108 lines
3.1 KiB
C++
108 lines
3.1 KiB
C++
#include <iostream>
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#include <fstream>
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#include <string>
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#include <sys/stat.h>
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#include <cerrno>
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#include <cstdlib>
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#include <climits>
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static bool file_exists(const std::string &path) {
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struct stat st{};
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return ::stat(path.c_str(), &st) == 0; // stat success => exists [web:59]
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}
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static std::string make_out_name(const std::string &in) {
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std::size_t pos = in.find_last_of('.');
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if (pos == std::string::npos) return in + ".out";
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return in.substr(0, pos) + ".out";
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}
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static void print_usage(const char* prog) {
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std::cerr << "Usage: " << prog << " <input_file> <replace_count>\n"; // positional args [web:59]
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}
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static bool parse_ll(const char* s, long long& out) {
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if (!s || !*s) return false;
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errno = 0;
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char* end = nullptr;
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long long v = std::strtoll(s, &end, 10); // use endptr and errno [web:59]
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if (errno == ERANGE) return false;
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if (end == s || *end != '\0') return false;
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out = v;
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return true;
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}
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int main(int argc, char* argv[]) {
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if (argc != 3) {
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print_usage(argv[0]);
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return -1;
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}
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std::string in_path = argv[1];
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long long replace_limit = 0;
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if (!parse_ll(argv[2], replace_limit) || replace_limit < 0) {
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std::cerr << "Error: replace_count must be a non-negative integer.\n";
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return -1;
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}
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if (!file_exists(in_path)) {
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std::cerr << "Error: input file does not exist.\n";
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return -1;
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}
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std::ifstream in(in_path);
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if (!in) {
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std::cerr << "Error: cannot open input file.\n";
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return -1;
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}
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std::string out_path = make_out_name(in_path);
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std::ofstream out(out_path);
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if (!out) {
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std::cerr << "Error: cannot create output file.\n";
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return -1;
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}
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long long performed = 0;
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std::string line;
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while (performed < replace_limit && std::getline(in, line)) { // stop early when limit hit [web:59]
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if (!line.empty()) {
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char first = line.front();
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for (char &c: line) {
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if (c == first && c != ' ') {
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c = ' ';
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++performed;
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if (performed >= replace_limit) break; // cap reached [web:44]
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}
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}
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}
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out << line;
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if (!in.eof()) out << '\n';
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if (!out) {
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std::cerr << "Error: write error.\n";
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return -1;
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}
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}
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// If limit reached mid-file, copy the rest unchanged
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if (performed >= replace_limit) { // stream may be mid-line or between lines [web:59]
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// Write remaining lines as-is
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if (!in.eof()) {
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// Flush any remaining part of current line already written; then dump rest
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std::string rest;
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while (std::getline(in, rest)) {
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out << rest;
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if (!in.eof()) out << '\n';
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if (!out) {
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std::cerr << "Error: write error.\n";
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return -1;
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}
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}
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}
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}
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std::cout << performed << std::endl; // print actual replacements up to limit [web:59]
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return 0; // success [web:59]
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}
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