b7d418131d
* [file_utils] spin-off syscall-related file operations 1. Eliminate the potential circular dependency between persistent-data/block.h and persistent-data/file_utils.h, if the former one wants to include the latter. 2. Avoid namespace pollution by removing the "using namespace std" declaration in block.tcc. 3. Correct the header hierarchy: base/xml_utils.h now no longer depends on the higher-level persistent-data/file_utils.h * [file_utils] support block files in get_file_length()
144 lines
3.4 KiB
C++
144 lines
3.4 KiB
C++
#include "base/file_utils.h"
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#include "base/error_string.h"
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#include <sstream>
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#include <stdexcept>
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#include <linux/fs.h>
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#include <sys/ioctl.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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//----------------------------------------------------------------
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// FIXME: give this namespace a name
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namespace {
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using namespace std;
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int const DEFAULT_MODE = 0666;
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int const OPEN_FLAGS = O_DIRECT;
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// FIXME: introduce a new exception for this, or at least lift this
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// to exception.h
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void syscall_failed(char const *call) {
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ostringstream out;
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out << "syscall '" << call << "' failed: " << base::error_string(errno);
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throw runtime_error(out.str());
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}
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void syscall_failed(string const &call, string const &message)
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{
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ostringstream out;
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out << "syscall '" << call << "' failed: " << base::error_string(errno) << "\n"
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<< message;
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throw runtime_error(out.str());
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}
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}
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//----------------------------------------------------------------
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int
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file_utils::open_file(string const &path, int flags) {
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int fd = ::open(path.c_str(), OPEN_FLAGS | flags, DEFAULT_MODE);
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if (fd < 0)
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syscall_failed("open",
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"Note: you cannot run this tool with these options on live metadata.");
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return fd;
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}
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bool
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file_utils::file_exists(string const &path) {
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struct ::stat info;
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int r = ::stat(path.c_str(), &info);
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if (r) {
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if (errno == ENOENT)
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return false;
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syscall_failed("stat");
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return false; // never get here
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} else
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return S_ISREG(info.st_mode) || S_ISBLK(info.st_mode);
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}
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void
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file_utils::check_file_exists(string const &file) {
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struct stat info;
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int r = ::stat(file.c_str(), &info);
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if (r)
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throw runtime_error("Couldn't stat file");
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if (!S_ISREG(info.st_mode))
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throw runtime_error("Not a regular file");
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}
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int
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file_utils::create_block_file(string const &path, off_t file_size) {
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if (file_exists(path)) {
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ostringstream out;
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out << __FUNCTION__ << ": file '" << path << "' already exists";
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throw runtime_error(out.str());
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}
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int fd = open_file(path, O_CREAT | O_EXCL | O_RDWR);
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int r = ::ftruncate(fd, file_size);
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if (r < 0)
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syscall_failed("ftruncate");
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return fd;
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}
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int
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file_utils::open_block_file(string const &path, off_t min_size, bool writeable, bool excl) {
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if (!file_exists(path)) {
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ostringstream out;
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out << __FUNCTION__ << ": file '" << path << "' doesn't exist";
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throw runtime_error(out.str());
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}
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int flags = writeable ? O_RDWR : O_RDONLY;
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if (excl)
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flags |= O_EXCL;
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return open_file(path, flags);
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}
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uint64_t
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file_utils::get_file_length(string const &file) {
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struct stat info;
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uint64_t nr_bytes;
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int r = ::stat(file.c_str(), &info);
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if (r)
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throw runtime_error("Couldn't stat path");
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if (S_ISREG(info.st_mode))
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// It's okay to cast st_size to a uint64_t value.
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// If LFS is enabled, st_size should not be negative for regular files.
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nr_bytes = static_cast<uint64_t>(info.st_size);
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else if (S_ISBLK(info.st_mode)) {
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// To get the size of a block device we need to
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// open it, and then make an ioctl call.
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int fd = ::open(file.c_str(), O_RDONLY);
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if (fd < 0)
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throw runtime_error("couldn't open block device to ascertain size");
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r = ::ioctl(fd, BLKGETSIZE64, &nr_bytes);
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if (r) {
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::close(fd);
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throw runtime_error("ioctl BLKGETSIZE64 failed");
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}
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::close(fd);
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} else
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// FIXME: needs a better message
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throw runtime_error("bad path");
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return nr_bytes;
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}
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//----------------------------------------------------------------
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