/****************************************************************************
*
* ftsystem.h
*
* FreeType low-level system interface definition (specification).
*
* Copyright (C) 1996-2020 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
#ifndef FTSYSTEM_H_
#define FTSYSTEM_H_
FT_BEGIN_HEADER
/**************************************************************************
*
* @section:
* system_interface
*
* @title:
* System Interface
*
* @abstract:
* How FreeType manages memory and i/o.
*
* @description:
* This section contains various definitions related to memory management
* and i/o access. You need to understand this information if you want to
* use a custom memory manager or you own i/o streams.
*
*/
/**************************************************************************
*
* M E M O R Y M A N A G E M E N T
*
*/
/**************************************************************************
*
* @type:
* FT_Memory
*
* @description:
* A handle to a given memory manager object, defined with an
* @FT_MemoryRec structure.
*
*/
typedef struct FT_MemoryRec_* FT_Memory;
/**************************************************************************
*
* @functype:
* FT_Alloc_Func
*
* @description:
* A function used to allocate `size` bytes from `memory`.
*
* @input:
* memory ::
* A handle to the source memory manager.
*
* size ::
* The size in bytes to allocate.
*
* @return:
* Address of new memory block. 0~in case of failure.
*
*/
typedef void*
(*FT_Alloc_Func)( FT_Memory memory,
long size );
/**************************************************************************
*
* @functype:
* FT_Free_Func
*
* @description:
* A function used to release a given block of memory.
*
* @input:
* memory ::
* A handle to the source memory manager.
*
* block ::
* The address of the target memory block.
*
*/
typedef void
(*FT_Free_Func)( FT_Memory memory,
void* block );
/**************************************************************************
*
* @functype:
* FT_Realloc_Func
*
* @description:
* A function used to re-allocate a given block of memory.
*
* @input:
* memory ::
* A handle to the source memory manager.
*
* cur_size ::
* The block's current size in bytes.
*
* new_size ::
* The block's requested new size.
*
* block ::
* The block's current address.
*
* @return:
* New block address. 0~in case of memory shortage.
*
* @note:
* In case of error, the old block must still be available.
*
*/
typedef void*
(*FT_Realloc_Func)( FT_Memory memory,
long cur_size,
long new_size,
void* block );
/**************************************************************************
*
* @struct:
* FT_MemoryRec
*
* @description:
* A structure used to describe a given memory manager to FreeType~2.
*
* @fields:
* user ::
* A generic typeless pointer for user data.
*
* alloc ::
* A pointer type to an allocation function.
*
* free ::
* A pointer type to an memory freeing function.
*
* realloc ::
* A pointer type to a reallocation function.
*
*/
struct FT_MemoryRec_
{
void* user;
FT_Alloc_Func alloc;
FT_Free_Func free;
FT_Realloc_Func realloc;
};
/**************************************************************************
*
* I / O M A N A G E M E N T
*
*/
/**************************************************************************
*
* @type:
* FT_Stream
*
* @description:
* A handle to an input stream.
*
* @also:
* See @FT_StreamRec for the publicly accessible fields of a given stream
* object.
*
*/
typedef struct FT_StreamRec_* FT_Stream;
/**************************************************************************
*
* @struct:
* FT_StreamDesc
*
* @description:
* A union type used to store either a long or a pointer. This is used
* to store a file descriptor or a `FILE*` in an input stream.
*
*/
typedef union FT_StreamDesc_
{
long value;
void* pointer;
} FT_StreamDesc;
/**************************************************************************
*
* @functype:
* FT_Stream_IoFunc
*
* @description:
* A function used to seek and read data from a given input stream.
*
* @input:
* stream ::
* A handle to the source stream.
*
* offset ::
* The offset of read in stream (always from start).
*
* buffer ::
* The address of the read buffer.
*
* count ::
* The number of bytes to read from the stream.
*
* @return:
* The number of bytes effectively read by the stream.
*
* @note:
* This function might be called to perform a seek or skip operation with
* a `count` of~0. A non-zero return value then indicates an error.
*
*/
typedef unsigned long
(*FT_Stream_IoFunc)( FT_Stream stream,
unsigned long offset,
unsigned char* buffer,
unsigned long count );
/**************************************************************************
*
* @functype:
* FT_Stream_CloseFunc
*
* @description:
* A function used to close a given input stream.
*
* @input:
* stream ::
* A handle to the target stream.
*
*/
typedef void
(*FT_Stream_CloseFunc)( FT_Stream stream );
/**************************************************************************
*
* @struct:
* FT_StreamRec
*
* @description:
* A structure used to describe an input stream.
*
* @input:
* base ::
* For memory-based streams, this is the address of the first stream
* byte in memory. This field should always be set to `NULL` for
* disk-based streams.
*
* size ::
* The stream size in bytes.
*
* In case of compressed streams where the size is unknown before
* actually doing the decompression, the value is set to 0x7FFFFFFF.
* (Note that this size value can occur for normal streams also; it is
* thus just a hint.)
*
* pos ::
* The current position within the stream.
*
* descriptor ::
* This field is a union that can hold an integer or a pointer. It is
* used by stream implementations to store file descriptors or `FILE*`
* pointers.
*
* pathname ::
* This field is completely ignored by FreeType. However, it is often
* useful during debugging to use it to store the stream's filename
* (where available).
*
* read ::
* The stream's input function.
*
* close ::
* The stream's close function.
*
* memory ::
* The memory manager to use to preload frames. This is set internally
* by FreeType and shouldn't be touched by stream implementations.
*
* cursor ::
* This field is set and used internally by FreeType when parsing
* frames. In particular, the `FT_GET_XXX` macros use this instead of
* the `pos` field.
*
* limit ::
* This field is set and used internally by FreeType when parsing
* frames.
*
*/
typedef struct FT_StreamRec_
{
unsigned char* base;
unsigned long size;
unsigned long pos;
FT_StreamDesc descriptor;
FT_StreamDesc pathname;
FT_Stream_IoFunc read;
FT_Stream_CloseFunc close;
FT_Memory memory;
unsigned char* cursor;
unsigned char* limit;
} FT_StreamRec;
/* */
FT_END_HEADER
#endif /* FTSYSTEM_H_ */
/* END */
