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Implement complete VarDecDiv() for any valid DECIMAL.
This commit is contained in:
Alex Villacís Lasso
Alexandre Julliard
parent
cb443bdb04
commit
69b5f808a7
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@ -4850,6 +4850,344 @@ static int VARIANT_DI_tostringW(VARIANT_DI * a, WCHAR * s, unsigned int n)
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return overflow;
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}
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/* shift the bits of a DWORD array to the left. p[0] is assumed LSB */
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static void VARIANT_int_shiftleft(DWORD * p, unsigned int n, unsigned int shift)
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{
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DWORD shifted;
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unsigned int i;
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/* shift whole DWORDs to the left */
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while (shift >= 32)
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{
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memmove(p + 1, p, (n - 1) * sizeof(DWORD));
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*p = 0; shift -= 32;
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}
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/* shift remainder (1..31 bits) */
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shifted = 0;
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if (shift > 0) for (i = 0; i < n; i++)
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{
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DWORD b;
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b = p[i] >> (32 - shift);
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p[i] = (p[i] << shift) | shifted;
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shifted = b;
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}
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}
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/* add the (unsigned) numbers stored in two DWORD arrays with LSB at index 0.
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Value at v is incremented by the value at p. Any size is supported, provided
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that v is not shorter than p. Any unapplied carry is returned as a result.
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*/
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static unsigned char VARIANT_int_add(DWORD * v, unsigned int nv, DWORD * p,
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unsigned int np)
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{
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unsigned char carry = 0;
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if (nv >= np) {
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ULONGLONG sum;
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unsigned int i;
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for (i = 0; i < np; i++) {
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sum = (ULONGLONG)v[i]
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+ (ULONGLONG)p[i]
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+ (ULONGLONG)carry;
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v[i] = sum & 0xffffffff;
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carry = sum >> 32;
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}
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for (; i < nv && carry; i++) {
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sum = (ULONGLONG)v[i]
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+ (ULONGLONG)carry;
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v[i] = sum & 0xffffffff;
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carry = sum >> 32;
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}
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}
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return carry;
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}
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/* perform integral division with operand p as dividend. Parameter n indicates
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number of available DWORDs in divisor p, but available space in p must be
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actually at least 2 * n DWORDs, because the remainder of the integral
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division is built in the next n DWORDs past the start of the quotient. This
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routine replaces the dividend in p with the quotient, and appends n
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additional DWORDs for the remainder.
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Thanks to Lee & Mark Atkinson for their book _Using_C_ (my very first book on
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C/C++ :-) where the "longhand binary division" algorithm was exposed for the
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source code to the VLI (Very Large Integer) division operator. This algorithm
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was then heavily modified by me (Alex Villacis Lasso) in order to handle
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variably-scaled integers such as the MS DECIMAL representation.
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*/
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static void VARIANT_int_div(DWORD * p, unsigned int n, DWORD * divisor,
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unsigned int dn)
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{
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unsigned int i;
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DWORD tempsub[8];
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DWORD * negdivisor = tempsub + n;
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/* build 2s-complement of divisor */
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for (i = 0; i < n; i++) negdivisor[i] = (i < dn) ? ~divisor[i] : 0xFFFFFFFF;
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p[n] = 1;
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VARIANT_int_add(negdivisor, n, p + n, 1);
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memset(p + n, 0, n * sizeof(DWORD));
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/* skip all leading zero DWORDs in quotient */
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for (i = 0; i < n && !p[n - 1]; i++) VARIANT_int_shiftleft(p, n, 32);
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/* i is now number of DWORDs left to process */
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for (i <<= 5; i < (n << 5); i++) {
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VARIANT_int_shiftleft(p, n << 1, 1); /* shl quotient+remainder */
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/* trial subtraction */
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memcpy(tempsub, p + n, n * sizeof(DWORD));
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VARIANT_int_add(tempsub, n, negdivisor, n);
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/* check whether result of subtraction was negative */
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if ((tempsub[n - 1] & 0x80000000) == 0) {
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memcpy(p + n, tempsub, n * sizeof(DWORD));
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p[0] |= 1;
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}
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}
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}
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/* perform integral multiplication by a byte operand. Used for scaling by 10 */
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static unsigned char VARIANT_int_mulbychar(DWORD * p, unsigned int n, unsigned char m)
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{
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unsigned int i;
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ULONG iOverflowMul;
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for (iOverflowMul = 0, i = 0; i < n; i++)
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p[i] = VARIANT_Mul(p[i], m, &iOverflowMul);
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return (unsigned char)iOverflowMul;
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}
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/* increment value in A by the value indicated in B, with scale adjusting.
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Modifies parameters by adjusting scales. Returns 0 if addition was
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successful, nonzero if a parameter underflowed before it could be
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successfully used in the addition.
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*/
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static int VARIANT_int_addlossy(
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DWORD * a, int * ascale, unsigned int an,
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DWORD * b, int * bscale, unsigned int bn)
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{
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int underflow = 0;
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if (VARIANT_int_iszero(a, an)) {
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/* if A is zero, copy B into A, after removing digits */
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while (bn > an && !VARIANT_int_iszero(b + an, bn - an)) {
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VARIANT_int_divbychar(b, bn, 10);
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(*bscale)--;
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}
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memcpy(a, b, an * sizeof(DWORD));
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*ascale = *bscale;
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} else if (!VARIANT_int_iszero(b, bn)) {
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unsigned int tn = an + 1;
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DWORD t[5];
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if (bn + 1 > tn) tn = bn + 1;
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if (*ascale != *bscale) {
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/* first (optimistic) try - try to scale down the one with the bigger
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scale, while this number is divisible by 10 */
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DWORD * digitchosen;
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unsigned int nchosen;
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int * scalechosen;
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int targetscale;
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if (*ascale < *bscale) {
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targetscale = *ascale;
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scalechosen = bscale;
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digitchosen = b;
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nchosen = bn;
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} else {
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targetscale = *bscale;
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scalechosen = ascale;
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digitchosen = a;
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nchosen = an;
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}
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memset(t, 0, tn * sizeof(DWORD));
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memcpy(t, digitchosen, nchosen * sizeof(DWORD));
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/* divide by 10 until target scale is reached */
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while (*scalechosen > targetscale) {
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unsigned char remainder = VARIANT_int_divbychar(t, tn, 10);
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if (!remainder) {
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(*scalechosen)--;
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memcpy(digitchosen, t, nchosen * sizeof(DWORD));
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} else break;
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}
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}
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if (*ascale != *bscale) {
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DWORD * digitchosen;
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unsigned int nchosen;
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int * scalechosen;
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int targetscale;
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/* try to scale up the one with the smaller scale */
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if (*ascale > *bscale) {
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targetscale = *ascale;
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scalechosen = bscale;
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digitchosen = b;
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nchosen = bn;
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} else {
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targetscale = *bscale;
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scalechosen = ascale;
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digitchosen = a;
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nchosen = an;
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}
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memset(t, 0, tn * sizeof(DWORD));
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memcpy(t, digitchosen, nchosen * sizeof(DWORD));
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/* multiply by 10 until target scale is reached, or
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significant bytes overflow the number
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*/
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while (*scalechosen < targetscale && t[nchosen] == 0) {
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VARIANT_int_mulbychar(t, tn, 10);
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if (t[nchosen] == 0) {
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/* still does not overflow */
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(*scalechosen)++;
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memcpy(digitchosen, t, nchosen * sizeof(DWORD));
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}
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}
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}
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if (*ascale != *bscale) {
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/* still different? try to scale down the one with the bigger scale
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(this *will* lose significant digits) */
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DWORD * digitchosen;
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unsigned int nchosen;
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int * scalechosen;
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int targetscale;
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if (*ascale < *bscale) {
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targetscale = *ascale;
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scalechosen = bscale;
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digitchosen = b;
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nchosen = bn;
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} else {
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targetscale = *bscale;
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scalechosen = ascale;
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digitchosen = a;
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nchosen = an;
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}
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memset(t, 0, tn * sizeof(DWORD));
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memcpy(t, digitchosen, nchosen * sizeof(DWORD));
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/* divide by 10 until target scale is reached */
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while (*scalechosen > targetscale) {
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VARIANT_int_divbychar(t, tn, 10);
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(*scalechosen)--;
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memcpy(digitchosen, t, nchosen * sizeof(DWORD));
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}
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}
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/* check whether any of the operands still has significant digits
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(underflow case 1)
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*/
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if (VARIANT_int_iszero(a, an) || VARIANT_int_iszero(b, bn)) {
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underflow = 1;
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} else {
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/* at this step, both numbers have the same scale and can be added
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as integers. However, the result might not fit in A, so further
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scaling down might be necessary.
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*/
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while (!underflow) {
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memset(t, 0, tn * sizeof(DWORD));
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memcpy(t, a, an * sizeof(DWORD));
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VARIANT_int_add(t, tn, b, bn);
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if (VARIANT_int_iszero(t + an, tn - an)) {
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/* addition was successful */
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memcpy(a, t, an * sizeof(DWORD));
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break;
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} else {
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/* addition overflowed - remove significant digits
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from both operands and try again */
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VARIANT_int_divbychar(a, an, 10); (*ascale)--;
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VARIANT_int_divbychar(b, bn, 10); (*bscale)--;
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/* check whether any operand keeps significant digits after
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scaledown (underflow case 2)
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*/
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underflow = (VARIANT_int_iszero(a, an) || VARIANT_int_iszero(b, bn));
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}
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}
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}
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}
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return underflow;
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}
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/* perform complete DECIMAL division in the internal representation. Returns
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0 if the division was completed (even if quotient is set to 0), or nonzero
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in case of quotient overflow.
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*/
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static HRESULT VARIANT_DI_div(VARIANT_DI * dividend, VARIANT_DI * divisor, VARIANT_DI * quotient)
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{
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HRESULT r_overflow = S_OK;
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if (VARIANT_int_iszero(divisor->bitsnum, sizeof(divisor->bitsnum)/sizeof(DWORD))) {
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/* division by 0 */
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r_overflow = DISP_E_DIVBYZERO;
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} else if (VARIANT_int_iszero(dividend->bitsnum, sizeof(dividend->bitsnum)/sizeof(DWORD))) {
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VARIANT_DI_clear(quotient);
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} else {
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int quotientscale, remainderscale, tempquotientscale;
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DWORD remainderplusquotient[8];
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int underflow;
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quotientscale = remainderscale = (int)dividend->scale - (int)divisor->scale;
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tempquotientscale = quotientscale;
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VARIANT_DI_clear(quotient);
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quotient->sign = (dividend->sign ^ divisor->sign) ? 1 : 0;
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/* The following strategy is used for division
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1) if there was a nonzero remainder from previous iteration, use it as
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dividend for this iteration, else (for first iteration) use intended
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dividend
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2) perform integer division in temporary buffer, develop quotient in
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low-order part, remainder in high-order part
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3) add quotient from step 2 to final result, with possible loss of
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significant digits
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4) multiply integer part of remainder by 10, while incrementing the
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scale of the remainder. This operation preserves the intended value
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of the remainder.
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5) loop to step 1 until one of the following is true:
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a) remainder is zero (exact division achieved)
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b) addition in step 3 fails to modify bits in quotient (remainder underflow)
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*/
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memset(remainderplusquotient, 0, sizeof(remainderplusquotient));
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memcpy(remainderplusquotient, dividend->bitsnum, sizeof(dividend->bitsnum));
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do {
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VARIANT_int_div(
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remainderplusquotient, 4,
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divisor->bitsnum, sizeof(divisor->bitsnum)/sizeof(DWORD));
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underflow = VARIANT_int_addlossy(
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quotient->bitsnum, "ientscale, sizeof(quotient->bitsnum) / sizeof(DWORD),
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remainderplusquotient, &tempquotientscale, 4);
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VARIANT_int_mulbychar(remainderplusquotient + 4, 4, 10);
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memcpy(remainderplusquotient, remainderplusquotient + 4, 4 * sizeof(DWORD));
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tempquotientscale = ++remainderscale;
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} while (!underflow && !VARIANT_int_iszero(remainderplusquotient + 4, 4));
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/* quotient scale might now be negative (extremely big number). If, so, try
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to multiply quotient by 10 (without overflowing), while adjusting the scale,
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until scale is 0. If this cannot be done, it is a real overflow.
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*/
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while (!r_overflow && quotientscale < 0) {
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memset(remainderplusquotient, 0, sizeof(remainderplusquotient));
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memcpy(remainderplusquotient, quotient->bitsnum, sizeof(quotient->bitsnum));
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VARIANT_int_mulbychar(remainderplusquotient, sizeof(remainderplusquotient)/sizeof(DWORD), 10);
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if (VARIANT_int_iszero(remainderplusquotient + sizeof(quotient->bitsnum)/sizeof(DWORD),
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(sizeof(remainderplusquotient) - sizeof(quotient->bitsnum))/sizeof(DWORD))) {
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quotientscale++;
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memcpy(quotient->bitsnum, remainderplusquotient, sizeof(quotient->bitsnum));
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} else r_overflow = DISP_E_OVERFLOW;
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}
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if (!r_overflow) {
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if (quotientscale <= 255) quotient->scale = quotientscale;
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else VARIANT_DI_clear(quotient);
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}
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}
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return r_overflow;
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}
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/************************************************************************
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* VarDecDiv (OLEAUT32.178)
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*
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@ -4866,8 +5204,59 @@ static int VARIANT_DI_tostringW(VARIANT_DI * a, WCHAR * s, unsigned int n)
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*/
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HRESULT WINAPI VarDecDiv(const DECIMAL* pDecLeft, const DECIMAL* pDecRight, DECIMAL* pDecOut)
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{
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FIXME("(%p,%p,%p)-stub!\n",pDecLeft,pDecRight,pDecOut);
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return DISP_E_OVERFLOW;
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HRESULT hRet = S_OK;
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VARIANT_DI di_left, di_right, di_result;
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HRESULT divresult;
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if (!pDecLeft || !pDecRight || !pDecOut) return E_INVALIDARG;
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VARIANT_DIFromDec(pDecLeft, &di_left);
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VARIANT_DIFromDec(pDecRight, &di_right);
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divresult = VARIANT_DI_div(&di_left, &di_right, &di_result);
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if (divresult)
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{
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/* division actually overflowed */
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hRet = divresult;
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}
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else
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{
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hRet = S_OK;
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if (di_result.scale > DEC_MAX_SCALE)
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{
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unsigned char remainder = 0;
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/* division underflowed. In order to comply with the MSDN
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specifications for DECIMAL ranges, some significant digits
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must be removed
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*/
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WARN("result scale is %u, scaling (with loss of significant digits)...\n",
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di_result.scale);
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while (di_result.scale > DEC_MAX_SCALE &&
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!VARIANT_int_iszero(di_result.bitsnum, sizeof(di_result.bitsnum) / sizeof(DWORD)))
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{
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remainder = VARIANT_int_divbychar(di_result.bitsnum, sizeof(di_result.bitsnum) / sizeof(DWORD), 10);
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di_result.scale--;
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}
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if (di_result.scale > DEC_MAX_SCALE)
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{
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WARN("result underflowed, setting to 0\n");
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di_result.scale = 0;
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di_result.sign = 0;
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}
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else if (remainder >= 5) /* round up result - native oleaut32 does this */
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{
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unsigned int i;
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for (remainder = 1, i = 0; i < sizeof(di_result.bitsnum) / sizeof(DWORD) && remainder; i++) {
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ULONGLONG digit = di_result.bitsnum[i] + 1;
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remainder = (digit > 0xFFFFFFFF) ? 1 : 0;
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di_result.bitsnum[i] = digit & 0xFFFFFFFF;
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}
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}
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}
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VARIANT_DecFromDI(&di_result, pDecOut);
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}
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return hRet;
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}
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/************************************************************************
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