Send HTTP headers to payload callback

Even if libweb already parses some common headers, such as
Content-Length, some users might find it interesting to inspect which
headers were received from a request.

Since HTTP/1.1 does not define a limit on the number of maximum headers
a client can send, for security reasons a maximum value must be provided
by the user. Any extra headers shall be then discarded by libweb.

An example application showing this new feature is also provided.

1 files changed, 81 insertions, 0 deletions

diff --git a/examples/headers/main.c b/examples/headers/main.c
new file mode 100644
index 0000000..b465aa1
--- /dev/null
+++ b/examples/headers/main.c
@@ -0,0 +1,81 @@
+#include <dynstr.h>
+#include <libweb/handler.h>
+#include <libweb/html.h>
+#include <libweb/http.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static const size_t max_headers = 5;
+
+static int hello(const struct http_payload *const pl,
+    struct http_response *const r, void *const user)
+{
+    printf("Got %zu headers from the client (max %zu).\n",
+        pl->n_headers, max_headers);
+
+    for (size_t i = 0; i < pl->n_headers; i++)
+    {
+        const struct http_header *const h = &pl->headers[i];
+
+        printf("%s: %s\n", h->header, h->value);
+    }
+
+    *r = (const struct http_response)
+    {
+        .status = HTTP_STATUS_OK
+    };
+
+    return 0;
+}
+
+static int on_length(const unsigned long long len,
+    const struct http_cookie *const c, struct http_response *const r,
+    void *const user)
+{
+    *r = (const struct http_response)
+    {
+        .status = HTTP_STATUS_FORBIDDEN
+    };
+
+    return 1;
+}
+
+int main(int argc, char *argv[])
+{
+    int ret = EXIT_FAILURE;
+    const short port = 8080;
+    const struct handler_cfg cfg =
+    {
+        .length = on_length,
+        .max_headers = max_headers
+    };
+
+    struct handler *const h = handler_alloc(&cfg);
+    static const char *const urls[] = {"/", "/index.html"};
+
+    if (!h)
+    {
+        fprintf(stderr, "%s: handler_alloc failed\n", __func__);
+        goto end;
+    }
+
+    for (size_t i = 0; i < sizeof urls / sizeof *urls; i++)
+        if (handler_add(h, urls[i], HTTP_OP_GET, hello, NULL))
+        {
+            fprintf(stderr, "%s: handler_add failed\n", __func__);
+            goto end;
+        }
+
+    if (handler_listen(h, port))
+    {
+        fprintf(stderr, "%s: handler_listen failed\n", __func__);
+        goto end;
+    }
+
+    ret = EXIT_SUCCESS;
+
+end:
+    handler_free(h);
+    return ret;
+}