table.go RawHistoryFolder

1package linuxdmabuf
2
3import (
4	"encoding/binary"
5	"fmt"
6	"io"
7
8	"github.com/bnema/wlturbo/wl"
9	"golang.org/x/sys/unix"
10)
11
12// FormatEntry is one 16-byte format-table record. Padding is ignored.
13type FormatEntry struct {
14	Format   uint32
15	Modifier uint64
16}
17
18// ReadFormatTable consumes an owned format_table descriptor, even on error.
19// It reads a bounded snapshot with pread rather than mapping compositor-owned
20// memory, avoiding SIGBUS if the backing file is unexpectedly truncated.
21func ReadFormatTable(fd *wl.OwnedFD, size uint32) ([]FormatEntry, error) {
22	if fd == nil {
23		return nil, fmt.Errorf("missing format table descriptor")
24	}
25	n, err := fd.Take()
26	if err != nil {
27		return nil, err
28	}
29	defer unix.Close(n)
30	if size%16 != 0 || size > 16<<20 {
31		return nil, fmt.Errorf("invalid format table size %d", size)
32	}
33	b := make([]byte, size)
34	for off := 0; off < len(b); {
35		read, e := unix.Pread(n, b[off:], int64(off))
36		off += read
37		if e == unix.EINTR {
38			continue
39		}
40		if e != nil {
41			return nil, e
42		}
43		if read == 0 {
44			return nil, io.ErrUnexpectedEOF
45		}
46	}
47	entries := make([]FormatEntry, size/16)
48	for i := range entries {
49		off := i * 16
50		entries[i] = FormatEntry{binary.NativeEndian.Uint32(b[off:]), binary.NativeEndian.Uint64(b[off+8:])}
51	}
52	return entries, nil
53}
54
55// TrancheIndices decodes the uint16 indices into a format table.
56func TrancheIndices(data []byte, count int) ([]uint16, error) {
57	if len(data)%2 != 0 {
58		return nil, fmt.Errorf("odd tranche indices length")
59	}
60	indices := make([]uint16, len(data)/2)
61	for i := range indices {
62		indices[i] = binary.NativeEndian.Uint16(data[i*2:])
63		if int(indices[i]) >= count {
64			return nil, fmt.Errorf("format table index %d out of range", indices[i])
65		}
66	}
67	return indices, nil
68}