Function encodeStringValue

structure/string.go:533–572

encodeStringValue encodes the value format: [type][expire][value] type: 1 byte expire: 8 bytes value: n bytes

(value []byte, ttl time.Duration)

// expire: 8 bytes
// value: n bytes
func encodeStringValue(value []byte, ttl time.Duration) ([]byte, error) {
	// Create a byte slice buf with a length of binary.MaxVarintLen64
	// to hold the encoded value and additional data.
	buf := make([]byte, binary.MaxVarintLen64)

	// Set the first element of buf to represent the data structure type as String.
	buf[0] = String

	// Use the variable bufIndex to keep track of the current index position in buf,
	// starting from 1 to indicate the number of bytes written so far.
	var bufIndex = 1

	// The variable expire is used to store the expiration time, initially set to 0.
	var expire int64 = 0

	// Calculate the expiration time by adding ttl to the current time,
	// convert it to nanoseconds, and store it in the expire variable.
	if ttl != 0 {
		expire = time.Now().Add(ttl).UnixNano()
	}

	// Encode the expiration time expire as a variable-length integer
	// and write it to the sub-slice of byte slice buf starting
	// from the current index position bufIndex.
	bufIndex += binary.PutVarint(buf[bufIndex:], expire)

	// Create a byte slice encValue with a length of bufIndex + len(value)
	// to hold the encoded value and additional data.
	encValue := make([]byte, bufIndex+len(value))

	// Copy the encoded value from the beginning of buf
	// to the corresponding position in encValue.
	copy(encValue[:bufIndex], buf[:bufIndex])

	// Copy the original value value to the remaining positions in encValue,
	// starting from the index bufIndex.
	copy(encValue[bufIndex:], value)

	return encValue, nil
}

var (
	// ErrInvalidValue is returned if the value is invalid.