1 /****************************************************************************
2 
3 gif_lib_private.h - internal giflib routines and structures
4 
5 ****************************************************************************/
6 
7 #ifndef _GIF_LIB_PRIVATE_H
8 #define _GIF_LIB_PRIVATE_H
9 
10 #include "gif_lib.h"
11 #include "gif_hash.h"
12 
13 #define EXTENSION_INTRODUCER      0x21
14 #define DESCRIPTOR_INTRODUCER     0x2c
15 #define TERMINATOR_INTRODUCER     0x3b
16 
17 #define LZ_MAX_CODE         4095    /* Biggest code possible in 12 bits. */
18 #define LZ_BITS             12
19 
20 #define FLUSH_OUTPUT        4096    /* Impossible code, to signal flush. */
21 #define FIRST_CODE          4097    /* Impossible code, to signal first. */
22 #define NO_SUCH_CODE        4098    /* Impossible code, to signal empty. */
23 
24 #define FILE_STATE_WRITE    0x01
25 #define FILE_STATE_SCREEN   0x02
26 #define FILE_STATE_IMAGE    0x04
27 #define FILE_STATE_READ     0x08
28 
29 #define IS_READABLE(Private)    (Private->FileState & FILE_STATE_READ)
30 #define IS_WRITEABLE(Private)   (Private->FileState & FILE_STATE_WRITE)
31 
32 typedef struct GifFilePrivateType {
33     GifWord FileState, FileHandle,  /* Where all this data goes to! */
34       BitsPerPixel,     /* Bits per pixel (Codes uses at least this + 1). */
35       ClearCode,   /* The CLEAR LZ code. */
36       EOFCode,     /* The EOF LZ code. */
37       RunningCode, /* The next code algorithm can generate. */
38       RunningBits, /* The number of bits required to represent RunningCode. */
39       MaxCode1,    /* 1 bigger than max. possible code, in RunningBits bits. */
40       LastCode,    /* The code before the current code. */
41       CrntCode,    /* Current algorithm code. */
42       StackPtr,    /* For character stack (see below). */
43       CrntShiftState;    /* Number of bits in CrntShiftDWord. */
44     unsigned long CrntShiftDWord;   /* For bytes decomposition into codes. */
45     unsigned long PixelCount;   /* Number of pixels in image. */
46     FILE *File;    /* File as stream. */
47     InputFunc Read;     /* function to read gif input (TVT) */
48     OutputFunc Write;   /* function to write gif output (MRB) */
49     GifByteType Buf[256];   /* Compressed input is buffered here. */
50     GifByteType Stack[LZ_MAX_CODE]; /* Decoded pixels are stacked here. */
51     GifByteType Suffix[LZ_MAX_CODE + 1];    /* So we can trace the codes. */
52     GifPrefixType Prefix[LZ_MAX_CODE + 1];
53     GifHashTableType *HashTable;
54     bool gif89;
55 } GifFilePrivateType;
56 
57 #endif /* _GIF_LIB_PRIVATE_H */
58 
59 /* end */
60