101 lines
3.0 KiB
C
101 lines
3.0 KiB
C
#ifndef GD_IO_H
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#define GD_IO_H 1
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#include <stdio.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#ifdef VMS
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# define Putchar gdPutchar
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#endif
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/*
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Group: Types
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typedef: gdIOCtx
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gdIOCtx structures hold function pointers for doing image IO.
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Most of the gd functions that read and write files, such as
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<gdImagePng> also have variants that accept a <gdIOCtx> structure;
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see <gdImagePngCtx> and <gdImageCreateFromJpegCtx>.
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Those who wish to provide their own custom routines to read and
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write images can populate a gdIOCtx structure with functions of
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their own devising to to read and write data. For image reading, the
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only mandatory functions are getC and getBuf, which must return the
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number of characters actually read, or a negative value on error or
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EOF. These functions must read the number of characters requested
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unless at the end of the file.
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For image writing, the only mandatory functions are putC and putBuf,
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which return the number of characters written; these functions must
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write the number of characters requested except in the event of an
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error. The seek and tell functions are only required in conjunction
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with the gd2 file format, which supports quick loading of partial
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images. The gd_free function will not be invoked when calling the
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standard Ctx functions; it is an implementation convenience when
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adding new data types to gd. For examples, see gd_png.c, gd_gd2.c,
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gd_jpeg.c, etc., all of which rely on gdIOCtx to implement the
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standard image read and write functions.
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> typedef struct gdIOCtx
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> {
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> int (*getC) (struct gdIOCtx *);
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> int (*getBuf) (struct gdIOCtx *, void *, int wanted);
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>
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> void (*putC) (struct gdIOCtx *, int);
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> int (*putBuf) (struct gdIOCtx *, const void *, int wanted);
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>
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> // seek must return 1 on SUCCESS, 0 on FAILURE. Unlike fseek!
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> int (*seek) (struct gdIOCtx *, const int);
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> long (*tell) (struct gdIOCtx *);
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>
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> void (*gd_free) (struct gdIOCtx *);
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> } gdIOCtx;
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*/
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typedef struct gdIOCtx {
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int (*getC)(struct gdIOCtx *);
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int (*getBuf)(struct gdIOCtx *, void *, int);
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void (*putC)(struct gdIOCtx *, int);
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int (*putBuf)(struct gdIOCtx *, const void *, int);
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/* seek must return 1 on SUCCESS, 0 on FAILURE. Unlike fseek! */
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int (*seek)(struct gdIOCtx *, const int);
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long (*tell)(struct gdIOCtx *);
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void (*gd_free)(struct gdIOCtx *);
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void *data;
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} gdIOCtx;
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typedef struct gdIOCtx *gdIOCtxPtr;
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void Putword(int w, gdIOCtx *ctx);
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void Putchar(int c, gdIOCtx *ctx);
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void gdPutC(const unsigned char c, gdIOCtx *ctx);
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int gdPutBuf(const void *, int, gdIOCtx *);
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void gdPutWord(int w, gdIOCtx *ctx);
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void gdPutInt(int w, gdIOCtx *ctx);
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int gdGetC(gdIOCtx *ctx);
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int gdGetBuf(void *, int, gdIOCtx *);
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int gdGetByte(int *result, gdIOCtx *ctx);
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int gdGetWord(int *result, gdIOCtx *ctx);
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int gdGetWordLSB(signed short int *result, gdIOCtx *ctx);
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int gdGetInt(int *result, gdIOCtx *ctx);
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int gdGetIntLSB(signed int *result, gdIOCtx *ctx);
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int gdSeek(gdIOCtx *ctx, const int offset);
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long gdTell(gdIOCtx *ctx);
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#ifdef __cplusplus
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}
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#endif
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#endif
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