353 lines
8.3 KiB
C
353 lines
8.3 KiB
C
/****************************************************************************
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*
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* ftsystem.h
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*
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* FreeType low-level system interface definition (specification).
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*
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* Copyright (C) 1996-2021 by
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* David Turner, Robert Wilhelm, and Werner Lemberg.
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*
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* This file is part of the FreeType project, and may only be used,
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* modified, and distributed under the terms of the FreeType project
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* license, LICENSE.TXT. By continuing to use, modify, or distribute
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* this file you indicate that you have read the license and
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* understand and accept it fully.
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*
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*/
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#ifndef FTSYSTEM_H_
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#define FTSYSTEM_H_
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FT_BEGIN_HEADER
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/**************************************************************************
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*
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* @section:
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* system_interface
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*
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* @title:
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* System Interface
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*
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* @abstract:
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* How FreeType manages memory and i/o.
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*
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* @description:
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* This section contains various definitions related to memory management
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* and i/o access. You need to understand this information if you want to
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* use a custom memory manager or you own i/o streams.
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*
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*/
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/**************************************************************************
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*
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* M E M O R Y M A N A G E M E N T
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*
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*/
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/**************************************************************************
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*
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* @type:
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* FT_Memory
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*
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* @description:
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* A handle to a given memory manager object, defined with an
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* @FT_MemoryRec structure.
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*
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*/
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typedef struct FT_MemoryRec_* FT_Memory;
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/**************************************************************************
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*
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* @functype:
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* FT_Alloc_Func
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*
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* @description:
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* A function used to allocate `size` bytes from `memory`.
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*
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* @input:
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* memory ::
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* A handle to the source memory manager.
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*
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* size ::
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* The size in bytes to allocate.
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*
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* @return:
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* Address of new memory block. 0~in case of failure.
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*
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*/
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typedef void*
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(*FT_Alloc_Func)( FT_Memory memory,
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long size );
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/**************************************************************************
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*
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* @functype:
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* FT_Free_Func
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*
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* @description:
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* A function used to release a given block of memory.
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*
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* @input:
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* memory ::
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* A handle to the source memory manager.
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*
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* block ::
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* The address of the target memory block.
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*
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*/
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typedef void
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(*FT_Free_Func)( FT_Memory memory,
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void* block );
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/**************************************************************************
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*
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* @functype:
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* FT_Realloc_Func
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*
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* @description:
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* A function used to re-allocate a given block of memory.
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*
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* @input:
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* memory ::
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* A handle to the source memory manager.
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*
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* cur_size ::
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* The block's current size in bytes.
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*
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* new_size ::
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* The block's requested new size.
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*
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* block ::
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* The block's current address.
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*
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* @return:
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* New block address. 0~in case of memory shortage.
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*
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* @note:
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* In case of error, the old block must still be available.
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*
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*/
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typedef void*
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(*FT_Realloc_Func)( FT_Memory memory,
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long cur_size,
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long new_size,
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void* block );
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/**************************************************************************
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*
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* @struct:
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* FT_MemoryRec
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*
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* @description:
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* A structure used to describe a given memory manager to FreeType~2.
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*
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* @fields:
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* user ::
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* A generic typeless pointer for user data.
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*
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* alloc ::
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* A pointer type to an allocation function.
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*
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* free ::
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* A pointer type to an memory freeing function.
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*
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* realloc ::
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* A pointer type to a reallocation function.
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*
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*/
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struct FT_MemoryRec_
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{
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void* user;
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FT_Alloc_Func alloc;
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FT_Free_Func free;
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FT_Realloc_Func realloc;
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};
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/**************************************************************************
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*
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* I / O M A N A G E M E N T
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*
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*/
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/**************************************************************************
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*
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* @type:
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* FT_Stream
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*
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* @description:
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* A handle to an input stream.
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*
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* @also:
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* See @FT_StreamRec for the publicly accessible fields of a given stream
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* object.
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*
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*/
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typedef struct FT_StreamRec_* FT_Stream;
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/**************************************************************************
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*
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* @struct:
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* FT_StreamDesc
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*
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* @description:
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* A union type used to store either a long or a pointer. This is used
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* to store a file descriptor or a `FILE*` in an input stream.
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*
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*/
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typedef union FT_StreamDesc_
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{
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long value;
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void* pointer;
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} FT_StreamDesc;
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/**************************************************************************
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*
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* @functype:
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* FT_Stream_IoFunc
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*
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* @description:
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* A function used to seek and read data from a given input stream.
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*
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* @input:
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* stream ::
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* A handle to the source stream.
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*
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* offset ::
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* The offset of read in stream (always from start).
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*
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* buffer ::
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* The address of the read buffer.
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*
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* count ::
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* The number of bytes to read from the stream.
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*
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* @return:
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* The number of bytes effectively read by the stream.
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*
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* @note:
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* This function might be called to perform a seek or skip operation with
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* a `count` of~0. A non-zero return value then indicates an error.
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*
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*/
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typedef unsigned long
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(*FT_Stream_IoFunc)( FT_Stream stream,
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unsigned long offset,
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unsigned char* buffer,
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unsigned long count );
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/**************************************************************************
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*
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* @functype:
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* FT_Stream_CloseFunc
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*
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* @description:
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* A function used to close a given input stream.
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*
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* @input:
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* stream ::
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* A handle to the target stream.
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*
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*/
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typedef void
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(*FT_Stream_CloseFunc)( FT_Stream stream );
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/**************************************************************************
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*
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* @struct:
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* FT_StreamRec
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*
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* @description:
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* A structure used to describe an input stream.
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*
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* @input:
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* base ::
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* For memory-based streams, this is the address of the first stream
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* byte in memory. This field should always be set to `NULL` for
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* disk-based streams.
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*
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* size ::
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* The stream size in bytes.
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*
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* In case of compressed streams where the size is unknown before
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* actually doing the decompression, the value is set to 0x7FFFFFFF.
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* (Note that this size value can occur for normal streams also; it is
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* thus just a hint.)
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*
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* pos ::
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* The current position within the stream.
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*
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* descriptor ::
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* This field is a union that can hold an integer or a pointer. It is
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* used by stream implementations to store file descriptors or `FILE*`
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* pointers.
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*
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* pathname ::
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* This field is completely ignored by FreeType. However, it is often
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* useful during debugging to use it to store the stream's filename
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* (where available).
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*
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* read ::
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* The stream's input function.
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*
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* close ::
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* The stream's close function.
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*
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* memory ::
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* The memory manager to use to preload frames. This is set internally
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* by FreeType and shouldn't be touched by stream implementations.
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*
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* cursor ::
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* This field is set and used internally by FreeType when parsing
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* frames. In particular, the `FT_GET_XXX` macros use this instead of
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* the `pos` field.
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*
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* limit ::
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* This field is set and used internally by FreeType when parsing
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* frames.
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*
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*/
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typedef struct FT_StreamRec_
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{
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unsigned char* base;
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unsigned long size;
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unsigned long pos;
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FT_StreamDesc descriptor;
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FT_StreamDesc pathname;
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FT_Stream_IoFunc read;
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FT_Stream_CloseFunc close;
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FT_Memory memory;
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unsigned char* cursor;
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unsigned char* limit;
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} FT_StreamRec;
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/* */
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FT_END_HEADER
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#endif /* FTSYSTEM_H_ */
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/* END */
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