/
carDriver.go
103 lines (88 loc) · 2.32 KB
/
carDriver.go
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package main
import (
"fmt"
"io"
"os"
"sync/atomic"
)
var carDriverCreator = driverCreator{
factory: newCarDriver,
help: carHelp,
maxCarSize: 1 << 42,
}
func carHelp(out io.Writer) {
fmt.Fprint(out, ` Positional:
- <PATH_FORMAT> defaults to "out.%d.car"
`)
}
func newCarDriver(input string) (driver, error) {
if input == "" {
input = "out.%d.car"
}
d := &carDriver{
pathFormat: input,
}
return d.send, nil
}
type carDriver struct {
pathFormat string
counter uint32
}
func (c *carDriver) send(headerBuffer []byte, car *os.File, carOffset int64) error {
n := atomic.AddUint32(&c.counter, 1)
outName := fmt.Sprintf(c.pathFormat, n)
outF, err := os.OpenFile(outName, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o600)
if err != nil {
outF.Close()
os.Remove(outName)
return fmt.Errorf("creating failed out file %q: %w", outName, err)
}
headerLen := int64(len(headerBuffer))
_, err = outF.Write(headerBuffer)
if err != nil {
outF.Close()
os.Remove(outName)
return fmt.Errorf("writing header to failed out file %q: %w", outName, err)
}
_, err = car.Seek(carOffset, io.SeekStart)
if err != nil {
outF.Close()
os.Remove(outName)
return fmt.Errorf("seeking car to failed out file %q: %w", outName, err)
}
if !noPad {
padCar := diskAssumedBlockSize - uint16(carOffset)%diskAssumedBlockSize
padHeader := (diskAssumedBlockSize - padCar - uint16(headerLen)) % diskAssumedBlockSize
if padHeader != 0 {
if padHeader < fakeBlockMinLength {
// we can't pad so little, pad to the next size
padHeader += diskAssumedBlockSize
}
_, err = outF.Write(createPadBlockHeader(padHeader))
if err != nil {
return fmt.Errorf("writing pad block to %q: %w", outName, err)
}
_, err = outF.Seek(headerLen+int64(padHeader), io.SeekStart)
if err != nil {
return fmt.Errorf("seeking after pad block to %q: %w", outName, err)
}
}
if padCar != 0 {
// Read only so little bytes to continue reading later alligned to the diskAssumedBlockSize
_, err = outF.ReadFrom(&io.LimitedReader{
R: car,
N: int64(padCar),
})
if err != nil {
return fmt.Errorf("precopying the pad car to %q: %w", outName, err)
}
}
}
_, err = outF.ReadFrom(car)
outF.Close()
if err != nil {
os.Remove(outName)
return fmt.Errorf("copying buffer to %q: %w", outName, err)
}
return nil
}