Performance optimization in jsonAppendString().

FossilOrigin-Name: fdf00e96239c73fb67e2acecc5b95f55a1fc51c3deed4512613c0d6070ce5805

manifest

@@ -1,5 +1,5 @@
-C Simplification\sand\soptimization\sof\sthe\sJSON\sparser.
+C Performance\soptimization\sin\sjsonAppendString().
-D 2023-12-02T13:36:52.119
+D 2023-12-02T14:16:47.613
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -688,7 +688,7 @@ F src/hash.h 3340ab6e1d13e725571d7cee6d3e3135f0779a7d8e76a9ce0a85971fa3953c51
 F src/hwtime.h f9c2dfb84dce7acf95ce6d289e46f5f9d3d1afd328e53da8f8e9008e3b3caae6
 F src/in-operator.md 10cd8f4bcd225a32518407c2fb2484089112fd71
 F src/insert.c 3f0a94082d978bbdd33c38fefea15346c6c6bffb70bc645a71dc0f1f87dd3276
-F src/json.c 73558b9dca8f326045c42350bd8274c9a9a6489cdb145b2208a8fc7e50a04247
+F src/json.c a3eabd185cfd13250503ac8a17ac3ec61c9bb88730f99134de9df6c9a3446d46
 F src/legacy.c d7874bc885906868cd51e6c2156698f2754f02d9eee1bae2d687323c3ca8e5aa
 F src/loadext.c 7432c944ff197046d67a1207790a1b13eec4548c85a9457eb0896bb3641dfb36
 F src/main.c 1b89f3de98d1b59fec5bac1d66d6ece21f703821b8eaa0d53d9604c35309f6f9
@@ -2145,8 +2145,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P a6dc29e4d5e13949e0fcd9d5dde575c2670eb10a230ab9df3806fc8c3016c540
+P f5ec9485119a2a6cb33eb864c7ca9b41d4a2ed08ab6ad9a6b0dd9358ab253576
-R d65ba1fc2a2f76e7b171a7dc72bb1070
+R a5df9ac2834f12883789ae2220af8e65
 U drh
-Z b0de3fe3c23565cae5077bfe62fcd8b8
+Z f68f81753669c00bcaaaadfbdd6d3188
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-f5ec9485119a2a6cb33eb864c7ca9b41d4a2ed08ab6ad9a6b0dd9358ab253576
+fdf00e96239c73fb67e2acecc5b95f55a1fc51c3deed4512613c0d6070ce5805

src/json.c

@@ -595,17 +595,33 @@ static void jsonAppendSeparator(JsonString *p){
 ** string.
 */
 static void jsonAppendString(JsonString *p, const char *zIn, u32 N){
-  u32 i;
+  u32 k;
-  if( zIn==0 ) return;
+  u8 c;
+  const u8 *z = (const u8*)zIn;
+  if( z==0 ) return;
   if( (N+p->nUsed+2 >= p->nAlloc) && jsonStringGrow(p,N+2)!=0 ) return;
   p->zBuf[p->nUsed++] = '"';
-  for(i=0; i<N; i++){
+  while( 1 /*exit-by-break*/ ){
-    unsigned char c = ((unsigned const char*)zIn)[i];
+    k = 0;
-    if( jsonIsOk[c] ){
+    while( k<N-1 && jsonIsOk[z[k]] && jsonIsOk[z[k+1]] ){ k += 2; }
-      p->zBuf[p->nUsed++] = c;
+    while( k<N && jsonIsOk[z[k]] ){ k++; }
-    }else if( c=='"' || c=='\\' ){
+    if( k>=N ){
+      if( k>0 ){
+        memcpy(&p->zBuf[p->nUsed], z, k);
+        p->nUsed += k;
+      }
+      break;
+    }
+    if( k>0 ){
+      memcpy(&p->zBuf[p->nUsed], z, k);
+      p->nUsed += k;
+      z += k;
+      N -= k;
+    }
+    c = z[0];
+    if( c=='"' || c=='\\' ){
       json_simple_escape:
-      if( (p->nUsed+N+3-i > p->nAlloc) && jsonStringGrow(p,N+3-i)!=0 ) return;
+      if( (p->nUsed+N+3 > p->nAlloc) && jsonStringGrow(p,N+3)!=0 ) return;
       p->zBuf[p->nUsed++] = '\\';
       p->zBuf[p->nUsed++] = c;
     }else if( c=='\'' ){
@@ -626,7 +642,7 @@ static void jsonAppendString(JsonString *p, const char *zIn, u32 N){
         c = aSpecial[c];
         goto json_simple_escape;
       }
-      if( (p->nUsed+N+7+i > p->nAlloc) && jsonStringGrow(p,N+7-i)!=0 ) return;
+      if( (p->nUsed+N+7 > p->nAlloc) && jsonStringGrow(p,N+7)!=0 ) return;
       p->zBuf[p->nUsed++] = '\\';
       p->zBuf[p->nUsed++] = 'u';
       p->zBuf[p->nUsed++] = '0';
@@ -634,6 +650,8 @@ static void jsonAppendString(JsonString *p, const char *zIn, u32 N){
       p->zBuf[p->nUsed++] = "0123456789abcdef"[c>>4];
       p->zBuf[p->nUsed++] = "0123456789abcdef"[c&0xf];
     }
+    z++;
+    N--;
   }
   p->zBuf[p->nUsed++] = '"';
   assert( p->nUsed<p->nAlloc );