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https://git.numenor-labs.us/dsfx.git
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58 lines
1.6 KiB
Go
58 lines
1.6 KiB
Go
package buffer
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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// MaxUint16 is the maximum value of a uint16. It is used to check if the
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// length of the data is too large to be encoded in a uint16.
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const MaxUint16 = 0xFFFF
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// ErrInvalidLength is the error message returned when the length of the data
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// is too large to be encoded in a uint16.
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var ErrInvalidLength = errors.New("data length is too large to be encoded in a uint16")
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// NewLenPrefixed returns a new buffer with a length prefix. The length prefix is
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// 2 bytes long and is encoded in big-endian order. The length prefix is
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// followed by the data.
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func NewLenPrefixed(data []byte) ([]byte, error) {
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length := len(data)
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// Overflow Guard: If the length of the data is greater than the maximum
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// value of a uint16, return an error.
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if length > MaxUint16 {
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return nil, ErrInvalidLength
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}
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buf := make([]byte, 2+len(data))
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binary.BigEndian.PutUint16(buf, uint16(len(data)))
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copy(buf[2:], data)
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return buf, nil
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}
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func ReadLenPrefixed(maxSize uint16, r io.Reader) ([]byte, error) {
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lenBuf := make([]byte, 2)
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if _, err := io.ReadFull(r, lenBuf); err != nil {
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return nil, err
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}
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if len(lenBuf) < 2 {
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return nil, errors.New("buffer is too small to contain length prefix")
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}
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length := binary.BigEndian.Uint16(lenBuf)
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if length > maxSize {
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return nil, errors.New("data length is too large to be encoded in a uint16")
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}
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buf := make([]byte, length)
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if _, err := io.ReadFull(r, buf); err != nil {
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return nil, err
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}
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if len(buf) < int(length) {
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return nil, errors.New("buffer is too small to contain data")
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}
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return buf, nil
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}
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