Introduce FetchFormDataConsumerHandle.

Source/modules/fetch/FetchFormDataConsumerHandle.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "modules/fetch/FetchFormDataConsumerHandle.h"
+
+#include "modules/fetch/DataConsumerHandleUtil.h"
+#include "modules/fetch/FetchBlobDataConsumerHandle.h"
+#include "wtf/ThreadSafeRefCounted.h"
+#include "wtf/ThreadingPrimitives.h"
+#include "wtf/Vector.h"
+#include "wtf/text/TextCodec.h"
+#include "wtf/text/TextEncoding.h"
+#include "wtf/text/WTFString.h"
+
+#include <utility>
+
+namespace blink {
+
+using Result = FetchDataConsumerHandle::Result;
+
+class FetchFormDataConsumerHandle::Context : public ThreadSafeRefCounted<Context> {
+    WTF_MAKE_NONCOPYABLE(Context);
+public:
+    virtual ~Context() {}
+    virtual PassOwnPtr<FetchDataConsumerHandle::Reader> obtainReader(Client*) = 0;
+
+protected:
+    explicit Context() {}
+};
+
+class FetchFormDataConsumerHandle::SimpleContext final : public Context {
+    class ReaderImpl;
+public:
+    static PassRefPtr<SimpleContext> create(const String& body) { return adoptRef(new SimpleContext(body)); }
+    static PassRefPtr<SimpleContext> create(const void* data, size_t size) { return adoptRef(new SimpleContext(data, size)); }
+    static PassRefPtr<SimpleContext> create(PassRefPtr<FormData> body) { return adoptRef(new SimpleContext(body)); }
+
+    PassOwnPtr<Reader> obtainReader(Client* client) override
+    {
+        // For memory barrier.
+        Mutex m;
+        MutexLocker locker(m);

[hiroshige, 2015/08/11 09:35:01]

BTW if we need memory barrier here, should we also add similar code to existing
code? Can we detect if we are missing memory barriers here by tests?

[yhirano, 2015/08/11 11:36:01]

If a user obtains and releases a reader on one thread, and obtains a reader
after that on another thread without a memory barrier, it could confuse the
implementation. On the other hand, I'm sure such a usage is not reliable and
always buggy without an external memory barrier. What do you think?

+        return ReaderImpl::create(this, client);
+    }
+
+    PassRefPtr<FormData> drainFormData()

[hiroshige, 2015/08/11 09:35:01]

IIUC:
1. If flatten() is called before drainFormData(), m_formData is cleared so
subsequent drainFormData() returns nullptr;
2. If drainFormData() is called before flatten(), m_flattenFormData is kept
empty so subsequent read()/beginRead() returns Done.
right?
If so, the interaction between |m_formData| and |m_flattenFormData| is a little
confusing, stating in invariants of them in comments might be helpful.

[yhirano, 2015/08/11 11:36:01]

Done.

+    {
+        ASSERT(!m_formData || m_formData->hasOneRef());
+        return m_formData.release();
+    }
+
+    Result read(void* data, size_t size, Flags flags, size_t* readSize)
+    {
+        *readSize = 0;
+        if (size == 0) {
+            if (!m_formData && m_flattenFormData.size() == m_flattenFormDataOffset)
+                return WebDataConsumerHandle::Done;
+            return WebDataConsumerHandle::Ok;
+        }
+        flatten();
+

[hiroshige, 2015/08/11 09:35:01]

How about adding "RELEASE_ASSERT(m_flattenFormData.size() >=
m_flattenFormDataOffset)"?

[yhirano, 2015/08/11 11:36:01]

Done.

+        *readSize = std::min(size, m_flattenFormData.size() - m_flattenFormDataOffset);
+        if (*readSize == 0)
+            return WebDataConsumerHandle::Done;
+        memcpy(data, &m_flattenFormData[m_flattenFormDataOffset], *readSize);
+        m_flattenFormDataOffset += *readSize;
+        return WebDataConsumerHandle::Ok;
+    }
+
+    Result beginRead(const void** buffer, Flags flags, size_t* available)
+    {
+        *buffer = nullptr;
+        *available = 0;
+
+        flatten();
+        if (m_flattenFormData.size() == m_flattenFormDataOffset)
+            return WebDataConsumerHandle::Done;

[hiroshige, 2015/08/11 09:35:01]

ditto.

[yhirano, 2015/08/11 11:36:01]

Done.

+        *buffer = &m_flattenFormData[m_flattenFormDataOffset];
+        *available = m_flattenFormData.size() - m_flattenFormDataOffset;
+        return WebDataConsumerHandle::Ok;
+    }
+
+    Result endRead(size_t read)
+    {

[hiroshige, 2015/08/11 09:35:01]

Please add:
    RELEASE_ASSERT(m_flattenFormData.size() >=
m_flattenFormDataOffset);
    if (read > m_flattenFormData.size() - m_flattenFormDataOffset)
        return UnexpectedError;

[yhirano, 2015/08/11 11:36:01]

Done.

+        m_flattenFormDataOffset += read;
+        return WebDataConsumerHandle::Ok;
+    }
+
+private:
+    class ReaderImpl final : public FetchDataConsumerHandle::Reader {
+        WTF_MAKE_NONCOPYABLE(ReaderImpl);
+    public:
+        static PassOwnPtr<ReaderImpl> create(PassRefPtr<SimpleContext> context, Client* client) { return adoptPtr(new ReaderImpl(context, client)); }
+        Result read(void* data, size_t size, Flags flags, size_t* readSize) override
+        {
+            return m_context->read(data, size, flags, readSize);
+        }
+        Result beginRead(const void** buffer, Flags flags, size_t* available) override
+        {
+            return m_context->beginRead(buffer, flags, available);
+        }
+        Result endRead(size_t read) override
+        {
+            return m_context->endRead(read);
+        }
+        PassRefPtr<FormData> drainAsFormData() override
+        {
+            return m_context->drainFormData();
+        }
+
+    private:
+        ReaderImpl(PassRefPtr<SimpleContext> context, Client* client) : m_context(context), m_notifier(client) {}
+
+        RefPtr<SimpleContext> m_context;
+        NotifyOnReaderCreationHelper m_notifier;
+    };
+
+    explicit SimpleContext(const String& body)
+        : m_formData(FormData::create(UTF8Encoding().encode(body, WTF::EntitiesForUnencodables)))
+        , m_flattenFormDataOffset(0) {}
+    explicit SimpleContext(const void* data, size_t size)
+        : m_formData(FormData::create(data, size))
+        , m_flattenFormDataOffset(0) {}
+    explicit SimpleContext(PassRefPtr<FormData> body)
+        : m_formData(body->deepCopy())
+        , m_flattenFormDataOffset(0) {}
+
+    void flatten()
+    {
+        if (!m_formData) {
+            // It is already drained or flatten.
+            return;
+        }
+        ASSERT(m_formData->hasOneRef());
+        m_formData->flatten(m_flattenFormData);
+        m_formData = nullptr;
+    }
+
+    RefPtr<FormData> m_formData;
+    Vector<char> m_flattenFormData;
+    size_t m_flattenFormDataOffset;
+};
+
+class FetchFormDataConsumerHandle::ComplexContext final : public Context {
+    class ReaderImpl;
+public:
+    static PassRefPtr<ComplexContext> create(ExecutionContext* executionContext,
+        PassRefPtr<FormData> formData,
+        FetchBlobDataConsumerHandle::LoaderFactory* factory)
+    {
+        return adoptRef(new ComplexContext(executionContext, formData, factory));
+    }
+
+    PassOwnPtr<FetchFormDataConsumerHandle::Reader> obtainReader(Client* client) override
+    {
+        // For memory barrier.
+        Mutex m;
+        MutexLocker locker(m);
+        return ReaderImpl::create(this, client);
+    }
+
+private:
+    class ReaderImpl final : public FetchDataConsumerHandle::Reader {
+        WTF_MAKE_NONCOPYABLE(ReaderImpl);
+    public:
+        static PassOwnPtr<ReaderImpl> create(PassRefPtr<ComplexContext> context, Client* client) { return adoptPtr(new ReaderImpl(context, client)); }
+        Result read(void* data, size_t size, Flags flags, size_t* readSize) override
+        {
+            Result r = m_reader->read(data, size, flags, readSize);
+            if (!((r == Ok && *readSize == 0) || r == ShouldWait)) {
+                m_context->drainFormData();
+            }
+            return r;
+        }
+        Result beginRead(const void** buffer, Flags flags, size_t* available) override
+        {
+            Result r = m_reader->beginRead(buffer, flags, available);
+            if (r != ShouldWait) {
+                m_context->drainFormData();
+            }
+            return r;
+        }
+        Result endRead(size_t read) override
+        {
+            return m_reader->endRead(read);
+        }
+        PassRefPtr<BlobDataHandle> drainAsBlobDataHandle(BlobSizePolicy policy) override
+        {
+            m_context->drainFormData();
+            return m_reader->drainAsBlobDataHandle();
+        }
+        PassRefPtr<FormData> drainAsFormData() override
+        {
+            // Drain from the internal reader to sync the state.
+            m_reader->drainAsFormData();
+            return m_context->drainFormData();
+        }
+    private:
+        ReaderImpl(PassRefPtr<ComplexContext> context, Client* client) : m_context(context), m_reader(m_context->m_handle->obtainReader(client)) {}
+
+        RefPtr<ComplexContext> m_context;
+        OwnPtr<FetchDataConsumerHandle::Reader> m_reader;
+    };
+
+    explicit ComplexContext(ExecutionContext* executionContext, PassRefPtr<FormData> body, FetchBlobDataConsumerHandle::LoaderFactory* factory)
+        : m_formData(body->deepCopy())
+    {
+        OwnPtr<BlobData> blobData = BlobData::create();
+        for (const auto& element : m_formData->elements()) {
+            switch (element.m_type) {
+            case FormDataElement::data:
+                blobData->appendBytes(element.m_data.data(), element.m_data.size());
+                break;
+            case FormDataElement::encodedFile:
+                blobData->appendFile(element.m_filename, element.m_fileStart, element.m_fileLength, element.m_expectedFileModificationTime);
+                break;
+            case FormDataElement::encodedBlob:
+                if (element.m_optionalBlobDataHandle)
+                    blobData->appendBlob(element.m_optionalBlobDataHandle, 0, element.m_optionalBlobDataHandle->size());
+                break;
+            case FormDataElement::encodedFileSystemURL:
+                blobData->appendFileSystemURL(element.m_fileSystemURL, element.m_fileStart, element.m_fileLength, element.m_expectedFileModificationTime);

[hiroshige, 2015/08/11 10:19:04]

This is not thread-safe, because appendFileSystemURL() increases refs to
|element.m_fileSystemURL|, which is inside |m_formData|, so this makes
|m_formData| not a pure deep copy. (Similar thing applies to appendFile())
Working on |body| instead of |m_formData| in this constructor might resolve the
problem.

I added FormData::isSafeToSendToAnotherThread() in
https://codereview.chromium.org/1276203004.
Replacing FormData::hasOneRef() with FormData::isSafeToSendToAnotherThread() can
check more on thread-safety.

[yhirano, 2015/08/11 11:36:01]

Nice catch! done.

+                break;
+            }
+        }
+        // Here we handle m_formData->boundary() as a C-style string. See
+        // FormDataBuilder::generateUniqueBoundaryString.
+        blobData->setContentType(AtomicString("multipart/form-data; boundary=", AtomicString::ConstructFromLiteral) + m_formData->boundary().data());
+        auto size = blobData->length();
+        if (factory) {
+            // For testing
+            m_handle = FetchBlobDataConsumerHandle::create(executionContext, BlobDataHandle::create(blobData.release(), size), factory);
+        } else {
+            m_handle = FetchBlobDataConsumerHandle::create(executionContext, BlobDataHandle::create(blobData.release(), size));
+        }
+    }
+    PassRefPtr<FormData> drainFormData()
+    {
+        ASSERT(!m_formData || m_formData->hasOneRef());
+        return m_formData.release();
+    }
+
+    RefPtr<FormData> m_formData;
+    OwnPtr<FetchDataConsumerHandle> m_handle;
+};
+
+FetchFormDataConsumerHandle::FetchFormDataConsumerHandle(const String& body) : m_context(SimpleContext::create(body)) {}
+FetchFormDataConsumerHandle::FetchFormDataConsumerHandle(const void* data, size_t size) : m_context(SimpleContext::create(data, size)) {}
+FetchFormDataConsumerHandle::FetchFormDataConsumerHandle(ExecutionContext* executionContext,
+    PassRefPtr<FormData> body,
+    FetchBlobDataConsumerHandle::LoaderFactory* loaderFactory)
+{
+    if (isSimple(body.get())) {
+        m_context = SimpleContext::create(body);
+    } else {
+        m_context = ComplexContext::create(executionContext, body, loaderFactory);
+    }
+}
+FetchFormDataConsumerHandle::~FetchFormDataConsumerHandle() {}
+
+FetchDataConsumerHandle::Reader* FetchFormDataConsumerHandle::obtainReaderInternal(Client* client)
+{
+    return m_context->obtainReader(client).leakPtr();
+}
+
+bool FetchFormDataConsumerHandle::isSimple(const FormData* formData)
+{
+    for (const auto& element : formData->elements()) {
+        if (element.m_type != FormDataElement::data)
+            return false;
+    }
+    return true;
+}
+
+} // namespace blink