Changeset 4fd61ba in mainline

Timestamp:

2006-04-30T19:08:14Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

ea199e5

Parents:

0e00b8a

Message:

Fix a bug caused by an unsigned subtraction of bigger value from smaller value in bitmap implementation.
Fix wrong calculation of unaligned leading bits in bitmap implementation.

File:

• generic/src/adt/bitmap.c (modified) (7 diffs)

generic/src/adt/bitmap.c

@@ -40 +40 @@
 #include <align.h>
 #include <debug.h>
+#include <macros.h>
 
 #define ALL_ONES        0xff
@@ -69 +70 @@
         index_t aligned_start;
         count_t lub;            /* leading unaligned bits */
-        count_t tub;            /* trailing unaligned bits */
+        count_t amb;            /* aligned middle bits */
+        count_t tab;            /* trailing aligned bits */
         
         ASSERT(start + bits <= bitmap->bits);
         
         aligned_start = ALIGN_UP(start, 8);
-        lub = aligned_start - start;
-        tub = (bits - lub) % 8;
+        lub = min(aligned_start - start, bits);
+        amb = bits > lub ? bits - lub : 0;
+        tab = amb % 8;
         
         if (lub) {
@@ -83 +86 @@
                 bitmap->map[start / 8] |= ~((1 << (8 - lub)) - 1);
         }
-        for (i = 0; i < (bits - lub) / 8; i++) {
+        for (i = 0; i < amb / 8; i++) {
                 /*
                  * The middle bits can be set byte by byte.
@@ -89 +92 @@
                 bitmap->map[aligned_start / 8 + i] = ALL_ONES;
         }
-        if (tub) {
+        if (tab) {
                 /*
-                 * Make sure to set any trailing unaligned bits.
+                 * Make sure to set any trailing aligned bits.
                  */
-                bitmap->map[aligned_start / 8 + i] |= (1 << tub) - 1;
+                bitmap->map[aligned_start / 8 + i] |= (1 << tab) - 1;
         }
         
@@ -109 +112 @@
         index_t aligned_start;
         count_t lub;            /* leading unaligned bits */
-        count_t tub;            /* trailing unaligned bits */
+        count_t amb;            /* aligned middle bits */
+        count_t tab;            /* trailing aligned bits */
         
         ASSERT(start + bits <= bitmap->bits);
         
         aligned_start = ALIGN_UP(start, 8);
-        lub = aligned_start - start;
-        tub = (bits - lub) % 8;
-        
+        lub = min(aligned_start - start, bits);
+        amb = bits > lub ? bits - lub : 0;
+        tab = amb % 8;
+
         if (lub) {
                 /*
@@ -123 +128 @@
                 bitmap->map[start / 8] &= (1 << (8 - lub)) - 1;
         }
-        for (i = 0; i < (bits - lub) / 8; i++) {
+        for (i = 0; i < amb / 8; i++) {
                 /*
                  * The middle bits can be cleared byte by byte.
@@ -129 +134 @@
                 bitmap->map[aligned_start / 8 + i] = ALL_ZEROES;
         }
-        if (tub) {
+        if (tab) {
                 /*
-                 * Make sure to clear any trailing unaligned bits.
+                 * Make sure to clear any trailing aligned bits.
                  */
-                bitmap->map[aligned_start / 8 + i] &= ~((1 << tub) - 1);
+                bitmap->map[aligned_start / 8 + i] &= ~((1 << tab) - 1);
         }
-        
+
 }