1 /*- 2 * Copyright (c) 1980, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.proprietary.c% 6 * 7 * @(#)ex_temp.h 8.1 (Berkeley) 06/09/93 8 */ 9 10 /* 11 * The editor uses a temporary file for files being edited, in a structure 12 * similar to that of ed. The first block of the file is used for a header 13 * block which guides recovery after editor/system crashes. 14 * Lines are represented in core by a pointer into the temporary file which 15 * is packed into 16 bits (32 on VMUNIX). All but the low bit index the temp 16 * file; the last is used by global commands. The parameters below control 17 * how much the other bits are shifted left before they index the temp file. 18 * Larger shifts give more slop in the temp file but allow larger files 19 * to be edited. 20 * 21 * The editor does not garbage collect the temporary file. When a new 22 * file is edited, the temporary file is rather discarded and a new one 23 * created for the new file. Garbage collection would be rather complicated 24 * in ex because of the general undo, and in any case would require more 25 * work when throwing lines away because marks would have be carefully 26 * checked before reallocating temporary file space. Said another way, 27 * each time you create a new line in the temporary file you get a unique 28 * number back, and this is a property used by marks. 29 * 30 * The following temp file parameters allow 256k bytes in the temporary 31 * file. By changing to the numbers in comments you can get 512k. 32 * For VMUNIX you get more than you could ever want. 33 * VMUNIX uses long (32 bit) integers giving much more 34 * space in the temp file and no waste. This doubles core 35 * requirements but allows files of essentially unlimited size to be edited. 36 */ 37 #ifndef VMUNIX 38 #define BLKMSK 0777 /* 01777 */ 39 #define BNDRY 8 /* 16 */ 40 #define INCRMT 0200 /* 0100 */ 41 #define LBTMSK 0770 /* 0760 */ 42 #define NMBLKS 506 /* 1018 */ 43 #define OFFBTS 7 /* 6 */ 44 #define OFFMSK 0177 /* 077 */ 45 #define SHFT 2 /* 3 */ 46 #else 47 #define BLKMSK 077777 48 #define BNDRY 2 49 #define INCRMT 02000 50 #define LBTMSK 01776 51 #define NMBLKS 077770 52 #define OFFBTS 10 53 #define OFFMSK 01777 54 #define SHFT 0 55 #endif 56 57 /* 58 * The editor uses three buffers into the temporary file (ed uses two 59 * and is very similar). These are two read buffers and one write buffer. 60 * Basically, the editor deals with the file as a sequence of BUFSIZ character 61 * blocks. Each block contains some number of lines (and lines 62 * can run across block boundaries. 63 * 64 * New lines are written into the last block in the temporary file 65 * which is in core as obuf. When a line is needed which isn't in obuf, 66 * then it is brought into an input buffer. As there are two, the choice 67 * is to take the buffer into which the last read (of the two) didn't go. 68 * Thus this is a 2 buffer LRU replacement strategy. Measurement 69 * shows that this saves roughly 25% of the buffer reads over a one 70 * input buffer strategy. Since the editor (on our VAX over 1 week) 71 * spends (spent) roughly 30% of its time in the system read routine, 72 * this can be a big help. 73 */ 74 var bool hitin2; /* Last read hit was ibuff2 not ibuff */ 75 var bool ichang2; /* Have actually changed ibuff2 */ 76 var bool ichanged; /* Have actually changed ibuff */ 77 var short iblock; /* Temp file block number of ibuff (or -1) */ 78 var short iblock2; /* Temp file block number of ibuff2 (or -1) */ 79 var short ninbuf; /* Number useful chars left in input buffer */ 80 var short nleft; /* Number usable chars left in output buffer */ 81 var short oblock; /* Temp file block number of obuff (or -1) */ 82 #ifndef VMUNIX 83 var short tline; /* Current temp file ptr */ 84 #else 85 var int tline; 86 #endif 87 88 var char ibuff[BUFSIZ]; 89 var char ibuff2[BUFSIZ]; 90 var char obuff[BUFSIZ]; 91 92 /* 93 * Structure of the descriptor block which resides 94 * in the first block of the temporary file and is 95 * the guiding light for crash recovery. 96 * 97 * As the Blocks field below implies, there are temporary file blocks 98 * devoted to (some) image of the incore array of pointers into the temp 99 * file. Thus, to recover from a crash we use these indices to get the 100 * line pointers back, and then use the line pointers to get the text back. 101 * Except for possible lost lines due to sandbagged I/O, the entire 102 * file (at the time of the last editor "sync") can be recovered from 103 * the temp file. 104 */ 105 106 /* This definition also appears in expreserve.c... beware */ 107 struct header { 108 time_t Time; /* Time temp file last updated */ 109 int Uid; 110 #ifndef VMUNIX 111 short Flines; /* Number of lines in file */ 112 #else 113 int Flines; 114 #endif 115 char Savedfile[FNSIZE]; /* The current file name */ 116 short Blocks[LBLKS]; /* Blocks where line pointers stashed */ 117 }; 118 var struct header H; 119 120 #define uid H.Uid 121 #define flines H.Flines 122 #define savedfile H.Savedfile 123 #define blocks H.Blocks 124