C++ AsyncFio::read方法代码示例

void Ps2File::cacheReadAhead() {
	if (_cacheOpRunning) {
		// there's already some cache read running
		if (fio.poll(_fd)) // did it finish?
			cacheReadSync(); // yes.
	}
	if ((!_cacheOpRunning) && ((_readBytesBlock >= CACHE_READ_THRESHOLD) || _stream) && fio.fioAvail()) {
		// the engine seems to do sequential reads and there are no other I/Os going on. read ahead.
		uint32 cachePosEnd = _cachePos + _bytesInCache;

		if (_cachePos > _filePos)
			return; // there was a seek in the meantime, don't cache.
		if (cachePosEnd - _filePos >= CACHE_FILL_MIN)
			return; // cache is full enough.
		if (cachePosEnd == _fileSize)
			return; // can't read beyond EOF.

		assert(cachePosEnd < _fileSize);

		if (_cachePos + _bytesInCache <= _filePos) {
			_cacheOfs = _bytesInCache = 0;
			_cachePos = cachePosEnd = _filePos & ~READ_ALIGN_MASK;
			assert(_filePos == _physFilePos);
		} else {
			uint32 cacheDiff = _filePos - _cachePos;
			assert(_bytesInCache >= cacheDiff);
			cacheDiff &= ~READ_ALIGN_MASK;
			_bytesInCache -= cacheDiff;
			_cachePos += cacheDiff;
			_cacheOfs = (_cacheOfs + cacheDiff) % CACHE_SIZE;
		}

		if (_physFilePos != cachePosEnd) {
			sioprintf("unexpected _physFilePos %d cache %d %d\n", _physFilePos, _cacheOfs, _bytesInCache);
			// assert(!(cachePosEnd & READ_ALIGN_MASK)); // romeo
			_physFilePos = fio.seek(_fd, cachePosEnd, SEEK_SET);
			if (_physFilePos != cachePosEnd) {
				sioprintf("cache seek error: seek to %d instead of %d, fs = %d\n", _physFilePos, cachePosEnd, _fileSize);
				return;
			}
		}

		uint32 cacheDest = (_cacheOfs + _bytesInCache) % CACHE_SIZE;
		uint32 cacheRead = CACHE_SIZE - _bytesInCache;
		if (cacheDest + cacheRead > CACHE_SIZE)
			cacheRead = CACHE_SIZE - cacheDest;
		if (cacheRead > MAX_READ_STEP)
			cacheRead = MAX_READ_STEP;

		assert((!(cacheRead & READ_ALIGN_MASK)) && cacheRead);

		_cacheOpRunning = true;
		fio.read(_fd, _cacheBuf + cacheDest, cacheRead);
	}
}

uint32 Ps2ReadFile::read(void *dest, uint32 len) {
	WaitSema(_sema);
	uint8 *destBuf = (uint8*)dest;
	if ((_filePos < _cachePos) || (_filePos + len > _cachePos + _bytesInCache))
		cacheReadSync(); // we have to read from CD, sync cache.

	while (len && (_filePos != _fileSize)) {
		if ((_filePos >= _cachePos) && (_filePos < _cachePos + _bytesInCache)) { // read from cache
			uint32 staPos = (_cacheOfs + (_filePos - _cachePos)) % CACHE_SIZE;
			uint32 cpyLen = _bytesInCache - (_filePos - _cachePos);
			if (cpyLen > len)
				cpyLen = len;
			if (staPos + cpyLen > CACHE_SIZE)
				cpyLen = CACHE_SIZE - staPos;

			assert(cpyLen);
			memcpy(destBuf, _cacheBuf + staPos, cpyLen);
			_filePos += cpyLen;
			destBuf += cpyLen;
			_readBytesBlock += len;
			len -= cpyLen;
		} else { // cache miss
			assert(!_cacheOpRunning);
			if (_physFilePos != _filePos) {
				if ((_filePos < _physFilePos) || (_filePos > _physFilePos + (CACHE_SIZE / 2)))
					_readBytesBlock = 0; // reset cache hit count

				_physFilePos = _filePos & ~READ_ALIGN_MASK;
				if (fio.seek(_fd, _physFilePos, SEEK_SET) != (int)_physFilePos)
					break; // read beyond EOF
			}

			int doRead = len + (_filePos - _physFilePos);
			doRead = (doRead + READ_ALIGN_MASK) & ~READ_ALIGN_MASK;

			if (doRead > MAX_READ_STEP)
				doRead = MAX_READ_STEP;
			if (doRead < 2048)
				doRead = 2048;

			fio.read(_fd, _cacheBuf, doRead);
			_cachePos = _physFilePos;
			_cacheOfs = 0;
			_bytesInCache = fio.sync(_fd);
			_physFilePos += _bytesInCache;
			if (!_bytesInCache)
				break; // EOF
		}
	}
	cacheReadAhead();
	SignalSema(_sema);
	return destBuf - (uint8*)dest;
}

bool Ps2File::open(const char *name, int mode) {
#if 1
	_fd = fio.open(name, mode);

	dbg_printf("open %s [%d]\n", name, _fd);

	if (_fd >= 0) {
		_mode = mode;
		_filePos = 0;

		if (_mode == O_RDONLY) {
			_fileSize = fio.seek(_fd, 0, SEEK_END);
			fio.seek(_fd, 0, SEEK_SET);
		}
		else
			_fileSize = 0;

		dbg_printf("  _mode = %x\n", _mode);
		dbg_printf("  _fileSize = %d\n", _fileSize);
		// dbg_printf("  _filePos = %d\n", _filePos);

		return true;
	}

	return false;
#else
	uint32 r;

	// hack: FIO does not reports size for RW (?)
	_fd = fio.open(name, O_RDONLY);
	if (_fd >= 0) {
		_fileSize = fio.seek(_fd, 0, SEEK_END);
		fio.seek(_fd, 0, SEEK_SET); /* rewind ! */

		if (_fileSize && mode != O_RDONLY) {
			fio.read(_fd, _cacheBuf, _fileSize);
			r = fio.sync(_fd);
			dbg_printf(" sz=%d, read=%d\n", _fileSize, r);
			assert(r == _fileSize);
		}

		fio.close(_fd);
	}
	else
		_fileSize = 0; /* new file */

	_fd = fio.open(name, mode);

	dbg_printf("open %s [%d]\n", name, _fd);

	if (_fd >= 0) {
		_mode = mode;
		_filePos = 0;

		if (_fileSize) { /* existing data */
			if (mode == O_RDONLY) {
				/* DANGER: for w* modes it will truncate your fine files */
				fio.seek(_fd, 0, SEEK_SET);
			}
			else if (_mode & O_APPEND) {
				fio.seek(_fd, 0, _fileSize);
				_filePos = _fileSize;
			}
			#if 0 /* file already trunc'd when opened as w* -> moved up */
			if (mode != O_RDONLY) {
				fio.read(_fd, _cacheBuf, _fileSize);
				r = fio.sync(_fd);
				dbg_printf(" sz=%d, read=%d\n", _fileSize, r);
				assert(r == _fileSize);
				// _fileSize = fio.seek(_fd, 0, SEEK_END);
			}
			#endif
		}

		dbg_printf("  _mode = %x\n", _mode);
		dbg_printf("  _fileSize = %d\n", _fileSize);
		dbg_printf("  _filePos = %d\n", _filePos);

		return true;
	} else
		return false;
#endif
}