Add the decimal_mul() function.

FossilOrigin-Name: 72eee04b67268ad38fd51ff32849f08c0a54cf1b481d5ecb11d77cc9c729ee03

ext/misc/decimal.c

@@ -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--;
+  }
 }
 
 /*
@@ -524,6 +529,57 @@ static void decimalSumFinalize(sqlite3_context *context){
   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 */

manifest

@@ -1,20 +1,17 @@
 B 7a876209a678a34c198b54ceef9e3c041f128a14dc73357f6a57cadadaa6cf7b
-C An\sextension\sfor\sdoing\sdecimal\sarithmetic\son\sstrings.
-D 2020-06-22T19:12:23.405
+C Add\sthe\sdecimal_mul()\sfunction.
+D 2020-06-22T21:25:37.690
 F Makefile.in 014ad669b4a5809752939c2dea83722992711b464aa56adebca80c5cc98cfdc2
 F Makefile.msc 08c8bbedfa51e21b57153370edbfee86d35bbefb53e3773a3e086fe654facccb
 F autoconf/Makefile.am a8d1d24affe52ebf8d7ddcf91aa973fa0316618ab95bb68c87cabf8faf527dc8
-F ext/misc/decimal.c ba7054d9719ceb034012e1744f6e9c1ca5fe2a00a2b83e34faf0c08a43204a64
+F ext/misc/decimal.c 334d8d34c124a8820d814dadbe1ac3daec63f504d5b322eb63671c317d3c6a3e
 F main.mk c99e452dd4edd0bea28547259421bd6cf24d41d928d24720737efc548958ca39
 F src/build.c ba1bbe563a3dc02d5fed20537603181e5289c13ea30ae5e775f552e7557adbfa
 F src/shell.c.in 7fe12fb6452de32f92bb26ee50524ec31c9d08a1c46376ca00a4ecd27472a14d
 F src/test1.c fe56c4bcaa2685ca9aa25d817a0ee9345e189aff4a5a71a3d8ba946c7776feb8
-F test/decimal.test 5c486a6baa87fe0cd1c119ffa190bcc70a23e2dd6617baa201eab9e0b0ef2efd
+F test/decimal.test c4af0264a0f30e896f617b489d69039932fe5127b02ac221d96f8af31db13826
 F tool/mkautoconfamal.sh f62353eb6c06ab264da027fd4507d09914433dbdcab9cb011cdc18016f1ab3b8
-P 067291143a63db924ead4810defb4bc6f195557412f5d1c22299f30d2d9f2a79
-R 4df2ada42f27e695d7e98ee101d73989
-T *branch * decimal
-T *sym-decimal *
-T -sym-trunk *
+P 4c3b85607feb53462ccc8b89bea699fdb132c402eae597afa33cc40a85c32329
+R d79a1d72394e5a5f6c93e9466f2c9aa1
 U drh
-Z ac0625ef3228b5eb95c4972028cf8994
+Z 3092a9d89a34e083e375231f8e857b54

manifest.uuid

@@ -1 +1 @@
-4c3b85607feb53462ccc8b89bea699fdb132c402eae597afa33cc40a85c32329
+72eee04b67268ad38fd51ff32849f08c0a54cf1b481d5ecb11d77cc9c729ee03

test/decimal.test

@@ -115,4 +115,14 @@ do_execsql_test 4010 {
     FROM t3;
 } {1505500000000000000015055.00000000000000015055}
 
+do_execsql_test 5000 {
+  WITH RECURSIVE c(x,y,z) AS (
+    VALUES(0,'1','1')
+    UNION ALL
+    SELECT x+1, decimal_mul(y,'2'), decimal_mul(z,'0.5')
+      FROM c WHERE x<32
+  )
+  SELECT count(*) FROM c WHERE decimal_mul(y,z)='1';
+} {33}
+
 finish_test