Reading and writing binary file

Question

I m trying to write code to read a binary file into a buffer  then write the buffer to another file   I have the following code  but the buffer only stores a couple of ASCII characters from the first line in the file and nothing else   int length  char   buffer   ifstream is  is open   C   Final gif   ios  binary       get length of file  is seekg  0  ios  end   length   is tellg    is seekg  0  ios  beg      allocate memory  buffer   new char  length      read data as a block  is read  buffer length   is close     FILE  pFile  pFile   fopen   C   myfile gif    w    fwrite  buffer   1   sizeof buffer    pFile

User · Answer

You should pass length into fwrite instead of sizeof buffer

User · Answer

sizeof buffer     sizeof char      Use length instead   Also  better to use fopen with  wb

User · Answer

There is a much simpler way  This does not care if it is binary or text file  Use noskipws  char buf SZ   ifstream f  quot file quot    int i  for i 0  f  gt  gt  noskipws  gt  gt  buffer i   i     ofstream f2  quot writeto quot    for int j 0  j  lt  i  j    f2  lt  lt  noskipws  lt  lt  buffer j    Or you can just use string instead of the buffer  string s  char c  ifstream f  quot image jpg quot    while f  gt  gt  noskipws  gt  gt  c  s    c  ofstream f2  quot copy jpg quot    f2  lt  lt  s   normally stream skips white space characters like space or new line  tab and all other control characters  But noskipws makes all the characters transferred  So this will not only copy a text file but also a binary file  And stream uses buffer internally  I assume the speed won t be slow

User · Answer

It can be done with simple commands in the following snippet   Copies the whole file of any size  No size constraint   Just use this  Tested And Working     include lt iostream gt   include lt fstream gt  using namespace std  int main       ifstream infile    infile open  source pdf  ios  binary ios  in      ofstream outfile    outfile open  temppdf pdf  ios  binary ios  out      int buffer 2     while infile read  char    amp buffer sizeof buffer              outfile write  char    amp buffer sizeof buffer           infile close      outfile close      return 0      Having a smaller buffer size would be helpful in copying tiny files  Even  char buffer 2   would do the job

User · Answer

If you want to do this the C   way  do it like this    include  lt fstream gt   include  lt iterator gt   include  lt algorithm gt   int main         std  ifstream input   C   Final gif   std  ios  binary        std  ofstream output   C   myfile gif   std  ios  binary         std  copy           std  istreambuf iterator lt char gt  input            std  istreambuf iterator lt char gt              std  ostreambuf iterator lt char gt  output        If you need that data in a buffer to modify it or something  do this    include  lt fstream gt   include  lt iterator gt   include  lt vector gt   int main         std  ifstream input   C   Final gif   std  ios  binary            copies all data into buffer     std  vector lt unsigned char gt  buffer std  istreambuf iterator lt char gt  input

User · Answer

Here is a short example  the C   way using rdbuf   I got this from the web   I can t find my original source on this      include  lt fstream gt   include  lt iostream gt   int main         std  ifstream f1   C   me txt  std  fstream  binary      std  ofstream f2   C   me2 doc  std  fstream  trunc std  fstream  binary      f2 lt  lt f1 rdbuf       return 0

User · Answer

sizeof buffer  is the size of a pointer on your last line NOT the actual size of the buffer  You need to use  length  that you already established instead

User · Answer

Here is implementation of standard C   14 using vectors and tuples to Read and Write Text Binary and Hex files  Snippet code   try   if  file type    BINARY FILE           Open the stream in binary mode        std  ifstream bin file file name  std  ios  binary        if  bin file good                Read Binary data using streambuffer iterators            std  vector lt uint8 t gt  v buf  std  istreambuf iterator lt char gt  bin file     std  istreambuf iterator lt char gt               vec buf   v buf          bin file close               else           throw std  exception              else if  file type    ASCII FILE           Open the stream in default mode        std  ifstream ascii file file name       string ascii data       if  ascii file good                Read ASCII data using getline           while  getline ascii file  ascii data               str buf    ascii data    quot  n quot            ascii file close              else           throw std  exception             else if  file type    HEX FILE           Open the stream in default mode        std  ifstream hex file file name        if  hex file good                Read Hex data using streambuffer iterators            std  vector lt char gt  h buf  std  istreambuf iterator lt char gt  hex file     std  istreambuf iterator lt char gt               string hex str buf h buf begin    h buf end             hex buf   hex str buf           hex file close              else           throw std  exception               Full Source code can be found here

[c++] Reading and writing binary file

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