Refactor PLWriter in preparation for buffered-document change.

Currently, PLWriter (Position List Writer) creates a locally-owned
DataBuffer to write into.  This is necessary to support doclist
collection during tokenization, where there is no obvious buffer to
write output to, but is not necessary for the other users of PLWriter.
 This change adds a DLCollector (Doc List Collector) structure to
handle the tokenization case.

Also fix a potential memory leak in writeZeroSegment().  In case of
error from leafWriterStep(), the DataBuffer dl was being leaked. (CVS 3706)

FossilOrigin-Name: 1b9918e20767aebc9c1e7523027139e5fbc12688

ext/fts2/fts2.c

@@ -942,18 +942,44 @@ static void plwInit(PLWriter *pWriter, sqlite_int64 iDocid, DocListType iType){
   dataBufferInit(&pWriter->b, 0);
   plwReset(pWriter, iDocid, iType);
 }
-static PLWriter *plwNew(sqlite_int64 iDocid, DocListType iType){
-  PLWriter *pWriter = malloc(sizeof(PLWriter));
-  plwInit(pWriter, iDocid, iType);
-  return pWriter;
-}
 static void plwDestroy(PLWriter *pWriter){
   dataBufferDestroy(&pWriter->b);
   SCRAMBLE(pWriter);
 }
-static void plwDelete(PLWriter *pWriter){
-  plwDestroy(pWriter);
-  free(pWriter);
+
+/*******************************************************************/
+/* DLCollector wraps PLWriter and DLWriter to provide a
+** dynamically-allocated doclist area to use during tokenization.
+**
+** dlcNew - malloc up and initialize a collector.
+** dlcDelete - destroy a collector and all contained items.
+** dlcAddPos - append position and offset information.
+** dlcAddDoclist - add the collected doclist to the given buffer.
+*/
+typedef struct DLCollector {
+  PLWriter plw;
+} DLCollector;
+
+static void dlcAddDoclist(DLCollector *pCollector, DataBuffer *b){
+  DLWriter dlw;
+  dlwInit(&dlw, pCollector->plw.iType, b);
+  plwDlwAdd(&pCollector->plw, &dlw);
+  dlwDestroy(&dlw);
+}
+static void dlcAddPos(DLCollector *pCollector, int iColumn, int iPos,
+                      int iStartOffset, int iEndOffset){
+  plwAdd(&pCollector->plw, iColumn, iPos, iStartOffset, iEndOffset);
+}
+
+static DLCollector *dlcNew(sqlite_int64 iDocid, DocListType iType){
+  DLCollector *pCollector = malloc(sizeof(DLCollector));
+  plwInit(&pCollector->plw, iDocid, iType);
+  return pCollector;
+}
+static void dlcDelete(DLCollector *pCollector){
+  plwDestroy(&pCollector->plw);
+  SCRAMBLE(pCollector);
+  free(pCollector);
 }
 
 
@@ -3533,7 +3559,7 @@ static int buildTerms(fulltext_vtab *v, fts2Hash *terms, sqlite_int64 iDocid,
                                                &pToken, &nTokenBytes,
                                                &iStartOffset, &iEndOffset,
                                                &iPosition) ){
-    PLWriter *p;
+    DLCollector *p;
 
     /* Positions can't be negative; we use -1 as a terminator internally. */
     if( iPosition<0 ){
@@ -3543,11 +3569,11 @@ static int buildTerms(fulltext_vtab *v, fts2Hash *terms, sqlite_int64 iDocid,
 
     p = fts2HashFind(terms, pToken, nTokenBytes);
     if( p==NULL ){
-      p = plwNew(iDocid, DL_DEFAULT);
+      p = dlcNew(iDocid, DL_DEFAULT);
       fts2HashInsert(terms, pToken, nTokenBytes, p);
     }
     if( iColumn>=0 ){
-      plwAdd(p, iColumn, iPosition, iStartOffset, iEndOffset);
+      dlcAddPos(p, iColumn, iPosition, iStartOffset, iEndOffset);
     }
   }
 
@@ -5045,7 +5071,7 @@ static int termSelect(fulltext_vtab *v, int iColumn,
 typedef struct TermData {
   const char *pTerm;
   int nTerm;
-  PLWriter *pWriter;
+  DLCollector *pCollector;
 } TermData;
 
 /* Orders TermData elements in strcmp fashion ( <0 for less-than, 0
@@ -5081,7 +5107,7 @@ static int writeZeroSegment(fulltext_vtab *v, fts2Hash *pTerms){
     assert( i<n );
     pData[i].pTerm = fts2HashKey(e);
     pData[i].nTerm = fts2HashKeysize(e);
-    pData[i].pWriter = fts2HashData(e);
+    pData[i].pCollector = fts2HashData(e);
   }
   assert( i==n );
 
@@ -5096,19 +5122,16 @@ static int writeZeroSegment(fulltext_vtab *v, fts2Hash *pTerms){
   leafWriterInit(0, idx, &writer);
   dataBufferInit(&dl, 0);
   for(i=0; i<n; i++){
-    DLWriter dlw;
     dataBufferReset(&dl);
-    dlwInit(&dlw, DL_DEFAULT, &dl);
-    plwDlwAdd(pData[i].pWriter, &dlw);
+    dlcAddDoclist(pData[i].pCollector, &dl);
     rc = leafWriterStep(v, &writer,
                         pData[i].pTerm, pData[i].nTerm, dl.pData, dl.nData);
-    dlwDestroy(&dlw);
     if( rc!=SQLITE_OK ) goto err;
   }
-  dataBufferDestroy(&dl);
   rc = leafWriterFinalize(v, &writer);
 
  err:
+  dataBufferDestroy(&dl);
   free(pData);
   leafWriterDestroy(&writer);
   return rc;
@@ -5158,7 +5181,7 @@ static int fulltextUpdate(sqlite3_vtab *pVtab, int nArg, sqlite3_value **ppArg,
 
   /* clean up */
   for(e=fts2HashFirst(&terms); e; e=fts2HashNext(e)){
-    plwDelete(fts2HashData(e));
+    dlcDelete(fts2HashData(e));
   }
   fts2HashClear(&terms);