NAME Data::FastPack - FastPack Record format, Parsing and Serialising DESCRIPTION Implements an incremental FastPack encoder and decoder for arbitrary reliable streams of data, with arbitrary name data channels. This document also defines the FastPack format CONCEPTS The message format is primarily intended to store a sequence of time indexed values which are to be parameterized to another channel. For example indexing a sensor to position where both the sensor and the position are sampled separately, but can be stored with the same time base. It's small footprint and easy encoding/decoding also make is a great format for IPC. It optionally (but highly recommended ) supports name aliasing for messages. This saves bytes in storage or transmission, by dynamically assigning a integer value to a message ID during encoding. The management of mappings is automatic and inserted into the stream of encoded messages. This makes it seamless for the decoder to reconstruct the named message. There is only one reserved channel id, 0 , which is a meta data channel for application level. This channel payload is JSON or MessagePack encoded. If no payload is present, this is a namespace reset, which will remove named id mappings so new ones can be generated from future data The meta data semantics are application dependant, giving great flexibility, in time base, channel relationships etc * Efficient use of memory access for ARM cpus Multi byte data types are stored in little endian order, unless otherwise specified in the meta data. Payloads are also on a 8 byte boundary allows direct access for double precision float * Messages stored in one or more files Multiple streams of message can be stored in a single file if they share a time base. For streams that have differing time bases, they are stored in a separate files. This give good compression ability * External defintition file(s) for message types if required. The definitions of a file can be pointed to externally, or can be stored internally in a meta data message * Highly compresssable and suitable for self contained web applications The message time, id, length fields will be mostly unchanging when multiple message source of same time base are recorded together. The 24 byte header will basically be reduced to 1 or 2 bytes after compression for most messages. Timimg Timing data is a double float field and can represent many different timing scenarios. * Direct time (seconds) The simplest case is the storing seconds as floating point values in the field. Whether the value is a difference to the previous message or an absolute value is based on definition messages for the file. * Multiple of a time base Similar to direct time above, however the value is multiplied by an external time base factor to generate the actual time. * Argument/index into a timing function. The value is used as an index into a timing function stored in external JavaScript, which when called calculates a time. i.e. for processing video with fixed non integer frame rates For a system reporting only a single message, the time field will constantly be updated for each message. However with multiple channels only the first message from the group will have a non zero time when using difference mode. Most messages in a system will have a 0 time because of this. Padding Padding to an 8 byte boundary is implicit to every message. Arbitrary bytes can be appended to ensure the alignment. Payload Length A 32 bit field indicating the length of the data in the payload. It is stored just before the payload to allow more efficient decoding in scripting languages Payload The payload of the message. It is 8 byte aligned for better memory access (ie a double can extracted directly out of the payload field) META AND STRUCTURED DATA All message ids of 0 are designated "Meta Data". This means the payload is encoded either in a JSON array or object or as a MessagePack structure This gives the fast encoding/decoding of simple time series values and the ability to have arbitrarily complex data when required Decoding of meta data automatically picks MessagePack or JSON as required, as long as the encoded values are are map or array types. It is recommended that general structured data in other message ids also either JSON or MessagePack also. NAMED IDs Static IDs are simple for small closed systems. However for larger system, using dynamic ids allows scoping. The mapping between names and ids is automatically applied when using a name space. Encoding a named id for the first time will in insert a entry in the local encoding side table. It will also inject a message with the dynamic id and payload of the name into the stream. This will be the first time this id is seen, and is a marker to update the decoding end of the system. Messages with id "0" are never subject to named id lookup. A message with id 0 and no payload, de-registers all (clears) the name space For a bidirectional link, as an example, 4 name spaces are actually used. The encoding end of each direction is the master in that direction. The ids likely don't match, but they don't need to. The decoding end of each direction is shadow/slave copy of the encoding table. Over a reliable transport, these tables will always be in sync with the master from the encoding end. FASTPACK FORMAT SUMMARY time(double float) # 8 byte aligned id(32) # uint32 len(32) # uint32 payload bytes # 8 byte aligned padding (as required) The FastPack format consists of a single type of time indexed binary record. The semantics of the message is application specific, and is bound to the ID field in every message. Finally the message payload is opaque data , with the entire message padded to a multiples of 8 bytes. All multi byte fields are in little endian byte order "time" is the absolute time of the sample or the difference in time from the current message to the previous message in the same stream. The exact meaning of the time is as per the definition messages. It is a double float to allow web browsers to utilise high resolution time, as they do not support 64bit integers. "id" is is the channel id within the file/stream. It relates to a definition file. 0 indicates a meta data point which is JSON or other structured data, which alters the processing of the file. Optionally a namespace can be used to provide dynamic ID generation. The ids are mapped from a name/label/topic/ to an integer. Additional mapping messages are inserted into the stream to facilitate this mapping at both ends. "len" is the length of the payload. If the length is larger than 2^32 then it must be fragmented at the 'application level'. "payload" is the data. "padding" Every record is padded to an 8 byte bounadary, with nulls, if nessicary API Usage Encoding and Decoding encode_fastpack encode_fastpack $buf, $inputs, $limit, $namespace Encodes and array ref of an array refs "[time, ID, payload]" in to the buffer $buf. $buf is aliased internally, and not copied. All need encoded messages are appended to the buffer. If "limit" is supplied, and less then the length of the $input array, only this number of inputs will be consumed. Inputs consumed are spliced out of the input array to allow the same array to be appended to externally If $namespace is provided, all messages are encoded assuming the id is name and dynamically allocates an ID to the name space. Note $limit must be provided (even if undefended) to use this argument. Namespace if prevented from using 0, "0", or "undef" as names. Messages with these names issue a warning. If a $namespace is utilised, the ID/name of the message can be any string. It is mapped to an integer code. If the message is the first one to use the ID, an extra message mapping the integer to the name (id becomes the integer value, payload becomes the name), in inserted into the output. If the message has and ID of "0", and a payload with no length, this resets the mappings in the namespace and is output as normal decode_fastpack decode_fastpack $buf,$output, $limit, $namespace Decodes FastPack messages from $buf, consuming it as it progresses. $buf is aliases so new messages can be added to it externally. $output is a reference to an array to store the decoded messages. The messages are decoded into "[time, id, payload]". If $limit is provided, this is the maximum number of messages to decode during a single call. If not provided or undef, 4096 is the default. $namespace if provided, int enables named ids. Decoded messages have the id mapped to a name stored in the names space. If its the id has not been encountered before, it uses the payload as the name to update the internal mapping. This message is not sent to the output, as it is intended to update the mapping only. If the message has and ID of "0", and a payload with no length, this resets the mappings in the namespace and is not forward past the decoder Namspaces create_namespace create_namespace Returns a name space structure for named ids. Separate name spaces structure are needed for encoding and decoding ends, even withing the same program. id_for_name id_for_name $namespace, $name Returns the integer id in $namespace for $name. Useful for testing and optimisation when multiple of the same messages are being encoded. name_for_id name_for_id $namespace, $id Returns the name id in $namespace for $id. Useful for testing and optimisation when multiple of the same messages are being encoded. AUTHOR Ruben Westerberg, REPOSITORTY and BUGS Please report any bugs via git hub: COPYRIGHT AND LICENSE Copyright (C) 2025 by Ruben Westerberg Licensed under MIT DISCLAIMER OF WARRANTIES THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.