sd-bus: add sd_bus_path_{encode,decode}_many()

This introduces two new helpers alongside sd_bus_path_{encode,decode}(),
which work similarly to their counterparts, but accept a format-string as
input. This allows encoding and decoding multiple labels of a format
string at the same time.

4 files changed, 200 insertions, 0 deletions

diff --git a/src/libsystemd/libsystemd.sym b/src/libsystemd/libsystemd.sym
index 518cbbb7ed..843a1e9880 100644
--- a/src/libsystemd/libsystemd.sym
+++ b/src/libsystemd/libsystemd.sym
@@ -477,4 +477,6 @@ global:
 LIBSYSTEMD_227 {
 global:
         sd_bus_default_flush_close;
+        sd_bus_path_decode_many;
+        sd_bus_path_encode_many;
 } LIBSYSTEMD_226;
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 53d1c6f61d..3310d3859d 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -3454,6 +3454,171 @@ _public_ int sd_bus_path_decode(const char *path, const char *prefix, char **ext
         return 1;
 }
 
+_public_ int sd_bus_path_encode_many(char **out, const char *path_template, ...) {
+        _cleanup_strv_free_ char **labels = NULL;
+        char *path, *path_pos, **label_pos;
+        const char *sep, *template_pos;
+        size_t path_length;
+        va_list list;
+        int r;
+
+        assert_return(out, -EINVAL);
+        assert_return(path_template, -EINVAL);
+
+        path_length = strlen(path_template);
+
+        va_start(list, out);
+        for (sep = strchr(path_template, '%'); sep; sep = strchr(sep + 1, '%')) {
+                const char *arg;
+                char *label;
+
+                arg = va_arg(list, const char *);
+                if (!arg) {
+                        va_end(list);
+                        return -EINVAL;
+                }
+
+                label = bus_label_escape(arg);
+                if (!label) {
+                        va_end(list);
+                        return -ENOMEM;
+                }
+
+                r = strv_consume(&labels, label);
+                if (r < 0) {
+                        va_end(list);
+                        return r;
+                }
+
+                /* add label length, but account for the format character */
+                path_length += strlen(label) - 1;
+        }
+        va_end(list);
+
+        path = malloc(path_length + 1);
+        if (!path)
+                return -ENOMEM;
+
+        path_pos = path;
+        label_pos = labels;
+
+        for (template_pos = path_template; *template_pos; ) {
+                sep = strchrnul(template_pos, '%');
+                path_pos = mempcpy(path_pos, template_pos, sep - template_pos);
+                if (!*sep)
+                        break;
+
+                path_pos = stpcpy(path_pos, *label_pos++);
+                template_pos = sep + 1;
+        }
+
+        *path_pos = 0;
+        *out = path;
+        return 0;
+}
+
+_public_ int sd_bus_path_decode_many(const char *path, const char *path_template, ...) {
+        _cleanup_strv_free_ char **labels = NULL;
+        const char *template_pos, *path_pos;
+        char **label_pos;
+        va_list list;
+        int r;
+
+        /*
+         * This decodes an object-path based on a template argument. The
+         * template consists of a verbatim path, optionally including special
+         * directives:
+         *
+         *   - Each occurrence of '%' in the template matches an arbitrary
+         *     substring of a label in the given path. At most one such
+         *     directive is allowed per label. For each such directive, the
+         *     caller must provide an output parameter (char **) via va_arg. If
+         *     NULL is passed, the given label is verified, but not returned.
+         *     For each matched label, the *decoded* label is stored in the
+         *     passed output argument, and the caller is responsible to free
+         *     it. Note that the output arguments are only modified if the
+         *     actualy path matched the template. Otherwise, they're left
+         *     untouched.
+         *
+         * This function returns <0 on error, 0 if the path does not match the
+         * template, 1 if it matched.
+         */
+
+        assert_return(path, -EINVAL);
+        assert_return(path_template, -EINVAL);
+
+        path_pos = path;
+
+        for (template_pos = path_template; *template_pos; ) {
+                const char *sep;
+                size_t length;
+                char *label;
+
+                /* verify everything until the next '%' matches verbatim */
+                sep = strchrnul(template_pos, '%');
+                length = sep - template_pos;
+                if (strncmp(path_pos, template_pos, length))
+                        return 0;
+
+                path_pos += length;
+                template_pos += length;
+
+                if (!*template_pos)
+                        break;
+
+                /* We found the next '%' character. Everything up until here
+                 * matched. We now skip ahead to the end of this label and make
+                 * sure it matches the tail of the label in the path. Then we
+                 * decode the string in-between and save it for later use. */
+
+                ++template_pos; /* skip over '%' */
+
+                sep = strchrnul(template_pos, '/');
+                length = sep - template_pos; /* length of suffix to match verbatim */
+
+                /* verify the suffixes match */
+                sep = strchrnul(path_pos, '/');
+                if (sep - path_pos < (ssize_t)length ||
+                    strncmp(sep - length, template_pos, length))
+                        return 0;
+
+                template_pos += length; /* skip over matched label */
+                length = sep - path_pos - length; /* length of sub-label to decode */
+
+                /* store unescaped label for later use */
+                label = bus_label_unescape_n(path_pos, length);
+                if (!label)
+                        return -ENOMEM;
+
+                r = strv_consume(&labels, label);
+                if (r < 0)
+                        return r;
+
+                path_pos = sep; /* skip decoded label and suffix */
+        }
+
+        /* end of template must match end of path */
+        if (*path_pos)
+                return 0;
+
+        /* copy the labels over to the caller */
+        va_start(list, path);
+        for (label_pos = labels; label_pos && *label_pos; ++label_pos) {
+                char **arg;
+
+                arg = va_arg(list, char **);
+                if (arg)
+                        *arg = *label_pos;
+                else
+                        free(*label_pos);
+        }
+        va_end(list);
+
+        free(labels);
+        labels = NULL;
+        return 1;
+}
+
 _public_ int sd_bus_try_close(sd_bus *bus) {
         int r;
 
diff --git a/src/libsystemd/sd-bus/test-bus-marshal.c b/src/libsystemd/sd-bus/test-bus-marshal.c
index b203707f27..ff6bba5988 100644
--- a/src/libsystemd/sd-bus/test-bus-marshal.c
+++ b/src/libsystemd/sd-bus/test-bus-marshal.c
@@ -66,6 +66,36 @@ static void test_bus_path_encode(void) {
         assert_se(sd_bus_path_decode(e, "/foo/bar", &f) > 0 && streq(f, "foo.bar"));
 }
 
+static void test_bus_path_encode_many(void) {
+        _cleanup_free_ char *a = NULL, *b = NULL, *c = NULL, *d = NULL, *e = NULL, *f = NULL;
+
+        assert_se(sd_bus_path_decode_many("/foo/bar", "/prefix/%", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/prefix/bar", "/prefix/%bar", NULL) == 1);
+        assert_se(sd_bus_path_decode_many("/foo/bar", "/prefix/%/suffix", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/prefix/foobar/suffix", "/prefix/%/suffix", &a) == 1 && streq_ptr(a, "foobar"));
+        assert_se(sd_bus_path_decode_many("/prefix/one_foo_two/mid/three_bar_four/suffix", "/prefix/one_%_two/mid/three_%_four/suffix", &b, &c) == 1 && streq_ptr(b, "foo") && streq_ptr(c, "bar"));
+        assert_se(sd_bus_path_decode_many("/prefix/one_foo_two/mid/three_bar_four/suffix", "/prefix/one_%_two/mid/three_%_four/suffix", NULL, &d) == 1 && streq_ptr(d, "bar"));
+
+        assert_se(sd_bus_path_decode_many("/foo/bar", "/foo/bar/%", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/bar%", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%/bar", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%bar", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/bar/suffix") == 1);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%%/suffix", NULL, NULL) == 0); /* multiple '%' are treated verbatim */
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%/suffi", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%/suffix", &e) == 1 && streq_ptr(e, "bar"));
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/foo/%/%", NULL, NULL) == 1);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/%/%/%", NULL, NULL, NULL) == 1);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "%/%/%", NULL, NULL, NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/%/%", NULL, NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/%/%/", NULL, NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/%/", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "/%", NULL) == 0);
+        assert_se(sd_bus_path_decode_many("/foo/bar/suffix", "%", NULL) == 0);
+
+        assert_se(sd_bus_path_encode_many(&f, "/prefix/one_%_two/mid/three_%_four/suffix", "foo", "bar") >= 0 && streq_ptr(f, "/prefix/one_foo_two/mid/three_bar_four/suffix"));
+}
+
 static void test_bus_label_escape_one(const char *a, const char *b) {
         _cleanup_free_ char *t = NULL, *x = NULL, *y = NULL;
 
@@ -393,6 +423,7 @@ int main(int argc, char *argv[]) {
         test_bus_label_escape();
         test_bus_path_encode();
         test_bus_path_encode_unique();
+        test_bus_path_encode_many();
 
         return 0;
 }
diff --git a/src/systemd/sd-bus.h b/src/systemd/sd-bus.h
index 0883203ae7..43cf247cdf 100644
--- a/src/systemd/sd-bus.h
+++ b/src/systemd/sd-bus.h
@@ -420,7 +420,9 @@ int sd_bus_error_add_map(const sd_bus_error_map *map);
 /* Label escaping */
 
 int sd_bus_path_encode(const char *prefix, const char *external_id, char **ret_path);
+int sd_bus_path_encode_many(char **out, const char *path_template, ...);
 int sd_bus_path_decode(const char *path, const char *prefix, char **ret_external_id);
+int sd_bus_path_decode_many(const char *path, const char *path_template, ...);
 
 /* Tracking peers */