feat(crc32c): Convenient Method For Reading Files (googleapis#2095)

* feat(crc32c): Convenient Method For Reading Files

* fix: `fs/promises` for Node 12

* fix: Use `unlink`, `rm` isn't available on Node 12

* fix: Use `unlink`, `rm` isn't available on Node 12

Author: d-goog

src/crc32c.ts

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import {PathLike, createReadStream} from 'fs';
+
 /**
  * Ported from {@link https://github.com/google/crc32c/blob/21fc8ef30415a635e7351ffa0e5d5367943d4a94/src/crc32c_portable.cc#L16-L59 github.com/google/crc32c}
  */
@@ -252,6 +254,19 @@ class CRC32C implements CRC32CValidator {
     return new CRC32C(buffer.readInt32BE());
   }
 
+  static async fromFile(file: PathLike) {
+    const crc32c = new CRC32C();
+
+    await new Promise((resolve, reject) => {
+      createReadStream(file)
+        .on('data', (d: Buffer) => crc32c.update(d))
+        .on('end', resolve)
+        .on('error', reject);
+    });
+
+    return crc32c;
+  }
+
   /**
    * Generates a `CRC32C` from 4-byte base64-encoded data (string).
    *
@@ -286,6 +301,7 @@ class CRC32C implements CRC32CValidator {
 
   /**
    * Generates a `CRC32C` from a variety of compatable types.
+   * Note: strings are treated as input, not as file paths to read from.
    *
    * @param value A number, 4-byte `ArrayBufferView`/`Buffer`/`TypedArray`, or 4-byte base64-encoded data (string)
    */

system-test/storage.ts

@@ -2698,14 +2698,7 @@ describe('storage', () => {
 
         before(async () => {
           // get a CRC32C value from the file
-          crc32c = await new Promise((resolve, reject) => {
-            const crc32c = new CRC32C();
-
-            fs.createReadStream(filePath)
-              .on('data', (d: Buffer) => crc32c.update(d))
-              .on('end', () => resolve(crc32c.toString()))
-              .on('error', reject);
-          });
+          crc32c = (await CRC32C.fromFile(filePath)).toString();
         });
 
         async function uploadAndVerify(

test/crc32c.ts

@@ -20,6 +20,9 @@ import {
   CRC32C_EXCEPTION_MESSAGES,
 } from '../src';
 import * as assert from 'assert';
+import {join} from 'path';
+import {tmpdir} from 'os';
+import * as fs from 'fs';
 
 const KNOWN_INPUT_TO_CRC32C = {
   /** empty string (i.e. nothing to 'update') */
@@ -497,5 +500,30 @@ describe('CRC32C', () => {
         });
       });
     });
+
+    describe('.fromFile', () => {
+      let tempFilePath: string;
+
+      beforeEach(async () => {
+        tempFilePath = join(tmpdir(), 'test.crc32c.fromFile');
+      });
+
+      after(async () => {
+        try {
+          await fs.promises.unlink(tempFilePath);
+        } catch (e) {
+          // errors are fine
+        }
+      });
+
+      it('should generate a valid `crc32c` via a file path', async () => {
+        for (const [key, expected] of Object.entries(KNOWN_INPUT_TO_CRC32C)) {
+          await fs.promises.writeFile(tempFilePath, key);
+
+          const crc32c = await CRC32C.fromFile(tempFilePath);
+          assert.equal(crc32c.toString(), expected);
+        }
+      });
+    });
   });
 });