Fix relative URI creation

8 files changed, 58 insertions, 43 deletions

diff --git a/NEWS b/NEWS
index 0c1ca82e..9b654a35 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,7 @@ serd (0.31.0) unstable; urgency=medium
   * Fix incorrect parsing of strange quote escape patterns
   * Fix possible hang when writing nested Turtle lists
   * Fix potential memory leaks when a write is aborted
+  * Fix relative URI creation
   * Gracefully handle bad characters in Turtle blank node syntax
   * Gracefully handle bad characters in Turtle datatype syntax
   * Improve TriG pretty-printing and remove trailing newlines
@@ -20,7 +21,7 @@ serd (0.31.0) unstable; urgency=medium
   * Replace duplicated dox_to_sphinx script with sphinxygen dependency
   * Test header for warnings more strictly
 
- -- David Robillard <d@drobilla.net>  Sun, 26 Mar 2023 23:59:39 +0000
+ -- David Robillard <d@drobilla.net>  Wed, 29 Mar 2023 23:55:55 +0000
 
 serd (0.30.16) stable; urgency=medium
 
diff --git a/src/uri.c b/src/uri.c
index 8acb79b3..dcdd8083 100644
--- a/src/uri.c
+++ b/src/uri.c
@@ -1,4 +1,4 @@
-// Copyright 2011-2020 David Robillard <d@drobilla.net>
+// Copyright 2011-2023 David Robillard <d@drobilla.net>
 // SPDX-License-Identifier: ISC
 
 #include "string_utils.h"
@@ -428,10 +428,6 @@ write_rel_path(SerdSink             sink,
     len += sink("../", 3, stream);
   }
 
-  if (last_shared_sep == 0 && up == 0) {
-    len += sink("/", 1, stream);
-  }
-
   // Write suffix
   return len + write_path_tail(sink, stream, uri, last_shared_sep + 1);
 }
@@ -468,8 +464,12 @@ serd_uri_serialise_relative(const SerdURI* const uri,
     if (uri->authority.buf) {
       len += sink("//", 2, stream);
       len += sink(uri->authority.buf, uri->authority.len, stream);
-      if (uri->authority.len > 0 &&
-          uri->authority.buf[uri->authority.len - 1] != '/' &&
+
+      const bool authority_ends_with_slash =
+        (uri->authority.len > 0 &&
+         uri->authority.buf[uri->authority.len - 1] == '/');
+
+      if (!authority_ends_with_slash &&
           serd_uri_path_starts_without_slash(uri)) {
         // Special case: ensure path begins with a slash
         // https://tools.ietf.org/html/rfc3986#section-3.2
diff --git a/src/uri_utils.h b/src/uri_utils.h
index 16819191..e2f30edb 100644
--- a/src/uri_utils.h
+++ b/src/uri_utils.h
@@ -12,6 +12,11 @@
 #include <stdint.h>
 #include <string.h>
 
+typedef struct {
+  size_t shared;
+  size_t root;
+} SlashIndexes;
+
 static inline bool
 chunk_equals(const SerdChunk* a, const SerdChunk* b)
 {
@@ -33,51 +38,64 @@ uri_path_at(const SerdURI* uri, size_t i)
 }
 
 /**
-   Return the index of the first differing character after the last root slash,
-   or zero if `uri` is not under `root`.
+   Return the index of the last slash shared with the root, or `SIZE_MAX`.
+
+   The index of the next slash found in the root is also returned, so the two
+   can be compared to determine if the URI is within the root (if the shared
+   slash is the last in the root, then the URI is a child of the root,
+   otherwise it may merely share some leading path components).
 */
-static inline SERD_PURE_FUNC size_t
+static inline SERD_PURE_FUNC SlashIndexes
 uri_rooted_index(const SerdURI* uri, const SerdURI* root)
 {
+  SlashIndexes indexes = {SIZE_MAX, SIZE_MAX};
+
   if (!root || !root->scheme.len ||
       !chunk_equals(&root->scheme, &uri->scheme) ||
       !chunk_equals(&root->authority, &uri->authority)) {
-    return 0;
+    return indexes;
   }
 
-  bool         differ          = false;
-  const size_t path_len        = uri_path_len(uri);
-  const size_t root_len        = uri_path_len(root);
-  size_t       last_root_slash = 0;
-  for (size_t i = 0; i < path_len && i < root_len; ++i) {
+  const size_t path_len = uri_path_len(uri);
+  const size_t root_len = uri_path_len(root);
+  const size_t min_len  = path_len < root_len ? path_len : root_len;
+  for (size_t i = 0; i < min_len; ++i) {
     const uint8_t u = uri_path_at(uri, i);
     const uint8_t r = uri_path_at(root, i);
 
-    differ = differ || u != r;
-    if (r == '/') {
-      last_root_slash = i;
-      if (differ) {
-        return 0;
+    if (u == r) {
+      if (u == '/') {
+        indexes.root = indexes.shared = i;
       }
+    } else {
+      for (size_t j = i; j < root_len; ++j) {
+        if (uri_path_at(root, j) == '/') {
+          indexes.root = j;
+          break;
+        }
+      }
+
+      return indexes;
     }
   }
 
-  return last_root_slash + 1;
+  return indexes;
 }
 
 /** Return true iff `uri` shares path components with `root` */
 static inline SERD_PURE_FUNC bool
 uri_is_related(const SerdURI* uri, const SerdURI* root)
 {
-  return uri_rooted_index(uri, root) > 0;
+  return uri_rooted_index(uri, root).shared != SIZE_MAX;
 }
 
 /** Return true iff `uri` is within the base of `root` */
 static inline SERD_PURE_FUNC bool
 uri_is_under(const SerdURI* uri, const SerdURI* root)
 {
-  const size_t index = uri_rooted_index(uri, root);
-  return index > 0 && uri->path.len > index;
+  const SlashIndexes indexes = uri_rooted_index(uri, root);
+  return indexes.shared && indexes.shared != SIZE_MAX &&
+         indexes.shared == indexes.root;
 }
 
 static inline bool
diff --git a/test/pretty/manifest.ttl b/test/pretty/manifest.ttl
index 1f653d65..69b951af 100644
--- a/test/pretty/manifest.ttl
+++ b/test/pretty/manifest.ttl
@@ -32,6 +32,7 @@
 		<#many-objects>
 		<#named-graph>
 		<#nested-list-object>
+		<#relative-uris>
 		<#short-string-escapes>
 		<#uri-escapes>
 		<#nested-list-subject>
@@ -193,6 +194,12 @@
 	mf:name "nested-list-subject" ;
 	mf:result <nested-list-subject.ttl> .
 
+<#relative-uris>
+	a rdft:TestTurtleEval ;
+	mf:action <relative-uris.ttl> ;
+	mf:name "relative-uris" ;
+	mf:result <relative-uris.ttl> .
+
 <#short-string-escapes>
 	a rdft:TestTurtleEval ;
 	mf:action <short-string-escapes.ttl> ;
diff --git a/test/pretty/relative-uris.ttl b/test/pretty/relative-uris.ttl
new file mode 100644
index 00000000..397c7cf7
--- /dev/null
+++ b/test/pretty/relative-uris.ttl
@@ -0,0 +1,2 @@
+<http://example.org/s>
+	<http://example.org/p> <manifest.ttl> .
diff --git a/test/root/root-inside-base-out.ttl b/test/root/root-inside-base-out.ttl
index a5081e4d..76f61791 100644
--- a/test/root/root-inside-base-out.ttl
+++ b/test/root/root-inside-base-out.ttl
@@ -1,7 +1,7 @@
 @base <http://example.org/top/> .
 @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
 
-<http://example.org/top/>
+<>
 	rdfs:label "base node" .
 
 <root/>
@@ -10,7 +10,7 @@
 <root/s>
 	rdfs:label "within root" .
 
-<s>
+<http://example.org/top/s>
 	rdfs:label "within base" .
 
 <http://example.org/other/s>
diff --git a/test/root/root-outside-base-out.ttl b/test/root/root-outside-base-out.ttl
index 47a4c47e..dcb95d5a 100644
--- a/test/root/root-outside-base-out.ttl
+++ b/test/root/root-outside-base-out.ttl
@@ -4,7 +4,7 @@
 <>
 	rdfs:label "base node" .
 
-<http://example.org/top/root/>
+<../>
 	rdfs:label "root node" .
 
 <s>
@@ -13,7 +13,7 @@
 <../s>
 	rdfs:label "within root" .
 
-<../../s>
+<http://example.org/top/s>
 	rdfs:label "outside root" .
 
 <http://example.com/s>
diff --git a/test/test_uri.c b/test/test_uri.c
index bcd670e5..ac24a2be 100644
--- a/test/test_uri.c
+++ b/test/test_uri.c
@@ -265,12 +265,8 @@ test_relative_uri(void)
 
   // Related base
 
-  /* Expected:
   check_relative_uri(
     "http://example.org/a/b", "http://example.org/", NULL, "a/b");
-  Actual: */
-  check_relative_uri(
-    "http://example.org/a/b", "http://example.org/", NULL, "/a/b");
 
   check_relative_uri(
     "http://example.org/a/b", "http://example.org/a/", NULL, "b");
@@ -286,10 +282,7 @@ test_relative_uri(void)
 
   check_relative_uri("http://example.org/", "http://example.org/", NULL, "");
 
-  /* Expected:
   check_relative_uri("http://example.org/", "http://example.org/a", NULL, "");
-  Actual: */
-  check_relative_uri("http://example.org/", "http://example.org/a", NULL, "/");
 
   check_relative_uri(
     "http://example.org/", "http://example.org/a/", NULL, "../");
@@ -337,10 +330,7 @@ test_relative_uri(void)
   check_relative_uri("http://example.org/a/",
                      "http://example.org/a/",
                      "http://example.org/a/",
-                     /* Expected:
                      "");
-                     Actual: */
-                     "http://example.org/a/");
 
   check_relative_uri("http://example.org/a/b",
                      "http://example.org/a/b/c",
@@ -350,10 +340,7 @@ test_relative_uri(void)
   check_relative_uri("http://example.org/a",
                      "http://example.org/a/b/c",
                      "http://example.org/a/b",
-                     /* Expected:
                      "http://example.org/a");
-                     Actual: */
-                     "../../a");
 }
 
 int