Add formatFileSize utility function - human readable byte sizes

packages/react-native/Libraries/Utilities/__tests__/formatFileSize-test.js

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+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import formatFileSize from '../formatFileSize';
+
+describe('formatFileSize', () => {
+  it('formats zero bytes', () => {
+    expect(formatFileSize(0)).toEqual('0 Bytes');
+  });
+
+  it('formats bytes less than 1 KB', () => {
+    expect(formatFileSize(512)).toEqual('512.00 Bytes');
+    expect(formatFileSize(1023)).toEqual('1023.00 Bytes');
+  });
+
+  it('formats kilobytes', () => {
+    expect(formatFileSize(1024)).toEqual('1.00 KB');
+    expect(formatFileSize(1536)).toEqual('1.50 KB');
+    expect(formatFileSize(2048)).toEqual('2.00 KB');
+  });
+
+  it('formats megabytes', () => {
+    expect(formatFileSize(1048576)).toEqual('1.00 MB');
+    expect(formatFileSize(1572864)).toEqual('1.50 MB');
+    expect(formatFileSize(2097152)).toEqual('2.00 MB');
+  });
+
+  it('formats gigabytes', () => {
+    expect(formatFileSize(1073741824)).toEqual('1.00 GB');
+    expect(formatFileSize(1610612736)).toEqual('1.50 GB');
+  });
+
+  it('formats terabytes', () => {
+    expect(formatFileSize(1099511627776)).toEqual('1.00 TB');
+  });
+
+  it('respects custom decimal places', () => {
+    expect(formatFileSize(1536, 0)).toEqual('2 KB');
+    expect(formatFileSize(1536, 1)).toEqual('1.5 KB');
+    expect(formatFileSize(1536, 3)).toEqual('1.500 KB');
+  });
+
+  it('handles very large numbers', () => {
+    const largeNumber = Math.pow(1024, 8); // YB
+    const result = formatFileSize(largeNumber);
+    expect(result).toContain('YB');
+  });
+
+  it('throws error for negative numbers', () => {
+    expect(() => formatFileSize(-1)).toThrow(
+      'Bytes must be a non-negative number',
+    );
+    expect(() => formatFileSize(-100)).toThrow(
+      'Bytes must be a non-negative number',
+    );
+  });
+
+  it('throws error for non-finite numbers', () => {
+    expect(() => formatFileSize(Infinity)).toThrow(
+      'Bytes must be a finite number',
+    );
+    expect(() => formatFileSize(-Infinity)).toThrow(
+      'Bytes must be a finite number',
+    );
+    expect(() => formatFileSize(NaN)).toThrow('Bytes must be a finite number');
+  });
+});

packages/react-native/Libraries/Utilities/formatFileSize.js

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+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ */
+
+/**
+ * Formats a number of bytes into a human-readable string.
+ *
+ * @param bytes - The number of bytes to format
+ * @param decimals - The number of decimal places to show (default: 2)
+ * @returns A formatted string like "1.5 KB", "2.3 MB", etc.
+ *
+ * @example
+ * formatFileSize(1024) // "1.00 KB"
+ * formatFileSize(1536) // "1.50 KB"
+ * formatFileSize(1048576) // "1.00 MB"
+ */
+export default function formatFileSize(
+  bytes: number,
+  decimals: number = 2,
+): string {
+  if (bytes === 0) {
+    return '0 Bytes';
+  }
+
+  if (!Number.isFinite(bytes)) {
+    throw new Error('Bytes must be a finite number');
+  }
+
+  if (bytes < 0) {
+    throw new Error('Bytes must be a non-negative number');
+  }
+
+  const k = 1024;
+  const sizes = ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
+  const i = Math.floor(Math.log(bytes) / Math.log(k));
+
+  // Ensure we don't go beyond the available sizes
+  const sizeIndex = Math.min(i, sizes.length - 1);
+  const size = sizes[sizeIndex];
+  const value = bytes / Math.pow(k, sizeIndex);
+
+  return `${value.toFixed(decimals)} ${size}`;
+}