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1 .H0 "Work Report
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2 .P
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3 foo
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4 .P
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5 bar
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6
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meillo@12
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7 .H1 "Removal of Code Relicts
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8 .P
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9 The code base of mmh originates in the late 70s, had been extensively
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10 worked on in the mid 80s, and had been partly reorganized and extended
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11 in the 90s. Relicts of all those times had gathered in the code base.
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12 My goal was to remove any ancient code parts. One part of the task was
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13 converting obsolete code constructs to standard constructs, the other part
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14 was dropping obsolete functions.
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15 .P
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16 As I'm not even thirty years old and have no more than seven years of
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17 Unix experience, I needed to learn about the history in retroperspective.
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18 Older people likely have used those ancient constructs themself
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19 and have suffered from their incompatiblities and have longed for
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20 standardization. Unfortunately, I have only read that others had done so.
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21 This put me in a much more difficult positions when working on the old
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22 code. I needed to recherche what other would have known by heart from
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23 experience. All my programming experience comes from a time past ANSI C
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24 and past POSIX. Although I knew about the times before, I took the
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25 current state implicitely for granted most of the time.
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26 .P
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27 Being aware of
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28 these facts, I rather let people with more historic experience solve the
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29 task of converting the ancient code constructs to standardized ones.
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30 Luckily, Lyndon Nerenberg focused on this task at the nmh project.
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31 He converted large parts of the code to POSIX constructs, removing
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32 the conditionals compilation for now standardized features.
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33 I'm thankful for this task being solved. I only pulled the changes into
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34 mmh.
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35 .P
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36 The other task of dropping ancient functionality to remove old code,
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37 I did myself, though. My position to strip mmh to the bare minimum of
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38 frequently used features is much more revolutional than the nmh community
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39 sees it. Without the need to justify my decisions, I was able to quickly
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40 remove code I considered ancient. The need to discuss my decisions with
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41 peers likely would have slowed this process down. Of course, I did research
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42 if a particular feature really should be dropped. Having not had any
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43 contact to this feature within my computer life was a first indicator to
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44 drop it, but I also asked others and searched the literature for modern
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45 usage of the feature. If it appeared to be truly ancient, I dropped it.
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46 The reason for dropping is always part of the commit message in the
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47 version control system. Thus, it is easy for others to check their
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48 view on the topic with mine and possibly to argue for reinclusion.
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49
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50 .U2 "MMDF maildrop support
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51 .P
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52 I did drop any support for the MMDF maildrop format. This type of format
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53 is conceptionally similar to the mbox format, but uses four bytes with
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54 value 1 (\fL^A^A^A^A\fP) as message delimiter,
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55 instead of the string ``\fLFrom\0\fP''.
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56 Due to the similarity and mbox being the de-facto standard maildrop
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57 format on Unix, but also due to the larger influence of Sendmail than MMDF,
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58 the MMDF maildrop format had vanished.
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59 .P
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60 The simplifications within the code were only moderate. Switches could
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61 be removed from tools like
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62 .L packf ,
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63 which generate packed mailboxes. Only one packed mailbox format remained:
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64 mbox.
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65 The most important changes affect the equally named mail parsing routine in
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66 .L sbr/m_getfld.c .
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67 The direct MMDF code had been removed, but as now only one packed mailbox
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68 format is left, code structure simplifications are likely possible.
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69 The reason why they are still outstanding is the heavily optimized code
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70 of \fLm_getfld()\fP. Changes beyond a small local scope \(en
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71 which restructuring in its core is \(en cause a high risk of damaging
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72 the intricate workings of the optimized code. This problem is know
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73 to the developers of nmh, too. They also avoid touching this minefield
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74 if possible.
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75
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76 .U2 "UUCP Bang Paths
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77 .P
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78 More questionably than the former topic is the removal of support for the
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79 UUCP bang path address style. However, the user may translate the bang
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80 paths on retrieval to Internet addresses and the other way on posting
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81 messages. The former can be done my an MDA like procmail; the latter
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82 by a sendmail wrapper. This would ensure that any address handling would
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83 work as expected. However, it might just work well without any
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84 such modifications, as mmh does not touch addresses much, in general.
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85 But I can't ensure as I have never used an environment with bang paths.
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86 Also, the behavior might break at any point in further development.
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87
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88 .U2 "Hardcopy terminal support
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89 .P
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90 More of a funny anecdote is the remaining of a check for printing to a
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91 hardcopy terminal until Spring 2012, when I finally removed it.
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92 I surely would be very happy to see such a terminal in action, maybe
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93 actually being able to work on it, but I fear my chances are null.
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94 .P
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95 The check only prevented a pager to be placed between the outputting
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96 program (\fLmhl\fP) and the terminal. This could have been ensured with
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97 the \fL-nomoreproc\fP at the command line statically, too.
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98
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99 .U2 "Removed support for header fields
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100 .P
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101 The `Encrypted' header had been introduced by RFC\^822, but already
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102 marked legacy in RFC 2822. It was superseded by FIXME.
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103 Mmh does no more support this header.
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104 .P
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105 `Content-MD5' headers were introduced by RFC\^1864. They provide only
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106 a verification of data corruption during the transfer. By no means can
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107 they ensure verbatim end-to-end delivery of the contents. This is clearly
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108 stated in the RFC. The proper approach to provide verificationability
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109 of content in an end-to-end relationship is the use of digital cryptography
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110 (RFCs FIXME). On the other hand, transfer protocols should ensure the
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111 integrity of the transmission. In combinations these two approaches
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112 make the `Content-MD5' header field useless. In consequence, I removed
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113 the support for it. By this removal, MD5 computation is not needed
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114 anywhere in mmh. Hence, over 500 lines of code were removed by this one
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115 change. Even if the `Content-MD5' header field is useful sometimes,
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116 I value its usefulnes less than the improvement in maintainability, caused
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117 by the removal.
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118
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119
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120 .H1 "Draft and Trash Folders
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121 .U2 "Draft Folder
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122 .P
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123 Historically, MH provided exactly one draft message, named `\fLdraft\fP' and
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124 being located in the MH directory. When starting to compose another message
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125 before the former one was sent, the user had been questioned wether to use,
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126 refile or replace the old draft. Working on multiple drafts at the same time
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127 was impossible. One could only work on them in alteration by refiling the
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128 previous one to some directory and fetching some other one for reediting.
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129 This manual draft management needed to be done each time the user wanted
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130 to switch between editing one draft to editing another.
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131 .P
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132 To allow true parallel editing of drafts, in a straight forward way, the
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133 draft folder facility exists. It had been introduced already in July 1984
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134 by Marshall T. Rose. The facility was deactivated by default.
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135 Even in nmh, the draft folder facility remained deactivated by default.
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136 At least, Richard Coleman added the man page \fImh-draft(5)\fP to document
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137 the feature well.
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138 .P
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139 The only advantage of not using the draft folder facility is the static
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140 name of the draft file. This could be an issue for MH frontends like mh-e.
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141 But as they likely want to provide working on multiple drafts in parallel,
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142 the issue is only concerning compatibility. The aim of nmh to stay compatible
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143 prevented the default activation of the draft folder facility.
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144 .P
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145 On the other hand, a draft folder is the much more natural concept than
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146 a draft message. MH's mail storage consists of folders and messages,
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147 the messages named with ascending numbers. A draft message breaks with this
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148 concept by introducing a message in a file named ``\fLdraft\fP''. This draft
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149 message is special. It can not be simply listed with the available tools,
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150 but instead requires special switches. I.e. corner-cases were
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151 introduced. A draft folder, in contrast, does not introduce such
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152 corner-cases. The available tools can operate on the messages within that
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153 folder like on any messages within any mail folders. The only difference
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154 is the fact that the default folder for \fLsend\fP is the draft folder,
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155 instead of the current folder, like for all other tools.
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156 .P
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157 The trivial part of the change was activating the draft folder facility
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158 by default and setting a default name for this folder. Obviously, I chose
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159 the name ``\fL+drafts\fP''. This made the \fL\-draftfolder\fP and
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160 \fL\-draftmessage\fP switches useless, and I could remove them.
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161 The more difficult but also the part that showed the real improvement,
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162 was updating the tools to the new concept. \fL\-draft\fP switches could
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163 be dropped, as operating on a draft message became indistinguishable to
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164 operating on any other message for the tools. \fLcomp\fP still has its
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165 \fL\-use\fP switch for switching between its two modes: (1) Compose a new
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166 draft, possibly by taking some existing message as a form. (2) Modify
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167 an existing draft. In either case, the behavior of \fLcomp\fP is
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168 deterministic. There is no more need to query the user. I consider this
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169 a major improvement. By making \fLsend\fP simply operate on the current
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170 message in the draft folder by default, with message and folder both
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171 overridable by specifying them on the command line, it is now possible
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172 to send a draft anywhere within the storage by simply specifying its folder
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173 and name.
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174 .P
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175 All theses changes converted special cases to regular cases, thus
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176 simplifying the tools and increasing the flexibility.
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177
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178 .U2 "Trash Folder
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179 .P
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180 Similar to the situation for drafts is the situation for removed messages.
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181 Historically, a message was deleted by renaming. A specific
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182 \fIbackup prefix\fP, often comma (\fL,\fP) or hash (\fL#\fP),
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183 being prepended to the file name. Thus, MH wouldn't recognize the file
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184 as a message anymore, as only files whose name consists of digits only
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185 are treated as messages. The removed messages remained as files in the
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186 same directory and needed some maintenance job to truly delete them after
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187 some grace time. Usually, by running a command similar to
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188 .DS
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189 find /home/user/Mail \-ctime +7 \-name ',*' | xargs rm
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190 .DE
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191 in a cron job. Within the grace time interval
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192 the original message could be restored by stripping the
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193 the backup prefix from the file name. If however, the last message of
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194 a folder is been removed \(en say message `\fL6\fP' becomes file
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195 `\fL,6\fP' \(en and a new message enters the same folder, thus the same
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196 numbered being given again \(en in our case `\fL6\fP' \(en, if that one
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197 is removed too, then the backup of the former message gets overwritten.
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198 Thus, the ability to restore removed messages does not only depend on
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199 the ``sweeping cron job'' but also on the removing of further messages.
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200 This is undesireable, because the real mechanism is hidden from the user
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201 and the concequences of further removals are not always obvious.
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202 Further more, the backup files are scattered within the whole mail
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203 storage, instead of being collected at one place.
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204 .P
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205 To improve the situation, the profile entry \fIrmmproc\fP
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206 (previously named \fIDelete-Prog\fP) was introduced, very early.
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207 It could be set to any command, which would care for the mail removal
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208 instead of taking the default action, described above.
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209 Refiling the to-be-removed files to some wastebin folder was a common
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210 example. Nmh's man page for \fLrmm(1)\fP proposes `\fLrefile +d\fP'
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211 to move messages to the wastebin and `\fLrm `mhpath +d all`\fP'
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212 the empty the wastebin.
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213 Managing the message removal this way is a sane approach. It keeps
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214 the removed messages in one place, makes it easy to remove the backup
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215 files, and, most important, enables the user to use the tools of MH
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216 itself to operate on the removed messages. One can \fLscan\fP them,
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217 \fLshow\fP them, and restore them with \fLrefile(1)\fP. There's no more
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218 need to use \fLmhpath\fP to switch over from MH tools to Unix tools
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219 \(en MH can do it all itself.
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220 .P
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221 This apporach is matches perfect with the concepts of MH, thus making
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222 it powerful. Hence, I made it the default. And even more, I also
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223 removed the old backup prefix approach, as it is clearly less powerful.
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224 Keeping unused alternative in the code is a bad choice as they likely
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225 gather bugs, by not being constantly tested. Also, the increased code
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226 size and more conditions crease the maintenance costs. By strictly
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227 converting to the trash folder approach, I simplified the code base.
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228 \fLrmm(1)\fP calls \fLrefile(1)\fP internally to move the to-be-removed
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229 message to the trash folder (`\fL+trash\fP' by default). Messages
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230 there can be operated on like on any other message in the storage.
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231 The sweep clean, one can use `\fLrmm \-unlink +trash a\fP', where
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232 the `\fL\-unlink\fP' switch causes the files to be truly unliked instead
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233 of moved to the trash folder.
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234
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235
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236 .H1 "MH Directory Split
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237 .P
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238
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239
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240
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241 .H1 "Path Notations
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242 .P
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243 foo
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244
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245 .H1 "Attachments
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246 .P
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247 foo
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248
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249 .H1 "Blind Carbon Copies
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250 .P
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251 foo
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252
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253 .H1 "Good Defaults
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254 .P
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255 foo
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256
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257 .H1 "Modularization
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258 .P
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259 foo
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260
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261 .H1 "Code style
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262 .P
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263 foo
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