Commit | Line | Data |
---|---|---|
7edc52ec | 1 | @(#)README 3.5 %G% |
84a5ea18 | 2 | |
533eb3f8 EW |
3 | Compilation notes: |
4 | ||
7c38ad4d | 5 | There is only one compiler option: |
84a5ea18 | 6 | |
115fa6f8 EW |
7 | mc68000 use 68000 byte ordering |
8 | It should already be defined in the preprocessor. | |
84a5ea18 | 9 | |
7c38ad4d | 10 | The file local.h contains locally tunable constants. |
84a5ea18 | 11 | |
533eb3f8 EW |
12 | The makefile should be updated with mkmf. The only library it needs |
13 | is termcap (and jobs for 4.1). | |
84a5ea18 | 14 | |
7c38ad4d | 15 | Window only runs on 4.2 machines. |
84a5ea18 | 16 | |
84a5ea18 | 17 | |
533eb3f8 EW |
18 | A few notes about the internals: |
19 | ||
20 | The window package. Windows are opened by calling wwopen(). | |
21 | Wwwrite() is the primitive for writing to windows. Wwputc(), wwputs(), | |
22 | and wwprintf() are also supported. Some of the outputs to windows are | |
23 | delayed. Wwupdate() updates the terminal to match the internal screen | |
24 | buffer. Wwspawn() spawns a child process on the other end of a window, | |
25 | with it's environment tailored to the window. Visible windows are | |
26 | doubly linked in the order of their overlap. Wwadd() inserts a window | |
115fa6f8 EW |
27 | into the list at a given place. Wwdelete() deletes it. Windows not in |
28 | the list are not visible, though wwwrite() still works. | |
533eb3f8 EW |
29 | |
30 | Most functions return -1 on error. Wwopen() returns the null | |
115fa6f8 EW |
31 | pointer. An error number is saved in wwerrno. Wwerror() returns an |
32 | error string based on wwerrno suitable for printing. | |
533eb3f8 EW |
33 | |
34 | The terminal drivers perform all output to the physical terminal, | |
35 | including special functions like character and line insertion and | |
36 | deletion. The window package keeps a list of known terminals. At | |
37 | initialization time, the terminal type is matched against the list to | |
38 | find the right terminal driver to use. The last driver, the generic | |
39 | driver, matches all terminals and uses the termcap database. The | |
40 | interface between the window package the terminal driver is the `tt' | |
41 | structure. It contains pointers to functions to perform special | |
42 | functions and terminal output, as well as flags about the | |
43 | characteristics of the terminal. | |
44 | ||
115fa6f8 EW |
45 | The IO system is semi-synchronous. Terminal input is signal |
46 | driven, and everything else is done synchronously with a single | |
47 | select(). | |
533eb3f8 | 48 | |
115fa6f8 EW |
49 | Normally, in both conversation mode and command mode, window |
50 | sleeps in a select() in wwiomux() waiting for data from the | |
51 | pseudo-terminals. At the same time, terminal input causes SIGIO which | |
52 | is caught by wwrint(). The select() returns when at least one of the | |
53 | pseudo-terminals becomes ready for reading. | |
533eb3f8 | 54 | |
115fa6f8 EW |
55 | Wwrint() is the interrupt handler for tty input. It reads input |
56 | into a linear buffer accessed through four pointers: | |
533eb3f8 EW |
57 | |
58 | +-------+--------------+----------------+ | |
59 | | empty | data | empty | | |
60 | +-------+--------------+----------------+ | |
61 | ^ ^ ^ ^ | |
62 | | | | | | |
63 | wwib wwibp wwibq wwibe | |
64 | ||
115fa6f8 EW |
65 | Wwrint() appends characters at the end and increments wwibq (*wwibq++ = |
66 | c), and characters are taken from the buffer at wwibp using the | |
67 | wwgetc() and wwpeekc() macros. As is the convention in C, wwibq and | |
68 | wwibe point to one position beyond the end. In addition, wwrint() will | |
69 | do a longjmp(wwjmpbuf) if wwsetjmp is true. This is used by wwiomux() | |
70 | to interrupt the select() which would otherwise resume after the | |
533eb3f8 EW |
71 | interrupt. The macro wwinterrupt() returns true if the input buffer is |
72 | non-empty. Wwupdate(), wwwrite(), and wwiomux() check this condition | |
73 | and will return at the first convenient opportunity when it becomes | |
74 | true. In the case of wwwrite(), the flag ww_nointr in the window | |
75 | structure overrides this. This feature allows the user to interrupt | |
115fa6f8 EW |
76 | lengthy outputs safely. The structure of the input buffer is designed |
77 | to avoid race conditions without blocking interrupts. | |
533eb3f8 EW |
78 | |
79 | Wwiomux() copies pseudo-terminal outputs into their corresponding | |
80 | windows. Without anything to do, it blocks in a select(), waiting for | |
81 | read ready on pseudo-terminals. Reads are done into per-window buffers | |
82 | in the window structures. When there is at least one buffer non-empty, | |
83 | wwiomux() finds the top most of these windows and writes it using | |
115fa6f8 EW |
84 | wwwrite(). Then the process is repeated. A non-blocking select() is |
85 | done after a wwwrite() to pick up any output that may have come in | |
86 | during the write, which may take a long time. Specifically, we use | |
87 | this to stop output or flush buffer when a pseudo-terminal tells us to | |
88 | (we use pty packet mode). The select() blocks only when all of the | |
89 | windows' buffers are empty. A wwupdate() is done prior to this, which | |
90 | is the only time the screen is guaranteed to be completely up to date. | |
91 | Wwiomux() loops until wwinterrupt() becomes true. | |
92 | ||
93 | The top level routine for all this is mloop(). In conversation | |
94 | mode, it simply calls wwiomux(), which only returns when input is | |
95 | available. The input buffer is then written to the pseudo-terminal of | |
96 | the current window. If the escape character is found in the input, | |
97 | command mode is entered. Otherwise, the process is repeated. In | |
98 | command mode, control is transferred to docmd() which returns only when | |
99 | conversation mode is reentered. Docmd() and other command processing | |
100 | routines typically wait for input in a loop: | |
101 | ||
102 | while (wwpeekc() < 0) | |
533eb3f8 EW |
103 | wwiomux(); |
104 | ||
115fa6f8 | 105 | When the loop terminates, wwgetc() is used to read the input buffer. |
533eb3f8 EW |
106 | |
107 | Output to the physical terminal is handled by the lowest level | |
108 | routines of the window package, in the files ttoutput.c and tt.h. The | |
115fa6f8 EW |
109 | standard IO package is not used, to get better control over buffering |
110 | and to use non-blocking reads in wwrint(). The buffer size is set to | |
533eb3f8 EW |
111 | approximately one second of output time, based on the baudrate. |
112 | ||
113 | The result of all this complexity is faster response time, | |
114 | especially in output stopping and flushing. Wwwrite() checks | |
115 | wwinterrupt() after every line. It also calls wwupdate() for each line | |
116 | it writes. The output buffer is limited to one second of output time. | |
117 | Thus, there is usually only a delay of one to two lines plus one second | |
118 | after a ^C or ^S. Also, commands that produce lengthy output can be | |
119 | aborted without actually showing all of it on the terminal. (Try the | |
115fa6f8 | 120 | '?' command followed by escape immediately.) |