Add virStringFilterChars() string utility

Add a function to filter a string based on a list of valid characters.

src/libvirt_private.syms

@@ -2755,6 +2755,7 @@ virStrcpy;
 virStrdup;
 virStringBufferIsPrintable;
 virStringEncodeBase64;
+virStringFilterChars;
 virStringHasChars;
 virStringHasControlChars;
 virStringIsEmpty;

src/util/virstring.c

@@ -1293,6 +1293,30 @@ virStringStripControlChars(char *str)
     str[j] = '\0';
 }
 
+/**
+ * virStringFilterChars:
+ * @str: the string to strip
+ * @valid: the valid characters for the string
+ *
+ * Modify the string in-place to remove the characters that aren't
+ * in the list of valid ones.
+ */
+void
+virStringFilterChars(char *str, const char *valid)
+{
+    size_t len, i, j;
+
+    if (!str)
+        return;
+
+    len = strlen(str);
+    for (i = 0, j = 0; i < len; i++) {
+        if (strchr(valid, str[i]))
+            str[j++] = str[i];
+    }
+    str[j] = '\0';
+}
+
 /**
  * virStringToUpper:
  * @str: string to capitalize

src/util/virstring.h

@@ -293,6 +293,7 @@ bool virStringHasChars(const char *str,
                        const char *chars);
 bool virStringHasControlChars(const char *str);
 void virStringStripControlChars(char *str);
+void virStringFilterChars(char *str, const char *valid);
 
 bool virStringIsPrintable(const char *str);
 bool virStringBufferIsPrintable(const uint8_t *buf, size_t buflen);

tests/virstringtest.c

@@ -767,6 +767,36 @@ static int testStripControlChars(const void *args)
     return ret;
 }
 
+struct testFilterData {
+    const char *string;
+    const char *valid;
+    const char *result;
+};
+
+static int testFilterChars(const void *args)
+{
+    const struct testFilterData *data = args;
+    int ret = -1;
+    char *res = NULL;
+
+    if (VIR_STRDUP(res, data->string) < 0)
+        goto cleanup;
+
+    virStringFilterChars(res, data->valid);
+
+    if (STRNEQ_NULLABLE(res, data->result)) {
+        fprintf(stderr, "Returned '%s', expected '%s'\n",
+                NULLSTR(res), NULLSTR(data->result));
+        goto cleanup;
+    }
+
+    ret = 0;
+
+ cleanup:
+    VIR_FREE(res);
+    return ret;
+}
+
 static int
 mymain(void)
 {
@@ -1085,6 +1115,22 @@ mymain(void)
     TEST_STRIP_CONTROL_CHARS("\x01H\x02" "E\x03L\x04L\x05O", "HELLO");
     TEST_STRIP_CONTROL_CHARS("\x01\x02\x03\x04HELL\x05O", "HELLO");
     TEST_STRIP_CONTROL_CHARS("\nhello \x01\x07hello\t", "\nhello hello\t");
+
+#define TEST_FILTER_CHARS(str, filter, res) \
+    do { \
+        struct testFilterData filterData = { \
+            .string = str,  \
+            .valid = filter, \
+            .result = res,  \
+        }; \
+        if (virTestRun("Filter chars from " #str, \
+                       testFilterChars, &filterData) < 0) \
+            ret = -1; \
+    } while (0)
+
+    TEST_FILTER_CHARS(NULL, NULL, NULL);
+    TEST_FILTER_CHARS("hello 123 hello", "helo", "hellohello");
+
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }