From 7c55ca5fff01fa28b99a0717860848071fca80ce Mon Sep 17 00:00:00 2001 From: Ori Bernstein Date: Wed, 4 Dec 2019 12:55:03 -0800 Subject: acme: Apply each -/+ only once (#156) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When plumbing an address like `3-`, Acme selects line 1, and similarly `3+` selects line 5. The same problem can be observed for character addresses (`#123+`) but _not_ for ones like `+`, `.+` or `/foo/+`: The problem only occurs when a number is followed by a direction (`-`/`+`). Following along with the example `3-` through `address` (in addr.c): We read `3` into `c` and match the `case` on line 239. The `while` loop on line 242ff reads additional digits into `c` and puts the first non-digit back by decrementing the index `q`. Then we find the range for line 3 on line 251 and continue. On the next iteration, we set `prevc` to the last `c`, but since that part read ahead _into `c`_, `c` is currently the _next_ character we will read, `-`, and now `prevc` is too. Then in the case block (line 210) the condition on line 211 holds and Acme believes that it has read two `-` in sequence and modifies the range to account for the “first” `-`. The “second” `-` gets applied after the loop is done, on line 292. So the general problem is: While reading numbers, Acme reads the next character after the number into `c`. It decrements the counter to ensure it will read it again on the next iteration, but it still uses it to update `prevc`. This change solves the problem by reading digits into `nc` instead. This variable is used to similar effect in the block for directions (line 212) and fills the role of “local `c` that we can safely use to read ahead” nicely. (imported from plan9front a82a8b6368274d77d42f526e379b74e79c137e26) --- sys/src/cmd/acme/addr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/sys/src/cmd/acme/addr.c b/sys/src/cmd/acme/addr.c index 29c9c1cfc..94dd88cde 100644 --- a/sys/src/cmd/acme/addr.c +++ b/sys/src/cmd/acme/addr.c @@ -215,12 +215,12 @@ address(Mntdir *md, Text *t, Range lim, Range ar, void *a, uint q0, uint q1, int case '5': case '6': case '7': case '8': case '9': n = c -'0'; while(q