Merge pull request #9131 from poettering/memory-startswith

add new memory_startswith() helper and make use of it everywhere

src/basic/log.c

@@ -1037,13 +1037,9 @@ int log_struct_iovec_internal(
                         return -error;
         }
 
-        for (i = 0; i < n_input_iovec; i++) {
-                if (input_iovec[i].iov_len < STRLEN("MESSAGE="))
-                        continue;
-
-                if (memcmp(input_iovec[i].iov_base, "MESSAGE=", STRLEN("MESSAGE=")) == 0)
+        for (i = 0; i < n_input_iovec; i++)
+                if (memory_startswith(input_iovec[i].iov_base, input_iovec[i].iov_len, "MESSAGE="))
                         break;
-        }
 
         if (_unlikely_(i >= n_input_iovec)) /* Couldn't find MESSAGE=? */
                 return -error;

src/basic/string-util.h

@@ -209,3 +209,21 @@ static inline size_t strlen_ptr(const char *s) {
 
         return strlen(s);
 }
+
+/* Like startswith(), but operates on arbitrary memory blocks */
+static inline void *memory_startswith(const void *p, size_t sz, const char *token) {
+        size_t n;
+
+        assert(token);
+
+        n = strlen(token);
+        if (sz < n)
+                return NULL;
+
+        assert(p);
+
+        if (memcmp(p, token, n) != 0)
+                return NULL;
+
+        return (uint8_t*) p + n;
+}

src/coredump/coredump.c

@@ -852,21 +852,18 @@ static void map_context_fields(const struct iovec *iovec, const char* context[])
         assert(context);
 
         for (i = 0; i < ELEMENTSOF(context_field_names); i++) {
-                size_t l;
+                char *p;
 
                 if (!context_field_names[i])
                         continue;
 
-                l = strlen(context_field_names[i]);
-                if (iovec->iov_len < l)
-                        continue;
-
-                if (memcmp(iovec->iov_base, context_field_names[i], l) != 0)
+                p = memory_startswith(iovec->iov_base, iovec->iov_len, context_field_names[i]);
+                if (!p)
                         continue;
 
                 /* Note that these strings are NUL terminated, because we made sure that a trailing NUL byte is in the
                  * buffer, though not included in the iov_len count. (see below) */
-                context[i] = (char*) iovec->iov_base + l;
+                context[i] = p;
                 break;
         }
 }

src/import/curl-util.c

@@ -365,19 +365,14 @@ struct curl_slist *curl_slist_new(const char *first, ...) {
 }
 
 int curl_header_strdup(const void *contents, size_t sz, const char *field, char **value) {
-        const char *p = contents;
-        size_t l;
+        const char *p;
         char *s;
 
-        l = strlen(field);
-        if (sz < l)
+        p = memory_startswith(contents, sz, field);
+        if (!p)
                 return 0;
 
-        if (memcmp(p, field, l) != 0)
-                return 0;
-
-        p += l;
-        sz -= l;
+        sz -= p - (const char*) contents;
 
         if (memchr(p, 0, sz))
                 return 0;

src/libsystemd/sd-bus/bus-socket.c

@@ -248,16 +248,13 @@ static bool line_equals(const char *s, size_t m, const char *line) {
 }
 
 static bool line_begins(const char *s, size_t m, const char *word) {
-        size_t l;
+        const char *p;
 
-        l = strlen(word);
-        if (m < l)
+        p = memory_startswith(s, m, word);
+        if (!p)
                 return false;
 
-        if (memcmp(s, word, l) != 0)
-                return false;
-
-        return m == l || (m > l && s[l] == ' ');
+        return IN_SET(*p, 0, ' ');
 }
 
 static int verify_anonymous_token(sd_bus *b, const char *p, size_t l) {

src/shared/dns-domain.c

@@ -353,10 +353,7 @@ int dns_label_undo_idna(const char *encoded, size_t encoded_size, char *decoded,
         if (encoded_size <= 0 || encoded_size > DNS_LABEL_MAX)
                 return -EINVAL;
 
-        if (encoded_size < sizeof(IDNA_ACE_PREFIX)-1)
-                return 0;
-
-        if (memcmp(encoded, IDNA_ACE_PREFIX, sizeof(IDNA_ACE_PREFIX) -1) != 0)
+        if (!memory_startswith(encoded, encoded_size, IDNA_ACE_PREFIX))
                 return 0;
 
         input = stringprep_utf8_to_ucs4(encoded, encoded_size, &input_size);

src/shared/logs-show.c

@@ -832,8 +832,7 @@ static int output_json(
                 char *n;
                 unsigned u;
 
-                if (length >= 9 &&
-                    memcmp(data, "_BOOT_ID=", 9) == 0)
+                if (memory_startswith(data, length, "_BOOT_ID="))
                         continue;
 
                 eq = memchr(data, '=', length);
@@ -882,10 +881,8 @@ static int output_json(
                         size_t m;
                         unsigned u;
 
-                        /* We already printed the boot id, from the data in
-                         * the header, hence let's suppress it here */
-                        if (length >= 9 &&
-                            memcmp(data, "_BOOT_ID=", 9) == 0)
+                        /* We already printed the boot id, from the data in the header, hence let's suppress it here */
+                        if (memory_startswith(data, length, "_BOOT_ID="))
                                 continue;
 
                         eq = memchr(data, '=', length);

src/test/test-string-util.c

@@ -406,6 +406,18 @@ static void test_strlen_ptr(void) {
         assert_se(strlen_ptr(NULL) == 0);
 }
 
+static void test_memory_startswith(void) {
+        assert_se(streq(memory_startswith("", 0, ""), ""));
+        assert_se(streq(memory_startswith("", 1, ""), ""));
+        assert_se(streq(memory_startswith("x", 2, ""), "x"));
+        assert_se(!memory_startswith("", 1, "x"));
+        assert_se(!memory_startswith("", 1, "xxxxxxxx"));
+        assert_se(streq(memory_startswith("xxx", 4, "x"), "xx"));
+        assert_se(streq(memory_startswith("xxx", 4, "xx"), "x"));
+        assert_se(streq(memory_startswith("xxx", 4, "xxx"), ""));
+        assert_se(!memory_startswith("xxx", 4, "xxxx"));
+}
+
 int main(int argc, char *argv[]) {
         test_string_erase();
         test_ascii_strcasecmp_n();
@@ -433,6 +445,7 @@ int main(int argc, char *argv[]) {
         test_split_pair();
         test_first_word();
         test_strlen_ptr();
+        test_memory_startswith();
 
         return 0;
 }