--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dep/animia/src/fd/linux.cc	Sun Nov 12 04:53:19 2023 -0500
@@ -0,0 +1,132 @@
+#include <algorithm>
+#include <fcntl.h>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <unordered_map>
+#include <vector>
+#include <cstring>
+#include <dirent.h>
+
+#include "animia/util.h"
+
+#define PROC_LOCATION "/proc"
+
+namespace animia::internal::linux {
+
+/* this uses dirent instead of std::filesystem; it would make a bit
+   more sense to use the latter, but this is platform dependent already :) */
+std::vector<std::string> GetAllFilesInDir(const std::string& _dir) {
+	std::vector<std::string> ret;
+
+	DIR* dir = opendir(_dir.c_str());
+	if (!dir)
+		return ret;
+
+	struct dirent* dp;
+	while ((dp = readdir(dir)) != NULL) {
+		if (!(!strcmp(dp->d_name, ".") || !strcmp(dp->d_name, "..")))
+			ret.push_back(_dir + "/" + dp->d_name);
+	}
+
+	closedir(dir);
+	return ret;
+}
+
+std::string Basename(const std::string& path) {
+	return path.substr(path.find_last_of("/") + 1, path.length());
+}
+
+static bool IsRegularFile(std::string link) {
+	struct stat sb;
+	if (stat(link.c_str(), &sb) == -1)
+		return false;
+	return S_ISREG(sb.st_mode);
+}
+
+static bool AreFlagsOk(pid_t pid, int fd) {
+	const std::string path = PROC_LOCATION "/" + std::to_string(pid) + "/fdinfo/" + std::to_string(fd);
+	std::stringstream buffer(util::ReadFile(path));
+
+	int flags = 0;
+	for (std::string line; std::getline(buffer, line);) {
+		/* FIXME: exception handling here!! */
+		if (line.rfind("flags:", 0) == 0) {
+			flags = std::stoi(line.substr(line.find_last_not_of("0123456789") + 1));
+		}
+	}
+	if (flags & O_WRONLY || flags & O_RDWR)
+		return false;
+	return true;
+}
+
+static std::string GetFilenameFromFd(std::string link) {
+	/* gets around stupid linux limitation where /proc doesn't
+	   give actual filesize readings */
+	size_t  exe_size = 1024;
+	ssize_t exe_used;
+	std::string ret;
+
+	while (1) {
+		ret = std::string(exe_size, '\0');
+		exe_used = readlink(link.c_str(), &ret.front(), ret.length());
+		if (exe_used == (ssize_t)-1)
+			return NULL;
+
+		if (exe_used < (ssize_t)1) {
+			errno = ENOENT;
+			return NULL;
+		}
+
+		if (exe_used < (ssize_t)(exe_size - 1))
+			break;
+
+		exe_size += 1024;
+	}
+
+	return ret.c_str();
+}
+
+bool GetAllPids(std::set<pid_t>& pids) {
+	for (const auto& dir : get_all_files_in_dir(PROC_LOCATION)) {
+		pid_t pid;
+		try {
+			pid = std::stoul(basename(dir));
+		} catch (std::invalid_argument) {
+			continue;
+		}
+		pids.push_back(pid);
+	}
+}
+
+bool GetProcessName(pid_t pid, std::string& result) {
+	const std::string path = PROC_LOCATION "/" + std::to_string(pid) + "/comm";
+
+	std::string result = util::ReadFile(path);
+	result.erase(std::remove(result.begin(), result.end(), '\n'), result.end());
+}
+
+bool EnumerateOpenFiles(const std::set<pid_t>& pids, std::vector<std::tuple<pid_t, std::string>>& files) {
+	for (const auto& pid : pids) {
+		const std::string path = PROC_LOCATION "/" + std::to_string(pid) + "/fd";
+
+		for (const auto& dir : GetAllFilesInDir(path)) {
+			if (!AreFlagsOk(pid, std::stoi(basename(dir))))
+				continue;
+
+			std::string name = GetFilenameFromFd(dir);
+
+			if (!IsRegularFile(name))
+				continue;
+
+			files.push_back({pid, name});
+		}
+	}
+	return true;
+}
+
+} // namespace animia::internal::linux