[英]DecodeError when reading Proto Buffer message from nanopb
I implemented a small HttpClient for an IoT device and wanted to use Proto Buffer as a communication format.我为 IoT 设备实现了一个小型 HttpClient,并希望使用 Proto Buffer 作为一种通信格式。 Because of the constraints of the platform I am using nanopb.由于平台的限制,我使用的是 nanopb。 That's the relevant code in C:这是C中的相关代码:
#include <pb_encode.h>
#include "device_data.pb.h"
#include <ESP8266HTTPClient.h>
[...]
pb_MEvent m_event = pb_MEvent_init_zero;
uint8_t m_buffer[21];
pb_ostream_t stream = pb_ostream_from_buffer(m_buffer, 21);
pb_encode(&stream, pb_MEvent_fields, &m_event);
int httpCode = httpClient.POST(m_buffer, stream.bytes_written);
[...]
I created a small flask server which exposes an endpoint.我创建了一个小型 flask 服务器,它公开了一个端点。 When I try to decode the message, I get the following error: google.protobuf.message.DecodeError: Error parsing message with type 'pb.MEvent'
当我尝试解码消息时,出现以下错误: google.protobuf.message.DecodeError: Error parsing message with type 'pb.MEvent'
That the code for it:它的代码:
from flask import Flask, request
from device_data_pb2 import MEvent
app = Flask(__name__)
@app.route("/", methods = ['POST', "GET"])
def hello_world():
m_event = MEvent()
m_event.ParseFromString(request.data)
print(m_event)
if __name__ == '__main__':
app.run(host='0.0.0.0', port= 5000)
I tried to use io.ByteStream and read it then and I also tried to encode the bytes with ASCII and UTF-8 but neither of that approaches worked.我尝试使用 io.ByteStream 然后读取它,我还尝试使用 ASCII 和 UTF-8 对字节进行编码,但这些方法都不起作用。
Could you please help me find out, what is causing the problem?您能帮我找出问题所在吗? The error message is not that helpful.错误消息没有那么有用。
This is the content fo the proto file:这是 proto 文件的内容:
syntax = "proto2";
package pb;
message MEvent {
required float accelX = 1;
required float accelY = 2;
required float accelZ = 3;
required float gyroX = 4;
required float gyroY = 5;
required float gyroZ = 6;
required int64 msec = 7;
}
And here are some data points:以下是一些数据点:
DATA:
0.16 -0.08 9.96 0.00 -0.00 0.02 0
HEX:
0d:98:d7:27:3e:15:bf:f7:ad:bd:1d:46:70:1f:41:25:b5:33:70:3b:2d
DATA:
0.16 -0.09 9.96 0.00 -0.00 0.02 0
HEX:
0d:cd:7d:20:3e:15:56:ab:bc:bd:1d:5f:6b:1f:41:25:79:22:a0:3b:2d
DATA:
0.15 -0.10 9.96 0.00 -0.00 0.02 0
HEX:
0d:89:0a:1e:3e:15:21:05:c4:bd:1d:de:52:1f:41:25:b5:33:70:3b:2d
DATA: 0.16 -0.08 9.96 0.00 -0.00 0.02 0 HEX: 0d:98:d7:27:3e:15:bf:f7:ad:bd:1d:46:70:1f:41:25:b5:33:70:3b:2d数据:0.16 -0.08 9.96 0.00 -0.00 0.02 0 十六进制:0d:98:d7:27:3e:15:bf:f7:ad:bd:1d:46:70:1f:41:25:b5:33:70 :3b:2d
I'm using the nanopb/tests/raw_decode
to analyze this.我正在使用nanopb/tests/raw_decode
来分析这个。 Marc Gravell's decode utility used to be great for this but for some reason it does not work very well for corrupted data anymore. Marc Gravell 的解码实用程序曾经非常适合此功能,但由于某种原因,它不再适用于损坏的数据。
user@host:~/nanopb/tests$ echo 0d:98:d7:27:3e:15:bf:f7:ad:bd:1d:46:70:1f:41:25:b5:33:70:3b:2d \ | tr -d ':' | xxd -r -p | build/raw_decode/raw_decode At 0: field tag 1, wire type 5 (32BIT), fixed32 value (4 bytes): 0x3e27d798 At 5: field tag 2, wire type 5 (32BIT), fixed32 value (4 bytes): 0xbdadf7bf At 10: field tag 3, wire type 5 (32BIT), fixed32 value (4 bytes): 0x411f7046 At 15: field tag 4, wire type 5 (32BIT), fixed32 value (4 bytes): 0x3b7033b5 At 20: field tag 5, wire type 5 (32BIT) ERROR: Failed to parse fixed32: io error LATEST BYTES READ (21 to 21):
It appears your message is cut short.看来您的消息被缩短了。 The amount of buffer space you reserve on this line is not large enough:您在此行保留的缓冲区空间量不够大:
uint8_t m_buffer[21]; uint8_t m_buffer[21];
If you check the return value of pb_encode()
it is probably also returning false
and stream.errmsg
indicates that the buffer is full.如果您检查pb_encode()
的返回值,它可能也返回false
并且stream.errmsg
表示缓冲区已满。
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