如何解决LWIP pbuf 复制到另一个缓冲区
我在我的 stm32f4 项目中使用 LWIP 库。在low_level_output 函数中有pbuf p 成员。我需要用 length + 1 改变它的长度,我需要在 pbuf->payload 的末尾添加 1 个字节,但我不想改变 pbuf 所以我需要定义新的 pbuf 来复制这个 pbuf 内容,而不是我需要使用这个行 for(q = mypBuf; q != NULL; q = q->next)
而不是下面的 for 循环。
我怎样才能做到这一点 ?请帮帮我。
static err_t low_level_output(struct netif *netif,struct pbuf *p)
{
err_t errval;
struct pbuf *q;
uint8_t *buffer = (uint8_t *)(heth.TxDesc->Buffer1Addr);
__IO ETH_DMADescTypeDef *DmaTxDesc;
uint32_t framelength = 0;
uint32_t bufferoffset = 0;
uint32_t byteslefttocopy = 0;
uint32_t payloadoffset = 0;
DmaTxDesc = heth.TxDesc;
bufferoffset = 0;
/* copy frame from pbufs to driver buffers */
for(q = p; q != NULL; q = q->next)
{
/* Is this buffer available? If not,goto error */
if((DmaTxDesc->Status & ETH_DMATXDESC_OWN) != (uint32_t)RESET)
{
errval = ERR_USE;
goto error;
}
/* Get bytes in current lwIP buffer */
byteslefttocopy = q->len;
payloadoffset = 0;
/* Check if the length of data to copy is bigger than Tx buffer size*/
while( (byteslefttocopy + bufferoffset) > ETH_TX_BUF_SIZE )
{
/* copy data to Tx buffer*/
memcpy( (uint8_t*)((uint8_t*)buffer + bufferoffset),(uint8_t*)((uint8_t*)q->payload + payloadoffset),(ETH_TX_BUF_SIZE - bufferoffset) );
/* Point to next descriptor */
DmaTxDesc = (ETH_DMADescTypeDef *)(DmaTxDesc->Buffer2NextDescAddr);
/* Check if the buffer is available */
if((DmaTxDesc->Status & ETH_DMATXDESC_OWN) != (uint32_t)RESET)
{
errval = ERR_USE;
goto error;
}
buffer = (uint8_t *)(DmaTxDesc->Buffer1Addr);
byteslefttocopy = byteslefttocopy - (ETH_TX_BUF_SIZE - bufferoffset);
payloadoffset = payloadoffset + (ETH_TX_BUF_SIZE - bufferoffset);
framelength = framelength + (ETH_TX_BUF_SIZE - bufferoffset);
bufferoffset = 0;
}
/* copy the remaining bytes */
memcpy( (uint8_t*)((uint8_t*)buffer + bufferoffset),byteslefttocopy );
bufferoffset = bufferoffset + byteslefttocopy;
framelength = framelength + byteslefttocopy;
}
/* Prepare transmit descriptors to give to DMA */
HAL_ETH_TransmitFrame(&heth,framelength);
errval = ERR_OK;
error:
/* When Transmit Underflow flag is set,clear it and issue a Transmit Poll Demand to resume transmission */
if ((heth.Instance->DMASR & ETH_DMASR_TUS) != (uint32_t)RESET)
{
/* Clear TUS ETHERNET DMA flag */
heth.Instance->DMASR = ETH_DMASR_TUS;
/* Resume DMA transmission*/
heth.Instance->DMATPDR = 0;
}
return errval;
}
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