First version of the URL builder

build.bat

@@ -2,3 +2,4 @@ gcc -o 000_parse.exe         examples/000_parse.c         url.c -I. -Wall -Wextr
 gcc -o 001_serialize.exe     examples/001_serialize.c     url.c -I. -Wall -Wextra -ggdb
 gcc -o 002_partial_parse.exe examples/002_partial_parse.c url.c -I. -Wall -Wextra -ggdb
 gcc -o 003_references.exe    examples/003_references.c    url.c -I. -Wall -Wextra -ggdb
+gcc -o 004_build.exe         examples/004_build.c         url.c -I. -Wall -Wextra -ggdb

build.sh

@@ -2,3 +2,4 @@ gcc -o 000_parse.out         examples/000_parse.c         url.c -I. -Wall -Wextr
 gcc -o 001_serialize.out     examples/001_serialize.c     url.c -I. -Wall -Wextra -ggdb
 gcc -o 002_partial_parse.out examples/002_partial_parse.c url.c -I. -Wall -Wextra -ggdb
 gcc -o 003_references.out    examples/003_references.c    url.c -I. -Wall -Wextra -ggdb
+gcc -o 004_build.out         examples/004_build.c         url.c -I. -Wall -Wextra -ggdb

examples/004_build.c

@@ -0,0 +1,33 @@
+#include <url.h>
+#include <stdio.h>
+
+int main(void)
+{
+    URL_Builder builder;
+    url_builder_init(&builder);
+
+    url_builder_set_scheme(&builder, "http", -1);
+
+    url_builder_set_username(&builder, "cozis", -1);
+
+    url_builder_set_password(&builder, "my_secret", -1);
+
+    url_builder_set_host_name(&builder, "www.ex@mple.com", -1);
+
+    url_builder_set_path(&builder, "/../../index.html", -1);
+
+    char url[1<<9];
+    int len = url_builder_finalize(&builder, url, sizeof(url));
+    if (len < 0) {
+        printf("Couldn't build URL\n");
+        return -1;
+    }
+    if (len >= (int) sizeof(url)) {
+        printf("URL buffer is too small\n");
+        return -1;
+    }
+    url[len] = '\0';
+
+    printf("Built URL: %s\n", url);
+    return 0;
+}

url.c

@@ -35,7 +35,7 @@
 #define UINT16_MAX (URL_u16) ((1 << 16)-1)
 
 #define NULL ((void*) 0)
-#define S(X) ((URL_String) { (X), sizeof(X)-1 })
+#define S(X) (URL_String) { (X), sizeof(X)-1 }
 #define EMPTY (URL_String) { NULL, 0 }
 #define SLICE(src, off, end) (URL_String) { src + off, end - off }
 
@@ -49,6 +49,14 @@ static void memcpy_(char *dst, char *src, int len)
 }
 #endif
 
+static int strlen_(char *s)
+{
+    int n = 0;
+    while (s[n] != '\0')
+        n++;
+    return n;
+}
+
 static URL_b32 streq(URL_String a, URL_String b)
 {
     if (a.len != b.len)
@@ -784,6 +792,13 @@ static void append(Builder *b, URL_String s)
     b->len += s.len;
 }
 
+static void appendc(Builder *b, char c)
+{
+    if (b->len < b->cap)
+        b->dst[b->len] = c;
+    b->len++;
+}
+
 static void append_port(Builder *b, URL_u16 port)
 {
     char buf[sizeof("65536")-1];
@@ -998,3 +1013,162 @@ int url_percent_decode(URL_String str, char *dst, int cap)
     }
     return wr;
 }
+
+static void append_percent_encoded(Builder *b, URL_String str, URL_b32 (*testfn)(char c))
+{
+    for (int i = 0; i < str.len; i++) {
+        char c = str.ptr[i];
+        if (testfn(c))
+            appendc(b, str.ptr[i]);
+        else {
+            static const char table[] = "0123456789abcdef";
+            appendc(b, '%');
+            appendc(b, table[(URL_u8) c >> 4]);
+            appendc(b, table[(URL_u8) c & 0xF]);
+        }
+    }
+}
+
+void url_builder_init(URL_Builder *ub)
+{
+    ub->scheme    = EMPTY;
+    ub->username  = EMPTY;
+    ub->password  = EMPTY;
+    ub->host_type = URL_HOST_EMPTY;
+    ub->no_port   = 1;
+    ub->port      = 0;
+    ub->path      = EMPTY;
+    ub->query     = EMPTY;
+    ub->fragment  = EMPTY;
+}
+
+void url_builder_set_scheme(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->scheme = (URL_String) { str, len };
+}
+
+void url_builder_set_username(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->username = (URL_String) { str, len };
+}
+
+void url_builder_set_password(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->password = (URL_String) { str, len };
+}
+
+void url_builder_set_host_name(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->host_type = URL_HOST_NAME;
+    ub->host_name = (URL_String) { str, len };
+}
+
+void url_builder_set_host_ipv4(URL_Builder *ub, URL_IPv4 ipv4)
+{
+    ub->host_type = URL_HOST_IPV4;
+    ub->host_ipv4 = ipv4;
+}
+
+void url_builder_set_host_ipv6(URL_Builder *ub, URL_IPv6 ipv6)
+{
+    ub->host_type = URL_HOST_IPV6;
+    ub->host_ipv6 = ipv6;
+}
+
+void url_builder_set_port(URL_Builder *ub, URL_u16 port)
+{
+    ub->no_port = 0;
+    ub->port = port;
+}
+
+void url_builder_set_path(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->path = (URL_String) { str, len };
+}
+
+void url_builder_set_query(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->query = (URL_String) { str, len };
+}
+
+void url_builder_set_fragment(URL_Builder *ub, char *str, int len)
+{
+    if (len < 0) len = str ? strlen_(str) : 0;
+    ub->fragment = (URL_String) { str, len };
+}
+
+int url_builder_finalize(URL_Builder *ub, char *dst, int cap)
+{
+    Builder b = { dst, cap, 0 };
+
+    // Validate and append the schema
+    {
+        if (ub->scheme.len == 0 || !is_scheme_first(ub->scheme.ptr[0]))
+            return -1;
+        for (int i = 1; i < ub->scheme.len; i++)
+            if (!is_scheme(ub->scheme.ptr[i]))
+                return -1;
+        append(&b, ub->scheme);
+    }
+
+    URL_b32 authority = 0;
+    if (ub->username.len > 0 || ub->password.len > 0 || ub->host_type != URL_HOST_EMPTY || ub->no_port == 0) {
+        authority = 1;
+        appendc(&b, '/');
+        appendc(&b, '/');
+        if (ub->username.len > 0 || ub->password.len > 0) {
+            append_percent_encoded(&b, ub->username, is_userinfo);
+            appendc(&b, ':');
+            append_percent_encoded(&b, ub->password, is_userinfo);
+            appendc(&b, '@');
+        }
+        switch (ub->host_type) {
+        case URL_HOST_EMPTY:
+            // Do nothing
+            break;
+        case URL_HOST_NAME:
+            append_percent_encoded(&b, ub->host_name, is_reg_name);
+            break;
+        case URL_HOST_IPV4:
+            ASSERT(0); // TODO
+            break;
+        case URL_HOST_IPV6:
+            appendc(&b, '[');
+            ASSERT(0);
+            appendc(&b, ']');
+            break;
+        }
+        if (ub->no_port == 0) {
+            appendc(&b, ':');
+            append_port(&b, ub->port);
+        }
+    }
+
+    if (ub->path.len > 0) {
+
+        // If an authority is present, the path can't be relative
+        if (authority && ub->path.ptr[0] != '/')
+            return -1;
+
+        PathComps comps = {0};
+        if (resolve_dots_and_append_comps(&comps, ub->path) < 0)
+                return -1;
+        for (int i = 0; i < comps.count; i++) {
+            if (i > 0 || comps.first_slash)
+                append(&b, S("/"));
+            append_percent_encoded(&b, comps.stack[i], is_pchar);
+        }
+        if (comps.trailing_slash)
+            append(&b, S("/"));
+    }
+
+    append_query(&b, ub->query);
+    append_fragment(&b, ub->fragment);
+    return b.len;
+}

url.h

@@ -45,6 +45,7 @@ typedef enum {
     URL_HOST_NAME,
 } URL_HostType;
 
+// This struct's fields are strictly read-only.
 typedef struct {
 
     // Flags used to parse this URL
@@ -174,4 +175,39 @@ int url_percent_decode(URL_String str, char *dst, int cap);
 // though it's just a best-effor normalization for now.
 int url_serialize(URL url, URL *base, char *dst, int cap);
 
+typedef struct {
+
+    URL_String scheme;
+
+    URL_String username;
+    URL_String password;
+
+    URL_HostType host_type;
+    union {
+        URL_String host_name;
+        URL_IPv4   host_ipv4;
+        URL_IPv6   host_ipv6;
+    };
+
+    URL_b32    no_port;
+    URL_u16    port;
+
+    URL_String path;
+    URL_String query;
+    URL_String fragment;
+} URL_Builder;
+
+void url_builder_init(URL_Builder *ub);
+void url_builder_set_scheme(URL_Builder *ub, char *str, int len);
+void url_builder_set_username(URL_Builder *ub, char *str, int len);
+void url_builder_set_password(URL_Builder *ub, char *str, int len);
+void url_builder_set_host_name(URL_Builder *ub, char *str, int len);
+void url_builder_set_host_ipv4(URL_Builder *ub, URL_IPv4 ipv4);
+void url_builder_set_host_ipv6(URL_Builder *ub, URL_IPv6 ipv6);
+void url_builder_set_port(URL_Builder *ub, URL_u16 port);
+void url_builder_set_path(URL_Builder *ub, char *str, int len);
+void url_builder_set_query(URL_Builder *ub, char *str, int len);
+void url_builder_set_fragment(URL_Builder *ub, char *str, int len);
+int  url_builder_finalize(URL_Builder *ub, char *dst, int cap);
+
 #endif // URL_INCLUDED