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Added support to load from memory #36

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Added support to load from memory #36

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c21aa8d
Added support to load from memory
racerxdl Mar 7, 2019
14fa0b3
Fixed missing comment on OpenFromMemory
racerxdl Mar 7, 2019
dc51776
Added Tests for OpenFromMemory
racerxdl Mar 7, 2019
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1 change: 1 addition & 0 deletions .gitignore
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
.idea
43 changes: 40 additions & 3 deletions reader.go
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package shp

import (
"bytes"
"encoding/binary"
"fmt"
"io"
Expand Down Expand Up @@ -30,6 +31,8 @@ type Reader struct {
dbfNumRecords int32
dbfHeaderLength int16
dbfRecordLength int16

memoryData *memoryShapeData
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I'm not happy with adding this member variable to the struct.

Do you need to have random access? If not, have you considered https://godoc.org/github.com/jonas-p/go-shp#SequentialReaderFromExt for opening the byte slices?

}

type readSeekCloser interface {
Expand All @@ -38,6 +41,25 @@ type readSeekCloser interface {
io.Closer
}

type byteSeekCloser struct {
bytes.Reader
}

func (bsc *byteSeekCloser) Close() error {
return nil
}

func newBytesReader(data []byte) *byteSeekCloser {
return &byteSeekCloser{
Reader: *bytes.NewReader(data),
}
}

type memoryShapeData struct {
shpFileData []byte
dbfFileData []byte
}

// Open opens a Shapefile for reading.
func Open(filename string) (*Reader, error) {
ext := filepath.Ext(filename)
Expand All @@ -53,6 +75,17 @@ func Open(filename string) (*Reader, error) {
return s, nil
}

func OpenFromMemory(shpFileData, dbfFileData []byte) (*Reader, error) {
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exported function OpenFromMemory should have comment or be unexported

mD := &memoryShapeData{
shpFileData: shpFileData,
dbfFileData: dbfFileData,
}

s := &Reader{filename: "", shp: newBytesReader(mD.shpFileData), memoryData: mD}
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I have doubts about this, as well. Effectively, you are adding references to mD twice to s. I understand that you want to preserve the dbf data so that openDbf has something to open later, but the proposed design will overcomplicate things.

s.readHeaders()
return s, nil
}

// BBox returns the bounding box of the shapefile.
func (r *Reader) BBox() Box {
return r.bbox
Expand Down Expand Up @@ -194,9 +227,13 @@ func (r *Reader) openDbf() (err error) {
return
}

r.dbf, err = os.Open(r.filename + ".dbf")
if err != nil {
return
if r.memoryData != nil {
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IMHO this is a bit of a code smell: Testing whether one of the members is holding data and then branching the logic from there.

r.dbf = newBytesReader(r.memoryData.dbfFileData)
} else {
r.dbf, err = os.Open(r.filename + ".dbf")
if err != nil {
return
}
}

// read header
Expand Down