prometheus/pkg/textparse/parse.go

110 lines
2.2 KiB
Go

//go:generate go get github.com/cznic/golex
//go:generate golex -o=lex.l.go lex.l
// Package textparse contains an efficient parser for the Prometheus text format.
package textparse
import (
"errors"
"io"
"sort"
"unsafe"
"github.com/prometheus/prometheus/pkg/labels"
)
type lexer struct {
b []byte
i int
vstart int
err error
val float64
offsets []int
mstart, mend int
}
const eof = 0
func (l *lexer) next() byte {
l.i++
if l.i >= len(l.b) {
l.err = io.EOF
return eof
}
c := l.b[l.i]
return c
}
func (l *lexer) Error(es string) {
l.err = errors.New(es)
}
// Parser parses samples from a byte slice of samples in the official
// Prometheus text exposition format.
type Parser struct {
l *lexer
err error
val float64
}
// New returns a new parser of the byte slice.
func New(b []byte) *Parser {
return &Parser{l: &lexer{b: b}}
}
// Next advances the parser to the next sample. It returns false if no
// more samples were read or an error occurred.
func (p *Parser) Next() bool {
switch p.l.Lex() {
case 0, -1:
return false
case 1:
return true
}
panic("unexpected")
}
// At returns the bytes of the metric, the timestamp if set, and the value
// of the current sample.
func (p *Parser) At() ([]byte, *int64, float64) {
return p.l.b[p.l.mstart:p.l.mend], nil, p.l.val
}
// Err returns the current error.
func (p *Parser) Err() error {
if p.err != nil {
return p.err
}
if p.l.err == io.EOF {
return nil
}
return p.l.err
}
// Metric writes the labels of the current sample into the passed labels.
func (p *Parser) Metric(l *labels.Labels) {
// Allocate the full immutable string immediately, so we just
// have to create references on it below.
s := string(p.l.b[p.l.mstart:p.l.mend])
*l = append(*l, labels.Label{
Name: labels.MetricName,
Value: s[:p.l.offsets[0]-p.l.mstart],
})
for i := 1; i < len(p.l.offsets); i += 3 {
a := p.l.offsets[i] - p.l.mstart
b := p.l.offsets[i+1] - p.l.mstart
c := p.l.offsets[i+2] - p.l.mstart
*l = append(*l, labels.Label{Name: s[a:b], Value: s[b+2 : c]})
}
sort.Sort((*l)[1:])
}
func yoloString(b []byte) string {
return *((*string)(unsafe.Pointer(&b)))
}