Re: Binary File IO - C / C++ / MFC Discussion Boards

Neville Franks23-Jun-06 13:27

23-Jun-06 13:27

You need to use the pre, code, < and > Formatting buttons at the bottom of the editor area otherwise we can't see your code correctly.

You also need to tell us the specific compiler and linker errors you are getting.

Neville Franks, Author of Surfulater www.surfulater.com "Save what you Surf" and ED for Windows www.getsoft.com

API needed

act_x23-Jun-06 9:57

act_x

23-Jun-06 9:57

Need to know if there is an API

1) to get the directory listing

2) To be able to search for a particular file extension

As for eg

Say i have a file i need to search for like AM01.txt in C:\temp1\temp2

I need an API to list the folders --> temp1 and then temp2

Then an API to filter *.txt files in that folder

Any ideas ?

Engineering is the effort !

Re: API needed

cje23-Jun-06 9:59

cje

23-Jun-06 9:59

have you looked at CFileFind class?

Re: API needed

David Crow23-Jun-06 10:00

David Crow

23-Jun-06 10:00

act_x wrote:
1) to get the directory listing

Use the FindFirstFile()/FindNextFile() pair.

act_x wrote:
2) To be able to search for a particular file extension

See above, just use *.txt in the pattern.

If you know the exact name of the file, and simply want to check for existence, use _access() or GetFileAttributes() instead.

"The largest fire starts but with the smallest spark." - David Crow

"Judge not by the eye but by the heart." - Native American Proverb

Re: API needed

act_x23-Jun-06 10:05

act_x

23-Jun-06 10:05

Thanks for your responses

Engineering is the effort !

Re: API needed

Hamid_RT23-Jun-06 21:08

Hamid_RT

23-Jun-06 21:08

See

<br />
(1)<br />
TCHAR lpt[260];<br />
lpt[0]='\0';<br />
strcat(lpt,"c:\\");<br />
GetCurrentDirectory(sizeof(lpt),lpt);<br />
DlgDirList(lpt,IDC_LIST2,NULL,DDL_DIRECTORY|DDL_ARCHIVE);//IDC_LIST2 is CListBox<br />
-----------------------------<br />
(2)<br />
WIN32_FIND_DATA find;<br />
HANDLE handle=FindFirstFile("*.*",&find);<br />
while(FindNextFile(handle,&find)!=0)<br />
m_List2.AddString(find.cFileName);//m_List2 is CListBox<br />
FindClose(handle); <br />

maybe it is some helpful to you

whitesky

Binary File IO

Jumpin' Jeff23-Jun-06 9:06

Jumpin' Jeff

23-Jun-06 9:06

I'm having trouble grasping Binary file I/O.

I am trying to read back a binary file that includes the following example...

char type[9]="File Type"
short MajorVersion = 1
short MinorVersion = 0

Using most methods found, I can read "File Type" but it's got garbage appended to it, so I cannot compare with a known type.

Also, I'm having trouble going beyond that. Meaning, I cannot access the version shorts.

The examples I've come across doesn't go into any depth about multiple types, or how to retrieve multiple items from a single buffer read.

Do I need to flush the buffer, and reposition my pointer?

What's the best way about getting this information out of my file?

Can someone give me a quick example of how to retrieve this data, and what method is most efficient?

Jeff

Re: Binary File IO

David Crow23-Jun-06 9:10

David Crow

23-Jun-06 9:10

Jumpin` Jeff wrote:
Using most methods found, I can read "File Type" but it's got garbage appended to it...

Exactly how are you reading the file? If you are reading nine bytes from the file, it should work.

Try this:

struct
{
    char type[9];
    short MajorVersion;
    short MinorVersion;
} myStruct;
 
FILE *pFile = fopen(..., "rb");
fread(&myStruct, sizeof(myStruct), 1, pFile);
fclose(pFile);

Depending on what you do with type, you may need room for a \0 character.

"The largest fire starts but with the smallest spark." - David Crow

"Judge not by the eye but by the heart." - Native American Proverb

Re: Binary File IO

Jumpin' Jeff23-Jun-06 9:41

Jumpin' Jeff

23-Jun-06 9:41

Thank you for such a quick responce David!

Using your example, I come up with similar to previous results....

The version shorts should have been Unsigned, My bad, but I used the following to display the extracted information....

cout << myStruct.type << "\n" << myStruct.MajorVersion<<"."<

Re: Binary File IO

David Crow23-Jun-06 9:53

David Crow

23-Jun-06 9:53

Jumpin` Jeff wrote:
File Type@ <- Actually a smiley symbol...

You will not be able to treat it as a nul-terminated string unless it actually ends with a \0 character.

"The largest fire starts but with the smallest spark." - David Crow

"Judge not by the eye but by the heart." - Native American Proverb

Re: Binary File IO [modified]

Zac Howland23-Jun-06 10:02

Zac Howland

23-Jun-06 10:02

Just a recommendation:

Instead of assuming your string is X number of characters long, write the string length first, followed by the characters in the string:

struct FileData<br />
{<br />
char* String;<br />
short MajorVersion;<br />
short MinorVersion;<br />
};<br />
<br />
// to write the file<br />
FileData data;<br />
// assuming data has already been filled in<br />
FILE pFile = fopen(..., "wb");<br />
long size = strlen(data.String);<br />
fwrite(&size, sizeof(size), 1, pFile);<br />
fwrite(data.String, size, 1, pFile);<br />
fwrite(&data.MajorVersion, sizeof(short), 1, pFile);<br />
fwrite(&data.MinorVersion, sizeof(short), 1, pFile);<br />
<br />
// to read the file<br />
FileData data1;<br />
FILE pReadFile = fopen(..., "rb");<br />
long readSize = 0;<br />
fread(&readSize, sizeof(readSize), 1, pReadFile);<br />
assert(readSize > 0);<br />
// create and initialize the new string<br />
data1.String = new char[readSize + 1];<br />
memset(data1.String, 0, readSize + 1);<br />
fread(&data1.String, readSize, 1, pReadFile);<br />
fread(&data1.MajorVersion, sizeof(short), 1, pReadFile);<br />
fread(&data1.MinorVersion, sizeof(short), 1, pReadFile);<br />

If you write the structure as a class, you can put the serialization code as a class member and have your code just call MyClass.Read/Write to make it very simple.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

-- modified at 16:03 Friday 23rd June, 2006

Re: Binary File IO [modified]

Joe Woodbury23-Jun-06 9:25

Joe Woodbury

23-Jun-06 9:25

The string "File Type" is 9 characters long; you are not writing/reading the null terminator. (Oddly, the compiler should have warned you about an overflowed buffer.)

David's example is good, except I would make type 10 characters. I would also place #pragma pack(1) before the structure and #pragma pack(0)#pragma pack() after.

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

-- modified at 16:36 Friday 23rd June, 2006

Re: Binary File IO

Jumpin' Jeff23-Jun-06 9:50

Jumpin' Jeff

23-Jun-06 9:50

Thanks Joe, but there is no null terminator.
That is the way the file is previously constructed. My example is just a very simple representation of the actual file.

It is X characters, followed by a file major version, then file minor version identifier.

Can you explain what #pragma pack will do for me?

Re: Binary File IO

David Crow23-Jun-06 9:55

David Crow

23-Jun-06 9:55

Jumpin` Jeff wrote:
Can you explain what #pragma pack will do for me?

See here.

"The largest fire starts but with the smallest spark." - David Crow

"Judge not by the eye but by the heart." - Native American Proverb

Re: Binary File IO

Jumpin' Jeff23-Jun-06 9:59

Jumpin' Jeff

23-Jun-06 9:59

Ok, I added the #pragma pack as you suggested, but left the type 9 characters, for when I changed it to 10, I came up with exactly what I did with David's example. The #pragma packs fixed the version data, but not the type. Still reads "File Type@", and I get 3 warnings...

warning C4081: expected 'newline'; found ';'
warning C4086: expected pragma parameter to be '1', '2', '4', '8', or '16'
warning C4081: expected 'newline';

Jeff

Re: Binary File IO

Joe Woodbury23-Jun-06 10:37

Joe Woodbury

23-Jun-06 10:37

My mistake, it should be #pragma pack()

For the compare, try strncmp(struct.string, realString, sizeof(struct.string))

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Entry Points into Exe files

Hibelton23-Jun-06 8:53

Hibelton

23-Jun-06 8:53

Here we have a simple entry point into a DLL

<br />
AFX_EXT_CLASS bool EntryPoint( void );<br />
<br />
and:<br />
<br />
bool EntryPoint()<br />
{<br />
    return true;<br />
}<br />

Which we can use with AfxLoadLibrary, and GetProcAddress. Yay and hooray! What I need is a way to do that with EXEs. See I need to be able to run some code dynamically based on files in a directory, and it has to work on both DLL's and EXE's. I thought I have read in the past about alternative entry points on EXE's, and you can load an EXE with AfxLoadLibrary, but you can't use GetProcAddress on it.

Re: Entry Points into Exe files

ovidiucucu24-Jun-06 7:22

ovidiucucu

24-Jun-06 7:22

Like form a DLL, you can export a function from an EXE as well.

Ovidiu Cucu
Microsoft MVP - Visual C++

Pointers [modified]

Jay0323-Jun-06 8:16

Jay03

23-Jun-06 8:16

Can someone tell me what is going on in the ObjectRoot constructor and also how the ObjectRootPtr is declared. Is the pointer pointing to a new array called ms_instances of size 21 and assigns a value of NULL to all ms_instance[0], ms_instance[1],.....ms_instance[20].....

PS: WHAT DOES THE SECOND LINE MEAN .... ARE YOU MAKING THE POINTER ObjectRootPtr point to class member ms_instances of size 21. I thought it was something like ObjectRootPtr = new ms_instances;

typedef ObjectRoot* ObjectRootPtr; <br />
static ObjectRootPtr ms_instances[MAX_INSTANCES];<br />
<br />
//! Static variable definition<br />
RTI::RTIambassador*          ObjectRoot::ms_rtiAmb     = NULL;   <br />
RTI::ObjectClassHandle       ObjectRoot::ms_classId    = 0;<br />
const char*                  ObjectRoot::ms_classIdStr = NULL;<br />
<br />
ObjectRootPtr   ObjectRoot::ms_instances[MAX_INSTANCES] =  // MAX_INSTANCES = 21<br />
{ NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,<br />
  NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL };<br />
unsigned int ObjectRoot::ms_numInstances = 0;<br />
<br />
ObjectRoot::ObjectRoot()<br />
{<br />
 //! Add this new object to the extent (collection) of all instances.<br />
   if (ms_numInstances < MAX_INSTANCES)  // ms_numInstances < 21<br />
      ObjectRoot::ms_instances[ ObjectRoot::ms_numInstances++ ] = this;<br />
}

-- modified at 14:19 Friday 23rd June, 2006

Re: Pointers

Jun Du23-Jun-06 8:52

Jun Du

23-Jun-06 8:52

I'll try to explain line by line.

static ObjectRootPtr ms_instances[MAX_INSTANCES];

Array of static pointers.

//! Static variable definition
RTI::RTIambassador* ObjectRoot::ms_rtiAmb = NULL;
RTI::ObjectClassHandle ObjectRoot::ms_classId = 0;
const char* ObjectRoot::ms_classIdStr = NULL;

Initialization of static and constant static data.

ObjectRootPtr ObjectRoot::ms_instances[MAX_INSTANCES] = // MAX_INSTANCES = 21
{ NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL };

Initialization of the static pointers defined by the second line above.

Jay03 wrote:
PS: WHAT DOES THE SECOND LINE MEAN .... ARE YOU MAKING THE POINTER ObjectRootPtr point to class member ms_instances of size 21. I thought it was something like ObjectRootPtr = new ms_instances;

No. It defines an array of pointers. No instantiation involved. It's easy to understand if you replace ObjectRootPtr with ObjectRoot*. The first line defines this replacement.

Best,
Jun

Re: Pointers

Jay0323-Jun-06 9:19

Jay03

23-Jun-06 9:19

For the first part..... what do STATIC POINTERS DO?

In the last part. ObjectRootPtr is pointer to an ObjectRoot object. Now this ObjectRootPtr was pointing to ms_instances[21] of size 21. And finally the ms_instances[21] points to NULL

I believe this is what you meant.

The big picture is:

ObjectRootPtr ---> ms_instances[0] --- > NULL
---> ms_instances[1] --- > NULL
---> ms_instances[2] --- > NULL
---> .............. --- > NULL
---> .............. --- > NULL
---> ms_instances[20] --- > NULL

BTW Thanks for your reply JUN Smile | :)

Re: Pointers

Zac Howland23-Jun-06 10:08

Zac Howland

23-Jun-06 10:08

The pointers are not static. The memory allocated to hold the pool of pointers is. Basically, they only want to have 21 instances (maximum) of this object. They created a pool to hold references for all active instances. At startup, those instances are initialized to NULL (since they don't point to anything).

The declaration static ObjectRootPtr ms_instances[21] is declaring a static array of 21 pointers to ObjectRoot objects.

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Re: Pointers

Jun Du23-Jun-06 10:30

Jun Du

23-Jun-06 10:30

You're right. It's a static array of pointers, not an array of static pointers. Thanks for pointing this out Rose | [Rose]

Best,
Jun

Re: Pointers

Jun Du23-Jun-06 10:15

Jun Du

23-Jun-06 10:15

Jay03 wrote:
For the first part..... what do STATIC POINTERS DO?

Static is in terms of scope. Like any static variable, a static pointer is shared by all instances of this class, rather than a specific instance. As a matter of fact, it exists before any instance is created. That is why we refer to it as <class_name>::<pointer_name>.

Jay03 wrote:
In the last part. ObjectRootPtr is pointer to an ObjectRoot object.

Correct.

Jay03 wrote:
Now this ObjectRootPtr was pointing to ms_instances[21] of size 21.

Well, a correct interpretation should be "Now you define a (static) array (say, 21) of such pointers (ObjectRootPtr)".

Best,
Jun

accessing an ftp server

LCI23-Jun-06 8:15

LCI

23-Jun-06 8:15

If i have an ftp server such as:
tennis.tournament.com:9662

Is there a way in a web browser to pull up that site and include the user id and password in the string so that this data is not prompted.

So for example:
tennis.tournament.com:9662:username:passwd

I know this is possible but the exact characters in between the user name and passwd i am not sure of.

Thanks,

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