现使用芯片stm32f407，通过串口3接收到一串数据，暂存到数组avail_data中，现需要写一个函数能通过串口1将avail_data储存的数据发出一条出来

以下是一个参考代码，可以根据具体情况进行修改：

#include "stm32f4xx_hal.h"

#define UART3_RX_BUFFER_SIZE  128   // 串口3接收缓存大小
#define UART1_TX_BUFFER_SIZE  128   // 串口1发送缓存大小

UART_HandleTypeDef huart3;
UART_HandleTypeDef huart1;

uint8_t uart3_rx_buffer[UART3_RX_BUFFER_SIZE];  // 串口3接收缓存
uint8_t uart1_tx_buffer[UART1_TX_BUFFER_SIZE];  // 串口1发送缓存

uint16_t uart3_rx_index = 0;   // 串口3接收缓存索引
uint16_t uart1_tx_index = 0;   // 串口1发送缓存索引

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart == &huart3)   // 如果是串口3接收中断
    {
        // 将接收到的数据存入缓存
        uart3_rx_buffer[uart3_rx_index++] = huart3.Instance->DR;

        if (uart3_rx_index >= UART3_RX_BUFFER_SIZE)   // 如果缓存已满
        {
            uart3_rx_index = 0;
        }

        // 继续接收
        HAL_UART_Receive_IT(&huart3, &uart3_rx_buffer[uart3_rx_index], 1);
    }
}

void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
    if (huart == &huart1)   // 如果是串口1发送中断
    {
        // 发送完一条数据后继续发送下一条数据
        if (uart1_tx_index > 0)
        {
            HAL_UART_Transmit_IT(&huart1, &uart1_tx_buffer[--uart1_tx_index], 1);
        }
    }
}

void send_data_via_uart1(uint8_t *data, uint16_t length)
{
    // 将数据存入发送缓存
    for (int i = 0; i < length; i++)
    {
        uart1_tx_buffer[uart1_tx_index++] = data[i];

        if (uart1_tx_index >= UART1_TX_BUFFER_SIZE)   // 如果缓存已满
        {
            uart1_tx_index = UART1_TX_BUFFER_SIZE - 1;
            break;
        }
    }

    // 如果串口1当前没有在发送数据，则立即开始发送
    if (huart1.gState == HAL_UART_STATE_READY)
    {
        HAL_UART_Transmit_IT(&huart1, &uart1_tx_buffer[--uart1_tx_index], 1);
    }
}

int main(void)
{
    HAL_Init();

    __HAL_RCC_GPIOA_CLK_ENABLE();
    __HAL_RCC_GPIOB_CLK_ENABLE();

    GPIO_InitTypeDef GPIO_InitStruct;

    // 配置串口3的GPIO引脚
    GPIO_InitStruct.Pin = GPIO_PIN_10 | GPIO_PIN_11;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART3;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

    // 配置串口1的GPIO引脚
    GPIO_InitStruct.Pin = GPIO_PIN_9 | GPIO_PIN_10;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
    GPIO_InitStruct.Alternate = GPIO_AF7_USART1;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    // 配置串口3
    huart3.Instance = USART3;
    huart3.Init.BaudRate = 115200;
    huart3.Init.WordLength = UART_WORDLENGTH_8B;
    huart3.Init.StopBits = UART_STOPBITS_1;
    huart3.Init.Parity = UART_PARITY_NONE;
    huart3.Init.Mode = UART_MODE_RX;
    huart3.Init.HwFlowCtl = UART_HWCONTROL_NONE;
    huart3.Init.OverSampling = UART_OVERSAMPLING_16;
    HAL_UART_Init(&huart3);

    // 配置串口1
    huart1.Instance = USART1;
    huart1.Init.BaudRate = 115200;
    huart1.Init.WordLength = UART_WORDLENGTH_8B;
    huart1.Init.StopBits = UART_STOPBITS_1;
    huart1.Init.Parity = UART_PARITY_NONE;
    huart1.Init.Mode = UART_MODE_TX;
    huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
    huart1.Init.OverSampling = UART_OVERSAMPLING_16;
    HAL_UART_Init(&huart1);

    // 启动串口3接收中断
    HAL_UART_Receive_IT(&huart3, &uart3_rx_buffer[uart3_rx_index], 1);

    while (1)
    {
        // 如果串口3接收到了数据，则将数据发送出去
        if (uart3_rx_index > 0)
        {
            send_data_via_uart1(uart3_rx_buffer, uart3_rx_index);
            uart3_rx_index = 0;
        }
    }
}