find: fix -prune more. Add big comment about it.

git-svn-id: svn://busybox.net/trunk/busybox@18363 69ca8d6d-28ef-0310-b511-8ec308f3f277

1 files changed, 21 insertions, 7 deletions

diff --git a/findutils/find.c b/findutils/find.c
index 3eea53db0..594eafca4 100644
--- a/findutils/find.c
+++ b/findutils/find.c
@@ -120,20 +120,34 @@ static int exec_actions(action ***appp, const char *fileName, struct stat *statb
 {
         int cur_group;
         int cur_action;
-        int rc = TRUE;
+        int rc = 0;
         action **app, *ap;
 
+        /* "action group" is a set of actions ANDed together.
+         * groups are ORed together.
+         * We simply evaluate each group until we find one in which all actions
+         * succeed. */
+
+        /* -prune is special: if it is encountered, then we won't
+         * descend into current directory. It doesn't matter whether
+         * action group (in which -prune sits) will succeed or not:
+         * find * -prune -name 'f*' -o -name 'm*' -- prunes every dir
+         * find * -name 'f*' -o -prune -name 'm*' -- prunes all dirs
+         *     not starting with 'f' */
+
+        /* We invert TRUE bit (bit 0). Now 1 there means 'failure'.
+         * and bitwise OR in "rc |= TRUE ^ ap->f()" will:
+         * (1) make SKIP (-prune) bit stick; and (2) detect 'failure'.
+         * On return, bit is restored.  */
+
         cur_group = -1;
         while ((app = appp[++cur_group])) {
-                /* We invert TRUE bit (bit 0). Now 1 there means 'failure'.
-                 * and bitwise OR in "rc |= TRUE ^ ap->f()" will:
-                 * (1) make SKIP bit stick; and (2) detect 'failure' */
-                rc = 0; /* 'success' so far */
+                rc &= ~TRUE; /* 'success' so far, clear TRUE bit */
                 cur_action = -1;
                 while (1) {
                         ap = app[++cur_action];
                         if (!ap) /* all actions in group were successful */
-                                return rc ^ TRUE;
+                                return rc ^ TRUE; /* restore TRUE bit */
                         rc |= TRUE ^ ap->f(fileName, statbuf, ap);
 #if ENABLE_FEATURE_FIND_NOT
                         if (ap->invert) rc ^= TRUE;
@@ -142,7 +156,7 @@ static int exec_actions(action ***appp, const char *fileName, struct stat *statb
                                 break;
                 }
         }
-        return rc ^ TRUE; /* straighten things out */
+        return rc ^ TRUE; /* restore TRUE bit */
 }