for i, k := range sortedKeys {
		b.WriteByte('"')
		escapeStringJSON(b, k)
		b.WriteString(`":"`)
		escapeStringJSON(b, c[k])
		b.WriteByte('"')
		if i < len(sortedKeys)-1 {
			b.WriteByte(',')
		}
	}
	b.WriteByte('}')
	return b.Bytes(), nil
}

// Adapted from Go stdlib.

var hexTable = "0123456789abcdef"

// escapeStringJSON will escape a string for JSON and write it to dst.