lazarus/streaming/bitreader.go

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package streaming
import (
"io"
)
type BitReader struct {
reader io.Reader
offset int
buffer [1]byte
}
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func NewBitReader(reader io.Reader) *BitReader {
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return &BitReader{reader: reader}
}
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func (r *BitReader) ReadBool() (bool, error) {
value, err := r.ReadUint64(1)
return value == 1, err
}
func (r *BitReader) ReadInt8(count int) (int8, error) {
value, err := r.ReadInt64(count)
return int8(value), err
}
func (r *BitReader) ReadUint8(count int) (uint8, error) {
value, err := r.ReadUint64(count)
return uint8(value), err
}
func (r *BitReader) ReadInt16(count int) (int16, error) {
value, err := r.ReadInt64(count)
return int16(value), err
}
func (r *BitReader) ReadUint16(count int) (uint16, error) {
value, err := r.ReadUint64(count)
return uint16(value), err
}
func (r *BitReader) ReadInt32(count int) (int32, error) {
value, err := r.ReadInt64(count)
return int32(value), err
}
func (r *BitReader) ReadUint32(count int) (uint32, error) {
value, err := r.ReadUint64(count)
return uint32(value), err
}
func (r *BitReader) ReadInt64(count int) (int64, error) {
value, err := r.ReadUint64(count)
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if err != nil {
return 0, err
}
if count > 0 {
valueMasked := value &^ (1 << uint(count-1))
if valueMasked != value {
return -int64(valueMasked), nil
}
}
return int64(value), nil
}
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func (r *BitReader) ReadUint64(count int) (uint64, error) {
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var value uint64
for count > 0 {
bitOffset := r.offset % 8
bitsLeft := 8 - bitOffset
if bitsLeft == 8 {
if _, err := r.reader.Read(r.buffer[:]); err != nil {
return 0, err
}
}
bitsRead := count
if bitsRead > bitsLeft {
bitsRead = bitsLeft
}
buffer := r.buffer[0]
buffer <<= uint(bitOffset)
buffer >>= (uint(bitOffset) + uint(bitsLeft-bitsRead))
value <<= uint(bitsRead)
value |= uint64(buffer)
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r.offset += bitsRead
count -= bitsRead
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}
return value, nil
}