Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/docs/libcurl/curl_pushheader_byname.md

@@ -0,0 +1,85 @@
+---
+c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+SPDX-License-Identifier: curl
+Title: curl_pushheader_byname
+Section: 3
+Source: libcurl
+See-also:
+  - CURLMOPT_PUSHFUNCTION (3)
+  - curl_pushheader_bynum (3)
+Protocol:
+  - HTTP
+Added-in: 7.44.0
+---
+
+# NAME
+
+curl_pushheader_byname - get a push header by name
+
+# SYNOPSIS
+
+~~~c
+#include <curl/curl.h>
+
+char *curl_pushheader_byname(struct curl_pushheaders *h, const char *name);
+~~~
+
+# DESCRIPTION
+
+This is a function that is only functional within a
+CURLMOPT_PUSHFUNCTION(3) callback. It makes no sense to try to use it
+elsewhere and it has no function then.
+
+It returns the value for the given header field name (or NULL) for the
+incoming server push request. This is a shortcut so that the application does
+not have to loop through all headers to find the one it is interested in. The
+data this function points to is freed when this callback returns. If more than
+one header field use the same name, this returns only the first one.
+
+# %PROTOCOLS%
+
+# EXAMPLE
+
+~~~c
+#include <string.h> /* for strncmp */
+
+static int push_cb(CURL *parent,
+                   CURL *easy,
+                   size_t num_headers,
+                   struct curl_pushheaders *headers,
+                   void *clientp)
+{
+  char *headp;
+  int *transfers = (int *)clientp;
+  FILE *out;
+  headp = curl_pushheader_byname(headers, ":path");
+  if(headp && !strncmp(headp, "/push-", 6)) {
+    fprintf(stderr, "The PATH is %s\n", headp);
+
+    /* save the push here */
+    out = fopen("pushed-stream", "wb");
+
+    /* write to this file */
+    curl_easy_setopt(easy, CURLOPT_WRITEDATA, out);
+
+    (*transfers)++; /* one more */
+
+    return CURL_PUSH_OK;
+  }
+  return CURL_PUSH_DENY;
+}
+
+int main(void)
+{
+  int counter;
+  CURLM *multi = curl_multi_init();
+  curl_multi_setopt(multi, CURLMOPT_PUSHFUNCTION, push_cb);
+  curl_multi_setopt(multi, CURLMOPT_PUSHDATA, &counter);
+}
+~~~
+
+# %AVAILABILITY%
+
+# RETURN VALUE
+
+Returns a pointer to the header field content or NULL.