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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* diffsorted -- a utility to compute a line-by-line diff on two
* sorted input files
*
* Copyright © 2019 Red Hat
*
* Author: J. Eric Ivancich
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation.
*/
/*
* SUMMARY
*
* The `diffsorted` utility does a line-by-line diff on two sorted text
* files and indicating lines that are in one file but not the other
* using diff-style notation (although line numbers are not indicated).
*
* USAGE
*
* rgw-diff-sorted file1.txt file2.txt
*
* NOTES
*
* Each files should have its lines in sorted order and should have no
* empty lines.
*
* A potential input file can be sorted using the `sort` utility provided
* that LANG=C to insure byte lexical order. For example:
*
* LANG=C sort unsorted.txt >sorted.txt
*
* or:
*
* export LANG=C
* sort unsorted.txt >sorted.txt
*
* EXIT STATUS
*
* 0 : files same
* 1 : files different
* 2 : usage problem (e.g., wrong number of command-line arguments)
* 3 : problem opening input file
* 4 : bad file content (e.g., unsorted order or empty lines)
*/
#include <iostream>
#include <fstream>
struct FileOfLines {
const char* filename;
std::ifstream input;
std::string this_line, prev_line;
bool next_eof;
bool is_eof;
FileOfLines(const char* _filename) :
filename(_filename),
input(filename),
next_eof(false),
is_eof(false)
{ }
void dump(const std::string& prefix) {
do {
std::cout << prefix << this_line << std::endl;
advance();
} while (!eof());
}
bool eof() const {
return is_eof;
}
bool good() const {
return input.good();
}
void advance() {
if (next_eof) {
is_eof = true;
return;
}
prev_line = this_line;
std::getline(input, this_line);
if (this_line.empty()) {
if (!input.eof()) {
std::cerr << "Error: " << filename << " has an empty line." <<
std::endl;
exit(4);
}
is_eof = true;
return;
} else if (input.eof()) {
next_eof = true;
}
if (this_line < prev_line) {
std::cerr << "Error: " << filename << " is not in sorted order; \"" <<
this_line << "\" follows \"" << prev_line << "\"." << std::endl;
exit(4);
}
}
const std::string line() const {
return this_line;
}
};
int main(int argc, const char* argv[]) {
if (argc != 3) {
std::cerr << "Usage: " << argv[0] << " <file1> <file2>" << std::endl;
exit(2);
}
FileOfLines input1(argv[1]);
if (!input1.good()) {
std::cerr << "Error opening " << argv[1] <<
"." << std::endl;
exit(3);
}
FileOfLines input2(argv[2]);
if (!input2.good()) {
std::cerr << "Error opening " << argv[2] <<
"." << std::endl;
exit(3);
}
bool files_same = true;
input1.advance();
input2.advance();
while (!input1.eof() && !input2.eof()) {
if (input1.line() == input2.line()) {
input1.advance();
input2.advance();
} else if (input1.line() < input2.line()) {
files_same = false;
std::cout << "< " << input1.line() << std::endl;
input1.advance();
} else {
files_same = false;
std::cout << "> " << input2.line() << std::endl;
input2.advance();
}
}
if (!input1.eof()) {
files_same = false;
input1.dump("< ");
} else if (!input2.eof()) {
files_same = false;
input2.dump("> ");
}
if (files_same) {
exit(0);
} else {
exit(1);
}
}
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