Further simplification, performance gain, and size reduction in

sqlite3FpDecode().

FossilOrigin-Name: 5954f22ceb6b43ed160ec085cd86b66299d8aab3e349a41941a4f1c2eade7457

diff --git a/manifest b/manifest
index d449f79dbe3ad6c81e0b20cfae6a848f5c9d2568..d6092d9986acac9320040710f3c0751ad4e2dc66 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Small\sperformance\sincrease\sand\ssize\sreduction\sin\ssqlite3FpDecode()\sby\susing\nlocal\svariables\sinstead\sof\sstructure\selements.
-D 2026-02-21T00:20:29.013
+C Further\ssimplification,\sperformance\sgain,\sand\ssize\sreduction\sin\nsqlite3FpDecode().
+D 2026-02-21T00:56:11.032
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -803,7 +803,7 @@ F src/trigger.c a40440614bdf523090cc07223f4878f7e3c892bcd1a13afe18f90190daa5945d
 F src/update.c 3e5e7ff66fa19ebe4d1b113d480639a24cc1175adbefabbd1a948a07f28e37cf
 F src/upsert.c 215328c3f91623c520ec8672c44323553f12caeb4f01b1090ebdca99fdf7b4f1
 F src/utf.c 7267c3fb9e2467020507601af3354c2446c61f444387e094c779dccd5ca62165
-F src/util.c 2578230d8c15e11cb86b7e6c4c069e5ea880a058d1d9aa25887fb607ac6942cd
+F src/util.c 1aa25fd0e8a9e7e7038dc35576ca084ab1ce305808683ed9fc34c0a911cd7cfe
 F src/vacuum.c d3d35d8ae893d419ade5fa196d761a83bddcbb62137a1a157ae751ef38b26e82
 F src/vdbe.c 5328c99dd256ee8132383565a86e253543a85daccfd7477c52f20bac6b385a7f
 F src/vdbe.h 966d0677a540b7ea6549b7c4e1312fc0d830fce3a235a58c801f2cc31cf5ecf9
@@ -2195,8 +2195,8 @@ F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee
 F tool/warnings.sh d924598cf2f55a4ecbc2aeb055c10bd5f48114793e7ba25f9585435da29e7e98
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
 F tool/winmain.c 00c8fb88e365c9017db14c73d3c78af62194d9644feaf60e220ab0f411f3604c
-P 6d9c29123b6b143b0f7c8f5d018f170c72edfc5b1a4d67edd45e5552def2af6c
-R ab113b7f537cba0046252b74a0cfbdbd
+P b4c378bba582205aa676e45b21ffa17ad6199e2a017ec73cf41a0243f693b589
+R 2ba85f29f79912c10542f94e5fe0f51a
 U drh
-Z eb44db8829fa7401363a7a2fe662819e
+Z 6f74841077f4058908580abdb7a6af5c
 # Remove this line to create a well-formed Fossil manifest.

diff --git a/manifest.tags b/manifest.tags
index bec971799ff1b8ee641c166c7aeb22d12c785393..a43a9fc376dafc64575244908ecf3e05eb7d4099 100644 (file)
--- a/manifest.tags
+++ b/manifest.tags
@@ -1,2 +1,2 @@
-branch trunk
-tag trunk
+branch fp-performance-v2
+tag fp-performance-v2

diff --git a/manifest.uuid b/manifest.uuid
index fa0737e469654207af2a06730185daf0821d9771..26c7dc2690cbf3b5f42899070ddf5c532ef122e3 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-b4c378bba582205aa676e45b21ffa17ad6199e2a017ec73cf41a0243f693b589
+5954f22ceb6b43ed160ec085cd86b66299d8aab3e349a41941a4f1c2eade7457

diff --git a/src/util.c b/src/util.c
index e0de0abf07000d4e75310d273f83aa2f688ac0bf..ed98fcc59ff4e7a654d113b408b838282197eb0c 100644 (file)
--- a/src/util.c
+++ b/src/util.c
@@ -1174,13 +1174,14 @@ int sqlite3Atoi(const char *z){
 ** The p->z[] array is *not* zero-terminated.
 */
 void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
-  int i, n;
-  u64 v;
-  int e, exp = 0;
-  char *zBuf;
+  int i;               /* Index into zBuf[] where to put next character */
+  int n;               /* Number of digits */
+  u64 v;               /* mantissa */
+  int e, exp = 0;      /* Base-2 and base-10 exponent */
+  char *zBuf;          /* Local alias for p->zBuf */
+  char *z;             /* Local alias for p->z */
 
   p->isSpecial = 0;
-  p->z = p->zBuf;
   assert( mxRound>0 );
 
   /* Convert negative numbers to positive.  Deal with Infinity, 0.0, and
@@ -1203,6 +1204,7 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
     p->isSpecial = 1 + (v!=0x7ff0000000000000LL);
     p->n = 0;
     p->iDP = 0;
+    p->z = p->zBuf;
     return;
   }
   v &= 0x000fffffffffffffULL;
@@ -1216,7 +1218,9 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
   }
   sqlite3Fp2Convert10(v, e, (iRound<=0||iRound>=18)?18:iRound+1, &v, &exp);  
 
-  /* Extract significant digits. */
+  /* Extract significant digits, start at the right-most slot in p->zBuf
+  ** and working back to the right.  "i" keeps track of the next slot in
+  ** which to store a digit. */
   i = sizeof(p->zBuf)-1;
   zBuf = p->zBuf;
   assert( v>0 );
@@ -1233,7 +1237,7 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
     zBuf[i--] = v + '0';
   }
   assert( i>=0 && i<sizeof(p->zBuf)-1 );
-  n = sizeof(p->zBuf) - 1 - i;
+  n = sizeof(p->zBuf) - 1 - i;  /* Total number of digits extracted */
   assert( n>0 );
   assert( n<sizeof(p->zBuf) );
   testcase( n==sizeof(p->zBuf)-1 );
@@ -1247,8 +1251,8 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
       p->iDP++;
     }
   }
+  z = &zBuf[i+1];  /* z points to the first digit */
   if( iRound>0 && (iRound<n || n>mxRound) ){
-    char *z = &zBuf[i+1];
     if( iRound>mxRound ) iRound = mxRound;
     n = iRound;
     if( z[iRound]>='5' ){
@@ -1258,7 +1262,8 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
         if( z[j]<='9' ) break;
         z[j] = '0';
         if( j==0 ){
-          p->z[i--] = '1';
+          z--;
+          z[0] = '1';
           n++;
           p->iDP++;
           break;
@@ -1268,15 +1273,13 @@ void sqlite3FpDecode(FpDecode *p, double r, int iRound, int mxRound){
       }
     }
   }
-  p->z = &zBuf[i+1];
-  assert( i+n < sizeof(p->zBuf) );
   assert( n>0 );
-  zBuf = p->z;
-  while( zBuf[n-1]=='0' ){
+  while( z[n-1]=='0' ){
     n--;
     assert( n>0 );
   }
   p->n = n;
+  p->z = z;
 }
 
 /*