Extend the json-path mechanism with array indexes of the form "#" or "#-n" for

some positive number "n", to reference the end of an array.

FossilOrigin-Name: 35ed68a651f4cf8740597433b0f1c3b345841868022e0904e9f342840ba0e502

1 files changed, 36 insertions, 5 deletions

diff --git a/ext/misc/json1.c b/ext/misc/json1.c
index 82bffe874..012ac4a89 100644
--- a/ext/misc/json1.c
+++ b/ext/misc/json1.c
@@ -1176,18 +1176,49 @@ static JsonNode *jsonLookupStep(
       }
       return pNode;
     }
-  }else if( zPath[0]=='[' && safe_isdigit(zPath[1]) ){
-    if( pRoot->eType!=JSON_ARRAY ) return 0;
+  }else if( zPath[0]=='[' ){
     i = 0;
     j = 1;
     while( safe_isdigit(zPath[j]) ){
       i = i*10 + zPath[j] - '0';
       j++;
     }
-    if( zPath[j]!=']' ){
-      *pzErr = zPath;
-      return 0;
+    if( j<2 || zPath[j]!=']' ){
+      if( zPath[1]=='#' ){
+        JsonNode *pBase = pRoot;
+        int iBase = iRoot;
+        if( pRoot->eType!=JSON_ARRAY ) return 0;
+        for(;;){
+          while( j<=pBase->n ){
+            if( (pBase[j].jnFlags & JNODE_REMOVE)==0 ) i++;
+            j += jsonNodeSize(&pBase[j]);
+          }
+          if( (pBase->jnFlags & JNODE_APPEND)==0 ) break;
+          iBase += pBase->u.iAppend;
+          pBase = &pParse->aNode[iBase];
+          j = 1;
+        }
+        j = 2;
+        if( zPath[2]=='-' && safe_isdigit(zPath[3]) ){
+          unsigned int x = 0;
+          j = 3;
+          do{
+            x = x*10 + zPath[j] - '0';
+            j++;
+          }while( safe_isdigit(zPath[j]) );
+          if( x>i ) return 0;
+          i -= x;
+        }
+        if( zPath[j]!=']' ){
+          *pzErr = zPath;
+          return 0;
+        }
+      }else{
+        *pzErr = zPath;
+        return 0;
+      }
     }
+    if( pRoot->eType!=JSON_ARRAY ) return 0;
     zPath += j + 1;
     j = 1;
     for(;;){