just immediately preceding the delta document.
Finishes encoding the current item, and returns its offset in the output data.
◆ FLEncoder_GetBase()Returns the base value passed to FLEncoder_Amend.
Returns the byte offset in the encoded data where the next value will be written.
(Due to internal buffering, this is not the same as FLEncoder_BytesWritten.)
◆ FLEncoder_LastValueWritten()Returns an opaque reference to the last complete value written to the encoder, if possible.
Fails (returning kFLNoWrittenValue) if nothing has been written, or if the value is inline and can't be referenced this way – that only happens with small scalars or empty collections.
◆ FLEncoder_Snip()Returns the data written so far as a standalone Fleece document, whose root is the last value written.
You can continue writing, and the final output returned by FLEncoder_Finish will consist of everything after this point. That second part can be used in the future by loading it as an FLDoc with the first part as its extern reference.
Tells the encoder not to write the two-byte Fleece trailer at the end of the data.
This is only useful for certain special purposes.
◆ FLEncoder_WriteValueAgain()Writes another reference (a "pointer") to an already-written value, given a reference previously returned from FLEncoder_LastValueWritten.
The effect is exactly the same as if you wrote the entire value again, except that the size of the encoded data only grows by 4 bytes. Returns false if the reference couldn't be written.
◆ FLJSON5_ToJSON()Converts valid JSON5 https://json5.org to JSON.
Among other things, it converts single quotes to double, adds missing quotes around dictionary keys, removes trailing commas, and removes comments.
In a JSON encoder, adds a newline ('
') and prepares to start encoding another top-level object.
The encoder MUST be not be within an array or dict. Has no effect in a Fleece encoder.
◆ FLSharedKeys_Count()Returns the number of keys in the mapping.
This number increases whenever the mapping is changed, and never decreases.
◆ FLSharedKeys_Decode()Returns the key string that maps to the given integer key, else NULL.
Disable caching of the SharedKeys.
◆ FLSharedKeys_Encode()Maps a key string to a number in the range [0...2047], or returns -1 if it isn't mapped.
If the key doesn't already have a mapping, and the add flag is true, a new mapping is assigned and returned. However, the add flag has no effect if the key is unmappable (is longer than 16 bytes or contains non-identifier characters), or if all available integers have been assigned.
Returns a data blob containing the current state (all the keys and their integers.)
◆ FLSharedKeys_LoadState() ◆ FLSharedKeys_LoadStateData()Updates an FLSharedKeys with saved state data created by FLSharedKeys_GetStateData.
Returns true if new keys were added, false if not.
◆ FLSharedKeys_New()Creates a new empty FLSharedKeys object, which must eventually be released.
◆ FLSharedKeys_NewWithRead() ◆ FLSharedKeys_Release()Decrements the reference count of an FLSharedKeys, freeing it when it reaches zero.
◆ FLSharedKeys_Retain()Increments the reference count of an FLSharedKeys.
◆ FLSharedKeys_RevertToCount()Reverts an FLSharedKeys by "forgetting" any keys added since it had the count oldCount.
Writes the current state to a Fleece encoder as a single value, which can later be decoded and passed to FLSharedKeys_LoadState.
◆ FLSharedKeyScope_Free() ◆ FLSharedKeyScope_WithRange()Registers a range of memory containing Fleece data that uses the given shared keys.
This allows Dict accessors to look up the values of shared keys.
◆ FLValue_FromData()Returns a pointer to the root value in the encoded data, or NULL if validation failed.
You should generally use an FLDoc instead; it's safer. Here's why:
On the plus side, FLValue_FromData is extremely fast: it allocates no memory, only scans enough of the data to ensure it's valid (and if trust is set to kFLTrusted, it doesn't even do that.)
But it's potentially very dangerous: the FLValue, and all values found through it, are only valid as long as the input data remains intact and unchanged. If you violate that, the values will be pointing to garbage and Bad Things will happen when you access them...
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