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bitio: Handle < 0 nbits

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Read/Write64 panic on < 0 bits
Readers return error
This commit is contained in:
Mattias Wadman 2021-09-29 11:51:07 +02:00
parent 723542aea2
commit 20021f48ec
3 changed files with 20 additions and 9 deletions
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18
pkg/bitio/bitio.go
View File

@ -8,6 +8,9 @@ import (
"io"
)
var ErrOffset = errors.New("invalid seek offset")
var ErrNegativeNBits = errors.New("negative number of bits")
type BitReaderAt interface {
ReadBitsAt(p []byte, nBits int, bitOff int64) (n int, err error)
}
@ -114,6 +117,10 @@ func BitsByteCount(nBits int64) int64 {
}
func readFull(p []byte, nBits int, bitOff int64, fn func(p []byte, nBits int, bitOff int64) (int, error)) (int, error) {
if nBits < 0 {
return 0, ErrNegativeNBits
}
readBitOffset := 0
for readBitOffset < nBits {
byteOffset := readBitOffset / 8
@ -180,7 +187,6 @@ func EndPos(rs BitSeeker) (int64, error) {
}
// Reader is a BitReadSeeker and BitReaderAt reading from a io.ReadSeeker
// TODO: private?
type Reader struct {
bitPos int64
rs io.ReadSeeker
@ -195,6 +201,10 @@ func NewReaderFromReadSeeker(rs io.ReadSeeker) *Reader {
}
func (r *Reader) ReadBitsAt(p []byte, nBits int, bitOffset int64) (int, error) {
if nBits < 0 {
return 0, ErrNegativeNBits
}
readBytePos := bitOffset / 8
readSkipBits := int(bitOffset % 8)
wantReadBits := readSkipBits + nBits
@ -311,8 +321,6 @@ func (r *SectionBitReader) ReadBits(p []byte, nBits int) (n int, err error) {
return rBits, err
}
var errOffset = errors.New("invalid seek offset")
func (r *SectionBitReader) SeekBits(bitOff int64, whence int) (int64, error) {
switch whence {
case io.SeekStart:
@ -325,7 +333,7 @@ func (r *SectionBitReader) SeekBits(bitOff int64, whence int) (int64, error) {
panic("unknown whence")
}
if bitOff < r.bitBase {
return 0, errOffset
return 0, ErrOffset
}
r.bitOff = bitOff
return bitOff - r.bitBase, nil
@ -411,7 +419,7 @@ func (m *MultiBitReader) SeekBits(bitOff int64, whence int) (int64, error) {
panic("unknown whence")
}
if p < 0 || p > end {
return 0, errOffset
return 0, ErrOffset
}
m.pos = p

8
pkg/bitio/rw64.go
View File

@ -8,8 +8,8 @@ import (
// Read64 read nBits bits large unsigned integer from buf starting from firstBit.
// Integer is read most significant bit first.
func Read64(buf []byte, firstBit int, nBits int) uint64 {
if nBits > 64 {
panic(fmt.Sprintf("only supports =< 64 bits (%d)", nBits))
if nBits < 0 || nBits > 64 {
panic(fmt.Sprintf("nBits must be 0-64 (%d)", nBits))
}
be := binary.BigEndian
@ -91,8 +91,8 @@ func Read64(buf []byte, firstBit int, nBits int) uint64 {
}
func Write64(v uint64, nBits int, buf []byte, firstBit int) {
if nBits > 64 {
panic(fmt.Sprintf("only supports =< 64 bits (%d)", nBits))
if nBits < 0 || nBits > 64 {
panic(fmt.Sprintf("nBits must be 0-64 (%d)", nBits))
}
be := binary.BigEndian

3
pkg/decode/numbers.go
View File

@ -37,6 +37,9 @@ func (d *D) TrySE(nBits int, endian Endian) (int64, error) {
if err != nil {
return 0, err
}
if nBits == 0 {
return 0, nil
}
if endian == LittleEndian {
n = bitio.Uint64ReverseBytes(nBits, n)
}