| Guido van Rossum | 741c81a | 1992-07-13 14:40:45 +0000 | [diff] [blame^] | 1 | # A class that makes each part of a multipart message "feel" like an |
| 2 | # ordinary file, as long as you use fp.readline(). Allows recursive |
| 3 | # use, for nested multipart messages. Probably best used together |
| 4 | # with module mimetools. |
| 5 | # |
| 6 | # Suggested use: |
| 7 | # |
| 8 | # real_fp = open(...) |
| 9 | # fp = MultiFile().init(real_fp) |
| 10 | # |
| 11 | # "read some lines from fp" |
| 12 | # fp.push(separator) |
| 13 | # while 1: |
| 14 | # "read lines from fp until it returns an empty string" (A) |
| 15 | # if not fp.next(): break |
| 16 | # fp.pop() |
| 17 | # "read remaining lines from fp until it returns an empty string" |
| 18 | # |
| 19 | # The latter sequence may be used recursively at (A). |
| 20 | # It is also allowed to use multiple push()...pop() sequences. |
| 21 | # Note that if a nested multipart message is terminated by a separator |
| 22 | # for an outer message, this is not reported, even though it is really |
| 23 | # illegal input. |
| 24 | |
| 25 | import sys |
| 26 | import string |
| 27 | |
| 28 | err = sys.stderr.write |
| 29 | |
| 30 | Error = 'multifile.Error' |
| 31 | |
| 32 | class MultiFile: |
| 33 | # |
| 34 | def init(self, fp): |
| 35 | self.fp = fp |
| 36 | self.stack = [] # Grows down |
| 37 | self.level = 0 |
| 38 | self.last = 0 |
| 39 | self.start = self.fp.tell() |
| 40 | self.posstack = [] # Grows down |
| 41 | return self |
| 42 | # |
| 43 | def tell(self): |
| 44 | if self.level > 0: |
| 45 | return self.lastpos |
| 46 | return self.fp.tell() - self.start |
| 47 | # |
| 48 | def seek(self, pos): |
| 49 | if not 0 <= pos <= self.tell() or \ |
| 50 | self.level > 0 and pos > self.lastpos: |
| 51 | raise Error, 'bad MultiFile.seek() call' |
| 52 | self.fp.seek(pos + self.start) |
| 53 | self.level = 0 |
| 54 | self.last = 0 |
| 55 | # |
| 56 | def readline(self): |
| 57 | if self.level > 0: return '' |
| 58 | line = self.fp.readline() |
| 59 | if not line: |
| 60 | self.level = len(self.stack) |
| 61 | self.last = (self.level > 0) |
| 62 | if self.last: |
| 63 | err('*** Sudden EOF in MultiFile.readline()\n') |
| 64 | return '' |
| 65 | if line[:2] <> '--': return line |
| 66 | n = len(line) |
| 67 | k = n |
| 68 | while k > 0 and line[k-1] in string.whitespace: k = k-1 |
| 69 | mark = line[2:k] |
| 70 | if mark[-2:] == '--': mark1 = mark[:-2] |
| 71 | else: mark1 = None |
| 72 | for i in range(len(self.stack)): |
| 73 | sep = self.stack[i] |
| 74 | if sep == mark: |
| 75 | self.last = 0 |
| 76 | break |
| 77 | elif mark1 <> None and sep == mark1: |
| 78 | self.last = 1 |
| 79 | break |
| 80 | else: |
| 81 | return line |
| 82 | # Get here after break out of loop |
| 83 | self.lastpos = self.tell() - len(line) |
| 84 | self.level = i+1 |
| 85 | if self.level > 1: |
| 86 | err('*** Missing endmarker in MultiFile.readline()\n') |
| 87 | return '' |
| 88 | # |
| 89 | def next(self): |
| 90 | while self.readline(): pass |
| 91 | if self.level > 1 or self.last: |
| 92 | return 0 |
| 93 | self.level = 0 |
| 94 | self.last = 0 |
| 95 | self.start = self.fp.tell() |
| 96 | return 1 |
| 97 | # |
| 98 | def push(self, sep): |
| 99 | if self.level > 0: |
| 100 | raise Error, 'bad MultiFile.push() call' |
| 101 | self.stack.insert(0, sep) |
| 102 | self.posstack.insert(0, self.start) |
| 103 | self.start = self.fp.tell() |
| 104 | # |
| 105 | def pop(self): |
| 106 | if self.stack == []: |
| 107 | raise Error, 'bad MultiFile.pop() call' |
| 108 | if self.level <= 1: |
| 109 | self.last = 0 |
| 110 | else: |
| 111 | abslastpos = self.lastpos + self.start |
| 112 | self.level = max(0, self.level - 1) |
| 113 | del self.stack[0] |
| 114 | self.start = self.posstack[0] |
| 115 | del self.posstack[0] |
| 116 | if self.level > 0: |
| 117 | self.lastpos = abslastpos - self.start |
| 118 | # |