此文已由作者郑博授权网易云社区发布。
欢迎访问网易云社区，了解更多网易技术产品运营经验
#endif // _WIN32
}
class FileStream::FileStreamPrivate
{
public:
FileStreamPrivate(const FileName &fileName)
: file(InvalidFileHandle)
, name(fileName)
, readOnly(true)
{
}
FileHandle file;
FileNameHandle name;
bool readOnly;
};
////////////////////////////////////////////////////////////////////////////////
// public members
////////////////////////////////////////////////////////////////////////////////
FileStream::FileStream(FileName fileName, bool openReadOnly)
: d(new FileStreamPrivate(fileName))
{
// First try with read / write mode, if that fails, fall back to read only.
if(!openReadOnly)
d->file = openFile(fileName, false);
if(d->file != InvalidFileHandle)
d->readOnly = false;
else
d->file = openFile(fileName, true);
if(d->file == InvalidFileHandle)
{
# ifdef _WIN32
debug("Could not open file " + fileName.toString());
# else
debug("Could not open file " + String(static_cast(d->name)));
# endif
}
}
FileStream::~FileStream()
{
if(isOpen())
closeFile(d->file);
delete d;
}
FileName FileStream::name() const
{
return d->name;
}
ByteVector FileStream::readBlock(ulong length)
{
if(!isOpen()) {
debug("FileStream::readBlock() -- invalid file.");
return ByteVector::null;
}
if(length == 0)
return ByteVector::null;
const ulong streamLength = static_cast(FileStream::length());
if(length > bufferSize() && length > streamLength)
length = streamLength;
ByteVector buffer(static_cast(length));
const size_t count = readFile(d->file, buffer);
buffer.resize(static_cast(count));
return buffer;
}
void FileStream::writeBlock(const ByteVector &data)
{
if(!isOpen()) {
debug("FileStream::writeBlock() -- invalid file.");
return;
}
if(readOnly()) {
debug("FileStream::writeBlock() -- read only file.");
return;
}
writeFile(d->file, data);
}
void FileStream::insert(const ByteVector &data, ulong start, ulong replace)
{
if(!isOpen()) {
debug("FileStream::insert() -- invalid file.");
return;
}
if(readOnly()) {
debug("FileStream::insert() -- read only file.");
return;
}
if(data.size() == replace) {
seek(start);
writeBlock(data);
return;
}
else if(data.size() < replace) {
seek(start);
writeBlock(data);
removeBlock(start + data.size(), replace - data.size());
return;
}
// Woohoo! Faster (about 20%) than id3lib at last. I had to get hardcore
// and avoid TagLib's high level API for rendering just copying parts of
// the file that don't contain tag data.
//
// Now I'll explain the steps in this ugliness:
// First, make sure that we're working with a buffer that is longer than
// the *differnce* in the tag sizes. We want to avoid overwriting parts
// that aren't yet in memory, so this is necessary.
ulong bufferLength = bufferSize();
while(data.size() - replace > bufferLength)
bufferLength += bufferSize();
// Set where to start the reading and writing.
long readPosition = start + replace;
long writePosition = start;
ByteVector buffer = data;
ByteVector aboutToOverwrite(static_cast(bufferLength));
while(true)
{
// Seek to the current read position and read the data that we're about
// to overwrite. Appropriately increment the readPosition.
seek(readPosition);
const size_t bytesRead = readFile(d->file, aboutToOverwrite);
aboutToOverwrite.resize(bytesRead);
readPosition += bufferLength;
// Check to see if we just read the last block. We need to call clear()
// if we did so that the last write succeeds.
if(bytesRead < bufferLength)
clear();
// Seek to the write position and write our buffer. Increment the
// writePosition.
seek(writePosition);
writeBlock(buffer);
// We hit the end of the file.
if(bytesRead == 0)
break;
writePosition += buffer.size();
// Make the current buffer the data that we read in the beginning.
buffer = aboutToOverwrite;
}
}
void FileStream::removeBlock(ulong start, ulong length)
{
if(!isOpen()) {
debug("FileStream::removeBlock() -- invalid file.");
return;
}
ulong bufferLength = bufferSize();
long readPosition = start + length;
long writePosition = start;
ByteVector buffer(static_cast(bufferLength));
for(size_t bytesRead = -1; bytesRead != 0;)
{
seek(readPosition);
bytesRead = readFile(d->file, buffer);
readPosition += bytesRead;
// Check to see if we just read the last block. We need to call clear()
// if we did so that the last write succeeds.
if(bytesRead < buffer.size()) {
clear();
buffer.resize(bytesRead);
}
seek(writePosition);
writeFile(d->file, buffer);
writePosition += bytesRead;
}
truncate(writePosition);
}
bool FileStream::readOnly() const
{
return d->readOnly;
}
bool FileStream::isOpen() const
{
return (d->file != InvalidFileHandle);
}
void FileStream::seek(long offset, Position p)
{
if(!isOpen()) {
debug("FileStream::seek() -- invalid file.");
return;
}
#ifdef _WIN32
DWORD whence;
switch(p) {
case Beginning:
whence = FILE_BEGIN;
break;
case Current:
whence = FILE_CURRENT;
break;
case End:
whence = FILE_END;
break;
default:
debug("FileStream::seek() -- Invalid Position value.");
return;
}
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM)
LARGE_INTEGER distance = { 0 };
distance.QuadPart = offset;
if (!SetFilePointerEx(d->file, distance, NULL, whence))
#else
SetLastError(NO_ERROR);
SetFilePointer(d->file, offset, NULL, whence);
const int lastError = GetLastError();
if(lastError != NO_ERROR && lastError != ERROR_NEGATIVE_SEEK)
#endif
debug("FileStream::seek() -- Failed to set the file pointer.");
#else
int whence;
switch(p) {
case Beginning:
whence = SEEK_SET;
break;
case Current:
whence = SEEK_CUR;
break;
case End:
whence = SEEK_END;
break;
default:
debug("FileStream::seek() -- Invalid Position value.");
return;
}
fseek(d->file, offset, whence);
#endif
}
void FileStream::clear()
{
#ifdef _WIN32
// NOP
#else
clearerr(d->file);
#endif
}
long FileStream::tell() const
{
#ifdef _WIN32
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM)
LARGE_INTEGER distance = { 0 };
LARGE_INTEGER position = { 0 };
if (SetFilePointerEx(d->file, distance, &position, FILE_CURRENT)) {
return static_cast(position.QuadPart);
}
#else
SetLastError(NO_ERROR);
const DWORD position = SetFilePointer(d->file, 0, NULL, FILE_CURRENT);
if(GetLastError() == NO_ERROR) {
return static_cast(position);
}
#endif
else {
debug("FileStream::tell() -- Failed to get the file pointer.");
return 0;
}
#else
return ftell(d->file);
#endif
}
long FileStream::length()
{
if(!isOpen()) {
debug("FileStream::length() -- invalid file.");
return 0;
}
#ifdef _WIN32
#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM)
LARGE_INTEGER fileSize = { 0 };
if (GetFileSizeEx(d->file, &fileSize)) {
return static_cast(fileSize.QuadPart);
}
#else
SetLastError(NO_ERROR);
const DWORD fileSize = GetFileSize(d->file, NULL);
if (GetLastError() == NO_ERROR) {
return static_cast(fileSize);
}
#endif
else {
debug("FileStream::length() -- Failed to get the file size.");
return 0;
}
#else
const long curpos = tell();
seek(0, End);
const long endpos = tell();
seek(curpos, Beginning);
return endpos;
#endif
}
////////////////////////////////////////////////////////////////////////////////
// protected members
////////////////////////////////////////////////////////////////////////////////
void FileStream::truncate(long length)
{
#ifdef _WIN32
const long currentPos = tell();
seek(length);
SetLastError(NO_ERROR);
SetEndOfFile(d->file);
if(GetLastError() != NO_ERROR) {
debug("FileStream::truncate() -- Failed to truncate the file.");
}
seek(currentPos);
#else
const int error = ftruncate(fileno(d->file), length);
if(error != 0) {
debug("FileStream::truncate() -- Coundn't truncate the file.");
}
#endif
}
TagLib::uint FileStream::bufferSize()
{
return 1024;
}
为了便于调试，还需要修改taglib\toolkit\tdebuglistener.cpp，以便在调试直接在Output窗口输出调试信息，完整代码如下：
/*************************************************************************** copyright : (C) 2013 by Tsuda Kageyu email : [email protected] ***************************************************************************/ /*************************************************************************** * This library is free software; you can redistribute it and/or modify * * it under the terms of the GNU Lesser General Public License version * * 2.1 as published by the Free Software Foundation. * * * * This library is distributed in the hope that it will be useful, but * * WITHOUT ANY WARRANTY; without even the implied warranty of * * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * * Lesser General Public License for more details. * * * * You should have received a copy of the GNU Lesser General Public * * License along with this library; if not, write to the Free Software * * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * * 02110-1301 USA * * * * Alternatively, this file is available under the Mozilla Public * * License Version 1.1. You may obtain a copy of the License at * * http://www.mozilla.org/MPL/ * ***************************************************************************/ #include "tdebuglistener.h" #include #include #ifdef _WIN32 # include #endif using namespace TagLib; namespace { class DefaultListener : public DebugListener { public: virtual void printMessage(const String &msg) { #ifdef _WIN32 const wstring wstr = msg.toWString(); #if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP | WINAPI_PARTITION_SYSTEM) OutputDebugStringW(wstr.c_str()); #else const int len = WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), -1, NULL, 0, NULL, NULL); if(len != 0) { std::vector buf(len); WideCharToMultiByte(CP_ACP, 0, wstr.c_str(), -1, &buf[0], len, NULL, NULL); std::cerr << std::string(&buf[0]); } #endif #else std::cerr << msg; #endif } }; DefaultListener defaultListener; } namespace TagLib { DebugListener *debugListener = &defaultListener; DebugListener::DebugListener() { } DebugListener::~DebugListener() { } void setDebugListener(DebugListener *listener) { if(listener) debugListener = listener; else debugListener = &defaultListener; } }
最后，编译吧，骚年！！！
免费领取验证码、内容安全、短信发送、直播点播体验包及云服务器等套餐
更多网易技术、产品、运营经验分享请点击。
相关文章：
【推荐】 dubbo心跳机制 （3）
【推荐】 Android标题栏（2）
【推荐】 云计算的前世今生（下）