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Question

为了通过线路将复杂的 JSON/JavaScript 对象发送到 C++ 二进制文件，我使用了 Protocol Buffers。如今，Node.js 有原生 protobuf 支持，因此我没有使用任何其他绑定。

// Set maximum execution time of binary to equal the
// remainder of processing time, minus a second to allow
// for parsing.
var timeLimit = context.getRemainingTimeInMillis() - 1000;

// Check if meta parameters are given in the request.
// Assign default values if they are not.
var model = new protocols.Model();

// Sort the resolutions.
function descending(a, b) {
    if (a.width > b.width) {
        return -1;
    } else if (a.width < b.width) {
        return 1;
    }
    return 0;
}

// Construct image objects.
var images = request.images.map(function(image) {
    // Perform the sort.
    image.resolutions.sort(descending);

    // Create an image protobuffer.
    var imageProto = new protocols.Model.Image();

    // Assign the original's resolution to the image.
    imageProto.setWidth(image.resolutions[0].width);
    imageProto.setHeight(image.resolutions[0].height);

    // Return the result.
    return imageProto;
});

// Construct flag enumeration references.
var flags = request.flags.map(function(flag) {
    return protocols.Model.Flag[flag];
});

// Assign request properties to protobuf.
model.setImagesList     (images                                                     );
model.setFlagsList      (flags                                                      );
model.setMinNoOfPages   (request.minNoOfPages   ? request.minNoOfPages  : 1         );
model.setMaxNoOfPages   (request.maxNoOfPages   ? request.maxNoOfPages  : 1         );
model.setMaxPerPage     (request.maxPerPage     ? request.maxPerPage    : 5         );
model.setPageWidth      (request.pageWidth      ? request.pageWidth     : 3508      );
model.setPageHeight     (request.pageHeight     ? request.pageHeight    : 2480      );
model.setTimeLimit      (request.timeLimit      ? request.timeLimit     : timeLimit );
model.setBorderWidth    (request.borderWidth    ? request.borderWidth   : 0         );
model.setMinDim         (request.minDim         ? request.minDim        : 0         );

// This is where things go wrong.
var serialized = model.serializeBinary();
fs.writeFileSync('model.pb', serialized);
var read = fs.readFileSync('model.pb'),
    model2 = protocols.Model.deserializeBinary(read);

console.log(model.toObject());
console.log(model2.toObject());

上面是我坚持的一段代码。我设法编译了一条 protobuf 消息：

syntax = "proto3";

package layout;

message Model {

    enum Flag {
        FILL_PAGE = 0;
        BORDERS = 1;
    }

    message Image {
        int32 width = 1;
        int32 height = 2;
    }

    repeated Flag flags = 1;
    repeated Image images = 2;

    string avoid_layout = 3;
    int32 min_no_of_pages = 4;
    int32 max_no_of_pages = 5;
    int32 max_per_page = 6;
    int32 page_width = 7;
    int32 page_height = 8;
    int32 time_limit = 9;
    int32 border_width = 10;
    int32 min_dim = 11;
}

然而，关于 JavaScript 对 protobuf 支持的文档很少（https://developers.google.com/protocol-buffers/docs/reference/javascript-generate#message），我不知道如何将消息读取到文件，然后再次读取它们。有人可以向我解释如何做到这一点吗？

我想解决方案是我的代码最后几行的一些变化，但目前我收到此错误：

AssertionError: Failure: Type not convertible to Uint8Array.

Answer 1

Buffer您可能正在目睹一些节点不被识别为的晦涩案例Uint8Array。我找到了相关的问题报告。所以尝试强制执行类型

protocols.Model.deserializeBinary(new Uint8Array(read));

或替换构造函数。该建议与您的建议特别相似 - 它也是读取二进制文件。