forked from lix-project/lix
447089a5f6
Nix. This is to prevent Berkeley DB from becoming wedged. Unfortunately it is not possible to throw C++ exceptions from a signal handler. In fact, you can't do much of anything except change variables of type `volatile sig_atomic_t'. So we set an interrupt flag in the signal handler and check it at various strategic locations in the code (by calling checkInterrupt()). Since this is unlikely to cover all cases (e.g., (semi-)infinite loops), sometimes SIGTERM may now be required to kill Nix.
327 lines
7.6 KiB
C++
327 lines
7.6 KiB
C++
#include <cerrno>
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#include <algorithm>
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#include <vector>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include "archive.hh"
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#include "util.hh"
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static string archiveVersion1 = "nix-archive-1";
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static void writePadding(unsigned int len, DumpSink & sink)
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{
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if (len % 8) {
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unsigned char zero[8];
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memset(zero, 0, sizeof(zero));
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sink(zero, 8 - (len % 8));
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}
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}
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static void writeInt(unsigned int n, DumpSink & sink)
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{
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unsigned char buf[8];
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memset(buf, 0, sizeof(buf));
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buf[0] = n & 0xff;
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buf[1] = (n >> 8) & 0xff;
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buf[2] = (n >> 16) & 0xff;
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buf[3] = (n >> 24) & 0xff;
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sink(buf, sizeof(buf));
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}
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static void writeString(const string & s, DumpSink & sink)
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{
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unsigned int len = s.length();
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writeInt(len, sink);
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sink((const unsigned char *) s.c_str(), len);
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writePadding(len, sink);
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}
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static void dump(const string & path, DumpSink & sink);
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static void dumpEntries(const Path & path, DumpSink & sink)
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{
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Strings names = readDirectory(path);
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vector<string> names2(names.begin(), names.end());
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sort(names2.begin(), names2.end());
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for (vector<string>::iterator it = names2.begin();
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it != names2.end(); it++)
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{
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writeString("entry", sink);
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writeString("(", sink);
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writeString("name", sink);
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writeString(*it, sink);
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writeString("node", sink);
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dump(path + "/" + *it, sink);
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writeString(")", sink);
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}
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}
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static void dumpContents(const Path & path, unsigned int size,
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DumpSink & sink)
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{
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writeString("contents", sink);
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writeInt(size, sink);
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AutoCloseFD fd = open(path.c_str(), O_RDONLY);
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if (fd == -1) throw SysError(format("opening file `%1%'") % path);
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unsigned char buf[65536];
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unsigned int total = 0;
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ssize_t n;
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while ((n = read(fd, buf, sizeof(buf)))) {
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checkInterrupt();
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if (n == -1) throw SysError("reading file " + path);
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total += n;
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sink(buf, n);
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}
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if (total != size)
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throw SysError("file changed while reading it: " + path);
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writePadding(size, sink);
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}
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static void dump(const Path & path, DumpSink & sink)
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{
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struct stat st;
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if (lstat(path.c_str(), &st))
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throw SysError(format("getting attributes of path `%1%'") % path);
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writeString("(", sink);
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if (S_ISREG(st.st_mode)) {
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writeString("type", sink);
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writeString("regular", sink);
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if (st.st_mode & S_IXUSR) {
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writeString("executable", sink);
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writeString("", sink);
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}
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dumpContents(path, st.st_size, sink);
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}
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else if (S_ISDIR(st.st_mode)) {
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writeString("type", sink);
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writeString("directory", sink);
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dumpEntries(path, sink);
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}
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else if (S_ISLNK(st.st_mode)) {
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writeString("type", sink);
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writeString("symlink", sink);
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writeString("target", sink);
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writeString(readLink(path), sink);
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}
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else throw Error("unknown file type: " + path);
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writeString(")", sink);
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}
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void dumpPath(const Path & path, DumpSink & sink)
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{
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writeString(archiveVersion1, sink);
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dump(path, sink);
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}
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static Error badArchive(string s)
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{
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return Error("bad archive: " + s);
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}
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static void readPadding(unsigned int len, RestoreSource & source)
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{
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if (len % 8) {
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unsigned char zero[8];
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unsigned int n = 8 - (len % 8);
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source(zero, n);
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for (unsigned int i = 0; i < n; i++)
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if (zero[i]) throw badArchive("non-zero padding");
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}
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}
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static unsigned int readInt(RestoreSource & source)
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{
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unsigned char buf[8];
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source(buf, sizeof(buf));
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if (buf[4] || buf[5] || buf[6] || buf[7])
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throw Error("implementation cannot deal with > 32-bit integers");
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return
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buf[0] |
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(buf[1] << 8) |
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(buf[2] << 16) |
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(buf[3] << 24);
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}
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static string readString(RestoreSource & source)
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{
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unsigned int len = readInt(source);
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char buf[len];
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source((unsigned char *) buf, len);
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readPadding(len, source);
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return string(buf, len);
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}
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static void skipGeneric(RestoreSource & source)
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{
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if (readString(source) == "(") {
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while (readString(source) != ")")
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skipGeneric(source);
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}
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}
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static void restore(const Path & path, RestoreSource & source);
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static void restoreEntry(const Path & path, RestoreSource & source)
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{
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string s, name;
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s = readString(source);
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if (s != "(") throw badArchive("expected open tag");
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while (1) {
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checkInterrupt();
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s = readString(source);
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if (s == ")") {
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break;
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} else if (s == "name") {
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name = readString(source);
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} else if (s == "node") {
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if (s == "") throw badArchive("entry name missing");
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restore(path + "/" + name, source);
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} else {
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throw badArchive("unknown field " + s);
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skipGeneric(source);
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}
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}
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}
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static void restoreContents(int fd, const Path & path, RestoreSource & source)
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{
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unsigned int size = readInt(source);
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unsigned int left = size;
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unsigned char buf[65536];
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while (left) {
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checkInterrupt();
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unsigned int n = sizeof(buf);
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if (n > left) n = left;
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source(buf, n);
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if (write(fd, buf, n) != (ssize_t) n)
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throw SysError("writing file " + path);
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left -= n;
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}
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readPadding(size, source);
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}
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static void restore(const Path & path, RestoreSource & source)
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{
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string s;
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s = readString(source);
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if (s != "(") throw badArchive("expected open tag");
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enum { tpUnknown, tpRegular, tpDirectory, tpSymlink } type = tpUnknown;
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AutoCloseFD fd;
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while (1) {
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checkInterrupt();
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s = readString(source);
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if (s == ")") {
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break;
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}
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else if (s == "type") {
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if (type != tpUnknown)
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throw badArchive("multiple type fields");
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string t = readString(source);
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if (t == "regular") {
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type = tpRegular;
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fd = open(path.c_str(), O_CREAT | O_EXCL | O_WRONLY, 0666);
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if (fd == -1)
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throw SysError("creating file " + path);
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}
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else if (t == "directory") {
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type = tpDirectory;
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if (mkdir(path.c_str(), 0777) == -1)
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throw SysError("creating directory " + path);
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}
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else if (t == "symlink") {
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type = tpSymlink;
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}
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else throw badArchive("unknown file type " + t);
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}
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else if (s == "contents" && type == tpRegular) {
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restoreContents(fd, path, source);
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}
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else if (s == "executable" && type == tpRegular) {
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readString(source);
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struct stat st;
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if (fstat(fd, &st) == -1)
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throw SysError("fstat");
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if (fchmod(fd, st.st_mode | (S_IXUSR | S_IXGRP | S_IXOTH)) == -1)
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throw SysError("fchmod");
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}
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else if (s == "entry" && type == tpDirectory) {
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restoreEntry(path, source);
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}
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else if (s == "target" && type == tpSymlink) {
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string target = readString(source);
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if (symlink(target.c_str(), path.c_str()) == -1)
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throw SysError("creating symlink " + path);
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}
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else {
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throw badArchive("unknown field " + s);
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skipGeneric(source);
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}
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}
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}
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void restorePath(const Path & path, RestoreSource & source)
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{
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if (readString(source) != archiveVersion1)
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throw badArchive("expected Nix archive");
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restore(path, source);
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}
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