[Issue 13285][pulsar-client] Optimize MessageBuilder and SharedBuffer to avoid unnecessary memory copy.

[tongsucn]

Fixes #13285

Motivation

See more in #13285

Modifications

1. Replaced std::vector<char> with std::string as the internal storage of SharedBuffer.
2. Added new interface MessageBuilder::setContent(std::string&&).
3. Added new move-constructors in SharedBuffer.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API: no
• The schema: no
• The default values of configurations: no
• The wire protocol: no
• The rest endpoints: no
• The admin cli options: no
• Anything that affects deployment: no

Documentation

Check the box below and label this PR (if you have committer privilege).

Need to update docs?

• no-need-doc

It does not add any new public interface, the comment on the function declaration is enough.

[github-actions]

@tongsucn:Thanks for your contribution. For this PR, do we need to update docs?
(The PR template contains info about doc, which helps others know more about the changes. Can you provide doc-related info in this and future PR descriptions? Thanks)

[github-actions]

@tongsucn:Thanks for providing doc info!

[merlimat]

@tongsucn Can you also add a unit tests for the new setContent() method?

[BewareMyPower]

I have a suggestion for testing the memory copy doesn't occur after this change, but it might depend on the implementation of std::string.

TEST(MessageBuilderTest, testSetContent) {
    std::string value;
    value.resize(1024, 'x');
    const void* originalAddress = &value[0];
    {
        auto msg = MessageBuilder().setContent(value).build();
        ASSERT_NE(msg.getData(), originalAddress);
    }
    {
        auto msg = MessageBuilder().setContent(std::move(value)).build();
        ASSERT_EQ(msg.getData(), originalAddress);
    }
}

[tongsucn]

auto msg = MessageBuilder().setContent(value).build();

@BewareMyPower I think the first setContent assertion should be fine. Because it internally allocates a same-sized std::string and calls std::copy explicitly, rather than using std::string's copy constructor. Thanks bro

[tongsucn]

@tongsucn Can you also add a unit tests for the new setContent() method?

@merlimat OK, I'll add some tests today.

[codelipenghui]

@tongsucn Any update on this PR?

[tongsucn]

@codelipenghui Just added a test case on MessageBuilder::setContent.

[merlimat]

@tongsucn You should either rebase or merge with master as there were some merge conflicts that make the checkstyle to fail. It's already fixed in latest master.

[tongsucn]

@tongsucn You should either rebase or merge with master as there were some merge conflicts that make the checkstyle to fail. It's already fixed in latest master.

@merlimat done