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sexp.go
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sexp.go
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// Copyright 2017 Google Inc. All Rights Reserved.
// This file is available under the Apache license.
package vm
import (
"fmt"
"strconv"
"strings"
"github.com/google/mtail/metrics"
)
// Sexp is for converting program syntax trees into typed s-expression for printing
type Sexp struct {
output string // Accumulator for the result
emitTypes bool
col int // column to indent current line to
line string
}
func (s *Sexp) indent() {
s.col += 2
}
func (s *Sexp) outdent() {
s.col -= 2
}
func (s *Sexp) prefix() (r string) {
for i := 0; i < s.col; i++ {
r += " "
}
return
}
func (s *Sexp) emit(str string) {
s.line += str
}
func (s *Sexp) newline() {
if s.line != "" {
s.output += s.prefix() + s.line
}
s.output += "\n"
s.line = ""
}
// VisitBefore implements the astNode Visitor interface.
func (s *Sexp) VisitBefore(n astNode) Visitor {
s.emit(fmt.Sprintf("( ;;%T ", n))
if s.emitTypes {
s.emit(fmt.Sprintf("<%s> ", n.Type()))
}
s.emit(fmt.Sprintf("@ %s", n.Pos()))
s.newline()
s.indent()
switch v := n.(type) {
case *patternFragmentDefNode:
s.emit("const ")
Walk(s, v.id)
s.emit(" ")
case *patternConstNode:
s.emit(fmt.Sprintf("%q", v.pattern))
case *binaryExprNode:
switch v.op {
case LT:
s.emit("<")
case GT:
s.emit(">")
case LE:
s.emit("<=")
case GE:
s.emit(">=")
case EQ:
s.emit("==")
case NE:
s.emit("!=")
case SHL:
s.emit("<<")
case SHR:
s.emit(">>")
case BITAND:
s.emit("&")
case BITOR:
s.emit("|")
case XOR:
s.emit("^")
case NOT:
s.emit("~")
case AND:
s.emit("&&")
case OR:
s.emit("||")
case PLUS:
s.emit("+")
case MINUS:
s.emit("-")
case MUL:
s.emit("*")
case DIV:
s.emit("/")
case POW:
s.emit("**")
case ASSIGN:
s.emit("=")
case MOD:
s.emit("%")
case CONCAT:
s.emit("++")
case MATCH:
s.emit("=~")
case NOT_MATCH:
s.emit("!~")
default:
s.emit(fmt.Sprintf("Unexpected op: %v", v.op))
}
s.newline()
s.indent()
case *idNode:
s.emit("\"" + v.name + "\"")
case *caprefNode:
s.emit("\"" + v.name + "\"")
case *builtinNode:
s.emit("\"" + v.name + "\"")
s.newline()
case *declNode:
switch v.kind {
case metrics.Counter:
s.emit("counter ")
case metrics.Gauge:
s.emit("gauge ")
case metrics.Timer:
s.emit("timer ")
case metrics.Text:
s.emit("text ")
}
s.emit(v.name)
if len(v.keys) > 0 {
s.emit(" (")
s.emit(strings.Join(v.keys, " "))
s.emit(")")
}
case *unaryExprNode:
switch v.op {
case INC:
s.emit("++")
case NOT:
s.emit("~")
}
case *stringConstNode:
s.emit("\"" + v.text + "\"")
case *intConstNode:
s.emit(strconv.FormatInt(v.i, 10))
case *floatConstNode:
s.emit(strconv.FormatFloat(v.f, 'g', -1, 64))
case *nextNode:
s.emit("next")
case *otherwiseNode:
s.emit("otherwise")
case *delNode:
s.emit("del")
case *convNode:
s.emit("conv")
case *errorNode:
s.emit(fmt.Sprintf("error %q", v.spelling))
case *indexedExprNode, *stmtlistNode, *exprlistNode, *condNode, *decoDefNode, *decoNode, *patternExprNode: // normal walk
default:
panic(fmt.Sprintf("sexp found undefined type %T", n))
}
return s
}
// VisitAfter implements the astNode Visitor interface.
func (s *Sexp) VisitAfter(node astNode) {
switch node.(type) {
case *binaryExprNode:
s.outdent()
}
s.outdent()
s.emit(")")
s.newline()
}
// Dump begins the dumping of the syntax tree, returning the s-expression as a single string
func (s *Sexp) Dump(n astNode) string {
Walk(s, n)
return s.output
}