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Add the decimal_mul() function.

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FossilOrigin-Name: 72eee04b67268ad38fd51ff32849f08c0a54cf1b481d5ecb11d77cc9c729ee03
This commit is contained in:
drh
2020-06-22 21:25:37 +00:00
parent beb9def059
commit 427af8dc3d
4 changed files with 77 additions and 13 deletions
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61
ext/misc/decimal.c
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@ -298,7 +298,8 @@ cmp_done:
}
/*
** Remove leading zeros from the Decimal
** Remove leading zeros from before the decimal and
** trailing zeros after the decimal.
*/
static void decimal_normalize(Decimal *p){
int i;
@ -310,6 +311,10 @@ static void decimal_normalize(Decimal *p){
memmove(p->a, p->a+i, p->nDigit - i);
p->nDigit -= i;
}
while( p->nFrac && p->a[p->nDigit-1]==0 ){
p->nFrac--;
p->nDigit--;
}
}
/*
@ -523,7 +528,58 @@ static void decimalSumFinalize(sqlite3_context *context){
decimal_result(context, p);
decimal_clear(p);
}
/*
** SQL Function: decimal_mul(X, Y)
**
** Return the product of X and Y.
*/
static void decimalMulFunc(
sqlite3_context *context,
int argc,
sqlite3_value **argv
){
Decimal *pA = decimal_new(context, argv[0], 0, 0);
Decimal *pB = decimal_new(context, argv[1], 0, 0);
signed char *acc = 0;
int i, j, k;
if( pA==0 || pA->oom || pA->isNull
|| pB==0 || pB->oom || pB->isNull
){
goto mul_end;
}
acc = sqlite3_malloc64( pA->nDigit + pB->nDigit + 2 );
if( acc==0 ){
sqlite3_result_error_nomem(context);
goto mul_end;
}
memset(acc, 0, pA->nDigit + pB->nDigit + 2);
for(i=pA->nDigit-1; i>=0; i--){
signed char f = pA->a[i];
int carry = 0, x;
for(j=pB->nDigit-1, k=i+j+3; j>=0; j--, k--){
int x = acc[k] + f*pB->a[j] + carry;
acc[k] = x%10;
carry = x/10;
}
x = acc[k] + carry;
acc[k] = x%10;
acc[k-1] += x/10;
}
sqlite3_free(pA->a);
pA->a = acc;
acc = 0;
pA->nDigit += pB->nDigit + 2;
pA->nFrac += pB->nFrac;
pA->sign ^= pB->sign;
decimal_normalize(pA);
decimal_result(context, pA);
mul_end:
sqlite3_free(acc);
decimal_free(pA);
decimal_free(pB);
}
#ifdef _WIN32
__declspec(dllexport)
@ -544,6 +600,7 @@ int sqlite3_decimal_init(
{ "decimal_cmp", 2, decimalCmpFunc },
{ "decimal_add", 2, decimalAddFunc },
{ "decimal_sub", 2, decimalSubFunc },
{ "decimal_mul", 2, decimalMulFunc },
};
int i;
(void)pzErrMsg; /* Unused parameter */