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27: BigEndian ( ) ; 
28: 
29: const uint64 PNGMAGIC = 0x89504E470D0A1A0A L ; 
30: 
31: 
32: typedef union { 
33: uint32 ctype < format = hex > ; 
34: char cname [ 4 ] ; 
35: } CTYPE < read = readCTYPE > ; 
36: 
37: string readCTYPE ( local CTYPE & t ) { 
38: return t . cname ; 
39: } 
40: 
41: 
42: 
43: 
44: 
45: typedef struct { 
46: uint32 width ; 
47: uint32 height ; 
48: ubyte bits ; 
49: ubyte color_type ; 
50: ubyte compression ; 
51: ubyte filter ; 
52: ubyte interlace ; 
53: } IHDR < read = readIHDR > ; 
54: 
55: string readIHDR ( local IHDR & ihdr ) { 
56: local string s ; 
57: SPrintf ( s , "%i x %i (x%i)" , ihdr . width , ihdr . height , ihdr . bits ) ; 
58: return s ; 
59: } 
60: 
61: 
62: 
63: typedef struct { 
64: string label ; 
65: char data [ length - Strlen ( label ) - 1 ] ; 
66: } tEXt < read = readtEXt > ; 
67: 
68: string readtEXt ( local tEXt & text ) { 
69: local string s ; 
70: SPrintf ( s , "%s = %s" , text . label , text . data ) ; 
71: return s ; 
72: } 
73: 
74: 
75: 
76: local uint32 CHUNK_CNT = 0 ; 
77: 
78: 
79: typedef struct { 
80: uint32 length ; 
81: local quad pos_start = FTell ( ) ; 
82: CTYPE type ; 
83: if ( type . cname == "IHDR" ) { 
84: IHDR ihdr ; 
85: } else if ( type . cname == "tEXt" ) { 
86: tEXt text ; 
87: } else { 
88: ubyte data [ length ] ; 
89: } 
90: local quad data_size = FTell ( ) - pos_start ; 
91: uint32 crc < format = hex > ; 
92: local uint32 crc_calc = Checksum ( CHECKSUM_CRC32 , pos_start , data_size ) ; 
93: if ( crc != crc_calc ) { 
94: local string msg ; 
95: SPrintf ( msg , "*WARNING CRC Mismatch @ chunk[%d] (%08x != %08x)\n" , CHUNK_CNT , crc , crc_calc ) ; 
96: Warning ( msg ) ; 
97: Printf ( msg ) ; 
98: } 
99: CHUNK_CNT ++ ; 
100: } CHUNK < read = readCHUNK > ; 
101: 
102: 
103: 
104: 
105: 
106: 
107: 
108: 
109: string readCHUNK ( local CHUNK & c ) { 
110: local string s ; 
111: s = readCTYPE ( c . type ) + "  (" ; 
112: s += ( c . type . cname [ 0 ] & 0x20 ) ? "Ancillary, " : "Critical, " ; 
113: s += ( c . type . cname [ 1 ] & 0x20 ) ? "Private, " : "Public, " ; 
114: s += ( c . type . cname [ 2 ] & 0x20 ) ? "ERROR_RESERVED, " : "" ; 
115: s += ( c . type . cname [ 3 ] & 0x20 ) ? "Safe to Copy)" : "Unsafe to Copy)" ; 
116: return s ; 
117: } 
118: 
119: 
120: 
121: 
122: 
123: uint64 pngid < format = hex > ; 
124: if ( pngid != PNGMAGIC ) { 
125: Warning ( "Invalid PNG File: Bad Magic Number" ) ; 
126: return - 1 ; 
127: } 
128: while ( ! FEof ( ) ) { 
129: CHUNK chunk ; 
130: } 
131: if ( CHUNK_CNT > 1 ) { 
132: if ( ( chunk [ 0 ] . type . cname != "IHDR" ) || ( chunk [ CHUNK_CNT - 1 ] . type . cname != "IEND" ) ) { 
133: local string msg ; 
134: SPrintf ( msg , "*WARNING: Chunk IHDR must be first and chunk IEND must be last!\n" ) ; 
135: Warning ( msg ) ; 
136: Printf ( msg ) ; 
137: } 
138: } 
139: tok_eof