sketch of http client

system/include/gsm/http_client.h

@@ -0,0 +1,24 @@
+/*
+ * http_client.h
+ *
+ *  Created on: Mar 10, 2022
+ *      Author: mateusz
+ */
+
+#ifndef INCLUDE_GSM_HTTP_CLIENT_H_
+#define INCLUDE_GSM_HTTP_CLIENT_H_
+
+#include "gsm/sim800c.h"
+
+#define HTTP_CLIENT_OK					0
+#define HTTP_CLIENT_TIMEOUT				-100
+#define HTTP_CLIENT_TOO_LONG_RESPONSE	-110
+
+void http_client_init(gsm_sim800_state_t * state, srl_context_t * serial_context);
+uint8_t http_client_async_get(char * url, uint8_t url_ln, uint16_t response_ln_limit);
+uint8_t http_client_async_post(char * url, uint8_t url_ln, char * data_to_post, uint8_t data_ln);
+
+char * http_client_get_server_response();
+uint16_t http_client_get_latest_http_code();
+
+#endif /* INCLUDE_GSM_HTTP_CLIENT_H_ */

system/src/gsm/http_client.c

@@ -0,0 +1,107 @@
+#include "gsm/http_client.h"
+
+#include <string.h>
+
+static const char * DISCONNECTED 			= "CLOSED\0";
+static const char * CONTENT_LN				= "Content-Length: \0";
+
+#define WAIT_FOR_CONTENT_LENGHT		0xFFFFu
+
+/**
+ * Content lenght received from HTTP response headers
+ */
+uint16_t http_client_content_lenght = 0;
+
+/**
+ *	HTTP code returned by the latest query. It is zeroed after each successful call to async
+ *	function. This indicate that a request is currently in progress. Negative values means some
+ *	non HTTP error, like communication timeout or response longer than expected
+ */
+int16_t http_client_http_code = 0;
+
+/**
+ * Temporary buffer for processing
+ */
+static char http_client_header_buffer[32];
+
+/**
+ * Index used to walk through 'http_client_header_buffer'
+ */
+static uint8_t http_client_header_index = 0;
+
+/**
+ * This static function is used as a termination callback for serial I/O with GPRS module.
+ * It ends transmission in one of three cases
+ * 	1. All data is received according to size specified by Content-Lenght field in response header
+ * 	2. If user set 'response_ln_limit' to non zero value and 'response_ln_limit' characters have been received (it also set HTTP_CLIENT_TOO_LONG_RESPONSE)
+ * 	3. If connection has been closed by remote server
+ *
+ */
+static uint8_t http_client_rx_done_callback(uint8_t current_data, const uint8_t * const rx_buffer, uint16_t rx_bytes_counter) {
+
+	uint8_t out = 0;
+
+	int compare_result = 0;
+
+	// check if we wait for content lenght
+	if (http_client_content_lenght == WAIT_FOR_CONTENT_LENGHT) {
+		// copy current character to temporary buffer
+		http_client_header_buffer[http_client_header_index++] = (char)current_data;
+
+		// check if
+		if (current_data == '\r') {
+
+		}
+	}
+
+	// if this is maybe the last character of 'CLOSED'
+	if ((char)current_data == 'D') {
+		// check 6 previous characters
+		compare_result = strncmp(DISCONNECTED, (const char *) (rx_buffer + rx_bytes_counter - 6), 6);
+
+		// terminate reception if 'CLOSED' has been found.
+		if (compare_result == 0) {
+			out = 1;
+		}
+	}
+
+	// if this is maybe an end of content lenght
+	else if (http_client_content_lenght == 0 && (char)current_data == 'h') {
+		// check 14 previous characters
+		compare_result = strncmp(CONTENT_LN, rx_buffer + rx_bytes_counter - 14, 14);
+
+		// terminate reception if 'CLOSED' has been found.
+		if (compare_result == 0) {
+			// set waiting for
+			http_client_content_lenght = WAIT_FOR_CONTENT_LENGHT;
+
+			// clear the buffer where header value will be stored
+			memset (http_client_header_buffer, 0x00, sizeof(http_client_header_buffer));
+		}
+	}
+
+	return out;
+}
+
+
+void http_client_init(gsm_sim800_state_t * state, srl_context_t * serial_context) {
+
+}
+
+
+uint8_t http_client_async_get(char * url, uint8_t url_ln, uint16_t response_ln_limit) {
+	return 0;
+}
+
+uint8_t http_client_async_post(char * url, uint8_t url_ln, char * data_to_post, uint8_t data_ln) {
+	return 0;
+}
+
+
+char * http_client_get_server_response() {
+	return 0;
+}
+
+uint16_t http_client_get_latest_http_code() {
+	return http_client_http_code;
+}