[PATCH v2 08/17] virstring: Introduce virStringIsNull()
This function will be used to detect zero buffers (which are
going to be interpreted as hole in virStream later).
I shamelessly took inspiration from coreutils.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
src/libvirt_private.syms | 1 +
src/util/virstring.c | 38 ++++++++++++++++++++++++++++++++
src/util/virstring.h | 2 ++
tests/virstringtest.c | 47 ++++++++++++++++++++++++++++++++++++++++
4 files changed, 88 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index ae0e253ab9..1d80aeb833 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3197,6 +3197,7 @@ virStringHasChars;
virStringHasControlChars;
virStringHasSuffix;
virStringIsEmpty;
+virStringIsNull;
virStringIsPrintable;
virStringListAdd;
virStringListAutoFree;
diff --git a/src/util/virstring.c b/src/util/virstring.c
index e9e792f3bf..c26bc770d4 100644
--- a/src/util/virstring.c
+++ b/src/util/virstring.c
@@ -1404,3 +1404,41 @@ int virStringParseYesNo(const char *str, bool *result)
return 0;
}
+
+
+/**
+ * virStringIsNull:
+ * @buf: buffer to check
+ * @len: the length of the buffer
+ *
+ * For given buffer @buf and its size @len determine whether
+ * it contains only zero bytes (NUL) or not.
+ *
+ * Returns: true if buffer is full of zero bytes,
+ * false otherwise.
+ */
+bool virStringIsNull(const char *buf, size_t len)
+{
+ const char *p = buf;
+
+ if (!len)
+ return true;
+
+ /* Check up to 16 first bytes. */
+ for (;;) {
+ if (*p)
+ return false;
+
+ p++;
+ len--;
+
+ if (!len)
+ return true;
+
+ if ((len & 0xf) == 0)
+ break;
+ }
+
+ /* Now we know first 16 bytes are NUL, memcmp with self. */
+ return memcmp(buf, p, len) == 0;
+}
diff --git a/src/util/virstring.h b/src/util/virstring.h
index 360c68395c..d0e54358ac 100644
--- a/src/util/virstring.h
+++ b/src/util/virstring.h
@@ -185,6 +185,8 @@ int virStringParsePort(const char *str,
int virStringParseYesNo(const char *str,
bool *result)
G_GNUC_WARN_UNUSED_RESULT;
+bool virStringIsNull(const char *buf, size_t len);
+
/**
* VIR_AUTOSTRINGLIST:
*
diff --git a/tests/virstringtest.c b/tests/virstringtest.c
index bee49e6cb6..5838a57574 100644
--- a/tests/virstringtest.c
+++ b/tests/virstringtest.c
@@ -649,6 +649,27 @@ static int testFilterChars(const void *args)
return ret;
}
+struct testIsNulData {
+ const char *buf;
+ size_t len;
+ bool nul;
+};
+
+static int
+testIsNul(const void *args)
+{
+ const struct testIsNulData *data = args;
+ int rc;
+
+ rc = virStringIsNull(data->buf, data->len);
+ if (rc != data->nul) {
+ fprintf(stderr, "Returned %d, expected %d\n", rc, data->nul);
+ return -1;
+ }
+
+ return 0;
+}
+
static int
mymain(void)
{
@@ -977,6 +998,32 @@ mymain(void)
TEST_FILTER_CHARS(NULL, NULL, NULL);
TEST_FILTER_CHARS("hello 123 hello", "helo",
"hellohello");
+#define TEST_IS_NUL(expect, ...) \
+ do { \
+ const char buf[] = {__VA_ARGS__ }; \
+ struct testIsNulData isNulData = { \
+ .buf = buf, \
+ .len = G_N_ELEMENTS(buf), \
+ .nul = expect \
+ }; \
+ if (virTestRun("isNul check", \
+ testIsNul, &isNulData) < 0) \
+ ret = -1; \
+ } while (0)
+
+ TEST_IS_NUL(true);
+ TEST_IS_NUL(true,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
+ TEST_IS_NUL(false, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01);
+ TEST_IS_NUL(false,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01);
+ TEST_IS_NUL(false,
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01,
+ 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01,
+ 0x00);
+
return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}
--
2.26.2