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std::memcmp(3)		       C++ Standard Libary		  std::memcmp(3)

NAME
     std::memcmp - std::memcmp

Synopsis
	Defined in header <cstring>
	int memcmp( const void* lhs, const void* rhs, std::size_t count );

	Reinterprets the objects pointed to by lhs and rhs as arrays of unsigned
     char and
	compares the first count bytes of these arrays. The comparison is done
	lexicographically.

	The  sign of the result is the sign of the difference between the values
     of the first
	pair of bytes (both interpreted as unsigned char) that differ in the ob-
     jects being
	compared.

Parameters
	lhs, rhs - pointers to the memory buffers to compare
	count	 - number of bytes to examine

Return value
	Negative value if the first differing byte  (reinterpreted  as	unsigned
     char) in lhs
	is less than the corresponding byte in rhs.

	0 if all count bytes of lhs and rhs are equal.

	Positive  value  if  the first differing byte in lhs is greater than the
     corresponding
	byte in rhs.

Notes
	This function reads object representations, not the object  values,  and
     is typically
	meaningful for only trivially-copyable objects that have no padding. For
     example,
	memcmp() between two objects of type std::string or std::vector will not
     compare
	their  contents,  memcmp()  between two objects of type struct { char c;
     int n; } will
	compare the padding bytes whose values may differ when the values  of  c
     and n are the
	same, and even if there were no padding bytes, the int would be compared
     without
	taking into account endianness.

Example
     // Run this code

      #include <cstring>
      #include <iostream>

      void demo(const char* lhs, const char* rhs, std::size_t sz)
      {
	  std::cout << std::string(lhs, sz);
	  const int rc = std::memcmp(lhs, rhs, sz);
	  if (rc < 0)
	      std::cout << " precedes ";
	  else if (rc > 0)
	      std::cout << " follows ";
	  else
	      std::cout << " compares equal to ";
	  std::cout << std::string(rhs, sz) << " in lexicographical order\n";
      }

      int main()
      {
	  char a1[] = {'a', 'b', 'c'};
	  char a2[sizeof a1] = {'a', 'b', 'd'};

	  demo(a1, a2, sizeof a1);
	  demo(a2, a1, sizeof a1);
	  demo(a1, a1, sizeof a1);
      }

Output:
      abc precedes abd in lexicographical order
      abd follows abc in lexicographical order
      abc compares equal to abc in lexicographical order

See also
	strcmp	compares two strings
		(function)
	strncmp compares a certain number of characters from two strings
		(function)
	C documentation for
	memcmp

http://cppreference.com 	   2024.06.10			  std::memcmp(3)
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