How does the file.seek() work ?

[gert]

I want the file pointer set to 100 and overwrite everything from there

curl -C 100 -T upload2.wsgi http://192.168.2.17/appwsgi/wsgi/upload2.wsgi
-v

w+ overwrites my file completely
r+ overwrites nothing
a+ only makes my file bigger

import os

def application(environ, response):
query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
offset=[]
for r in range: offset.append(r.split('-'))
with open(query,'w+') as f:
f.seek(int(offset[0][0]))
while True:
chunk=environ['wsgi.input'].read(8192).decode('latin1')
if not chunk: break
f.write(chunk)
f=open(query)
l=str(os.fstat(f.fileno()).st_size)
response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
return [l]

also why must I open the file a second time to know how big it is ?

 

[Tim Chase]

I want the file pointer set to 100 and overwrite everything from there
[snip]

def application(environ, response):
query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
offset=[]
for r in range: offset.append(r.split('-'))
with open(query,'w+') as f:
f.seek(int(offset[0][0]))
while True:
chunk=environ['wsgi.input'].read(8192).decode('latin1')
if not chunk: break
f.write(chunk)
f=open(query)
l=str(os.fstat(f.fileno()).st_size)
response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
return [l]

A couple items of note:

- you don't open the file in binary mode -- seek is more reliable
in binary mode

- if you want to lop off the rest of the file, use f.truncate()

An example:

# create the initial file
# demonstrate that it worked

also why must I open the file a second time to know how big it is ?

Likely the output has been buffered. You can try using

f.flush() # write all the data to the disk first
size = os.fstat(f.fileno()).st_size

which seems to do the trick for me.

-tkc

 

[gert]

I want the file pointer set to 100 and overwrite everything from there [snip]
def application(environ, response):
    query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
    range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
    offset=[]
    for r in range: offset.append(r.split('-'))
    with open(query,'w+') as f:
         f.seek(int(offset[0][0]))
         while True:
             chunk=environ['wsgi.input'].read(8192).decode('latin1')
             if not chunk: break
             f.write(chunk)
    f=open(query)
    l=str(os.fstat(f.fileno()).st_size)
    response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
    return [l]

A couple items of note:

- you don't open the file in binary mode -- seek is more reliable
in binary mode

- if you want to lop off the rest of the file, use f.truncate()

An example:

# create the initial file
 >>> f = file('zzz.zzz', 'wb+')
 >>> f.write('abcdefghijklmnop')
 >>> f.close()

 >>> f = file('zzz.zzz', 'ab+')
 >>> f.read() # show the existing content
'abcdefghijklmnop'
 >>> f.seek(5) # seek to the desired offset
 >>> f.truncate() # throw away everything after here
 >>> f.write('zyx') # write the new data at pos=5
 >>> f.close()

# demonstrate that it worked
 >>> f = file('zzz.zzz', 'rb')
 >>> f.read()
'abcdezyx'
 >>> f.close()

also why must I open the file a second time to know how big it is ?

Likely the output has been buffered.  You can try using

   f.flush() # write all the data to the disk first
   size = os.fstat(f.fileno()).st_size

which seems to do the trick for me.

-tkc

Doh! my curl was wrong, thanks

curl -C 100 upload2.wsgi http://192.168.2.17/appwsgi/wsgi/upload2.wsgi
-v

 

[Graham Dumpleton]

I want the file pointer set to 100 and overwrite everything from there [snip]
def application(environ, response):
    query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
    range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
    offset=[]
    for r in range: offset.append(r.split('-'))
    with open(query,'w+') as f:
         f.seek(int(offset[0][0]))
         while True:
             chunk=environ['wsgi.input'].read(8192).decode('latin1')
             if not chunk: break
             f.write(chunk)
    f=open(query)
    l=str(os.fstat(f.fileno()).st_size)
    response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
    return [l]

A couple items of note:

- you don't open the file in binary mode -- seek is more reliable
in binary mode

If my memory is right, if file is opened in binary mode, also wouldn't
need to be decoding the WSGI input stream as latin-1 to get a string.
Instead can just deal with bytes and write bytes to file.

Graham

 

[gert]

I want the file pointer set to 100 and overwrite everything from there [snip]
def application(environ, response):
    query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
    range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
    offset=[]
    for r in range: offset.append(r.split('-'))
    with open(query,'w+') as f:
         f.seek(int(offset[0][0]))
         while True:
             chunk=environ['wsgi.input'].read(8192).decode('latin1')
             if not chunk: break
             f.write(chunk)
    f=open(query)
    l=str(os.fstat(f.fileno()).st_size)
    response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
    return [l]

A couple items of note:

- you don't open the file in binary mode -- seek is more reliable
in binary mode

If my memory is right, if file is opened in binary mode, also wouldn't
need to be decoding the WSGI input stream as latin-1 to get a string.
Instead can just deal with bytes and write bytes to file.

Graham

- if you want to lop off the rest of the file, use f.truncate()

An example:

# create the initial file
 >>> f = file('zzz.zzz', 'wb+')
 >>> f.write('abcdefghijklmnop')
 >>> f.close()

 >>> f = file('zzz.zzz', 'ab+')
 >>> f.read() # show the existing content
'abcdefghijklmnop'
 >>> f.seek(5) # seek to the desired offset
 >>> f.truncate() # throw away everything after here
 >>> f.write('zyx') # write the new data at pos=5
 >>> f.close()

# demonstrate that it worked
 >>> f = file('zzz.zzz', 'rb')
 >>> f.read()
'abcdezyx'
 >>> f.close()

Likely the output has been buffered.  You can try using

   f.flush() # write all the data to the disk first
   size = os.fstat(f.fileno()).st_size

which seems to do the trick for me.
-tkc

Works thanks

curl -C 10 -T upload2.wsgi http://192.168.2.17/appwsgi/wsgi/upload2.wsgi
--header "Transfer-Encoding: chunked" -v

import os

def application(environ, response):
#query=environ.get['QUERY_STRING']
#print (query, file=environ['wsgi.errors'])
query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
range=environ.get('HTTP_CONTENT_RANGE','bytes 0-').replace('bytes
','').split('/')[0].split(',')
offset=[]
for r in range: offset.append(r.split('-'))
with open(query,'rb+') as f:
f.seek(int(offset[0][0]))
if environ['REQUEST_METHOD']=='PUT':
f.truncate()
while True:
chunk=environ['wsgi.input'].read(8192)
if not chunk: break
f.write(chunk)
f.flush()
l=str(os.fstat(f.fileno()).st_size)
response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
return [l]

 

[gert]

I want the file pointer set to 100 and overwrite everything from there
[snip]
def application(environ, response):
    query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
    range=environ.get('HTTP_RANGE','bytes=0-').replace
('bytes=','').split(',')
    offset=[]
    for r in range: offset.append(r.split('-'))
    with open(query,'w+') as f:
         f.seek(int(offset[0][0]))
         while True:
             chunk=environ['wsgi.input'].read(8192)..decode('latin1')
             if not chunk: break
             f.write(chunk)
    f=open(query)
    l=str(os.fstat(f.fileno()).st_size)
    response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
    return [l]
A couple items of note:
- you don't open the file in binary mode -- seek is more reliable
in binary mode

If my memory is right, if file is opened in binary mode, also wouldn't
need to be decoding the WSGI input stream as latin-1 to get a string.
Instead can just deal with bytes and write bytes to file.

Works thanks

curl -C 10 -T upload2.wsgihttp://192.168.2.17/appwsgi/wsgi/upload2.wsgi
--header "Transfer-Encoding: chunked" -v

import os

def application(environ, response):
    #query=environ.get['QUERY_STRING']
    #print (query, file=environ['wsgi.errors'])
    query=os.path.join(os.path.dirname(__file__),'teeeeeeeeeemp')
    range=environ.get('HTTP_CONTENT_RANGE','bytes 0-').replace('bytes
','').split('/')[0].split(',')
    offset=[]
    for r in range: offset.append(r.split('-'))
    with open(query,'rb+') as f:
         f.seek(int(offset[0][0]))
         if environ['REQUEST_METHOD']=='PUT':
             f.truncate()
             while True:
                 chunk=environ['wsgi.input'].read(8192)
                 if not chunk: break
                 f.write(chunk)
         f.flush()
         l=str(os.fstat(f.fileno()).st_size)
    response('200 OK', [('Content-Type', 'text/plain'), ('Content-
Length', str(len(l)))])
    return [l]

Update it works on mod_wsgi but not on wsgiref.simple_server

C:\Users\gert\Desktop\hg\appwsgi\wsgi>curl -T upload2.wsgi
http://localhost/appwsgi/wsgi/upload2.wsg
i -v
* About to connect() to localhost port 80 (#0)
* Trying 127.0.0.1... connected
* Connected to localhost (127.0.0.1) port 80 (#0)

PUT /appwsgi/wsgi/upload2.wsgi HTTP/1.1
User-Agent: curl/7.19.4 (amd64-pc-win32) libcurl/7.19.4 OpenSSL/0.9.8j zlib/1.2.3
Host: localhost
Accept: */*
Content-Length: 869
Expect: 100-continue

* Done waiting for 100-continue

I not getting 100-continues ?