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[PATCH v3, 07/16] xfsprogs: metadump: use pointers in generate_obfuscate

To: xfs@xxxxxxxxxxx
Subject: [PATCH v3, 07/16] xfsprogs: metadump: use pointers in generate_obfuscated_name()
From: Alex Elder <aelder@xxxxxxx>
Date: Fri, 18 Feb 2011 15:21:01 -0600
User-agent: Heirloom mailx 12.5 7/5/10
Switch from using array references to using pointers to refer to the
pathname characters as they get generated.  Also limit the scope of
a few automatic variables.

Signed-off-by: Alex Elder <aelder@xxxxxxx>

The only update since the last post version is the addition of an
ASSERT() in the loop generating the last 5 bytes.

---
 db/metadump.c |   35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

Index: b/db/metadump.c
===================================================================
--- a/db/metadump.c
+++ b/db/metadump.c
@@ -437,11 +437,8 @@ generate_obfuscated_name(
 {
        xfs_dahash_t            hash;
        name_ent_t              *p;
-       int                     i;
        int                     dup;
-       xfs_dahash_t            newhash;
        uchar_t                 newname[NAME_MAX];
-       uchar_t                 *newp = &newname[0];
 
        /*
         * Our obfuscation algorithm requires at least 5-character
@@ -472,7 +469,12 @@ generate_obfuscated_name(
 
        hash = libxfs_da_hashname(name, namelen);
        do {
-               uchar_t high_bit;
+               int             i;
+               xfs_dahash_t    newhash = 0;
+               uchar_t         *newp = &newname[0];
+               uchar_t         *first;
+               uchar_t         high_bit;
+               int             shift;
 
                dup = 0;
 
@@ -482,10 +484,10 @@ generate_obfuscated_name(
                 * characters.  Accumulate its new hash value as we
                 * go.
                 */
-               newhash = 0;
                for (i = 0; i < namelen - 5; i++) {
-                       newp[i] = random_filename_char();
-                       newhash = newp[i] ^ rol32(newhash, 7);
+                       *newp = random_filename_char();
+                       newhash = *newp ^ rol32(newhash, 7);
+                       newp++;
                }
 
                /*
@@ -500,16 +502,17 @@ generate_obfuscated_name(
                 */
                newhash = rol32(newhash, 3) ^ hash;
 
+               first = newp;
                high_bit = 0;
-               for (i = 5; i > 0; i--) {
-                       int shift = (i - 1) * 7;
-
-                       newp[namelen - i] = ((newhash >> shift) & 0x7f) ^ 
high_bit;
-                       if (is_invalid_char(newp[namelen - i])) {
-                               newp[namelen - i] ^= 1;
+               for (shift = 28; shift >= 0; shift -= 7) {
+                       *newp = (newhash >> shift & 0x7f) ^ high_bit;
+                       if (is_invalid_char(*newp)) {
+                               *newp ^= 1;
                                high_bit = 0x80;
                        } else
                                high_bit = 0;
+                       ASSERT(!is_invalid_char(*newp));
+                       newp++;
                }
 
                /*
@@ -522,15 +525,15 @@ generate_obfuscated_name(
                 * worry about it becoming invalid as a result.
                 */
                if (high_bit) {
-                       newp[namelen - 5] ^= 0x10;
-                       ASSERT(!is_invalid_char(newp[namelen - 5]));
+                       *first ^= 0x10;
+                       ASSERT(!is_invalid_char(*first));
                }
 
                ASSERT(libxfs_da_hashname(newname, namelen) == hash);
 
                for (p = nametable[hash % NAME_TABLE_SIZE]; p; p = p->next) {
                        if (p->hash == hash && p->namelen == namelen &&
-                                       memcmp(p->name, newname, namelen) == 0){
+                                       !memcmp(p->name, newname, namelen)) {
                                dup = 1;
                                break;
                        }

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