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write_optional.go
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write_optional.go
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package dremel
import (
"bytes"
"fmt"
"log"
"strings"
"text/template"
"github.com/parsyl/parquet/internal/fields"
)
func init() {
funcs := template.FuncMap{
"removeStar": func(s string) string {
return strings.Replace(s, "*", "", 1)
},
"plusOne": func(i int) int { return i + 1 },
"notNil": func(x *ifElse) bool { return x != nil },
}
var err error
writeTpl, err = template.New("output").Funcs(funcs).Parse(`func write{{.FuncName}}(x *{{.Field.Type}}, vals []{{removeStar .Field.TypeName}}, defs, reps []uint8) (int, int) {
def := defs[0]
switch def { {{range $i, $case := .Cases}}{{$def:=plusOne $i}}
case {{$def}}:
{{$defIndex := $.Field.DefIndex $def}}{{if $case.UseIf}}{{template "ifelse" $case}}{{else}}{{$case.Val}}{{end}}{{if eq $def $.MaxDef}}
return 1, 1{{end}}{{end}}
}
return 0, 1
}`)
if err != nil {
log.Fatal(err)
}
ifelseStmt = `{{define "ifelse"}}if {{.If.Cond}} {
{{.If.Val}}
} {{range $else := .ElseIf}} else if {{$else.Cond}} {
{{$else.Val}}
}{{end}} {{if notNil .Else}} else {
{{.Else.Val}}
} {{end}}{{end}}`
writeTpl, err = writeTpl.Parse(ifelseStmt)
if err != nil {
log.Fatal(err)
}
}
var (
writeTpl *template.Template
ifelseStmt string
)
type writeInput struct {
fields.Field
Cases []ifElses
FuncName string
}
type ifElse struct {
Cond string
Val string
}
type ifElses struct {
If ifElse
ElseIf []ifElse
Else *ifElse
Val *string
}
func (i ifElses) UseIf() bool {
return i.Val == nil
}
func writeOptional(i int, flds []fields.Field) string {
f := flds[i]
s := fields.Seen(i, flds)
f.Seen = s
wi := writeInput{
Field: f,
FuncName: strings.Join(f.FieldNames, ""),
Cases: writeOptionalCases(f, s),
}
var buf bytes.Buffer
err := writeTpl.Execute(&buf, wi)
if err != nil {
log.Fatal(err) //TODO: return error
}
return string(buf.Bytes())
}
func writeOptionalCases(f fields.Field, seen fields.RepetitionTypes) []ifElses {
var out []ifElses
for def := 1; def <= defs(f); def++ {
if useIfElse(def, 0, seen, f) {
out = append(out, ifelses(def, 0, f))
} else {
s := f.Init(def, 0)
out = append(out, ifElses{Val: &s})
}
}
return out
}
type ifElseCase struct {
f fields.Field
p fields.Field
}
// ifelses returns an if else block for the given definition and repetition level
func ifelses(def, rep int, orig fields.Field) ifElses {
opts := optionals(def, orig)
var cases ifElseCases
for _, o := range opts {
f := orig.Copy()
f.Seen = seens(o)
cases = append(cases, ifElseCase{f: f, p: f.Parent(o + 1)})
}
return cases.ifElses(def, rep, int(orig.MaxDef()))
}
func seens(i int) fields.RepetitionTypes {
out := make([]fields.RepetitionType, i)
for i := range out {
out[i] = fields.Repeated
}
return fields.RepetitionTypes(out)
}
type ifElseCases []ifElseCase
func (i ifElseCases) ifElses(def, rep, md int) ifElses {
out := ifElses{
If: ifElse{
Cond: fmt.Sprintf("x.%s == nil", strings.Join(i[0].p.FieldNames, ".")),
Val: i[0].f.Init(def, rep),
},
}
var leftovers []ifElseCase
if len(i) > 1 {
out.Else = &ifElse{
Val: i[len(i)-1].f.Init(def, rep),
}
if len(i) > 2 {
leftovers = i[1 : len(i)-1]
}
}
for _, iec := range leftovers {
out.ElseIf = append(out.ElseIf, ifElse{
Cond: fmt.Sprintf("x.%s == nil", strings.Join(iec.p.FieldNames, ".")),
Val: iec.f.Init(def, rep),
})
}
return out
}
// optionals returns a slice that contains the index of
// each optional field.
func optionals(def int, f fields.Field) []int {
var out []int
di := f.DefIndex(def)
seen := append(f.Seen[:0:0], f.Seen...)
if len(seen) > di+1 {
seen = seen[:di+1]
}
for i, rt := range f.RepetitionTypes[:di+1] {
if rt >= fields.Optional {
out = append(out, i)
}
if i > len(seen)-1 && rt >= fields.Optional {
break
}
}
return out
}