Allow E.pipe to pipe from Strings, remove pipe's internal position …

…counter (fix #2352)

ChangeLog

@@ -45,6 +45,7 @@
             Bangle.js2: Ensure `HRM-raw.raw` is set correctly after we moved to binary hrm algorithm
             nRF5x: Add `NRF.on("passkey", ...)` to allow passkey pairing with `NRF.setSecurity({mitm:1, display:1});`
             nrf52: Allow disabling pairing with `NRF.setSecurity({pair:0})`
+            Allow E.pipe to pipe from Strings, remove pipe's internal `position` counter (fix #2352)
 
      2v18 : Fix drawString with setClipRect with 90/270-degree rotation (fix #2343)
             Pico/Wifi: Enabled JIT compiler

src/jswrap_espruino.c

@@ -777,12 +777,44 @@ their values.
   "ifndef" : "SAVE_ON_FLASH",
   "generate" : "jswrap_pipe",
   "params" : [
-    ["source","JsVar","The source file/stream that will send content."],
+    ["source","JsVar","The source file/stream that will send content. As of 2v19 this can also be a `String`"],
     ["destination","JsVar","The destination file/stream that will receive content from the source."],
     ["options","JsVar",["[optional] An object `{ chunkSize : int=64, end : bool=true, complete : function }`","chunkSize : The amount of data to pipe from source to destination at a time","complete : a function to call when the pipe activity is complete","end : call the 'end' function on the destination when the source is finished"]]
   ],
   "typescript" : "pipe(source: any, destination: any, options?: PipeOptions): void"
-}*/
+}
+Pipe one stream to another.
+
+This can be given any object with a `read` method as a source, and any object with a `.write(data)` method as a destination.
+
+Data will be piped from `source` to `destination` in the idle loop until `source.read(...)` returns `undefined`.
+
+For instance:
+
+```
+// Print a really big string to the console, 1 character at a time and write 'Finished!' at the end
+E.pipe("This is a really big String",
+       {write: print},
+       {chunkSize:1, complete:()=>print("Finished!")});
+
+// Pipe the numbers 1 to 100 to a StorageFile in Storage
+E.pipe({ n:0, read : function() { if (this.n<100) return (this.n++)+"\n"; }},
+       require("Storage").open("testfile","w"));
+
+// Pipe a StorageFile straight to the Bluetooth UART
+E.pipe(require("Storage").open("testfile","r"), Bluetooth);
+
+// Pipe a normal file in Storage (not StorageFile) straight to the Bluetooth UART
+E.pipe(require("Storage").read("blob.txt"), Bluetooth);
+
+// Pipe a normal file in Storage as a response to an HTTP request
+function onPageRequest(req, res) {
+  res.writeHead(200, {'Content-Type': 'text/plain'});
+  E.pipe(require("Storage").read("webpage.txt"), res);
+}
+require("http").createServer(onPageRequest).listen(80);
+```
+*/
 
 /*JSON{
   "type" : "staticmethod",

src/jswrap_pipe.c

@@ -52,10 +52,6 @@ static void handlePipeClose(JsVar *arr, JsvObjectIterator *it, JsVar* pipe) {
         jsvUnLock(jspExecuteFunction(writeFunc, destination, 1, &buffer));
       }
       jsvUnLock(writeFunc);
-      // update position
-      JsVar *position = jsvObjectGetChildIfExists(pipe,"position");
-      jsvSetInteger(position, jsvGetInteger(position) + (JsVarInt)jsvGetStringLength(buffer));
-      jsvUnLock(position);
     }
     jsvUnLock(buffer);
   }
@@ -104,13 +100,12 @@ static bool handlePipe(JsVar *arr, JsvObjectIterator *it, JsVar* pipe) {
   bool paused = jsvGetBoolAndUnLock(jsvObjectGetChildIfExists(pipe,"drainWait"));
   if (paused) return false;
 
-  JsVar *position = jsvObjectGetChildIfExists(pipe,"position");
   JsVar *chunkSize = jsvObjectGetChildIfExists(pipe,"chunkSize");
   JsVar *source = jsvObjectGetChildIfExists(pipe,"source");
   JsVar *destination = jsvObjectGetChildIfExists(pipe,"destination");
 
   bool dataTransferred = false;
-  if(source && destination && chunkSize && position) {
+  if(source && destination && chunkSize) {
     JsVar *readFunc = jspGetNamedField(source, "read", false);
     JsVar *writeFunc = jspGetNamedField(destination, "write", false);
     if (jsvIsFunction(readFunc) && jsvIsFunction(writeFunc)) { // do the objects have the necessary methods on them?
@@ -124,7 +119,6 @@ static bool handlePipe(JsVar *arr, JsvObjectIterator *it, JsVar* pipe) {
             jsvObjectSetChildAndUnLock(pipe,"drainWait",jsvNewFromBool(true));
           }
           jsvUnLock(response);
-          jsvSetInteger(position, jsvGetInteger(position) + bufferSize);
         }
         jsvUnLock(buffer);
         dataTransferred = true; // so we don't close the pipe if we get an empty string
@@ -142,7 +136,6 @@ static bool handlePipe(JsVar *arr, JsvObjectIterator *it, JsVar* pipe) {
     handlePipeClose(arr, it, pipe);
   }
   jsvUnLock3(source, destination, chunkSize);
-  jsvUnLock(position);
   return dataTransferred;
 }
 
@@ -256,13 +249,20 @@ type PipeOptions = {
     ["options","JsVar",["[optional] An object `{ chunkSize : int=64, end : bool=true, complete : function }`","chunkSize : The amount of data to pipe from source to destination at a time","complete : a function to call when the pipe activity is complete","end : call the 'end' function on the destination when the source is finished"]]
   ],
   "typescript": "pipe(destination: any, options?: PipeOptions): void"
-}*/
+}
+Pipe this file to a destination stream (object which has a `.write(data)` method).
+*/
 void jswrap_pipe(JsVar* source, JsVar* dest, JsVar* options) {
   if (!source || !dest) return;
+  jsvLockAgain(source); // source should be unlocked at end
   JsVar *pipe = jspNewObject(0, "Pipe");
   JsVar *arr = pipeGetArray(true);
-  JsVar* position = jsvNewFromInteger(0);
-  if (pipe && arr && position) {// out of memory?
+  if (pipe && arr) {// out of memory?
+    if (jsvIsString(source)) { // Single-line 'StringStream' object to add ability to stream from Strings
+      JsVar *stream = jspExecuteJSFunction("(function(s){var p=0;return{read:function(l){return s.substring(p,p+=l)||undefined;}}})",NULL,1,&source);
+      jsvUnLock(source);
+      source = stream;
+    }
     JsVar *readFunc = jspGetNamedField(source, "read", false);
     JsVar *writeFunc = jspGetNamedField(dest, "write", false);
     if(jsvIsFunction(readFunc)) {
@@ -297,19 +297,18 @@ void jswrap_pipe(JsVar* source, JsVar* dest, JsVar* options) {
         // set up the rest of the pipe
         jsvObjectSetChildAndUnLock(pipe, "chunkSize", jsvNewFromInteger(chunkSize));
         jsvObjectSetChildAndUnLock(pipe, "end", jsvNewFromBool(callEnd));
-        jsvUnLock3(jsvAddNamedChild(pipe, position, "position"), 
-                   jsvAddNamedChild(pipe, source, "source"), 
+        jsvUnLock2(jsvAddNamedChild(pipe, source, "source"),
                    jsvAddNamedChild(pipe, dest, "destination"));
         // add the pipe to our list
         jsvArrayPush(arr, pipe);
       } else {
-        jsExceptionHere(JSET_ERROR, "Destination object does not implement the required write(buffer, length, position) method.");
+        jsExceptionHere(JSET_ERROR, "Destination object does not implement the required write(buffer, length) method.");
       }
     } else {
-      jsExceptionHere(JSET_ERROR, "Source object does not implement the required read(buffer, length, position) method.");
+      jsExceptionHere(JSET_ERROR, "Source object does not implement the required read(buffer, length) method.");
     }
     jsvUnLock2(readFunc, writeFunc);
   }
-  jsvUnLock3(arr, pipe, position);
+  jsvUnLock3(arr, pipe, source);
 }