Honor buffer.byteOffset in read/write for nodefs

This change started out by adding buffer.byteOffset to offset (hence the
description) but ended by just getting rid of the additional array view.
Digging through the history, it seems that may have originated from the
original code, when the node.js fs APIs didn't accept a TypedArray -
just a node Buffer instance

Author: inolen

src/lib/libnodefs.js

@@ -272,12 +272,12 @@ addToLibrary({
       },
       read(stream, buffer, offset, length, position) {
         return NODEFS.tryFSOperation(() =>
-          fs.readSync(stream.nfd, new Int8Array(buffer.buffer, offset, length), 0, length, position)
+          fs.readSync(stream.nfd, buffer, offset, length, position)
         );
       },
       write(stream, buffer, offset, length, position) {
         return NODEFS.tryFSOperation(() =>
-          fs.writeSync(stream.nfd, new Int8Array(buffer.buffer, offset, length), 0, length, position)
+          fs.writeSync(stream.nfd, buffer, offset, length, position)
         );
       },
       llseek(stream, offset, whence) {

src/lib/libnoderawfs.js

@@ -207,7 +207,7 @@ addToLibrary({
       }
       var seeking = typeof position != 'undefined';
       if (!seeking && stream.seekable) position = stream.position;
-      var bytesRead = fs.readSync(stream.nfd, new Int8Array(buffer.buffer, offset, length), 0, length, position);
+      var bytesRead = fs.readSync(stream.nfd, buffer, offset, length, position);
       // update position marker when non-seeking
       if (!seeking) stream.position += bytesRead;
       return bytesRead;
@@ -223,7 +223,7 @@ addToLibrary({
       }
       var seeking = typeof position != 'undefined';
       if (!seeking && stream.seekable) position = stream.position;
-      var bytesWritten = fs.writeSync(stream.nfd, new Int8Array(buffer.buffer, offset, length), 0, length, position);
+      var bytesWritten = fs.writeSync(stream.nfd, buffer, offset, length, position);
       // update position marker when non-seeking
       if (!seeking) stream.position += bytesWritten;
       return bytesWritten;

test/fs/test_writeFile.cpp

@@ -8,16 +8,18 @@
 
 int main() {
   EM_ASM(
+    const buf = Uint8Array.from('c=3\nd=4\ne=5', x => x.charCodeAt(0));
     FS.writeFile("testfile", "a=1\nb=2\n");
-    FS.writeFile("testfile", new Uint8Array([99, 61, 51]) /* c=3 */, { flags: "a" });
+    FS.writeFile("testfile", buf.subarray(4, 7) /* d=4 */, { flags: "a" });
   );
 
   std::ifstream file("testfile");
 
   while (!file.eof() && !file.fail()) {
     std::string line;
     getline(file, line);
-    std::string name;
+    std::string key;
+    std::string val;
 
     std::cout << "read " << line << std::endl;
 
@@ -35,7 +37,10 @@ int main() {
         continue;
     }
 
-    name = line.substr(0, equalsPos);
+    key = line.substr(0, equalsPos);
+    val = line.substr(equalsPos + 1);
+
+    std::cout << "parsed " << key << "=" << val << std::endl;
   }
 
   return 0;

test/fs/test_writeFile.out

@@ -1,3 +1,6 @@
 read a=1
+parsed a=1
 read b=2
-read c=3
+parsed b=2
+read d=4
+parsed d=4