Golang split byte slice in chunks sized by limit

bytes_split.go

func split(buf []byte, lim int) [][]byte {
	var chunk []byte
	chunks := make([][]byte, 0, len(buf)/lim+1)
	for len(buf) >= lim {
		chunk, buf = buf[:lim], buf[lim:]
		chunks = append(chunks, chunk)
	}
	if len(buf) > 0 {
		chunks = append(chunks, buf[:len(buf)])
	}
	return chunks
}

bytes_split_join.go

const PackSizeLimit = 5 * 1024 * 1024

// [a b c] -> [[a, b], [c]]
// where (len(a)+len(b) < MAX) and (len(c) < MAX),
// where (len(a) < MAX) and (len(b) < MAX) and (len(c) < MAX),
// but (len(a) + len(b) + len(c)) > MAX
func splitForJoin(chunks [][]byte, lim int) [][][]byte {
	var result [][][]byte
	for len(chunks) > 0 {
		for i, v := range chunks {
			if size+len(v) > PackSizeLimit {
				chunks = chunks[i:]
				break
			}
		}
		// TODO
	}
	return result
}