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Analysis

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Robert L. Bocchino Jr. edited this page Apr 18, 2024 · 31 revisions

This page describes the algorithms and data structures for performing analysis on FPP source models.

Data Structures

  • Abstract Syntax Tree (AST): The structure representing the abstract source syntax of an input model. The AST consists of nodes arranged in a tree with a parent-child relationship.

  • Analysis Data Structure: Defined here.

  • AST Node: An AST node represents an element of the source syntax. Each AST node has a unique integer identifier.

  • Command: An FPP command specifier.

  • Component: An FPP component, consisting of the following:

    1. A map from port names to port instances.

    2. A map from special port kinds to special port instances.

    3. A map from event identifiers to events.

    4. A map from command opcodes to commands.

    5. A map from parameter identifiers to parameters.

    6. A map from telemetry channel identifiers to telemetry channels.

    7. A map from container identifiers to containers.

    8. A map from record identifiers to records.

  • Component Instance: An FPP component instance. Contains a map from execution phases to init specifiers.

  • Connection: An FPP connection consisting of an output port instance, an optional output port number, an input port instance, and an optional input port number.

  • Connection graph pattern: An FPP connection graph pattern consisting of a pattern kind, a source instance, and a list of target instances.

  • Container: An FPP specifier for a data product container.

  • Dictionary Data Structure: Structure representing the dictionary produced for an FPP topology, consisting of:

    1. The set of type symbols used in the topology

    2. A map from resolved identifiers to commands

    3. A map from resolved identifiers to telemetry channels

    4. A map from resolved identifiers to events

    5. A map from resolved identifiers to parameters

    6. A map from resolved identifiers to records

    7. A map from resolved identifiers to containers

  • Event: An FPP specifier for an event report.

  • Expression: A syntactic expression. Expressions with identical form (e.g., two instances of the literal value 3) appearing at distinct nodes in the AST count as distinct expressions.

  • File: One of (a) an absolute path on the system where the analysis occurs; or (b) a special system file such as stdin or stdout.

  • Init specifier: An FPP init specifier.

  • Internal port: An internal port used in a component definition.

  • Location: A file and line number indicating the location of an AST node.

  • Location map: A map from AST nodes to their locations.

  • Name: A name, either qualified or unqualified. Names are not associated with nodes in the AST. For example, there is only one name a.b.c.

  • Name-Symbol Map: A local mapping of unqualified names to symbols. For any name-symbol map s and name n, if the mapping s[n] already exists, then it is an error to attempt to add a new mapping for n.

  • Nested Scope: A stack of scopes that represents the nesting of scopes inside each other. Scopes are pushed on the stack (starting with the global scope) when moving inwards in the nesting, and popped off the stack when returning outwards. New mappings of names to symbols are added to the innermost scope. Lookup of names n starts with the innermost scope S, moving to the next level up only if there is no entry for n in S, and finally giving up with an error if there is no entry for n at the outermost scope.

  • Parameter: An FPP ground parameter specifier.

  • Port: An FPP port definition.

  • Port Instance: A instance of a port definition used in a component definition. A port instance can be (1) a general instance of a port definition or (2) a special port instance or (3) an instance of an internal port.

  • Qualified Identifier: A qualified identifier appearing in the source syntax. A qualified identifier is either an unqualified name (e.g., a) or a qualified identifier followed by an unqualified name (e.g., a.b). A qualified identifier represents a qualified name. Qualified identifiers representing the same qualified name (e.g., the name a.b.c) and appearing at distinct nodes in the AST count as distinct qualified identifiers.

  • Record: An FPP specifier for a data product record.

  • Scope: A collection of name-symbol maps that represents a single flat scope (the global scope or a brace-delimited scope). Within each scope, there is one name-symbol map for each name group (values, types, etc.).

  • Symbol: A data structure that represents a definition. There is one kind of symbol for each kind of definition. A module symbol for a module M stores the first AST node encountered that adds definitions to M. A non-module symbol stores the unique AST node where the definition occurs.

  • Telemetry Channel: An FPP telemetry channel specifier.

  • Topology: An FPP topology, consisting of the following:

    1. A set of topology symbols representing the directly imported topology definitions.

    2. A set of topology symbols representing the transitively imported topology definitions.

    3. A set of component instances. Each instance may be either public or private for this topology.

    4. A set of connection graph patterns.

    5. A map from connection graph names to sets of connections.

    6. A map from connection graph names to sets of locally defined (i.e., not imported) connections.

    7. A map from ports to their output connections.

    8. A map from ports to their input connections.

    9. A map from connections to their from port numbers.

    10. A map from connections to their to port numbers.

    11. The set of unconnected port instances.

  • Type Name: A syntactic type name. A type name is associated with a node in the AST, so two different type names can refer to the same type. For example, if the keyword U32 appears at multiple nodes in the AST, then there are multiple type names that all refer to the same type U32.

  • Type: An FPP type. Types include internal types such as Integer. Types are not associated with nodes in the AST. For example, there is only one type U32. Multiple type names can refer to the same type. Array types have resolved constants for their size expressions.

  • Use-Def Matching: A data structure that matches the use of a symbol with the symbol it uses. A use-def matching stores an AST node identifier (the use), a qualified name (the qualified name appearing in the use), and a symbol (the definition that the use refers to).

  • Value: An FPP value.

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