C language implements storing and retrieving data in the buffer

//When accessing data, it is best to add a mutex lock to prevent exceptions

unsigned char m_data[8*1024];
int m_max = 8*1024;
int m_read = 0;
int m_write = 0;
int m_used = 0;

int putdata(uint8_t *data, int length)
{
    
    	
	if (m_used + length > m_max)
		return 0;
		
	if (m_write+length <= m_max) {
    
    
		memcpy (m_data+m_write, data, length);
		m_write += length;
	} else {
    
    
		int left;
		left = m_max-m_write;
		memcpy (m_data+m_write, data, left);
		memcpy (m_data, (uint8_t *)data+left, length-left);
		m_write = length-left;
	}
	if (m_write >= m_max)
		m_write = 0;
	m_used += length;
	return length;
}

int getdata(uint8_t *data, int length)
{
    
    
	if (m_used < length)
		return 0;

	if (m_read+length <= m_max) {
    
    
		memcpy (data, m_data+m_read, length);
		m_read += length;
	} else {
    
    
		int left;
		left = m_max-m_read;
		memcpy (data, m_data+m_read, left);
		memcpy ((uint8_t *)data+left, m_data, length-left);
		m_read = length-left;
	}
	if (m_read >= m_max)
		m_read = 0;
	m_used -= length;

	return length;
}