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Re: [Dev-C++] how to use strings
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From: Michael C. <jd...@ho...> - 2001-09-04 07:11:00
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Hi,
Yes this is how I would have done this in the past, it's just that the
person wanted to use fprintf().
Also, I would have used stat() to obtain the size of the file unless (which
is why you have shown this) the file is too big and you just wanted to read
it in chunks.
Generally, (as you know) we know the size of the structs we read in so we
would probably allocate memory for a number of structs and read that in at
one time - whatever is more efficient for our program to do.
Michael
>From: Johannes Pretorius <joh...@pr...>
>To: "Michael C" <jd...@ho...>
>CC: dev...@li...
>Subject: Re: [Dev-C++] how to use strings
>Date: Tue, 04 Sep 2001 07:38:15 +0200
>
>Okay I dont reaaly know what You want to do. Considering you want to read
>in a structure I will say use fread !!! else try something like
>this if you want a block of data
>
>//SNIP
>
>#include <stdio.h>
>#include <fcntl.h>
>#include <alloc.h> /* alloc.h for Borland compilers,
> malloc.h for Microsoft compilers */
>
>#define BUFFER_SIZE 0x8000 /* 32Kb data buffer */
>
>main(int argc, char *argv[]) {
> int Handle;
> unsigned int Checksum;
> unsigned char *WorkingBuffer;
> int WorkingLength;
>
> if ( argc != 2 ) {
> printf("usage: checksum filename\n");
> exit(1);
> }
>
> if ( (Handle = open(argv[1], O_RDONLY | O_BINARY)) == -1 ) {
> printf("Can't open file: %s\n", argv[1]);
> exit(1);
> }
>
> /* Get memory in which to buffer the data */
> if ( (WorkingBuffer = (unsigned char *)malloc(BUFFER_SIZE)) == NULL ) {
> printf("Can't get enough memory\n");
> exit(1);
> }
>
> /* Initialize the checksum accumulator */
> Checksum = 0;
>
> /* Process the file in 32Kb chunks */
> do {
> if ( (WorkingLength = read(Handle, WorkingBuffer,
> BUFFER_SIZE)) == -1 ) {
> printf("Error reading file %s\n", argv[1]);
> exit(1);
> }
> /* Checksum this chunk if there's anything in it */
> if ( WorkingLength ) {
> //Beneath part is in assembler file. So I commented it out
> //ChecksumChunk(WorkingBuffer, WorkingLength, &Checksum);
> }
> } while ( WorkingLength );
>
> /* Report the result */
> printf("The checksum is: %u\n", Checksum);
>
> exit(0);
>}
>
>//END SNIP
>
>NOTE : The above code will always have a checksum of 0 as it is not calling
>the assembler function that is in a different file.
>else a more simple straight forward approach will be
>
>//SNIP
>/*
> * Program to calculate the 16-bit checksum of the stream of bytes
> * from the specified file. Obtains the bytes one at a time via
> * getc(), allowing C to perform data buffering.
> */
>#include <stdio.h>
>
>main(int argc, char *argv[]) {
> FILE *CheckFile;
> int Byte;
> unsigned int Checksum;
>
> if ( argc != 2 ) {
> printf("usage: checksum filename\n");
> exit(1);
> }
>
> if ( (CheckFile = fopen(argv[1], "rb")) == NULL ) {
> printf("Can't open file: %s\n", argv[1]);
> exit(1);
> }
>
> /* Initialize the checksum accumulator */
> Checksum = 0;
>
> /* Add each byte in turn into the checksum accumulator */
> while ( (Byte = getc(CheckFile)) != EOF ) {
> Checksum += (unsigned int) Byte;
> }
>
> /* Report the result */
> printf("The checksum is: %u\n", Checksum);
>
> exit(0);
>}
>
>//END SNIP
>
>Now this is basic stuff that I can think of right now. Futher more if you
>can give more information on what you want to achieve maybe we can help
>
>
>hope this helps
>Johannes
>
>
>
>At 21:34 03/09/2001 +0100, you wrote:
>>Hi,
>>
>>I havn't programmed in C for a couple of years now, I've been
>>concentrating
>>on C++.
>>I have forgotten a few things so I'm watching this group for input, and
>>I've
>>been impressed by what I have seen.
>>
>>I had a look at your code and spotted a few things:
>>
>>1) For fopen() use "w+" as you need to read it as well.
>>2) Use ' fseek (fhandle, 0L, SEEK_SET);' to reposition the file to the
>>beginning for reading.
>>3) Dereference fhandle (*fhandle) in the fprintf() statement and this will
>>read in the string.
>>3) fprintf() and fscanf() do not move the file position and I can't
>>remember
>>how to do this. So another call to fprintf() will not read the stringified
>>number on the next line. I thought I could use:
>> 'fseek (fhandle, len, SEEK_CUR);' where len is the returned value
>>from a successful call to fprintf()
>> However, this doesn't work. Instead I prefer to use:
>>
>> int c;
>> while ((c = fgetc (fhandle)) != EOF)
>> {
>> fputc (c, stdout);
>> }
>>
>>Any comments?
>>
>>Hope this helps.
>>
>>Michael
>>
>>----- Original Message -----
>>From: Johannes Pretorius <joh...@pr...>
>>To: <jsc...@gm...>
>>Cc: <dev...@li...>
>>Sent: Monday, September 03, 2001 2:07 PM
>>Subject: Re: [Dev-C++] how to use strings
>>
>>
>> > this here is a simple example that will make more sense. For
>>considering
>> > that you are trying to mix
>> > your WINAPI functions and write to the handle of the file allocators. I
>>do
>> > not think that it is possible in
>> > the compiler version. Maybe with a Microsft compiler.
>> >
>> > else this is a VERY simple way to do it that works. I hope this help.,
>> > Please mail if I misunderstand you.
>> >
>> > file://====== SNIP =========
>> >
>> > #include <iostream.h>
>> > #include <stdio.h>
>> > #include <stdlib.h>
>> >
>> >
>> >
>> > struct test{
>> > char data [200];
>> > }testdata;
>> >
>> > void main(void){
>> > char outstring[200];
>> > FILE *fhandle;
>> > int actualnumber;
>> >
>> > file://open in write mode (override if exist);
>> > fhandle = fopen("c:\\medcelldata.txt","w");
>> > /*CreateFile("c:/medcelldata.txt",
>> > GENERIC_READ | GENERIC_WRITE,
>> > 0,
>> > NULL,
>> > OPEN_ALWAYS,
>> > FILE_ATTRIBUTE_NORMAL,
>> > NULL
>> > );
>> > */
>> >
>> > if(fhandle == NULL)
>> > {
>> > printf("\nNO File present");
>> > }
>> >
>> > file://copy test to structuer
>> > strcpy(testdata.data,"Hallo World\n");
>> >
>> > actualnumber = 1000;
>> >
>> > file://write using fwrite (BETTER for Structures)
>> > fwrite(&testdata, sizeof(testdata), 1, fhandle);
>> >
>> > file://convert integer
>> > itoa(actualnumber, outstring, 10);
>> >
>> > file://write with fprintf to file
>> > fprintf(fhandle,"OutString : %s",outstring);
>> >
>> > file://clsoe file
>> > fclose(fhandle);
>> > }
>> >
>> >
>> >
>> >
>> > file://========= END SNIP =========
>> >
>> > Hope it helps
>> > Johannes
>> >
>> >
>> >
>> > At 14:03 03/09/2001 +0200, you wrote:
>> > >On 3 Sep 2001, at 11:57, Johannes Pretorius wrote:
>> > >
>> > > > Johannes Pretorius <joh...@pr...>
>> > >
>> > >
>> > >Here it is ! i allready change something to make it run - but in the
>> > >written file there only occurs 1- or two figures !
>> > >
>> > >How can i use the fprintf - function to access the file ????
>> > >
>> > >
>> > >
>> > >#include <iostream.h>
>> > >#include <stdio.h>
>> > >#include <stdlib.h>
>> > >#include <windows.h>
>> > >
>> > >// vars
>> > >
>> > >HANDLE hcom; // file handler
>> > >HANDLE hfile;
>> > >DWORD dwWritten;
>> > >
>> > >int value[8];
>> > >int numofdata[15] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} ;
>> > >
>> > >BYTE noise; // for testing only
>> > >BYTE activeitem; // no of active row
>> > >
>> > >BYTE in_buffer[35]; // input buffer = 8
>>needed
>> > >BYTE out_buffer[35]; // output buffer
>> > >
>> > >int writepoint;
>> > >int readpoint;
>> > >int writepointin; // write pos inbuffer
>> > >int readpointin; // read pos inbuffer
>> > >int goodvalue;
>> > >int tempvalue;
>> > >int actualnumber;
>> > >
>> > >BYTE input;
>> > >BYTE count;
>> > >int globalschleife;
>> > >LPTSTR lpMessage;
>> > >
>> > >int progmode; // bin or asc
>> > >
>> > >
>> > >....
>> > >
>> > > hfile = CreateFile("E:/medcelldata.txt",
>> > > GENERIC_READ | GENERIC_WRITE,
>> > > 0,
>> > > NULL,
>> > > OPEN_ALWAYS,
>> > > FILE_ATTRIBUTE_NORMAL,
>> > > NULL
>> > > );
>> > >
>> > > if(hfile == INVALID_HANDLE_VALUE)
>> > > {
>> > > printf("\nNO File present");
>> > > }
>> > >
>> > > pstr = "MedCellCom 1.2\n\n ";
>> > > WriteFile(hfile, pstr, 16, &dwWritten, NULL);
>> > >
>> > >
>> > > pstr = "Prozess - Protokoll vom : \n ";
>> > >
>> > > WriteFile(hfile, pstr, 27, &dwWritten, NULL);
>> > >
>> > >
>> > > itoa(actualnumber, outstring, 10);
>> > >
>> > > WriteFile(hfile, outstring, 10, &dwWritten,
>>NULL);
>> > >
>> > > WriteFile(hfile, "456", 3, &dwWritten, NULL);
>> > >
>> > > printf("%d\t", dwWritten);
>> > > printf("%s\n", outstring);
>> > >
>> > >
>> > >
>> > >The output shows only
>> > >
>> > > MedCellCom 1.2
>> > >
>> > > Prozess - Protokoll vom :
>> > >2
>> > >
>> > >Where "2" ist the actualnumber
>> > >
>> > >I do not see the 456 test string allthoug the screen
>> > >shows the correct outstring and 3 chars written !
>> > >
>> > >It is a big loop, where many lines are written and
>> > >shown on the screeen it works and the prog terminates.
>> > >
>> > >When writing only dummy strings like explicit
>> > >"iugnuztf" it works and show 200 lines with exactly
>> > >this text !
>> > >
>> > >????
>> >
>> >
>> > _______________________________________________
>> > Dev-cpp-users mailing list
>> > Dev...@li...
>> > https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
>> >
>
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