[PATCH v2] msacm32: Rewrite PCM conversion functions.

[Alex Henrie]

2017-06-14 11:05 GMT-06:00 Alex Henrie <alexhenrie24 at gmail.com>:
> 2017-06-14 10:13 GMT-06:00 Zebediah Figura <z.figura12 at gmail.com>:
>> On 06/14/2017 08:42 AM, Andrew Eikum wrote:
>>>
>>> On Tue, Jun 13, 2017 at 04:35:52PM -0500, Zebediah Figura wrote:
>>>>
>>>> +#define PCM_CVT_CHANGE_FUNC(name)      static void name(DWORD srcRate,
>>>> const unsigned char *src, DWORD *nsrc, \
>>>> +                                                        DWORD dstRate,
>>>> unsigned char *dst, DWORD *ndst) \
>>>> +    { \
>>>> +    DWORD error = srcRate / 2; \
>>>> +    DWORD srcUsed = 0, dstUsed = 0; \
>>>> +    for (srcUsed = 0; srcUsed < *nsrc; srcUsed++) { \
>>>> +        error += dstRate; \
>>>> +        while (error > srcRate) { \
>>>> +            if (dstUsed == *ndst) { \
>>>> +                *nsrc = srcUsed; \
>>>> +                *ndst = dstUsed; \
>>>> +                return; \
>>>> +            }
>>>> +
>>>> +            /* conversion is done here */
>>>> +
>>>> +#define PCM_CVT_CHANGE_FUNC_END(offset)        \
>>>> +            dstUsed++; \
>>>> +            error -= srcRate; \
>>>> +        } \
>>>> +        src += offset; \
>>>> +    } \
>>>> +    *nsrc = srcUsed; \
>>>> +    *ndst = dstUsed; \
>>>> +}
>>>> +
>>>> +PCM_CVT_CHANGE_FUNC(cvtSS88C)
>>>> +    *dst++ = src[0];
>>>> +    *dst++ = src[1];
>>>> +PCM_CVT_CHANGE_FUNC_END(2)
>>>> +
>>>
>>>
>>> I really dislike complicated preprocessor tricks. Can't this be done
>>> in a similar way with real functions? If not, I'd rather have the
>>> copy-pasted code than these difficult macros.
>>>
>>> Andrew
>>>
>>
>> As far as I know there's no way to keep this structure without either using
>> macros or rewriting the same function 20 times, neither of which is very
>> desirable. On the other hand, might it be worth sacrificing a slight bit of
>> efficiency (which may not even be that much) as in the attached patch?
>
> You could make each codec function pass a codec-specific callback
> function to the common function.

Actually, forget I said anything. The patch you attached is similar,
but even cleaner than what I was thinking.

-Alex