fix performance and memory usage of creating blob on Android (facebook#50121)

Summary:
This PR fixes facebook#48657
- Memory usage for creating a blob lowered from _( nearest 2^N greater than the file size)+1KB_ previously To _(file size)+1KB_. This is achieved by avoiding internal calls to java.io.ByteArrayOutputStream.ensureCapacity by creating a buffer based on file size.
- Increases the max file size a Blob can be  created from before hitting a OutOfMemoryException.
- Major performance increase by avoiding buffer copying

## Changelog:

[ANDROID] [CHANGED] - Speed and Memory usage improvements to Android Blob support
[ANDROID] [FIXED] - Creating of Blobs from large files now works. File size can now be upto available (free) heap size.

Pull Request resolved: facebook#50121

Test Plan: Used the App here to test Android Blob creation. https://github.com/giantslogik/blob-large-file-fetch.

Reviewed By: cortinico

Differential Revision: D71464835

Pulled By: javache

fbshipit-source-id: 38de7d83bcaee265fc6e7183f6b1160027cd4cb2

Author: giantslogik

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/blob/BlobModule.java

@@ -231,14 +231,40 @@ private byte[] getBytesFromUri(Uri contentUri) throws IOException {
       throw new FileNotFoundException("File not found for " + contentUri);
     }
 
-    ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
-    int bufferSize = 1024;
-    byte[] buffer = new byte[bufferSize];
-    int len;
-    while ((len = is.read(buffer)) != -1) {
-      byteBuffer.write(buffer, 0, len);
+    try {
+      // Allocate a buffer upto the number of bytes that can be read without blocking
+      // available() typically returns the file size if the uri represents an underlying file (i.e.
+      // is instanceof FileInputStream)
+      byte[] buffer =
+          new byte
+              [Math.max(
+                  1024,
+                  is.available())]; // fallback to 1024 if available returns 0 or a small size.
+      int len;
+      byte[] prevBuffer = new byte[1024];
+      int prevLen = 0;
+
+      ByteArrayOutputStream byteBuffer = new ByteArrayOutputStream();
+      while ((len = is.read(buffer)) != -1) {
+        // this performs a no-op on the first iteration of while. prevLen is zero
+        byteBuffer.write(prevBuffer, 0, prevLen);
+        // swap buffers.
+        byte[] temp = prevBuffer;
+        prevBuffer = buffer;
+        buffer = temp;
+        // set prevLen = length of data in prevBuffer
+        prevLen = len;
+      }
+
+      if (byteBuffer.size() == 0 && prevBuffer.length == prevLen) {
+        // If EOF AND prevBuffer contains entire stream avoid using ByteArrayOutputStream
+        return prevBuffer;
+      }
+      byteBuffer.write(prevBuffer, 0, prevLen);
+      return byteBuffer.toByteArray();
+    } finally {
+      is.close();
     }
-    return byteBuffer.toByteArray();
   }
 
   private String getNameFromUri(Uri contentUri) {