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1.1 root 1: /* Copyright (c) 1981 Regents of the University of California */
2: /* sccs id: @(#)ex_temp.h 7.3 8/2/81 */
3: /*
4: * The editor uses a temporary file for files being edited, in a structure
5: * similar to that of ed. The first block of the file is used for a header
6: * block which guides recovery after editor/system crashes.
7: * Lines are represented in core by a pointer into the temporary file which
8: * is packed into 16 bits (32 on VMUNIX). All but the low bit index the temp
9: * file; the last is used by global commands. The parameters below control
10: * how much the other bits are shifted left before they index the temp file.
11: * Larger shifts give more slop in the temp file but allow larger files
12: * to be edited.
13: *
14: * The editor does not garbage collect the temporary file. When a new
15: * file is edited, the temporary file is rather discarded and a new one
16: * created for the new file. Garbage collection would be rather complicated
17: * in ex because of the general undo, and in any case would require more
18: * work when throwing lines away because marks would have be carefully
19: * checked before reallocating temporary file space. Said another way,
20: * each time you create a new line in the temporary file you get a unique
21: * number back, and this is a property used by marks.
22: *
23: * The following temp file parameters allow 256k bytes in the temporary
24: * file. By changing to the numbers in comments you can get 512k.
25: * For VMUNIX you get more than you could ever want.
26: * VMUNIX uses long (32 bit) integers giving much more
27: * space in the temp file and no waste. This doubles core
28: * requirements but allows files of essentially unlimited size to be edited.
29: */
30: #ifndef VMUNIX
31: #define BLKMSK 0777 /* 01777 */
32: #define BNDRY 8 /* 16 */
33: #define INCRMT 0200 /* 0100 */
34: #define LBTMSK 0770 /* 0760 */
35: #define NMBLKS 506 /* 1018 */
36: #define OFFBTS 7 /* 6 */
37: #define OFFMSK 0177 /* 077 */
38: #define SHFT 2 /* 3 */
39: #else
40: #define BLKMSK 077777
41: #define BNDRY 2
42: #define INCRMT 02000
43: #define LBTMSK 01776
44: #define NMBLKS 077770
45: #define OFFBTS 10
46: #define OFFMSK 01777
47: #define SHFT 0
48: #endif
49:
50: /*
51: * The editor uses three buffers into the temporary file (ed uses two
52: * and is very similar). These are two read buffers and one write buffer.
53: * Basically, the editor deals with the file as a sequence of BUFSIZ character
54: * blocks. Each block contains some number of lines (and lines
55: * can run across block boundaries.
56: *
57: * New lines are written into the last block in the temporary file
58: * which is in core as obuf. When a line is needed which isn't in obuf,
59: * then it is brought into an input buffer. As there are two, the choice
60: * is to take the buffer into which the last read (of the two) didn't go.
61: * Thus this is a 2 buffer LRU replacement strategy. Measurement
62: * shows that this saves roughly 25% of the buffer reads over a one
63: * input buffer strategy. Since the editor (on our VAX over 1 week)
64: * spends (spent) roughly 30% of its time in the system read routine,
65: * this can be a big help.
66: */
67: var bool hitin2; /* Last read hit was ibuff2 not ibuff */
68: var bool ichang2; /* Have actually changed ibuff2 */
69: var bool ichanged; /* Have actually changed ibuff */
70: var short iblock; /* Temp file block number of ibuff (or -1) */
71: var short iblock2; /* Temp file block number of ibuff2 (or -1) */
72: var short ninbuf; /* Number useful chars left in input buffer */
73: var short nleft; /* Number usable chars left in output buffer */
74: var short oblock; /* Temp file block number of obuff (or -1) */
75: #ifndef VMUNIX
76: var short tline; /* Current temp file ptr */
77: #else
78: var int tline;
79: #endif
80:
81: var char ibuff[BUFSIZ];
82: var char ibuff2[BUFSIZ];
83: var char obuff[BUFSIZ];
84:
85: /*
86: * Structure of the descriptor block which resides
87: * in the first block of the temporary file and is
88: * the guiding light for crash recovery.
89: *
90: * As the Blocks field below implies, there are temporary file blocks
91: * devoted to (some) image of the incore array of pointers into the temp
92: * file. Thus, to recover from a crash we use these indices to get the
93: * line pointers back, and then use the line pointers to get the text back.
94: * Except for possible lost lines due to sandbagged I/O, the entire
95: * file (at the time of the last editor "sync") can be recovered from
96: * the temp file.
97: */
98:
99: /* This definition also appears in expreserve.c... beware */
100: struct header {
101: time_t Time; /* Time temp file last updated */
102: int Uid;
103: #ifndef VMUNIX
104: short Flines; /* Number of lines in file */
105: #else
106: int Flines;
107: #endif
108: char Savedfile[FNSIZE]; /* The current file name */
109: short Blocks[LBLKS]; /* Blocks where line pointers stashed */
110: };
111: var struct header H;
112:
113: #define uid H.Uid
114: #define flines H.Flines
115: #define savedfile H.Savedfile
116: #define blocks H.Blocks
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