read long 4 bytes in 140th position and 176 position

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Hi i am havinig file.
file size 1200

i am reading the file thru ifstream.

C#

outHdrFile.seekg(0, ios::end);
       long Hdrlen = outHdrFile.tellg();
       ifstream::pos_type HdrPtr;
       HdrPtr = Hdrlen;// - headerSize;
       BYTE* HdrFileBuff = new BYTE[HdrBufferSize];
       outHdrFile.seekg (140, ios::beg);
       outHdrFile.read((char*)HdrFileBuff,HdrPtr);

reading 4 bytes from 140th postion and write that into a temp file with same position 140th .in 140th position 6 is there and i have to update 6100 there.

pls tell me how to update in minimum lines.

thanks

Posted 18-Aug-12 2:43am

JOYKAIGA1

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Richard MacCutchan · Answer 1 · 2012-08-18T03:04:00

Solution 1

Forget about seeking when doing this type of transction; do it this way:

Read the next N bytes of input file (in this case 140).
Write those bytes to the output file.
Read the next N bytes (4).
Modify the value just read.
Write the modified value to the output file.
Repeat until all data is copied.

Posted 18-Aug-12 3:04am

Richard MacCutchan

Comments

JOYKAIGA1 18-Aug-12 9:15am

how to print in ascii of that long data type?

Richard MacCutchan 18-Aug-12 11:09am

Any way you like, it all depends what it represents. You could print it as 4 bytes, 2 half words or 1 whole word. You can use printf() or one of its variants with the X format specifier, or cout with the hex manipulator.

Sergey Alexandrovich Kryukov 18-Aug-12 17:59pm

Makes full sense, a 5.
--SA