http keep alive

Give an example of how to implement http keep alive. This requires a
modified version of the lwip http client.

pico_w/wifi/http_client/CMakeLists.txt

@@ -1,9 +1,11 @@
+add_subdirectory(http_client_mod)
+
 pico_add_library(example_lwip_http_util NOFLAG)
 target_sources(example_lwip_http_util INTERFACE
         ${CMAKE_CURRENT_LIST_DIR}/example_http_client_util.c
         )
 pico_mirrored_target_link_libraries(example_lwip_http_util INTERFACE
-        pico_lwip_http
+        pico_lwip_http_client_mod
         pico_lwip_mbedtls
         pico_mbedtls
         )

pico_w/wifi/http_client/example_http_client_util.c

@@ -25,7 +25,7 @@
 
 #ifndef HTTP_DEBUG
 #ifdef NDEBUG
-#define HTTP_DEBUG
+#define HTTP_DEBUG(...)
 #else
 #define HTTP_DEBUG printf
 #endif
@@ -48,7 +48,7 @@ err_t http_client_header_print_fn(__unused httpc_state_t *connection, __unused v
 
 // Print body to stdout
 err_t http_client_receive_print_fn(__unused void *arg, __unused struct altcp_pcb *conn, struct pbuf *p, err_t err) {
-    HTTP_INFO("\ncontent err %d\n", err);
+    HTTP_INFO("\ncontent err %d len %u\n", err, p->tot_len);
     u16_t offset = 0;
     while (offset < p->tot_len) {
         char c = (char)pbuf_get_at(p, offset++);
@@ -71,20 +71,26 @@ static err_t internal_recv_fn(void *arg, struct altcp_pcb *conn, struct pbuf *p,
     assert(arg);
     EXAMPLE_HTTP_REQUEST_T *req = (EXAMPLE_HTTP_REQUEST_T*)arg;
     if (req->recv_fn) {
-        return req->recv_fn(req->callback_arg, conn, p, err);
+        req->recv_fn(req->callback_arg, conn, p, err);
     }
+    altcp_recved(conn, p->tot_len);
+    pbuf_free(p);
     return ERR_OK;
 }
 
-static void internal_result_fn(void *arg, httpc_result_t httpc_result, u32_t rx_content_len, u32_t srv_res, err_t err) {
+static int internal_result_fn(void *arg, httpc_result_t httpc_result, u32_t rx_content_len, u32_t srv_res, err_t err) {
+    int more = 0;
     assert(arg);
     EXAMPLE_HTTP_REQUEST_T *req = (EXAMPLE_HTTP_REQUEST_T*)arg;
     HTTP_DEBUG("result %d len %u server_response %u err %d\n", httpc_result, rx_content_len, srv_res, err);
-    req->complete = true;
     req->result = httpc_result;
     if (req->result_fn) {
-        req->result_fn(req->callback_arg, httpc_result, rx_content_len, srv_res, err);
+        more = req->result_fn(req->callback_arg, httpc_result, rx_content_len, srv_res, err);
     }
+    if (!more) {
+        req->complete = true;
+    }
+    return more;
 }
 
 // Override altcp_tls_alloc to set sni
@@ -118,7 +124,7 @@ int http_client_request_async(async_context_t *context, EXAMPLE_HTTP_REQUEST_T *
     req->settings.headers_done_fn = req->headers_fn ? internal_header_fn : NULL;
     req->settings.result_fn = internal_result_fn;
     async_context_acquire_lock_blocking(context);
-    err_t ret = httpc_get_file_dns(req->hostname, req->port ? req->port : default_port, req->url, &req->settings, internal_recv_fn, req, NULL);
+    err_t ret = httpc_get_file_dns(req->hostname, req->port ? req->port : default_port, req->url, &req->settings, internal_recv_fn, req, &req->connection);
     async_context_release_lock(context);
     if (ret != ERR_OK) {
         HTTP_ERROR("http request failed: %d", ret);

pico_w/wifi/http_client/example_http_client_util.h

@@ -7,7 +7,7 @@
 #ifndef EXAMPLE_HTTP_CLIENT_UTIL_H
 #define EXAMPLE_HTTP_CLIENT_UTIL_H
 
-#include "lwip/apps/http_client.h"
+#include "http_client_mod.h"
 
 /*! \brief Parameters used to make HTTP request
  *  \ingroup pico_lwip
@@ -33,6 +33,7 @@ typedef struct EXAMPLE_HTTP_REQUEST {
     altcp_recv_fn recv_fn;
     /*!
      * Function to callback with final results of the request, can be null
+     * @return true to keep the connection alive and make more requests
      * @see httpc_result_fn
      */
     httpc_result_fn result_fn;
@@ -51,7 +52,7 @@ typedef struct EXAMPLE_HTTP_REQUEST {
      */
     struct altcp_tls_config *tls_config;
     /*!
-     * TLS allocator, used internall for setting TLS server name indication
+     * TLS allocator, used internally for setting TLS server name indication
      */
     altcp_allocator_t tls_allocator;
 #endif
@@ -64,10 +65,13 @@ typedef struct EXAMPLE_HTTP_REQUEST {
      */
     int complete;
     /*!
-     * Overall result of http request, only valid when complete is set
+     * Overall result of http request
      */
     httpc_result_t result;
-
+    /*!
+     * Gets a pointer to internal http client
+     */
+    httpc_state_t *connection;
 } EXAMPLE_HTTP_REQUEST_T;
 
 struct async_context;

pico_w/wifi/http_client/http_client_mod/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Modified version of LwIP http client
+pico_add_library(pico_lwip_http_client_mod NOFLAG)
+target_include_directories(pico_lwip_http_client_mod INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}
+        )
+target_sources(pico_lwip_http_client_mod INTERFACE
+    ${PICO_LWIP_PATH}/src/apps/http/altcp_proxyconnect.c
+    ${CMAKE_CURRENT_LIST_DIR}/http_client_mod.c
+    )