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| trouble writing file |
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William Labbett
Member #4,486
March 2004
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al_fseek( file, 4, ALLEGRO_SEEK_SET ); pf(" writing version as 2.\n"); al_fwrite32le( file, (int32_t) 2); al_fseek( file, 4, ALLEGRO_SEEK_SET ); v = al_fread32le( file ); pf(" version is after write is %d.\n",v); Hi, in this code, I'm trying to change a number from 1 to 2 in the file. Since it's an int32_t and the version number is the second number in the file, I call al_fseek(file, 4, ALLEGRO_SEEK_SET) to get to the second int32_t. After the write, I seek back to the position of the number and read it to v and print it out but it remains 1, not 2 like I'm trying to achieve. Any ideas why it isn't working ?
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Arthur Kalliokoski
Second in Command
February 2005
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Try an al_fflush() after the write? “Throughout history, poverty is the normal condition of man. Advances which permit this norm to be exceeded — here and there, now and then — are the work of an extremely small minority, frequently despised, often condemned, and almost always opposed by all right-thinking people. Whenever this tiny minority is kept from creating, or (as sometimes happens) is driven out of a society, the people then slip back into abject poverty. This is known as "bad luck.” ― Robert A. Heinlein |
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William Labbett
Member #4,486
March 2004
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Cheers Arthur. I put one in but it hasn't changed anything. 1void convert_file_from_v1_to_v2( ALLEGRO_FILE *file )
2{
3
4 int num_reps;
5
6 int rep_num;
7
8 int v;
9
10 F_REP frep;
11
12 if(file == NULL)
13 {
14 pf(" convert_file_from_v1_to_v2 : file is NULL.\n");
15 system("PAUSE");
16 exit(1);
17 }
18
19 al_fseek( file, 0, ALLEGRO_SEEK_SET );
20
21 num_reps = al_fread32le( file);
22
23 /* Write 2 as the version number. */
24
25 al_fseek( file, 4, ALLEGRO_SEEK_SET );
26
27 pf(" writing version as 2.\n");
28
29 al_fwrite32le( file, (int32_t) 2);
30
31 al_fseek( file, 4, ALLEGRO_SEEK_SET );
32
33 v = al_fread32le( file );
34
35 pf(" version is after write is %d.\n",v);
36
37 pf(" converting file from version 1 to version 2....\n");
38 pf(" num_reps = %d.\n", num_reps);
39
40
41 al_fseek( file, 8, ALLEGRO_SEEK_SET);
42
43
44 for( rep_num = 0; rep_num < num_reps; ++rep_num )
45 {
46 al_fread( file, &frep, sizeof(F_REP));
47
48 if( frep.type > 1 )
49 {
50 frep.type += 1;
51
52 write_f_rep_( file, rep_num, frep);
53 }
54 }
55
56 pf("converted file.\n\n");
57
58 al_fflush(file);
59
60}
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Matthew Leverton
Supreme Loser
January 1999
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What mode are you opening the file as? |
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William Labbett
Member #4,486
March 2004
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1if(type == LOADED_FILE)
2 {
3 load :
4
5 a_file = al_fopen( fn, "a + b");
6 if( a_file == NULL )
7 {
8 printf(" edit_feature_data() : couldn't load file %s\n", fn);
9 return QUIT_DUE_TO_PROBLEM;
10 }
11 else
12 {
13 pf("loaded %s.\n", fn);
14 }
15
16 al_fseek( a_file, 0, ALLEGRO_SEEK_SET);
17
18 num_reps = al_fread32le(a_file);
19
20 eof_check_1
21
22 frd_file_version = al_fread32le(a_file);
23
24 eof_check_1
25
26 feature_selected = num_reps - 1;
27
28 load_fr = 1;
29
30 pf(" num_reps is %d.\n", num_reps);
31 pf("loaded frd file. Version is %d.\n", frd_file_version);
32
33 if( frd_file_version == 1 && CURRENT_VERSION == 2)
34 {
35 convert_file_from_v1_to_v2( a_file );
36
37
38 al_fclose( a_file );
39
40 goto load;
41 }
42
43
44
45 }
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Matthew Leverton
Supreme Loser
January 1999
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I think you want "r+b". Did you check to see if all of your new integers are being appended at the end of the file? |
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William Labbett
Member #4,486
March 2004
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Thanks. It was "r + b" but I thought I needed to change it to "a + b" as I was trying to write to the file, not just to read from it. I've changed it back and it's working now On to the next problem /** EDIT : solved
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Thomas Fjellstrom
Member #476
June 2000
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yeah, when you add a + to the mode, it means to open in read/write mode. r+ means to open rw, with the file pos at the start of the file, and a+ means to open with the file pos at the end. w+ is a bit different, it'll open the file for reading and writing, but it'll truncate the file first. -- |
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