kits/tracker/AttributeStream.h

/*
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*/

//	attribute streams allow copying/filtering/transformation of attributes
//	between file and/or memory nodes
//
//	for example one can use constructs of nodes like:
//
// 	destinationNode << transformer << buffer << filter << sourceNode
//
//	transformer may for instance perform endian-swapping or offsetting of
//	a B_RECT attribute filter may withold certain attributes buffer is a
//	memory allocated snapshot of attributes, may be repeatedly streamed into
//	other files, buffers
//
//	In addition to the whacky (but usefull) << syntax, calls like Read, Write
//	are also available
#ifndef _ATTRIBUTE_STREAM_H
#define _ATTRIBUTE_STREAM_H


#include <ObjectList.h>
#include <Node.h>
#include <Rect.h>
#include <String.h>
#include <TypeConstants.h>

#include <fs_attr.h>


namespace BPrivate {

struct AttributeTemplate {
	// used for read-only attribute source
	const char* fAttributeName;
	uint32 fAttributeType;
	off_t fSize;
	const char* fBits;
};


class AttributeInfo {
	// utility class for internal attribute description
public:
	AttributeInfo();
	AttributeInfo(const AttributeInfo& other);
	AttributeInfo(const char* name, attr_info info);
	AttributeInfo(const char* name, uint32 type, off_t size);

	void SetTo(const AttributeInfo& other);
	void SetTo(const char* name, attr_info info);
	void SetTo(const char* name, uint32 type, off_t size);
	const char* Name() const;
	uint32 Type() const;
	off_t Size() const;

private:
	BString fName;
	attr_info fInfo;
};


class AttributeStreamNode {
public:
	AttributeStreamNode();
	virtual ~AttributeStreamNode();

	AttributeStreamNode &operator<<(AttributeStreamNode &source);
		// workhorse call
		// to the outside makes this node a part of the stream, passing on
		// any data it has, gets, transforms, doesn't filter out
		//
		// under the hood sets up streaming into the next node; hooking
		// up source and destination, forces the stream head to start
		// streaming

	virtual void Rewind();
		// get ready to start all over again
	virtual void MakeEmpty() {}
		// remove any attributes the node may have

	virtual off_t Contains(const char*, uint32);
		// returns size of attribute if found

	virtual off_t Read(const char* name, const char* foreignName,
		uint32 type, off_t size, void* buffer, void (*swapFunc)(void*) = 0);
		// read from this node
	virtual off_t Write(const char* name, const char* foreignName,
		uint32 type, off_t size, const void* buffer);
		// write to this node

	// work calls
	virtual bool Drive();
		// node at the head of the stream makes the entire stream
		// feed it
	virtual const AttributeInfo* Next();
		// give me the next attribute in the stream
	virtual const char* Get();
		// give me the data of the attribute in the stream that was just
		// returned by Next assumes there is a buffering node somewhere on the
		// way to the source, from which the resulting buffer is borrowed
	virtual bool Fill(char* buffer) const;
		// fill the buffer with data of the attribute in the stream that was
		// just returned by next <buffer> is big enough to hold the entire
		// attribute data

	virtual bool CanFeed() const { return false; }
		// return true if can work as a source for the entire stream

private:
	bool Start();
		// utility call, used to start up the stream by finding the ultimate
		// target of the stream and calling Drive on it

	void Detach();

protected:
	AttributeStreamNode* fReadFrom;
	AttributeStreamNode* fWriteTo;
};


class AttributeStreamFileNode : public AttributeStreamNode {
	// handles reading and writing attributes to and from the
	// stream
public:
	AttributeStreamFileNode();
	AttributeStreamFileNode(BNode*);

	virtual void MakeEmpty();
	virtual void Rewind();
	virtual off_t Contains(const char* name, uint32 type);
	virtual off_t Read(const char* name, const char* foreignName, uint32 type,
		off_t size, void* buffer, void (*swapFunc)(void*) = 0);
	virtual off_t Write(const char* name, const char* foreignName, uint32 type,
		off_t size, const void* buffer);

	void SetTo(BNode*);

	BNode* Node() { return fNode; }

protected:
	virtual bool CanFeed() const { return true; }

	virtual bool Drive();
		// give me all the attributes, I'll write them into myself
	virtual const AttributeInfo* Next();
		// return the info for the next attribute I can read for you
	virtual const char* Get();
	virtual bool Fill(char* buffer) const;

private:
	AttributeInfo fCurrentAttr;
	BNode* fNode;

	typedef AttributeStreamNode _inherited;
};


class AttributeStreamMemoryNode : public AttributeStreamNode {
	// in memory attribute buffer; can be both target of writing and source
	// of reading at the same time
public:
	AttributeStreamMemoryNode();

	virtual void MakeEmpty();
	virtual off_t Contains(const char* name, uint32 type);
	virtual off_t Read(const char* name, const char* foreignName,
		uint32 type, off_t size, void* buffer, void (*swapFunc)(void*) = 0);
	virtual off_t Write(const char* name, const char* foreignName,
		uint32 type, off_t size, const void* buffer);

protected:
	virtual bool CanFeed() const { return true; }
	virtual void Rewind();
	virtual bool Drive();
	virtual const AttributeInfo* Next();
	virtual const char* Get();
	virtual bool Fill(char* buffer) const;

	class AttrNode {
	public:
		AttrNode(const char* name, uint32 type, off_t size, char* data)
		:
		fAttr(name, type, size),
		fData(data)
		{
		}

		~AttrNode()
		{
			delete[] fData;
		}

		AttributeInfo fAttr;
		char* fData;
	};

		// utility calls
	virtual AttrNode* BufferingGet();
	virtual AttrNode* BufferingGet(const char* name, uint32 type, off_t size);
	int32 Find(const char* name, uint32 type) const;

private:
	BObjectList<AttrNode> fAttributes;
	int32 fCurrentIndex;

	typedef AttributeStreamNode _inherited;
};


class AttributeStreamTemplateNode : public AttributeStreamNode {
	// in read-only memory attribute source
	// can only be used as a source for Next and Get
public:
	AttributeStreamTemplateNode(const AttributeTemplate*, int32 count);

	virtual off_t Contains(const char* name, uint32 type);

protected:
	virtual bool CanFeed() const { return true; }
	virtual void Rewind();
	virtual const AttributeInfo* Next();
	virtual const char* Get();
	virtual bool Fill(char* buffer) const;

	int32 Find(const char* name, uint32 type) const;

private:
	AttributeInfo fCurrentAttr;
	const AttributeTemplate* fAttributes;
	int32 fCurrentIndex;
	int32 fCount;

	typedef AttributeStreamNode _inherited;
};


class AttributeStreamFilterNode : public AttributeStreamNode {
	// filter node may not pass thru specified attributes
public:
	AttributeStreamFilterNode()
		{}
	virtual off_t Contains(const char* name, uint32 type);
	virtual off_t Read(const char* name, const char* foreignName,
		uint32 type, off_t size, void* buffer, void (*swapFunc)(void*) = 0);
	virtual off_t Write(const char* name, const char* foreignName,
		uint32 type, off_t size, const void* buffer);

protected:
	virtual bool Reject(const char* name, uint32 type, off_t size);
		// override to implement filtering
	virtual const AttributeInfo* Next();

private:
	typedef AttributeStreamNode _inherited;
};


class NamesToAcceptAttrFilter : public AttributeStreamFilterNode {
	// filter node that only passes thru attributes that match
	// a list of names
public:
	NamesToAcceptAttrFilter(const char**);

protected:
	virtual bool Reject(const char* name, uint32 type, off_t size);

private:
	const char** fNameList;
};


class SelectiveAttributeTransformer : public AttributeStreamNode {
	// node applies a transformation on specified attributes
public:
	SelectiveAttributeTransformer(const char* attributeName,
		bool (*)(const char*, uint32 , off_t , void*, void*), void* params);
	virtual ~SelectiveAttributeTransformer();

	virtual off_t Read(const char* name, const char* foreignName, uint32 type,
		off_t size, void* buffer, void (*swapFunc)(void*) = 0);

	virtual void Rewind();

protected:
	virtual bool WillTransform(const char* name, uint32 type, off_t size,
		const char* data) const;
		// override to implement filtering, should only return true if
		// transformation will occur
	virtual char* CopyAndApplyTransformer(const char* name, uint32 type,
		off_t size, const char* data);
		// makes a copy of data
	virtual bool ApplyTransformer(const char* name, uint32 type, off_t size,
		char* data);
		// transforms in place
	virtual const AttributeInfo* Next();
	virtual const char* Get();

private:
	AttributeInfo fCurrentAttr;
	const char* fAttributeNameToTransform;
	bool (*fTransformFunc)(const char*, uint32 , off_t , void*, void*);
	void* fTransformParams;

	BObjectList<char> fTransformedBuffers;

	typedef AttributeStreamNode _inherited;
};


template <class Type>
class AttributeStreamConstValue : public AttributeStreamNode {
public:
	AttributeStreamConstValue(const char* name, uint32 attributeType,
		Type value);

protected:
	virtual bool CanFeed() const { return true; }
	virtual void Rewind() { fRewound = true; }
	virtual const AttributeInfo* Next();
	virtual const char* Get();
	virtual bool Fill(char* buffer) const;

	int32 Find(const char* name, uint32 type) const;

private:
	AttributeInfo fAttr;
	Type fValue;
	bool fRewound;

	typedef AttributeStreamNode _inherited;
};


template<class Type>
AttributeStreamConstValue<Type>::AttributeStreamConstValue(const char* name,
	uint32 attributeType, Type value)
	:
	fAttr(name, attributeType, sizeof(Type)),
	fValue(value),
	fRewound(true)
{
}


template<class Type>
const AttributeInfo*
AttributeStreamConstValue<Type>::Next()
{
	if (!fRewound)
		return NULL;

	fRewound = false;
	return &fAttr;
}


template<class Type>
const char*
AttributeStreamConstValue<Type>::Get()
{
	return (const char*)&fValue;
}


template<class Type>
bool
AttributeStreamConstValue<Type>::Fill(char* buffer) const
{
	memcpy(buffer, &fValue, sizeof(Type));
	return true;
}


template<class Type>
int32
AttributeStreamConstValue<Type>::Find(const char* name, uint32 type) const
{
	if (strcmp(fAttr.Name(), name) == 0 && type == fAttr.Type())
		return 0;

	return -1;
}


class AttributeStreamBoolValue : public AttributeStreamConstValue<bool> {
public:
	AttributeStreamBoolValue(const char* name, bool value)
		:
		AttributeStreamConstValue<bool>(name, B_BOOL_TYPE, value)
	{
	}
};


class AttributeStreamInt32Value : public AttributeStreamConstValue<int32> {
public:
	AttributeStreamInt32Value(const char* name, int32 value)
		:
		AttributeStreamConstValue<int32>(name, B_INT32_TYPE, value)
	{
	}
};


class AttributeStreamInt64Value : public AttributeStreamConstValue<int64> {
public:
	AttributeStreamInt64Value(const char* name, int64 value)
		:
		AttributeStreamConstValue<int64>(name, B_INT64_TYPE, value)
	{
	}
};


class AttributeStreamRectValue : public AttributeStreamConstValue<BRect> {
public:
	AttributeStreamRectValue(const char* name, BRect value)
		:
		AttributeStreamConstValue<BRect>(name, B_RECT_TYPE, value)
	{
	}
};


class AttributeStreamFloatValue : public AttributeStreamConstValue<float> {
public:
	AttributeStreamFloatValue(const char* name, float value)
		:
		AttributeStreamConstValue<float>(name, B_FLOAT_TYPE, value)
	{
	}
};

} // namespace BPrivate

using namespace BPrivate;


#endif	// _ATTRIBUTE_STREAM_H