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package packrev
import (
"bufio"
"errors"
"fmt"
"io"
"math"
"lindenii.org/go/furgit/internal/stickyio"
"lindenii.org/go/furgit/object/id"
)
// ErrInvalidPositions reports that
// positions supplied for a reverse index write
// are out of range or too numerous.
var ErrInvalidPositions = errors.New("internal/format/packrev: invalid positions")
// Write writes one pack reverse index to w.
//
// positions holds, for each object in pack offset order,
// the object's pack index position.
// packHash must be the pack's trailer hash;
// Write panics when its length does not match the object format.
func Write(w io.Writer, objectFormat id.ObjectFormat, positions []uint32, packHash []byte) error {
hashID, err := hashFunctionID(objectFormat)
if err != nil {
return err
}
if len(packHash) != objectFormat.Size() {
panic("internal/format/packrev: invalid pack hash length")
}
if len(positions) > math.MaxUint32 {
return fmt.Errorf("%w: too many positions", ErrInvalidPositions)
}
for _, position := range positions {
if uint64(position) >= uint64(len(positions)) {
return fmt.Errorf("%w: index position out of range", ErrInvalidPositions)
}
}
hashImpl, err := objectFormat.New()
if err != nil {
return fmt.Errorf("internal/format/packrev: %w", err)
}
bw := bufio.NewWriter(io.MultiWriter(w, hashImpl))
sw := stickyio.New(bw)
sw.PutUint32(signature)
sw.PutUint32(version)
sw.PutUint32(hashID)
for _, position := range positions {
sw.PutUint32(position)
}
sw.Put(packHash)
err = sw.Err()
if err != nil {
return fmt.Errorf("internal/format/packrev: %w", err)
}
err = bw.Flush()
if err != nil {
return fmt.Errorf("internal/format/packrev: %w", err)
}
_, err = w.Write(hashImpl.Sum(nil))
if err != nil {
return fmt.Errorf("internal/format/packrev: %w", err)
}
return nil
}
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