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Bugfix: Off-by-one bug in subtracting UINT. Fixes #1557

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rjo12
2023-05-11 22:49:23 +09:30
committed by Dennis Guse
parent d6cf8ba90e
commit 5b0e7e5065
2 changed files with 36 additions and 6 deletions
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src/androidTest/java/de/dennisguse/opentracks/sensors/UintUtilsTest.java
+34 -5
View File
@@ -11,15 +11,44 @@ public class UintUtilsTest {
assertEquals(0, UintUtils.diff(1, 1, UintUtils.UINT16_MAX));
assertEquals(1, UintUtils.diff(2, 1, UintUtils.UINT16_MAX));
assertEquals(3, UintUtils.diff(5, 2, UintUtils.UINT16_MAX));
assertEquals(65534, UintUtils.diff(1, 2, UintUtils.UINT16_MAX));
// assertEquals(65535, UintUtils.diff(0, 1, UintUtils.UINT16_MAX));
assertEquals(65535, UintUtils.UINT16_MAX);
assertEquals(65535, UintUtils.diff(1, 2, UintUtils.UINT16_MAX)); /* unsigned 16 arithmetic is modulo UINT16_MAX + 1, not modulo UINT16_MAX */
assertEquals(65530, UintUtils.diff(UintUtils.UINT16_MAX, 5, UintUtils.UINT16_MAX));
/* Test modulo arithmetic for arguments that are out of range */
if (false) { /* false means UintUtils.diff() throws if arguments out of range */
assertEquals(0, UintUtils.diff(65537, 1, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(1, 65537, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(65537, 65537, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(-65535, 1, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(1, -65535, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(-65535, -65535, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(-65535, 65537, UintUtils.UINT16_MAX));
assertEquals(0, UintUtils.diff(65537, -65535, UintUtils.UINT16_MAX));
}
/* The following tests are the above, but for 32-bit unsigned. */
assertEquals(0, UintUtils.diff(1, 1, UintUtils.UINT32_MAX));
assertEquals(1, UintUtils.diff(2, 1, UintUtils.UINT32_MAX));
assertEquals(3, UintUtils.diff(5, 2, UintUtils.UINT32_MAX));
assertEquals(4294967295L, UintUtils.diff(1, 2, UintUtils.UINT32_MAX));
assertEquals(4294967290L, UintUtils.diff(UintUtils.UINT32_MAX, 5, UintUtils.UINT32_MAX));
if (false) { /* false means UintUtils.diff() throws if arguments out of range */
assertEquals(0, UintUtils.diff(4294967297L, 1, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(1, 4294967297L, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(4294967297L, 4294967297L, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(-4294967295L, 1, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(1, -4294967295L, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(-4294967295L, -4294967295L, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(-4294967295L, 4294967297L, UintUtils.UINT32_MAX));
assertEquals(0, UintUtils.diff(65537, -4294967297L, UintUtils.UINT32_MAX));
}
}
@Test
public void realData() {
assertEquals(1, UintUtils.diff(381616, 381615, UintUtils.UINT32_MAX));
}
}
}
src/main/java/de/dennisguse/opentracks/sensors/UintUtils.java
+2 -1
View File
@@ -14,6 +14,7 @@ public class UintUtils {
* @return diff
*/
public static long diff(long a, long b, final long UINT_MAX) {
if (a < 0 || b < 0) {
throw new RuntimeException("a or b cannot be less than zero.");
}
@@ -25,6 +26,6 @@ public class UintUtils {
return a - b;
}
return (UINT_MAX - b) + a;
return (UINT_MAX + 1 - b) + a;
}
}