How do I print bytes as hexadecimal

Question

I know in C  you can use String Format method  But how do you do this in C    Is there a function that allows me to convert a byte to a Hex   Just need to convert a 8 byte long data to Hex  how do I do that

User · Answer

I don t know of a better way than   unsigned char byData xxx     int nLength   sizeof byData    2  char  pBuffer   new char nLength   1   pBuffer nLength    0  for  int i   0  i  lt  sizeof byData   i          sprintf pBuffer 2   i     02X   byData i        You can speed it up by using a Nibble to Hex method  unsigned char byData xxx    const char szNibbleToHex      0123456789ABCDEF      int nLength   sizeof byData    2  char  pBuffer   new char nLength   1   pBuffer nLength    0  for  int i   0  i  lt  sizeof byData   i             divide by 16     int nNibble   byData i   gt  gt  4      pBuffer 2   i     pszNibbleToHex nNibble        nNibble   byData i   amp  0x0F      pBuffer 2   i   1     pszNibbleToHex nNibble

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Printing arbitrary structures in modern C    All answers so far only tell you how to print an array of integers  but we can also print any arbitrary structure  given that we know its size  The example below creates such structure and iterates a pointer through its bytes  printing them to the output    include  lt iostream gt   include  lt iomanip gt   include  lt cstring gt   using std  cout  using std  endl  using std  hex  using std  setfill  using std  setw   using u64   unsigned long long  using u16   unsigned short  using f64   double   struct Header       u16 version      u16 msgSize      struct Example       Header header      u64 someId      u64 anotherId      bool isFoo      bool isBar      f64 floatingPointValue      int main          Example example         fill with zeros so padding regions don t contain garbage     memset  amp example  0  sizeof Example        example header version   5      example header msgSize   sizeof Example  - sizeof Header       example someId   0x1234      example anotherId   0x5678      example isFoo   true      example isBar   true      example floatingPointValue   1 1       cout  lt  lt  hex  lt  lt  setfill  0        needs to be set only once     auto  ptr   reinterpret cast lt unsigned char   gt   amp example       for  int i   0  i  lt  sizeof Example   i    ptr              if  i   sizeof u64     0                cout  lt  lt  endl                    cout  lt  lt  setw 2   lt  lt  static cast lt unsigned gt   ptr   lt  lt                  return 0      And here s the output   05 00 24 00 00 00 00 00  34 12 00 00 00 00 00 00  78 56 00 00 00 00 00 00  01 01 00 00 00 00 00 00  9a 99 99 99 99 99 f1 3f   Notice this example also illustrates memory alignment working  We see version occupying 2 bytes  05 00   followed by msgSize with 2 more bytes  24 00  and then 4 bytes of padding  after which comes someId  34 12 00 00 00 00 00 00  and anotherId  78 56 00 00 00 00 00 00   Then isFoo  which occupies 1 byte  01  and isBar  another byte  01   followed by 6 bytes of padding  finally ending with the IEEE 754 standard representation of the double field floatingPointValue   Also notice that all values are represented as little endian  least significant bytes come first   since this was compiled and run on an Intel platform

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This is a modified version of the Nibble to Hex method  void hexArrayToStr unsigned char  info  unsigned int infoLength  char   buffer        const char  pszNibbleToHex     0123456789ABCDEF        int nNibble  i      if  infoLength  gt  0            if  info    NULL                 buffer    char    malloc  infoLength   2    1               buffer 0   infoLength   2     0              for  i   0  i  lt  infoLength  i                      nNibble   info i   gt  gt  4                  buffer 0  2   i    pszNibbleToHex nNibble                   nNibble   info i   amp  0x0F                  buffer 0  2   i   1    pszNibbleToHex nNibble                           else                buffer   NULL                  else            buffer   NULL

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Yet another answer  in case the byte array is defined as char    uppercase and separated by spaces  void debugArray const unsigned char  data  size t len        std  ios base  fmtflags f  std  cout flags          for  size t i   0  i  lt  len    i          std  cout  lt  lt  std  uppercase  lt  lt  std  hex  lt  lt  std  setfill  0    lt  lt  std  setw 2   lt  lt     int data i    amp  0xFF   lt  lt   quot   quot       std  cout  lt  lt  std  endl      std  cout flags  f       Example  unsigned char test    0x01  0x02  0x03  0x04  0x05  0x06   debugArray test  sizeof test     Output  01 02 03 04 05 06

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If you want to use C   streams rather than C functions  you can do the following   int ar       20  30  40  50  60  70  80  90    const int siz ar   sizeof ar    sizeof int    for  int i   0  i  lt  siz ar    i      cout  lt  lt  ar i   lt  lt       cout  lt  lt  endl   for  int i   0  i  lt  siz ar    i      cout  lt  lt  hex  lt  lt  setfill  0    lt  lt  setw 2   lt  lt  ar i   lt  lt       cout  lt  lt  endl    Very simple   Output   20 30 40 50 60 70 80 90 14 1e 28 32 3c 46 50 5a

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C   static void print buf const char  title  const unsigned char  buf  size t buf len        size t i   0      fprintf stdout    s n   title       for i   0  i  lt  buf len    i      fprintf stdout    02X s   buf i                  i   1     16    0     r n                C     void print bytes std  ostream amp  out  const char  title  const unsigned char  data  size t dataLen  bool format   true        out  lt  lt  title  lt  lt  std  endl      out  lt  lt  std  setfill  0        for size t i   0  i  lt  dataLen    i            out  lt  lt  std  hex  lt  lt  std  setw 2   lt  lt   int data i           if  format                out  lt  lt     i   1    16    0      n                              out  lt  lt  std  endl

User · Answer

Well you can convert one byte  unsigned char  at a time into a array like so  char buffer  17   buffer 16    0  for j   0  j  lt  8  j        sprintf  amp buffer 2 j     02X   data j

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Use C   streams and restore state afterwards  This is a variation of How do I print bytes as hexadecimal  but    runnable considering that this alters the state of cout and trying to restore it at the end as asked at  Restore the state of std  cout after manipulating it   main cpp   include  lt iomanip gt   include  lt iostream gt   int main         int array      0  0x8  0x10  0x18       constexpr size t size   sizeof array    sizeof array 0            Sanity check decimal print      for  size t i   0  i  lt  size    i          std  cout  lt  lt  array i   lt  lt           std  cout  lt  lt  std  endl          Hex print and restore default afterwards      std  ios cout state nullptr       cout state copyfmt std  cout       std  cout  lt  lt  std  hex  lt  lt  std  setfill  0    lt  lt  std  setw 2       for  size t i   0  i  lt  size    i          std  cout  lt  lt  array i   lt  lt           std  cout  lt  lt  std  endl      std  cout copyfmt cout state           Check that cout state was restored      for  size t i   0  i  lt  size    i          std  cout  lt  lt  array i   lt  lt           std  cout  lt  lt  std  endl      Compile and run   g   -o main out -std c  11 main cpp   main out   Output   0 8 16 24  00 8 10 18  0 8 16 24   Tested on Ubuntu 16 04  GCC 6 4 0

[c++] How do I print bytes as hexadecimal?

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