Function write_bits

libkram/astc-encoder/astcenc_integer_sequence.cpp:452–470

* @brief Write up to 8 bits at an arbitrary bit offset. * * The stored value is at most 8 bits, but can be stored at an offset of between 0 and 7 bits so may * span two separate bytes in memory. * * @param value The value to write. * @param bitcount The number of bits to write, starting from LSB. * @param bitoffset The bit offset to store at, between 0 and

 * @param[in,out] ptr         The data pointer to write to.
 */
static inline void write_bits(
	unsigned int value,
	unsigned int bitcount,
	unsigned int bitoffset,
	uint8_t ptr[2]
) {
	unsigned int mask = (1 << bitcount) - 1;
	value &= mask;
	ptr += bitoffset >> 3;
	bitoffset &= 7;
	value <<= bitoffset;
	mask <<= bitoffset;
	mask = ~mask;

	ptr[0] &= mask;
	ptr[0] |= value;
	ptr[1] &= mask >> 8;
	ptr[1] |= value >> 8;
}

/**
 * @brief Read up to 8 bits at an arbitrary bit offset.