SGABIOS: fix wrong video attrs for int 10h, ah==13h
[sgabios.git] / csum8.c
1 /*
2 * Copyright 2010 Google Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * compute rom checksum byte
17 */
18
19 #include <stdio.h>
20 #include <unistd.h>
21 #include <stdlib.h>
22 #include <fcntl.h>
23 #include <sys/types.h>
24
25 #define MAX_SIZE 65536
26 unsigned char buf[MAX_SIZE];
27
28 int main(int argc, char **argv)
29 {
30 ssize_t fsize;
31 int i, sum, fd;
32 unsigned char csum;
33
34 if (argc < 2) {
35 fprintf(stderr, "usage: %s filename\n", argv[0]);
36 exit(1);
37 }
38 if ((fd = open(argv[1], O_RDWR)) < 0) {
39 perror(argv[1]);
40 exit(1);
41 }
42 if ((fsize = read(fd, buf, MAX_SIZE)) < 0) {
43 perror(argv[1]);
44 exit(1);
45 }
46 if (fsize >= MAX_SIZE && read(fd, &buf[MAX_SIZE - 1], 1) > 0) {
47 fprintf(stderr, "FAIL: %s is larger than %d bytes\n", argv[1], MAX_SIZE);
48 exit(1);
49 }
50 i = fsize - 2048 * (fsize / 2048);
51 if (i != 2047) {
52 fprintf(stderr, "FAIL: %s is %zd bytes, need 2K pad-1\n", argv[1], fsize);
53 exit(1);
54 }
55 for (i = sum = 0; i < fsize; i++) {
56 sum += buf[i];
57 }
58 sum &= 0xff;
59 csum = -sum & 0xff;
60 write(fd, &csum, 1);
61 close(fd);
62 fprintf(stderr, "%s: sum = 0x%02x, wrote byte 0x%02x\n", argv[1], sum, csum);
63 return 0;
64 }