Opencv: cvmemstorage

 

Opencv: cvmemstorage

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1. dynamic memory storage and operation functions

Cvmemstorage

Typedef struct cvmemstorage

{

Struct cvmemblock * bottom;

Struct cvmemblock * top;

Struct cvmemstorage * parent;

Int block_size;

Int free_space;

} Cvmemstorage;

Memory is an underlying structure that can be used to store dynamic growth data structures such as sequences, outlines, graphs, and subpartitions. It consists of a series of memory blocks of the same size. The list-based bottom domain refers to the first column, and the top domain refers to the block currently pointed to, but not necessarily the end of the column. all blocks (including bottom, excluding top) between bottom and top are fully occupied; all blocks (including block tails, excluding top) between top and column tails) it is empty, while the top block itself occupies part of the space-free_space refers to the number of remaining blank characters in the top block. Newly allocated memory buffer (or displayed through
Cvmemstoragealloc function allocation, or hidden advanced function allocation through cvseqpush, cvgraphaddedge, etc.) always starts from the remaining part of the current block (that is, the top block, if the remaining part meets the requirements (the allocation size is sufficient ). After the allocation, free_space reduces the size of the newly allocated memory, and some additional sizes used to save the appropriate column type. When the remaining space of the top block cannot meet the size of the allocated block (buffer zone), the next storage block of the top block is set to the current block (New top block) -- free_space is set to the size of the entire block previously allocated. If no empty storage block exists (that is, the top block is at the end of the column), you must assign a new block (or inherit from the parent). See
Cvcreatechildmemstorage) and add the block to the end of the column. As a result, memory storage is like a stack. Bottom points to the bottom of the stack, and (top, free_space) points to the top of the stack. Stack top can be saved through cvsavemstoragepos, restored to point through cvrestoremstoragepos, and reset through cvclearstorage.

Cvmemblock

Memory block structure

Typedef struct cvmemblock

{

Struct cvmemblock * Prev;

Struct cvmemblock * next;

} Cvmemblock;

Cvmemblock represents a separate memory block structure. The actual data in the memory block is stored after the header block (that is, there is a header pointing to the block header, which does not store data). Therefore, the I-th byte of the memory block can be obtained through the expression (char *) (mem_block_ptr + 1) [I. However, it is usually not necessary to directly obtain the domain of the storage structure.

Cvmemstoragepos

Memory block address

Typedef struct cvmemstoragepos

{

Cvmemblock * top;

Int free_space;

} Cvmemstoragepos;

This structure (as described below) saves the address of the top stack. The top stack can be saved through cvsavemstoragepos or cvrestoremstoragepos.

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Cvcreatememstorage

Create a memory block

Cvmemstorage * cvcreatememstorage (INT block_size = 0 );

Block_size: the size of the storage block in bytes. If the block size is 0 bytes, set this block to the default value. The current default size is 64 KB.

The cvcreatememstorage function creates a memory block and returns a pointer to the first part of the block. At first, the storage block is empty. All the domain values of the header (that is, header) are 0, except for block_size.

Cvreleasememstorage

Release memory blocks

Void cvreleasememstorage (cvmemstorage ** storage );

Storage: pointer to the released storage Block

The cvreleasememstorage function releases all storage (memory) blocks or returns them to their respective parents (if needed ). Next, release the header block (that is, release the block pointed to by the header pointer head = free (head) and clear the pointer pointing to the block (that is, head = NULL ). Clear the child blocks before releasing them as parent blocks.

Cvclearmemstorage

Clear memory block

Void cvclearmemstorage (cvmemstorage * storage );

Storage: storage Block

The function cvclearmemstorage places the top of the block to the header of the block (Note: Clear the content stored in the block ). This function does not release the memory (only clears the memory ). If the memory block has a parent memory block (I .e., a memory block has a parent-child relationship with it), the function returns all the blocks to its parent.

Cvmemstoragealloc

Allocate to memory buffer in the storage Block

Void * cvmemstoragealloc (cvmemstorage * storage, size_t size );

Storage: memory block.

Size: the size of the buffer.

The cvmemstoragealloc function allocates a memory buffer in the storage block. The size of the buffer cannot exceed the size of the memory block. Otherwise, a running error occurs. The buffer address is changed to the cv_struct_align byte (currently sizeof (double )).

Cvmemstorageallocstring

Assign a text string to the bucket

Typedef struct cvstring

{

Int Len;

Char * PTR;

}

Cvstring;

Cvstring cvmemstorageallocstring (cvmemstorage * storage, const char * PTR, int Len =-1 );

Storage: storage Block

PTR: String

Len: the length of the string ('\ 0' is not counted '). If the parameter is negative, the function calculates the length of the string.

The cvmemstorageallostring function creates a copy of a string in the bucket. It returns a structure that contains the length of a string (transmitted by the user or calculated) and a pointer to the copied string.

Cvsavememstoragepos

Location (address) of the memory block to be saved)

Void cvsavememstoragepos (const cvmemstorage * storage, cvmemstoragepos * POS );

Storage: memory block.

POs: the top position of the memory block.

The cvsavemstoragepos function saves the current location of the storage block to the POs parameter. The cvrestoremstoragepos function can further obtain the location (address ).

Cvrestorememstoragepos

Restore the location of a memory block

Void cvrestorememstoragepos (cvmemstorage * storage, cvmemstoragepos * POS );

Storage: memory block.

POs: Location of the new storage Block

The cvrestoremstoragepos function restores the memory block position through the POs parameter. This function and function cvclearmemstorage are the only way to release occupied memory blocks. Note: There is no way to release part of the memory occupied by the storage block.

From: http://blog.sina.com.cn/s/blog_672c5a470100j1cm.html