SQLite

** However, before returning SQLITE_FULL, the write requests invoke
** a callback function that is configurable for each quota group.
** This callback has the opportunity to enlarge the quota.  If the
** callback does enlarge the quota such that the total size of all
** files within the group is less than the new quota, then the write
** continues as if nothing had happened.
*/
#include "test_quota.h"
#include <string.h>
#include <assert.h>

/*
** For an build without mutexes, no-op the mutex calls.
*/
#if defined(SQLITE_THREADSAFE) && SQLITE_THREADSAFE==0

** VFS is appended to this structure.
*/
struct quotaConn {
  sqlite3_file base;              /* Base class - must be first */
  quotaFile *pFile;               /* The underlying file */
  /* The underlying VFS sqlite3_file is appended to this object */
};

/*
** An instance of the following object records the state of an
** open file.  This object is opaque to all users - the internal
** structure is only visible to the functions below.
*/
struct quota_FILE {
  FILE *f;                /* Open stdio file pointer */
  sqlite3_int64 iOfst;    /* Current offset into the file */
  quotaFile *pFile;       /* The file record in the quota system */
};


/************************* Global Variables **********************************/
/*
** All global variables used by this file are containing within the following
** gQuota structure.
*/
static struct {

  quotaConn *p = (quotaConn*)pConn;
  return (sqlite3_file*)&p[1];
}

/* Find a file in a quota group and return a pointer to that file.
** Return NULL if the file is not in the group.
*/
static quotaFile *quotaFindFile(
  quotaGroup *pGroup,     /* Group in which to look for the file */
  const char *zName,      /* Full pathname of the file */
  int createFlag          /* Try to create the file if not found */
){
  quotaFile *pFile = pGroup->pFiles;
  while( pFile && strcmp(pFile->zFilename, zName)!=0 ){
    pFile = pFile->pNext;
  }
  if( pFile==0 && createFlag ){
    int nName = strlen(zName);
    pFile = (quotaFile *)sqlite3_malloc( sizeof(*pFile) + nName + 1 );
    if( pFile ){
      memset(pFile, 0, sizeof(*pFile));
      pFile->zFilename = (char*)&pFile[1];
      memcpy(pFile->zFilename, zName, nName+1);
      pFile->pNext = pGroup->pFiles;
      if( pGroup->pFiles ) pGroup->pFiles->ppPrev = &pFile->pNext;
      pFile->ppPrev = &pGroup->pFiles;
      pGroup->pFiles = pFile;
      pFile->pGroup = pGroup;
    }
  }
  return pFile;
}

/************************* VFS Method Wrappers *****************************/
/*
** This is the xOpen method used for the "quota" VFS.

  }else{
    /* If we get to this point, it means the file needs to be quota tracked.
    */
    pQuotaOpen = (quotaConn*)pConn;
    pSubOpen = quotaSubOpen(pConn);
    rc = pOrigVfs->xOpen(pOrigVfs, zName, pSubOpen, flags, pOutFlags);
    if( rc==SQLITE_OK ){
      pFile = quotaFindFile(pGroup, zName, 1);
      if( pFile==0 ){



        quotaLeave();
        pSubOpen->pMethods->xClose(pSubOpen);
        return SQLITE_NOMEM;
      }








      pFile->deleteOnClose = (flags & SQLITE_OPEN_DELETEONCLOSE)!=0;

      pFile->nRef++;
      pQuotaOpen->pFile = pFile;
      if( pSubOpen->pMethods->iVersion==1 ){
        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV1;
      }else{
        pQuotaOpen->base.pMethods = &gQuota.sIoMethodsV2;
      }

  /* If the file just deleted is a member of a quota group, then remove
  ** it from that quota group.
  */
  if( rc==SQLITE_OK ){
    quotaEnter();
    pGroup = quotaGroupFind(zName);
    if( pGroup ){
      pFile = quotaFindFile(pGroup, zName, 0);
      if( pFile ){
        if( pFile->nRef ){
          pFile->deleteOnClose = 1;
        }else{
          quotaRemoveFile(pFile);
          quotaGroupDeref(pGroup);
        }

    fd->pMethods->xClose(fd);
  }else if( rc==SQLITE_CANTOPEN ){
    quotaGroup *pGroup;
    quotaFile *pFile;
    quotaEnter();
    pGroup = quotaGroupFind(zFull);
    if( pGroup ){
      pFile = quotaFindFile(pGroup, zFull, 0);
      if( pFile ) quotaRemoveFile(pFile);
    }
    quotaLeave();
  }
  sqlite3_free(fd);
  return rc;
}

/*
** Open a potentially quotaed file for I/O.
*/
quota_FILE *sqlite3_quota_fopen(const char *zFilename, const char *zMode){
  quota_FILE *p = 0;
  char *zFull = 0;
  int rc;
  quotaGroup *pGroup;
  quotaFile *pFile;

  p = sqlite3_malloc(gQuota.sThisVfs.mxPathname + 1);
  if( p==0 ) return 0;
  zFull = (char*)&p[1];
  rc = gQuota.pOrigVfs->xFullPathname(gQuota.pOrigVfs, zFilename,
                                      gQuota.sThisVfs.mxPathname+1, zFull);
  if( rc ) goto quota_fopen_error;
  p = sqlite3_malloc(sizeof(*p));
  if( p==0 ) goto quota_fopen_error;
  memset(p, 0, sizeof(*p));
  p->f = fopen(zFull, zMode);
  if( p->f==0 ) goto quota_fopen_error;
  quotaEnter();
  pGroup = quotaGroupFind(zFull);
  if( pGroup ){
    pFile = quotaFindFile(pGroup, zFull, 1);
    if( pFile==0 ){
      quotaLeave();
      goto quota_fopen_error;
    }
    pFile->nRef++;
    p->pFile = pFile;
  }
  quotaLeave();
  sqlite3_free(zFull);
  return p;

quota_fopen_error:
  sqlite3_free(zFull);
  if( p && p->f ) fclose(p->f);
  sqlite3_free(p);
  return 0;
}

/*
** Read content from a quota_FILE
*/
size_t sqlite3_quota_fread(
  void *pBuf,            /* Store the content here */
  size_t size,           /* Size of each element */
  size_t nmemb,          /* Number of elements to read */
  quota_FILE *p          /* Read from this quota_FILE object */
){
  return fread(pBuf, size, nmemb, p->f);
}

/*
** Write content into a quota_FILE.  Invoke the quota callback and block
** the write if we exceed quota.
*/
size_t sqlite3_quota_fwrite(
  void *pBuf,            /* Take content to write from here */
  size_t size,           /* Size of each element */
  size_t nmemb,          /* Number of elements */
  quota_FILE *p          /* Write to this quota_FILE objecct */
){
  sqlite3_int64 iOfst;
  sqlite3_int64 iEnd;
  sqlite3_int64 szNew;
  quotaFile *pFile;
  
  iOfst = ftell(p->f);
  iEnd = iOfst + size*nmemb;
  pFile = p->pFile;
  if( pFile->iSize<iEnd ){
    quotaGroup *pGroup = pFile->pGroup;
    quotaEnter();
    szNew = pGroup->iSize - pFile->iSize + iEnd;
    if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
      if( pGroup->xCallback ){
        pGroup->xCallback(pFile->zFilename, &pGroup->iLimit, szNew, 
                          pGroup->pArg);
      }
      if( szNew>pGroup->iLimit && pGroup->iLimit>0 ){
        iEnd = pGroup->iLimit - pGroup->iSize + pFile->iSize;
        nmemb = (iEnd - iOfst)/size;
        iEnd = iOfst + size*nmemb;
        szNew = pGroup->iSize - pFile->iSize + iEnd;
      }
    }
    pGroup->iSize = szNew;
    pFile->iSize = iEnd;
    quotaLeave();
  }
  return fwrite(pBuf, size, nmemb, p->f);
}

/*
** Close an open quota_FILE stream.
*/
int sqlite3_quota_fclose(quota_FILE *p){
  int rc;
  quotaFile *pFile;
  rc = fclose(p->f);
  pFile = p->pFile;
  quotaEnter();
  pFile->nRef--;
  if( pFile->nRef==0 ){
    quotaGroup *pGroup = pFile->pGroup;
    if( pFile->deleteOnClose ) quotaRemoveFile(pFile);
    quotaGroupDeref(pGroup);
  }
  quotaLeave();
  sqlite3_free(p);
  return rc;
}

/*
** Seek on a quota_FILE stream.
*/
int sqlite3_quota_fseek(quota_FILE *p, long offset, int whence){
  return fseek(p->f, offset, whence);
}

/*
** rewind a quota_FILE stream.
*/
void sqlite3_quota_rewind(quota_FILE *p){
  rewind(p->f);
}

/*
** Tell the current location of a quota_FILE stream.
*/
long sqlite3_quota_ftell(quota_FILE *p){
  return ftell(p->f);
}

/*
** Remove a file.  Update quotas accordingly.
*/
int sqlite3_quota_remove(const char *zFilename){
  int rc = remove(zFilename);
  sqlite3_quota_file(zFilename);
  return rc;
}

  
/***************************** Test Code ***********************************/
#ifdef SQLITE_TEST
#include <tcl.h>

/*

/*
** 2011 December 1
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains the interface definition for the quota a VFS shim.
**
** This particular shim enforces a quota system on files.  One or more
** database files are in a "quota group" that is defined by a GLOB
** pattern.  A quota is set for the combined size of all files in the
** the group.  A quota of zero means "no limit".  If the total size
** of all files in the quota group is greater than the limit, then
** write requests that attempt to enlarge a file fail with SQLITE_FULL.
**
** However, before returning SQLITE_FULL, the write requests invoke
** a callback function that is configurable for each quota group.
** This callback has the opportunity to enlarge the quota.  If the
** callback does enlarge the quota such that the total size of all
** files within the group is less than the new quota, then the write
** continues as if nothing had happened.
*/
#ifndef _QUOTA_H_
#include "sqlite3.h"
#include <stdio.h>

/*
** Initialize the quota VFS shim.  Use the VFS named zOrigVfsName
** as the VFS that does the actual work.  Use the default if
** zOrigVfsName==NULL.  
**
** The quota VFS shim is named "quota".  It will become the default
** VFS if makeDefault is non-zero.
**
** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once
** during start-up.
*/
int sqlite3_quota_initialize(const char *zOrigVfsName, int makeDefault);

/*
** Shutdown the quota system.
**
** All SQLite database connections must be closed before calling this
** routine.
**
** THIS ROUTINE IS NOT THREADSAFE.  Call this routine exactly once while
** shutting down in order to free all remaining quota groups.
*/
int sqlite3_quota_shutdown(void);

/*
** Create or destroy a quota group.
**
** The quota group is defined by the zPattern.  When calling this routine
** with a zPattern for a quota group that already exists, this routine
** merely updates the iLimit, xCallback, and pArg values for that quota
** group.  If zPattern is new, then a new quota group is created.
**
** The zPattern is always compared against the full pathname of the file.
** Even if APIs are called with relative pathnames, SQLite converts the
** name to a full pathname before comparing it against zPattern.  zPattern
** is a standard glob pattern with the following matching rules:
**
**      '*'       Matches any sequence of zero or more characters.
**
**      '?'       Matches exactly one character.
**
**     [...]      Matches one character from the enclosed list of
**                characters.
**
**     [^...]     Matches one character not in the enclosed list.
**
** Note that, unlike unix shell globbing, the directory separator "/"
** can match a wildcard.  So, for example, the pattern "/abc/xyz/" "*"
** matches any files anywhere in the directory hierarchy beneath
** /abc/xyz
**
** If the iLimit for a quota group is set to zero, then the quota group
** is disabled and will be deleted when the last database connection using
** the quota group is closed.
**
** Calling this routine on a zPattern that does not exist and with a
** zero iLimit is a no-op.
**
** A quota group must exist with a non-zero iLimit prior to opening
** database connections if those connections are to participate in the
** quota group.  Creating a quota group does not affect database connections
** that are already open.
*/
int sqlite3_quota_set(
  const char *zPattern,           /* The filename pattern */
  sqlite3_int64 iLimit,           /* New quota to set for this quota group */
  void (*xCallback)(              /* Callback invoked when going over quota */
     const char *zFilename,         /* Name of file whose size increases */
     sqlite3_int64 *piLimit,        /* IN/OUT: The current limit */
     sqlite3_int64 iSize,           /* Total size of all files in the group */
     void *pArg                     /* Client data */
  ),
  void *pArg,                     /* client data passed thru to callback */
  void (*xDestroy)(void*)         /* Optional destructor for pArg */
);

/*
** Bring the named file under quota management.  Or if it is already under
** management, update its size.
*/
int sqlite3_quota_file(const char *zFilename);

/*
** The following object serves the same role as FILE in the standard C
** library.  It represents an open connection to a file on disk for I/O.
*/
typedef struct quota_FILE quota_FILE;

/*
** Create a new quota_FILE object used to read and/or write to the
** file zFilename.  The zMode parameter is as with standard library zMode.
*/
quota_FILE *sqlite3_quota_fopen(const char *zFilename, const char *zMode);

/*
** Perform I/O against a quota_FILE object.  When doing writes, the
** quota mechanism may result in a short write, in order to prevent
** the sum of sizes of all files from going over quota.
*/
size_t sqlite3_quota_fread(void*, size_t, size_t, quota_FILE*);
size_t sqlite3_quota_fwrite(void*, size_t, size_t, quota_FILE*);

/*
** Close a quota_FILE object and free all associated resources.  The
** file remains under quota management.
*/
int sqlite3_quota_fclose(quota_FILE*);

/*
** Move the read/write pointer for a quota_FILE object.  Or tell the
** current location of the read/write pointer.
*/
int sqlite3_quota_fseek(quota_FILE*, long, int);
void sqlite3_quota_rewind(quota_FILE*);
long sqlite3_quota_ftell(quota_FILE*);

/*
** Delete a file from the disk.  If that file is under quota management,
** then adjust quotas accordingly.
**
** The file being deleted must not be open for reading or writing or as
** a database when it is deleted.
*/
int sqlite3_quota_remove(const char *zFilename);

#endif /* _QUOTA_H_ */