Patch by Eric Raymond: add an optional 'seekable' flag to the

MultiFile constructor, and only do the posstack bookkeeping when it is
true.

diff --git a/Lib/multifile.py b/Lib/multifile.py
index 8ba88e46328c056f75c0c034a5a41a277e4bb234..6c80c43ccbaf82d2d0eb7d638206383f91c3c813 100644 (file)
--- a/Lib/multifile.py
+++ b/Lib/multifile.py
@@ -21,6 +21,11 @@
 # Note that if a nested multipart message is terminated by a separator
 # for an outer message, this is not reported, even though it is really
 # illegal input.
+#
+# If seekable is given as 0, the class code will not do the bookeeping
+# it normally attempts in order to make seeks relative to the beginning of the
+# current file part.  This may be useful when using MultiFile with a non-
+# seekable stream object.
 
 import sys
 import string
@@ -31,13 +36,16 @@ Error = 'multifile.Error'
 
 class MultiFile:
        #
-       def __init__(self, fp):
+       seekable = 0
+       def __init__(self, fp, seekable=1):
                self.fp = fp
                self.stack = [] # Grows down
                self.level = 0
                self.last = 0
-               self.start = self.fp.tell()
-               self.posstack = [] # Grows down
+               if seekable:
+                       self.seekable = 1
+                       self.start = self.fp.tell()
+                       self.posstack = [] # Grows down
        #
        def tell(self):
                if self.level > 0:
@@ -88,7 +96,8 @@ class MultiFile:
                else:
                        return line
                # Get here after break out of loop
-               self.lastpos = self.tell() - len(line)
+               if self.seekable:
+                       self.lastpos = self.tell() - len(line)
                self.level = i+1
                if self.level > 1:
                        err('*** Missing endmarker in MultiFile.readline()\n')
@@ -111,15 +120,17 @@ class MultiFile:
                        return 0
                self.level = 0
                self.last = 0
-               self.start = self.fp.tell()
+               if self.seekable:
+                       self.start = self.fp.tell()
                return 1
        #
        def push(self, sep):
                if self.level > 0:
                        raise Error, 'bad MultiFile.push() call'
                self.stack.insert(0, sep)
-               self.posstack.insert(0, self.start)
-               self.start = self.fp.tell()
+               if self.seekable:
+                       self.posstack.insert(0, self.start)
+                       self.start = self.fp.tell()
        #
        def pop(self):
                if self.stack == []:
@@ -130,8 +141,9 @@ class MultiFile:
                        abslastpos = self.lastpos + self.start
                self.level = max(0, self.level - 1)
                del self.stack[0]
-               self.start = self.posstack[0]
-               del self.posstack[0]
-               if self.level > 0:
-                       self.lastpos = abslastpos - self.start
+               if self.seekable:
+                       self.start = self.posstack[0]
+                       del self.posstack[0]
+                       if self.level > 0:
+                               self.lastpos = abslastpos - self.start
        #