virbitmap: Introduce virBitmapParseUnlimitedAllowEmpty()

Some sysfs files contain either string representation of a bitmap
or just a newline character. An example of such file is:
/sys/devices/system/cpu/isolated. Our current implementation of
virBitmapParseUnlimited() fails in the latter case,
unfortunately. Introduce a slightly modified version that accepts
empty files.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>

src/libvirt_private.syms

@@ -1936,6 +1936,7 @@ virBitmapNextSetBit;
 virBitmapOverlaps;
 virBitmapParse;
 virBitmapParseUnlimited;
+virBitmapParseUnlimitedAllowEmpty;
 virBitmapSetAll;
 virBitmapSetBit;
 virBitmapSetBitExpand;

src/util/virbitmap.c

@@ -368,6 +368,7 @@ virBitmapFormat(virBitmap *bitmap)
  * @str: points to a string representing a human-readable bitmap
  * @bitmap: a bitmap populated from @str
  * @limited: Don't use self-expanding APIs, report error if bit exceeds bitmap size
+ * @allowEmpty: Allow @str to be empty string or contain nothing but spaces
  *
  * This function is the counterpart of virBitmapFormat. This function creates
  * a bitmap, in which bits are set according to the content of @str.
@@ -381,7 +382,8 @@ virBitmapFormat(virBitmap *bitmap)
 static int
 virBitmapParseInternal(const char *str,
                        virBitmap *bitmap,
-                       bool limited)
+                       bool limited,
+                       bool allowEmpty)
 {
     bool neg = false;
     const char *cur = str;
@@ -389,13 +391,19 @@ virBitmapParseInternal(const char *str,
     size_t i;
     int start, last;
 
-    if (!str)
+    if (!str) {
+        if (allowEmpty)
+            return 0;
         goto error;
+    }
 
     virSkipSpaces(&cur);
 
-    if (*cur == '\0')
+    if (*cur == '\0') {
+        if (allowEmpty)
+            return 0;
         goto error;
+    }
 
     while (*cur != 0) {
         /*
@@ -505,7 +513,7 @@ virBitmapParse(const char *str,
 {
     g_autoptr(virBitmap) tmp = virBitmapNew(bitmapSize);
 
-    if (virBitmapParseInternal(str, tmp, true) < 0)
+    if (virBitmapParseInternal(str, tmp, true, false) < 0)
         return -1;
 
     *bitmap = g_steal_pointer(&tmp);
@@ -534,7 +542,29 @@ virBitmapParseUnlimited(const char *str)
 {
     g_autoptr(virBitmap) tmp = virBitmapNew(0);
 
-    if (virBitmapParseInternal(str, tmp, false) < 0)
+    if (virBitmapParseInternal(str, tmp, false, false) < 0)
+        return NULL;
+
+    return g_steal_pointer(&tmp);
+}
+
+
+/**
+ * virBitmapParseUnlimitedAllowEmpty:
+ * @str: points to a string representing a human-readable bitmap
+ *
+ * Just like virBitmapParseUnlimited() except when the input string @str is
+ * empty (or contains just spaces) an empty bitmap is returned instead of an
+ * error.
+ *
+ * Returns @bitmap on success, or NULL in cas of error
+ */
+virBitmap *
+virBitmapParseUnlimitedAllowEmpty(const char *str)
+{
+    g_autoptr(virBitmap) tmp = virBitmapNew(0);
+
+    if (virBitmapParseInternal(str, tmp, false, true) < 0)
         return NULL;
 
     return g_steal_pointer(&tmp);

src/util/virbitmap.h

@@ -84,6 +84,9 @@ int virBitmapParse(const char *str,
 virBitmap *
 virBitmapParseUnlimited(const char *str);
 
+virBitmap *
+virBitmapParseUnlimitedAllowEmpty(const char *str);
+
 virBitmap *virBitmapNewCopy(virBitmap *src) ATTRIBUTE_NONNULL(1);
 
 virBitmap *virBitmapNewData(const void *data, int len) ATTRIBUTE_NONNULL(1);

tests/virbitmaptest.c

@@ -705,6 +705,43 @@ test16(const void *opaque G_GNUC_UNUSED)
 }
 
 
+/* virBitmapParseUnlimitedAllowEmpty */
+static int
+test17(const void *opaque G_GNUC_UNUSED)
+{
+    g_autoptr(virBitmap) map1 = NULL;
+    g_autoptr(virBitmap) map2 = NULL;
+    g_autofree char *map1_str = NULL;
+    g_autofree char *map2_str = NULL;
+
+    if (!(map1 = virBitmapParseUnlimitedAllowEmpty(NULL))) {
+        fprintf(stderr, "Expected success, got failure\n");
+        return -1;
+    }
+
+    if (!(map2 = virBitmapParseUnlimitedAllowEmpty("    "))) {
+        fprintf(stderr, "Expected success, got failure\n");
+        return -1;
+    }
+
+    if (!virBitmapIsAllClear(map1) ||
+        !virBitmapIsAllClear(map2) ||
+        !virBitmapEqual(map1, map2)) {
+        fprintf(stderr, "empty maps should equal\n");
+        return -1;
+    }
+
+    if (!(map1_str = virBitmapFormat(map1)) ||
+        !(map2_str = virBitmapFormat(map2)) ||
+        STRNEQ(map1_str, map2_str)) {
+        fprintf(stderr, "maps don't equal after format to string\n");
+        return -1;
+    }
+
+    return 0;
+}
+
+
 #define TESTBINARYOP(A, B, RES, FUNC) \
     testBinaryOpData.a = A; \
     testBinaryOpData.b = B; \
@@ -781,6 +818,9 @@ mymain(void)
     if (virTestRun("test16", test16, NULL) < 0)
         ret = -1;
 
+    if (virTestRun("test17", test17, NULL) < 0)
+        ret = -1;
+
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }