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package read
import (
"os"
"syscall"
"codeberg.org/lindenii/furgit/commitgraph"
"codeberg.org/lindenii/furgit/internal/intconv"
objectid "codeberg.org/lindenii/furgit/object/id"
)
func openLayer(root *os.Root, relPath string, algo objectid.Algorithm) (*layer, error) {
file, err := root.Open(relPath)
if err != nil {
return nil, err
}
info, err := file.Stat()
if err != nil {
_ = file.Close()
return nil, err
}
size := info.Size()
if size < int64(commitgraph.HeaderSize+commitgraph.FanoutSize+algo.Size()) {
_ = file.Close()
return nil, &MalformedError{Path: relPath, Reason: "file too short"}
}
mapLen, err := intconv.Int64ToUint64(size)
if err != nil {
_ = file.Close()
return nil, err
}
mapLenInt, err := intconv.Uint64ToInt(mapLen)
if err != nil {
_ = file.Close()
return nil, err
}
fd, err := intconv.UintptrToInt(file.Fd())
if err != nil {
_ = file.Close()
return nil, err
}
data, err := syscall.Mmap(fd, 0, mapLenInt, syscall.PROT_READ, syscall.MAP_PRIVATE)
if err != nil {
_ = file.Close()
return nil, err
}
out := &layer{
path: relPath,
file: file,
data: data,
}
parseErr := parseLayer(out, algo)
if parseErr != nil {
_ = out.close()
return nil, parseErr
}
verifyErr := verifyTrailerHash(out.data, algo, relPath)
if verifyErr != nil {
_ = out.close()
return nil, verifyErr
}
return out, nil
}
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