BYTE SD_ReadBytes(DWORD sector,DWORD offset,BYTE* buf,WORD num){//读取若干字节
WORD SecReadCnt=0;
while(offset>=512){//计算偏移跳过的扇区
offset-=512;
sector++;
}
if(ReadBegin(sector++)!=0)
return 1;//进入读状态失败
while(offset--){//跳过offset个字节
SecReadCnt++;
SPI_ByteRW(0xFF);
}
while(num){//还有数据要读
while(num>0 && SecReadCnt<512){//还有数据要读并且本扇区未读完
*(buf++)=SPI_ByteRW(0xFF);
SecReadCnt++;
num--;
}
if(num==0){//读完毕
break;
}
else{//数据未读完，本扇区读结束
ReadEnd();
if(ReadBegin(sector++)!=0)
return 1;//进入下一扇区读状态失败
SecReadCnt=0;//本扇区字节计数清零
}
}
while((SecReadCnt++)<512){//跳过本扇区最后的字节
SPI_ByteRW(0xFF);
}
ReadEnd();
return 0;
}
MemoryData NetworkBuffer::ReadData(size_t len, DataReadingMode mode/* = DataReadingMode::AlwaysCopy*/)
{
assert(len <= ReadableCount());
if (mode == DataReadingMode::AlwaysCopy)
{
MemoryData result = MemoryData::CopyFrom(ReadBegin(), len);
Retrieve(len);
return result;
}
else
{
MemoryData result = MemoryData::FromStatic(ReadBegin(), len);
Retrieve(len);
return result;
}
}
BYTE SD_ReadOneSector(DWORD sector,BYTE* buf){//读一个扇区(buf为512字节)，成功返回0
WORD i;
if(ReadBegin(sector++)!=0)
return 1;//进入读状态失败
for(i=0;i<512;i++){//读512个数据
*(buf++)=SPI_ByteRW(0xFF);
}
ReadEnd();//退出读状态
return 0;
}
void NetworkBuffer::TryAdjust()
{
if (IsFull())
{
mStream.ReserveSize(Size() * 2);
}
else if (mReadIndex>= Size() / 2) //write
{
// move readable data to the front, make space inside buffer
size_t readable = ReadableCount();
Memory::SafeCopy(mStream.MutablePtr(), mStream.Length(), ReadBegin(), readable);
mReadIndex = 0;
mWriteIndex = mReadIndex + readable;
assert(readable == ReadableCount());
}
}
HeapString NetworkBuffer::ReadString(size_t len)
{
HeapString result((const char*)ReadBegin(), len);
Retrieve(len);
return result;
}
StringRef NetworkBuffer::ReadStringRef(size_t len)
{
StringRef result((const char*)ReadBegin(), len);
Retrieve(len);
return result;
}
void NetworkBuffer::RetrieveUntil(const byte* end)
{
assert(ReadBegin() <= end);
assert(end <= WriteBegin());
Retrieve(end - ReadBegin());
}