parser

Documentation

Overview

Package parser implements the parse phase of the mtail program compilation. The parser itself is defined in parser.y, and goyacc generates the program code and token definitions. The parser fetches tokens from the lexer, which scans the input converting the program source into a token stream. The driver code wraps the generated parser and marshals the ast and errors back to the caller.

Two pretty-printers are used for debugging: the unparser, which converts an ast back into program text, and an approximation of an s-expression printer, which tries to model in indented text the structure of the ast.

Index

• Constants
• func Parse(name string, input io.Reader) (ast.Node, error)
• type Kind
  • func (k Kind) String() string
• type Lexer
  • func NewLexer(name string, input io.Reader) *Lexer
  • func (l *Lexer) NextToken() Token
• type Sexp
  • func (s *Sexp) Dump(n ast.Node) string
  • func (s *Sexp) VisitAfter(node ast.Node) ast.Node
  • func (s *Sexp) VisitBefore(n ast.Node) (ast.Visitor, ast.Node)
• type Token
  • func (t Token) String() string
• type Unparser
  • func (u *Unparser) Unparse(n ast.Node) string
  • func (u *Unparser) VisitAfter(n ast.Node) ast.Node
  • func (u *Unparser) VisitBefore(n ast.Node) (ast.Visitor, ast.Node)

Constants

const ADD_ASSIGN = 57396

const AFTER = 57352

const AND = 57394

const AS = 57353

const ASSIGN = 57397

const BITAND = 57390

const BITOR = 57392

const BUCKETS = 57363

const BUILTIN = 57364

const BY = 57354

const CAPREF = 57367

const CAPREF_NAMED = 57368

const COMMA = 57407

const CONCAT = 57398

const CONST = 57355

const COUNTER = 57347

const DEC = 57375

const DECO = 57370

const DEF = 57357

const DEL = 57358

const DIV = 57376

const DURATIONLITERAL = 57373

const ELSE = 57361

const EOF = 0

EOF is a marker for end of file. It has the same value as the goyacc internal Kind `$end`.

const EQ = 57388

const FLOATLITERAL = 57372

const GAUGE = 57348

const GE = 57387

const GT = 57385

const HIDDEN = 57356

const HISTOGRAM = 57351

const ID = 57369

const INC = 57374

const INTLITERAL = 57371

const INVALID = 57346

const LCURLY = 57401

const LE = 57386

const LPAREN = 57403

const LSQUARE = 57405

const LT = 57384

const MATCH = 57399

const MINUS = 57379

const MOD = 57377

const MUL = 57378

const NE = 57389

const NEXT = 57359

const NL = 57408

const NOT = 57393

const NOT_MATCH = 57400

const OR = 57395

const OTHERWISE = 57360

const PLUS = 57380

const POW = 57381

const RCURLY = 57402

const REGEX = 57365

const RPAREN = 57404

const RSQUARE = 57406

const SHL = 57382

const SHR = 57383

const STOP = 57362

const STRING = 57366

const TEXT = 57350

const TIMER = 57349

const XOR = 57391

Functions

func Parse

func Parse(name string, input io.Reader) (ast.Node, error)

Parse reads the program named name from the input, and if successful returns an ast.Node for the root of the AST, otherwise parser errors.

Types

type Kind

type Kind int

Kind enumerates the types of lexical tokens in a mtail program.

func (Kind) String

func (k Kind) String() string

String returns a readable name of the token Kind.

type Lexer

type Lexer struct {
	InRegex bool // Context aware flag from parser to say we're in a regex
	// contains filtered or unexported fields
}

A lexer holds the state of the scanner.

func NewLexer

func NewLexer(name string, input io.Reader) *Lexer

NewLexer creates a new scanner type that reads the input provided.

func (*Lexer) NextToken

func (l *Lexer) NextToken() Token

NextToken returns the next token in the input. When no token is available to be returned it executes the next action in the state machine.

type Sexp

type Sexp struct {
	EmitTypes bool
	// contains filtered or unexported fields
}

Sexp is for converting program syntax trees into typed s-expression for printing

func (*Sexp) Dump

func (s *Sexp) Dump(n ast.Node) string

Dump begins the dumping of the syntax tree, returning the s-expression as a single string

func (*Sexp) VisitAfter

func (s *Sexp) VisitAfter(node ast.Node) ast.Node

VisitAfter implements the astNode Visitor interface.

func (*Sexp) VisitBefore

func (s *Sexp) VisitBefore(n ast.Node) (ast.Visitor, ast.Node)

VisitBefore implements the astNode Visitor interface.

type Token

type Token struct {
	Kind     Kind
	Spelling string
	Pos      position.Position
}

Token describes a lexed Token from the input, containing its type, the original text of the Token, and its position in the input.

func (Token) String

func (t Token) String() string

String returns a printable form of a Token.

type Unparser

type Unparser struct {
	// contains filtered or unexported fields
}

Unparser is for converting program syntax trees back to program text.

func (*Unparser) Unparse

func (u *Unparser) Unparse(n ast.Node) string

Unparse begins the unparsing of the syntax tree, returning the program text as a single string.

func (*Unparser) VisitAfter

func (u *Unparser) VisitAfter(n ast.Node) ast.Node

VisitAfter implements the ast.Visitor interface.

func (*Unparser) VisitBefore

func (u *Unparser) VisitBefore(n ast.Node) (ast.Visitor, ast.Node)

VisitBefore implements the ast.Visitor interface.