Thread: Can anybody spot where I'm going wrong with this?

Decided that hex just wasn't clear enough so I modified some macros val_print relies on to produce this:

Code:

(vul1 << vul2) = 10101101111001101000101010000000u                                                                       
(vuv1 << vuv2) =      111010110111100110100010101u                                                                       
(vuv1 << vuv2) = 10000110010110111100110100010101u                                                                       
(vul1 << vul3) =  1111001101000101010000000000000u                                                                       
(vuv1 << vuv3) =      111010110111100110100010101u                                                                       
(vuv1 << vuv3) =      111010110111100110100010101u                                                                       
(vul2 << vul3) =                 1110000000000000u                                                                       
(vuv2 << vuv3) =                              111u                                                                       
(vuv2 << vuv3) =                              111u

Edit: You'll notice that each set now has 2 pairs of the vuv* values, the 1st is the pre-shift state the 2nd is the post-shift state

After some major modifications to my code:

Code:

#ifdef DBG_BIT
#include <stdio.h>
#define DBG_BIT_POS
#endif
zuv_t* _zuvShl( zuv_t *num, zul_t bytes, zul_t bits ) {
    if ( !_zuvValidNum( num ) ) return NULL;
#ifdef DBG_BIT
    printf("\n_vuvShl(): Moving %lu of %u bytes", bytes, num->size );
    printf("\n_vuvShl(): Moving %lu of %lu bits", bits, num->bits );
#endif
    // Skip oversized moving
    if ( bits > num->bits || bytes > num->size ) {
        memset( num->buff, 0, num->size );
        return num;
    }
    // We don't need lbs so skip it
    zul_t rbs = num->bits - bits;
    zus_t lps = num->size, rps = lps - bytes;
    zuc_t lbt = _zuvEndBit( num->bits ), rbt = _zuvEndBit( rbs );
#ifdef DBG_BIT
    printf("\n_vuvShl(): rbs = %lu", rbs);
    printf("\n_vuvShl(): lps = %u; rps = %u", lps, rps);
    printf("\n_vuvShl(): lbt = %02x; rbt = %02x", lbt, rbt);
#endif
    // Make sure we start with correct bytes
    --lps;
    while ( rps > 0 ) {
        --rps;
#ifdef DBG_BIT_POS
        printf("\n_vuvShl(): while()");
        printf("\n_vuvShl(): rbs = %lu", rbs);
        printf("\n_vuvShl(): lps = %u; rps = %u", lps, rps);
        printf("\n_vuvShl(): lbt = %02x; rbt = %02x", lbt, rbt);
#endif
        for ( ; rbt & rbs > 0; --rbs, lbt >>= 1, rbt >>= 1 ) {
#ifdef DBG_BIT_POS
            printf("\n_vuvShl(): for()");
            printf("\n_vuvShl(): rbs = %lu", rbs);
            printf("\n_vuvShl(): lps = %u; rps = %u", lps, rps);
            printf("\n_vuvShl(): lbt = %02x; rbt = %02x", lbt, rbt);
#endif
            if ( !lbt ) {
                lbt = SCHAR_MIN;
                // This will never be lower than rps so don't check it
                --lps;
            }
            // Set the left bit
            if ( num->buff[rps] & rbt ) {
                num->buff[lps] |= lbt;
                // We're moving bits left so make sure to clear as we go right
                num->buff[rps] ^= rbt;
            }
            // Clear left bit
            else if ( num->buff[lps] & lbt )
                num->buff[lps] ^= lbt;
        }
        // Make sure we're not retrieving 0
        rbt = SCHAR_MIN;
    }
    return num;
}

To produce this:

Code:

...
(vul2 << vul3) =                 1110000000000000u                                                                       

(vuv2 << vuv3) =                              111u                                                                       

vuvShl(): Valid Numbers!                                                                                                 

vuvShl(): Moving 13 bits                                                                                                 

_vuvShl(): Moving 1 of 4 bytes                                                                                           

_vuvShl(): Moving 5 of 32 bits                                                                                           

_vuvShl(): rbs = 27                                                                                                      

_vuvShl(): lps = 4; rps = 3                                                                                              
_vuvShl(): lbt = 80; rbt = 04                                                                                            
_vuvShl(): while()                                                                                                       

_vuvShl(): rbs = 27                                                                                                      
_vuvShl(): lps = 3; rps = 2                                                                                              
_vuvShl(): lbt = 80; rbt = 04                                                                                            

_vuvShl(): while()                                                                                                       
_vuvShl(): rbs = 27                                                                                                      

_vuvShl(): lps = 3; rps = 1                                                                                              
_vuvShl(): lbt = 80; rbt = 80                                                                                            
_vuvShl(): while()                                                                                                       
_vuvShl(): rbs = 27                                                                                                      
_vuvShl(): lps = 3; rps = 0                                                                                              

_vuvShl(): lbt = 80; rbt = 80                                                                                            

(vuv2 << vuv3) =                              111u

I narrowed down the problem area to my for loop, I am somehow not entering that loop in the first place (BTW I am using GDB online Debugger | Compiler - Code, Compile, Run, Debug online C, C++ to write and test this code)

Edit: Never mind I just noticed the reason,

Code:

rbt & rbs >0

should've been

Code:

rbt && rbs > 0