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stl.go
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stl.go
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package mesh
import (
"encoding/binary"
"errors"
"os"
"github.com/ungerik/go3d/vec3"
)
const (
uint16Size = 2
uint32Size = 4
float32Size = 4
)
var (
errFormat = errors.New("wrong file format")
errSize = errors.New("reported face count does not match actual")
)
func IsFormat(err error) bool {
return err == errFormat
}
func IsSize(err error) bool {
return err == errSize
}
const (
asciiId = "solid"
headerLen = 80
)
// StlFile reads from an existing .stl file or creates a new one if it doesn't exist.
type StlFile struct {
path string
numTriangles int
}
func NewStlFile(filepath string) (*StlFile, error) {
stlFile := StlFile{path: filepath}
file, err := os.Open(filepath)
if os.IsNotExist(err) {
return &stlFile, nil
}
if err != nil {
return nil, err
}
defer file.Close()
stlFileStat, err := file.Stat()
if err != nil {
return nil, err
}
if stlFileStat.Size() == 0 {
return &stlFile, nil
}
if binary, err := stlFile.isBinary(file); err != nil {
return nil, err
} else if !binary {
return nil, errFormat
}
if err = stlFile.readTriangleCount(file); err != nil {
return nil, err
}
return &stlFile, nil
}
func (this *StlFile) isBinary(stlFile *os.File) (result bool, err error) {
if _, err = stlFile.Seek(0, 0); err != nil {
return
}
asciiText := make([]byte, len(asciiId))
if _, err = stlFile.Read(asciiText); err != nil {
return
}
return string(asciiText) != asciiId, nil
}
func (this *StlFile) readTriangleCount(stlFile *os.File) (err error) {
_, err = stlFile.Seek(headerLen, 0)
if err != nil {
return
}
var numTriangles uint32
err = binary.Read(stlFile, binary.LittleEndian, &numTriangles)
if err != nil {
return
}
this.numTriangles = int(numTriangles)
var meshSize int64 = int64(this.numTriangles) * (3*4*float32Size + uint16Size)
var fileSize int64 = headerLen + uint32Size + meshSize
stats, err := stlFile.Stat()
if err != nil {
return
}
if stats.Size() != fileSize {
return errSize
}
return
}
func (this *StlFile) read() <-chan Triangle {
triChan := make(chan Triangle)
go func() {
file, err := os.Open(this.path)
if err != nil {
panic(err)
}
defer file.Close()
file.Seek(headerLen+uint32Size, 0)
var incomingTri stlTriangle
var currTriangle int
for ; currTriangle < this.numTriangles; currTriangle++ {
binary.Read(file, binary.LittleEndian, &incomingTri)
triChan <- incomingTri.Tri
}
close(triChan)
}()
return triChan
}
type stlTriangle struct {
_ vec3.T // Normal
Tri Triangle
_ uint16 // Extra info
}
func (this *StlFile) ConvertFrom(mesh Mesh) {
this.numTriangles = mesh.NumTriangles()
err := os.Remove(this.path)
if err != nil && !os.IsNotExist(err) {
panic(err)
}
file, err := os.Create(this.path)
if err != nil {
panic(err)
}
defer file.Close()
header := make([]byte, headerLen)
for i := range header {
header[i] = 0x20
}
_, err = file.Write(header)
if err != nil {
panic(err)
}
err = binary.Write(file, binary.LittleEndian, uint32(this.numTriangles))
if err != nil {
panic(err)
}
var stlTri stlTriangle
for tri := range mesh.read() {
stlTri.Tri = tri
binary.Write(file, binary.LittleEndian, stlTri)
}
}
func (this *StlFile) NumTriangles() int {
return this.numTriangles
}