diff options
| -rw-r--r-- | yapf/blob.hpp | 95 |
1 files changed, 85 insertions, 10 deletions
diff --git a/yapf/blob.hpp b/yapf/blob.hpp index f05e6a77d..1a20f3ac2 100644 --- a/yapf/blob.hpp +++ b/yapf/blob.hpp @@ -3,6 +3,10 @@ #ifndef BLOB_HPP #define BLOB_HPP +/** Type-safe version of memcpy(). + * @param d destination buffer + * @param s source buffer + * @param num_items number of items to be copied (!not number of bytes!) */ template <class Titem_> FORCEINLINE void MemCpyT(Titem_* d, const Titem_* s, int num_items = 1) { @@ -18,51 +22,94 @@ FORCEINLINE void MemCpyT(Titem_* d, const Titem_* s, int num_items = 1) * module (DLL) where the blob was allocated * - no configurable allocation policy (how big blocks should be allocated) * - no extra ownership policy (i.e. 'copy on write') when blob is copied - * - no thread synchronization at all */ + * - no thread synchronization at all + * + * Internal member layout: + * 1. The only class member is pointer to the first item (see union ptr_u). + * 2. Allocated block contains the blob header (see CHdr) followed by the raw byte data. + * Always, when it allocates memory the allocated size is: + * sizeof(CHdr) + <data capacity> + * 3. Two 'virtual' members (m_size and m_max_size) are stored in the CHdr at beginning + * of the alloated block. + * 4. The pointer (in ptr_u) points behind the header (to the first data byte). + * When memory block is allocated, the sizeof(CHdr) it added to it. + * 5. Benefits of this layout: + * - items are accessed in the simplest possible way - just dereferencing the pointer, + * which is good for performance (assuming that data are accessed most often). + * - sizeof(blob) is the same as the size of any other pointer + * 6. Drawbacks of this layout: + * - the fact, that pointer to the alocated block is adjusted by sizeof(CHdr) before + * it is stored can lead to several confusions: + * - it is not common pattern so the implementation code is bit harder to read + * - valgrind can generate warning that allocated block is lost (not accessible) + * */ class CBlobBaseSimple { protected: + /** header of the allocated memory block */ struct CHdr { - int m_size; // actual blob size in bytes - int m_max_size; // maximum (allocated) size in bytes + int m_size; ///< actual blob size in bytes + int m_max_size; ///< maximum (allocated) size in bytes }; + /** type used as class member */ union { - int8 *m_pData; - CHdr *m_pHdr_1; + int8 *m_pData; ///< pointer to the first byte of data + CHdr *m_pHdr_1; ///< pointer just after the CHdr holding m_size and m_max_size } ptr_u; public: - static const int Ttail_reserve = 4; // four extra bytes will be always allocated and zeroed at the end + static const int Ttail_reserve = 4; ///< four extra bytes will be always allocated and zeroed at the end + /** default constructor - initializes empty blob */ FORCEINLINE CBlobBaseSimple() { InitEmpty(); } + /** copy constructor */ FORCEINLINE CBlobBaseSimple(const CBlobBaseSimple& src) { InitEmpty(); AppendRaw(src); } + /** destructor */ FORCEINLINE ~CBlobBaseSimple() { Free(); } protected: + /** initialize the empty blob by setting the ptr_u.m_pHdr_1 pointer to the static CHdr with + * both m_size and m_max_size containing zero */ FORCEINLINE void InitEmpty() { static CHdr hdrEmpty[] = {{0, 0}, {0, 0}}; ptr_u.m_pHdr_1 = &hdrEmpty[1]; } + /** initialize blob by attaching it to the given header followed by data */ FORCEINLINE void Init(CHdr* hdr) { ptr_u.m_pHdr_1 = &hdr[1]; } + /** blob header accessor - use it rather than using the pointer arithmetics directly - non-const version */ FORCEINLINE CHdr& Hdr() { return ptr_u.m_pHdr_1[-1]; } + /** blob header accessor - use it rather than using the pointer arithmetics directly - const version */ FORCEINLINE const CHdr& Hdr() const { return ptr_u.m_pHdr_1[-1]; } + /** return reference to the actual blob size - used when the size needs to be modified */ FORCEINLINE int& RawSizeRef() { return Hdr().m_size; }; public: + /** return true if blob doesn't contain valid data */ FORCEINLINE bool IsEmpty() const { return RawSize() == 0; } + /** return the number of valid data bytes in the blob */ FORCEINLINE int RawSize() const { return Hdr().m_size; }; + /** return the current blob capacity in bytes */ FORCEINLINE int MaxRawSize() const { return Hdr().m_max_size; }; + /** return pointer to the first byte of data - non-const version */ FORCEINLINE int8* RawData() { return ptr_u.m_pData; } + /** return pointer to the first byte of data - const version */ FORCEINLINE const int8* RawData() const { return ptr_u.m_pData; } #if 0 // reenable when needed + /** return the 32 bit CRC of valid data in the blob */ FORCEINLINE uint32 Crc32() const {return CCrc32::Calc(RawData(), RawSize());} #endif //0 + /** invalidate blob's data - doesn't free buffer */ FORCEINLINE void Clear() { RawSizeRef() = 0; } + /** free the blob's memory */ FORCEINLINE void Free() { if (MaxRawSize() > 0) {RawFree(&Hdr()); InitEmpty();} } + /** copy data from another blob - replaces any existing blob's data */ FORCEINLINE void CopyFrom(const CBlobBaseSimple& src) { Clear(); AppendRaw(src); } + /** overtake ownership of data buffer from the source blob - source blob will become empty */ FORCEINLINE void MoveFrom(CBlobBaseSimple& src) { Free(); ptr_u.m_pData = src.ptr_u.m_pData; src.InitEmpty(); } + /** swap buffers (with data) between two blobs (this and source blob) */ FORCEINLINE void Swap(CBlobBaseSimple& src) { int8 *tmp = ptr_u.m_pData; ptr_u.m_pData = src.ptr_u.m_pData; src.ptr_u.m_pData = tmp; } + /** append new bytes at the end of existing data bytes - reallocates if necessary */ FORCEINLINE void AppendRaw(int8 *p, int num_bytes) { assert(p != NULL); @@ -73,6 +120,7 @@ public: } } + /** append bytes from given source blob to the end of existing data bytes - reallocates if necessary */ FORCEINLINE void AppendRaw(const CBlobBaseSimple& src) { if (!src.IsEmpty()) @@ -164,6 +212,13 @@ public: } }; +/** Blob - simple dynamic Titem_ array. Titem_ (template argument) is a placeholder for any type. + * Titem_ can be any integral type, pointer, or structure. Using Blob instead of just plain C array + * simplifies the resource management in several ways: + * 1. When adding new item(s) it automatically grows capacity if needed. + * 2. When variable of type Blob comes out of scope it automatically frees the data buffer. + * 3. Takes care about the actual data size (number of used items). + * 4. Dynamically constructs only used items (as opposite of static array which constructs all items) */ template <class Titem_, class Tbase_ = CBlobBaseSimple> class CBlobT : public CBlobBaseSimple { // make template arguments public: @@ -173,15 +228,25 @@ public: static const int Titem_size = sizeof(Titem); + /** Default constructor - makes new Blob ready to accept any data */ FORCEINLINE CBlobT() : Tbase() {} + /** Copy constructor - make new blob to become copy of the original (source) blob */ FORCEINLINE CBlobT(const Tbase& src) : Tbase(src) {assert((RawSize() % Titem_size) == 0);} + /** Destructor - ensures that allocated memory (if any) is freed */ FORCEINLINE ~CBlobT() { Free(); } + /** Check the validity of item index (only in debug mode) */ FORCEINLINE void CheckIdx(int idx) { assert(idx >= 0); assert(idx < Size()); } + /** Return pointer to the first data item - non-const version */ FORCEINLINE Titem* Data() { return (Titem*)RawData(); } + /** Return pointer to the first data item - const version */ FORCEINLINE const Titem* Data() const { return (const Titem*)RawData(); } + /** Return pointer to the idx-th data item - non-const version */ FORCEINLINE Titem* Data(int idx) { CheckIdx(idx); return (Data() + idx); } + /** Return pointer to the idx-th data item - const version */ FORCEINLINE const Titem* Data(int idx) const { CheckIdx(idx); return (Data() + idx); } + /** Return number of items in the Blob */ FORCEINLINE int Size() const { return (RawSize() / Titem_size); } + /** Free the memory occupied by Blob destroying all items */ FORCEINLINE void Free() { assert((RawSize() % Titem_size) == 0); @@ -193,12 +258,15 @@ public: } Tbase::Free(); } + /** Grow number of data items in Blob by given number - doesn't construct items */ FORCEINLINE Titem* GrowSizeNC(int num_items) { return (Titem*)GrowRawSize(num_items * Titem_size); } + /** Grow number of data items in Blob by given number - constructs new items (using Titem_'s default constructor) */ FORCEINLINE Titem* GrowSizeC(int num_items) { Titem* pI = GrowSizeNC(num_items); for (int i = num_items; i > 0; i--, pI++) new (pI) Titem(); } + /** Destroy given number of items and reduce the Blob's data size */ FORCEINLINE void ReduceSize(int num_items) { assert((RawSize() % Titem_size) == 0); @@ -211,18 +279,21 @@ public: // remove them ReduceRawSize(num_items * Titem_size); } + /** Append one data item at the end (calls Titem_'s default constructor) */ FORCEINLINE Titem* AppendNew() { - Titem& dst = *GrowSizeNC(1); - Titem* pNewItem = new (&dst) Titem(); + Titem& dst = *GrowSizeNC(1); // Grow size by one item + Titem* pNewItem = new (&dst) Titem(); // construct the new item by calling in-place new operator return pNewItem; } + /** Append the copy of given item at the end of Blob (using copy constructor) */ FORCEINLINE Titem* Append(const Titem& src) { - Titem& dst = *GrowSizeNC(1); - Titem* pNewItem = new (&dst) Titem(src); + Titem& dst = *GrowSizeNC(1); // Grow size by one item + Titem* pNewItem = new (&dst) Titem(src); // construct the new item by calling in-place new operator with copy ctor() return pNewItem; } + /** Add given items (ptr + number of items) at the end of blob */ FORCEINLINE Titem* Append(const Titem* pSrc, int num_items) { Titem* pDst = GrowSizeNC(num_items); @@ -231,6 +302,7 @@ public: while (pDst < pDstEnd) new (pDst++) Titem(*(pSrc++)); return pDstOrg; } + /** Remove item with the given index by replacing it by the last item and reducing the size by one */ FORCEINLINE void RemoveBySwap(int idx) { CheckIdx(idx); @@ -238,6 +310,7 @@ public: Titem* pRemoved = Data(idx); RemoveBySwap(pRemoved); } + /** Remove item given by pointer replacing it by the last item and reducing the size by one */ FORCEINLINE void RemoveBySwap(Titem* pItem) { Titem* pLast = Data(Size() - 1); @@ -252,6 +325,8 @@ public: // and reduce the raw blob size ReduceRawSize(Titem_size); } + /** Ensures that given number of items can be added to the end of Blob. Returns pointer to the + * first free (unused) item */ FORCEINLINE Titem* MakeFreeSpace(int num_items) { return (Titem*)MakeRawFreeSpace(num_items * Titem_size); } }; |