1 /* Copyright (c) 1981 Regents of the University of California */ 2 /* sccs id: @(#)ex_temp.h 7.3 08/02/81 */ 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 117