added OTA Update S3 example with a sample bin (espressif#445)

* added OTA Update S3 example with a sample bin

* Update as per comments

Author: arvindr21

libraries/Update/examples/AWS_S3_OTA_Update/AWS_S3_OTA_Update.ino

@@ -0,0 +1,276 @@
+/**
+   AWS S3 OTA Update
+   Date: 14th June 2017
+   Author: Arvind Ravulavaru <https://github.com/arvindr21>
+   Purpose: Perform an OTA update from a bin located in Amazon S3 (HTTP Only)
+
+   Upload:
+   Step 1 : Download the sample bin file from the examples folder
+   Step 2 : Upload it to your Amazon S3 account, in a bucket of your choice
+   Step 3 : Once uploaded, inside S3, select the bin file >> More (button on top of the file list) >> Make Public
+   Step 4 : You S3 URL => http://bucket-name.s3.ap-south-1.amazonaws.com/sketch-name.ino.bin
+   Step 5 : Build the above URL and fire it either in your browser or curl it `curl -I -v http://bucket-name.ap-south-1.amazonaws.com/sketch-name.ino.bin` to validate the same
+   Step 6:  Plug in your SSID, Password, S3 Host and Bin file below
+
+   Build & upload
+   Step 1 : Menu > Sketch > Export Compiled Library. The bin file will be saved in the sketch folder (Menu > Sketch > Show Sketch folder)
+   Step 2 : Upload bin to S3 and continue the above process
+
+   // Check the bottom of this sketch for sample serial monitor log, during and after successful OTA Update
+*/
+
+#include <WiFi.h>
+#include <Update.h>
+
+WiFiClient client;
+
+// Variables to validate
+// response from S3
+int contentLength = 0;
+bool isValidContentType = false;
+
+// Your SSID and PSWD that the chip needs
+// to connect to
+char* SSID = "YOUR-SSID";
+char* PSWD = "YOUR-SSID-PSWD";
+
+// S3 Bucket Config
+String host = "bucket-name.s3.ap-south-1.amazonaws.com"; // Host => bucket-name.s3.region.amazonaws.com
+int port = 80; // Non https. For HTTPS 443. As of today, HTTPS doesn't work.
+String bin = "/sketch-name.ino.bin"; // bin file name with a slash in front.
+
+// Utility to extract header value from headers
+String getHeaderValue(String header, String headerName) {
+  return header.substring(strlen(headerName.c_str()));
+}
+
+// OTA Logic 
+void execOTA() {
+  Serial.println("Connecting to: " + String(host));
+  // Connect to S3
+  if (client.connect(host.c_str(), port)) {
+    // Connection Succeed.
+    // Fecthing the bin
+    Serial.println("Fetching Bin: " + String(bin));
+
+    // Get the contents of the bin file
+    client.print(String("GET ") + bin + " HTTP/1.1\r\n" +
+                 "Host: " + host + "\r\n" +
+                 "Cache-Control: no-cache\r\n" +
+                 "Connection: close\r\n\r\n");
+
+    // Check what is being sent
+    //    Serial.print(String("GET ") + bin + " HTTP/1.1\r\n" +
+    //                 "Host: " + host + "\r\n" +
+    //                 "Cache-Control: no-cache\r\n" +
+    //                 "Connection: close\r\n\r\n");
+
+    delay(100);
+    // Once the response is available,
+    // check stuff
+
+    /*
+       Response Structure
+        HTTP/1.1 200 OK
+        x-amz-id-2: NVKxnU1aIQMmpGKhSwpCBh8y2JPbak18QLIfE+OiUDOos+7UftZKjtCFqrwsGOZRN5Zee0jpTd0=
+        x-amz-request-id: 2D56B47560B764EC
+        Date: Wed, 14 Jun 2017 03:33:59 GMT
+        Last-Modified: Fri, 02 Jun 2017 14:50:11 GMT
+        ETag: "d2afebbaaebc38cd669ce36727152af9"
+        Accept-Ranges: bytes
+        Content-Type: application/octet-stream
+        Content-Length: 357280
+        Server: AmazonS3
+                                   
+        {{BIN FILE CONTENTS}}
+
+    */
+    while (client.available()) {
+      // read line till /n
+      String line = client.readStringUntil('\n');
+      // remove space, to check if the line is end of headers
+      line.trim();
+
+      // if the the line is empty,
+      // this is end of headers
+      // break the while and feed the
+      // remaining `client` to the
+      // Update.writeStream();
+      if (!line.length()) {
+        //headers ended
+        break; // and get the OTA started
+      }
+
+      // Check if the HTTP Response is 200
+      // else break and Exit Update
+      if (line.startsWith("HTTP/1.1")) {
+        if (line.indexOf("200") < 0) {
+          Serial.println("Got a non 200 status code from server. Exiting OTA Update.");
+          break;
+        }
+      }
+
+      // extract headers here
+      // Start with content length
+      if (line.startsWith("Content-Length: ")) {
+        contentLength = atoi((getHeaderValue(line, "Content-Length: ")).c_str());
+        Serial.println("Got " + String(contentLength) + " bytes from server");
+      }
+
+      // Next, the content type
+      if (line.startsWith("Content-Type: ")) {
+        String contentType = getHeaderValue(line, "Content-Type: ");
+        Serial.println("Got " + contentType + " payload.");
+        if (contentType == "application/octet-stream") {
+          isValidContentType = true;
+        }
+      }
+    }
+  } else {
+    // Connect to S3 failed
+    // May be try?
+    // Probably a choppy network?
+    Serial.println("Connection to " + String(host) + " failed. Please check your setup");
+    // retry??
+    // execOTA();
+  }
+
+  // Check what is the contentLength and if content type is `application/octet-stream`
+  Serial.println("contentLength : " + String(contentLength) + ", isValidContentType : " + String(isValidContentType));
+
+  // check contentLength and content type
+  if (contentLength && isValidContentType) {
+    // Check if there is enough to OTA Update
+    bool canBegin = Update.begin(contentLength);
+
+    // If yes, begin
+    if (canBegin) {
+      Serial.println("Begin OTA. This may take 2 - 5 mins to complete. Things might be quite for a while.. Patience!");
+      // No activity would appear on the Serial monitor
+      // So be patient. This may take 2 - 5mins to complete
+      size_t written = Update.writeStream(client);
+
+      if (written == contentLength) {
+        Serial.println("Written : " + String(written) + " successfully");
+      } else {
+        Serial.println("Written only : " + String(written) + "/" + String(contentLength) + ". Retry?" );
+        // retry??
+        // execOTA();
+      }
+
+      if (Update.end()) {
+        Serial.println("OTA done!");
+        if (Update.isFinished()) {
+          Serial.println("Update successfully completed. Rebooting.");
+          ESP.restart();
+        } else {
+          Serial.println("Update not finished? Something went wrong!");
+        }
+      } else {
+        Serial.println("Error Occurred. Error #: " + String(Update.getError()));
+      }
+    } else {
+      // not enough space to begin OTA
+      // Understand the partitions and
+      // space availability
+      Serial.println("Not enough space to begin OTA");
+      client.flush();
+    }
+  } else {
+    Serial.println("There was no content in the response");
+    client.flush();
+  }
+}
+
+void setup() {
+  //Begin Serial
+  Serial.begin(115200);
+  delay(10);
+
+  Serial.println("Connecting to " + String(SSID));
+
+  // Connect to provided SSID and PSWD
+  WiFi.begin(SSID, PSWD);
+
+  // Wait for connection to establish
+  while (WiFi.status() != WL_CONNECTED) {
+    Serial.print("."); // Keep the serial monitor lit!
+    delay(500);
+  }
+
+  // Connection Succeed
+  Serial.println("");
+  Serial.println("Connected to " + String(SSID));
+
+  // Execute OTA Update
+  execOTA();
+}
+
+void loop() {
+  // chill
+}
+
+/*
+ * Serial Monitor log for this sketch
+ * 
+ * If the OTA succeeded, it would load the preference sketch, with a small modification. i.e.
+ * Print `OTA Update succeeded!! This is an example sketch : Preferences > StartCounter`
+ * And then keeps on restarting every 10 seconds, updating the preferences
+ * 
+ * 
+      rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
+      configsip: 0, SPIWP:0x00
+      clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
+      mode:DIO, clock div:1
+      load:0x3fff0008,len:8
+      load:0x3fff0010,len:160
+      load:0x40078000,len:10632
+      load:0x40080000,len:252
+      entry 0x40080034
+      Connecting to SSID
+      ......
+      Connected to SSID
+      Connecting to: bucket-name.s3.ap-south-1.amazonaws.com
+      Fetching Bin: /StartCounter.ino.bin
+      Got application/octet-stream payload.
+      Got 357280 bytes from server
+      contentLength : 357280, isValidContentType : 1
+      Begin OTA. This may take 2 - 5 mins to complete. Things might be quite for a while.. Patience!
+      Written : 357280 successfully
+      OTA done!
+      Update successfully completed. Rebooting.
+      ets Jun  8 2016 00:22:57
+      
+      rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
+      configsip: 0, SPIWP:0x00
+      clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
+      mode:DIO, clock div:1
+      load:0x3fff0008,len:8
+      load:0x3fff0010,len:160
+      load:0x40078000,len:10632
+      load:0x40080000,len:252
+      entry 0x40080034
+      
+      OTA Update succeeded!! This is an example sketch : Preferences > StartCounter
+      Current counter value: 1
+      Restarting in 10 seconds...
+      E (102534) wifi: esp_wifi_stop 802 wifi is not init
+      ets Jun  8 2016 00:22:57
+      
+      rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
+      configsip: 0, SPIWP:0x00
+      clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
+      mode:DIO, clock div:1
+      load:0x3fff0008,len:8
+      load:0x3fff0010,len:160
+      load:0x40078000,len:10632
+      load:0x40080000,len:252
+      entry 0x40080034
+      
+      OTA Update succeeded!! This is an example sketch : Preferences > StartCounter
+      Current counter value: 2
+      Restarting in 10 seconds...
+
+      ....
+ * 
+ */