Question

Let’s say I have defined an array float floatBuffer[4] and I have a struct: struct vec3{float x,y,z;} myVec;

before the vec3 assignment, I assign: floatBuffer[3] = 0.0f;

(If this is possible,) In what ways can I assign myVec to floatBuffer[0] (binary copy), so that

• floatBuffer[0] == myVec.x

• floatBuffer[1] == myVec.y

• floatBuffer[2] == myVec.z

• floatBuffer[3] == 0.0f

  ?

Answer 1

The obvious answer is:

floatBuffer[0] = myVec.x;
floatBuffer[1] = myVec.y;
floatBuffer[2] = myVec.z;

If you’re willing to make assumptions on struct layout, and your compiler generates crappy code for the direct assignments, document your assumptions and do a memcpy:

static_assert(sizeof(myVec) == sizeof(float[3]), "myVec should not have padding");

memcpy(&floatBuffer[0], &myVec, sizeof(myVec));