1 /*	screendump 1.2 - dump the contents of the console
2  *							Author: Kees J. Bot
3  *								16 Dec 1994
4  */
5 #define nil 0
6 #include <sys/types.h>
7 #include <stdlib.h>
8 #include <unistd.h>
9 #include <errno.h>
10 #include <fcntl.h>
11 #include <string.h>
12 #include <termios.h>
13 #include <sys/ioctl.h>
14 
15 #define BIOS_CRTBASE	0x00463L	/* BIOS parameters: CRT base. */
16 #define CRTBASE_MONO	0x03B4		/* Value of CRT base for mono mode. */
17 
18 #define MONO_BASE	0xB0000L	/* Screen memory in monochrome mode. */
19 #define COLOR_BASE	0xB8000L	/* ... colour mode. */
20 
21 #define DEF_COLS	80		/* Default screen geometry. */
22 #define DEF_ROWS	25
23 
24 #define MAX_COLS	132		/* Maximum screen geometry. */
25 #define MAX_ROWS	60
26 
27 char MEMORY[] =		"/dev/mem";	/* Memory device to read screen. */
28 int mfd;				/* Open memory device. */
29 
30 void tell(const char *message)
31 {
32 	write(2, message, strlen(message));
33 }
34 
35 void fatal(const char *label)
36 {
37 	const char *err= strerror(errno);
38 
39 	tell("screendump: ");
40 	tell(label);
41 	tell(": ");
42 	tell(err);
43 	tell("\n");
44 	exit(1);
45 }
46 
47 long video_base(void)
48 /* Is it monochrome or colour? */
49 {
50 	static unsigned short bios_crtbase;
51 
52 	if (lseek(mfd, (off_t) BIOS_CRTBASE, SEEK_SET) == -1) fatal(MEMORY);
53 	switch (read(mfd, &bios_crtbase, sizeof(bios_crtbase))) {
54 	case -1:
55 		fatal(MEMORY);
56 	default:
57 		tell("screendump: can't obtain BIOS parameter: short read\n");
58 		exit(1);
59 	case sizeof(bios_crtbase):
60 		/* Fine */;
61 	}
62 
63 	return bios_crtbase == CRTBASE_MONO ? MONO_BASE : COLOR_BASE;
64 }
65 
66 int main(void)
67 {
68 	static unsigned char screen[MAX_COLS * MAX_ROWS * 2];
69 	unsigned char *ps;
70 	long base;
71 	int lfd;
72 	int row;
73 	int nrows, ncols;
74 	struct winsize winsize;
75 
76 	/* Open the memory device. */
77 	if ((mfd= open(MEMORY, O_RDONLY)) < 0) fatal(MEMORY);
78 
79 	base= video_base();
80 
81 	/* Read screen memory. */
82 	if (lseek(mfd, base, SEEK_SET) == -1) fatal(MEMORY);
83 
84 	switch (read(mfd, screen, sizeof(screen))) {
85 	case -1:
86 		fatal(MEMORY);
87 	default:
88 		tell("screendump: can't obtain screen dump: short read\n");
89 		exit(1);
90 	case sizeof(screen):
91 		/* Fine */;
92 	}
93 
94 	/* Try to obtain the screen geometry from /dev/log. */
95 	ncols= DEF_COLS;
96 	nrows= DEF_ROWS;
97 	if ((lfd= open("/dev/log", O_WRONLY)) != -1
98 		&& ioctl(lfd, TIOCGWINSZ, &winsize) == 0
99 	) {
100 		if (40 <= winsize.ws_col && winsize.ws_col <= MAX_COLS) {
101 			ncols= winsize.ws_col;
102 		}
103 		if (25 <= winsize.ws_row && winsize.ws_row <= MAX_COLS) {
104 			nrows= winsize.ws_row;
105 		}
106 	}
107 	if (lfd != -1) close(lfd);
108 
109 	/* Print the contents of the screen line by line.  Omit trailing
110 	 * blanks.  Note that screen memory consists of pairs of characters
111 	 * and attribute bytes.
112 	 */
113 	ps= screen;
114 	for (row= 0; row < nrows; row++) {
115 		char line[MAX_COLS + 1];
116 		char *pl= line;
117 		int column;
118 		int blanks= 0;
119 
120 		for (column= 0; column < ncols; column++) {
121 			if (*ps <= ' ') {
122 				/* Skip trailing junk. */
123 				blanks++;
124 			} else {
125 				/* Reinsert blanks and add a character. */
126 				while (blanks > 0) { *pl++= ' '; blanks--; }
127 				*pl++= *ps;
128 			}
129 			/* Skip character and attribute byte. */
130 			ps+= 2;
131 		}
132 		*pl++= '\n';
133 		if (write(1, line, pl - line) < 0) fatal("stdout");
134 	}
135 	exit(0);
136 }
137