path: root/libsyscalls_to_tracee_endian.c

/* See LICENSE file for copyright and license details. */
#include "common.h"


/* XXX be smarter if using the same byteorder */
enum libsyscalls_error
libsyscalls_to_tracee_endian(unsigned long long int value_in,
                             const struct libsyscalls_datatype_description *type,
                             void *value_out, size_t out_offset)
{
	const unsigned long long int limit = sizeof(long long int) / sizeof(char) * CHAR_BIT;
	unsigned long long int bytebits, bytemask, byte, remmask, valmask;
	unsigned long long int offset, offset_byte, offset_bit;
	unsigned char *out = value_out;
	size_t i;

	if (!type || !value_out || (unsigned long long int)type->width_in_bits > limit)
		return LIBSYSCALLS_E_INVAL;

	bytebits = (unsigned long long int)type->width_in_bits;
	for (i = 0; !LIBSYSCALLS_IS_BYTEORDER_END_AT(type, i); i++)
		if (type->byteorder[i] && (unsigned long long int)type->byteorder[i] < bytebits)
			bytebits = (unsigned long long int)type->byteorder[i];

	if (bytebits > limit)
		return LIBSYSCALLS_E_INVAL;
	else if (bytebits == limit)
		bytemask = ~0ULL;
	else
		bytemask = (1ULL << bytebits) - 1ULL;

	if ((unsigned long long int)type->width_in_bits == limit)
		valmask = ~0ULL;
	else
		valmask = (1ULL << (unsigned long long int)type->width_in_bits) - 1ULL;

	for (i = 0; !LIBSYSCALLS_IS_BYTEORDER_END_AT(type, i); i++) {
		offset = out_offset;
		offset_byte = offset / CHAR_BIT;
		offset_bit = offset % CHAR_BIT;
		out_offset += bytebits;

		byte = value_in >> type->byteorder[i];
		byte &= remmask = bytemask & (valmask >> type->byteorder[i]);

		out[offset_byte] &= (unsigned char)~(remmask << offset_bit);
		out[offset_byte] |= (unsigned char)(byte << offset_bit);
		if (bytebits != limit && (remmask >>= CHAR_BIT - offset_bit)) {
			byte >>= CHAR_BIT - offset_bit;
			do {
				offset_byte += 1;
				out[offset_byte] &= (unsigned char)~remmask;
				out[offset_byte] |= (unsigned char)byte;
				byte >>= CHAR_BIT;
			} while (remmask >>= CHAR_BIT);
		}
	}

	return LIBSYSCALLS_E_OK;
}