/
scanner.go
180 lines (150 loc) · 3.34 KB
/
scanner.go
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package shapefile
import (
"fmt"
"io"
"sync"
"github.com/mercatormaps/go-shapefile/dbf"
"github.com/mercatormaps/go-shapefile/dbf/dbase5"
"github.com/mercatormaps/go-shapefile/shp"
"github.com/pkg/errors"
)
type Scanner struct {
shp *shp.Scanner
dbf *dbf.Scanner
opts options
infoOnce sync.Once
info Info
scanOnce sync.Once
recordsCh chan *Record
errOnce sync.Once
err error
}
type Info struct {
BoundingBox shp.BoundingBox
NumRecords uint32
ShapeType shp.ShapeType
Fields FieldDescList
}
type FieldDescList []FieldDesc
func (l FieldDescList) Exists(name string) bool {
for _, f := range l {
if f.Name() == name {
return true
}
}
return false
}
type FieldDesc interface {
Name() string
}
func NewScanner(shpR, dbfR io.Reader, opts ...Option) *Scanner {
s := &Scanner{
dbf: dbf.NewScanner(dbfR),
recordsCh: make(chan *Record),
}
for _, opt := range opts {
opt(&s.opts)
}
s.shp = shp.NewScanner(shpR, s.opts.shp...)
return s
}
func (s *Scanner) AddOptions(opts ...Option) {
for _, opt := range opts {
opt(&s.opts)
}
s.shp.AddOptions(s.opts.shp...)
}
func (s *Scanner) Info() (*Info, error) {
var err error
s.infoOnce.Do(func() {
var shpHeader *shp.Header
if shpHeader, err = s.shp.Header(); err != nil {
err = errors.Wrap(err, "failed to parse shp header")
return
}
var dbfHeader dbf.Header
if dbfHeader, err = s.dbf.Header(); err != nil {
err = errors.Wrap(err, "failed to parse dbf header")
return
}
var fields []FieldDesc
switch h := dbfHeader.(type) {
case *dbase5.Header:
fields = make([]FieldDesc, len(h.Fields))
for i, f := range h.Fields {
fields[i] = f
}
default:
err = fmt.Errorf("unrecognized dbf header")
return
}
s.info = Info{
BoundingBox: shpHeader.BoundingBox,
NumRecords: dbfHeader.NumRecords(),
ShapeType: shpHeader.ShapeType,
Fields: fields,
}
})
return &s.info, err
}
func (s *Scanner) Scan() error {
info, err := s.Info()
if err != nil {
return err
}
s.scanOnce.Do(func() {
if err = s.shp.Scan(); err != nil {
return
} else if err = s.dbf.Scan(s.opts.dbf...); err != nil {
return
}
go func() {
defer func() {
if err := s.shp.Err(); err != nil {
s.setErr(errors.Wrap(err, "error in shp file"))
} else if err = s.dbf.Err(); err != nil {
s.setErr(errors.Wrap(err, "error in dbf file"))
}
close(s.recordsCh)
}()
for i := uint32(0); i < info.NumRecords; i++ {
shape := s.shp.Shape()
if err := s.shp.Err(); err != nil {
s.setErr(errors.Wrap(err, "error in shp file"))
return
} else if shape == nil {
s.setErr(fmt.Errorf("failed to read shape; expecting %d but have read %d", info.NumRecords, i+1))
return
}
attr := s.dbf.Record()
if err = s.dbf.Err(); err != nil {
s.setErr(errors.Wrap(err, "error in dbf file"))
return
} else if attr == nil {
s.setErr(fmt.Errorf("failed to read attributes; expecting %d but have read %d", info.NumRecords, i+1))
return
}
s.recordsCh <- &Record{
Shape: shape,
Attributes: attr,
}
}
}()
})
return err
}
func (s *Scanner) Record() *Record {
rec, ok := <-s.recordsCh
if !ok {
return nil
}
return rec
}
func (s *Scanner) Err() error {
return s.err
}
func (s *Scanner) setErr(err error) {
s.errOnce.Do(func() {
s.err = err
})
}