[xpcom] Make Base64 compatible with ReadSegments() with small buffers.

2 files changed, 96 insertions, 0 deletions

diff --git a/netwerk/test/gtest/TestBase64Stream.cpp b/netwerk/test/gtest/TestBase64Stream.cpp
new file mode 100644
index 000000000..37f5cb824
--- /dev/null
+++ b/netwerk/test/gtest/TestBase64Stream.cpp
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include "mozilla/Base64.h"
+#include "nsIInputStream.h"
+
+namespace mozilla {
+namespace net {
+
+// An input stream whose ReadSegments method calls aWriter with writes of size
+// aStep from the provided aInput in order to test edge-cases related to small
+// buffers.
+class TestStream final : public nsIInputStream {
+ public:
+  NS_DECL_ISUPPORTS;
+
+  TestStream(const nsACString& aInput, uint32_t aStep)
+      : mInput(aInput), mStep(aStep) {}
+
+  NS_IMETHOD Close() override { MOZ_CRASH("This should not be called"); }
+
+  NS_IMETHOD Available(uint64_t* aLength) override {
+    *aLength = mInput.Length() - mPos;
+    return NS_OK;
+  }
+
+  NS_IMETHOD Read(char* aBuffer, uint32_t aCount,
+                  uint32_t* aReadCount) override {
+    MOZ_CRASH("This should not be called");
+  }
+
+  NS_IMETHOD ReadSegments(nsWriteSegmentFun aWriter, void* aClosure,
+                          uint32_t aCount, uint32_t* aResult) override {
+    *aResult = 0;
+
+    if (mPos == mInput.Length()) {
+      return NS_OK;
+    }
+
+    while (aCount > 0) {
+      uint32_t amt = std::min(mStep, (uint32_t)(mInput.Length() - mPos));
+
+      uint32_t read = 0;
+      nsresult rv =
+          aWriter(this, aClosure, mInput.get() + mPos, *aResult, amt, &read);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+
+      *aResult += read;
+      aCount -= read;
+      mPos += read;
+    }
+
+    return NS_OK;
+  }
+
+  NS_IMETHOD IsNonBlocking(bool* aNonBlocking) override {
+    *aNonBlocking = true;
+    return NS_OK;
+  }
+
+ private:
+  ~TestStream() = default;
+
+  nsCString mInput;
+  const uint32_t mStep;
+  uint32_t mPos = 0;
+};
+
+NS_IMPL_ISUPPORTS(TestStream, nsIInputStream)
+
+// Test the base64 encoder with writer buffer sizes between 1 byte and the
+// entire length of "Hello World!" in order to exercise various edge cases.
+TEST(TestBase64Stream, Run)
+{
+  nsCString input;
+  input.AssignLiteral("Hello World!");
+
+  for (uint32_t step = 1; step <= input.Length(); ++step) {
+    RefPtr<TestStream> ts = new TestStream(input, step);
+
+    nsAutoString encodedData;
+    nsresult rv = Base64EncodeInputStream(ts, encodedData, input.Length());
+    ASSERT_TRUE(NS_SUCCEEDED(rv));
+
+    EXPECT_TRUE(encodedData.EqualsLiteral("SGVsbG8gV29ybGQh"));
+  }
+}
+
+}  // namespace net
+}  // namespace mozilla
diff --git a/netwerk/test/gtest/moz.build b/netwerk/test/gtest/moz.build
index 6e6c80152..e463feb65 100644
--- a/netwerk/test/gtest/moz.build
+++ b/netwerk/test/gtest/moz.build
@@ -5,6 +5,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 UNIFIED_SOURCES += [
+    'TestBase64Stream.cpp',
     'TestProtocolProxyService.cpp',
     'TestStandardURL.cpp',
 ]