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reader.go
163 lines (144 loc) · 3.52 KB
/
reader.go
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package pixi
import (
"encoding/binary"
"io"
"strconv"
)
func ReadPixi(r io.ReadSeeker) (Pixi, error) {
buf := make([]byte, 4)
// check file type
_, err := r.Read(buf)
if err != nil {
return Pixi{}, err
}
fileType := string(buf)
if fileType != PixiFileType {
return Pixi{}, FormatError("pixi file marker not found at start of file")
}
// check file version
_, err = r.Read(buf)
if err != nil {
return Pixi{}, err
}
version, err := strconv.ParseInt(string(buf), 10, 32)
if err != nil {
return Pixi{}, err
}
if version > PixiVersion {
return Pixi{}, FormatError("reader does not support this version of pixi file")
}
offset := (&Pixi{}).FirstLayerOffset()
layers := []*DiskLayer{}
for offset != 0 {
layer, err := ReadLayer(r)
if err != nil {
return Pixi{}, err
}
layers = append(layers, &layer)
offset = layer.NextLayerStart
_, err = r.Seek(offset, io.SeekStart)
if err != nil {
return Pixi{}, err
}
}
summary := Pixi{
Layers: layers,
}
return summary, nil
}
func ReadLayer(r io.Reader) (DiskLayer, error) {
summary := DiskLayer{}
var dimCount, fieldCount, configuration, nameLen uint32
err := binary.Read(r, binary.BigEndian, &dimCount)
if err != nil {
return summary, err
}
err = binary.Read(r, binary.BigEndian, &fieldCount)
if err != nil {
return summary, err
}
err = binary.Read(r, binary.BigEndian, &configuration)
if err != nil {
return summary, err
}
summary.Separated = configuration != 0
err = binary.Read(r, binary.BigEndian, &summary.Compression)
if err != nil {
return summary, err
}
// read layer name
err = binary.Read(r, binary.BigEndian, &nameLen)
if err != nil {
return summary, err
}
name := make([]byte, nameLen)
_, err = r.Read(name)
if err != nil {
return summary, err
}
summary.Name = string(name)
// read dimension sizes
dimSizes := make([]int64, dimCount)
err = binary.Read(r, binary.BigEndian, dimSizes)
if err != nil {
return summary, err
}
// read dimension tile sizes
tileSizes := make([]int64, dimCount)
err = binary.Read(r, binary.BigEndian, tileSizes)
if err != nil {
return summary, err
}
dims := make([]Dimension, dimCount)
for i := 0; i < int(dimCount); i++ {
dims[i] = Dimension{Size: int(dimSizes[i]), TileSize: int(tileSizes[i])}
}
summary.Dimensions = dims
// read field types
fieldTypes := make([]FieldType, fieldCount)
err = binary.Read(r, binary.BigEndian, fieldTypes)
if err != nil {
return summary, err
}
// read field names
fieldNames := make([]string, fieldCount)
for i := 0; i < int(fieldCount); i++ {
var nameLen uint16
err := binary.Read(r, binary.BigEndian, &nameLen)
if err != nil {
return summary, err
}
buf := make([]byte, nameLen)
_, err = r.Read(buf)
if err != nil {
return summary, err
}
fieldNames[i] = string(buf)
}
fields := make([]Field, fieldCount)
for i := 0; i < int(fieldCount); i++ {
fields[i] = Field{Name: fieldNames[i], Type: fieldTypes[i]}
}
summary.Fields = fields
// read tile bytes, offsets, and next layer start
tiles := summary.DiskTiles()
tileBytes := make([]int64, tiles)
err = binary.Read(r, binary.BigEndian, tileBytes)
if err != nil {
return summary, err
}
tileOffsets := make([]int64, tiles)
err = binary.Read(r, binary.BigEndian, tileOffsets)
if err != nil {
return summary, err
}
var nextLayerStart int64
err = binary.Read(r, binary.BigEndian, &nextLayerStart)
if err != nil {
return summary, err
}
summary.TileBytes = tileBytes
summary.TileOffsets = tileOffsets
summary.NextLayerStart = nextLayerStart
return summary, nil
}