LittleFS: add overrides for Stream::send (#8386)

* littlefs: add overrides for Stream::send

cores/esp8266/FS.h

@@ -118,6 +118,18 @@ public:
     time_t getCreationTime();
     void setTimeCallback(time_t (*cb)(void));
 
+    // Stream::send configuration
+
+    bool inputCanTimeout () override {
+        // unavailable data can't become later available
+        return false;
+    }
+
+    bool outputCanTimeout () override {
+        // free space for write can't increase later
+        return false;
+    }
+
 protected:
     FileImplPtr _p;
     time_t (*_timeCallback)(void) = nullptr;

libraries/LittleFS/examples/SpeedTest/SpeedTest.ino

@@ -132,6 +132,16 @@ void DoTest(FS *fs) {
   f.close();
   stop = millis();
   Serial.printf("==> Time to read 64KB in 1b chunks = %lu milliseconds = %s\n", stop - start, rate(start, stop, 65536));
+
+
+  start = millis();
+  auto dest = fs->open("/test1bw.bin", "w");
+  f = fs->open("/test1b.bin", "r");
+  auto copysize = f.sendAll(dest);
+  dest.close();
+  stop = millis();
+  Serial.printf("==> Time to copy %d = %zd bytes = %lu milliseconds = %s\n", f.size(), copysize, stop - start, rate(start, stop, f.size()));
+  f.close();
 }
 
 void setup() {
@@ -139,6 +149,7 @@ void setup() {
   Serial.printf("Beginning test\n");
   Serial.flush();
   DoTest(&TESTFS);
+  Serial.println("done");
 }
 
 void loop() {

libraries/LittleFS/src/LittleFS.h

@@ -241,7 +241,7 @@ public:
                 DEBUGV("lfs_format, lfs_setattr 't': rc=%d\n", rc);
                 return false;
             }
-            
+
             lfs_unmount(&_lfs);
             _mounted = false;
         }
@@ -372,6 +372,30 @@ public:
         }
     }
 
+    int availableForWrite () override {
+        if (!_opened || !_fd) {
+            return 0;
+        }
+
+        const auto f = _getFD();
+        const auto fs = _fs->getFS();
+
+        // check for remaining size in current block
+        // ignore inline feature (per code in lfs_file_rawwrite())
+        auto afw = fs->cfg->block_size - f->off;
+
+        if (afw == 0) {
+            // current block is full
+            // check for filesystem full (per code in lfs_alloc())
+            if (!(fs->free.i == fs->free.size && fs->free.ack == 0)) {
+                // fs is not full, return a full sector as free space
+                afw = fs->cfg->block_size;
+            }
+        }
+
+        return afw;
+    }
+
     size_t write(const uint8_t *buf, size_t size) override {
         if (!_opened || !_fd || !buf) {
             return 0;