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1.1 root 1: /* Copyright (c) 1979 Regents of the University of California */
2: /*
3: * The editor uses a temporary file for files being edited, in a structure
4: * similar to that of ed. The first block of the file is used for a header
5: * block which guides recovery after editor/system crashes.
6: * Lines are represented in core by a pointer into the temporary file which
7: * is packed into 16 bits (32 on VMUNIX). All but the low bit index the temp
8: * file; the last is used by global commands. The parameters below control
9: * how much the other bits are shifted left before they index the temp file.
10: * Larger shifts give more slop in the temp file but allow larger files
11: * to be edited.
12: *
13: * The editor does not garbage collect the temporary file. When a new
14: * file is edited, the temporary file is rather discarded and a new one
15: * created for the new file. Garbage collection would be rather complicated
16: * in ex because of the general undo, and in any case would require more
17: * work when throwing lines away because marks would have be carefully
18: * checked before reallocating temporary file space. Said another way,
19: * each time you create a new line in the temporary file you get a unique
20: * number back, and this is a property used by marks.
21: *
22: * The following temp file parameters allow 256k bytes in the temporary
23: * file. By changing to the numbers in comments you can get 512k.
24: * For VMUNIX you get more than you could ever want.
25: * VMUNIX uses long (32 bit) integers giving much more
26: * space in the temp file and no waste. This doubles core
27: * requirements but allows files of essentially unlimited size to be edited.
28: */
29: #ifndef VMUNIX
30: #define BLKMSK 0777 /* 01777 */
31: #define BNDRY 8 /* 16 */
32: #define INCRMT 0200 /* 0100 */
33: #define LBTMSK 0770 /* 0760 */
34: #define NMBLKS 506 /* 1018 */
35: #define OFFBTS 7 /* 6 */
36: #define OFFMSK 0177 /* 077 */
37: #define SHFT 2 /* 3 */
38: #else
39: #define BLKMSK 077777
40: #define BNDRY 2
41: #define INCRMT 02000
42: #define LBTMSK 01776
43: #define NMBLKS 077770
44: #define OFFBTS 10
45: #define OFFMSK 01777
46: #define SHFT 0
47: #endif
48:
49: /*
50: * The editor uses three buffers into the temporary file (ed uses two
51: * and is very similar). These are two read buffers and one write buffer.
52: * Basically, the editor deals with the file as a sequence of BUFSIZ character
53: * blocks. Each block contains some number of lines (and lines
54: * can run across block boundaries.
55: *
56: * New lines are written into the last block in the temporary file
57: * which is in core as obuf. When a line is needed which isn't in obuf,
58: * then it is brought into an input buffer. As there are two, the choice
59: * is to take the buffer into which the last read (of the two) didn't go.
60: * Thus this is a 2 buffer LRU replacement strategy. Measurement
61: * shows that this saves roughly 25% of the buffer reads over a one
62: * input buffer strategy. Since the editor (on our VAX over 1 week)
63: * spends (spent) roughly 30% of its time in the system read routine,
64: * this can be a big help.
65: */
66: bool hitin2; /* Last read hit was ibuff2 not ibuff */
67: bool ichang2; /* Have actually changed ibuff2 */
68: bool ichanged; /* Have actually changed ibuff */
69: short iblock; /* Temp file block number of ibuff (or -1) */
70: short iblock2; /* Temp file block number of ibuff2 (or -1) */
71: short ninbuf; /* Number useful chars left in input buffer */
72: short nleft; /* Number usable chars left in output buffer */
73: short oblock; /* Temp file block number of obuff (or -1) */
74: #ifndef VMUNIX
75: short tline; /* Current temp file ptr */
76: #else
77: int tline;
78: #endif
79:
80: char ibuff[BUFSIZ];
81: char ibuff2[BUFSIZ];
82: char obuff[BUFSIZ];
83:
84: /*
85: * Structure of the descriptor block which resides
86: * in the first block of the temporary file and is
87: * the guiding light for crash recovery.
88: *
89: * As the Blocks field below implies, there are temporary file blocks
90: * devoted to (some) image of the incore array of pointers into the temp
91: * file. Thus, to recover from a crash we use these indices to get the
92: * line pointers back, and then use the line pointers to get the text back.
93: * Except for possible lost lines due to sandbagged I/O, the entire
94: * file (at the time of the last editor "sync") can be recovered from
95: * the temp file.
96: */
97:
98: /* This definition also appears in expreserve.c... beware */
99: struct header {
100: time_t Time; /* Time temp file last updated */
101: short Uid;
102: #ifndef VMUNIX
103: short Flines; /* Number of lines in file */
104: #else
105: int Flines;
106: #endif
107: char Savedfile[FNSIZE]; /* The current file name */
108: short Blocks[LBLKS]; /* Blocks where line pointers stashed */
109: } H;
110:
111: #define uid H.Uid
112: #define flines H.Flines
113: #define savedfile H.Savedfile
114: #define blocks H.Blocks
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