[Fetch API] Implement Request.formData and Response.formData.

third_party/WebKit/Source/modules/fetch/MultipartParser.cpp

+// Copyright 2016 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 "modules/fetch/MultipartParser.h"
+
+#include "public/platform/Platform.h"
+
+#include <algorithm>
+#include <utility>
+
+namespace blink {
+
+namespace {
+    constexpr char kCloseDelimiterSuffix[] = "--\r\n";
+    constexpr char kDelimiterSuffix[] = "\r\n";
+    constexpr size_t kDelimiterOffsetForEmptyPreamble = 2u; // For no "\r\n" prefix.
+    constexpr size_t kDelimiterOffsetForEmptyBody = kDelimiterOffsetForEmptyPreamble;
+}

[yhirano, 2016/09/12 02:20:49]

 // namespace

[e_hakkinen, 2016/09/16 13:41:36]

Done.

+
+MultipartParser::MultipartParser(Vector<char> boundary, Client* client)
+    : m_delimiter(std::move(boundary))
+    , m_client(client)
+    , m_seenDelimiterLength(0u)
+    , m_seenDelimiterOffset(kDelimiterOffsetForEmptyPreamble)
+{
+    // The delimiter consists of "\r\n" and a dash delimiter which consists of
+    // "--" and a boundary.
+    m_delimiter.prepend("\r\n--", 4u);
+}
+
+bool MultipartParser::appendData(const char* bytes, size_t size)
+{
+    DCHECK_NE(Finished, m_state);
+    DCHECK_NE(Cancelled, m_state);
+
+    while (size > 0u) {
+        size_t index = 0u;
+
+        switch (m_state) {
+        case ParsingPreamble:
+            // Parse either a preamble and a delimiter or a dash delimiter.
+            if (parseDelimiter(bytes, size, &index))
+                m_state = ParsingDelimiterSuffix;
+            break;
+
+        case ParsingDelimiterSuffix:
+            // Parse transport padding and "\r\n" after a delimiter.
+            if (parseDelimiterSuffix(bytes, size, &index, kDelimiterSuffix))
+                m_state = ParsingPartHeaderFields;
+            break;
+
+        case ParsingPartHeaderFields: {
+            // Parse part header fields (which ends with "\r\n") and an empty
+            // line (which also ends with "\r\n").
+            WebURLResponse response;
+
+            // Combine the current bytes with previously seen header bytes if
+            // needed.
+            const char* headerBytes = bytes + index;
+            size_t headerSize = size - index;
+            if (!m_seenHeaderBytes.isEmpty()) {
+                m_seenHeaderBytes.append(headerBytes, headerSize);
+                headerBytes = m_seenHeaderBytes.data();
+                headerSize = m_seenHeaderBytes.size();
+            }
+
+            size_t end = 0;
+            if (!Platform::current()->parseMultipartHeadersFromBody(headerBytes, headerSize, &response, &end)) {
+                // Store the current bytes for the next call.
+                if (headerBytes != m_seenHeaderBytes.data())

[yhirano, 2016/09/12 02:20:49]

if (m_seenHeaderBytes.isEmpty()) is easier to understand.

[e_hakkinen, 2016/09/16 13:41:36]

Done.

+                    m_seenHeaderBytes.append(headerBytes, headerSize);
+                return true;
+            }
+
+            m_seenDelimiterLength = 0u;
+            m_seenDelimiterOffset = kDelimiterOffsetForEmptyBody;
+            m_seenHeaderBytes.shrink(0);

[yhirano, 2016/09/12 02:20:49]

clear()

[e_hakkinen, 2016/09/16 13:41:36]

Done.

+            m_state = ParsingPartOctets;
+            index = size - (headerSize - end);
+            m_client->partHeaderFieldsInMultipartReceived(
+                response.toResourceResponse());
+            break;
+        }
+
+        case ParsingPartOctets: {
+            // Parse either a non-empty part octets and a delimiter or an empty
+            // part octets and a dash delimiter.
+            size_t initialSeenDelimiterLength = m_seenDelimiterLength;
+            size_t initialSeenDelimiterOffset = m_seenDelimiterOffset;
+            if (parseDelimiter(bytes, size, &index))
+                m_state = ParsingDelimiterOrCloseDelimiterSuffix;
+            if (index >= m_seenDelimiterLength && initialSeenDelimiterLength > 0u)
+                m_client->partDataInMultipartReceived(m_delimiter.data() + initialSeenDelimiterOffset, initialSeenDelimiterLength);
+            if (index > m_seenDelimiterLength)
+                m_client->partDataInMultipartReceived(bytes, index - m_seenDelimiterLength);
+            if (m_state == ParsingDelimiterOrCloseDelimiterSuffix)
+                m_client->partDataInMultipartFullyReceived();
+            break;
+        }
+
+        case ParsingDelimiterOrCloseDelimiterSuffix:
+            m_state = bytes[index] != '-' ? ParsingDelimiterSuffix : ParsingCloseDelimiterSuffix;

[yhirano, 2016/09/12 02:20:49]

This is not correct. When parsing the first "dash-boundary transport-padding
CRLF" in multipart-body,  we need reject the input if we see '-' here.

[e_hakkinen, 2016/09/16 13:41:36]

No, it is correct.
That's true. That is why next state after a preamble and a delimiter is
ParsingDelimiterSuffix (see the line 44) and not
ParsingDelimiterOrCloseDelimiterSuffix as we need to reject the input if we see
a close delimiter suffix.

So, the parsing state can be ParsingDelimiterOrCloseDelimiterSuffix only after
part octets and a delimiter (see the line 92) as that is the only place in the
input where both a delimiter suffix and a close delimiter suffix are allowed.

[yhirano, 2016/09/20 09:49:53]

Thank you, I understand.

+            break;
+
+        case ParsingCloseDelimiterSuffix:
+            // Parse "--", transport padding and "\r\n" after a delimiter
+            // (a delimiter and "--" constitute a close delimiter).
+            if (parseDelimiterSuffix(bytes, size, &index, kCloseDelimiterSuffix))
+                m_state = ParsingEpilogue;
+            break;
+
+        case ParsingEpilogue:
+            // Data in an epilogue should be ignored.
+            return true;
+
+        case Cancelled:
+        case Finished:
+            // The client changed the state.
+            return true;
+
+        case Failed:
+            // Keep failing.
+            return false;
+        }
+
+        bytes += index;
+        size -= index;
+    }
+
+    return true;
+}
+
+void MultipartParser::cancel()
+{
+    m_state = Cancelled;
+}
+
+bool MultipartParser::finish()
+{
+    DCHECK_NE(Cancelled, m_state);
+
+    State initialState = m_state;
+
+    if (m_state == ParsingPartOctets && m_seenDelimiterLength > 0u && m_seenDelimiterOffset + m_seenDelimiterLength < m_delimiter.size()) {
+        // The end of append bytes looked like a delimiter but was not a full
+        // one, after all. Treat the those bytes as part of part octets.
+        m_client->partDataInMultipartReceived(
+            m_delimiter.data() + m_seenDelimiterOffset, m_seenDelimiterLength);
+    }
+    m_state = Finished;
+
+    switch (initialState) {
+    case ParsingCloseDelimiterSuffix:
+        // Require a full close delimiter consisting of a delimiter and "--"
+        // but ignore missing or partial "\r\n" after that.
+        return seenDelimiterSuffixLength() >= 2u;
+    case ParsingEpilogue:
+    case Finished:
+        return true;
+    default:
+        return false;
+    }
+}
+
+size_t MultipartParser::countNonDelimiterBytes(const char* bytes, size_t size) const
+{
+    const char* p = static_cast<const char*>(memchr(bytes, '\r', size));
+    if (p)
+        return static_cast<size_t>(p - bytes);
+    return size;
+}
+
+size_t MultipartParser::countPossibleDelimiterBytes(const char* bytes, size_t size) const
+{
+    size_t index = 0u;
+    while (index < size && m_seenDelimiterOffset + m_seenDelimiterLength + index < m_delimiter.size() && bytes[index] == m_delimiter[m_seenDelimiterOffset + m_seenDelimiterLength + index])
+        ++index;
+    return index;
+}
+
+size_t MultipartParser::countTransportPaddingBytes(const char* bytes, size_t size) const
+{
+    size_t index = 0u;
+    while (index < size && (bytes[index] == '\t' || bytes[index] == ' '))
+        ++index;
+    return index;
+}
+
+bool MultipartParser::parseDelimiter(const char* bytes, size_t size, size_t* index)
+{
+    for (;;) {
+        // Try to continue reading a delimiter.
+        size_t possibleDelimiterBytes = countPossibleDelimiterBytes(bytes + *index, size - *index);
+        if (possibleDelimiterBytes > 0u) {

[yhirano, 2016/09/12 02:20:49]

Is it OK to execute these statements unconditionally?

+            m_seenDelimiterLength += possibleDelimiterBytes;
+            *index += possibleDelimiterBytes;
+        }

[yhirano, 2016/09/12 02:20:49]

DCHECK_LE(*index, size);

+        size_t seenDelimiterEnd = m_seenDelimiterOffset + m_seenDelimiterLength;
+        if (seenDelimiterEnd == m_delimiter.size())
+            return true;
+        if (*index >= size)
+            break;
+
+        // Jump to the next possible delimiter or to the end of bytes.
+        m_seenDelimiterLength = 0u;
+        m_seenDelimiterOffset = 0u;
+        *index += countNonDelimiterBytes(bytes + *index, size - *index);

[yhirano, 2016/09/12 02:20:49]

DCHECK_LE(*index, size);

+    }
+    return false;
+}
+
+bool MultipartParser::parseDelimiterSuffix(const char* bytes, size_t size, size_t* index, const char* suffix)
+{
+    while (char expected = suffix[seenDelimiterSuffixLength()]) {
+        if (expected == '\r')

[yhirano, 2016/09/12 02:20:49]

Hmm... I don't like this special case. The function looks like an general
parsing (e.g., taking a pattern to match) but it starts consuming LWSPs if it
sees a certain character.

[e_hakkinen, 2016/09/16 13:41:36]

Removed.

+            *index += countTransportPaddingBytes(bytes + *index, size - *index);
+        if (*index >= size)
+            return false;
+        if (bytes[(*index)++] != expected) {
+            m_state = Failed;
+            return false;
+        }
+        ++m_seenDelimiterLength;

[yhirano, 2016/09/12 02:20:49]

I don't understand - what you are seeing here is not the delimiter, but a
"delimiter suffix". Why are you updating this variable?

[e_hakkinen, 2016/09/16 13:41:36]

Sorry for reusing m_seenDelimiterLength for m_seenDelimiterSuffixLength.
Reimplemented.

+    }
+    return true;
+}
+
+size_t MultipartParser::seenDelimiterSuffixLength() const
+{
+    return m_seenDelimiterOffset + m_seenDelimiterLength - m_delimiter.size();
+}
+
+DEFINE_TRACE(MultipartParser)
+{
+    visitor->trace(m_client);
+}
+
+} // namespace blink