ext/zonefile/zonefile.c

/*
** 2018-02-10
**
** 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.
**
******************************************************************************
*/

#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#ifndef SQLITE_OMIT_VIRTUALTABLE

#ifndef SQLITE_AMALGAMATION
typedef sqlite3_int64 i64;
typedef sqlite3_uint64 u64;
typedef unsigned char u8;
typedef unsigned short u16;
typedef unsigned long u32;
#define MIN(a,b) ((a)<(b) ? (a) : (b))

#if defined(SQLITE_COVERAGE_TEST) || defined(SQLITE_MUTATION_TEST)
# define ALWAYS(X)      (1)
# define NEVER(X)       (0)
#elif !defined(NDEBUG)
# define ALWAYS(X)      ((X)?1:(assert(0),0))
# define NEVER(X)       ((X)?(assert(0),1):0)
#else
# define ALWAYS(X)      (X)
# define NEVER(X)       (X)
#endif
#endif   /* SQLITE_AMALGAMATION */

#define ZONEFILE_MAGIC_NUMBER 0x464B3138

#define ZONEFILE_SZ_HEADER           32
#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          \
  "CREATE TABLE z1("             \
  "  k INTEGER PRIMARY KEY,"     \
  "  v BLOB,"                    \
  "  fileid INTEGER,"            \
  "  frame INTEGER,"             \
  "  ofst INTEGER,"              \
  "  sz INTEGER"                 \
  ")"

#define ZONEFILE_FILES_SCHEMA    \
  "CREATE TABLE z2("             \
  "  filename TEXT,"             \
  "  ekey BLOB,"                 \
  "  header JSON HIDDEN"         \
  ")"


#include <stdio.h>
#include <string.h>
#include <assert.h>

/*
** A structure to store the parameters for a single zonefile_write()
** invocation. 
*/
typedef struct ZonefileWrite ZonefileWrite;
struct ZonefileWrite {
  int compressionTypeIndexData;
  int compressionTypeContent;
  int encryptionType;
  int maxAutoFrameSize;
};

/*
** A structure to store a deserialized zonefile header in.
*/
typedef struct ZonefileHeader ZonefileHeader;
struct ZonefileHeader {
  u32 magicNumber;
  u8 compressionTypeIndexData;
  u8 compressionTypeContent;
  u32 byteOffsetDictionary;
  u32 byteOffsetFrames;
  u32 numFrames;
  u32 numKeys;
  u8 encryptionType;
  u8 encryptionKeyIdx;
  u8 extendedHeaderVersion;
  u8 extendedHeaderSize;
};

/*
** Buffer structure used by the zonefile_write() implementation.
*/
typedef struct ZonefileBuffer ZonefileBuffer;
struct ZonefileBuffer {
  u8 *a;
  int n;
  int nAlloc;
};

/*
** Set the error message contained in context ctx to the results of
** vprintf(zFmt, ...).
*/
static void zonefileCtxError(sqlite3_context *ctx, const char *zFmt, ...){
  char *zMsg = 0;
  va_list ap;
  va_start(ap, zFmt);
  zMsg = sqlite3_vmprintf(zFmt, ap);
  sqlite3_result_error(ctx, zMsg, -1);
  sqlite3_free(zMsg);
  va_end(ap);
}

static void zonefileTransferError(sqlite3_context *pCtx){
  sqlite3 *db = sqlite3_context_db_handle(pCtx);
  const char *zErr = sqlite3_errmsg(db);
  sqlite3_result_error(pCtx, zErr, -1);
}

static int zonefilePrepare(
  sqlite3 *db,
  sqlite3_stmt **ppStmt,
  char **pzErr,
  const char *zFmt,
  ...
){
  int rc;
  va_list ap;
  char *zSql;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  *ppStmt = 0;
  if( zSql ){
    rc = sqlite3_prepare(db, zSql, -1, ppStmt, 0);
    if( rc!=SQLITE_OK ){
      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
    }
    sqlite3_free(zSql);
  }else{
    rc = SQLITE_NOMEM;
  }
  return rc;
}


static sqlite3_stmt *zonefileCtxPrepare(
  sqlite3_context *pCtx,
  const char *zFmt,
  ...
){
  sqlite3_stmt *pRet = 0;
  va_list ap;
  char *zSql;
  va_start(ap, zFmt);
  zSql = sqlite3_vmprintf(zFmt, ap);
  if( zSql ){
    sqlite3 *db = sqlite3_context_db_handle(pCtx);
    int rc = sqlite3_prepare(db, zSql, -1, &pRet, 0);
    if( rc!=SQLITE_OK ){
      zonefileTransferError(pCtx);
    }
    sqlite3_free(zSql);
  }else{
    sqlite3_result_error_nomem(pCtx);
  }
  return pRet;
}

/*
** Return zero if the two SQL values passed as arguments are equal, or
** non-zero otherwise. Values with different types are considered unequal,
** even if they both contain the same numeric value (e.g. 2 and 2.0).
*/
static int zonefileCompareValue(sqlite3_value *p1, sqlite3_value *p2){
  int eType;
  assert( p1 );
  if( p2==0 ) return 1;
  eType = sqlite3_value_type(p1);
  if( sqlite3_value_type(p2)!=eType ) return 1;
  switch( eType ){
    case SQLITE_INTEGER:
      return sqlite3_value_int64(p1)!=sqlite3_value_int64(p2);
    case SQLITE_FLOAT:
      return sqlite3_value_double(p1)!=sqlite3_value_double(p2);
    case SQLITE_TEXT:
    case SQLITE_BLOB: {
      int n1 = sqlite3_value_bytes(p1);
      int n2 = sqlite3_value_bytes(p2);
      if( n1!=n2 ) return 1;
      return memcmp(sqlite3_value_blob(p1), sqlite3_value_blob(p2), n1);
    }
    default:
      assert( eType==SQLITE_NULL);
  }

  return 0;
}

int zonefileIsAutoFrame(sqlite3_value *pFrame){
  return (
      sqlite3_value_type(pFrame)==SQLITE_INTEGER 
   && sqlite3_value_int64(pFrame)==-1
  );
}

static int zonefileGetParams(
  sqlite3_context *pCtx,          /* Leave any error message here */
  const char *zJson,              /* JSON configuration parameter (or NULL) */
  ZonefileWrite *p                /* Populate this object before returning */
){
  sqlite3 *db = sqlite3_context_db_handle(pCtx);
  sqlite3_stmt *pStmt = 0;
  char *zErr = 0;
  int rc = SQLITE_OK;
  int rc2;

  memset(p, 0, sizeof(ZonefileWrite));
  p->maxAutoFrameSize = ZONEFILE_DEFAULT_MAXAUTOFRAMESIZE;

  rc = zonefilePrepare(db, &pStmt, &zErr,"SELECT key, value FROM json_each(?)");
  if( rc==SQLITE_OK ){
    sqlite3_bind_text(pStmt, 1, zJson, -1, SQLITE_STATIC);
  }
  while( rc==SQLITE_OK && SQLITE_ROW==sqlite3_step(pStmt) ){
    const char *zKey = (const char*)sqlite3_column_text(pStmt, 0);
    int iVal = sqlite3_column_int(pStmt, 1);
    if( sqlite3_stricmp("maxAutoFrameSize", zKey)==0 ){
      p->maxAutoFrameSize = iVal;
    }else
    if( sqlite3_stricmp("compressionTypeIndexData", zKey)==0 ){
      p->compressionTypeIndexData = iVal;
    }else
    if( sqlite3_stricmp("compressionTypeContent", zKey)==0 ){
      p->compressionTypeContent = iVal;
    }else
    if( sqlite3_stricmp("encryptionType", zKey)==0 ){
      p->encryptionType = iVal;
    }else{
      rc = SQLITE_ERROR;
      zErr = sqlite3_mprintf("unknown parameter name: \"%s\"", zKey);
    }
  }
  rc2 = sqlite3_finalize(pStmt);
  if( rc==SQLITE_OK ) rc = rc2;

  if( zErr ){
    sqlite3_result_error(pCtx, zErr, -1);
    sqlite3_free(zErr);
  }
  return rc;
}

/*
** Check that there is room in buffer pBuf for at least nByte bytes more 
** data. If not, attempt to allocate more space. If the allocation attempt
** fails, leave an error message in context pCtx and return SQLITE_ERROR.
**
** If no error occurs, SQLITE_OK is returned.
*/
static int zonefileBufferGrow(
  sqlite3_context *pCtx, 
  ZonefileBuffer *pBuf, 
  int nByte
){
  int nReq = pBuf->n + nByte;
  if( nReq>pBuf->nAlloc ){
    u8 *aNew;
    int nNew = pBuf->nAlloc ? pBuf->nAlloc*2 : 128;
    while( nNew<nReq ) nNew = nNew*2;
    aNew = sqlite3_realloc(pBuf->a, nNew);
    if( aNew==0 ){
      sqlite3_result_error_nomem(pCtx);
      return SQLITE_ERROR;
    }
    pBuf->a = aNew;
    pBuf->nAlloc = nNew;
  }
  return SQLITE_OK;
}

static void zonefileBufferFree(ZonefileBuffer *pBuf){
  sqlite3_free(pBuf->a);
  memset(pBuf, 0, sizeof(ZonefileBuffer));
}

static void zonefilePut32(u8 *aBuf, u32 v){
  aBuf[0] = (v >> 24) & 0xFF;
  aBuf[1] = (v >> 16) & 0xFF;
  aBuf[2] = (v >>  8) & 0xFF;
  aBuf[3] = v & 0xFF;
}

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 ? "wb" : "rb");
  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_value **objv            /* Array of SQL arguments */
){
  const char *zFile = 0;          /* File to write to */
  const char *zTbl = 0;           /* Database object to read from */
  const char *zJson = 0;          /* JSON configuration parameters */
  ZonefileWrite sWrite;           /* Decoded JSON parameters */
  int nKey = 0;                   /* Number of keys in new zonefile */
  int nFrame = 0;                 /* Number of frames in new zonefile */
  int szFrame = 0;                /* Size of current frame */
  sqlite3_stmt *pStmt = 0;        /* SQL used to read data from source table */
  FILE *pFd = 0;
  int rc;
  sqlite3_value *pPrev = 0;
  char *zErr = 0;

  ZonefileBuffer sFrameIdx = {0, 0, 0};
  ZonefileBuffer sKeyIdx = {0, 0, 0};
  ZonefileBuffer sFrames = {0, 0, 0};
  u8 aHdr[ZONEFILE_SZ_HEADER];    /* Space to assemble zonefile header */

  assert( objc==2 || objc==3 );
  zFile = (const char*)sqlite3_value_text(objv[0]);
  zTbl = (const char*)sqlite3_value_text(objv[1]);
  if( objc==3 ){
    zJson = (const char*)sqlite3_value_text(objv[2]);
  }
  if( zonefileGetParams(pCtx, zJson, &sWrite) ) return;

  /* Prepare the SQL statement used to read data from the source table. This
  ** also serves to verify the suitability of the source table schema. */
  pStmt = zonefileCtxPrepare(pCtx, 
      "SELECT k, frame, v FROM %Q ORDER BY frame, idx, k", zTbl
  );
  if( pStmt==0 ) return;

  /* Open a file-handle used to write out the zonefile */ 
  pFd = zonefileFileOpen(zFile, 1, &zErr);
  if( pFd==0 ){
    sqlite3_result_error(pCtx, zErr, -1);
    sqlite3_finalize(pStmt);
    sqlite3_free(zErr);
    return;
  }

  while( SQLITE_ROW==sqlite3_step(pStmt) ){
    sqlite3_int64 k = sqlite3_column_int64(pStmt, 0);
    sqlite3_value *pFrame = sqlite3_column_value(pStmt, 1);
    int nBlob = sqlite3_column_bytes(pStmt, 2);
    const u8 *pBlob = (const u8*)sqlite3_column_blob(pStmt, 2);

    int bAuto = zonefileIsAutoFrame(pFrame);
    if( zonefileCompareValue(pFrame, pPrev) 
     || (bAuto && szFrame && (szFrame+nBlob)>sWrite.maxAutoFrameSize)
    ){
      /* Add new entry to sFrameIdx */
      szFrame = 0;
      if( zonefileBufferGrow(pCtx, &sFrameIdx, 4) ) goto zone_write_out;
      zonefileAppend32(&sFrameIdx, sFrames.n);
      sqlite3_value_free(pPrev);
      pPrev = sqlite3_value_dup(pFrame);
      if( pPrev==0 ){
        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;
    zonefileAppendBlob(&sFrames, pBlob, nBlob);
    szFrame += nBlob;
    nKey++;
  }
  sqlite3_value_free(pPrev);
  pPrev = 0;

  /* Create the zonefile header in the in-memory buffer */
  memset(aHdr, 0, ZONEFILE_SZ_HEADER);
  zonefilePut32(&aHdr[0], ZONEFILE_MAGIC_NUMBER);
  aHdr[4] = sWrite.compressionTypeIndexData;
  aHdr[5] = sWrite.compressionTypeContent;
  zonefilePut32(&aHdr[6], 0);     /* Compression dictionary byte offset */
  zonefilePut32(&aHdr[10], ZONEFILE_SZ_HEADER + sFrameIdx.n + sKeyIdx.n); 
  zonefilePut32(&aHdr[14], nFrame);
  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);
  }
  pFd = 0;

 zone_write_out:
  if( pFd ) fclose(pFd);
  sqlite3_finalize(pStmt);
  zonefileBufferFree(&sFrameIdx);
  zonefileBufferFree(&sKeyIdx);
  zonefileBufferFree(&sFrames);
}

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;
};

/*
** This function does the work of xCreate (if bCreate!=0) or xConnect
** (if bCreate==0) for the zonefile_files module.
*/
static int zffCreateConnect(
  int bCreate,
  sqlite3 *db,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  ZonefileFilesTab *p;
  const char *zName = argv[2];
  const char *zDb = argv[1];
  int nName = strlen(zName);
  int nDb = strlen(zDb);
  int rc = SQLITE_OK;

  if( nName<6 || memcmp(&zName[nName-6], "_files", 6)!=0 ){
    *pzErr = sqlite3_mprintf("do not create zonefile_files tables directly!");
    *ppVtab = 0;
    return SQLITE_ERROR;
  }

  p = (ZonefileFilesTab*)sqlite3_malloc(sizeof(ZonefileFilesTab)+nName+1+nDb+1);
  if( !p ){
    rc = SQLITE_NOMEM;
  }else{
    memset(p, 0, sizeof(ZonefileFilesTab));
    p->zBase = (char*)&p[1];
    memcpy(p->zBase, zName, nName-6);
    p->zBase[nName-6] = '\0';
    p->zDb = &p->zBase[nName+1];
    memcpy(p->zDb, zDb, nDb+1);
    p->db = db;
    rc = sqlite3_declare_vtab(db, ZONEFILE_FILES_SCHEMA);
  }

  if( rc!=SQLITE_OK ){
    sqlite3_free(p);
    p = 0;
  }
  *ppVtab = (sqlite3_vtab*)p;
  return rc;
}

/* 
** zonefile_files virtual table module xCreate method.
*/
static int zffCreate(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  return zffCreateConnect(1, db, argc, argv, ppVtab, pzErr);
}

/* 
** zonefile_files virtual table module xConnect method.
*/
static int zffConnect(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  return zffCreateConnect(0, db, argc, argv, ppVtab, pzErr);
}

/* 
** 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 int zffClose(sqlite3_vtab_cursor *cur){
  ZonefileFilesCsr *pCsr = (ZonefileFilesCsr*)cur;
  zffCursorReset(pCsr);
  sqlite3_free(pCsr);
  return SQLITE_OK;
}

/* 
** zonefile_files virtual table module xNext method.
*/
static int zffNext(sqlite3_vtab_cursor *cur){
  ZonefileFilesCsr *pCsr = (ZonefileFilesCsr*)cur;
  int rc;
  if( SQLITE_ROW==sqlite3_step(pCsr->pSelect) ){
    rc = SQLITE_OK;
  }else{
    rc = sqlite3_finalize(pCsr->pSelect);
    pCsr->pSelect = 0;
  }
  return rc;
}

/* 
** zonefile_files virtual table module xFilter method.
*/
static int zffFilter(
  sqlite3_vtab_cursor *cur, 
  int idxNum, const char *idxStr,
  int argc, sqlite3_value **argv
){
  ZonefileFilesCsr *pCsr = (ZonefileFilesCsr*)cur;
  ZonefileFilesTab *pTab = (ZonefileFilesTab*)(pCsr->base.pVtab);
  int rc;
  zffCursorReset(pCsr);

  rc = zonefilePrepare(pTab->db, &pCsr->pSelect, &pTab->base.zErrMsg,
      "SELECT filename, fileid FROM %Q.'%q_shadow_file'",
      pTab->zDb, pTab->zBase
  );
  if( rc==SQLITE_OK ){
    rc = zffNext(cur);
  }
  return rc;
}

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

static void zonefileHeaderDeserialize(u8 *aBuf, ZonefileHeader *pHdr){
  pHdr->magicNumber = zonefileGet32(&aBuf[0]);
  pHdr->compressionTypeIndexData = aBuf[4];
  pHdr->compressionTypeContent = aBuf[5];
  pHdr->byteOffsetDictionary = zonefileGet32(&aBuf[6]);
  pHdr->byteOffsetFrames = zonefileGet32(&aBuf[10]);
  pHdr->numFrames = zonefileGet32(&aBuf[14]);
  pHdr->numKeys = zonefileGet32(&aBuf[18]);
  pHdr->encryptionType = aBuf[22];
  pHdr->encryptionKeyIdx = aBuf[23];
  pHdr->extendedHeaderVersion = aBuf[24];
  pHdr->extendedHeaderSize = aBuf[25];
}

static void zonefileJsonHeader(sqlite3_context *pCtx, const char *zFile){
  char *zErr = 0;
  FILE *pFd = zonefileFileOpen(zFile, 0, &zErr);
  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{
      char *zJson = sqlite3_mprintf("{"
          "\"magicNumber\":%u,"
          "\"compressionTypeIndexData\":%u,"
          "\"compressionTypeContent\":%u,"
          "\"byteOffsetDictionary\":%u,"
          "\"byteOffsetFrames\":%u,"
          "\"numFrames\":%u,"
          "\"numKeys\":%u,"
          "\"encryptionType\":%u,"
          "\"encryptionKeyIdx\":%u,"
          "\"extendedHeaderVersion\":%u,"
          "\"extendedHeaderSize\":%u}",
          (u32)hdr.magicNumber,
          (u32)hdr.compressionTypeIndexData,
          (u32)hdr.compressionTypeContent,
          (u32)hdr.byteOffsetDictionary,
          (u32)hdr.byteOffsetFrames,
          (u32)hdr.numFrames,
          (u32)hdr.numKeys,
          (u32)hdr.encryptionType,
          (u32)hdr.encryptionKeyIdx,
          (u32)hdr.extendedHeaderVersion,
          (u32)hdr.extendedHeaderSize
      );
      if( zJson ){
        sqlite3_result_text(pCtx, zJson, -1, SQLITE_TRANSIENT);
        sqlite3_free(zJson);
      }else{
        sqlite3_result_error_nomem(pCtx);
      }
    }
    fclose(pFd);
  }else{
    sqlite3_result_error(pCtx, zErr, -1);
    sqlite3_free(zErr);
  }
}

/* 
** zonefile_files virtual table module xColumn method.
*/
static int zffColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
  ZonefileFilesCsr *pCsr = (ZonefileFilesCsr*)cur;
  switch( i ){
    case 0: /* filename */
      sqlite3_result_value(ctx, sqlite3_column_value(pCsr->pSelect, 0));
      break;
    case 1: /* ekey */
      break;
    case 2: { /* header */
      const char *zFile = (const char*)sqlite3_column_text(pCsr->pSelect, 0);
      zonefileJsonHeader(ctx, zFile);
      break;
    }
  }
  return SQLITE_OK;
}

/* 
** 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:
**
**   1. The "old" rowid, or NULL.
**   2. The "new" rowid.
**   3. Values for each of the 3 columns: (filename,ekey,header)
*/
static int zffUpdate(
  sqlite3_vtab *pVtab, 
  int nVal, 
  sqlite3_value **apVal, 
  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
**   argv[2]   -> table name
*/
static int zonefileCreateConnect(
  int bCreate,
  sqlite3 *db,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  ZonefileTab *p;
  const char *zName = argv[2];
  const char *zDb = argv[1];
  int nName = strlen(zName);
  int nDb = strlen(zDb);
  int rc = SQLITE_OK;

  p = (ZonefileTab*)sqlite3_malloc(sizeof(ZonefileTab) + nName+1 + nDb+1);
  if( !p ){
    rc = SQLITE_NOMEM;
  }else{
    memset(p, 0, sizeof(ZonefileTab));
    p->zName = (char*)&p[1];
    memcpy(p->zName, zName, nName+1);
    p->zDb = &p->zName[nName+1];
    memcpy(p->zDb, zDb, nDb+1);
    p->db = db;
  
    if( bCreate ){
      char *zSql = sqlite3_mprintf(
          "CREATE TABLE %Q.'%q_shadow_idx'(" 
          "  k INTEGER PRIMARY KEY,"
          "  fileid INTEGER,"
          "  frame INTEGER,"
          "  ofst INTEGER,"
          "  sz INTEGER"
          ");"
          "CREATE TABLE %Q.'%q_shadow_file'(" 
          "  filename TEXT,"
          "  fileid INTEGER PRIMARY KEY"
          ");" 
          "CREATE VIRTUAL TABLE %Q.'%q_files' USING zonefile_files;",
          zDb, zName, zDb, zName, zDb, zName
      );
  
      if( zSql==0 ){
        rc = SQLITE_NOMEM;
      }else{
        rc = sqlite3_exec(db, zSql, 0, 0, pzErr);
        sqlite3_free(zSql);
      }
    }
    
    if( rc==SQLITE_OK ){
      rc = sqlite3_declare_vtab(db, ZONEFILE_SCHEMA);
    }
  }

  if( rc!=SQLITE_OK ){
    sqlite3_free(p);
    p = 0;
  }
  *ppVtab = (sqlite3_vtab*)p;
  return rc;
}

/* 
** zonefile virtual table module xCreate method.
*/
static int zonefileCreate(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  return zonefileCreateConnect(1, db, argc, argv, ppVtab, pzErr);
}

/* 
** zonefile virtual table module xConnect method.
*/
static int zonefileConnect(
  sqlite3 *db,
  void *pAux,
  int argc, const char *const*argv,
  sqlite3_vtab **ppVtab,
  char **pzErr
){
  return zonefileCreateConnect(0, db, argc, argv, ppVtab, pzErr);
}

/* 
** 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 */
    zffCreate,                    /* xCreate - create a table */
    zffConnect,                   /* xConnect - connect to an existing table */
    zffBestIndex,                 /* xBestIndex - Determine search strategy */
    zffDisconnect,                /* xDisconnect - Disconnect from a table */
    zffDisconnect,                /* xDestroy - Drop a table */
    zffOpen,                      /* xOpen - open a cursor */
    zffClose,                     /* xClose - close a cursor */
    zffFilter,                    /* xFilter - configure scan constraints */
    zffNext,                      /* xNext - advance a cursor */
    zffEof,                       /* xEof */
    zffColumn,                    /* xColumn - read data */
    zffRowid,                     /* xRowid - read data */
    zffUpdate,                    /* xUpdate - write data */
    0,                            /* xBegin - begin transaction */
    0,                            /* xSync - sync transaction */
    0,                            /* xCommit - commit transaction */
    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 */
    zonefileOpen,                 /* xOpen - open a cursor */
    zonefileClose,                /* xClose - close a cursor */
    zonefileFilter,               /* xFilter - configure scan constraints */
    zonefileNext,                 /* xNext - advance a cursor */
    zonefileEof,                  /* xEof */
    zonefileColumn,               /* xColumn - read data */
    zonefileRowid,                /* xRowid - read data */
    0,                            /* xUpdate - write data */
    0,                            /* xBegin - begin transaction */
    0,                            /* xSync - sync transaction */
    0,                            /* xCommit - commit transaction */
    0,                            /* xRollback - rollback transaction */
    0,                            /* xFindFunction - function overloading */
    0,                            /* xRename - rename the table */
    0,                            /* xSavepoint */
    0,                            /* xRelease */
    0                             /* xRollbackTo */
  };

  struct Func {
    const char *z;
    int n;
    void (*x)(sqlite3_context*,int,sqlite3_value**);
  } aFunc[] = {
    { "zonefile_write", 2, zonefileWriteFunc },
    { "zonefile_write", 3, zonefileWriteFunc },
  };

  int rc = SQLITE_OK;
  int i;

  for(i=0; rc==SQLITE_OK && i<sizeof(aFunc)/sizeof(aFunc[0]); i++){
    struct Func *p = &aFunc[i];
    rc = sqlite3_create_function(db, p->z, p->n, SQLITE_ANY, 0, p->x, 0, 0);
  }

  if( rc==SQLITE_OK ){
    rc = sqlite3_create_module(db, "zonefile_files", &filesModule, 0);
  }
  if( rc==SQLITE_OK ){
    rc = sqlite3_create_module(db, "zonefile", &zonefileModule, 0);
  }

  return rc;
}

#else         /* SQLITE_OMIT_VIRTUALTABLE */
# define zonefileRegister(x) SQLITE_OK
#endif

#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_zonefile_init(
  sqlite3 *db, 
  char **pzErrMsg, 
  const sqlite3_api_routines *pApi
){
  SQLITE_EXTENSION_INIT2(pApi);
  (void)pzErrMsg;  /* Unused parameter */
  return zonefileRegister(db);
}