[PATCH xserver 1/3] Rewrite the byte swapping macros.

[Eric Anholt]

Keith Packard <keithp at keithp.com> writes:

> [ Unknown signature status ]
> Eric Anholt <eric at anholt.net> writes:
>
>>  #define swapll(x) do { \
>> +		uint64_t temp; \
>>  		if (sizeof(*(x)) != 8) \
>>  			wrong_size(); \
>> -                swap_uint64((uint64_t *)(x));   \
>> +		memcpy(&temp, x, 8); \
>> +		temp = bswap_64(temp); \
>> +		memcpy(x, &temp, 8); \
>>  	} while (0)
>
>>  #define swapl(x) do { \
>> +		uint32_t temp; \
>>  		if (sizeof(*(x)) != 4) \
>>  			wrong_size(); \
>> -		if (__builtin_constant_p((uintptr_t)(x) & 3) && ((uintptr_t)(x) & 3) == 0) \
>> -			*(x) = lswapl(*(x)); \
>> -		else \
>> -			swap_uint32((uint32_t *)(x)); \
>> +		memcpy(&temp, x, 4); \
>> +		temp = bswap_32(temp); \
>> +		memcpy(x, &temp, 4); \
>>  	} while (0)
>
>>  #define swaps(x) do { \
>> +		uint16_t temp; \
>>  		if (sizeof(*(x)) != 2) \
>>  			wrong_size(); \
>> -		if (__builtin_constant_p((uintptr_t)(x) & 1) && ((uintptr_t)(x) & 1) == 0) \
>> -			*(x) = lswaps(*(x)); \
>> -		else \
>> -			swap_uint16((uint16_t *)(x)); \
>> +		memcpy(&temp, x, 2); \
>> +		temp = bswap_16(temp); \
>> +		memcpy(x, &temp, 2); \
>>  	} while (0)
>
> Any particular reason to think that x might be unaligned (and hence need
> the memcpys? Yeah, I know they're probably 'free' when things are
> aligned.
>
> The rest of this is
>
> Reviewed-by: Keith Packard <keithp at keithp.com>

The reason to think so is that the previous code had this weird stuff to
explicitly handle unaligned.  I rip out the unaligned support in patch
3, because I think it's not needed.
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