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package rosa
import (
"encoding/binary"
"errors"
"fmt"
"io"
"os"
"runtime"
"runtime/debug"
"strconv"
"sync"
"syscall"
"unique"
"unsafe"
"hakurei.app/internal/pkg"
"hakurei.app/message"
)
// wordSize is the boundary which binary segments are always aligned to.
const wordSize = 8
// padSize returns the padding size for aligning sz.
func padSize[T int | int64](sz T) T {
return (wordSize - (sz)%wordSize) % wordSize
}
// WriteReport writes a report of all available [PArtifact] to w.
func WriteReport(msg message.Msg, w io.Writer, c *pkg.Cache) error {
var (
zero [wordSize]byte
buf [len(pkg.ID{}) + wordSize]byte
)
for i := range PresetEnd {
a := Std.Load(PArtifact(i))
if _, ok := a.(pkg.FileArtifact); ok {
msg.Verbosef("skipping file artifact %s", artifactsM[i].Name)
continue
}
id := c.Ident(a)
var f *os.File
if r, err := c.OpenStatus(a); err != nil {
if errors.Is(err, os.ErrNotExist) {
msg.Verbosef("artifact %s unavailable", artifactsM[i].Name)
continue
}
return err
} else {
f = r.(*os.File)
}
msg.Verbosef("writing artifact %s...", artifactsM[i].Name)
var sz int64
if fi, err := f.Stat(); err != nil {
_ = f.Close()
return err
} else {
sz = fi.Size()
}
*(*pkg.ID)(buf[:]) = id.Value()
binary.LittleEndian.PutUint64(buf[len(pkg.ID{}):], uint64(sz))
if _, err := w.Write(buf[:]); err != nil {
_ = f.Close()
return err
}
if n, err := io.Copy(w, f); err != nil {
_ = f.Close()
return err
} else if n != sz {
_ = f.Close()
return fmt.Errorf("strange status file copy: %d != %d", n, sz)
} else if err = f.Close(); err != nil {
return err
}
if psz := padSize(sz); psz > 0 {
if _, err := w.Write(zero[:psz]); err != nil {
return err
}
}
// existence of status implies cured artifact
var n int
if pathname, _, err := c.Cure(a); err != nil {
return err
} else if n, err = pkg.Flatten(
os.DirFS(pathname.String()), ".",
io.Discard,
); err != nil {
return err
}
binary.LittleEndian.PutUint64(buf[:], uint64(n))
if _, err := w.Write(buf[:wordSize]); err != nil {
return err
}
}
return nil
}
// Report provides efficient access to a report file populated by [WriteReport].
type Report struct {
// Underlying file, must not be exposed directly.
f *os.File
// Slice backed by f. Access must be prepared by HandleAccess.
data []byte
// Offsets into data for each identifier.
offsets map[unique.Handle[pkg.ID]]int
// Outcome of a call to Close.
closeErr error
// Synchronises calls to Close.
closeOnce sync.Once
}
// OpenReport opens a file populated by [WriteReport]
func OpenReport(pathname string) (rp *Report, err error) {
var r Report
if r.f, err = os.Open(pathname); err != nil {
return
}
defer func() {
if err != nil {
_ = r.f.Close()
if r.data != nil {
_ = syscall.Munmap(r.data)
}
}
}()
var fi os.FileInfo
if fi, err = r.f.Stat(); err != nil {
return
}
if r.data, err = syscall.Mmap(
int(r.f.Fd()),
0,
int(fi.Size()),
syscall.PROT_READ,
syscall.MAP_PRIVATE,
); err != nil {
return
}
defer r.HandleAccess(&err)()
var offset int
r.offsets = make(map[unique.Handle[pkg.ID]]int)
for offset < len(r.data) {
id := unique.Make((pkg.ID)(r.data[offset:]))
offset += len(pkg.ID{})
r.offsets[id] = offset
offset += int(binary.LittleEndian.Uint64(r.data[offset:])) + wordSize
offset += padSize(offset)
offset += wordSize
}
return &r, nil
}
// ReportIOError describes an I/O error while accessing a [Report].
type ReportIOError struct {
Offset int
Err error
}
// Unwrap returns the underlying runtime error.
func (e *ReportIOError) Unwrap() error { return e.Err }
// Error returns a description of the error offset.
func (e *ReportIOError) Error() string {
return "report I/O error at offset " + strconv.Itoa(e.Offset)
}
// HandleAccess prepares for accessing memory returned by a method of [Report]
// and returns a function that must be deferred by the caller.
func (r *Report) HandleAccess(errP *error) func() {
pof := debug.SetPanicOnFault(true)
return func() {
debug.SetPanicOnFault(pof)
v := recover()
if v == nil {
return
}
if err, ok := v.(error); !ok {
panic(v)
} else if *errP != nil {
return
} else {
*errP = err
}
var runtimeError interface {
Addr() uintptr
runtime.Error
}
if errors.As(*errP, &runtimeError) {
offset := int(runtimeError.Addr() - uintptr(unsafe.Pointer(unsafe.SliceData(r.data))))
// best effort for fragile uintptr
if offset >= 0 {
*errP = &ReportIOError{offset, *errP}
}
}
}
}
// ArtifactOf returns information of a [pkg.Artifact] corresponding to id.
func (r *Report) ArtifactOf(id unique.Handle[pkg.ID]) (status []byte, n int64) {
if offset, ok := r.offsets[id]; !ok {
n = -1
} else {
sz := int(binary.LittleEndian.Uint64(r.data[offset:]))
offset += wordSize
status = r.data[offset : offset+sz]
offset += sz + padSize(sz)
n = int64(binary.LittleEndian.Uint64(r.data[offset:]))
}
return
}
// Close closes the underlying file and releases all associated resources.
func (r *Report) Close() error {
r.closeOnce.Do(func() {
err := syscall.Munmap(r.data)
r.closeErr = errors.Join(err, r.f.Close())
})
return r.closeErr
}
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