Experiments with a new algorithm for converting ieee-754 binary64 numbers

into decimal.

FossilOrigin-Name: e923405e448385085224f9289991b303d86b02763535ea77d6fcee98ba6fc1f2

manifest

@@ -1,5 +1,5 @@
-C Add\ssupport\sfor\ssqlite3_stmt_scanstatus_v2()\sprofiling\sof\sGROUP\sBY\sclauses\sthat\suse\sa\stemp\sb-tree,\sand\sfor\ssub-queries\simplemented\sas\sco-routines.
-D 2023-06-30T18:31:37.545
+C Experiments\swith\sa\snew\salgorithm\sfor\sconverting\sieee-754\sbinary64\snumbers\ninto\sdecimal.
+D 2023-06-30T18:35:43.344
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -590,7 +590,7 @@ F src/delete.c cd5f5cd06ed0b6a882ec1a8c2a0d73b3cecb28479ad19e9931c4706c5e2182be
 F src/expr.c 8d1656b65e26af3e34f78e947ac423f0d20c214ed25a67486e433bf16ca6b543
 F src/fault.c 460f3e55994363812d9d60844b2a6de88826e007
 F src/fkey.c a7fcbf7e66d14dbb73cf49f31489ebf66d0e6006c62b95246924a3bae9f37b36
-F src/func.c 6b4804738b4d869f40625958b476a8f964d3df65b626e72a530d76051863cf32
+F src/func.c 699e19ca0dc580a024eb343f3a3abfb646e5438e36d377023d485a3038d789d5
 F src/global.c bd0892ade7289f6e20bff44c07d06371f2ff9b53cea359e7854b9b72f65adc30
 F src/hash.c 9ee4269fb1d6632a6fecfb9479c93a1f29271bddbbaf215dd60420bcb80c7220
 F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
@@ -642,7 +642,7 @@ F src/shell.c.in 2c02c819349de410d63fcc0217763dfe5a42dbe58f2d68046d4ea8a376d12c2
 F src/sqlite.h.in 3076d78836b6dac53b3ab0875fc8fd15bca8077aad4d33c85336e05af6aef8c7
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
 F src/sqlite3ext.h da473ce2b3d0ae407a6300c4a164589b9a6bfdbec9462688a8593ff16f3bb6e4
-F src/sqliteInt.h b677ba33397479f9a2fa1223fcd24b561cc8c77c7d073798f7b7118e15d69dbb
+F src/sqliteInt.h 6ef127217c54e4707b1ca500508340542ca3c2a5aa08ee7a00aaa4834e68992d
 F src/sqliteLimit.h 33b1c9baba578d34efe7dfdb43193b366111cdf41476b1e82699e14c11ee1fb6
 F src/status.c 160c445d7d28c984a0eae38c144f6419311ed3eace59b44ac6dafc20db4af749
 F src/table.c 0f141b58a16de7e2fbe81c308379e7279f4c6b50eb08efeec5892794a0ba30d1
@@ -705,7 +705,7 @@ F src/trigger.c ad6ab9452715fa9a8075442e15196022275b414b9141b566af8cdb7a1605f2b0
 F src/update.c 0aa36561167a7c40d01163238c297297962f31a15a8d742216b3c37cdf25f731
 F src/upsert.c 5303dc6c518fa7d4b280ec65170f465c7a70b7ac2b22491598f6d0b4875b3145
 F src/utf.c ee39565f0843775cc2c81135751ddd93eceb91a673ea2c57f61c76f288b041a0
-F src/util.c 4264102045fdb36e9af3ff361e390a5f7a76342a2bd7069e55d8ad332026d6b5
+F src/util.c 447fd1d981bab37788397c24f980ce555438168f28badde1227441f6d67f1214
 F src/vacuum.c 604fcdaebe76f3497c855afcbf91b8fa5046b32de3045bab89cc008d68e40104
 F src/vdbe.c 74282a947234513872a83b0bab1b8c644ece64b3e27b053ef17677c8ff9c81e0
 F src/vdbe.h 41485521f68e9437fdb7ec4a90f9d86ab294e9bb8281e33b235915e29122cfc0
@@ -2041,9 +2041,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P f936f101406069b29218c89a36581b4497226fb61906782ea368f12d943c901c 4e8718dc35dbbaf75f17265a88d14acd9750dc75efbadf41377f9c97e732009c
-R 4da01a7efae23c104b98c2eba70ec2ef
-T +closed 4e8718dc35dbbaf75f17265a88d14acd9750dc75efbadf41377f9c97e732009c
-U dan
-Z 8ca5997f8884b68f398b8d0f077d59ae
+P 7afad1f759f7ceda873c6d869422fd56fe4399c2d24d47ad9bc3b84b06d830d1
+R b84c58ae5f50c9a21c1125fd73d7f10d
+T *branch * fp-to-decimal-refactor
+T *sym-fp-to-decimal-refactor *
+T -sym-trunk *
+U drh
+Z aad0befdc05a87e7f362b0543d2a6962
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-7afad1f759f7ceda873c6d869422fd56fe4399c2d24d47ad9bc3b84b06d830d1
+e923405e448385085224f9289991b303d86b02763535ea77d6fcee98ba6fc1f2

src/func.c

@@ -2371,6 +2371,23 @@ static void signFunc(
   sqlite3_result_int(context, x<0.0 ? -1 : x>0.0 ? +1 : 0);
 }
 
+
+#if 1 /* Temporary prototyping logic */
+static void fpdecodeFunc(
+  sqlite3_context *context,
+  int argc,
+  sqlite3_value **argv
+){
+  double r = sqlite3_value_double(argv[0]);
+  FpDecode s;
+  char zBuf[50];
+  UNUSED_PARAMETER(argc);
+  sqlite3FpDecode(&s, r);
+  sqlite3_snprintf(sizeof(zBuf), zBuf, "%c%.*s/%d", s.sign, s.n, s.z, s.iDP);
+  sqlite3_result_text(context, zBuf, -1, SQLITE_TRANSIENT);
+}
+#endif /* Temporary prototyping logic */
+
 /*
 ** All of the FuncDef structures in the aBuiltinFunc[] array above
 ** to the global function hash table.  This occurs at start-time (as
@@ -2442,6 +2459,11 @@ void sqlite3RegisterBuiltinFunctions(void){
     FUNCTION(unicode,            1, 0, 0, unicodeFunc      ),
     FUNCTION(char,              -1, 0, 0, charFunc         ),
     FUNCTION(abs,                1, 0, 0, absFunc          ),
+
+#if 1  /* Temporary prototyping function */
+    FUNCTION(fpdecode,           1, 0, 0, fpdecodeFunc     ),
+#endif
+  
 #ifndef SQLITE_OMIT_FLOATING_POINT
     FUNCTION(round,              1, 0, 0, roundFunc        ),
     FUNCTION(round,              2, 0, 0, roundFunc        ),

src/sqliteInt.h

@@ -1239,6 +1239,7 @@ typedef struct Schema Schema;
 typedef struct Expr Expr;
 typedef struct ExprList ExprList;
 typedef struct FKey FKey;
+typedef struct FpDecode FpDecode;
 typedef struct FuncDestructor FuncDestructor;
 typedef struct FuncDef FuncDef;
 typedef struct FuncDefHash FuncDefHash;
@@ -4597,6 +4598,20 @@ struct PrintfArguments {
   sqlite3_value **apArg;   /* The argument values */
 };
 
+/*
+** An instance of this object receives the decoding of a floating point
+** value into an approximate decimal representation.
+*/
+struct FpDecode {
+  char sign;           /* '+' or '-' */
+  char isNan;          /* True if not-a-number */
+  char isInf;          /* True if infinity */
+  int n;               /* Significant digits in the decode */
+  int iDP;             /* Location of the decimal point */
+  char z[24];          /* Significiant digits */
+};
+
+void sqlite3FpDecode(FpDecode*,double);
 char *sqlite3MPrintf(sqlite3*,const char*, ...);
 char *sqlite3VMPrintf(sqlite3*,const char*, va_list);
 #if defined(SQLITE_DEBUG) || defined(SQLITE_HAVE_OS_TRACE)

src/util.c

@@ -928,6 +928,69 @@ int sqlite3Atoi(const char *z){
   return x;
 }
 
+/*
+** Decode a floating-point value into an approximate decimal
+** representation.
+*/
+void sqlite3FpDecode(FpDecode *p, double r){
+  int i;
+  u64 v;
+  int e, exp = 0;
+  if( r<0.0 ){
+    p->sign = '-';
+    r = -r;
+  }else if( r==0.0 ){
+    p->sign = '+';
+    p->n = 1;
+    p->iDP = 1;
+    p->z[0] = '0';
+    return;
+  }else{
+    p->sign = '+';
+  }
+  memcpy(&v,&r,8);
+  e = v>>52;
+  if( e==0x7ff ){
+    if( v==0x7ff0000000000000L ){
+      p->isInf = 1;
+      p->isNan = 0;
+      p->z[0] = 'I';
+      p->z[1] = 'n';
+      p->z[2] = 'f';
+    }else{
+      p->isInf = 0;
+      p->isNan = 1;
+      p->z[0] = 'N';
+      p->z[1] = 'a';
+      p->z[2] = 'N';
+    }
+    p->n = 3;
+    p->iDP = 3;
+    return;
+  }
+  /* At this point, r is positive (non-zero) and is not Inf or NaN.
+  ** The strategy is to multiple or divide r by powers of 10 until
+  ** it is in between 1.0e+17 and 1.0e+19.  Then convert r into
+  ** an unsigned 64-bit integer v, and extract digits from v.
+  */
+  if( r>=1.0e+19 ){
+    while( r>=1.0e+119 ){ exp+=100; r /= 1.0e+100; }
+    while( r>=1.0e+29  ){ exp+=10;  r /= 1.0e+10;  }
+    while( r>=1.0e+19  ){ exp++;    r /= 10.0;     }
+  }else if( r<1.0e+17 ){
+    while( r<1.0e-97   ){ exp-=100; r *= 1.0e+100; }
+    while( r<1.0e+07   ){ exp-=10;  r *= 1.0e+10;  }
+    while( r<1.0e+17   ){ exp--;    r *= 10.0;     }
+  }
+  v = (u64)r;
+  i = sizeof(p->z);
+  while( v ){  p->z[i--] = (v%10) + '0'; v /= 10; }
+  p->n = sizeof(p->z) - i;
+  p->iDP = p->n + exp;
+  memmove(p->z, &p->z[i+1], p->n);
+  while( p->n>0 && p->z[p->n-1]=='0' ){ p->n--; }
+}
+
 /*
 ** Try to convert z into an unsigned 32-bit integer.  Return true on
 ** success and false if there is an error.