Add command line parameter --no-heap-copy that optimizes for small memory footprint and fread() performance over the default behavior that copied VFS to HEAP, that is designed for mmap() performance.

Adjust MEMFS node contentMode enum to reflect whether content is off the main HEAP or not. Note that this enum is not much used, so this has little effect. Add browser tests to check that fread() and mmap() work with and without --no-heap-copy.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/library_memfs.js b/src/library_memfs.js
index 9f528108..d3148d8b 100644
--- a/src/library_memfs.js
+++ b/src/library_memfs.js
@@ -225,9 +225,9 @@ mergeInto(LibraryManager.library, {
 #if ASSERTIONS
           assert(buffer.length);
 #endif
-          if (canOwn && buffer.buffer === HEAP8.buffer && offset === 0) {
-            node.contents = buffer; // this is a subarray of the heap, and we can own it
-            node.contentMode = MEMFS.CONTENT_OWNING;
+          if (canOwn && offset === 0) {
+            node.contents = buffer; // this could be a subarray of Emscripten HEAP, or allocated from some other source.
+            node.contentMode = (buffer.buffer === HEAP8.buffer) ? MEMFS.CONTENT_OWNING : MEMFS.CONTENT_FIXED;
           } else {
             node.contents = new Uint8Array(buffer.subarray(offset, offset+length));
             node.contentMode = MEMFS.CONTENT_FIXED;