saving/reading a long to/from a file?

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Socoder -> C/C++/C#/Other -> saving/reading a long to/from a file?
Tue, 11 Dec 2007, 06:07
spinal	I am trying to save a long int to a file, then read it back, however its not working, can someone help me out? if (Pad.Newpress.Y) { // Open bookmark FILE* testRead = fopen ("music.bmk", "rb"); //rb = read if(testRead) { PA_StopMP3(); // this does nothing to the file handle - don't forget to close it! fread((long )&file_position, 4, 1, testRead); fseek(infile, file_position ,SEEK_SET); // jump to new location PA_ResumeMP3(); } fclose(testRead); }// press Y if(PA_RTC.Seconds==0 && saved==0) { long file_position = ftell(infile); PA_StopMP3(); // momenterally pause the mp3 FILE testWrite = fopen ("music.bmk", "wb"); //wb = create/truncate & write fwrite((long *)&file_position, sizeof(file_position), 1, testWrite); fclose(testWrite); PA_ResumeMP3(); // Resume playback saved=1; }else{saved=0;} --v -=-=- Check out my excellent homepage!
Tue, 11 Dec 2007, 06:38
Jayenkai	Long int's aren't 4, are they? I thought regular ints were 32bit = 4, and longints were 64bit=8.. Having googled it, the whole net seems confused with some saying 4 and some saying 8! A few suggest that a "long long int" is 8!! I think the rule might be that if and int is 4 then long should be 8. so try that! If not.. Are you sure the DS is even handling the long as it should in the first place, even before the load/save stuff? -=-=- ''Load, Next List!''
Tue, 11 Dec 2007, 06:52
Afr0	AFAIK, from what I've learned from my time with C and C++, the actual size of standard variables in memory can vary from machine to machine. I'm pretty sure there's a 'standard' value for the DS though - this should be easy to print out using the sizeof() function. Not sure what headers you need to include to get that function in the DS API, but it should just be standard C headers. (PC) Test Program: #include <stdout> fprint("Sizeof long: %i", sizeof(long)); --v Note that the parameters (specifically, the '%i' bit) for the fprint function might be wrong - I haven't used ANSI C for ages. Edit: Found a better example. /* * $Id: sizeof.c,v 1.4 2006/03/23 20:08:08 sms Exp $ * www.pccl.demon.co.uk * * Program to display data sizes. / #include <stdio.h> #include <time.h> #include <sys/types.h> #define printsize(x) printf ("sizeof (" #x ") = %d\n", sizeof (x)) main () { printf ("\nC\n"); printsize (char); printsize (double); printsize (float); printsize (int); printsize (long); printsize (long long); printsize (short); printsize (void ); printf("\n"); printsize (clock_t); printsize (gid_t); printsize (pid_t); printsize (size_t); printsize (ssize_t); printsize (time_t); printsize (uid_t); } --v -=-=- Afr0 Games Project Dollhouse on Github - Please fork!
Tue, 11 Dec 2007, 17:38
spinal	long is printing out as 4. Other than the worries about the size of the variable, are my attempts logical, or am I missing something? No matter what the variable is when writing, it reads (or at least prints) as 1. perhaps I'm using fread incorrectly. -=-=- Check out my excellent homepage!
Tue, 11 Dec 2007, 17:43
Jayenkai	Oh yeah.. That's right.. I had weird issues trying to read 1 single thing, didn't I! Have you tried creating a small temp[2] array, and loading into that instead? That usually works for me -=-=- ''Load, Next List!''
Tue, 11 Dec 2007, 17:58
spinal	You'll have to give me some example code jay, do you mean I should load the 4 bytes seperatly? -=-=- Check out my excellent homepage!
Tue, 11 Dec 2007, 18:11
Jayenkai	I'm sure fileread should do as it says, but I can't seem to get it to work with single variables, and instead it seems insistent on working with Arrays. (I really should learn all this pointer gubbins someday!) FILE* testRead = fopen ("music.bmk", "rb"); //rb = read if(testRead) { PA_StopMP3(); // this does nothing to the file handle - don't forget to close it! fread((long )&file_position, 4, 1, testRead); fseek(infile, file_position ,SEEK_SET); // jump to new location PA_ResumeMP3(); } fclose(testRead); --v Where you have that, switch it with this. long longtemp[2]; FILE testRead = fopen ("music.bmk", "rb"); //rb = read if(testRead) { PA_StopMP3(); // this does nothing to the file handle - don't forget to close it! fread(longtemp, 4, 2, testRead); file_position=longtemp[0]; fseek(infile, file_position ,SEEK_SET); // jump to new location PA_ResumeMP3(); } fclose(testRead); --v And vice-versa for the Write bit, too. I'm sure I'll now get 100 complaints about my lack of "Proper C Coding Skills" but it works, and that's good enough for me!! And No$GBA, too, which still insists my DS Coding is a "Technically rare masterpiece" ) -=-=- ''Load, Next List!''
Tue, 11 Dec 2007, 19:59
spinal	Seems to work fine, but the mp3 lib doesnt like starting in the middle. I'll mess with it a bit more, see if anything works. -=-=- Check out my excellent homepage!