8000 数据发送分片 · Issue #2 · aeo123/upacker · GitHub
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linhuikui opened this issue Aug 23, 2019 · 3 comments
Open

数据发送分片 #2

linhuikui opened this issue Aug 23, 2019 · 3 comments

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@linhuikui
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建议数据发送的时候，不要分两次发送；否则接收端用超时回调时，接收到的数据可能不完整。尽量不要分片发送。
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@aeo123
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aeo123 commented Aug 23, 2019

建议数据发送的时候，不要分两次发送；否则接收端用超时回调时，接收到的数据可能不完整。尽量不要分片发送。

感谢，居然有人看。
static uint8_t frame_encode(upacker_inst_t packer, uint8_t *data, uint16_t size)
{

uint8_t tmp[4] = {0};
uint8_t crc = 0;

if (size > 16384)
{
return 0;
}

tmp[0] = 0x55;
tmp[1] = size & 0xff;
tmp[2] = (size >> 8) & 0x3f; //低14位用来保存size;header校验4位
crc = tmp[0] ^ tmp[1] ^ tmp[2];
tmp[2] |= (crc & 0x0C) << 4; //tmp[2][7:6]保存header检验[3:2]
tmp[3] = 0x03 & (crc >> 4); //tmp[3][1:0]保存header校验[5:4]
for (int i = 0; i < size; i++)
{
crc ^= data[i];
}

tmp[3] |= (crc & 0xfc); //tmp[3][7:2]保存data check[7:2]
packer->send(tmp, 4);
packer->send(data, size);

return 1;
}
以下是我的想法：
1.这里send两次的原因是我想着节约内存，因为包头和payload不是连续的。
2.另外不存在数据不完整不存在，这个代码就是为了解决数据帧的粘包、分包，接收端不管收到多少数据都丢进来解析就行了。
3.关于这里的发送其实还有后续，还带一个双缓冲，然后丢到串口dma。这里send实际只是push到了缓存区。当然直接阻塞发送也是没问题的

@luzefeng123
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不仅有人看 ,还有不少人在用了, 我fork了一下, 把c++ 的发送两次回调用动态申请内存改成了回调一次, c的两次回调, 我也没好办法,

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@linhuikui @aeo123 @luzefeng123
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