475 lines
12 KiB
C++
475 lines
12 KiB
C++
#include <iostream>
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#include <sys/wait.h>
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#include <unistd.h>
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#include "store.hh"
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#include "globals.hh"
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#include "db.hh"
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#include "archive.hh"
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#include "pathlocks.hh"
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/* Nix database. */
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static Database nixDB;
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/* Database tables. */
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/* dbValidPaths :: Path -> ()
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The existence of a key $p$ indicates that path $p$ is valid (that
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is, produced by a succesful build). */
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static TableId dbValidPaths;
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/* dbSuccessors :: Path -> Path
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Each pair $(p_1, p_2)$ in this mapping records the fact that the
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Nix expression stored at path $p_1$ has a successor expression
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stored at path $p_2$.
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Note that a term $y$ is a successor of $x$ iff there exists a
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sequence of rewrite steps that rewrites $x$ into $y$.
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*/
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static TableId dbSuccessors;
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/* dbSuccessorsRev :: Path -> [Path]
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The reverse mapping of dbSuccessors (i.e., it stores the
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predecessors of a Nix expression).
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*/
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static TableId dbSuccessorsRev;
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/* dbSubstitutes :: Path -> [Path]
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Each pair $(p, [ps])$ tells Nix that it can realise any of the
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Nix expressions stored at paths $ps$ to produce a path $p$.
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The main purpose of this is for distributed caching of derivates.
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One system can compute a derivate and put it on a website (as a Nix
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archive), for instance, and then another system can register a
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substitute for that derivate. The substitute in this case might be
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a Nix expression that fetches the Nix archive.
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*/
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static TableId dbSubstitutes;
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/* dbSubstitutesRev :: Path -> [Path]
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The reverse mapping of dbSubstitutes.
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*/
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static TableId dbSubstitutesRev;
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void openDB()
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{
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nixDB.open(nixDBPath);
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dbValidPaths = nixDB.openTable("validpaths");
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dbSuccessors = nixDB.openTable("successors");
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dbSuccessorsRev = nixDB.openTable("successors-rev");
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dbSubstitutes = nixDB.openTable("substitutes");
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dbSubstitutesRev = nixDB.openTable("substitutes-rev");
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}
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void initDB()
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{
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}
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void createStoreTransaction(Transaction & txn)
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{
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Transaction txn2(nixDB);
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txn2.moveTo(txn);
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}
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/* Path copying. */
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struct CopySink : DumpSink
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{
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int fd;
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virtual void operator () (const unsigned char * data, unsigned int len)
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{
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writeFull(fd, data, len);
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}
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};
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struct CopySource : RestoreSource
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{
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int fd;
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virtual void operator () (unsigned char * data, unsigned int len)
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{
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readFull(fd, data, len);
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}
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};
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void copyPath(const Path & src, const Path & dst)
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{
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debug(format("copying `%1%' to `%2%'") % src % dst);
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/* Unfortunately C++ doesn't support coprocedures, so we have no
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nice way to chain CopySink and CopySource together. Instead we
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fork off a child to run the sink. (Fork-less platforms should
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use a thread). */
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/* Create a pipe. */
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int fds[2];
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if (pipe(fds) == -1) throw SysError("creating pipe");
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/* Fork. */
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pid_t pid;
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switch (pid = fork()) {
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case -1:
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throw SysError("unable to fork");
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case 0: /* child */
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try {
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close(fds[1]);
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CopySource source;
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source.fd = fds[0];
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restorePath(dst, source);
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_exit(0);
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} catch (exception & e) {
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cerr << "error: " << e.what() << endl;
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}
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_exit(1);
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}
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close(fds[0]);
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/* Parent. */
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CopySink sink;
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sink.fd = fds[1];
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dumpPath(src, sink);
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/* Wait for the child to finish. */
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int status;
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if (waitpid(pid, &status, 0) != pid)
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throw SysError("waiting for child");
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if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
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throw Error("cannot copy file: child died");
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}
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static bool isValidPathTxn(const Path & path, const Transaction & txn)
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{
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string s;
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return nixDB.queryString(txn, dbValidPaths, path, s);
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}
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bool isValidPath(const Path & path)
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{
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return isValidPathTxn(path, noTxn);
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}
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static bool isUsablePathTxn(const Path & path, const Transaction & txn)
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{
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if (isValidPathTxn(path, txn)) return true;
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Paths subs;
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nixDB.queryStrings(txn, dbSubstitutes, path, subs);
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return subs.size() > 0;
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}
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void registerSuccessor(const Transaction & txn,
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const Path & srcPath, const Path & sucPath)
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{
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if (!isUsablePathTxn(sucPath, txn)) throw Error(
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format("path `%1%' cannot be a successor, since it is not usable")
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% sucPath);
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Path known;
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if (nixDB.queryString(txn, dbSuccessors, srcPath, known) &&
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known != sucPath)
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{
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throw Error(format(
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"the `impossible' happened: expression in path "
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"`%1%' appears to have multiple successors "
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"(known `%2%', new `%3%'")
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% srcPath % known % sucPath);
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}
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
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if (find(revs.begin(), revs.end(), srcPath) == revs.end())
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revs.push_back(srcPath);
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nixDB.setString(txn, dbSuccessors, srcPath, sucPath);
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nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
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}
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bool querySuccessor(const Path & srcPath, Path & sucPath)
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{
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return nixDB.queryString(noTxn, dbSuccessors, srcPath, sucPath);
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}
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Paths queryPredecessors(const Path & sucPath)
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{
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Paths revs;
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nixDB.queryStrings(noTxn, dbSuccessorsRev, sucPath, revs);
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return revs;
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}
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void registerSubstitute(const Path & srcPath, const Path & subPath)
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{
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if (!isValidPathTxn(subPath, noTxn)) throw Error(
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format("path `%1%' cannot be a substitute, since it is not valid")
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% subPath);
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Transaction txn(nixDB);
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Paths subs;
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nixDB.queryStrings(txn, dbSubstitutes, srcPath, subs);
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if (find(subs.begin(), subs.end(), subPath) != subs.end()) {
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/* Nothing to do if the substitute is already known. */
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txn.abort();
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return;
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}
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subs.push_front(subPath); /* new substitutes take precedence */
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Paths revs;
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nixDB.queryStrings(txn, dbSubstitutesRev, subPath, revs);
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if (find(revs.begin(), revs.end(), srcPath) == revs.end())
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revs.push_back(srcPath);
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nixDB.setStrings(txn, dbSubstitutes, srcPath, subs);
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nixDB.setStrings(txn, dbSubstitutesRev, subPath, revs);
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txn.commit();
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}
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Paths querySubstitutes(const Path & srcPath)
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{
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Paths subPaths;
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nixDB.queryStrings(noTxn, dbSubstitutes, srcPath, subPaths);
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return subPaths;
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}
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void registerValidPath(const Transaction & txn, const Path & _path)
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{
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Path path(canonPath(_path));
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debug(format("registering path `%1%'") % path);
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nixDB.setString(txn, dbValidPaths, path, "");
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}
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static void setOrClearStrings(Transaction & txn,
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TableId table, const string & key, const Strings & value)
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{
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if (value.size() > 0)
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nixDB.setStrings(txn, table, key, value);
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else
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nixDB.delPair(txn, table, key);
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}
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static void invalidatePath(const Path & path, Transaction & txn)
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{
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debug(format("unregistering path `%1%'") % path);
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nixDB.delPair(txn, dbValidPaths, path);
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/* Remove any successor mappings to this path (but not *from*
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it). */
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, path, revs);
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for (Paths::iterator i = revs.begin(); i != revs.end(); ++i)
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nixDB.delPair(txn, dbSuccessors, *i);
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nixDB.delPair(txn, dbSuccessorsRev, path);
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/* Remove any substitute mappings to this path. */
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revs.clear();
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nixDB.queryStrings(txn, dbSubstitutesRev, path, revs);
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for (Paths::iterator i = revs.begin(); i != revs.end(); ++i) {
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Paths subs;
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nixDB.queryStrings(txn, dbSubstitutes, *i, subs);
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if (find(subs.begin(), subs.end(), path) == subs.end())
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throw Error("integrity error in substitutes mapping");
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subs.remove(path);
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setOrClearStrings(txn, dbSubstitutes, *i, subs);
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/* If path *i now has no substitutes left, and is not valid,
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then it too should be invalidated. This is because it may
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be a substitute or successor. */
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if (subs.size() == 0 && !isValidPathTxn(*i, txn))
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invalidatePath(*i, txn);
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}
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nixDB.delPair(txn, dbSubstitutesRev, path);
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}
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static bool isInPrefix(const string & path, const string & _prefix)
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{
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string prefix = canonPath(_prefix + "/");
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return string(path, 0, prefix.size()) == prefix;
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}
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Path addToStore(const Path & _srcPath)
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{
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Path srcPath(absPath(_srcPath));
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debug(format("adding `%1%' to the store") % srcPath);
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Hash h = hashPath(srcPath);
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string baseName = baseNameOf(srcPath);
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Path dstPath = canonPath(nixStore + "/" + (string) h + "-" + baseName);
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if (!isValidPath(dstPath)) {
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/* The first check above is an optimisation to prevent
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unnecessary lock acquisition. */
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PathSet lockPaths;
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lockPaths.insert(dstPath);
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PathLocks outputLock(lockPaths);
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if (!isValidPath(dstPath)) {
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copyPath(srcPath, dstPath);
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Transaction txn(nixDB);
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registerValidPath(txn, dstPath);
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txn.commit();
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}
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outputLock.setDeletion(true);
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}
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return dstPath;
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}
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void addTextToStore(const Path & dstPath, const string & s)
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{
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if (!isValidPath(dstPath)) {
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PathSet lockPaths;
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lockPaths.insert(dstPath);
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PathLocks outputLock(lockPaths);
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if (!isValidPath(dstPath)) {
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writeStringToFile(dstPath, s);
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Transaction txn(nixDB);
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registerValidPath(txn, dstPath);
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txn.commit();
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}
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outputLock.setDeletion(true);
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}
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}
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void deleteFromStore(const Path & _path)
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{
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Path path(canonPath(_path));
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if (!isInPrefix(path, nixStore))
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throw Error(format("path `%1%' is not in the store") % path);
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Transaction txn(nixDB);
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invalidatePath(path, txn);
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txn.commit();
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deletePath(path);
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}
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void verifyStore()
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{
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Transaction txn(nixDB);
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Paths paths;
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PathSet validPaths;
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nixDB.enumTable(txn, dbValidPaths, paths);
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for (Paths::iterator i = paths.begin(); i != paths.end(); ++i) {
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Path path = *i;
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if (!pathExists(path)) {
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debug(format("path `%1%' disappeared") % path);
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invalidatePath(path, txn);
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} else
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validPaths.insert(path);
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}
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/* !!! the code below does not allow transitive substitutes.
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I.e., if B is a substitute of A, then B must be a valid path.
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B cannot itself be invalid but have a substitute. */
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/* "Usable" paths are those that are valid or have a substitute.
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These are the paths that are allowed to appear in the
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right-hand side of a sute mapping. */
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PathSet usablePaths(validPaths);
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/* Check that the values of the substitute mappings are valid
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paths. */
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Paths subs;
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nixDB.enumTable(txn, dbSubstitutes, subs);
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for (Paths::iterator i = subs.begin(); i != subs.end(); ++i) {
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Paths subPaths, subPaths2;
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nixDB.queryStrings(txn, dbSubstitutes, *i, subPaths);
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for (Paths::iterator j = subPaths.begin(); j != subPaths.end(); ++j)
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if (validPaths.find(*j) == validPaths.end())
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debug(format("found substitute mapping to non-existent path `%1%'") % *j);
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else
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subPaths2.push_back(*j);
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if (subPaths.size() != subPaths2.size())
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setOrClearStrings(txn, dbSubstitutes, *i, subPaths2);
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if (subPaths2.size() > 0)
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usablePaths.insert(*i);
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}
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/* Check that the keys of the reverse substitute mappings are
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valid paths. */
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Paths rsubs;
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nixDB.enumTable(txn, dbSubstitutesRev, rsubs);
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for (Paths::iterator i = rsubs.begin(); i != rsubs.end(); ++i) {
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if (validPaths.find(*i) == validPaths.end()) {
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debug(format("found reverse substitute mapping for non-existent path `%1%'") % *i);
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nixDB.delPair(txn, dbSubstitutesRev, *i);
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}
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}
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/* Check that the values of the successor mappings are usable
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paths. */
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Paths sucs;
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nixDB.enumTable(txn, dbSuccessors, sucs);
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for (Paths::iterator i = sucs.begin(); i != sucs.end(); ++i) {
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/* Note that *i itself does not have to be valid, just its
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successor. */
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Path sucPath;
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if (nixDB.queryString(txn, dbSuccessors, *i, sucPath) &&
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usablePaths.find(sucPath) == usablePaths.end())
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{
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debug(format("found successor mapping to non-existent path `%1%'") % sucPath);
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nixDB.delPair(txn, dbSuccessors, *i);
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}
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}
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/* Check that the keys of the reverse successor mappings are valid
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paths. */
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Paths rsucs;
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nixDB.enumTable(txn, dbSuccessorsRev, rsucs);
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for (Paths::iterator i = rsucs.begin(); i != rsucs.end(); ++i) {
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if (usablePaths.find(*i) == usablePaths.end()) {
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debug(format("found reverse successor mapping for non-existent path `%1%'") % *i);
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nixDB.delPair(txn, dbSuccessorsRev, *i);
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}
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}
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txn.commit();
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}
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