It may worth to try the switch case structure that should compile to
something similar to the jump table in your example:

switch ( i ) {
    case 7: *pbuf++ <<=3D 1 +c;
    case 6: *pbuf++ <<=3D 1 +c;
    .....
    case 1: *pbuf++ <<=3D 1 +c;
    case 0: *pbuf++ <<=3D 1 +c;
}

Tam=E1s

On 2/28/10, Scott Dattalo <scott@dattalo.com> wrote:
>> Hi All,
>>
>> I browsed the PICList source library, but couldn't find anything
>> similar to what I was looking for.
>>
>> I have a buffer of "packed" "bytes" where each byte is less that
>> 8-bits in length.
>>
>> This buffer is generated by capturing a bitstream (LSB first) and
>> right shifting in to the LSB of a buffer.
>>
>> e.g. for bytes sized 7 bits, if the first byte is all ones, the second
>> is all zeros, and the third is all ones,
>> my buffer looks as such:
>>
>> 01111111
>> 11000000
>> xxx11111
>> xxxxxxxx
>> ...
>>
>> What I would like to do is break each "byte" out of the buffer and put
>> it into another buffer, e.g.
>>
>> 01111111
>> 00000000
>> 01111111
>> 0xxxxxxx
>> 0xxxxxxx
>
> Hi Scott,
>
> Here's an untested 18F version:
>
>    lfsr  0,packedBuffer   ; Source
>    lfsr  1,packedBuffer   ; Source (used as a temporary)
>    lfsr  2,unpackedBuffer ; Destination
>    movlw numberOfBytes
>    movwf count
>
> loop:
>    movf  indf0,W      ; Get the next packed byte
>    andlw 0x7f
>    movwf postinc2     ; And save it unpacked
>
>    movf  count,W      ; Are more than 7 bytes left?
>    sublw 7
>    skpc
>     bra  rotate7      ; There are more than 7 left so rotate them
>
>    addwf WREG,W       ; multiply (7-count) by 2
>    addlw low(rotate7) ; And only rotate what's remaining
>    skpnc
>      incf PCLATH,F
>    movwf PCL
> rotate7:
>    rlcf  postinc0,F
>    rlcf  postinc0,F
>    rlcf  postinc0,F
>    rlcf  postinc0,F
>    rlcf  postinc0,F
>    rlcf  postinc0,F
>
>    movf  postinc1,W   ; Increment FSR1 (don't care about W)
>    movff FSR1L, FSR0L
>    movff FSR1H, FSR0H
>
>    decfsz count,F
>      bra  loop
>    return
>
> Here's the untested C-version
>
> void unpackBuffer(unsigned char *pSrc, unsigned char *pDest, unsigned char
> size)
> {
>   unsigned char i,j;
>
>   for (i=3D0; i<size; i++)
>   {
>     unsigned char *pTemp;
>     unsigned char carryIn;
>     unsigned char carryOut;
>
>     // copy the source to the destination
>     *pDest++ =3D *pSrc & 0x7f;
>
>     pSrc++;
>
>     // Rotate the next 7 bytes (if 7 or more are left)
>     j =3D i > 7 ? 7 : i;
>
>     // The MSB needs to be moved to the LSB of
>     // of the next byte
>
>     carryOut =3D (*pSrc++ & 0x80) ? 1 : 0;
>     pTemp =3D pSrc;
>     while (j)
>     {
>       carryIn =3D carryOut;
>
>       // Get the carry for the next byte
>       carryOut =3D (*pTemp & 0x80) ? 1 : 0;
>
>       // rotate this byte and pick up carry from previous
>       *pTemp =3D (*pTemp << 1) + carryIn;
>
>       // Point to the next
>       pTemp++;
>     }
>   }
>
>
> I imagine the assembly version is a little faster.
>
> Scott
> --
> http://www.piclist.com PIC/SX FAQ & list archive
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> http://mailman.mit.edu/mailman/listinfo/piclist
>

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Sent from my mobile device

int main() { char *a,*s,*q; printf(s=3D"int main() { char *a,*s,*q;
printf(s=3D%s%s%s, q=3D%s%s%s%s,s,q,q,a=3D%s%s%s%s,q,q,q,a,a,q); }",
q=3D"\"",s,q,q,a=3D"\\",q,q,q,a,a,q); }

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