Simplify URI API and implementation

13 files changed, 514 insertions, 443 deletions

diff --git a/include/serd/serd.h b/include/serd/serd.h
index 31b631b1..13ac1156 100644
--- a/include/serd/serd.h
+++ b/include/serd/serd.h
@@ -302,22 +302,43 @@ typedef size_t (*SerdSink)(const void* SERD_NONNULL buf,
 /**
    A parsed URI.
 
-   This struct directly refers to slices in other strings, it does not own any
-   memory itself.  This allows some URI operations like resolution to be done
-   in-place without allocating memory.
+   This URI representation is designed for fast streaming, it allows creating
+   relative URI references or resolving them into absolute URIs in-place
+   without any string allocation.
+
+   Each component refers to slices in other strings, so a URI view must outlive
+   any strings it was parsed from.  The components are not necessarily
+   null-terminated.
+
+   The scheme, authority, path, query, and fragment simply point to the string
+   value of those components, not including any delimiters.  The path_prefix is
+   a special component for storing relative or resolved paths.  If it points to
+   a string (usually a base URI the URI was resolved against), then this string
+   is prepended to the path.  Otherwise, the length is interpret as the number
+   of up-references ("../") that must be prepended to the path.
 */
 typedef struct {
-  SerdStringView scheme;    ///< Scheme
-  SerdStringView authority; ///< Authority
-  SerdStringView path_base; ///< Path prefix if relative
-  SerdStringView path;      ///< Path suffix
-  SerdStringView query;     ///< Query
-  SerdStringView fragment;  ///< Fragment
+  SerdStringView scheme;      ///< Scheme
+  SerdStringView authority;   ///< Authority
+  SerdStringView path_prefix; ///< Path prefix for relative/resolved paths
+  SerdStringView path;        ///< Path suffix
+  SerdStringView query;       ///< Query
+  SerdStringView fragment;    ///< Fragment
 } SerdURIView;
 
 static const SerdURIView SERD_URI_NULL =
   {{NULL, 0}, {NULL, 0}, {NULL, 0}, {NULL, 0}, {NULL, 0}, {NULL, 0}};
 
+/// Return true iff `string` starts with a valid URI scheme
+SERD_PURE_API
+bool
+serd_uri_string_has_scheme(const char* SERD_NONNULL string);
+
+/// Parse `string` and return a URI view that points into it
+SERD_PURE_API
+SerdURIView
+serd_parse_uri(const char* SERD_NONNULL string);
+
 /**
    Get the unescaped path and hostname from a file URI.
 
@@ -325,55 +346,83 @@ static const SerdURIView SERD_URI_NULL =
 
    @param uri A file URI.
    @param hostname If non-NULL, set to the hostname, if present.
-   @return The path component of the URI.
+   @return A filesystem path.
 */
 SERD_API
 char* SERD_NULLABLE
-serd_file_uri_parse(const char* SERD_NONNULL uri,
+serd_parse_file_uri(const char* SERD_NONNULL          uri,
                     char* SERD_NONNULL* SERD_NULLABLE hostname);
 
-/// Return true iff `utf8` starts with a valid URI scheme
-SERD_PURE_API
-bool
-serd_uri_string_has_scheme(const char* SERD_NULLABLE utf8);
+/**
+   Return reference `r` resolved against `base`.
 
-/// Parse `utf8`, writing result to `out`
-SERD_API
-SerdStatus
-serd_uri_parse(const char* SERD_NONNULL utf8, SerdURIView* SERD_NONNULL out);
+   This will make `r` an absolute URI if possible.
+
+   @see [RFC3986 5.2.2](http://tools.ietf.org/html/rfc3986#section-5.2.2)
+
+   @param r URI reference to make absolute, for example "child/path".
+
+   @param base Base URI, for example "http://example.org/base/".
+
+   @return An absolute URI, for example "http://example.org/base/child/path",
+   or `r` if it is not a URI reference that can be resolved against `base`.
+*/
+SERD_PURE_API
+SerdURIView
+serd_resolve_uri(SerdURIView r, SerdURIView base);
 
 /**
-   Set target `t` to reference `r` resolved against `base`.
+   Return `r` as a reference relative to `base` if possible.
 
    @see [RFC3986 5.2.2](http://tools.ietf.org/html/rfc3986#section-5.2.2)
+
+   @param r URI to make relative, for example
+   "http://example.org/base/child/path".
+
+   @param base Base URI, for example "http://example.org/base".
+
+   @return A relative URI reference, for example "child/path", `r` if it can
+   not be made relative to `base`, or a null URI if `r` could be made relative
+   to base, but the path prefix is already being used (most likely because `r`
+   was previously a relative URI reference that was resolved against some
+   base).
 */
-SERD_API
-void
-serd_uri_resolve(const SerdURIView* SERD_NONNULL r,
-                 const SerdURIView* SERD_NONNULL base,
-                 SerdURIView* SERD_NONNULL       t);
+SERD_PURE_API
+SerdURIView
+serd_relative_uri(SerdURIView r, SerdURIView base);
 
-/// Serialise `uri` with a series of calls to `sink`
-SERD_API
-size_t
-serd_uri_serialise(const SerdURIView* SERD_NONNULL uri,
-                   SerdSink SERD_NONNULL           sink,
-                   void* SERD_NONNULL              stream);
+/**
+   Return whether `r` can be written as a reference relative to `base`.
+
+   For example, with `base` "http://example.org/base/", this returns true if
+   `r` is also "http://example.org/base/", or something like
+   "http://example.org/base/child" ("child")
+   "http://example.org/base/child/grandchild#fragment"
+   ("child/grandchild#fragment"),
+   "http://example.org/base/child/grandchild?query" ("child/grandchild?query"),
+   and so on.
+
+   @return True if `r` and `base` are equal or if `r` is a child of `base`.
+*/
+SERD_PURE_API
+bool
+serd_uri_is_within(SerdURIView r, SerdURIView base);
 
 /**
-   Serialise `uri` relative to `base` with a series of calls to `sink`
+   Write `uri` as a string to `sink`.
+
+   This will call `sink` several times to emit the URI.
 
-   The `uri` is written as a relative URI iff if it a child of `base` and
-   `root`.  The optional `root` parameter must be a prefix of `base` and can be
-   used keep up-references ("../") within a certain namespace.
+   @param uri URI to write as a string.
+   @param sink Sink to write string output to.
+   @param stream Opaque user argument to pass to `sink`.
+   @return The number of bytes written.
 */
 SERD_API
 size_t
-serd_uri_serialise_relative(const SerdURIView* SERD_NONNULL  uri,
-                            const SerdURIView* SERD_NULLABLE base,
-                            const SerdURIView* SERD_NULLABLE root,
-                            SerdSink SERD_NONNULL            sink,
-                            void* SERD_NONNULL               stream);
+serd_write_uri(SerdURIView           uri,
+               SerdSink SERD_NONNULL sink,
+               void* SERD_NONNULL    stream);
 
 /**
    @}
@@ -450,16 +499,12 @@ serd_new_substring(SerdNodeType              type,
 /// Simple wrapper for serd_new_uri() to resolve a URI node
 SERD_API
 SerdNode* SERD_ALLOCATED
-serd_new_uri_from_node(const SerdNode* SERD_NONNULL     uri_node,
-                       const SerdURIView* SERD_NULLABLE base,
-                       SerdURIView* SERD_NULLABLE       out);
+serd_new_uri(const char* SERD_NONNULL str);
 
-/// Simple wrapper for serd_new_uri() to resolve a URI string
+/// Create a new URI from a URI view
 SERD_API
 SerdNode* SERD_ALLOCATED
-serd_new_uri_from_string(const char* SERD_NULLABLE        str,
-                         const SerdURIView* SERD_NULLABLE base,
-                         SerdURIView* SERD_NULLABLE       out);
+serd_new_parsed_uri(SerdURIView uri);
 
 /**
    Create a new file URI node from a file system path and optional hostname.
@@ -477,41 +522,6 @@ serd_new_file_uri(const char* SERD_NONNULL   path,
                   SerdURIView* SERD_NULLABLE out);
 
 /**
-   Create a new node by serialising `uri` into a new string.
-
-   @param uri The URI to serialise.
-
-   @param base Base URI to resolve `uri` against (or NULL for no resolution).
-
-   @param out Set to the parsing of the new URI (i.e. points only to
-   memory owned by the new returned node).
-*/
-SERD_API
-SerdNode* SERD_ALLOCATED
-serd_new_uri(const SerdURIView* SERD_NONNULL  uri,
-             const SerdURIView* SERD_NULLABLE base,
-             SerdURIView* SERD_NULLABLE       out);
-
-/**
-   Create a new node by serialising `uri` into a new relative URI.
-
-   @param uri The URI to serialise.
-
-   @param base Base URI to make `uri` relative to, if possible.
-
-   @param root Root URI for resolution (see serd_uri_serialise_relative()).
-
-   @param out Set to the parsing of the new URI (i.e. points only to
-   memory owned by the new returned node).
-*/
-SERD_API
-SerdNode* SERD_ALLOCATED
-serd_new_relative_uri(const SerdURIView* SERD_NONNULL  uri,
-                      const SerdURIView* SERD_NULLABLE base,
-                      const SerdURIView* SERD_NULLABLE root,
-                      SerdURIView* SERD_NULLABLE       out);
-
-/**
    Create a new node by serialising `d` into an xsd:decimal string.
 
    The resulting node will always contain a `.', start with a digit, and end
@@ -595,7 +605,7 @@ serd_node_string_view(const SerdNode* SERD_NONNULL node);
    idea to keep the value if you will be using it several times in the same
    scope.
 */
-SERD_API
+SERD_PURE_API
 SerdURIView
 serd_node_uri_view(const SerdNode* SERD_NONNULL node);
 
diff --git a/src/env.c b/src/env.c
index 84fd43d4..b4824aae 100644
--- a/src/env.c
+++ b/src/env.c
@@ -86,15 +86,16 @@ serd_env_set_base_uri(SerdEnv* const env, const SerdNode* const uri)
     return SERD_SUCCESS;
   }
 
-  // Resolve base URI and create a new node and URI for it
-  SerdURIView base_uri;
-  SerdNode*   base_uri_node =
-    serd_new_uri_from_node(uri, &env->base_uri, &base_uri);
+  // Resolve the new base against the current base in case it is relative
+  const SerdURIView new_base_uri =
+    serd_resolve_uri(serd_parse_uri(serd_node_string(uri)), env->base_uri);
+
+  SerdNode* const new_base_node = serd_new_parsed_uri(new_base_uri);
 
   // Replace the current base URI
   serd_node_free(env->base_uri_node);
-  env->base_uri_node = base_uri_node;
-  env->base_uri      = base_uri;
+  env->base_uri_node = new_base_node;
+  env->base_uri      = serd_node_uri_view(env->base_uri_node);
 
   return SERD_SUCCESS;
 }
@@ -149,17 +150,22 @@ serd_env_set_prefix(SerdEnv* const        env,
   if (serd_uri_string_has_scheme(serd_node_string(uri))) {
     // Set prefix to absolute URI
     serd_env_add(env, name, uri);
-  } else {
-    // Resolve relative URI and create a new node and URI for it
-    SerdURIView abs_uri;
-    SerdNode*   abs_uri_node =
-      serd_new_uri_from_node(uri, &env->base_uri, &abs_uri);
-
-    // Set prefix to resolved (absolute) URI
-    serd_env_add(env, name, abs_uri_node);
-    serd_node_free(abs_uri_node);
+    return SERD_SUCCESS;
+  }
+
+  if (!env->base_uri_node) {
+    return SERD_ERR_BAD_ARG;
   }
 
+  // Resolve relative URI and create a new node and URI for it
+  SerdNode* const abs_uri =
+    serd_new_resolved_uri(serd_node_string_view(uri), env->base_uri);
+
+  // Set prefix to resolved (absolute) URI
+  serd_env_add(env, name, abs_uri);
+
+  serd_node_free(abs_uri);
+
   return SERD_SUCCESS;
 }
 
@@ -243,16 +249,15 @@ serd_env_expand_node(const SerdEnv* const env, const SerdNode* const node)
   switch (node->type) {
   case SERD_LITERAL:
     break;
-  case SERD_URI: {
-    SerdURIView ignored;
-    return serd_new_uri_from_node(node, &env->base_uri, &ignored);
-  }
+  case SERD_URI:
+    return serd_new_resolved_uri(serd_node_string_view(node), env->base_uri);
   case SERD_CURIE: {
     SerdStringView prefix;
     SerdStringView suffix;
     if (serd_env_expand(env, node, &prefix, &suffix)) {
       return NULL;
     }
+
     const size_t len = prefix.len + suffix.len;
     SerdNode*    ret = serd_node_malloc(len, 0, SERD_URI);
     char*        buf = serd_node_buffer(ret);
diff --git a/src/node.c b/src/node.c
index 07010684..854772ac 100644
--- a/src/node.c
+++ b/src/node.c
@@ -45,7 +45,7 @@ static const size_t serd_node_align = 2 * sizeof(uint64_t);
 static size_t
 serd_uri_string_length(const SerdURIView* const uri)
 {
-  size_t len = uri->path_base.len;
+  size_t len = uri->path_prefix.len;
 
 #define ADD_LEN(field, n_delims)     \
   if ((field).len) {                 \
@@ -164,29 +164,56 @@ serd_node_equals(const SerdNode* const a, const SerdNode* const b)
 }
 
 SerdNode*
-serd_new_uri_from_node(const SerdNode* const    uri_node,
-                       const SerdURIView* const base,
-                       SerdURIView* const       out)
+serd_new_uri(const char* const str)
 {
-  const char* uri_str = serd_node_string(uri_node);
-  return (uri_node && uri_node->type == SERD_URI && uri_str)
-           ? serd_new_uri_from_string(uri_str, base, out)
-           : NULL;
+  const size_t length = strlen(str);
+  SerdNode*    node   = serd_node_malloc(length, 0, SERD_URI);
+  memcpy(serd_node_buffer(node), str, length);
+  node->length = length;
+  return node;
 }
 
 SerdNode*
-serd_new_uri_from_string(const char* const        str,
-                         const SerdURIView* const base,
-                         SerdURIView* const       out)
+serd_new_parsed_uri(const SerdURIView uri)
+{
+  const size_t    len        = serd_uri_string_length(&uri);
+  SerdNode* const node       = serd_node_malloc(len, 0, SERD_URI);
+  char*           ptr        = serd_node_buffer(node);
+  const size_t    actual_len = serd_write_uri(uri, string_sink, &ptr);
+
+  serd_node_buffer(node)[actual_len] = '\0';
+  node->length                       = actual_len;
+
+  return node;
+}
+
+static SerdNode*
+serd_new_from_uri(const SerdURIView uri, const SerdURIView base)
 {
-  if (!str || str[0] == '\0') {
-    // Empty URI => Base URI, or nothing if no base is given
-    return base ? serd_new_uri(base, NULL, out) : NULL;
+  const SerdURIView abs_uri    = serd_resolve_uri(uri, base);
+  const size_t      len        = serd_uri_string_length(&abs_uri);
+  SerdNode*         node       = serd_node_malloc(len, 0, SERD_URI);
+  char*             ptr        = serd_node_buffer(node);
+  const size_t      actual_len = serd_write_uri(abs_uri, string_sink, &ptr);
+
+  serd_node_buffer(node)[actual_len] = '\0';
+  node->length                       = actual_len;
+
+  return node;
+}
+
+SerdNode*
+serd_new_resolved_uri(const SerdStringView string, const SerdURIView base)
+{
+  const SerdURIView uri    = serd_parse_uri(string.buf);
+  SerdNode* const   result = serd_new_from_uri(uri, base);
+
+  if (!serd_uri_string_has_scheme(serd_node_string(result))) {
+    serd_node_free(result);
+    return NULL;
   }
 
-  SerdURIView uri;
-  serd_uri_parse(str, &uri);
-  return serd_new_uri(&uri, base, out); // Resolve/Serialise
+  return result;
 }
 
 static bool
@@ -270,61 +297,13 @@ serd_new_file_uri(const char* const  path,
   SerdNode* node =
     serd_new_substring(SERD_URI, (const char*)buffer.buf, buffer.len);
   if (out) {
-    serd_uri_parse(serd_node_buffer(node), out);
+    *out = serd_parse_uri(serd_node_buffer(node));
   }
 
   free(buffer.buf);
   return node;
 }
 
-SerdNode*
-serd_new_uri(const SerdURIView* const uri,
-             const SerdURIView* const base,
-             SerdURIView* const       out)
-{
-  SerdURIView abs_uri = *uri;
-  if (base) {
-    serd_uri_resolve(uri, base, &abs_uri);
-  }
-
-  const size_t len        = serd_uri_string_length(&abs_uri);
-  SerdNode*    node       = serd_node_malloc(len, 0, SERD_URI);
-  char*        ptr        = serd_node_buffer(node);
-  const size_t actual_len = serd_uri_serialise(&abs_uri, string_sink, &ptr);
-
-  serd_node_buffer(node)[actual_len] = '\0';
-  node->length                       = actual_len;
-
-  if (out) {
-    serd_uri_parse(serd_node_buffer(node), out); // TODO: avoid double parse
-  }
-
-  return node;
-}
-
-SerdNode*
-serd_new_relative_uri(const SerdURIView* const uri,
-                      const SerdURIView* const base,
-                      const SerdURIView* const root,
-                      SerdURIView* const       out)
-{
-  const size_t uri_len  = serd_uri_string_length(uri);
-  const size_t base_len = serd_uri_string_length(base);
-  SerdNode*    node     = serd_node_malloc(uri_len + base_len, 0, SERD_URI);
-  char*        ptr      = serd_node_buffer(node);
-  const size_t actual_len =
-    serd_uri_serialise_relative(uri, base, root, string_sink, &ptr);
-
-  serd_node_buffer(node)[actual_len] = '\0';
-  node->length                       = actual_len;
-
-  if (out) {
-    serd_uri_parse(serd_node_buffer(node), out); // TODO: avoid double parse
-  }
-
-  return node;
-}
-
 static unsigned
 serd_digits(const double abs)
 {
@@ -461,13 +440,8 @@ serd_node_string_view(const SerdNode* const node)
 SerdURIView
 serd_node_uri_view(const SerdNode* const node)
 {
-  SerdURIView result = SERD_URI_NULL;
-
-  if (node->type == SERD_URI) {
-    serd_uri_parse(serd_node_string(node), &result);
-  }
-
-  return result;
+  return (node->type == SERD_URI) ? serd_parse_uri(serd_node_string(node))
+                                  : SERD_URI_NULL;
 }
 
 SerdNodeFlags
diff --git a/src/node.h b/src/node.h
index 5e5b3881..69b36c3c 100644
--- a/src/node.h
+++ b/src/node.h
@@ -46,4 +46,8 @@ void
 serd_node_set(SerdNode* SERD_NULLABLE* SERD_NONNULL dst,
               const SerdNode* SERD_NULLABLE         src);
 
+/// Create a new URI from a string, resolved against a base URI
+SerdNode* SERD_ALLOCATED
+serd_new_resolved_uri(SerdStringView string, SerdURIView base_uri);
+
 #endif // SERD_NODE_H
diff --git a/src/reader.c b/src/reader.c
index 86df3134..ff53ab46 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -284,7 +284,7 @@ serd_reader_set_default_graph(SerdReader* const     reader,
 SerdStatus
 serd_reader_read_file(SerdReader* const reader, const char* const uri)
 {
-  char* const path = serd_file_uri_parse(uri, NULL);
+  char* const path = serd_parse_file_uri(uri, NULL);
   if (!path) {
     return SERD_ERR_BAD_ARG;
   }
diff --git a/src/serdi.c b/src/serdi.c
index babe4575..e86042bb 100644
--- a/src/serdi.c
+++ b/src/serdi.c
@@ -293,7 +293,7 @@ main(int argc, char** argv)
     in_name = in_name ? in_name : input;
     if (!in_fd) {
       if (!strncmp(input, "file:", 5)) {
-        input_path = serd_file_uri_parse(input, NULL);
+        input_path = serd_parse_file_uri(input, NULL);
         input      = input_path;
       }
       if (!input || !(in_fd = serd_fopen(input, "rb"))) {
@@ -319,7 +319,8 @@ main(int argc, char** argv)
   SerdURIView base_uri = SERD_URI_NULL;
   SerdNode*   base     = NULL;
   if (a < argc) { // Base URI given on command line
-    base = serd_new_uri_from_string((const char*)argv[a], NULL, &base_uri);
+    base_uri = serd_parse_uri(argv[a]);
+    base     = serd_new_parsed_uri(base_uri);
   } else if (from_file && in_fd != stdin) { // Use input file URI
     base = serd_new_file_uri(input, NULL, &base_uri);
   }
diff --git a/src/uri.c b/src/uri.c
index 60f387b0..2c9c6db2 100644
--- a/src/uri.c
+++ b/src/uri.c
@@ -20,18 +20,18 @@
 #include "serd/serd.h"
 
 #include <stdbool.h>
-#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 char*
-serd_file_uri_parse(const char* const uri, char** const hostname)
+serd_parse_file_uri(const char* const uri, char** const hostname)
 {
   const char* path = uri;
   if (hostname) {
     *hostname = NULL;
   }
+
   if (!strncmp(uri, "file://", 7)) {
     const char* auth = uri + 7;
     if (*auth == '/') { // No hostname
@@ -40,6 +40,7 @@ serd_file_uri_parse(const char* const uri, char** const hostname)
       if (!(path = strchr(auth, '/'))) {
         return NULL;
       }
+
       if (hostname) {
         const size_t len = (size_t)(path - auth);
         *hostname        = (char*)calloc(len + 1, 1);
@@ -70,36 +71,34 @@ serd_file_uri_parse(const char* const uri, char** const hostname)
       serd_buffer_sink(s, 1, &buffer);
     }
   }
+
   return serd_buffer_sink_finish(&buffer);
 }
 
+/// RFC3986: scheme ::= ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
 bool
-serd_uri_string_has_scheme(const char* utf8)
+serd_uri_string_has_scheme(const char* const string)
 {
-  // RFC3986: scheme ::= ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
-  if (!utf8 || !is_alpha(utf8[0])) {
-    return false; // Invalid scheme initial character, URI is relative
-  }
-
-  for (char c = 0; (c = *++utf8) != '\0';) {
-    if (!is_uri_scheme_char(c)) {
-      return false;
-    }
+  if (is_alpha(string[0])) {
+    for (size_t i = 1; string[i]; ++i) {
+      if (!is_uri_scheme_char(string[i])) {
+        return false; // Non-scheme character before a ':'
+      }
 
-    if (c == ':') {
-      return true; // End of scheme
+      if (string[i] == ':') {
+        return true; // Valid scheme terminated by a ':'
+      }
     }
   }
 
-  return false;
+  return false; // String doesn't start with a scheme
 }
 
-SerdStatus
-serd_uri_parse(const char* const utf8, SerdURIView* const out)
+SerdURIView
+serd_parse_uri(const char* const string)
 {
-  *out = SERD_URI_NULL;
-
-  const char* ptr = utf8;
+  SerdURIView result = SERD_URI_NULL;
+  const char* ptr    = string;
 
   /* See http://tools.ietf.org/html/rfc3986#section-3
      URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ]
@@ -113,11 +112,11 @@ serd_uri_parse(const char* const utf8, SerdURIView* const out)
       case '/':
       case '?':
       case '#':
-        ptr = utf8;
+        ptr = string;
         goto path; // Relative URI (starts with path by definition)
       case ':':
-        out->scheme.buf = utf8;
-        out->scheme.len = (size_t)((ptr++) - utf8);
+        result.scheme.buf = string;
+        result.scheme.len = (size_t)((ptr++) - string);
         goto maybe_authority; // URI with scheme
       case '+':
       case '-':
@@ -138,7 +137,7 @@ serd_uri_parse(const char* const utf8, SerdURIView* const out)
 maybe_authority:
   if (*ptr == '/' && *(ptr + 1) == '/') {
     ptr += 2;
-    out->authority.buf = ptr;
+    result.authority.buf = ptr;
     for (char c = 0; (c = *ptr) != '\0'; ++ptr) {
       switch (c) {
       case '/':
@@ -148,7 +147,7 @@ maybe_authority:
       case '#':
         goto fragment;
       default:
-        ++out->authority.len;
+        ++result.authority.len;
       }
     }
   }
@@ -167,8 +166,8 @@ path:
   default:
     break;
   }
-  out->path.buf = ptr;
-  out->path.len = 0;
+  result.path.buf = ptr;
+  result.path.len = 0;
   for (char c = 0; (c = *ptr) != '\0'; ++ptr) {
     switch (c) {
     case '?':
@@ -176,7 +175,7 @@ path:
     case '#':
       goto fragment;
     default:
-      ++out->path.len;
+      ++result.path.len;
     }
   }
 
@@ -186,12 +185,12 @@ path:
   */
 query:
   if (*ptr == '?') {
-    out->query.buf = ++ptr;
+    result.query.buf = ++ptr;
     for (char c = 0; (c = *ptr) != '\0'; ++ptr) {
       if (c == '#') {
         goto fragment;
       }
-      ++out->query.len;
+      ++result.query.len;
     }
   }
 
@@ -201,14 +200,14 @@ query:
   */
 fragment:
   if (*ptr == '#') {
-    out->fragment.buf = ptr;
+    result.fragment.buf = ptr;
     while (*ptr++ != '\0') {
-      ++out->fragment.len;
+      ++result.fragment.len;
     }
   }
 
 end:
-  return SERD_SUCCESS;
+  return result;
 }
 
 /**
@@ -220,62 +219,31 @@ end:
 static const char*
 remove_dot_segments(const char* const path, const size_t len, size_t* const up)
 {
-  const char*       begin = path;
-  const char* const end   = path + len;
-
   *up = 0;
-  while (begin < end) {
-    switch (begin[0]) {
-    case '.':
-      switch (begin[1]) {
-      case '/':
-        begin += 2; // Chop leading "./"
-        break;
-      case '.':
-        switch (begin[2]) {
-        case '\0':
-          ++*up;
-          begin += 2; // Chop input ".."
-          break;
-        case '/':
-          ++*up;
-          begin += 3; // Chop leading "../"
-          break;
-        default:
-          return begin;
-        }
-        break;
-      case '\0':
-        return ++begin; // Chop input "."
-      default:
-        return begin;
-      }
-      break;
-    case '/':
-      switch (begin[1]) {
-      case '.':
-        switch (begin[2]) {
-        case '/':
-          begin += 2; // Leading "/./" => "/"
-          break;
-        case '.':
-          switch (begin[3]) {
-          case '/':
-            ++*up;
-            begin += 3; // Leading "/../" => "/"
-          }
-          break;
-        default:
-          return begin;
-        }
-      }
-      return begin;
-    default:
-      return begin; // Finished chopping dot components
+
+  for (size_t i = 0; i < len;) {
+    const char* const p = path + i;
+    if (!strncmp(p, "./", 2)) {
+      i += 2; // Chop leading "./"
+    } else if (!strcmp(p, "..")) {
+      ++*up;
+      i += 2; // Chop input ".."
+    } else if (!strncmp(p, "../", 3)) {
+      ++*up;
+      i += 3; // Chop leading "../"
+    } else if (!strcmp(p, ".")) {
+      ++i; // Chop input "."
+    } else if (!strncmp(p, "/./", 3)) {
+      i += 2; // Leading "/./" => "/"
+    } else if (!strncmp(p, "/../", 4)) {
+      ++*up;
+      i += 3; // Leading "/../" => "/"
+    } else {
+      return p;
     }
   }
 
-  return begin;
+  return path + len;
 }
 
 /// Merge `base` and `path` in-place
@@ -306,179 +274,185 @@ merge(SerdStringView* const base, SerdStringView* const path)
 }
 
 /// See http://tools.ietf.org/html/rfc3986#section-5.2.2
-void
-serd_uri_resolve(const SerdURIView* const r,
-                 const SerdURIView* const base,
-                 SerdURIView* const       t)
+SerdURIView
+serd_resolve_uri(const SerdURIView r, const SerdURIView base)
 {
-  if (!base->scheme.len) {
-    *t = *r; // Don't resolve against non-absolute URIs
-    return;
+  if (r.scheme.len || !base.scheme.len) {
+    return r; // No resolution necessary || possible (respectively)
   }
 
-  t->path_base.buf = NULL;
-  t->path_base.len = 0;
-  if (r->scheme.len) {
-    *t = *r;
+  SerdURIView t = SERD_URI_NULL;
+
+  if (r.authority.len) {
+    t.authority = r.authority;
+    t.path      = r.path;
+    t.query     = r.query;
   } else {
-    if (r->authority.len) {
-      t->authority = r->authority;
-      t->path      = r->path;
-      t->query     = r->query;
+    t.path = r.path;
+    if (!r.path.len) {
+      t.path_prefix = base.path;
+      t.query       = r.query.len ? r.query : base.query;
     } else {
-      t->path = r->path;
-      if (!r->path.len) {
-        t->path_base = base->path;
-        if (r->query.len) {
-          t->query = r->query;
-        } else {
-          t->query = base->query;
-        }
-      } else {
-        if (r->path.buf[0] != '/') {
-          t->path_base = base->path;
-        }
-        merge(&t->path_base, &t->path);
-        t->query = r->query;
+      if (r.path.buf[0] != '/') {
+        t.path_prefix = base.path;
       }
-      t->authority = base->authority;
+
+      merge(&t.path_prefix, &t.path);
+      t.query = r.query;
     }
-    t->scheme   = base->scheme;
-    t->fragment = r->fragment;
+
+    t.authority = base.authority;
   }
+
+  t.scheme   = base.scheme;
+  t.fragment = r.fragment;
+
+  return t;
 }
 
-/** Write the path of `uri` starting at index `i` */
-static size_t
-write_path_tail(SerdSink                 sink,
-                void* const              stream,
-                const SerdURIView* const uri,
-                const size_t             i)
+SerdURIView
+serd_relative_uri(const SerdURIView uri, const SerdURIView base)
 {
-  size_t len = 0;
-  if (i < uri->path_base.len) {
-    len += sink(uri->path_base.buf + i, uri->path_base.len - i, stream);
+  if (!uri_is_related(&uri, &base)) {
+    return uri;
   }
 
-  if (uri->path.buf) {
-    if (i < uri->path_base.len) {
-      len += sink(uri->path.buf, uri->path.len, stream);
-    } else {
-      const size_t j = (i - uri->path_base.len);
-      len += sink(uri->path.buf + j, uri->path.len - j, stream);
-    }
-  }
+  SerdURIView result = SERD_URI_NULL;
 
-  return len;
-}
+  // Regardless of the path, the query and/or fragment come along
+  result.query    = uri.query;
+  result.fragment = uri.fragment;
 
-/** Write the path of `uri` relative to the path of `base`. */
-static size_t
-write_rel_path(SerdSink                 sink,
-               void* const              stream,
-               const SerdURIView* const uri,
-               const SerdURIView* const base)
-{
-  const size_t path_len = uri_path_len(uri);
-  const size_t base_len = uri_path_len(base);
+  const size_t path_len = uri_path_len(&uri);
+  const size_t base_len = uri_path_len(&base);
   const size_t min_len  = (path_len < base_len) ? path_len : base_len;
 
   // Find the last separator common to both paths
   size_t last_shared_sep = 0;
   size_t i               = 0;
-  for (; i < min_len && uri_path_at(uri, i) == uri_path_at(base, i); ++i) {
-    if (uri_path_at(uri, i) == '/') {
+  for (; i < min_len && uri_path_at(&uri, i) == uri_path_at(&base, i); ++i) {
+    if (uri_path_at(&uri, i) == '/') {
       last_shared_sep = i;
     }
   }
 
-  if (i == path_len && i == base_len) { // Paths are identical
-    return 0;
+  // If the URI and base URI have identical paths, the relative path is empty
+  if (i == path_len && i == base_len) {
+    result.path.buf = uri.path.buf;
+    result.path.len = 0;
+    return result;
   }
 
+  // Otherwise, we need to build the relative path out of string slices
+
   // Find the number of up references ("..") required
   size_t up = 0;
   for (size_t s = last_shared_sep + 1; s < base_len; ++s) {
-    if (uri_path_at(base, s) == '/') {
+    if (uri_path_at(&base, s) == '/') {
       ++up;
     }
   }
 
-  // Write up references
-  size_t len = 0;
-  for (size_t u = 0; u < up; ++u) {
-    len += sink("../", 3, stream);
+  if (up > 0) {
+    if (last_shared_sep < uri.path_prefix.len) {
+      return SERD_URI_NULL;
+    }
+
+    // Special representation: NULL buffer and len set to the depth
+    result.path_prefix.len = up;
   }
 
-  if (last_shared_sep == 0 && up == 0) {
-    len += sink("/", 1, stream);
+  if (last_shared_sep < uri.path_prefix.len) {
+    result.path_prefix.buf = uri.path_prefix.buf + last_shared_sep + 1;
+    result.path_prefix.len = uri.path_prefix.len - last_shared_sep - 1;
+    result.path            = uri.path;
+  } else {
+    result.path.buf = uri.path.buf + last_shared_sep + 1;
+    result.path.len = uri.path.len - last_shared_sep - 1;
   }
 
-  // Write suffix
-  return len + write_path_tail(sink, stream, uri, last_shared_sep + 1);
+  return result;
 }
 
-static uint8_t
-serd_uri_path_starts_without_slash(const SerdURIView* uri)
+bool
+serd_uri_is_within(const SerdURIView uri, const SerdURIView base)
 {
-  return ((uri->path_base.len || uri->path.len) &&
-          ((!uri->path_base.len || uri->path_base.buf[0] != '/') &&
-           (!uri->path.len || uri->path.buf[0] != '/')));
+  if (!base.scheme.len || !slice_equals(&base.scheme, &uri.scheme) ||
+      !slice_equals(&base.authority, &uri.authority)) {
+    return false;
+  }
+
+  bool         differ   = false;
+  const size_t path_len = uri_path_len(&uri);
+  const size_t base_len = uri_path_len(&base);
+
+  size_t last_base_slash = 0;
+  for (size_t i = 0; i < path_len && i < base_len; ++i) {
+    const char u = uri_path_at(&uri, i);
+    const char b = uri_path_at(&base, i);
+
+    differ = differ || u != b;
+    if (b == '/') {
+      last_base_slash = i;
+      if (differ) {
+        return false;
+      }
+    }
+  }
+
+  for (size_t i = last_base_slash + 1; i < base_len; ++i) {
+    if (uri_path_at(&base, i) == '/') {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 /// See http://tools.ietf.org/html/rfc3986#section-5.3
 size_t
-serd_uri_serialise_relative(const SerdURIView* const uri,
-                            const SerdURIView* const base,
-                            const SerdURIView* const root,
-                            SerdSink                 sink,
-                            void* const              stream)
+serd_write_uri(const SerdURIView uri, SerdSink sink, void* const stream)
 {
-  size_t     len = 0;
-  const bool relative =
-    root ? uri_is_under(uri, root) : uri_is_related(uri, base);
+  size_t len = 0;
 
-  if (relative) {
-    len = write_rel_path(sink, stream, uri, base);
+  if (uri.scheme.buf) {
+    len += sink(uri.scheme.buf, uri.scheme.len, stream);
+    len += sink(":", 1, stream);
   }
 
-  if (!relative || (!len && base->query.buf)) {
-    if (uri->scheme.buf) {
-      len += sink(uri->scheme.buf, uri->scheme.len, stream);
-      len += sink(":", 1, stream);
+  if (uri.authority.buf) {
+    len += sink("//", 2, stream);
+    len += sink(uri.authority.buf, uri.authority.len, stream);
+
+    if (uri.authority.len > 0 && uri_path_len(&uri) > 0 &&
+        uri_path_at(&uri, 0) != '/') {
+      // Special case: ensure path begins with a slash
+      // https://tools.ietf.org/html/rfc3986#section-3.2
+      len += sink("/", 1, stream);
     }
-    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] != '/' &&
-          serd_uri_path_starts_without_slash(uri)) {
-        // Special case: ensure path begins with a slash
-        // https://tools.ietf.org/html/rfc3986#section-3.2
-        len += sink("/", 1, stream);
-      }
+  }
+
+  if (uri.path_prefix.buf) {
+    len += sink(uri.path_prefix.buf, uri.path_prefix.len, stream);
+  } else if (uri.path_prefix.len) {
+    for (size_t i = 0; i < uri.path_prefix.len; ++i) {
+      len += sink("../", 3, stream);
     }
-    len += write_path_tail(sink, stream, uri, 0);
   }
 
-  if (uri->query.buf) {
+  if (uri.path.buf) {
+    len += sink(uri.path.buf, uri.path.len, stream);
+  }
+
+  if (uri.query.buf) {
     len += sink("?", 1, stream);
-    len += sink(uri->query.buf, uri->query.len, stream);
+    len += sink(uri.query.buf, uri.query.len, stream);
   }
 
-  if (uri->fragment.buf) {
-    // Note uri->fragment.buf includes the leading `#'
-    len += sink(uri->fragment.buf, uri->fragment.len, stream);
+  if (uri.fragment.buf) {
+    // Note that uri.fragment.buf includes the leading `#'
+    len += sink(uri.fragment.buf, uri.fragment.len, stream);
   }
 
   return len;
 }
-
-/// See http://tools.ietf.org/html/rfc3986#section-5.3
-size_t
-serd_uri_serialise(const SerdURIView* const uri,
-                   SerdSink                 sink,
-                   void* const              stream)
-{
-  return serd_uri_serialise_relative(uri, NULL, NULL, sink, stream);
-}
diff --git a/src/uri_utils.h b/src/uri_utils.h
index 6b07ec48..865651ae 100644
--- a/src/uri_utils.h
+++ b/src/uri_utils.h
@@ -33,17 +33,17 @@ slice_equals(const SerdStringView* a, const SerdStringView* b)
 static inline size_t
 uri_path_len(const SerdURIView* uri)
 {
-  return uri->path_base.len + uri->path.len;
+  return uri->path_prefix.len + uri->path.len;
 }
 
 static inline char
 uri_path_at(const SerdURIView* uri, size_t i)
 {
-  if (i < uri->path_base.len) {
-    return uri->path_base.buf[i];
+  if (i < uri->path_prefix.len) {
+    return uri->path_prefix.buf[i];
   }
 
-  return uri->path.buf[i - uri->path_base.len];
+  return uri->path.buf[i - uri->path_prefix.len];
 }
 
 /**
@@ -60,10 +60,11 @@ uri_rooted_index(const SerdURIView* uri, const SerdURIView* root)
     return 0;
   }
 
-  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;
+  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 char u = uri_path_at(uri, i);
     const char r = uri_path_at(root, i);
@@ -85,7 +86,9 @@ static inline SERD_PURE_FUNC
 bool
 uri_is_related(const SerdURIView* uri, const SerdURIView* root)
 {
-  return uri_rooted_index(uri, root) > 0;
+  return root && root->scheme.len &&
+         slice_equals(&root->scheme, &uri->scheme) &&
+         slice_equals(&root->authority, &uri->authority);
 }
 
 /** Return true iff `uri` is within the base of `root` */
diff --git a/src/writer.c b/src/writer.c
index abfe327b..f0bd11eb 100644
--- a/src/writer.c
+++ b/src/writer.c
@@ -614,20 +614,21 @@ write_uri_node(SerdWriter* const writer,
 
   write_sep(writer, SEP_URI_BEGIN);
   if (writer->flags & SERD_WRITE_RESOLVED) {
+    const SerdURIView uri = serd_parse_uri(node_str);
+
     SerdURIView in_base_uri;
-    SerdURIView uri;
-    SerdURIView abs_uri;
     serd_env_base_uri(writer->env, &in_base_uri);
-    serd_uri_parse(node_str, &uri);
-    serd_uri_resolve(&uri, &in_base_uri, &abs_uri);
-    bool         rooted = uri_is_under(&writer->base_uri, &writer->root_uri);
-    SerdURIView* root   = rooted ? &writer->root_uri : &writer->base_uri;
-    if (!uri_is_under(&abs_uri, root) || writer->syntax == SERD_NTRIPLES ||
-        writer->syntax == SERD_NQUADS) {
-      serd_uri_serialise(&abs_uri, uri_sink, writer);
+
+    const SerdURIView  abs_uri = serd_resolve_uri(uri, in_base_uri);
+    const bool         rooted  = uri_is_under(&in_base_uri, &writer->root_uri);
+    const SerdURIView* root    = rooted ? &writer->root_uri : &in_base_uri;
+
+    if (writer->syntax == SERD_NTRIPLES || writer->syntax == SERD_NQUADS ||
+        !uri_is_under(&abs_uri, root) ||
+        !uri_is_related(&abs_uri, &in_base_uri)) {
+      serd_write_uri(abs_uri, uri_sink, writer);
     } else {
-      serd_uri_serialise_relative(
-        &uri, &writer->base_uri, root, uri_sink, writer);
+      serd_write_uri(serd_relative_uri(uri, in_base_uri), uri_sink, writer);
     }
   } else {
     write_uri_from_node(writer, node);
@@ -1026,7 +1027,7 @@ serd_writer_set_root_uri(SerdWriter* writer, const SerdNode* uri)
 
   if (uri) {
     writer->root_node = serd_node_copy(uri);
-    serd_uri_parse(serd_node_string(writer->root_node), &writer->root_uri);
+    writer->root_uri  = serd_parse_uri(serd_node_string(writer->root_node));
   }
 
   return SERD_SUCCESS;
diff --git a/test/.clang-tidy b/test/.clang-tidy
index 539d0b59..4e2b14eb 100644
--- a/test/.clang-tidy
+++ b/test/.clang-tidy
@@ -5,6 +5,7 @@ Checks: >
   -altera-*,
   -android-cloexec-fopen,
   -bugprone-easily-swappable-parameters,
+  -bugprone-reserved-identifier,
   -clang-analyzer-nullability.NullabilityBase,
   -clang-analyzer-nullability.NullableDereferenced,
   -clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling,
diff --git a/test/meson.build b/test/meson.build
index 61ed6d6f..308803bb 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -19,7 +19,7 @@ foreach unit : unit_tests
   test(unit,
        executable('test_@0@'.format(unit),
                   'test_@0@.c'.format(unit),
-                  c_args: c_warnings + prog_args,
+                  c_args: c_warnings + platform_args + prog_args,
                   dependencies: serd_dep),
        suite: 'unit')
 endforeach
diff --git a/test/test_env.c b/test/test_env.c
index b86783db..d470971e 100644
--- a/test/test_env.c
+++ b/test/test_env.c
@@ -36,6 +36,7 @@ test_env(void)
 {
   SerdNode* u   = serd_new_string(SERD_URI, "http://example.org/foo");
   SerdNode* b   = serd_new_string(SERD_CURIE, "invalid");
+  SerdNode* e   = serd_new_string(SERD_URI, "");
   SerdNode* c   = serd_new_string(SERD_CURIE, "eg.2:b");
   SerdNode* s   = serd_new_string(SERD_LITERAL, "hello");
   SerdEnv*  env = serd_env_new(NULL);
@@ -49,9 +50,13 @@ test_env(void)
 
   assert(serd_env_expand(env, NULL, &prefix, &suffix) == SERD_ERR_BAD_CURIE);
 
+  assert(serd_env_set_prefix_from_strings(env, "eg.3", "rel") ==
+         SERD_ERR_BAD_ARG);
+
   assert(!serd_env_expand_node(NULL, u));
   assert(!serd_env_expand_node(env, b));
   assert(!serd_env_expand_node(env, s));
+  assert(!serd_env_expand_node(env, e));
 
   assert(!serd_env_set_base_uri(env, NULL));
 
@@ -84,6 +89,12 @@ test_env(void)
 
   assert(!serd_env_set_base_uri(env, u));
   assert(serd_node_equals(serd_env_base_uri(env, NULL), u));
+
+  SerdNode* xe = serd_env_expand_node(env, e);
+  assert(xe);
+  assert(!strcmp(serd_node_string(xe), "http://example.org/foo"));
+  serd_node_free(xe);
+
   assert(!serd_env_set_base_uri(env, NULL));
   assert(!serd_env_base_uri(env, NULL));
 
@@ -92,6 +103,7 @@ test_env(void)
   serd_node_free(badpre);
   serd_node_free(s);
   serd_node_free(c);
+  serd_node_free(e);
   serd_node_free(b);
   serd_node_free(u);
 
diff --git a/test/test_uri.c b/test/test_uri.c
index 60e03ad8..60d93831 100644
--- a/test/test_uri.c
+++ b/test/test_uri.c
@@ -19,6 +19,7 @@
 #include "serd/serd.h"
 
 #include <assert.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 
@@ -35,7 +36,7 @@ test_file_uri(const char* hostname,
   SerdNode*   node         = serd_new_file_uri(path, hostname, 0);
   const char* node_str     = serd_node_string(node);
   char*       out_hostname = NULL;
-  char*       out_path     = serd_file_uri_parse(node_str, &out_hostname);
+  char*       out_path     = serd_parse_file_uri(node_str, &out_hostname);
   assert(!strcmp(node_str, expected_uri));
   assert((hostname && out_hostname) || (!hostname && !out_hostname));
   assert(!strcmp(out_path, expected_path));
@@ -57,75 +58,160 @@ test_uri_parsing(void)
   test_file_uri("bhost", "/foo/bar", "file://bhost/foo/bar", NULL);
   test_file_uri(NULL, "a/relative <path>", "a/relative%20%3Cpath%3E", NULL);
 
-  // Test tolerance of parsing junk URI escapes
+  // Missing trailing '/' after authority
+  assert(!serd_parse_file_uri("file://truncated", NULL));
 
-  char* out_path = serd_file_uri_parse("file:///foo/%0Xbar", NULL);
+  // Check that NULL hostname doesn't crash
+  char* out_path = serd_parse_file_uri("file://me/path", NULL);
+  assert(!strcmp(out_path, "/path"));
+  serd_free(out_path);
+
+  // Invalid first escape character
+  out_path = serd_parse_file_uri("file:///foo/%0Xbar", NULL);
+  assert(!strcmp(out_path, "/foo/bar"));
+  serd_free(out_path);
+
+  // Invalid second escape character
+  out_path = serd_parse_file_uri("file:///foo/%X0bar", NULL);
   assert(!strcmp(out_path, "/foo/bar"));
   serd_free(out_path);
 }
 
 static void
-test_uri_from_string(void)
+test_parse_uri(void)
 {
-  assert(!serd_new_uri_from_string(NULL, NULL, NULL));
+  const SerdStringView base = SERD_STRING("http://example.org/a/b/c/");
+
+  const SerdURIView base_uri  = serd_parse_uri(base.buf);
+  const SerdURIView empty_uri = serd_parse_uri("");
+
+  SerdNode* const nil =
+    serd_new_parsed_uri(serd_resolve_uri(empty_uri, base_uri));
 
-  SerdURIView base_uri;
-  SerdNode*   base =
-    serd_new_uri_from_string("http://example.org/", NULL, &base_uri);
-  SerdNode* nil  = serd_new_uri_from_string(NULL, &base_uri, NULL);
-  SerdNode* nil2 = serd_new_uri_from_string("", &base_uri, NULL);
   assert(serd_node_type(nil) == SERD_URI);
-  assert(!strcmp(serd_node_string(nil), serd_node_string(base)));
-  assert(serd_node_type(nil2) == SERD_URI);
-  assert(!strcmp(serd_node_string(nil2), serd_node_string(base)));
+  assert(!strcmp(serd_node_string(nil), base.buf));
+
   serd_node_free(nil);
-  serd_node_free(nil2);
-  serd_node_free(base);
 }
 
 static void
-test_relative_uri(void)
+check_is_within(const char* const uri_string,
+                const char* const base_uri_string,
+                const bool        expected)
 {
-  SerdURIView base_uri;
-  SerdNode*   base =
-    serd_new_uri_from_string("http://example.org/", NULL, &base_uri);
+  const SerdURIView uri      = serd_parse_uri(uri_string);
+  const SerdURIView base_uri = serd_parse_uri(base_uri_string);
 
-  SerdNode*   abs = serd_new_string(SERD_URI, "http://example.org/foo/bar");
-  SerdURIView abs_uri;
-  serd_uri_parse(serd_node_string(abs), &abs_uri);
+  assert(serd_uri_is_within(uri, base_uri) == expected);
+}
 
-  SerdURIView rel_uri;
-  SerdNode*   rel = serd_new_relative_uri(&abs_uri, &base_uri, NULL, &rel_uri);
-  assert(!strcmp(serd_node_string(rel), "/foo/bar"));
+static void
+test_is_within(void)
+{
+  static const char* const base = "http://example.org/base/";
+
+  check_is_within("http://example.org/base/", base, true);
+  check_is_within("http://example.org/base/kid?q", base, true);
+  check_is_within("http://example.org/base/kid", base, true);
+  check_is_within("http://example.org/base/kid#f", base, true);
+  check_is_within("http://example.org/base/kid?q#f", base, true);
+  check_is_within("http://example.org/base/kid/grandkid", base, true);
+
+  check_is_within("http://example.org/base", base, false);
+  check_is_within("http://example.org/based", base, false);
+  check_is_within("http://example.org/bose", base, false);
+  check_is_within("http://example.org/", base, false);
+  check_is_within("http://other.org/base", base, false);
+  check_is_within("ftp://other.org/base", base, false);
+  check_is_within("base", base, false);
+
+  check_is_within("http://example.org/", "rel", false);
+}
 
-  SerdNode* up = serd_new_relative_uri(&base_uri, &abs_uri, NULL, NULL);
-  assert(!strcmp(serd_node_string(up), "../"));
+static void
+check_rel_uri(const char*     uri_string,
+              const SerdNode* base,
+              const SerdNode* root,
+              const char*     expected)
+{
+  const SerdURIView base_uri = serd_node_uri_view(base);
+  const SerdURIView uri      = serd_parse_uri(uri_string);
+  const bool        is_within =
+    !root || serd_uri_is_within(uri, serd_node_uri_view(root));
 
-  SerdNode* noup = serd_new_relative_uri(&base_uri, &abs_uri, &abs_uri, NULL);
-  assert(!strcmp(serd_node_string(noup), "http://example.org/"));
+  SerdNode* const rel =
+    is_within ? serd_new_parsed_uri(serd_relative_uri(uri, base_uri))
+              : serd_new_uri(uri_string);
 
-  SerdNode*   x = serd_new_string(SERD_URI, "http://example.org/foo/x");
-  SerdURIView x_uri;
-  serd_uri_parse(serd_node_string(x), &x_uri);
+  const int ret = strcmp(serd_node_string(rel), expected);
+  serd_node_free(rel);
+  assert(!ret);
+}
 
-  SerdNode* x_rel = serd_new_relative_uri(&x_uri, &abs_uri, &abs_uri, NULL);
-  assert(!strcmp(serd_node_string(x_rel), "x"));
+static void
+test_relative_uri(void)
+{
+  SerdNode* const root = serd_new_uri("http://example.org/a/b/ignored");
+  SerdNode* const base = serd_new_uri("http://example.org/a/b/c/");
+
+  check_rel_uri("http://example.org/a/b/c/foo", base, NULL, "foo");
+  check_rel_uri("http://example.org/a/", base, NULL, "../../");
+  check_rel_uri("http://example.org/a/", base, root, "http://example.org/a/");
+  check_rel_uri("http://example.org/a/b/x", root, root, "x");
+  check_rel_uri("http://example.org/", base, NULL, "../../../");
+  check_rel_uri("http://drobilla.net/a", base, NULL, "http://drobilla.net/a");
+
+  {
+    // Check making a relative URI from a resolved URI
+    const SerdURIView ref  = serd_parse_uri("child");
+    const SerdURIView abs  = serd_resolve_uri(ref, serd_node_uri_view(base));
+    const SerdURIView rel  = serd_relative_uri(abs, serd_node_uri_view(root));
+    SerdNode* const   node = serd_new_parsed_uri(rel);
+
+    assert(!strcmp(serd_node_string(node), "c/child"));
+    serd_node_free(node);
+  }
+  {
+    // Check failure when path_prefix is not available for use
+    const SerdURIView top   = serd_parse_uri("http://example.org/a/");
+    const SerdURIView ref   = serd_parse_uri("up");
+    const SerdURIView up    = serd_resolve_uri(ref, top);
+    const SerdURIView upref = serd_relative_uri(up, serd_node_uri_view(base));
+
+    assert(!memcmp(&upref, &SERD_URI_NULL, sizeof(ref)));
+  }
 
-  serd_node_free(x_rel);
-  serd_node_free(x);
-  serd_node_free(noup);
-  serd_node_free(up);
-  serd_node_free(abs);
-  serd_node_free(rel);
   serd_node_free(base);
+  serd_node_free(root);
+}
+
+static void
+test_uri_resolution(void)
+{
+  static const SerdStringView base = SERD_STRING("http://example.org/a/b/c/");
+
+  static const SerdStringView base_foo =
+    SERD_STRING("http://example.org/a/b/c/foo");
+
+  const SerdURIView base_uri     = serd_parse_uri(base.buf);
+  const SerdURIView abs_foo_uri  = serd_parse_uri(base_foo.buf);
+  const SerdURIView rel_foo_uri  = serd_relative_uri(abs_foo_uri, base_uri);
+  const SerdURIView resolved_uri = serd_resolve_uri(rel_foo_uri, base_uri);
+
+  SerdNode* const resolved = serd_new_parsed_uri(resolved_uri);
+  assert(!strcmp(serd_node_string(resolved), "http://example.org/a/b/c/foo"));
+
+  serd_node_free(resolved);
 }
 
 int
 main(void)
 {
   test_uri_parsing();
-  test_uri_from_string();
+  test_parse_uri();
+  test_is_within();
   test_relative_uri();
+  test_uri_resolution();
 
   printf("Success\n");
   return 0;