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C, howto read binary file intobuffer

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04-21-2004, 03:17 PM # 1

ScragMember

Registered: Mar 2004Location: WisconsinDistribution: Mandrake 9.2Posts: 116

C, howto read binary file into buffer

Could somebody provide a complete example of codethat shows how to read a binary file into a buffer/arrayin C. Im trying to use fread() but my C book doesntgive very understandable examples. Or if theressomething better than fread thats cool too.

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wto read binary le into buffer http://www.linuxquestions.org/questions/programming-9/...

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ThankYou!!

04-21-2004, 03:35 PM # 2

deiussumMember

Registered: Aug 2003Location: Santa Clara, CADistribution: SlackwarePosts: 895

Rep:

This is just off the top of my head, so I may misssomething, but here goes:

Code:

FILE *f;unsigned char buffer[MAX_FILE_SIZE];int n;

f = fopen("filename.bin", "rb");if (f){

n = fread(buffer, MAX_FILE_SIZE, 1, f)}

else{// error opening file

}

1 members found this post helpful.

04-21-2004, 04:09 PM # 3

The_NerdMember

Registered: Aug 2002Distribution: DebianPosts: 539

Rep:

Code:

void ReadFile(char *name){

FILE *file;char *buffer;unsigned long fileLen;

//Open filefile = fopen(name, "rb");if (!file){

fprintf(stderr, "Unable toreturn;

}

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//Get file lengthfseek(file, 0, SEEK_END);fileLen=ftell(file);fseek(file, 0, SEEK_SET);

//Allocate memorybuffer=(char *)malloc(fileLen+1);if (!buffer){

fprintf(stderr, "Memory efclose(fil

return;}

1 members found this post helpful.

04-21-2004, 04:18 PM # 4

ScragMember

Registered: Mar 2004Location: WisconsinDistribution: Mandrake 9.2Posts: 116

Original PosterRep:

Hhhhmmmmmm.....

With your code, it reads in (im guessing) first 4 bytes of data, which is what is happening with the different codeblocks that i've written. The file is ok, its a .bmp file.The output when printing buffer is:

BM

Where when I cat the file its:

BM(* etc...

etc....etc.........etc........

If im reading on the file right, and displaying it withcorrectly with printf("%s", buffer) , i should get lots of output to screen. I tried a for loop to read it in char bychar, and output is still BM, and i kept an integer countwith how many char's read, and its 4.Heres the code u gave me (modified).....any otherideas??

THANKS!!

FILE *f;unsigned char buffer[10000];int n;

f = fopen("bmp.bmp", "rb");n = fread(buffer, 10000, 1, f);printf("%s\n", &buffer);

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04-21-2004,04:26 PM

itsme86SeniorMember

Registered:Jan 2004Location:

Oregon,USADistribution:SlackwarePosts: 1,246

Rep:

You can't just print a binary buffer as a string. The reason is because if the binary data contains 8-bits in a row of 0's it's interpreted as astring-terminating NULL. So let's say your buffer looks like this:

011101010101010010000101000000000001111111010100010101100

The string interprets the 00000000 as the end of the string.

If you want to show the entire contents of the buffer, then show eachcharacter one at a time until the counter equals the size of the file.

Code:

void dump_buffer(void *buffer, int buffer_size){

int i;

for(i = 0;i < buffer_size;++i)

printf("%c", ((char *)buffer)[i]);}

Last edited by itsme86; 04-21-2004 at 04:30 PM .

04-21-2004, 04:32 PM # 6

ScragMember

Registered: Mar 2004

Location: WisconsinDistribution: Mandrake 9.2Posts: 116

Original PosterRep:

COOL!!!

It works now, thanks to all of you !!!!!

04-21-2004, 07:59 PM # 7

aluserMember

Registered: Mar 2004Location: MassachusettsDistribution: DebianPosts: 557

Rep:

You can also use fwrite to print the whole thing with onefunction call -- it's similar to fread. (Use stdout as theFILE*)

04-21-2004, 08:58 PM # 8

deiussumMember

Registered: Aug 2003

Usually I find it's more useful to display binary data in ahexidecimal format. You can use something like:



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Location: Santa Clara, CADistribution: SlackwarePosts: 895

Rep:

Code:

for (int c=0;c

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return;}

Good Day,How do I read the buffer??I have tried looping through it But I didn't any out put.

Thanks.

09-23-2009, 12:38 AM # 10

kishorworldLQ Newbie

Registered: Sep 2009Posts: 1

Rep:

How to Read Binary data file through C language

Hi friends....

m having a weather report file with extension as .wlkit's a formatted binary data file...

Can anyone tell me that how to read this .wlk file andconvert the data into the text format (.txt)with the helpof C/C++ code ...

if possible provide me source code or usefule links tocreate programme

Email ID: [email protected]

thanx in advance...

Last edited by kishorworld; 09-23-2009 at 12:39 AM . Reason: providing email id

09-23-2009, 12:51 AM # 11

smeezekittySenior Member

Registered: Sep 2009Location: Washington U.S.Distribution: Damn SmallLinux, KateOs, M$ Ickdows

Vista, My own OSPosts: 2,119

Rep:

Quote:

Originally Posted by kishorworldHi friends....

m having a weather report file with extension as.wlk it's a formatted binary data file...

Can anyone tell me that how to read this .wlk file and convert the data into the text format (.txt)with the help of C/C++ code ...

if possible provide me source code or usefulelinks to create programme

Email ID: [email protected]



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thanx in advance...

your problem is more complicatedplease start your own thread

09-23-2009, 10:13 AM # 12

theNbomrSenior Member

Registered: Aug 2005Distribution: OpenSuse,Fedora, Redhat, DebianPosts: 4,667Blog Entries: 2

Rep:

Use the code posted by deiussum in article #8 of thisthread. That won't interpret the file in any way, butsimply display the bytes as hexadecimal. Interpretationof the data is application specific, and most people herewon't know how to extract meaningful information fromfiles of that type. For that, you will need some kind of published documentation, or a code library/API writtenfor the purpose of interpreting the file.--- rod.

09-23-2009, 12:44 PM # 13

smeezekittySenior Member

Registered: Sep 2009Location: Washington U.S.Distribution: Damn SmallLinux, KateOs, M$ IckdowsVista, My own OSPosts: 2,119

Rep:

did you see how many views on this thread?! LOL

01-14-2010, 06:40 AM # 14

naphstorLQ Newbie

Registered: Jan 2010Posts: 3

Rep:

reading a .m4v file.

hi all, i am a newbie in this forum. luckily i got the posti was searching for. but i have some issues. i have a.m4v file and want to read it and display its contents. iread the file and tried to print the buffer, but got some

junk data on screen. i even tried the code given abovefor printing buffer, but effort seems to be in vain. Theabove modified code i used is :-

Code:

#include

main(){




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file = fopen("1.m4v", "rb");if (!file){

fprintf(stderr, "can't opeexit(1);

}

fseek(file, 0, SEEK_END);fileLen=ftell(file);fseek(file, 0, SEEK_SET);

buffer=(char *)malloc(fileLen+1);

if (!buffer){

fprintf(stderr, "Memory efclose(file);

exit(1);}

please help me out. thanks.

01-14-2010, 08:24 AM # 15

Sergei SteshenkoSenior Member

Registered: May 2005Posts: 4,168

Rep:

Quote:

Originally Posted by naphstorhi all, i am a newbie in this forum. luckily i got the post i was searching for. but i have someissues. i have a .m4v file and want to read it and display its contents. i read the file and tried to

print the buffer, but got some junk data on screen . i even tried the code given above for printing buffer, but effort seems to be in vain.The above modified code i used is :-

Code:

#include

main(){


file = fopen("1.m4v", "rb");if (!file){

fprintf(stderr, "caexit(1);

}



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fseek(file, 0, SEEK_END);fileLen=ftell(file);fseek(file, 0, SEEK_SET);

buffer=(char *)malloc(fileLe

if (!buffer){

fprintf(stderr, "Me fclose(file);exit(1);

}

please help me out. thanks.

What kind of data do you expect on the screen and whydo you expect it to look not like junk ? I.e. do you know

what data is displayed on screen as somethingmeaningful and what data as junk/gibberish ? If I may,have you ever heard of ASCII ? If not, try to performweb search on ASCII and/or try

man ascii

on your UNIX/Linux bix.

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