SQLite

  const char *zDefaultVfs,        /* VFS to use if no "vfs=xxx" query option */
  const char *zUri,               /* Nul-terminated URI to parse */
  int *pFlags,                    /* IN/OUT: SQLITE_OPEN_XXX flags */
  sqlite3_vfs **ppVfs,            /* OUT: VFS to use */ 
  char **pzFile,                  /* OUT: Filename component of URI */
  char **pzErrMsg                 /* OUT: Error message (if rc!=SQLITE_OK) */
){











  int rc = SQLITE_OK;
  int flags = *pFlags;
  const char *zVfs = zDefaultVfs;
  char *zFile;
  int nUri = sqlite3Strlen30(zUri);

  assert( *pzErrMsg==0 );

       && sqlite3Isxdigit(zUri[iIn]) 
       && sqlite3Isxdigit(zUri[iIn+1]) 
      ){
        int codepoint = (sqlite3HexToInt(zUri[iIn++]) << 4);
        codepoint += sqlite3HexToInt(zUri[iIn++]);

        assert( codepoint>=0 && codepoint<256 );
        if( codepoint>=128 ){
          *pzErrMsg = sqlite3_mprintf("invalid uri escape: %.3s", &zUri[-3]);
          rc = SQLITE_ERROR;
          goto parse_uri_out;
        }
        else if( codepoint==0 ){
          /* This branch is taken when "%00" appears within the URI. In this
          ** case we ignore all text in the remainder of the path, name or
          ** value currently being parsed. So ignore the current character
          ** and skip to the next "?", "=" or "&", as appropriate. */
          while( zUri[iIn] && zUri[iIn]!='#' 
              && (eState!=0 || zUri[iIn]!='?')
              && (eState!=1 || (zUri[iIn]!='=' && zUri[iIn]!='&'))

    if( eState==1 ) zFile[iOut++] = '\0';
    zFile[iOut++] = '\0';
    zFile[iOut++] = '\0';

    /* Check if there were any options specified that should be interpreted 
    ** here. Options that are interpreted here include "vfs" and those that
    ** correspond to flags that may be passed to the sqlite3_open_v2()
    ** method. */
    zOpt = &zFile[sqlite3Strlen30(zFile)+1];
    while( zOpt[0] ){
      int nOpt = sqlite3Strlen30(zOpt);
      char *zVal = &zOpt[nOpt+1];
      int nVal = sqlite3Strlen30(zVal);


      if( nOpt==3 && sqlite3_strnicmp("vfs", zOpt, 3)==0 ){
        zVfs = zVal;
      }else{
        struct OpenMode {
          const char *z;

          int mode;
        } *aMode = 0;
        char *zModeType;
        int mask;
        int limit;

        if( nOpt==5 && sqlite3_strnicmp("cache", zOpt, 5)==0 ){
          static struct OpenMode aCacheMode[] = {
            { "shared",  SQLITE_OPEN_SHAREDCACHE },
            { "private", SQLITE_OPEN_PRIVATECACHE },
            { 0, 0 }
          };

          mask = SQLITE_OPEN_SHAREDCACHE|SQLITE_OPEN_PRIVATECACHE;
          aMode = aCacheMode;
          limit = mask;
          zModeType = "cache";
        }
        if( nOpt==4 && sqlite3_strnicmp("mode", zOpt, 4)==0 ){
          static struct OpenMode aOpenMode[] = {
            { "ro",  SQLITE_OPEN_READONLY },
            { "rw",  SQLITE_OPEN_READWRITE }, 
            { "rwc", SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE },
            { 0, 0 }
          };

          mask = SQLITE_OPEN_READONLY|SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE;
          aMode = aOpenMode;
          limit = mask & flags;
          zModeType = "access";
        }

        if( aMode ){
          int i;
          int mode = 0;
          for(i=0; aMode[i].z; i++){
            const char *z = aMode[i].z;
            if( nVal==strlen(z) && 0==sqlite3_strnicmp(zVal, z, nVal) ){
              mode = aMode[i].mode;
              break;
            }
          }
          if( mode==0 ){
            *pzErrMsg = sqlite3_mprintf("no such %s mode: %s", zModeType, zVal);
            rc = SQLITE_ERROR;
            goto parse_uri_out;
          }
          if( mode>limit ){
            rc = SQLITE_PERM;
            goto parse_uri_out;
          }
          flags = (flags & ~mask) | mode;
        }
      }

      zOpt = &zVal[nVal+1];
    }

  }else{
    zFile = sqlite3_malloc(nUri+2);
    if( !zFile ) return SQLITE_NOMEM;
    memcpy(zFile, zUri, nUri);
    zFile[nUri] = '\0';
    zFile[nUri+1] = '\0';
  }

  *ppVfs = sqlite3_vfs_find(zVfs);
  if( *ppVfs==0 ){
    *pzErrMsg = sqlite3_mprintf("no such vfs: %s", zVfs);
    rc = SQLITE_ERROR;
  }
 parse_uri_out:
  if( rc!=SQLITE_OK ){
    sqlite3_free(zFile);

    zFile = 0;
  }
  *pFlags = flags;
  *pzFile = zFile;
  return rc;
}


/*
** This routine does the work of opening a database on behalf of
** sqlite3_open() and sqlite3_open16(). The database filename "zFilename"  
** is UTF-8 encoded.

  char *zErrMsg = 0;              /* Error message from sqlite3ParseUri() */

  *ppDb = 0;
#ifndef SQLITE_OMIT_AUTOINIT
  rc = sqlite3_initialize();
  if( rc ) return rc;
#endif

  /* Only allow sensible combinations of bits in the flags argument.  
  ** Throw an error if any non-sense combination is used.  If we
  ** do not block illegal combinations here, it could trigger
  ** assert() statements in deeper layers.  Sensible combinations
  ** are:
  **
  **  1:  SQLITE_OPEN_READONLY
  **  2:  SQLITE_OPEN_READWRITE
  **  6:  SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE
  */
  assert( SQLITE_OPEN_READONLY  == 0x01 );
  assert( SQLITE_OPEN_READWRITE == 0x02 );
  assert( SQLITE_OPEN_CREATE    == 0x04 );
  testcase( (1<<(flags&7))==0x02 ); /* READONLY */
  testcase( (1<<(flags&7))==0x04 ); /* READWRITE */
  testcase( (1<<(flags&7))==0x40 ); /* READWRITE | CREATE */
  if( ((1<<(flags&7)) & 0x46)==0 ){
    rc = SQLITE_MISUSE;
    goto opendb_out;
  }

  if( sqlite3GlobalConfig.bCoreMutex==0 ){
    isThreadsafe = 0;
  }else if( flags & SQLITE_OPEN_NOMUTEX ){
    isThreadsafe = 0;
  }else if( flags & SQLITE_OPEN_FULLMUTEX ){
    isThreadsafe = 1;

  /* Also add a UTF-8 case-insensitive collation sequence. */
  createCollation(db, "NOCASE", SQLITE_UTF8, SQLITE_COLL_NOCASE, 0,
                  nocaseCollatingFunc, 0);

  /* Parse the filename/URI argument. */
  rc = sqlite3ParseUri(zVfs, zFilename, &flags, &db->pVfs, &zOpen, &zErrMsg);
  if( rc!=SQLITE_OK ){
    sqlite3Error(db, rc, zErrMsg ? "%s" : 0, zErrMsg);
    sqlite3_free(zErrMsg);
    goto opendb_out;
  }






















  /* Open the backend database driver */
  db->openFlags = flags;
  rc = sqlite3BtreeOpen(db->pVfs, zOpen, db, &db->aDb[0].pBt, 0,
                        flags | SQLITE_OPEN_MAIN_DB);
  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;

} {1 {no such vfs: nosuchvfs}}

#-------------------------------------------------------------------------
# Test some of the other options (other than "vfs").
#
# TODO: Fix this after the list of options is decided.
#
foreach {tn mode create_ok write_ok readonly_ok} {
  1    ro    0   0   1
  2    rw    0   1   0
  3    rwc   1   1   0
} {
  catch { db close }
  forcedelete test.db

  set A(1) {0 {}}
  set A(0) {1 {unable to open database file}}
  do_test 4.1.$tn.1 {
    list [catch {sqlite3 db "file:test.db?mode=$mode"} msg] $msg
  } $A($create_ok)

  catch { db close }
  forcedelete test.db
  sqlite3 db test.db
  db eval { CREATE TABLE t1(a, b) }
  db close

  set A(1) {0 {}}
  set A(0) {1 {attempt to write a readonly database}}
  do_test 4.1.$tn.2 {
    sqlite3 db "file:test.db?mode=$mode"
    catchsql { INSERT INTO t1 VALUES(1, 2) }
  } $A($write_ok)

  set A(1) {0 {}}
  set A(0) {1 {access permission denied}}
  do_test 4.1.$tn.3 {
    list [catch {sqlite3 db "file:test.db?mode=$mode" -readonly 1} msg] $msg
  } $A($readonly_ok)
}

set orig [sqlite3_enable_shared_cache]
foreach {tn options sc_default is_shared} {
  1    ""                1   1
  2    "cache=private"   1   0
  3    "cache=shared"    1   1
  4    ""                0   0
  5    "cache=private"   0   0
  6    "cache=shared"    0   1
} {
  catch { db close }
  forcedelete test.db

  sqlite3_enable_shared_cache 1
  sqlite3 db2 test.db
  db2 eval {CREATE TABLE t1(a, b)}

  sqlite3_enable_shared_cache $sc_default
  sqlite3 db "file:test.db?$options"
  db eval {SELECT * FROM t1}

  set A(1) {1 {database table is locked: t1}}
  set A(0) {0 {}}
  do_test 4.2.$tn {

    db2 eval {BEGIN; INSERT INTO t1 VALUES(1, 2);}
    catchsql { SELECT * FROM t1 }
  } $A($is_shared)

  db2 close
}

do_test 4.3.1 {
  list [catch {sqlite3 db "file:test.db?mode=rc"} msg] $msg
} {1 {no such access mode: rc}}
do_test 4.3.2 {
  list [catch {sqlite3 db "file:test.db?cache=public"} msg] $msg
} {1 {no such cache mode: public}}

#-------------------------------------------------------------------------
# Test that things work if an ATTACHed database uses a different VFS than
# the main database. The important point is that for all operations 
# involving the ATTACHed database, the correct versions of the following
# VFS are used for all operations involving the attached database.
#

  execsql {
    ATTACH 'file:test.db2?vfs=tvfs2' AS aux;
    PRAGMA main.journal_mode = PERSIST;
    PRAGMA aux.journal_mode = PERSIST;
    CREATE TABLE t1(a, b);
    CREATE TABLE aux.t2(a, b);
    PRAGMA main.journal_mode = WAL;
    PRAGMA aux.journal_mode = WAL;
    INSERT INTO t1 VALUES('x', 'y');
    INSERT INTO t2 VALUES('x', 'y');
  }
  lsort [array names ::T1]
} {test.db1 test.db1-journal test.db1-wal}

do_test 5.1.2 {