#include "libNPK_StdAfx.h"
#include "libNPK_FileStream.h"
#include "libNPK_Errors.h"

#include "libEncrypt_CRC32.h"

namespace NPK
{

CFileStream::CFileStream(CNPKFile* pNPKFile, HANDLE hFile, const FileItemBaseInfo& baseFileInfo)
	: m_pNPKFile(pNPKFile)
	, m_hFileandle(hFile)
	, m_fileName(baseFileInfo.keyName)
	, m_fileOffset(baseFileInfo.fileOffset)
	, m_fileSize(baseFileInfo.fileSize)
	, m_currentOffset(0)
{

}

CFileStream::~CFileStream()
{

}

uint32_t CFileStream::read(void* buffer, uint32_t size)
{
	if(isEOF())
	{
		return 0; // End of file
	}

	DWORD dwOffset = m_fileOffset + m_currentOffset;
	if (dwOffset != ::SetFilePointer(m_hFileandle, dwOffset, NULL, FILE_BEGIN))
	{
		setLastError(NPK_ERR_FILE_READ, "WinErr=%d", ::GetLastError());
		return 0; // Failed to set file pointer
	}

	DWORD dwRemainBytes = m_fileSize - m_currentOffset;
	DWORD dwToRead = (size < dwRemainBytes) ? size : dwRemainBytes;

	DWORD dwBytesRead = 0;
	if(!::ReadFile(m_hFileandle, buffer, dwToRead, &dwBytesRead, NULL))
	{
		setLastError(NPK_ERR_FILE_READ, "WinErr=%d", ::GetLastError());
		return 0; // Failed to read file
	}
	
	m_currentOffset += dwBytesRead;
	return dwBytesRead;
}

bool CFileStream::seek(uint32_t offset)
{
	if(offset > m_fileSize)
	{
		setLastError(NPK_ERR_FILE_READ, "Seek offset %u exceeds file size %u", offset, m_fileSize);
		return false; // Seek offset exceeds file size
	}
	m_currentOffset = offset;
	return true;
}

uint32_t CFileStream::crc32(void)
{
	if (m_crc32Calculated) return m_crc32; // CRC32 already calculated

	const size_t kBufferSize = 1024*4;
	uint8_t pTempBuffer[kBufferSize];

	uint32_t currentOffset = m_currentOffset;
	m_currentOffset = 0;
	m_crc32 = 0;

	// Read the entire file to calculate CRC32
	uint32_t bytesRead = 0;
	while ((bytesRead = read(pTempBuffer, kBufferSize)) > 0)
	{
		m_crc32 = crcMemory32(pTempBuffer, bytesRead, m_crc32);
	}
	m_currentOffset = currentOffset;
	m_crc32Calculated = true;
	return m_crc32;
}

}