454 lines
14 KiB
C
454 lines
14 KiB
C
/*
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** 2017-10-20
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** This file implements a VFS shim that allows an SQLite database to be
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** appended onto the end of some other file, such as an executable.
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**
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** A special record must appear at the end of the file that identifies the
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** file as an appended database and provides an offset to page 1. For
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** best performance page 1 should be located at a disk page boundary, though
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** that is not required.
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**
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** An appended database is considered immutable. It is read-only and no
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** locks are ever taken.
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**
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** If the file being opened is not an appended database, then this shim is
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** a pass-through into the default underlying VFS.
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**/
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#include <sqlite3ext.h>
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SQLITE_EXTENSION_INIT1
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#include <string.h>
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#include <assert.h>
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/* The append mark at the end of the database is:
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**
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** Start-Of-SQLite3-NNNNNNNN
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** 123456789 123456789 12345
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**
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** The NNNNNNNN represents a 64-bit big-endian unsigned integer which is
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** the offset to page 1.
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*/
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#define APND_MARK_PREFIX "Start-Of-SQLite3-"
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#define APND_MARK_PREFIX_SZ 17
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#define APND_MARK_SIZE 25
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/*
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** Forward declaration of objects used by this utility
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*/
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typedef struct sqlite3_vfs ApndVfs;
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typedef struct ApndFile ApndFile;
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/* Access to a lower-level VFS that (might) implement dynamic loading,
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** access to randomness, etc.
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*/
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#define ORIGVFS(p) ((sqlite3_vfs*)((p)->pAppData))
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#define ORIGFILE(p) ((sqlite3_file*)(((ApndFile*)(p))+1))
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/* An open file */
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struct ApndFile {
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sqlite3_file base; /* IO methods */
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sqlite3_int64 iPgOne; /* File offset to page 1 */
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};
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/*
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** Methods for ApndFile
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*/
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static int apndClose(sqlite3_file*);
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static int apndRead(sqlite3_file*, void*, int iAmt, sqlite3_int64 iOfst);
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static int apndWrite(sqlite3_file*,const void*,int iAmt, sqlite3_int64 iOfst);
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static int apndTruncate(sqlite3_file*, sqlite3_int64 size);
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static int apndSync(sqlite3_file*, int flags);
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static int apndFileSize(sqlite3_file*, sqlite3_int64 *pSize);
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static int apndLock(sqlite3_file*, int);
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static int apndUnlock(sqlite3_file*, int);
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static int apndCheckReservedLock(sqlite3_file*, int *pResOut);
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static int apndFileControl(sqlite3_file*, int op, void *pArg);
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static int apndSectorSize(sqlite3_file*);
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static int apndDeviceCharacteristics(sqlite3_file*);
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static int apndShmMap(sqlite3_file*, int iPg, int pgsz, int, void volatile**);
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static int apndShmLock(sqlite3_file*, int offset, int n, int flags);
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static void apndShmBarrier(sqlite3_file*);
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static int apndShmUnmap(sqlite3_file*, int deleteFlag);
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static int apndFetch(sqlite3_file*, sqlite3_int64 iOfst, int iAmt, void **pp);
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static int apndUnfetch(sqlite3_file*, sqlite3_int64 iOfst, void *p);
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/*
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** Methods for ApndVfs
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*/
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static int apndOpen(sqlite3_vfs*, const char *, sqlite3_file*, int , int *);
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static int apndDelete(sqlite3_vfs*, const char *zName, int syncDir);
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static int apndAccess(sqlite3_vfs*, const char *zName, int flags, int *);
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static int apndFullPathname(sqlite3_vfs*, const char *zName, int, char *zOut);
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static void *apndDlOpen(sqlite3_vfs*, const char *zFilename);
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static void apndDlError(sqlite3_vfs*, int nByte, char *zErrMsg);
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static void (*apndDlSym(sqlite3_vfs *pVfs, void *p, const char*zSym))(void);
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static void apndDlClose(sqlite3_vfs*, void*);
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static int apndRandomness(sqlite3_vfs*, int nByte, char *zOut);
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static int apndSleep(sqlite3_vfs*, int microseconds);
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static int apndCurrentTime(sqlite3_vfs*, double*);
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static int apndGetLastError(sqlite3_vfs*, int, char *);
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static int apndCurrentTimeInt64(sqlite3_vfs*, sqlite3_int64*);
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static int apndSetSystemCall(sqlite3_vfs*, const char*,sqlite3_syscall_ptr);
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static sqlite3_syscall_ptr apndGetSystemCall(sqlite3_vfs*, const char *z);
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static const char *apndNextSystemCall(sqlite3_vfs*, const char *zName);
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static sqlite3_vfs apnd_vfs = {
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3, /* iVersion (set when registered) */
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0, /* szOsFile (set when registered) */
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1024, /* mxPathname */
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0, /* pNext */
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"apndvfs", /* zName */
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0, /* pAppData (set when registered) */
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apndOpen, /* xOpen */
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apndDelete, /* xDelete */
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apndAccess, /* xAccess */
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apndFullPathname, /* xFullPathname */
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apndDlOpen, /* xDlOpen */
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apndDlError, /* xDlError */
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apndDlSym, /* xDlSym */
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apndDlClose, /* xDlClose */
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apndRandomness, /* xRandomness */
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apndSleep, /* xSleep */
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apndCurrentTime, /* xCurrentTime */
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apndGetLastError, /* xGetLastError */
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apndCurrentTimeInt64, /* xCurrentTimeInt64 */
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apndSetSystemCall, /* xSetSystemCall */
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apndGetSystemCall, /* xGetSystemCall */
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apndNextSystemCall /* xNextSystemCall */
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};
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static const sqlite3_io_methods apnd_io_methods = {
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3, /* iVersion */
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apndClose, /* xClose */
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apndRead, /* xRead */
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apndWrite, /* xWrite */
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apndTruncate, /* xTruncate */
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apndSync, /* xSync */
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apndFileSize, /* xFileSize */
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apndLock, /* xLock */
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apndUnlock, /* xUnlock */
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apndCheckReservedLock, /* xCheckReservedLock */
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apndFileControl, /* xFileControl */
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apndSectorSize, /* xSectorSize */
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apndDeviceCharacteristics, /* xDeviceCharacteristics */
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apndShmMap, /* xShmMap */
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apndShmLock, /* xShmLock */
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apndShmBarrier, /* xShmBarrier */
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apndShmUnmap, /* xShmUnmap */
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apndFetch, /* xFetch */
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apndUnfetch /* xUnfetch */
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};
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/*
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** Close an apnd-file.
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*/
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static int apndClose(sqlite3_file *pFile){
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pFile = ORIGFILE(pFile);
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return pFile->pMethods->xClose(pFile);
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}
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/*
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** Read data from an apnd-file.
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*/
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static int apndRead(
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sqlite3_file *pFile,
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void *zBuf,
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int iAmt,
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sqlite_int64 iOfst
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){
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ApndFile *p = (ApndFile *)pFile;
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pFile = ORIGFILE(pFile);
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return pFile->pMethods->xRead(pFile, zBuf, iAmt, iOfst+p->iPgOne);
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}
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/*
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** Write data to an apnd-file.
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*/
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static int apndWrite(
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sqlite3_file *pFile,
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const void *z,
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int iAmt,
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sqlite_int64 iOfst
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){
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return SQLITE_READONLY;
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}
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/*
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** Truncate an apnd-file.
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*/
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static int apndTruncate(sqlite3_file *pFile, sqlite_int64 size){
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return SQLITE_READONLY;
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}
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/*
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** Sync an apnd-file.
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*/
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static int apndSync(sqlite3_file *pFile, int flags){
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return SQLITE_READONLY;
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}
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/*
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** Return the current file-size of an apnd-file.
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*/
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static int apndFileSize(sqlite3_file *pFile, sqlite_int64 *pSize){
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ApndFile *p = (ApndFile*)pFile;
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int rc;
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pFile = ORIGFILE(p);
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rc = pFile->pMethods->xFileSize(pFile, pSize);
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if( rc==SQLITE_OK && p->iPgOne ){
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*pSize -= p->iPgOne + APND_MARK_SIZE;
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}
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return rc;
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}
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/*
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** Lock an apnd-file.
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*/
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static int apndLock(sqlite3_file *pFile, int eLock){
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return SQLITE_READONLY;
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}
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/*
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** Unlock an apnd-file.
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*/
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static int apndUnlock(sqlite3_file *pFile, int eLock){
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return SQLITE_OK;
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}
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/*
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** Check if another file-handle holds a RESERVED lock on an apnd-file.
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*/
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static int apndCheckReservedLock(sqlite3_file *pFile, int *pResOut){
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*pResOut = 0;
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return SQLITE_OK;
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}
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/*
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** File control method. For custom operations on an apnd-file.
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*/
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static int apndFileControl(sqlite3_file *pFile, int op, void *pArg){
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ApndFile *p = (ApndFile *)pFile;
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int rc;
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pFile = ORIGFILE(pFile);
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rc = pFile->pMethods->xFileControl(pFile, op, pArg);
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if( rc==SQLITE_OK && op==SQLITE_FCNTL_VFSNAME ){
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*(char**)pArg = sqlite3_mprintf("apnd(%lld)/%z", p->iPgOne, *(char**)pArg);
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}
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return rc;
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}
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/*
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** Return the sector-size in bytes for an apnd-file.
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*/
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static int apndSectorSize(sqlite3_file *pFile){
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pFile = ORIGFILE(pFile);
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return pFile->pMethods->xSectorSize(pFile);
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}
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/*
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** Return the device characteristic flags supported by an apnd-file.
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*/
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static int apndDeviceCharacteristics(sqlite3_file *pFile){
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pFile = ORIGFILE(pFile);
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return SQLITE_IOCAP_IMMUTABLE |
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pFile->pMethods->xDeviceCharacteristics(pFile);
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}
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/* Create a shared memory file mapping */
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static int apndShmMap(
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sqlite3_file *pFile,
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int iPg,
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int pgsz,
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int bExtend,
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void volatile **pp
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){
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return SQLITE_READONLY;
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}
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/* Perform locking on a shared-memory segment */
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static int apndShmLock(sqlite3_file *pFile, int offset, int n, int flags){
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return SQLITE_READONLY;
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}
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/* Memory barrier operation on shared memory */
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static void apndShmBarrier(sqlite3_file *pFile){
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return;
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}
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/* Unmap a shared memory segment */
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static int apndShmUnmap(sqlite3_file *pFile, int deleteFlag){
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return SQLITE_OK;
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}
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/* Fetch a page of a memory-mapped file */
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static int apndFetch(
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sqlite3_file *pFile,
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sqlite3_int64 iOfst,
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int iAmt,
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void **pp
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){
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ApndFile *p = (ApndFile *)pFile;
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pFile = ORIGFILE(pFile);
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return pFile->pMethods->xFetch(pFile, iOfst+p->iPgOne, iAmt, pp);
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}
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/* Release a memory-mapped page */
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static int apndUnfetch(sqlite3_file *pFile, sqlite3_int64 iOfst, void *pPage){
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ApndFile *p = (ApndFile *)pFile;
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pFile = ORIGFILE(pFile);
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return pFile->pMethods->xUnfetch(pFile, iOfst+p->iPgOne, pPage);
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}
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/*
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** Open an apnd file handle.
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*/
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static int apndOpen(
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sqlite3_vfs *pVfs,
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const char *zName,
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sqlite3_file *pFile,
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int flags,
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int *pOutFlags
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){
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ApndFile *p;
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int rc;
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sqlite3_int64 sz;
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pVfs = ORIGVFS(pVfs);
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if( (flags & SQLITE_OPEN_MAIN_DB)==0 ){
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return pVfs->xOpen(pVfs, zName, pFile, flags, pOutFlags);
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}
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p = (ApndFile*)pFile;
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memset(p, 0, sizeof(*p));
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p->base.pMethods = &apnd_io_methods;
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pFile = ORIGFILE(pFile);
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flags &= ~(SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE);
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flags |= SQLITE_OPEN_READONLY;
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rc = pVfs->xOpen(pVfs, zName, pFile, flags, pOutFlags);
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if( rc ) return rc;
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rc = pFile->pMethods->xFileSize(pFile, &sz);
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if( rc==SQLITE_OK && sz>512 ){
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unsigned char a[APND_MARK_SIZE];
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rc = pFile->pMethods->xRead(pFile, a, APND_MARK_SIZE, sz-APND_MARK_SIZE);
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if( rc==SQLITE_OK
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&& memcmp(a, APND_MARK_PREFIX, APND_MARK_PREFIX_SZ)==0
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){
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p->iPgOne =
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ]<<56) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+1]<<48) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+2]<<40) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+3]<<32) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+4]<<24) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+5]<<16) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+6]<<8) +
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((sqlite3_uint64)a[APND_MARK_PREFIX_SZ+7]);
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}
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}
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return SQLITE_OK;
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}
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/*
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** All other VFS methods are pass-thrus.
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*/
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static int apndDelete(sqlite3_vfs *pVfs, const char *zPath, int dirSync){
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return ORIGVFS(pVfs)->xDelete(ORIGVFS(pVfs), zPath, dirSync);
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}
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static int apndAccess(
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sqlite3_vfs *pVfs,
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const char *zPath,
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int flags,
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int *pResOut
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){
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return ORIGVFS(pVfs)->xAccess(ORIGVFS(pVfs), zPath, flags, pResOut);
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}
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static int apndFullPathname(
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sqlite3_vfs *pVfs,
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const char *zPath,
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int nOut,
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char *zOut
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){
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return ORIGVFS(pVfs)->xFullPathname(ORIGVFS(pVfs),zPath,nOut,zOut);
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}
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static void *apndDlOpen(sqlite3_vfs *pVfs, const char *zPath){
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return ORIGVFS(pVfs)->xDlOpen(ORIGVFS(pVfs), zPath);
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}
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static void apndDlError(sqlite3_vfs *pVfs, int nByte, char *zErrMsg){
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ORIGVFS(pVfs)->xDlError(ORIGVFS(pVfs), nByte, zErrMsg);
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}
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static void (*apndDlSym(sqlite3_vfs *pVfs, void *p, const char *zSym))(void){
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return ORIGVFS(pVfs)->xDlSym(ORIGVFS(pVfs), p, zSym);
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}
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static void apndDlClose(sqlite3_vfs *pVfs, void *pHandle){
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ORIGVFS(pVfs)->xDlClose(ORIGVFS(pVfs), pHandle);
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}
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static int apndRandomness(sqlite3_vfs *pVfs, int nByte, char *zBufOut){
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return ORIGVFS(pVfs)->xRandomness(ORIGVFS(pVfs), nByte, zBufOut);
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}
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static int apndSleep(sqlite3_vfs *pVfs, int nMicro){
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return ORIGVFS(pVfs)->xSleep(ORIGVFS(pVfs), nMicro);
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}
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static int apndCurrentTime(sqlite3_vfs *pVfs, double *pTimeOut){
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return ORIGVFS(pVfs)->xCurrentTime(ORIGVFS(pVfs), pTimeOut);
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}
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static int apndGetLastError(sqlite3_vfs *pVfs, int a, char *b){
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return ORIGVFS(pVfs)->xGetLastError(ORIGVFS(pVfs), a, b);
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}
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static int apndCurrentTimeInt64(sqlite3_vfs *pVfs, sqlite3_int64 *p){
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return ORIGVFS(pVfs)->xCurrentTimeInt64(ORIGVFS(pVfs), p);
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}
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static int apndSetSystemCall(
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sqlite3_vfs *pVfs,
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const char *zName,
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sqlite3_syscall_ptr pCall
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){
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return ORIGVFS(pVfs)->xSetSystemCall(ORIGVFS(pVfs),zName,pCall);
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}
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static sqlite3_syscall_ptr apndGetSystemCall(
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sqlite3_vfs *pVfs,
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const char *zName
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){
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return ORIGVFS(pVfs)->xGetSystemCall(ORIGVFS(pVfs),zName);
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}
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static const char *apndNextSystemCall(sqlite3_vfs *pVfs, const char *zName){
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return ORIGVFS(pVfs)->xNextSystemCall(ORIGVFS(pVfs), zName);
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}
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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/*
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** This routine is called when the extension is loaded.
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** Register the new VFS.
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*/
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int sqlite3_appendvfs_init(
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sqlite3 *db,
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char **pzErrMsg,
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const sqlite3_api_routines *pApi
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){
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int rc = SQLITE_OK;
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sqlite3_vfs *pOrig;
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SQLITE_EXTENSION_INIT2(pApi);
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pOrig = sqlite3_vfs_find(0);
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apnd_vfs.iVersion = pOrig->iVersion;
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apnd_vfs.pAppData = pOrig;
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apnd_vfs.szOsFile = sizeof(ApndFile);
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rc = sqlite3_vfs_register(&apnd_vfs, 1);
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#ifdef APPENDVFS_TEST
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if( rc==SQLITE_OK ){
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rc = sqlite3_auto_extension((void(*)(void))apndvfsRegister);
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}
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#endif
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if( rc==SQLITE_OK ) rc = SQLITE_OK_LOAD_PERMANENTLY;
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return rc;
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}
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