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Author(s) Olivier Martin, Cyril Pletinckx, Minh-Phuong Tran
Deadline No deadline
Submission limit No limitation
Category tags s5, category_mmap, category_file, level4

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[S5] Reading integers in a binary file

Estimated time: 25 minutes

Given a binary file containing some (possibly none) positive integers (int) that were stored in a file, write a code that computes the sum of all of these integers. The function returns the sum when there are no errors. In case of errors, it returns.

  • If open() fails, return -1.
  • If close() fails, return -2.
  • If mmap() fails, return -3.
  • If munmap() fails, return -4.
  • If fstat() fails, return -5.

You can only use open(2), mmap(2), munmap(2), fstat(2) and close(2).

Hint : fstat(2) is mandatory to know the size of the file and thus with a simple formula, the number of integers that are stored in it (find it !).

Write your code here 
/*
 * @pre filename != NULL, name of the file
 * @post returns the sum of all integers stored in the binary file.
 *       return -1 if the file can not be open.
 *       return -2 if the file can not be closed.
 *       return -3 if mmap() fails.
 *       return -4 if munmap() fails.
 *       return -5 if fstat() fails.
 */
int sum_file(char *filename) {