feat: parallelize multimodal decode in request transfer.

[wly-115]

No description provided.

[gemini-code-assist]

Code Review

This pull request refactors the multi-modal input processing logic to enable parallel decoding. The MMHandlerSet::process method is split into load and decode phases, and MMInputTransfer now utilizes a ThreadPool and BlockingCounter to execute decoding tasks concurrently. Feedback focuses on adhering to the repository style guide, specifically regarding project-root-relative include paths, annotating constant arguments, reserving vector capacity, using early continue in loops to reduce nesting, and applying static_cast for type conversions.

[gemini-code-assist]

According to the repository style guide, all includes must use project-root-relative paths. The current paths are missing the core/ prefix.

Suggested change

	#include "util/blocking_counter.h"
	#include "util/threadpool.h"
	#include "core/util/blocking_counter.h"
	#include "core/util/threadpool.h"

References

1. No relative paths in #include. Always use project-root-relative paths. ^(link)

[gemini-code-assist]

Constant arguments in constructor calls should be annotated with the parameter name to improve readability, as per the repository style guide.

Suggested change

	threadpool_ = std::make_unique<ThreadPool>(16);
	threadpool_ = std::make_unique<ThreadPool>(/*num_threads=*/16);

References

1. Annotate constant arguments with a comment indicating the parameter name when calling functions or constructors. ^(link)

[gemini-code-assist]

The repository style guide requires calling reserve() before filling a std::vector when the size is known or can be estimated. Since mmc.size() is known, we should reserve capacity for inputs.

Suggested change

	inputs.clear();
	inputs.clear();
	inputs.reserve(mmc.size());

References

1. Always reserve() before filling a std::vector when the size is known or can be estimated. ^(link)

[gemini-code-assist]

The repository style guide recommends avoiding if blocks inside for loops for filtering logic. Using an early continue reduces indentation and improves readability.

    if (type == "text") {
      continue;
    }
    MMInputItem input;
    MMErrCode code = mm_handlers_->load(type, item, input, payload);
    if (code != MMErrCode::SUCCESS) {
      return code;
    }

    inputs.emplace_back(std::move(input));
    decode_tasks.emplace_back(DecodeTask{
        .type = type,
        .input_index = inputs.size() - 1,
    });

References

1. Avoid if inside for loops when possible. Prefer filtering the data beforehand or restructuring the logic (e.g., early continue). ^(link)

[gemini-code-assist]

The repository style guide requires using static_cast for all type conversions. Converting size_t to int32_t (as required by the BlockingCounter constructor) should be explicit.

Suggested change

	BlockingCounter counter(decode_tasks.size());
	BlockingCounter counter(static_cast<int32_t>(decode_tasks.size()));

References

1. Use static_cast for all type conversions. Never use C-style casts. ^(link)