How to use the apsw.VFS function in apsw

if "." in funcname:
                    klass, funcname=funcname.split(".",1)
                else:
                    klass="apsw"
                if klass not in classes:
                    classes[klass]=[]
                classes[klass].append(funcname)


# ok, so we know what was documented.  Now lets see what exists

con=apsw.Connection(":memory:")
cur=con.cursor()
cur.execute("create table x(y); insert into x values(x'abcdef1012');select * from x")
blob=con.blobopen("main", "x", "y", con.last_insert_rowid(), 0)
vfs=apsw.VFS("aname", "")
vfsfile=apsw.VFSFile("", ":memory:", [apsw.SQLITE_OPEN_MAIN_DB|apsw.SQLITE_OPEN_CREATE|apsw.SQLITE_OPEN_READWRITE, 0])

# virtual tables aren't real - just check their size hasn't changed
assert len(classes['VTModule'])==2
del classes['VTModule']
assert len(classes['VTTable'])==13
del classes['VTTable']
assert len(classes['VTCursor'])==6
del classes['VTCursor']

for name, obj in ( ('Connection', con),
                   ('Cursor', cur),
                   ('blob', blob),
                   ('VFS', vfs),
                   ('VFSFile', vfsfile),
                   ('apsw', apsw),

### @@ example-vfs
### A VFS that "obfuscates" the database file contents.  The scheme
### used is to xor all bytes with 0xa5.  This scheme honours that used
### for MAPI and SQL Server.
###

def encryptme(data):
    if not data: return data
    if py3:
        return bytes([x^0xa5 for x in data])

    return "".join([chr(ord(x)^0xa5) for x in data])

# Inheriting from a base of "" means the default vfs
class ObfuscatedVFS(apsw.VFS):
    def __init__(self, vfsname="obfu", basevfs=""):
        self.vfsname=vfsname
        self.basevfs=basevfs
        apsw.VFS.__init__(self, self.vfsname, self.basevfs)

    # We want to return our own file implmentation, but also
    # want it to inherit
    def xOpen(self, name, flags):
        # We can look at uri parameters
        if isinstance(name, apsw.URIFilename):
            #@@CAPTURE
            print ("fast is", name.uri_parameter("fast"))
            print ("level is", name.uri_int("level", 3))
            print ("warp is", name.uri_boolean("warp", False))
            print ("notpresent is", name.uri_parameter("notpresent"))
            #@@ENDCAPTURE

import apsw
import sys
import boto3

VFS_S3_CLIENT = boto3.client('s3')


class S3VFS(apsw.VFS):
    def __init__(self, vfsname="s3", basevfs=""):
        self.vfsname=vfsname
        self.basevfs=basevfs
        apsw.VFS.__init__(self, self.vfsname, self.basevfs)

    def xOpen(self, name, flags):
        return S3VFSFile(self.basevfs, name, flags)

class S3VFSFile():
    def __init__(self, inheritfromvfsname, filename, flags):
        self.bucket = filename.uri_parameter("bucket")
        self.key = filename.filename().lstrip("/")
        print("Initiated S3 VFS for file: {}".format(self._get_s3_url()))

    def xRead(self, amount, offset):
        response = VFS_S3_CLIENT.get_object(Bucket=self.bucket, Key=self.key, Range='bytes={}-{}'.format(offset, offset + amount))