Helper Fields

One interesting (albeit not commonly used) trick is to use unions to create "helpers" for accessing different parts of a piece of memory. Consider the following:

typedef union Color {
  struct {
    uint8_t r;
    uint8_t g;
    uint8_t b;
    uint8_t a;
  } components;
  uint32_t rgba;
} color_t;

It results in a memory layout like this:

Only 4 bytes are used. And, unlike in 99% of scenarios, it makes sense to both set and get values from this union through both the components and rgba fields! Both fields in the union are exactly 32 bits in size, which means that we can "safely" (?) access the entire set of colors through the .rgba field, or get a single color component through the .components field.

The convenience of additional fields, with the efficiency of a single memory location!