fixes #539 Feature request: customizable http error page

4 files changed, 208 insertions, 0 deletions

diff --git a/docs/man/libnng.3.adoc b/docs/man/libnng.3.adoc
index 21a34a6a..70fd3be2 100644
--- a/docs/man/libnng.3.adoc
+++ b/docs/man/libnng.3.adoc
@@ -341,7 +341,10 @@ These functions are intended for use with HTTP server applications.
 |<<nng_http_server_get_tls.3http#,nng_http_server_get_tls()>>|get HTTP server TLS configuration
 |<<nng_http_server_hold.3http#,nng_http_server_get_tls()>>|get and hold HTTP server instance
 |<<nng_http_server_release.3http#,nng_http_server_get_tls()>>|release HTTP server instance
+|<<nng_http_server_set_error_file.3http#,nng_http_server_set_error_file()>>|set custom HTTP error file
+|<<nng_http_server_set_error_page.3http#,nng_http_server_set_error_page()>>|set custom HTTP error page
 |<<nng_http_server_set_tls.3http#,nng_http_server_set_tls()>>|set HTTP server TLS configuration
+|<<nng_http_server_res_error.3http#,nng_http_server_res_error()>>|use HTTP server error page
 |<<nng_http_server_start.3http#,nng_http_server_start()>>|start HTTP server
 |<<nng_http_server_stop.3http#,nng_http_server_stop()>>|stop HTTP server
 |===
diff --git a/docs/man/nng_http_server_res_error.3http.adoc b/docs/man/nng_http_server_res_error.3http.adoc
new file mode 100644
index 00000000..a62628f7
--- /dev/null
+++ b/docs/man/nng_http_server_res_error.3http.adoc
@@ -0,0 +1,63 @@
+= nng_http_server_res_error(3http)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nng_http_server_res_error - use HTTP server error page
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
+
+int nng_http_server_set_error_file(nng_http_server *server,
+        nng_http_res *response);
+----
+
+== DESCRIPTION
+
+The `nng_http_server_res_error()` sets the body of _response_
+to _server_'s error page, which may have been customized using the
+`<<nng_http_server_set_error_file.3http#,nng_http_server_error_file()>>`
+or
+`<<nng_http_server_set_error_page.3http#,nng_http_server_error_page()>>`
+functions.
+
+The status code of the _response_ should have already been set, either
+implicitly by allocating it with
+`<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error()>>`,
+or by calling
+`<<nng_http_res_set_status.3http#,nng_http_res_set_status()>>`.
+
+Any content body previously set for _response_ will be overridden by
+this function.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+[horizontal]
+`NNG_ENOMEM`:: Insufficient free memory exists.
+`NNG_ENOTSUP`:: HTTP not supported.
+
+== SEE ALSO
+
+[.text-left]
+<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error(3http)>>,
+<<nng_http_server_hold.3http#,nng_http_server_hold(3http)>>,
+<<nng_http_server_set_error_file.3http#,nng_http_server_set_error_file(3http)>>,
+<<nng_http_server_set_error_page.3http#,nng_http_server_set_error_page(3http)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng.7#,nng(7)>>
diff --git a/docs/man/nng_http_server_set_error_file.3http.adoc b/docs/man/nng_http_server_set_error_file.3http.adoc
new file mode 100644
index 00000000..dde8d980
--- /dev/null
+++ b/docs/man/nng_http_server_set_error_file.3http.adoc
@@ -0,0 +1,73 @@
+= nng_http_server_set_error_file(3http)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nng_http_server_set_error_file - set custom HTTP error file
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
+
+int nng_http_server_set_error_file(nng_http_server *server,
+        uint16_t code, const char *path);
+----
+
+== DESCRIPTION
+
+The `nng_http_server_set_error_file()` sets an error page to be used
+for HTTP status _code_ on the server instance _server_.
+The body content of the HTTP responses will contain the file contents of
+the file located at _path_, which should be an HTML file.
+
+The custom HTML content will be used when the server is returning an
+internally generated error response, or is returning an error response
+that was allocated with the
+`<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error()>>`
+function.
+This HTML content will also be used if the application calls the
+`<<nng_http_server_res_error.3http#,nng_http_server_res_error()>>`.
+The last custom error page set for _code_ by either this function or
+`<<nng_http_server_set_error_page.3http#,nng_http_server_error_page()>>`
+will be used.
+
+NOTE: Error responses that have their body content changed after allocation,
+or that are written directly by the application, will not use the body
+content supplied here.
+
+NOTE: The file contents of _path_ are read when this function is called.
+Therefore, if the file contents are changed, then this function should
+be called again to update the error page.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+[horizontal]
+`NNG_ENOENT`:: The file named by _path_ does not exist.
+`NNG_EPERM`:: No permission to read the file named by _path_.
+`NNG_ENOMEM`:: Insufficient free memory exists.
+`NNG_ENOTSUP`:: HTTP not supported.
+
+== SEE ALSO
+
+[.text-left]
+<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error(3http)>>,
+<<nng_http_server_hold.3http#,nng_http_server_hold(3http)>>,
+<<nng_http_server_res_error.3http#,nng_http_server_res_error(3http)>>,
+<<nng_http_server_set_error_page.3http#,nng_http_server_set_error_page(3http)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng.7#,nng(7)>>
diff --git a/docs/man/nng_http_server_set_error_page.3http.adoc b/docs/man/nng_http_server_set_error_page.3http.adoc
new file mode 100644
index 00000000..271b9d99
--- /dev/null
+++ b/docs/man/nng_http_server_set_error_page.3http.adoc
@@ -0,0 +1,69 @@
+= nng_http_server_set_error_page(3http)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nng_http_server_set_error_page - set custom HTTP error page
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+#include <nng/supplemental/http/http.h>
+
+int nng_http_server_set_error_page(nng_http_server *server,
+        uint16_t code, const char *html);
+----
+
+== DESCRIPTION
+
+The `nng_http_server_set_error_page()` sets an error page to be used
+for HTTP status _code_ on the server instance _server_.
+The body content of the HTTP responses will contain _html_.
+
+The custom HTML content will be used when the server is returning an
+internally generated error response, or is returning an error response
+that was allocated with the
+`<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error()>>`
+function.
+This HTML content will also be used if the application calls the
+`<<nng_http_server_res_error.3http#,nng_http_server_res_error()>>`.
+The last custom error page set for _code_ by either this function or
+`<<nng_http_server_set_error_file.3http#,nng_http_server_error_file()>>`
+will be used.
+
+NOTE: Error responses that have their body content changed after allocation,
+or that are written directly by the application, will not use the body
+content supplied here.
+
+The supplied HTML content is copied by this function, and may be reused
+after this function returns.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+[horizontal]
+`NNG_ENOMEM`:: Insufficient free memory exists.
+`NNG_ENOTSUP`:: HTTP not supported.
+
+== SEE ALSO
+
+[.text-left]
+<<nng_http_res_alloc_error.3http#,nng_http_res_alloc_error(3http)>>,
+<<nng_http_server_hold.3http#,nng_http_server_hold(3http)>>,
+<<nng_http_server_res_error.3http#,nng_http_server_res_error(3http)>>,
+<<nng_http_server_set_error_file.3http#,nng_http_server_set_error_file(3http)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng.7#,nng(7)>>