namespace Community.CsharpSqlite
{
  public partial class Sqlite3
  {
    /*
    ** 2007 August 22
    **
    ** The author disclaims copyright to this source code.  In place of
    ** a legal notice, here is a blessing:
    **
    **    May you do good and not evil.
    **    May you find forgiveness for yourself and forgive others.
    **    May you share freely, never taking more than you give.
    **
    *************************************************************************
    **
    ** This file implements a special kind of sqlite3_file object used
    ** by SQLite to create journal files if the atomic-write optimization
    ** is enabled.
    **
    ** The distinctive characteristic of this sqlite3_file is that the
    ** actual on disk file is created lazily. When the file is created,
    ** the caller specifies a buffer size for an in-memory buffer to
    ** be used to service read() and write() requests. The actual file
    ** on disk is not created or populated until either:
    **
    **   1) The in-memory representation grows too large for the allocated
    **      buffer, or
    **   2) The sqlite3JournalCreate() function is called.
    *************************************************************************
    **  Included in SQLite3 port to C#-SQLite;  2008 Noah B Hart
    **  C#-SQLite is an independent reimplementation of the SQLite software library
    **
    **  SQLITE_SOURCE_ID: 2010-08-23 18:52:01 42537b60566f288167f1b5864a5435986838e3a3
    **
    *************************************************************************
    */
#if SQLITE_ENABLE_ATOMIC_WRITE
    //#include "sqliteInt.h"

/*
** A JournalFile object is a subclass of sqlite3_file used by
** as an open file handle for journal files.
*/
struct JournalFile {
sqlite3_io_methods pMethod;    /* I/O methods on journal files */
int nBuf;                       /* Size of zBuf[] in bytes */
string zBuf;                     /* Space to buffer journal writes */
int iSize;                      /* Amount of zBuf[] currently used */
int flags;                      /* xOpen flags */
sqlite3_vfs pVfs;              /* The "real" underlying VFS */
sqlite3_file pReal;            /* The "real" underlying file descriptor */
string zJournal;           /* Name of the journal file */
};
typedef struct JournalFile JournalFile;

/*
** If it does not already exists, create and populate the on-disk file
** for JournalFile p.
*/
static int createFile(JournalFile p){
int rc = SQLITE_OK;
if( null==p.pReal ){
sqlite3_file pReal = (sqlite3_file )&p[1];
rc = sqlite3OsOpen(p.pVfs, p.zJournal, pReal, p.flags, 0);
if( rc==SQLITE_OK ){
p.pReal = pReal;
if( p.iSize>0 ){
Debug.Assert(p.iSize<=p.nBuf);
rc = sqlite3OsWrite(p.pReal, p.zBuf, p.iSize, 0);
}
}
}
return rc;
}

/*
** Close the file.
*/
static int jrnlClose(sqlite3_file pJfd){
JournalFile p = (JournalFile )pJfd;
if( p.pReal ){
sqlite3OsClose(p.pReal);
}
sqlite3DbFree(db,p.zBuf);
return SQLITE_OK;
}

/*
** Read data from the file.
*/
static int jrnlRead(
sqlite3_file *pJfd,    /* The journal file from which to read */
void *zBuf,            /* Put the results here */
int iAmt,              /* Number of bytes to read */
sqlite_int64 iOfst     /* Begin reading at this offset */
){
int rc = SQLITE_OK;
JournalFile *p = (JournalFile )pJfd;
if( p->pReal ){
rc = sqlite3OsRead(p->pReal, zBuf, iAmt, iOfst);
}else if( (iAmt+iOfst)>p->iSize ){
rc = SQLITE_IOERR_SHORT_READ;
}else{
memcpy(zBuf, &p->zBuf[iOfst], iAmt);
}
return rc;
}

/*
** Write data to the file.
*/
static int jrnlWrite(
sqlite3_file pJfd,    /* The journal file into which to write */
string zBuf,      /* Take data to be written from here */
int iAmt,              /* Number of bytes to write */
sqlite_int64 iOfst     /* Begin writing at this offset into the file */
){
int rc = SQLITE_OK;
JournalFile p = (JournalFile )pJfd;
if( null==p.pReal && (iOfst+iAmt)>p.nBuf ){
rc = createFile(p);
}
if( rc==SQLITE_OK ){
if( p.pReal ){
rc = sqlite3OsWrite(p.pReal, zBuf, iAmt, iOfst);
}else{
memcpy(p.zBuf[iOfst], zBuf, iAmt);
if( p.iSize<(iOfst+iAmt) ){
p.iSize = (iOfst+iAmt);
}
}
}
return rc;
}

/*
** Truncate the file.
*/
static int jrnlTruncate(sqlite3_file pJfd, sqlite_int64 size){
int rc = SQLITE_OK;
JournalFile p = (JournalFile )pJfd;
if( p.pReal ){
rc = sqlite3OsTruncate(p.pReal, size);
}else if( size<p.iSize ){
p.iSize = size;
}
return rc;
}

/*
** Sync the file.
*/
static int jrnlSync(sqlite3_file pJfd, int flags){
int rc;
JournalFile p = (JournalFile )pJfd;
if( p.pReal ){
rc = sqlite3OsSync(p.pReal, flags);
}else{
rc = SQLITE_OK;
}
return rc;
}

/*
** Query the size of the file in bytes.
*/
static int jrnlFileSize(sqlite3_file pJfd, sqlite_int64 pSize){
int rc = SQLITE_OK;
JournalFile p = (JournalFile )pJfd;
if( p.pReal ){
rc = sqlite3OsFileSize(p.pReal, pSize);
}else{
pSize = (sqlite_int64) p.iSize;
}
return rc;
}

/*
** Table of methods for JournalFile sqlite3_file object.
*/
static struct sqlite3_io_methods JournalFileMethods = {
1,             /* iVersion */
jrnlClose,     /* xClose */
jrnlRead,      /* xRead */
jrnlWrite,     /* xWrite */
jrnlTruncate,  /* xTruncate */
jrnlSync,      /* xSync */
jrnlFileSize,  /* xFileSize */
0,             /* xLock */
0,             /* xUnlock */
0,             /* xCheckReservedLock */
0,             /* xFileControl */
0,             /* xSectorSize */
0,             /* xDeviceCharacteristics */
0,             /* xShmMap */
0,             /* xShmLock */
0,             /* xShmBarrier */
0              /* xShmUnmap */
};

/*
** Open a journal file.
*/
int sqlite3JournalOpen(
sqlite3_vfs pVfs,         /* The VFS to use for actual file I/O */
string zName,         /* Name of the journal file */
sqlite3_file pJfd,        /* Preallocated, blank file handle */
int flags,                 /* Opening flags */
int nBuf                   /* Bytes buffered before opening the file */
){
JournalFile p = (JournalFile )pJfd;
memset(p, 0, sqlite3JournalSize(pVfs));
if( nBuf>0 ){
p.zBuf = sqlite3MallocZero(nBuf);
if( null==p.zBuf ){
return SQLITE_NOMEM;
}
}else{
return sqlite3OsOpen(pVfs, zName, pJfd, flags, 0);
}
p.pMethod = JournalFileMethods;
p.nBuf = nBuf;
p.flags = flags;
p.zJournal = zName;
p.pVfs = pVfs;
return SQLITE_OK;
}

/*
** If the argument p points to a JournalFile structure, and the underlying
** file has not yet been created, create it now.
*/
int sqlite3JournalCreate(sqlite3_file p){
if( p.pMethods!=&JournalFileMethods ){
return SQLITE_OK;
}
return createFile((JournalFile )p);
}

/*
** Return the number of bytes required to store a JournalFile that uses vfs
** pVfs to create the underlying on-disk files.
*/
int sqlite3JournalSize(sqlite3_vfs pVfs){
return (pVfs->szOsFile+sizeof(JournalFile));
}
#endif
  }
}
