ydb/contrib/libs/base64/plain64/enc_head.c

// Assume that *out is large enough to contain the output.
// Theoretically it should be 4/3 the length of src.
const uint8_t *c = (const uint8_t *)src;
uint8_t *o = (uint8_t *)out;

// Use local temporaries to avoid cache thrashing:
size_t outl = 0;
struct plain64_base64_state st;
st.bytes = state->bytes;
st.carry = state->carry;

// Turn three bytes into four 6-bit numbers:
// in[0] = 00111111
// in[1] = 00112222
// in[2] = 00222233
// in[3] = 00333333

// Duff's device, a for() loop inside a switch() statement. Legal!
switch (st.bytes)
{
	for (;;)
	{
	case 0: