serial.cpp.hpp

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// src/fl/remote/transport/serial.cpp.hpp
// Implementation of JSON-RPC serial transport layer
 
#pragma once
 
#include "fl/remote/transport/serial.h"
#include "fl/stl/cstring.h"
#include "fl/stl/noexcept.h"
 
namespace fl {
 
namespace {
// Small error reply used when the response cannot be serialized or framed.
fl::string outOfMemoryResponse(const char* prefix, fl::size prefixLength) FL_NO_EXCEPT {
    static const char error[] =
        "{\"error\":{\"code\":-32603,\"message\":\"Out of memory\"},"
        "\"id\":null,\"jsonrpc\":\"2.0\"}";
    fl::string failure;
    failure.write(prefix, prefixLength);
    failure.write(error, sizeof(error) - 1);
    if (failure.size() == prefixLength + sizeof(error) - 1) {
        return failure;
    }
    return error;
}
} // namespace
 
fl::string formatJsonResponse(const fl::json& response, const char* prefix) FL_NO_EXCEPT {
    // Reuse the serialized body. A second growing stream kept two full copies
    // of large discovery responses alive and could exhaust ESP32's heap.
    fl::string jsonStr = response.to_string();
    const fl::size bodyLength = jsonStr.size();
    const fl::size prefixLength = prefix ? fl::strlen(prefix) : 0;
    if (bodyLength == 0) {
        // to_string() returns empty only when its buffer could not be
        // allocated; never publish a bare prefix (FastLED #4899).
        return outOfMemoryResponse(prefix, prefixLength);
    }
    if (prefixLength != 0) {
        const fl::size totalLength = bodyLength + prefixLength;
        if (totalLength >= bodyLength && totalLength != fl::string::npos) {
            jsonStr.reserve(totalLength);
            jsonStr.write(prefix, prefixLength);
        }
        if (jsonStr.size() != totalLength || totalLength < bodyLength) {
            // Release the large body before allocating the small error reply.
            // A failed extension must not publish partially formed JSON.
            jsonStr.clear(true);
            return outOfMemoryResponse(prefix, prefixLength);
        }
        char *bytes = &jsonStr[0]; // fl-lint: container-data-ptr-ok - contiguous mutable string for memmove/memcpy interop
        fl::memmove(bytes + prefixLength, bytes, bodyLength);
        fl::memcpy(bytes, prefix, prefixLength);
    }
 
    // Preserve prefix bytes; normalize only the serialized body in place.
    for (fl::size i = prefixLength; i < jsonStr.size(); ++i) {
        char &byte = jsonStr[i];
        if (byte == '\n' || byte == '\r') {
            byte = ' ';
        }
    }
    return jsonStr;
}
 
} // namespace fl