HTML Tidy  5.4.0
The HTACG Tidy HTML Project
Memory Allocation

Tidy uses a user provided allocator for all memory allocations. More...

Data Structures

struct  _TidyAllocator
 An allocator. More...
struct  _TidyAllocatorVtbl
 An allocator's function table. More...


typedef struct _TidyAllocator TidyAllocator
 The allocator. More...
typedef struct _TidyAllocatorVtbl TidyAllocatorVtbl
 The allocators function table. More...
typedef void(TIDY_CALLTidyFree) (void *buf)
 Callback for "free" replacement. More...
typedef void *(TIDY_CALLTidyMalloc) (size_t len)
 Callback for "malloc" replacement. More...
typedef void(TIDY_CALLTidyPanic) (ctmbstr mssg)
 Callback for "out of memory" panic state. More...
typedef void *(TIDY_CALLTidyRealloc) (void *buf, size_t len)
 Callback for "realloc" replacement. More...


Bool TIDY_CALL tidySetFreeCall (TidyFree ffree)
 Give Tidy a free() replacement. More...
Bool TIDY_CALL tidySetMallocCall (TidyMalloc fmalloc)
 Give Tidy a malloc() replacement. More...
Bool TIDY_CALL tidySetPanicCall (TidyPanic fpanic)
 Give Tidy an "out of memory" handler. More...
Bool TIDY_CALL tidySetReallocCall (TidyRealloc frealloc)
 Give Tidy a realloc() replacement. More...

Detailed Description

Tidy uses a user provided allocator for all memory allocations.

If this allocator is not provided, then a default allocator is used which simply wraps standard C malloc/free calls. These wrappers call the panic function upon any failure. The default panic function prints an out of memory message to stderr, and calls exit(2).

For applications in which it is unacceptable to abort in the case of memory allocation, then the panic function can be replaced with one which longjmps() out of the tidy code. For this to clean up completely, you should be careful not to use any tidy methods that open files as these will not be closed before panic() is called.

TODO: associate file handles with tidyDoc and ensure that tidyDocRelease() can close them all.

Calling the withAllocator() family ( tidyCreateWithAllocator, tidyBufInitWithAllocator, tidyBufAllocWithAllocator) allow settings custom allocators).

All parts of the document use the same allocator. Calls that require a user provided buffer can optionally use a different allocator.

For reference in designing a plug-in allocator, most allocations made by tidy are less than 100 bytes, corresponding to attribute names/values, etc.

There is also an additional class of much larger allocations which are where most of the data from the lexer is stored. (It is not currently possible to use a separate allocator for the lexer, this would be a useful extension).

In general, approximately 1/3rd of the memory used by tidy is freed during the parse, so if memory usage is an issue then an allocator that can reuse this memory is a good idea.

Data Structure Documentation

struct _TidyAllocator

An allocator.

To create your own allocator, do something like the following:

typedef struct _MyAllocator {
...other custom allocator state...
} MyAllocator;
void* MyAllocator_alloc(TidyAllocator *base, void *block, size_t nBytes)
MyAllocator *self = (MyAllocator*)base;
static const TidyAllocatorVtbl MyAllocatorVtbl = {
myAllocator allocator;
TidyDoc doc;
allocator.base.vtbl = &MyAllocatorVtbl;
...initialise allocator specific state...
doc = tidyCreateWithAllocator(&allocator);

Although this looks slightly long winded, the advantage is that to create a custom allocator you simply need to set the vtbl pointer correctly. The vtbl itself can reside in static/global data, and hence does not need to be initialised each time an allocator is created, and furthermore the memory is shared amongst all created allocators.

Definition at line 225 of file tidy.h.

Data Fields
const TidyAllocatorVtbl * vtbl
struct _TidyAllocatorVtbl

An allocator's function table.

All functions here must be provided.

Definition at line 167 of file tidy.h.

Public Member Functions

void *TIDY_CALLalloc (TidyAllocator *self, size_t nBytes)
 Called to allocate a block of nBytes of memory. More...
void *TIDY_CALLrealloc (TidyAllocator *self, void *block, size_t nBytes)
 Called to resize (grow, in general) a block of memory. More...
 void (TIDY_CALL *free)(TidyAllocator *self
 Called to free a previously allocated block of memory. More...
 void (TIDY_CALL *panic)(TidyAllocator *self
 Called when a panic condition is detected. More...

Data Fields

ctmbstr msg

Member Function Documentation

void* TIDY_CALL* _TidyAllocatorVtbl::alloc ( TidyAllocator self,
size_t  nBytes 

Called to allocate a block of nBytes of memory.

void* TIDY_CALL* _TidyAllocatorVtbl::realloc ( TidyAllocator self,
void block,
size_t  nBytes 

Called to resize (grow, in general) a block of memory.

Must support being called with NULL.

_TidyAllocatorVtbl::void ( TIDY_CALL free)

Called to free a previously allocated block of memory.

_TidyAllocatorVtbl::void ( TIDY_CALL panic)

Called when a panic condition is detected.

Must support block == NULL. This function is not called if either alloc or realloc fails; it is up to the allocator to do this. Currently this function can only be called if an error is detected in the tree integrity via the internal function CheckNodeIntegrity(). This is a situation that can only arise in the case of a programming error in tidylib. You can turn off node integrity checking by defining the constant NO_NODE_INTEGRITY_CHECK during the build.

Field Documentation

void* _TidyAllocatorVtbl::block

Definition at line 175 of file tidy.h.

ctmbstr _TidyAllocatorVtbl::msg

Definition at line 186 of file tidy.h.

Typedef Documentation

typedef struct _TidyAllocator TidyAllocator

The allocator.

Definition at line 162 of file tidy.h.

The allocators function table.

Definition at line 157 of file tidy.h.

typedef void(TIDY_CALL * TidyFree) (void *buf)

Callback for "free" replacement.

Definition at line 234 of file tidy.h.

typedef void*(TIDY_CALL * TidyMalloc) (size_t len)

Callback for "malloc" replacement.

Definition at line 230 of file tidy.h.

typedef void(TIDY_CALL * TidyPanic) (ctmbstr mssg)

Callback for "out of memory" panic state.

Definition at line 236 of file tidy.h.

typedef void*(TIDY_CALL * TidyRealloc) (void *buf, size_t len)

Callback for "realloc" replacement.

Definition at line 232 of file tidy.h.

Function Documentation

Bool TIDY_CALL tidySetFreeCall ( TidyFree  ffree)

Give Tidy a free() replacement.

Bool TIDY_CALL tidySetMallocCall ( TidyMalloc  fmalloc)

Give Tidy a malloc() replacement.

Bool TIDY_CALL tidySetPanicCall ( TidyPanic  fpanic)

Give Tidy an "out of memory" handler.

Bool TIDY_CALL tidySetReallocCall ( TidyRealloc  frealloc)

Give Tidy a realloc() replacement.