projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 09a0104b BJ |
1 | #include "ex.h" |
| 2 | /* | |
| 3 | * Ex - a text editor | |
| 4 | * Bill Joy UCB June/September 1977 | |
| 5 | * | |
| 6 | * Pointers for lines deleted by the last buffer editing | |
| 7 | * command are salted away between dol and unddol. Unddel | |
| 8 | * marks the line which was before this group prior to the last | |
| 9 | * command. If undap1 != undap2 then the lines from undap1 | |
| 10 | * to undap2-1 were appended by the last command. | |
| 11 | */ | |
| 12 | ||
| 13 | undo(c) | |
| 14 | char c; | |
| 15 | { | |
| 16 | register int i, *jp, *kp; | |
| 17 | int *dolp1, *newdol, *newadot; | |
| 18 | ||
| 19 | if (inglobal) | |
| 20 | error("Can't undo in global@commands"); | |
| 21 | if (!c) | |
| 22 | somechange(); | |
| 23 | change(); | |
| 24 | if (undkind == UNDMOVE) { | |
| 25 | /* | |
| 26 | * Command to be undone is a move command. | |
| 27 | * This is handled as a special case by noting that | |
| 28 | * a move "a,b m c" can be inverted by another move. | |
| 29 | */ | |
| 30 | if ((i = (jp = unddel) - undap2) > 0) { | |
| 31 | /* | |
| 32 | * when c > b inverse is a+(c-b),c m a-1 | |
| 33 | */ | |
| 34 | addr2 = jp; | |
| 35 | addr1 = (jp = undap1) + i; | |
| 36 | unddel = jp-1; | |
| 37 | } else { | |
| 38 | /* | |
| 39 | * when b > c inverse is c+1,c+1+(b-a) m b | |
| 40 | */ | |
| 41 | addr1 = ++jp; | |
| 42 | addr2 = jp + ((unddel = undap2) - undap1); | |
| 43 | } | |
| 44 | kp = undap1; | |
| 45 | move1(0, unddel); | |
| 46 | dot = kp; | |
| 47 | Command = "move"; | |
| 48 | killed(); | |
| 49 | } else { | |
| 50 | int cnt; | |
| 51 | ||
| 52 | newadot = dot; | |
| 53 | cnt = dol - zero; | |
| 54 | newdol = dol; | |
| 55 | dolp1 = dol + 1; | |
| 56 | /* | |
| 57 | * Command to be undone is a non-move. | |
| 58 | * All such commands are treated as a combination of | |
| 59 | * a delete command and a append command. | |
| 60 | * We first move the lines appended by the last command | |
| 61 | * from undap1 to undap2-1 so that they are just before the | |
| 62 | * saved deleted lines. | |
| 63 | */ | |
| 64 | if ((i = (kp = undap2) - (jp = undap1)) > 0) { | |
| 65 | reverse(jp, kp); | |
| 66 | reverse(kp, dolp1); | |
| 67 | reverse(jp, dolp1); | |
| 68 | /* | |
| 69 | * Account for possible backward motion of target | |
| 70 | * for restoration of saved deleted lines. | |
| 71 | */ | |
| 72 | if (unddel >= jp) | |
| 73 | unddel =- i; | |
| 74 | newdol =- i; | |
| 75 | /* | |
| 76 | * For the case where no lines are restored, dot | |
| 77 | * is the line before the first line deleted. | |
| 78 | */ | |
| 79 | dot = jp-1; | |
| 80 | } | |
| 81 | /* | |
| 82 | * Now put the deleted lines, if any, back where they were. | |
| 83 | * Basic operation is: dol+1,unddol m unddel | |
| 84 | */ | |
| 85 | jp = unddel + 1; | |
| 86 | if ((i = (kp = unddol) - dol) > 0) { | |
| 87 | if (jp != dolp1) { | |
| 88 | reverse(jp, dolp1); | |
| 89 | reverse(dolp1, ++kp); | |
| 90 | reverse(jp, kp); | |
| 91 | } | |
| 92 | /* | |
| 93 | * Account for possible forward motion of the target | |
| 94 | * for restoration of the deleted lines. | |
| 95 | */ | |
| 96 | if (undap1 >= jp) | |
| 97 | undap1 =+ i; | |
| 98 | /* | |
| 99 | * Dot is the first resurrected line. | |
| 100 | */ | |
| 101 | dot = jp; | |
| 102 | newdol =+ i; | |
| 103 | } | |
| 104 | /* | |
| 105 | * Clean up so we are invertible | |
| 106 | */ | |
| 107 | unddel = undap1 - 1; | |
| 108 | undap1 = jp; | |
| 109 | undap2 = jp + i; | |
| 110 | dol = newdol; | |
| 111 | netchHAD(cnt); | |
| 112 | if (undkind == UNDALL) { | |
| 113 | dot = undadot; | |
| 114 | undadot = newadot; | |
| 115 | } | |
| 116 | } | |
| 117 | if (dot == zero && dot != dol) | |
| 118 | dot = one; | |
| 119 | } | |
| 120 | ||
| 121 | somechange() | |
| 122 | { | |
| 123 | register int *ip, *jp; | |
| 124 | ||
| 125 | switch (undkind) { | |
| 126 | case UNDMOVE: | |
| 127 | return; | |
| 128 | case UNDCHANGE: | |
| 129 | if (undap1 == undap2 && dol == unddol) | |
| 130 | break; | |
| 131 | return; | |
| 132 | case UNDALL: | |
| 133 | if (unddol - dol != dol - zero) | |
| 134 | return; | |
| 135 | for (ip = one, jp = dol + 1; ip <= dol; ip++, jp++) | |
| 136 | if ((*ip &~ 01) != (*jp &~ 01)) | |
| 137 | return; | |
| 138 | break; | |
| 139 | case UNDNONE: | |
| 140 | error("Nothing to undo"); | |
| 141 | } | |
| 142 | error("Nothing changed|Last undoable command didn't change anything"); | |
| 143 | } |