Thread: dump the buffer read from binary file

Sup guys,

I am reading the binary file to the buffer(char array) and then want parse it to this struct array.

Code:

typedef struct
{
  char key[4], name[20];
  int mark;
}rec;
int main()
{
   rec recs[10];
   .........
}

when parsing, i read characters one by one to fill 'key' and 'name' fields, but how do i deal with integer?
int is 4 bytes. so when i read the content of the binary file to char array(buffer) that integer is stored byte by byte in that array.
How do I get that integer from buffer?

Thanks!

ps. or is there a way to read directly to the struct array?

You can scanf() it directly to the struct member, but fscanf() needs strictly compliant data to the format you request with it.

You can also get it from the string buffer with sscanf(), <just scanf() from a string >

You could maybe use something like memmove:

Code:

memmove   Copies a block of n bytes from src to dest.

 Syntax:
   void *memmove(void *dest, const void *src, size_t n);

 Prototype in:
 mem.h   string.h

 Remarks:
memmove copies a block of n bytes from src to dest.

Even when the source and destination blocks overlap, bytes in the
overlapping locations are copied correctly.

 Return Value:
memmove returns dest.

 Portability:
memmove is available on UNIX System V systems and is compatible
with ANSI C.

 Example:
#include <string.h> 
#include <stdio.h>

 int main(void)
 {
   char *dest = "abcdefghijklmnopqrstuvwxyz0123456789";
   char *src = "******************************";
   printf("destination prior to memmove: %s\n", dest);
   memmove(dest, src, 26);
   printf("destination after memmove:    %s\n", dest);
   return 0;
 }

I'm not very familiar with memmove, but when I read "4 bytes", in your post, it came to mind, right away.

What do you think?

I think I better post the whole code, for you guys to get the idea of whats reall going on.
here we go:

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct
{
	char key[4], Name[21];
	int Mark;
}rec;
void merge(rec * rm, rec * r1, rec * r2, int n1, int n2);
void printRecs(rec * r, int n);
void parseF(char * filename, rec * r, int *n);

int main(void)
{
	int i, n1=0, n2=0;

	rec recs1[10], recs2[10], recs[20];

	char s[27];
	
    	parseF("bin1", recs1, &n1);
        parseF("bin2", recs2, &n2);
	merge(recs, recs1, recs2, n1, n2);
	printRecs(recs, n1+n2);
		
	return 0;
}   
void parseF(char* filename, rec *r, int *n)
{
	FILE *f;
	char *buffer;
	unsigned long fileLen;
	int i, ri, part, ci;

	f = fopen(filename, "rb");
	if ( f == NULL )
	{
		printf("Cannot open record file %s", filename);   
		exit(1);
	}
	fseek(f, 0, SEEK_END);
	fileLen = ftell(f);
	fseek(f, 0, SEEK_SET);
	
	buffer = (char*)malloc(fileLen+1);
	if (!buffer)
	{
		printf("Cannot allocate memory");
		fclose(f);
		exit(1);
	}
	fread(buffer, fileLen, 1, f);
	//r = (rec*)malloc(sizeof(rec)*fileLen/27);
	i  = 0;
	ri = 0; // record count
	ci = 0;; // character count;
	part = 0;
	while(i<fileLen)
	{
		if(buffer[i]=='\0') {continue;}
		if (i%27==0)
		{
			ci=0;
			part = 0;
			ri++;
		}
		if (i%27==3)
		{
			ci=0;
			part = 1;
		}
		if (i%27==23)
		{
			ci=0;
			part = 2;
		}
		if (part == 0)
		{
			printf("%c\n", buffer[i]);
			r[ri].key[ci++] = buffer[i];
		} else if (part == 1)
		{
			printf("%c\n", buffer[i]);
			r[ri].Name[ci++] = buffer[i];
		} else if (part == 2)
		{
			// ??????
		}
		i++;
	}
	fclose(f);
}
void merge(rec * rm, rec * r1, rec * r2, int n1, int n2)
{
	int i1=0, i2=0, i=0;
	while (i1<n1 && i2<n2)
	{
		if (r1[i1].Mark < r2[i2].Mark)
		{
			strcpy(rm[i].key, r1[i1].key);
			strcpy(rm[i].Name, r1[i1].Name);
			rm[i].Mark = r1[i1].Mark;
			i1++;
		}
		else if (r1[i1].Mark > r2[i2].Mark)
		{
			strcpy(rm[i].key, r2[i2].key);
			strcpy(rm[i].Name, r2[i2].Name);
			rm[i].Mark = r2[i2].Mark;
			i2++;
		}
		else
		{
			if (strcmp(r1[i1].Name, r2[i2].Name)<1)
			{
				strcpy(rm[i].key, r1[i1].key);
				strcpy(rm[i].Name, r1[i1].Name);
				rm[i].Mark = r1[i1].Mark;
				i1++;
			}
			else
			{
				strcpy(rm[i].key, r2[i2].key);
				strcpy(rm[i].Name, r2[i2].Name);
				rm[i].Mark = r2[i2].Mark;
				i2++;
			}
		}
		i++;

	}
	while (i1<n1){ rm[i].Mark = r1[i1].Mark; i1++; i++;}
	while (i2<n2){ rm[i].Mark = r2[i2].Mark; i2++; i++;}

}
void printRecs(rec * r, int n)
{
	int i;
	for (i=0;i<n ;i++ )
	{
		printf("%3s  %20s %4d\n", r[i].key, r[i].Name, r[i].Mark);
	}
}

What my code is supposed to do:
1)Reads two binary files which contain [key][Name][Mark] records which are sorted by [Mark] field
2)puts them in two different struct arrays
3)merges them, so we get third sorted array of structs
4)prints it

In parseF method there is commented line with question marks... that's the place where I am stuck...

One more thing:

records in bin file are stored in this way
key Name Mark
[3 bytes][20 bytes][4 bytes]
- no delimeters between the fields
- the Name field which is 20 chars long can be less than 20 chars and ends with null character, the rest of the bytes can contain anything and
(# bytes before null)+(# the rest of bytes) = 20

Any suggestions are welcome!

I'll post up some code for a part of the program.

That would be awesome, appreciate that!

I can't put the contents of binary file because there are some characters which cannot be displayed in simple text editor. for example null character '\0'
so, ok here is the example of bin file with '\0':

Code:

AAAJohn Doe\0abcdefghijk1BBBJack Doe\0abcdefghijk2CCCBenn Doe\0abcdefghijk3

What I need is a true binary file - everything just the same.

You can post it at Swoopshare, (a file depot website) and then post the link, here.

RapidShare: 1-CLICK Web hosting - Easy Filehosting

Originally Posted by quzah

Ah, so you're advocating modifying string literals because you might get lucky. Clearly you should be giving advise here...


Quzah.

I made no statement advocating modifying string literals. That was the example by Borland.

As was stated by laserlight, memmove (you do remember memmove() was the subject of my post, right?) works on char arrays.

Clearly, you have no substantive point to make, and you should learn to spell "advice".

Originally Posted by quzah

You wrote:

"You could maybe use something like memmove:"

Then illustrated its use by modifying a string literal. You didn't qualify your example as:Therefore, it's not beyond reason that I tell you it's incorrect. Furthermore, you followed up with a reply, not acknowledging that it was incorrect, but rather said that it "works for me".

The difference here is that I'm not on an English forum, teaching the English language.


Quzah.

A "maybe" is *NOT* the same thing as a recommendation. "What do you think?" is not advocating an action, it is asking a question.

Turbo C has been modifying string literals for more than 20 years for me. You want me to lie about it?

Laserlight already posted the change needed to use memmove() on a string.

Instead of trying to make a point that has already been made and solved, why not try and post up a nice suggestion or code example for r00t?

I'm much too old to be impressed by how correct you think you are.