Adding upstream version 1.43.0.upstream/1.43.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 959 insertions, 0 deletions

diff --git a/database/sqlite/dbdata.c b/database/sqlite/dbdata.c
new file mode 100644
index 000000000..1ad742e04
--- /dev/null
+++ b/database/sqlite/dbdata.c
@@ -0,0 +1,959 @@
+/*
+** 2019-04-17
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+******************************************************************************
+**
+** This file contains an implementation of two eponymous virtual tables,
+** "sqlite_dbdata" and "sqlite_dbptr". Both modules require that the
+** "sqlite_dbpage" eponymous virtual table be available.
+**
+** SQLITE_DBDATA:
+**   sqlite_dbdata is used to extract data directly from a database b-tree
+**   page and its associated overflow pages, bypassing the b-tree layer.
+**   The table schema is equivalent to:
+**
+**     CREATE TABLE sqlite_dbdata(
+**       pgno INTEGER,
+**       cell INTEGER,
+**       field INTEGER,
+**       value ANY,
+**       schema TEXT HIDDEN
+**     );
+**
+**   IMPORTANT: THE VIRTUAL TABLE SCHEMA ABOVE IS SUBJECT TO CHANGE. IN THE
+**   FUTURE NEW NON-HIDDEN COLUMNS MAY BE ADDED BETWEEN "value" AND
+**   "schema".
+**
+**   Each page of the database is inspected. If it cannot be interpreted as
+**   a b-tree page, or if it is a b-tree page containing 0 entries, the
+**   sqlite_dbdata table contains no rows for that page.  Otherwise, the
+**   table contains one row for each field in the record associated with
+**   each cell on the page. For intkey b-trees, the key value is stored in
+**   field -1.
+**
+**   For example, for the database:
+**
+**     CREATE TABLE t1(a, b);     -- root page is page 2
+**     INSERT INTO t1(rowid, a, b) VALUES(5, 'v', 'five');
+**     INSERT INTO t1(rowid, a, b) VALUES(10, 'x', 'ten');
+**
+**   the sqlite_dbdata table contains, as well as from entries related to 
+**   page 1, content equivalent to:
+**
+**     INSERT INTO sqlite_dbdata(pgno, cell, field, value) VALUES
+**         (2, 0, -1, 5     ),
+**         (2, 0,  0, 'v'   ),
+**         (2, 0,  1, 'five'),
+**         (2, 1, -1, 10    ),
+**         (2, 1,  0, 'x'   ),
+**         (2, 1,  1, 'ten' );
+**
+**   If database corruption is encountered, this module does not report an
+**   error. Instead, it attempts to extract as much data as possible and
+**   ignores the corruption.
+**
+** SQLITE_DBPTR:
+**   The sqlite_dbptr table has the following schema:
+**
+**     CREATE TABLE sqlite_dbptr(
+**       pgno INTEGER,
+**       child INTEGER,
+**       schema TEXT HIDDEN
+**     );
+**
+**   It contains one entry for each b-tree pointer between a parent and
+**   child page in the database.
+*/
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#if !defined(SQLITEINT_H)
+#include "sqlite3.h"
+
+typedef unsigned char u8;
+typedef unsigned int u32;
+
+#endif
+#include <string.h>
+#include <assert.h>
+
+#ifndef SQLITE_OMIT_VIRTUALTABLE
+
+#define DBDATA_PADDING_BYTES 100 
+
+typedef struct DbdataTable DbdataTable;
+typedef struct DbdataCursor DbdataCursor;
+
+/* Cursor object */
+struct DbdataCursor {
+  sqlite3_vtab_cursor base;       /* Base class.  Must be first */
+  sqlite3_stmt *pStmt;            /* For fetching database pages */
+
+  int iPgno;                      /* Current page number */
+  u8 *aPage;                      /* Buffer containing page */
+  int nPage;                      /* Size of aPage[] in bytes */
+  int nCell;                      /* Number of cells on aPage[] */
+  int iCell;                      /* Current cell number */
+  int bOnePage;                   /* True to stop after one page */
+  int szDb;
+  sqlite3_int64 iRowid;
+
+  /* Only for the sqlite_dbdata table */
+  u8 *pRec;                       /* Buffer containing current record */
+  sqlite3_int64 nRec;             /* Size of pRec[] in bytes */
+  sqlite3_int64 nHdr;             /* Size of header in bytes */
+  int iField;                     /* Current field number */
+  u8 *pHdrPtr;
+  u8 *pPtr;
+  u32 enc;                        /* Text encoding */
+  
+  sqlite3_int64 iIntkey;          /* Integer key value */
+};
+
+/* Table object */
+struct DbdataTable {
+  sqlite3_vtab base;              /* Base class.  Must be first */
+  sqlite3 *db;                    /* The database connection */
+  sqlite3_stmt *pStmt;            /* For fetching database pages */
+  int bPtr;                       /* True for sqlite3_dbptr table */
+};
+
+/* Column and schema definitions for sqlite_dbdata */
+#define DBDATA_COLUMN_PGNO        0
+#define DBDATA_COLUMN_CELL        1
+#define DBDATA_COLUMN_FIELD       2
+#define DBDATA_COLUMN_VALUE       3
+#define DBDATA_COLUMN_SCHEMA      4
+#define DBDATA_SCHEMA             \
+      "CREATE TABLE x("           \
+      "  pgno INTEGER,"           \
+      "  cell INTEGER,"           \
+      "  field INTEGER,"          \
+      "  value ANY,"              \
+      "  schema TEXT HIDDEN"      \
+      ")"
+
+/* Column and schema definitions for sqlite_dbptr */
+#define DBPTR_COLUMN_PGNO         0
+#define DBPTR_COLUMN_CHILD        1
+#define DBPTR_COLUMN_SCHEMA       2
+#define DBPTR_SCHEMA              \
+      "CREATE TABLE x("           \
+      "  pgno INTEGER,"           \
+      "  child INTEGER,"          \
+      "  schema TEXT HIDDEN"      \
+      ")"
+
+/*
+** Connect to an sqlite_dbdata (pAux==0) or sqlite_dbptr (pAux!=0) virtual 
+** table.
+*/
+static int dbdataConnect(
+  sqlite3 *db,
+  void *pAux,
+  int argc, const char *const*argv,
+  sqlite3_vtab **ppVtab,
+  char **pzErr
+){
+  DbdataTable *pTab = 0;
+  int rc = sqlite3_declare_vtab(db, pAux ? DBPTR_SCHEMA : DBDATA_SCHEMA);
+
+  (void)argc;
+  (void)argv;
+  (void)pzErr;
+  sqlite3_vtab_config(db, SQLITE_VTAB_USES_ALL_SCHEMAS);
+  if( rc==SQLITE_OK ){
+    pTab = (DbdataTable*)sqlite3_malloc64(sizeof(DbdataTable));
+    if( pTab==0 ){
+      rc = SQLITE_NOMEM;
+    }else{
+      memset(pTab, 0, sizeof(DbdataTable));
+      pTab->db = db;
+      pTab->bPtr = (pAux!=0);
+    }
+  }
+
+  *ppVtab = (sqlite3_vtab*)pTab;
+  return rc;
+}
+
+/*
+** Disconnect from or destroy a sqlite_dbdata or sqlite_dbptr virtual table.
+*/
+static int dbdataDisconnect(sqlite3_vtab *pVtab){
+  DbdataTable *pTab = (DbdataTable*)pVtab;
+  if( pTab ){
+    sqlite3_finalize(pTab->pStmt);
+    sqlite3_free(pVtab);
+  }
+  return SQLITE_OK;
+}
+
+/*
+** This function interprets two types of constraints:
+**
+**       schema=?
+**       pgno=?
+**
+** If neither are present, idxNum is set to 0. If schema=? is present,
+** the 0x01 bit in idxNum is set. If pgno=? is present, the 0x02 bit
+** in idxNum is set.
+**
+** If both parameters are present, schema is in position 0 and pgno in
+** position 1.
+*/
+static int dbdataBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdx){
+  DbdataTable *pTab = (DbdataTable*)tab;
+  int i;
+  int iSchema = -1;
+  int iPgno = -1;
+  int colSchema = (pTab->bPtr ? DBPTR_COLUMN_SCHEMA : DBDATA_COLUMN_SCHEMA);
+
+  for(i=0; i<pIdx->nConstraint; i++){
+    struct sqlite3_index_constraint *p = &pIdx->aConstraint[i];
+    if( p->op==SQLITE_INDEX_CONSTRAINT_EQ ){
+      if( p->iColumn==colSchema ){
+        if( p->usable==0 ) return SQLITE_CONSTRAINT;
+        iSchema = i;
+      }
+      if( p->iColumn==DBDATA_COLUMN_PGNO && p->usable ){
+        iPgno = i;
+      }
+    }
+  }
+
+  if( iSchema>=0 ){
+    pIdx->aConstraintUsage[iSchema].argvIndex = 1;
+    pIdx->aConstraintUsage[iSchema].omit = 1;
+  }
+  if( iPgno>=0 ){
+    pIdx->aConstraintUsage[iPgno].argvIndex = 1 + (iSchema>=0);
+    pIdx->aConstraintUsage[iPgno].omit = 1;
+    pIdx->estimatedCost = 100;
+    pIdx->estimatedRows =  50;
+
+    if( pTab->bPtr==0 && pIdx->nOrderBy && pIdx->aOrderBy[0].desc==0 ){
+      int iCol = pIdx->aOrderBy[0].iColumn;
+      if( pIdx->nOrderBy==1 ){
+        pIdx->orderByConsumed = (iCol==0 || iCol==1);
+      }else if( pIdx->nOrderBy==2 && pIdx->aOrderBy[1].desc==0 && iCol==0 ){
+        pIdx->orderByConsumed = (pIdx->aOrderBy[1].iColumn==1);
+      }
+    }
+
+  }else{
+    pIdx->estimatedCost = 100000000;
+    pIdx->estimatedRows = 1000000000;
+  }
+  pIdx->idxNum = (iSchema>=0 ? 0x01 : 0x00) | (iPgno>=0 ? 0x02 : 0x00);
+  return SQLITE_OK;
+}
+
+/*
+** Open a new sqlite_dbdata or sqlite_dbptr cursor.
+*/
+static int dbdataOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+  DbdataCursor *pCsr;
+
+  pCsr = (DbdataCursor*)sqlite3_malloc64(sizeof(DbdataCursor));
+  if( pCsr==0 ){
+    return SQLITE_NOMEM;
+  }else{
+    memset(pCsr, 0, sizeof(DbdataCursor));
+    pCsr->base.pVtab = pVTab;
+  }
+
+  *ppCursor = (sqlite3_vtab_cursor *)pCsr;
+  return SQLITE_OK;
+}
+
+/*
+** Restore a cursor object to the state it was in when first allocated 
+** by dbdataOpen().
+*/
+static void dbdataResetCursor(DbdataCursor *pCsr){
+  DbdataTable *pTab = (DbdataTable*)(pCsr->base.pVtab);
+  if( pTab->pStmt==0 ){
+    pTab->pStmt = pCsr->pStmt;
+  }else{
+    sqlite3_finalize(pCsr->pStmt);
+  }
+  pCsr->pStmt = 0;
+  pCsr->iPgno = 1;
+  pCsr->iCell = 0;
+  pCsr->iField = 0;
+  pCsr->bOnePage = 0;
+  sqlite3_free(pCsr->aPage);
+  sqlite3_free(pCsr->pRec);
+  pCsr->pRec = 0;
+  pCsr->aPage = 0;
+}
+
+/*
+** Close an sqlite_dbdata or sqlite_dbptr cursor.
+*/
+static int dbdataClose(sqlite3_vtab_cursor *pCursor){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  dbdataResetCursor(pCsr);
+  sqlite3_free(pCsr);
+  return SQLITE_OK;
+}
+
+/* 
+** Utility methods to decode 16 and 32-bit big-endian unsigned integers. 
+*/
+static u32 get_uint16(unsigned char *a){
+  return (a[0]<<8)|a[1];
+}
+static u32 get_uint32(unsigned char *a){
+  return ((u32)a[0]<<24)
+       | ((u32)a[1]<<16)
+       | ((u32)a[2]<<8)
+       | ((u32)a[3]);
+}
+
+/*
+** Load page pgno from the database via the sqlite_dbpage virtual table.
+** If successful, set (*ppPage) to point to a buffer containing the page
+** data, (*pnPage) to the size of that buffer in bytes and return
+** SQLITE_OK. In this case it is the responsibility of the caller to
+** eventually free the buffer using sqlite3_free().
+**
+** Or, if an error occurs, set both (*ppPage) and (*pnPage) to 0 and
+** return an SQLite error code.
+*/
+static int dbdataLoadPage(
+  DbdataCursor *pCsr,             /* Cursor object */
+  u32 pgno,                       /* Page number of page to load */
+  u8 **ppPage,                    /* OUT: pointer to page buffer */
+  int *pnPage                     /* OUT: Size of (*ppPage) in bytes */
+){
+  int rc2;
+  int rc = SQLITE_OK;
+  sqlite3_stmt *pStmt = pCsr->pStmt;
+
+  *ppPage = 0;
+  *pnPage = 0;
+  if( pgno>0 ){
+    sqlite3_bind_int64(pStmt, 2, pgno);
+    if( SQLITE_ROW==sqlite3_step(pStmt) ){
+      int nCopy = sqlite3_column_bytes(pStmt, 0);
+      if( nCopy>0 ){
+        u8 *pPage;
+        pPage = (u8*)sqlite3_malloc64(nCopy + DBDATA_PADDING_BYTES);
+        if( pPage==0 ){
+          rc = SQLITE_NOMEM;
+        }else{
+          const u8 *pCopy = sqlite3_column_blob(pStmt, 0);
+          memcpy(pPage, pCopy, nCopy);
+          memset(&pPage[nCopy], 0, DBDATA_PADDING_BYTES);
+        }
+        *ppPage = pPage;
+        *pnPage = nCopy;
+      }
+    }
+    rc2 = sqlite3_reset(pStmt);
+    if( rc==SQLITE_OK ) rc = rc2;
+  }
+
+  return rc;
+}
+
+/*
+** Read a varint.  Put the value in *pVal and return the number of bytes.
+*/
+static int dbdataGetVarint(const u8 *z, sqlite3_int64 *pVal){
+  sqlite3_uint64 u = 0;
+  int i;
+  for(i=0; i<8; i++){
+    u = (u<<7) + (z[i]&0x7f);
+    if( (z[i]&0x80)==0 ){ *pVal = (sqlite3_int64)u; return i+1; }
+  }
+  u = (u<<8) + (z[i]&0xff);
+  *pVal = (sqlite3_int64)u;
+  return 9;
+}
+
+/*
+** Like dbdataGetVarint(), but set the output to 0 if it is less than 0
+** or greater than 0xFFFFFFFF. This can be used for all varints in an
+** SQLite database except for key values in intkey tables.
+*/
+static int dbdataGetVarintU32(const u8 *z, sqlite3_int64 *pVal){
+  sqlite3_int64 val;
+  int nRet = dbdataGetVarint(z, &val);
+  if( val<0 || val>0xFFFFFFFF ) val = 0;
+  *pVal = val;
+  return nRet;
+}
+
+/*
+** Return the number of bytes of space used by an SQLite value of type
+** eType.
+*/
+static int dbdataValueBytes(int eType){
+  switch( eType ){
+    case 0: case 8: case 9:
+    case 10: case 11:
+      return 0;
+    case 1:
+      return 1;
+    case 2:
+      return 2;
+    case 3:
+      return 3;
+    case 4:
+      return 4;
+    case 5:
+      return 6;
+    case 6:
+    case 7:
+      return 8;
+    default:
+      if( eType>0 ){
+        return ((eType-12) / 2);
+      }
+      return 0;
+  }
+}
+
+/*
+** Load a value of type eType from buffer pData and use it to set the
+** result of context object pCtx.
+*/
+static void dbdataValue(
+  sqlite3_context *pCtx, 
+  u32 enc,
+  int eType, 
+  u8 *pData,
+  sqlite3_int64 nData
+){
+  if( eType>=0 && dbdataValueBytes(eType)<=nData ){
+    switch( eType ){
+      case 0: 
+      case 10: 
+      case 11: 
+        sqlite3_result_null(pCtx);
+        break;
+      
+      case 8: 
+        sqlite3_result_int(pCtx, 0);
+        break;
+      case 9:
+        sqlite3_result_int(pCtx, 1);
+        break;
+  
+      case 1: case 2: case 3: case 4: case 5: case 6: case 7: {
+        sqlite3_uint64 v = (signed char)pData[0];
+        pData++;
+        switch( eType ){
+          case 7:
+          case 6:  v = (v<<16) + (pData[0]<<8) + pData[1];  pData += 2;
+          case 5:  v = (v<<16) + (pData[0]<<8) + pData[1];  pData += 2;
+          case 4:  v = (v<<8) + pData[0];  pData++;
+          case 3:  v = (v<<8) + pData[0];  pData++;
+          case 2:  v = (v<<8) + pData[0];  pData++;
+        }
+  
+        if( eType==7 ){
+          double r;
+          memcpy(&r, &v, sizeof(r));
+          sqlite3_result_double(pCtx, r);
+        }else{
+          sqlite3_result_int64(pCtx, (sqlite3_int64)v);
+        }
+        break;
+      }
+  
+      default: {
+        int n = ((eType-12) / 2);
+        if( eType % 2 ){
+          switch( enc ){
+#ifndef SQLITE_OMIT_UTF16
+            case SQLITE_UTF16BE:
+              sqlite3_result_text16be(pCtx, (void*)pData, n, SQLITE_TRANSIENT);
+              break;
+            case SQLITE_UTF16LE:
+              sqlite3_result_text16le(pCtx, (void*)pData, n, SQLITE_TRANSIENT);
+              break;
+#endif
+            default:
+              sqlite3_result_text(pCtx, (char*)pData, n, SQLITE_TRANSIENT);
+              break;
+          }
+        }else{
+          sqlite3_result_blob(pCtx, pData, n, SQLITE_TRANSIENT);
+        }
+      }
+    }
+  }
+}
+
+/*
+** Move an sqlite_dbdata or sqlite_dbptr cursor to the next entry.
+*/
+static int dbdataNext(sqlite3_vtab_cursor *pCursor){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
+
+  pCsr->iRowid++;
+  while( 1 ){
+    int rc;
+    int iOff = (pCsr->iPgno==1 ? 100 : 0);
+    int bNextPage = 0;
+
+    if( pCsr->aPage==0 ){
+      while( 1 ){
+        if( pCsr->bOnePage==0 && pCsr->iPgno>pCsr->szDb ) return SQLITE_OK;
+        rc = dbdataLoadPage(pCsr, pCsr->iPgno, &pCsr->aPage, &pCsr->nPage);
+        if( rc!=SQLITE_OK ) return rc;
+        if( pCsr->aPage && pCsr->nPage>=256 ) break;
+        sqlite3_free(pCsr->aPage);
+        pCsr->aPage = 0;
+        if( pCsr->bOnePage ) return SQLITE_OK;
+        pCsr->iPgno++;
+      }
+
+      assert( iOff+3+2<=pCsr->nPage );
+      pCsr->iCell = pTab->bPtr ? -2 : 0;
+      pCsr->nCell = get_uint16(&pCsr->aPage[iOff+3]);
+    }
+
+    if( pTab->bPtr ){
+      if( pCsr->aPage[iOff]!=0x02 && pCsr->aPage[iOff]!=0x05 ){
+        pCsr->iCell = pCsr->nCell;
+      }
+      pCsr->iCell++;
+      if( pCsr->iCell>=pCsr->nCell ){
+        sqlite3_free(pCsr->aPage);
+        pCsr->aPage = 0;
+        if( pCsr->bOnePage ) return SQLITE_OK;
+        pCsr->iPgno++;
+      }else{
+        return SQLITE_OK;
+      }
+    }else{
+      /* If there is no record loaded, load it now. */
+      if( pCsr->pRec==0 ){
+        int bHasRowid = 0;
+        int nPointer = 0;
+        sqlite3_int64 nPayload = 0;
+        sqlite3_int64 nHdr = 0;
+        int iHdr;
+        int U, X;
+        int nLocal;
+  
+        switch( pCsr->aPage[iOff] ){
+          case 0x02:
+            nPointer = 4;
+            break;
+          case 0x0a:
+            break;
+          case 0x0d:
+            bHasRowid = 1;
+            break;
+          default:
+            /* This is not a b-tree page with records on it. Continue. */
+            pCsr->iCell = pCsr->nCell;
+            break;
+        }
+
+        if( pCsr->iCell>=pCsr->nCell ){
+          bNextPage = 1;
+        }else{
+  
+          iOff += 8 + nPointer + pCsr->iCell*2;
+          if( iOff>pCsr->nPage ){
+            bNextPage = 1;
+          }else{
+            iOff = get_uint16(&pCsr->aPage[iOff]);
+          }
+    
+          /* For an interior node cell, skip past the child-page number */
+          iOff += nPointer;
+    
+          /* Load the "byte of payload including overflow" field */
+          if( bNextPage || iOff>pCsr->nPage ){
+            bNextPage = 1;
+          }else{
+            iOff += dbdataGetVarintU32(&pCsr->aPage[iOff], &nPayload);
+          }
+    
+          /* If this is a leaf intkey cell, load the rowid */
+          if( bHasRowid && !bNextPage && iOff<pCsr->nPage ){
+            iOff += dbdataGetVarint(&pCsr->aPage[iOff], &pCsr->iIntkey);
+          }
+    
+          /* Figure out how much data to read from the local page */
+          U = pCsr->nPage;
+          if( bHasRowid ){
+            X = U-35;
+          }else{
+            X = ((U-12)*64/255)-23;
+          }
+          if( nPayload<=X ){
+            nLocal = nPayload;
+          }else{
+            int M, K;
+            M = ((U-12)*32/255)-23;
+            K = M+((nPayload-M)%(U-4));
+            if( K<=X ){
+              nLocal = K;
+            }else{
+              nLocal = M;
+            }
+          }
+
+          if( bNextPage || nLocal+iOff>pCsr->nPage ){
+            bNextPage = 1;
+          }else{
+
+            /* Allocate space for payload. And a bit more to catch small buffer
+            ** overruns caused by attempting to read a varint or similar from 
+            ** near the end of a corrupt record.  */
+            pCsr->pRec = (u8*)sqlite3_malloc64(nPayload+DBDATA_PADDING_BYTES);
+            if( pCsr->pRec==0 ) return SQLITE_NOMEM;
+            memset(pCsr->pRec, 0, nPayload+DBDATA_PADDING_BYTES);
+            pCsr->nRec = nPayload;
+
+            /* Load the nLocal bytes of payload */
+            memcpy(pCsr->pRec, &pCsr->aPage[iOff], nLocal);
+            iOff += nLocal;
+
+            /* Load content from overflow pages */
+            if( nPayload>nLocal ){
+              sqlite3_int64 nRem = nPayload - nLocal;
+              u32 pgnoOvfl = get_uint32(&pCsr->aPage[iOff]);
+              while( nRem>0 ){
+                u8 *aOvfl = 0;
+                int nOvfl = 0;
+                int nCopy;
+                rc = dbdataLoadPage(pCsr, pgnoOvfl, &aOvfl, &nOvfl);
+                assert( rc!=SQLITE_OK || aOvfl==0 || nOvfl==pCsr->nPage );
+                if( rc!=SQLITE_OK ) return rc;
+                if( aOvfl==0 ) break;
+
+                nCopy = U-4;
+                if( nCopy>nRem ) nCopy = nRem;
+                memcpy(&pCsr->pRec[nPayload-nRem], &aOvfl[4], nCopy);
+                nRem -= nCopy;
+
+                pgnoOvfl = get_uint32(aOvfl);
+                sqlite3_free(aOvfl);
+              }
+            }
+    
+            iHdr = dbdataGetVarintU32(pCsr->pRec, &nHdr);
+            if( nHdr>nPayload ) nHdr = 0;
+            pCsr->nHdr = nHdr;
+            pCsr->pHdrPtr = &pCsr->pRec[iHdr];
+            pCsr->pPtr = &pCsr->pRec[pCsr->nHdr];
+            pCsr->iField = (bHasRowid ? -1 : 0);
+          }
+        }
+      }else{
+        pCsr->iField++;
+        if( pCsr->iField>0 ){
+          sqlite3_int64 iType;
+          if( pCsr->pHdrPtr>&pCsr->pRec[pCsr->nRec] ){
+            bNextPage = 1;
+          }else{
+            int szField = 0;
+            pCsr->pHdrPtr += dbdataGetVarintU32(pCsr->pHdrPtr, &iType);
+            szField = dbdataValueBytes(iType);
+            if( (pCsr->nRec - (pCsr->pPtr - pCsr->pRec))<szField ){
+              pCsr->pPtr = &pCsr->pRec[pCsr->nRec];
+            }else{
+              pCsr->pPtr += szField;
+            }
+          }
+        }
+      }
+
+      if( bNextPage ){
+        sqlite3_free(pCsr->aPage);
+        sqlite3_free(pCsr->pRec);
+        pCsr->aPage = 0;
+        pCsr->pRec = 0;
+        if( pCsr->bOnePage ) return SQLITE_OK;
+        pCsr->iPgno++;
+      }else{
+        if( pCsr->iField<0 || pCsr->pHdrPtr<&pCsr->pRec[pCsr->nHdr] ){
+          return SQLITE_OK;
+        }
+
+        /* Advance to the next cell. The next iteration of the loop will load
+        ** the record and so on. */
+        sqlite3_free(pCsr->pRec);
+        pCsr->pRec = 0;
+        pCsr->iCell++;
+      }
+    }
+  }
+
+  assert( !"can't get here" );
+  return SQLITE_OK;
+}
+
+/* 
+** Return true if the cursor is at EOF.
+*/
+static int dbdataEof(sqlite3_vtab_cursor *pCursor){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  return pCsr->aPage==0;
+}
+
+/*
+** Return true if nul-terminated string zSchema ends in "()". Or false
+** otherwise.
+*/
+static int dbdataIsFunction(const char *zSchema){
+  size_t n = strlen(zSchema);
+  if( n>2 && zSchema[n-2]=='(' && zSchema[n-1]==')' ){
+    return (int)n-2;
+  }
+  return 0;
+}
+
+/* 
+** Determine the size in pages of database zSchema (where zSchema is
+** "main", "temp" or the name of an attached database) and set 
+** pCsr->szDb accordingly. If successful, return SQLITE_OK. Otherwise,
+** an SQLite error code.
+*/
+static int dbdataDbsize(DbdataCursor *pCsr, const char *zSchema){
+  DbdataTable *pTab = (DbdataTable*)pCsr->base.pVtab;
+  char *zSql = 0;
+  int rc, rc2;
+  int nFunc = 0;
+  sqlite3_stmt *pStmt = 0;
+
+  if( (nFunc = dbdataIsFunction(zSchema))>0 ){
+    zSql = sqlite3_mprintf("SELECT %.*s(0)", nFunc, zSchema);
+  }else{
+    zSql = sqlite3_mprintf("PRAGMA %Q.page_count", zSchema);
+  }
+  if( zSql==0 ) return SQLITE_NOMEM;
+
+  rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pStmt, 0);
+  sqlite3_free(zSql);
+  if( rc==SQLITE_OK && sqlite3_step(pStmt)==SQLITE_ROW ){
+    pCsr->szDb = sqlite3_column_int(pStmt, 0);
+  }
+  rc2 = sqlite3_finalize(pStmt);
+  if( rc==SQLITE_OK ) rc = rc2;
+  return rc;
+}
+
+/*
+** Attempt to figure out the encoding of the database by retrieving page 1
+** and inspecting the header field. If successful, set the pCsr->enc variable
+** and return SQLITE_OK. Otherwise, return an SQLite error code.
+*/
+static int dbdataGetEncoding(DbdataCursor *pCsr){
+  int rc = SQLITE_OK;
+  int nPg1 = 0;
+  u8 *aPg1 = 0;
+  rc = dbdataLoadPage(pCsr, 1, &aPg1, &nPg1);
+  if( rc==SQLITE_OK && nPg1>=(56+4) ){
+    pCsr->enc = get_uint32(&aPg1[56]);
+  }
+  sqlite3_free(aPg1);
+  return rc;
+}
+
+
+/* 
+** xFilter method for sqlite_dbdata and sqlite_dbptr.
+*/
+static int dbdataFilter(
+  sqlite3_vtab_cursor *pCursor, 
+  int idxNum, const char *idxStr,
+  int argc, sqlite3_value **argv
+){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
+  int rc = SQLITE_OK;
+  const char *zSchema = "main";
+  (void)idxStr;
+  (void)argc;
+
+  dbdataResetCursor(pCsr);
+  assert( pCsr->iPgno==1 );
+  if( idxNum & 0x01 ){
+    zSchema = (const char*)sqlite3_value_text(argv[0]);
+    if( zSchema==0 ) zSchema = "";
+  }
+  if( idxNum & 0x02 ){
+    pCsr->iPgno = sqlite3_value_int(argv[(idxNum & 0x01)]);
+    pCsr->bOnePage = 1;
+  }else{
+    rc = dbdataDbsize(pCsr, zSchema);
+  }
+
+  if( rc==SQLITE_OK ){
+    int nFunc = 0;
+    if( pTab->pStmt ){
+      pCsr->pStmt = pTab->pStmt;
+      pTab->pStmt = 0;
+    }else if( (nFunc = dbdataIsFunction(zSchema))>0 ){
+      char *zSql = sqlite3_mprintf("SELECT %.*s(?2)", nFunc, zSchema);
+      if( zSql==0 ){
+        rc = SQLITE_NOMEM;
+      }else{
+        rc = sqlite3_prepare_v2(pTab->db, zSql, -1, &pCsr->pStmt, 0);
+        sqlite3_free(zSql);
+      }
+    }else{
+      rc = sqlite3_prepare_v2(pTab->db, 
+          "SELECT data FROM sqlite_dbpage(?) WHERE pgno=?", -1,
+          &pCsr->pStmt, 0
+      );
+    }
+  }
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_bind_text(pCsr->pStmt, 1, zSchema, -1, SQLITE_TRANSIENT);
+  }
+
+  /* Try to determine the encoding of the db by inspecting the header
+  ** field on page 1. */
+  if( rc==SQLITE_OK ){
+    rc = dbdataGetEncoding(pCsr);
+  }
+
+  if( rc!=SQLITE_OK ){
+    pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
+  }
+
+  if( rc==SQLITE_OK ){
+    rc = dbdataNext(pCursor);
+  }
+  return rc;
+}
+
+/*
+** Return a column for the sqlite_dbdata or sqlite_dbptr table.
+*/
+static int dbdataColumn(
+  sqlite3_vtab_cursor *pCursor, 
+  sqlite3_context *ctx, 
+  int i
+){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  DbdataTable *pTab = (DbdataTable*)pCursor->pVtab;
+  if( pTab->bPtr ){
+    switch( i ){
+      case DBPTR_COLUMN_PGNO:
+        sqlite3_result_int64(ctx, pCsr->iPgno);
+        break;
+      case DBPTR_COLUMN_CHILD: {
+        int iOff = pCsr->iPgno==1 ? 100 : 0;
+        if( pCsr->iCell<0 ){
+          iOff += 8;
+        }else{
+          iOff += 12 + pCsr->iCell*2;
+          if( iOff>pCsr->nPage ) return SQLITE_OK;
+          iOff = get_uint16(&pCsr->aPage[iOff]);
+        }
+        if( iOff<=pCsr->nPage ){
+          sqlite3_result_int64(ctx, get_uint32(&pCsr->aPage[iOff]));
+        }
+        break;
+      }
+    }
+  }else{
+    switch( i ){
+      case DBDATA_COLUMN_PGNO:
+        sqlite3_result_int64(ctx, pCsr->iPgno);
+        break;
+      case DBDATA_COLUMN_CELL:
+        sqlite3_result_int(ctx, pCsr->iCell);
+        break;
+      case DBDATA_COLUMN_FIELD:
+        sqlite3_result_int(ctx, pCsr->iField);
+        break;
+      case DBDATA_COLUMN_VALUE: {
+        if( pCsr->iField<0 ){
+          sqlite3_result_int64(ctx, pCsr->iIntkey);
+        }else if( &pCsr->pRec[pCsr->nRec] >= pCsr->pPtr ){
+          sqlite3_int64 iType;
+          dbdataGetVarintU32(pCsr->pHdrPtr, &iType);
+          dbdataValue(
+              ctx, pCsr->enc, iType, pCsr->pPtr, 
+              &pCsr->pRec[pCsr->nRec] - pCsr->pPtr
+          );
+        }
+        break;
+      }
+    }
+  }
+  return SQLITE_OK;
+}
+
+/* 
+** Return the rowid for an sqlite_dbdata or sqlite_dptr table.
+*/
+static int dbdataRowid(sqlite3_vtab_cursor *pCursor, sqlite_int64 *pRowid){
+  DbdataCursor *pCsr = (DbdataCursor*)pCursor;
+  *pRowid = pCsr->iRowid;
+  return SQLITE_OK;
+}
+
+
+/*
+** Invoke this routine to register the "sqlite_dbdata" virtual table module
+*/
+static int sqlite3DbdataRegister(sqlite3 *db){
+  static sqlite3_module dbdata_module = {
+    0,                            /* iVersion */
+    0,                            /* xCreate */
+    dbdataConnect,                /* xConnect */
+    dbdataBestIndex,              /* xBestIndex */
+    dbdataDisconnect,             /* xDisconnect */
+    0,                            /* xDestroy */
+    dbdataOpen,                   /* xOpen - open a cursor */
+    dbdataClose,                  /* xClose - close a cursor */
+    dbdataFilter,                 /* xFilter - configure scan constraints */
+    dbdataNext,                   /* xNext - advance a cursor */
+    dbdataEof,                    /* xEof - check for end of scan */
+    dbdataColumn,                 /* xColumn - read data */
+    dbdataRowid,                  /* xRowid - read data */
+    0,                            /* xUpdate */
+    0,                            /* xBegin */
+    0,                            /* xSync */
+    0,                            /* xCommit */
+    0,                            /* xRollback */
+    0,                            /* xFindMethod */
+    0,                            /* xRename */
+    0,                            /* xSavepoint */
+    0,                            /* xRelease */
+    0,                            /* xRollbackTo */
+    0                             /* xShadowName */
+  };
+
+  int rc = sqlite3_create_module(db, "sqlite_dbdata", &dbdata_module, 0);
+  if( rc==SQLITE_OK ){
+    rc = sqlite3_create_module(db, "sqlite_dbptr", &dbdata_module, (void*)1);
+  }
+  return rc;
+}
+
+int sqlite3_dbdata_init(
+  sqlite3 *db, 
+  char **pzErrMsg, 
+  const sqlite3_api_routines *pApi
+){
+  (void)pzErrMsg;
+  return sqlite3DbdataRegister(db);
+}
+
+#endif /* ifndef SQLITE_OMIT_VIRTUALTABLE */
+#pragma GCC diagnostic pop