SQLite

# define ALWAYS(X)      (X)
# define NEVER(X)       (X)
#endif
#endif   /* SQLITE_AMALGAMATION */

#define ZONEFILE_MAGIC_NUMBER 0x464B3138

#define ZONEFILE_SZ_HEADER           26
#define ZONEFILE_SZ_KEYOFFSETS_ENTRY 20

#define ZONEFILE_DEFAULT_MAXAUTOFRAMESIZE (64*1024)
#define ZONEFILE_DEFAULT_ENCRYPTION       0
#define ZONEFILE_DEFAULT_COMPRESSION      0


#define ZONEFILE_SCHEMA          \

static u32 zonefileGet32(u8 *aBuf){
  return (((u32)aBuf[0]) << 24)
       + (((u32)aBuf[1]) << 16)
       + (((u32)aBuf[2]) <<  8)
       + (((u32)aBuf[3]) <<  0);
}

static u64 zonefileGet64(u8 *aBuf){
  return (((u64)aBuf[0]) << 56)
       + (((u64)aBuf[1]) << 48)
       + (((u64)aBuf[2]) << 40)
       + (((u64)aBuf[3]) << 32) 
       + (((u64)aBuf[4]) << 24)
       + (((u64)aBuf[5]) << 16)
       + (((u64)aBuf[6]) <<  8)
       + (((u64)aBuf[7]) <<  0);
}

static void zonefileAppend32(ZonefileBuffer *pBuf, u32 v){
  zonefilePut32(&pBuf->a[pBuf->n], v);
  pBuf->n += 4;
}

static void zonefileAppend64(ZonefileBuffer *pBuf, u64 v){
  zonefileAppend32(pBuf, v>>32);
  zonefileAppend32(pBuf, v & 0xFFFFFFFF);
}

static void zonefileAppendBlob(ZonefileBuffer *pBuf, const u8 *p, int n){
  memcpy(&pBuf->a[pBuf->n], p, n);
  pBuf->n += n;
}

static int zonefileFileWrite(FILE *pFd, const u8 *aBuf, int nBuf){
  size_t res = fwrite(aBuf, 1, nBuf, pFd);
  return res!=nBuf ? SQLITE_ERROR : SQLITE_OK;
}

static int zonefileFileRead(FILE *pFd, u8 *aBuf, int nBuf, i64 iOff){
  int rc = fseek(pFd, iOff, SEEK_SET);
  if( rc==0 ){
    rc = fread(aBuf, 1, nBuf, pFd);
    rc = (rc==nBuf) ? SQLITE_OK : SQLITE_ERROR;
  }
  return rc;
}

static FILE *zonefileFileOpen(const char *zFile, int bWrite, char **pzErr){
  FILE *pFd = fopen(zFile, bWrite ? "w" : "r");
  if( pFd==0 ){
    *pzErr = sqlite3_mprintf("failed to open file \"%s\" for %s",
        zFile, bWrite ? "writing" : "reading"
    );
  }
  return pFd;
}

static void zonefileFileClose(FILE *pFd){
  if( pFd ) fclose(pFd);
}

/*
** Function:     zonefile_write(F,T[,J])
*/
static void zonefileWriteFunc(
  sqlite3_context *pCtx,       /* Context object */
  int objc,                       /* Number of SQL arguments */

        sqlite3_result_error_nomem(pCtx);
        goto zone_write_out;
      }
      nFrame++;
    }

    /* Add new entry to sKeyIdx */
    if( zonefileBufferGrow(pCtx, &sKeyIdx, ZONEFILE_SZ_KEYOFFSETS_ENTRY) ){
      goto zone_write_out;
    }
    zonefileAppend64(&sKeyIdx, k);
    zonefileAppend32(&sKeyIdx, nFrame-1);
    zonefileAppend32(&sKeyIdx, szFrame);
    zonefileAppend32(&sKeyIdx, nBlob);

    /* Add data for new entry to sFrames */
    if( zonefileBufferGrow(pCtx, &sFrames, nBlob) ) goto zone_write_out;

  zonefilePut32(&aHdr[18], nKey);
  aHdr[22] = sWrite.encryptionType;
  aHdr[23] = 0;                   /* Encryption key index */
  aHdr[24] = 0;                   /* extended header version */
  aHdr[25] = 0;                   /* extended header size */
  assert( ZONEFILE_SZ_HEADER==26 );

  rc = zonefileFileWrite(pFd, aHdr, ZONEFILE_SZ_HEADER);
  if( rc==SQLITE_OK ) rc = zonefileFileWrite(pFd, sFrameIdx.a, sFrameIdx.n);
  if( rc==SQLITE_OK ) rc = zonefileFileWrite(pFd, sKeyIdx.a, sKeyIdx.n);
  if( rc==SQLITE_OK ) rc = zonefileFileWrite(pFd, sFrames.a, sFrames.n);
  if( rc ){
    zonefileCtxError(pCtx, "error writing file \"%s\" (fwrite())", zFile);
    goto zone_write_out;
  }

  if( fclose(pFd) ){
    zonefileCtxError(pCtx, "error writing file \"%s\" (fclose())", zFile);

typedef struct ZonefileFilesTab ZonefileFilesTab;
struct ZonefileFilesTab {
  sqlite3_vtab base;              /* Base class - must be first */
  sqlite3 *db;
  char *zBase;                    /* Name of this table */
  char *zDb;                      /* Database containing this table */
  sqlite3_stmt *pInsert;          /* Insert into the %_shadow_file table */
  sqlite3_stmt *pInsertIdx;       /* Insert into the %_shadow_idx table */
  sqlite3_stmt *pDeleteIdx;       /* Delete by fileid from %_shadow_idx table */
  sqlite3_stmt *pDelete;          /* Delete by rowid from %_shadow_file table */
};

typedef struct ZonefileFilesCsr ZonefileFilesCsr;
struct ZonefileFilesCsr {
  sqlite3_vtab_cursor base;       /* Base class - must be first */
  sqlite3_stmt *pSelect;

/* 
** zonefile_files virtual table module xDisconnect method.
*/
static int zffDisconnect(sqlite3_vtab *pVtab){
  ZonefileFilesTab *pTab = (ZonefileFilesTab*)pVtab;
  sqlite3_finalize(pTab->pInsert);
  sqlite3_finalize(pTab->pDelete);
  sqlite3_finalize(pTab->pInsertIdx);
  sqlite3_finalize(pTab->pDeleteIdx);
  sqlite3_free(pTab);
  return SQLITE_OK;
}

/* 
** zonefile_files virtual table module xBestIndex method.
*/
static int zffBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pInfo){
  return SQLITE_OK;
}

/* 
** zonefile_files virtual table module xOpen method.
*/
static int zffOpen(sqlite3_vtab *pVtab, sqlite3_vtab_cursor **ppCursor){
  ZonefileFilesCsr *pCsr;
  pCsr = (ZonefileFilesCsr*)sqlite3_malloc(sizeof(ZonefileFilesCsr));
  if( pCsr==0 ){
    return SQLITE_NOMEM;
  }
  memset(pCsr, 0, sizeof(ZonefileFilesCsr));
  *ppCursor = (sqlite3_vtab_cursor*)pCsr;
  return SQLITE_OK;
}

/* 
** Reset a ZonefileFilesCsr object to the state it is in immediately after
** it is allocated by zffOpen().
*/
static void zffCursorReset(ZonefileFilesCsr *pCsr){
  sqlite3_finalize(pCsr->pSelect);
  pCsr->pSelect = 0;
}

/* 
** zonefile_files virtual table module xClose method.

static void zonefileJsonHeader(sqlite3_context *pCtx, const char *zFile){
  FILE *pFd = zonefileOpenFile(pCtx, zFile);
  if( pFd ){
    int rc;
    ZonefileHeader hdr;
    u8 aBuf[ZONEFILE_SZ_HEADER];

    rc = zonefileFileRead(pFd, aBuf, ZONEFILE_SZ_HEADER, 0);
    if( rc==SQLITE_OK ){
      zonefileHeaderDeserialize(aBuf, &hdr);
    }

    if( rc!=SQLITE_OK ){
      zonefileCtxError(pCtx, "failed to read header from file: \"%s\"", zFile);
    }else{

** zonefile_files virtual table module xRowid method.
*/
static int zffRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  ZonefileFilesCsr *pCsr = (ZonefileFilesCsr*)cur;
  *pRowid = sqlite3_column_int64(pCsr->pSelect, 1);
  return SQLITE_OK;
}

/*
** Read and decode a Zonefile header from the start of the file opened
** by file-handle pFd. If successful, populate object (*pHdr) before
** returning SQLITE_OK. Otherwise, if an error occurs, set output
** parameter (*pzErr) to point to an English language error message and
** return an SQLite error code.
**
** It is the responsibility of the caller to eventually free any error
** message returned via (*pzErr) using sqlite3_free().
*/
static int zonefileReadHeader(
  FILE *pFd,                      /* File to read from */
  const char *zFile,              /* Name of file opened by pFd */
  ZonefileHeader *pHdr,           /* Populate this object before returning */
  char **pzErr                    /* OUT: Error message */
){
  u8 aBuf[ZONEFILE_SZ_HEADER];
  int rc = zonefileFileRead(pFd, aBuf, ZONEFILE_SZ_HEADER, 0);
  if( rc==SQLITE_OK ){
    zonefileHeaderDeserialize(aBuf, pHdr);
    if( pHdr->magicNumber!=ZONEFILE_MAGIC_NUMBER ){
      rc = SQLITE_ERROR;
    }
  }

  if( rc!=SQLITE_OK ){
    *pzErr = sqlite3_mprintf(
        "failed to read zonefile header from file \"%s\"", zFile
    );
  }

  return rc;
}

static int zonefilePopulateIndex(
  ZonefileFilesTab *pTab,
  const char *zFile,
  i64 iFileid
){
  ZonefileHeader hdr;
  int rc;
  FILE *pFd = zonefileFileOpen(zFile, 0, &pTab->base.zErrMsg);

  if( pFd==0 ){
    rc = SQLITE_ERROR;
  }else{
    rc = zonefileReadHeader(pFd, zFile, &hdr, &pTab->base.zErrMsg);
  }

  if( rc==SQLITE_OK && hdr.numKeys>0 ){
    /* TODO: Deal with encrypted and compressed ZonefileIndex objects */
    i64 iOff;                     /* Offset of keyOffsets array */
    u8 *aKey;                     /* Entire KeyOffsets array */
    int nKey;                     /* Size of buffer aKey[] in bytes */
    int i;
    assert( hdr.encryptionType==0 && hdr.compressionTypeIndexData==0 );

    iOff = ZONEFILE_SZ_HEADER + (hdr.numFrames * 4);
    nKey = ZONEFILE_SZ_KEYOFFSETS_ENTRY * hdr.numKeys;
    aKey = (u8*)sqlite3_malloc(nKey);
    if( aKey==0 ){
      rc = SQLITE_NOMEM;
    }else{
      rc = zonefileFileRead(pFd, aKey, nKey, iOff);
    }

    if( rc==SQLITE_OK && pTab->pInsertIdx==0 ){
      rc = zonefilePrepare(pTab->db, &pTab->pInsertIdx, &pTab->base.zErrMsg,
          "INSERT INTO %Q.'%q_shadow_idx'(k, fileid, frame, ofst, sz)"
          "VALUES(?,?,?,?,?)",
          pTab->zDb, pTab->zBase
      );
    }

    for(i=0; i<hdr.numKeys && rc==SQLITE_OK; i++){
      u8 *aEntry = &aKey[ZONEFILE_SZ_KEYOFFSETS_ENTRY * i];

      sqlite3_bind_int64(pTab->pInsertIdx, 1, (i64)zonefileGet64(&aEntry[0]));
      sqlite3_bind_int64(pTab->pInsertIdx, 2, iFileid);
      sqlite3_bind_int64(pTab->pInsertIdx, 3, (i64)zonefileGet32(&aEntry[8]));
      sqlite3_bind_int64(pTab->pInsertIdx, 4, (i64)zonefileGet32(&aEntry[12]));
      sqlite3_bind_int64(pTab->pInsertIdx, 5, (i64)zonefileGet32(&aEntry[16]));

      sqlite3_step(pTab->pInsertIdx);
      rc = sqlite3_reset(pTab->pInsertIdx);
      if( rc!=SQLITE_OK ){
        pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
      }
    }
    sqlite3_free(aKey);
  }

  zonefileFileClose(pFd);
  return rc;
}

/*
** zonefile_files virtual table module xUpdate method.
**
** A delete specifies a single argument - the rowid of the row to remove.
** 
** Update and insert operations pass:

  sqlite_int64 *pRowid
){
  int rc = SQLITE_OK;
  ZonefileFilesTab *pTab = (ZonefileFilesTab*)pVtab;

  if( sqlite3_value_type(apVal[0])==SQLITE_INTEGER ){
    if( pTab->pDelete==0 ){
      rc = zonefilePrepare(pTab->db, &pTab->pDelete, &pVtab->zErrMsg,
          "DELETE FROM %Q.'%q_shadow_file' WHERE fileid=?",
          pTab->zDb, pTab->zBase
      );
    }
    if( rc==SQLITE_OK && pTab->pDeleteIdx==0 ){
      rc = zonefilePrepare(pTab->db, &pTab->pDeleteIdx, &pVtab->zErrMsg,
          "DELETE FROM %Q.'%q_shadow_idx' WHERE fileid=?",
          pTab->zDb, pTab->zBase
      );
    }

    if( rc==SQLITE_OK ){
      sqlite3_bind_value(pTab->pDelete, 1, apVal[0]);
      sqlite3_step(pTab->pDelete);
      rc = sqlite3_reset(pTab->pDelete);
    }
    if( rc==SQLITE_OK ){
      sqlite3_bind_value(pTab->pDeleteIdx, 1, apVal[0]);
      sqlite3_step(pTab->pDeleteIdx);
      rc = sqlite3_reset(pTab->pDeleteIdx);
    }
  }
  if( nVal>1 ){
    const char *zFile = (const char*)sqlite3_value_text(apVal[2]);

    if( pTab->pInsert==0 ){
      rc = zonefilePrepare(pTab->db, &pTab->pInsert, &pVtab->zErrMsg,
          "INSERT INTO %Q.'%q_shadow_file'(filename) VALUES(?)",
          pTab->zDb, pTab->zBase
      );
    }

    /* Add the new entry to the %_shadow_file table. */
    if( rc==SQLITE_OK ){

      sqlite3_bind_text(pTab->pInsert, 1, zFile, -1, SQLITE_TRANSIENT);
      sqlite3_step(pTab->pInsert);
      rc = sqlite3_reset(pTab->pInsert);
    }

    /* Populate the %_shadow_idx table with entries for all keys in
    ** the zonefile just added to %_shadow_file.  */
    if( rc==SQLITE_OK ){
      i64 iFileid = sqlite3_last_insert_rowid(pTab->db);
      rc = zonefilePopulateIndex(pTab, zFile, iFileid);
    }
  }

  return rc;
}

typedef struct ZonefileTab ZonefileTab;
struct ZonefileTab {
  sqlite3_vtab base;         /* Base class - must be first */
  sqlite3 *db;
  sqlite3_stmt *pIdToName;   /* Translate fileid to filename */
  char *zName;               /* Name of this table */
  char *zDb;                 /* Name of db containing this table */
};

typedef struct ZonefileCsr ZonefileCsr;
struct ZonefileCsr {
  sqlite3_vtab_cursor base;  /* Base class - must be first */
  sqlite3_stmt *pSelect;     /* SELECT on %_shadow_idx table */
};

/*
** This function does the work of xCreate (if bCreate!=0) or xConnect
** (if bCreate==0) for the zonefile module.
**
**   argv[0]   -> module name  ("zonefile")
**   argv[1]   -> database name

}

/* 
** zonefile virtual table module xDisconnect method.
*/
static int zonefileDisconnect(sqlite3_vtab *pVtab){
  ZonefileTab *pTab = (ZonefileTab*)pVtab;
  sqlite3_finalize(pTab->pIdToName);
  sqlite3_free(pTab);
  return SQLITE_OK;
}

/* 
** Zonefile virtual table module xBestIndex method.
**
** Equality and range constraints on either the rowid or column "k" (which
** are the same thing) are processed. Bits in the idxNum parameter are
** set to indicate the constraints present:
**
**   0x01:   k == ? 
**   0x02:   k <  ? 
**   0x04:   k <= ? 
**   0x08:   k >  ? 
**   0x10:   k >= ? 
**
** Only some combinations are valid:
**
**   * If an == constraint is found, no other bits are set.
**   * If a < constraint is present, any <= is ignored.
**   * If a > constraint is present, any >= is ignored.
*/
static int zonefileBestIndex(sqlite3_vtab *pVtab, sqlite3_index_info *pInfo){
  int iEq = -1;
  int iLt = -1;
  int iLe = -1;
  int iGt = -1;
  int iGe = -1;
  int i;
  int idxNum = 0;
  double cost = 1000000000.0;

  for(i=0; i<pInfo->nConstraint; i++){
    struct sqlite3_index_constraint *p = &pInfo->aConstraint[i];
    if( p->usable && p->iColumn<=0 ){
      switch( p->op ){
        case SQLITE_INDEX_CONSTRAINT_EQ: iEq = i; break;
        case SQLITE_INDEX_CONSTRAINT_LT: iLt = i; break;
        case SQLITE_INDEX_CONSTRAINT_LE: iLe = i; break;
        case SQLITE_INDEX_CONSTRAINT_GT: iGt = i; break;
        case SQLITE_INDEX_CONSTRAINT_GE: iGe = i; break;
      }
    }
  }

  if( iEq>=0 ){
    cost = 10.0;
    idxNum = 0x01;
    pInfo->aConstraintUsage[iEq].argvIndex = 1;
  }else{
    int iIdx = 1;
    if( iLt>=0 ){
      pInfo->aConstraintUsage[iLt].argvIndex = iIdx++;
      idxNum |= 0x02;
    }else if( iLe>=0 ){
      pInfo->aConstraintUsage[iLe].argvIndex = iIdx++;
      idxNum |= 0x04;
    }
    if( iGt>=0 ){
      pInfo->aConstraintUsage[iGt].argvIndex = iIdx++;
      idxNum |= 0x08;
    }else if( iGe>=0 ){
      pInfo->aConstraintUsage[iGe].argvIndex = iIdx++;
      idxNum |= 0x10;
    }

    if( iIdx==2 ) cost = 10000.0;
    if( iIdx==3 ) cost = 100.0;
  }

  pInfo->idxNum = idxNum;
  pInfo->estimatedCost = cost;

  return SQLITE_OK;
}

/* 
** zonefile virtual table module xDestroy method.
*/
static int zonefileDestroy(sqlite3_vtab *pVtab){
  ZonefileTab *pTab = (ZonefileTab*)pVtab;
  int rc = SQLITE_OK;
  char *zSql = sqlite3_mprintf(
      "DROP TABLE IF EXISTS %Q.'%q_shadow_idx';"
      "DROP TABLE IF EXISTS %Q.'%q_shadow_file';"
      "DROP TABLE IF EXISTS %Q.'%q_files';",
      pTab->zDb, pTab->zName, pTab->zDb, pTab->zName, pTab->zDb, pTab->zName
  );
  if( zSql==0 ){
    rc = SQLITE_NOMEM;
  }else{
    rc = sqlite3_exec(pTab->db, zSql, 0, 0, 0);
    sqlite3_free(zSql);
  }

  if( rc==SQLITE_OK ){
    zonefileDisconnect(pVtab);
  }
  return rc;
}

/* 
** zonefile virtual table module xOpen method.
*/
static int zonefileOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
  ZonefileCsr *pCsr;
  pCsr = (ZonefileCsr*)sqlite3_malloc(sizeof(ZonefileCsr));
  if( pCsr==0 ){
    return SQLITE_NOMEM;
  }
  memset(pCsr, 0, sizeof(ZonefileCsr));
  *ppCursor = (sqlite3_vtab_cursor*)pCsr;
  return SQLITE_OK;
}

/* 
** Reset a ZonefileCsr object to the state it is in immediately after
** it is allocated by zffOpen().
*/
static void zonefileCursorReset(ZonefileCsr *pCsr){
  sqlite3_finalize(pCsr->pSelect);
  pCsr->pSelect = 0;
}

/* 
** zonefile virtual table module xClose method.
*/
static int zonefileClose(sqlite3_vtab_cursor *cur){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  zonefileCursorReset(pCsr);
  sqlite3_free(pCsr);
  return SQLITE_OK;
}

/* 
** zonefile virtual table module xNext method.
*/
static int zonefileNext(sqlite3_vtab_cursor *cur){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  int rc = SQLITE_OK;
  if( SQLITE_ROW!=sqlite3_step(pCsr->pSelect) ){
    rc = sqlite3_finalize(pCsr->pSelect);
    if( rc!=SQLITE_OK ){
      ZonefileTab *pTab = (ZonefileTab*)pCsr->base.pVtab;
      pTab->base.zErrMsg = sqlite3_mprintf("%s", sqlite3_errmsg(pTab->db));
    }
    pCsr->pSelect = 0;
  }
  return rc;
}

/* 
** zonefile virtual table module xFilter method.
*/
static int zonefileFilter(
  sqlite3_vtab_cursor *cur, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  ZonefileTab *pTab = (ZonefileTab*)pCsr->base.pVtab;
  int rc;

  const char *z1 = 0;
  const char *z2 = 0;

  if( idxNum & 0x01 ){
    z1 = "k = ?";
  }else{
    if( idxNum & 0x02 ) { z1 = "k < ?"; }
    if( idxNum & 0x04 ) { z1 = "k <= ?"; }
    if( idxNum & 0x08 ) { if( z1 ) z2 = "k > ?"; else z1 = "k > ?"; }
    if( idxNum & 0x10 ) { if( z1 ) z2 = "k <= ?"; else z1 = "k <= ?"; }
  }

  rc = zonefilePrepare(pTab->db, &pCsr->pSelect, &pTab->base.zErrMsg, 
      "SELECT k, fileid, frame, ofst, sz FROM %Q.'%q_shadow_idx'%s%s%s%s",
      pTab->zDb, pTab->zName,
      z1 ? " WHERE " : "", z1, 
      z2 ? " AND " : "", z2
  );

  if( z1 ) sqlite3_bind_value(pCsr->pSelect, 1, argv[0]);
  if( z2 ) sqlite3_bind_value(pCsr->pSelect, 2, argv[1]);

  if( rc==SQLITE_OK ){
    rc = zonefileNext(cur);
  }

  return rc;
}

/*
** zonefile virtual table module xEof method.
*/
static int zonefileEof(sqlite3_vtab_cursor *cur){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  return (pCsr->pSelect==0);
}

static void zonefileFree(void *p){
  sqlite3_free(p);
}

static int zonefileGetValue(sqlite3_context *pCtx, ZonefileCsr *pCsr){
  ZonefileTab *pTab = (ZonefileTab*)pCsr->base.pVtab;
  const char *zFile = 0;
  char *zErr = 0;
  FILE *pFd = 0;
  int rc = SQLITE_OK;
  u32 iOff = 0;                   /* Offset of frame in file */
  ZonefileHeader hdr;

  if( pTab->pIdToName==0 ){
    rc = zonefilePrepare(pTab->db, &pTab->pIdToName, &pTab->base.zErrMsg, 
        "SELECT filename FROM %Q.'%q_shadow_file' WHERE fileid=?",
        pTab->zDb, pTab->zName
    );
    if( rc!=SQLITE_OK ){
      zonefileTransferError(pCtx);
      return SQLITE_ERROR;
    }
  }

  /* Open the file to read the blob from */
  sqlite3_bind_int64(pTab->pIdToName, 1, sqlite3_column_int64(pCsr->pSelect,1));
  if( SQLITE_ROW==sqlite3_step(pTab->pIdToName) ){
    zFile = (const char*)sqlite3_column_text(pTab->pIdToName, 0);
    pFd = zonefileFileOpen(zFile, 0, &zErr);
  }
  if( zFile==0 ){
    rc = sqlite3_reset(pTab->pIdToName);
    if( rc!=SQLITE_OK ){
      zonefileTransferError(pCtx);
    }else{
      rc = SQLITE_CORRUPT_VTAB;
    }
  }else if( pFd==0 ){
    rc = SQLITE_ERROR;
  }

  /* Read the zonefile header */
  if( rc==SQLITE_OK ){
    rc = zonefileReadHeader(pFd, zFile, &hdr, &zErr);
  }

  /* Calculate the offset of the frame to read the blob from */
  if( rc==SQLITE_OK ){
    u8 aOff[4] = {0,0,0,0};
    int iFrame = sqlite3_column_int(pCsr->pSelect, 2);
    rc = zonefileFileRead(pFd, aOff, 4, ZONEFILE_SZ_HEADER + 4 * iFrame);
    iOff = zonefileGet32(aOff);
  }

  /* Read the blob */
  if( rc==SQLITE_OK ){
    int sz = sqlite3_column_int(pCsr->pSelect, 4);
    int ofst = sqlite3_column_int(pCsr->pSelect, 3);
    u8 *aBuf = sqlite3_malloc(sz);
    if( aBuf==0 ){
      rc = SQLITE_NOMEM;
    }else{
      rc = zonefileFileRead(pFd, aBuf, sz, hdr.byteOffsetFrames + iOff + ofst);
      if( rc==SQLITE_OK ){
        sqlite3_result_blob(pCtx, aBuf, sz, zonefileFree);
      }else{
        zErr = sqlite3_mprintf(
            "failed to read %d bytes from file \"%s\"", sz, zFile
        );
      }
    }
  }

  sqlite3_reset(pTab->pIdToName);
  if( zErr ){
    assert( rc!=SQLITE_OK );
    sqlite3_result_error(pCtx, zErr, -1);
    sqlite3_free(zErr);
  }
  zonefileFileClose(pFd);
  return rc;
}

/* 
** zonefile virtual table module xColumn method.
*/
static int zonefileColumn(
  sqlite3_vtab_cursor *cur, 
  sqlite3_context *pCtx, 
  int i
){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  int rc = SQLITE_OK;
  switch( i ){
    case 0: /* k */
      sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pSelect, 0));
      break;
    case 1: /* v */
      rc = zonefileGetValue(pCtx, pCsr);
      break;
    case 2: /* fileid */
      sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pSelect, 1));
      break;
    case 3: /* frame */
      sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pSelect, 2));
      break;
    case 4: /* ofst */
      sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pSelect, 3));
      break;
    default: /* sz */
      sqlite3_result_value(pCtx, sqlite3_column_value(pCsr->pSelect, 4));
      break;
  }
  return rc;
}

/* 
** zonefile virtual table module xRowid method.
*/
static int zonefileRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
  ZonefileCsr *pCsr = (ZonefileCsr*)cur;
  *pRowid = sqlite3_column_int64(pCsr->pSelect, 0);
  return SQLITE_OK;
}


/*
** Register the "zonefile" extensions.
*/
static int zonefileRegister(sqlite3 *db){
  static sqlite3_module filesModule = {
    0,                            /* iVersion */

    0,                            /* xRollback - rollback transaction */
    0,                            /* xFindFunction - function overloading */
    0,                            /* xRename - rename the table */
    0,                            /* xSavepoint */
    0,                            /* xRelease */
    0                             /* xRollbackTo */
  };

  static sqlite3_module zonefileModule = {
    0,                            /* iVersion */
    zonefileCreate,               /* xCreate - create a table */
    zonefileConnect,              /* xConnect - connect to an existing table */
    zonefileBestIndex,            /* xBestIndex - Determine search strategy */
    zonefileDisconnect,           /* xDisconnect - Disconnect from a table */
    zonefileDestroy,              /* xDestroy - Drop a table */

do_execsql_test 1.0 {
  CREATE TABLE zz(k INTEGER PRIMARY KEY, frame INTEGER, idx INTEGER, v BLOB);
  INSERT INTO zz VALUES(1, -1, -1, randomblob(100));
  INSERT INTO zz VALUES(2, -1, -1, randomblob(100));
  INSERT INTO zz VALUES(3, -1, -1, randomblob(100));
}


do_execsql_test 1.1 {
  SELECT zonefile_write('test.zonefile', 'zz');
} {{}}

do_execsql_test 1.2 {
  CREATE VIRTUAL TABLE z1 USING zonefile;
  SELECT name FROM sqlite_master WHERE name LIKE 'z1%' ORDER BY 1;
} {z1 z1_files z1_shadow_file z1_shadow_idx}

do_execsql_test 1.3 {
  INSERT INTO z1_files(filename) VALUES('test.zonefile');
  SELECT filename, 
         json_extract(header, '$.magicNumber'),
         json_extract(header, '$.numFrames'),
         json_extract(header, '$.numKeys')
         FROM z1_files;
} {test.zonefile 1179332920 1 3}

do_execsql_test 1.4 { SELECT count(*) FROM z1_shadow_idx } 3

do_execsql_test 1.5.1 { SELECT k FROM z1 } {1 2 3}
do_execsql_test 1.5.2 { SELECT fileid FROM z1 } {1 1 1}
do_execsql_test 1.5.3 { SELECT frame FROM z1 } {0 0 0}
do_execsql_test 1.5.4 { SELECT sz FROM z1 } {100 100 100}

do_execsql_test 1.5.5 {
  SELECT zz.v==z1.v FROM zz, z1 WHERE zz.k=z1.k
} {1 1 1}

do_execsql_test 1.5 {
  DELETE FROM z1_files;
  SELECT * FROM z1_files;
} {}

do_execsql_test 1.6 { SELECT count(*) FROM z1_shadow_idx } 0

do_execsql_test 1.7 { DROP TABLE z1 }

finish_test