lix/src/store.cc

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#include <iostream>
#include <sys/types.h>
#include <sys/wait.h>
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#include "store.hh"
#include "globals.hh"
#include "db.hh"
#include "archive.hh"
#include "pathlocks.hh"
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#include "normalise.hh"
struct CopySink : DumpSink
{
int fd;
virtual void operator () (const unsigned char * data, unsigned int len)
{
writeFull(fd, data, len);
}
};
struct CopySource : RestoreSource
{
int fd;
virtual void operator () (unsigned char * data, unsigned int len)
{
readFull(fd, data, len);
}
};
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void copyPath(string src, string dst)
{
debug(format("copying `%1%' to `%2%'") % src % dst);
/* Unfortunately C++ doesn't support coprocedures, so we have no
nice way to chain CopySink and CopySource together. Instead we
fork off a child to run the sink. (Fork-less platforms should
use a thread). */
/* Create a pipe. */
int fds[2];
if (pipe(fds) == -1) throw SysError("creating pipe");
/* Fork. */
pid_t pid;
switch (pid = fork()) {
case -1:
throw SysError("unable to fork");
case 0: /* child */
try {
close(fds[1]);
CopySource source;
source.fd = fds[0];
restorePath(dst, source);
_exit(0);
} catch (exception & e) {
cerr << "error: " << e.what() << endl;
}
_exit(1);
}
close(fds[0]);
/* Parent. */
CopySink sink;
sink.fd = fds[1];
dumpPath(src, sink);
/* Wait for the child to finish. */
int status;
if (waitpid(pid, &status, 0) != pid)
throw SysError("waiting for child");
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
throw Error("cannot copy file: child died");
}
void registerSubstitute(const FSId & srcId, const FSId & subId)
{
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#if 0
Strings subs;
queryListDB(nixDB, dbSubstitutes, srcId, subs); /* non-existence = ok */
for (Strings::iterator it = subs.begin(); it != subs.end(); it++)
if (parseHash(*it) == subId) return;
subs.push_back(subId);
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setListDB(nixDB, dbSubstitutes, srcId, subs);
#endif
/* For now, accept only one substitute per id. */
Strings subs;
subs.push_back(subId);
Transaction txn(nixDB);
nixDB.setStrings(txn, dbSubstitutes, srcId, subs);
txn.commit();
}
void registerPath(const Transaction & txn,
const string & _path, const FSId & id)
{
string path(canonPath(_path));
debug(format("registering path `%1%' with id %2%")
% path % (string) id);
string oldId;
if (nixDB.queryString(txn, dbPath2Id, path, oldId)) {
if (id != parseHash(oldId))
throw Error(format("path `%1%' already contains id %2%")
% path % oldId);
return;
}
nixDB.setString(txn, dbPath2Id, path, id);
Strings paths;
nixDB.queryStrings(txn, dbId2Paths, id, paths); /* non-existence = ok */
paths.push_back(path);
nixDB.setStrings(txn, dbId2Paths, id, paths);
}
void unregisterPath(const string & _path)
{
string path(canonPath(_path));
Transaction txn(nixDB);
debug(format("unregistering path `%1%'") % path);
string _id;
if (!nixDB.queryString(txn, dbPath2Id, path, _id)) {
txn.abort();
return;
}
FSId id(parseHash(_id));
nixDB.delPair(txn, dbPath2Id, path);
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Strings paths, paths2;
nixDB.queryStrings(txn, dbId2Paths, id, paths); /* non-existence = ok */
for (Strings::iterator it = paths.begin();
it != paths.end(); it++)
if (*it != path) paths2.push_back(*it);
nixDB.setStrings(txn, dbId2Paths, id, paths2);
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txn.commit();
}
bool queryPathId(const string & path, FSId & id)
{
string s;
if (!nixDB.queryString(noTxn, dbPath2Id, absPath(path), s)) return false;
id = parseHash(s);
return true;
}
bool isInPrefix(const string & path, const string & _prefix)
{
string prefix = canonPath(_prefix + "/");
return string(path, 0, prefix.size()) == prefix;
}
string expandId(const FSId & id, const string & target,
const string & prefix, FSIdSet pending, bool ignoreSubstitutes)
{
Nest nest(lvlDebug, format("expanding %1%") % (string) id);
Strings paths;
if (!target.empty() && !isInPrefix(target, prefix))
abort();
nixDB.queryStrings(noTxn, dbId2Paths, id, paths);
/* Pick one equal to `target'. */
if (!target.empty()) {
for (Strings::iterator i = paths.begin();
i != paths.end(); i++)
{
string path = *i;
if (path == target && pathExists(path))
return path;
}
}
/* Arbitrarily pick the first one that exists and isn't stale. */
for (Strings::iterator it = paths.begin();
it != paths.end(); it++)
{
string path = *it;
if (isInPrefix(path, prefix) && pathExists(path)) {
if (target.empty())
return path;
else {
/* Acquire a lock on the target path. */
Strings lockPaths;
lockPaths.push_back(target);
PathLocks outputLock(lockPaths);
/* Copy. */
copyPath(path, target);
/* Register the target path. */
Transaction txn(nixDB);
registerPath(txn, target, id);
txn.commit();
return target;
}
}
}
if (!ignoreSubstitutes) {
if (pending.find(id) != pending.end())
throw Error(format("id %1% already being expanded") % (string) id);
pending.insert(id);
/* Try to realise the substitutes, but only if this id is not
already being realised by a substitute. */
Strings subs;
nixDB.queryStrings(noTxn, dbSubstitutes, id, subs); /* non-existence = ok */
for (Strings::iterator it = subs.begin(); it != subs.end(); it++) {
FSId subId = parseHash(*it);
debug(format("trying substitute %1%") % (string) subId);
realiseSlice(normaliseFState(subId, pending), pending);
return expandId(id, target, prefix, pending);
}
}
throw Error(format("cannot expand id `%1%'") % (string) id);
}
void addToStore(string srcPath, string & dstPath, FSId & id,
bool deterministicName)
{
debug(format("adding `%1%' to the store") % srcPath);
srcPath = absPath(srcPath);
id = hashPath(srcPath);
string baseName = baseNameOf(srcPath);
dstPath = canonPath(nixStore + "/" + (string) id + "-" + baseName);
try {
dstPath = expandId(id, deterministicName ? dstPath : "",
nixStore, FSIdSet(), true);
return;
} catch (...) {
}
Strings lockPaths;
lockPaths.push_back(dstPath);
PathLocks outputLock(lockPaths);
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copyPath(srcPath, dstPath);
Transaction txn(nixDB);
registerPath(txn, dstPath, id);
txn.commit();
}
void deleteFromStore(const string & path)
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{
string prefix = + "/";
if (!isInPrefix(path, nixStore))
throw Error(format("path %1% is not in the store") % path);
unregisterPath(path);
deletePath(path);
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}
void verifyStore()
{
Transaction txn(nixDB);
/* !!! verify that the result is consistent */
Strings paths;
nixDB.enumTable(txn, dbPath2Id, paths);
for (Strings::iterator i = paths.begin();
i != paths.end(); i++)
{
bool erase = true;
string path = *i;
if (!pathExists(path)) {
debug(format("path `%1%' disappeared") % path);
}
else {
string id;
if (!nixDB.queryString(txn, dbPath2Id, path, id)) abort();
Strings idPaths;
nixDB.queryStrings(txn, dbId2Paths, id, idPaths);
bool found = false;
for (Strings::iterator j = idPaths.begin();
j != idPaths.end(); j++)
if (path == *j) {
found = true;
break;
}
if (found)
erase = false;
else
/* !!! perhaps we should add path to idPaths? */
debug(format("reverse mapping for path `%1%' missing") % path);
}
if (erase) nixDB.delPair(txn, dbPath2Id, path);
}
Strings ids;
nixDB.enumTable(txn, dbId2Paths, ids);
for (Strings::iterator i = ids.begin();
i != ids.end(); i++)
{
FSId id = parseHash(*i);
Strings idPaths;
nixDB.queryStrings(txn, dbId2Paths, id, idPaths);
for (Strings::iterator j = idPaths.begin();
j != idPaths.end(); )
{
string id2;
if (!nixDB.queryString(txn, dbPath2Id, *j, id2) ||
id != parseHash(id2)) {
debug(format("erasing path `%1%' from mapping for id %2%")
% *j % (string) id);
j = idPaths.erase(j);
} else j++;
}
nixDB.setStrings(txn, dbId2Paths, id, idPaths);
}
Strings subs;
nixDB.enumTable(txn, dbSubstitutes, subs);
for (Strings::iterator i = subs.begin();
i != subs.end(); i++)
{
FSId srcId = parseHash(*i);
Strings subIds;
nixDB.queryStrings(txn, dbSubstitutes, srcId, subIds);
for (Strings::iterator j = subIds.begin();
j != subIds.end(); )
{
FSId subId = parseHash(*j);
Strings subPaths;
nixDB.queryStrings(txn, dbId2Paths, subId, subPaths);
if (subPaths.size() == 0) {
debug(format("erasing substitute %1% for %2%")
% (string) subId % (string) srcId);
j = subIds.erase(j);
} else j++;
}
nixDB.setStrings(txn, dbSubstitutes, srcId, subIds);
}
Strings sucs;
nixDB.enumTable(txn, dbSuccessors, sucs);
for (Strings::iterator i = sucs.begin();
i != sucs.end(); i++)
{
FSId id1 = parseHash(*i);
string id2;
if (!nixDB.queryString(txn, dbSuccessors, id1, id2)) abort();
Strings id2Paths;
nixDB.queryStrings(txn, dbId2Paths, id2, id2Paths);
if (id2Paths.size() == 0) {
Strings id2Subs;
nixDB.queryStrings(txn, dbSubstitutes, id2, id2Subs);
if (id2Subs.size() == 0) {
debug(format("successor %1% for %2% missing")
% id2 % (string) id1);
nixDB.delPair(txn, dbSuccessors, (string) id1);
}
}
}
txn.commit();
}