forked from lix-project/lix
d58a11e019
bits, then encode them in a radix-32 representation (using digits and letters except e, o, u, and t). This produces store paths like /nix/store/4i0zb0z7f88mwghjirkz702a71dcfivn-aterm-2.3.1. The nice thing about this is that the hash part of the file name is still 32 characters, as before with MD5. (Of course, shortening SHA-256 to 160 bits makes it no better than SHA-160 in theory, but hopefully it's a bit more resistant to attacks; it's certainly a lot slower.)
596 lines
15 KiB
C++
596 lines
15 KiB
C++
#include <iostream>
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#include <algorithm>
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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 = 0;
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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 = 0;
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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 = 0;
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/* dbSubstitutes :: Path -> [[Path]]
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Each pair $(p, subs)$ tells Nix that it can use any of the
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substitutes in $subs$ to build path $p$. Each substitute defines a
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command-line invocation of a program (i.e., the first list element
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is the full path to the program, the remaining elements are
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arguments).
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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 = 0;
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bool Substitute::operator == (const Substitute & sub)
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{
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return program == sub.program
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&& args == sub.args;
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}
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void openDB()
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{
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if (readOnlyMode) return;
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try {
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nixDB.open(nixDBPath);
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} catch (DbNoPermission & e) {
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printMsg(lvlTalkative, "cannot access Nix database; continuing anyway");
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readOnlyMode = true;
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return;
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}
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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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}
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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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Pipe pipe;
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pipe.create();
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/* Fork. */
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Pid pid;
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pid = fork();
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switch (pid) {
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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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pipe.writeSide.close();
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CopySource source;
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source.fd = pipe.readSide;
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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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/* Parent. */
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pipe.readSide.close();
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CopySink sink;
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sink.fd = pipe.writeSide;
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{
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SwitchToOriginalUser sw;
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dumpPath(src, sink);
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}
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/* Wait for the child to finish. */
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int status = pid.wait(true);
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if (!statusOk(status))
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throw Error(format("cannot copy `%1% to `%2%': child %3%")
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% src % dst % statusToString(status));
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}
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static bool isInStore(const Path & path)
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{
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return path[0] == '/'
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&& path.compare(0, nixStore.size(), nixStore) == 0
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&& path.size() >= nixStore.size() + 2
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&& path[nixStore.size()] == '/'
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&& path.find('/', nixStore.size() + 1) == Path::npos;
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}
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void assertStorePath(const Path & path)
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{
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if (!isInStore(path))
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throw Error(format("path `%1%' is not in the Nix store") % path);
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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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assertStorePath(srcPath);
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assertStorePath(sucPath);
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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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void unregisterSuccessor(const Path & srcPath)
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{
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assertStorePath(srcPath);
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Transaction txn(nixDB);
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Path sucPath;
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if (!nixDB.queryString(txn, dbSuccessors, srcPath, sucPath)) {
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txn.abort();
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return;
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}
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nixDB.delPair(txn, dbSuccessors, srcPath);
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Paths revs;
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nixDB.queryStrings(txn, dbSuccessorsRev, sucPath, revs);
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Paths::iterator i = find(revs.begin(), revs.end(), srcPath);
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assert(i != revs.end());
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revs.erase(i);
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nixDB.setStrings(txn, dbSuccessorsRev, sucPath, revs);
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txn.commit();
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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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static Substitutes readSubstitutes(const Transaction & txn,
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const Path & srcPath)
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{
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Strings ss;
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nixDB.queryStrings(txn, dbSubstitutes, srcPath, ss);
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Substitutes subs;
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for (Strings::iterator i = ss.begin(); i != ss.end(); ++i) {
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if (i->size() < 4 || (*i)[3] != 0) {
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/* Old-style substitute. !!! remove this code
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eventually? */
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break;
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}
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Strings ss2 = unpackStrings(*i);
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if (ss2.size() == 3) {
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/* Another old-style substitute. */
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continue;
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}
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if (ss2.size() != 2) throw Error("malformed substitute");
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Strings::iterator j = ss2.begin();
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Substitute sub;
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sub.program = *j++;
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sub.args = unpackStrings(*j++);
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subs.push_back(sub);
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}
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return subs;
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}
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static void writeSubstitutes(const Transaction & txn,
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const Path & srcPath, const Substitutes & subs)
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{
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Strings ss;
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for (Substitutes::const_iterator i = subs.begin();
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i != subs.end(); ++i)
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{
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Strings ss2;
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ss2.push_back(i->program);
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ss2.push_back(packStrings(i->args));
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ss.push_back(packStrings(ss2));
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}
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nixDB.setStrings(txn, dbSubstitutes, srcPath, ss);
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}
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void registerSubstitutes(const Transaction & txn,
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const SubstitutePairs & subPairs)
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{
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for (SubstitutePairs::const_iterator i = subPairs.begin();
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i != subPairs.end(); ++i)
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{
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const Path & srcPath(i->first);
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const Substitute & sub(i->second);
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assertStorePath(srcPath);
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Substitutes subs = readSubstitutes(txn, srcPath);
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/* New substitutes take precedence over old ones. If the
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substitute is already present, it's moved to the front. */
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remove(subs.begin(), subs.end(), sub);
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subs.push_front(sub);
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writeSubstitutes(txn, srcPath, subs);
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}
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}
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Substitutes querySubstitutes(const Path & srcPath)
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{
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return readSubstitutes(noTxn, srcPath);
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}
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static void unregisterPredecessors(const Path & path, Transaction & txn)
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{
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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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}
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void clearSubstitutes()
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{
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Transaction txn(nixDB);
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/* Iterate over all paths for which there are substitutes. */
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Paths subKeys;
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nixDB.enumTable(txn, dbSubstitutes, subKeys);
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for (Paths::iterator i = subKeys.begin(); i != subKeys.end(); ++i) {
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/* If this path has not become valid in the mean-while, delete
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any successor mappings *to* it. This is to preserve the
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invariant the all successors are `usable' as opposed to
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`valid' (i.e., the successor must be valid *or* have at
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least one substitute). */
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if (!isValidPath(*i)) {
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unregisterPredecessors(*i, txn);
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}
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/* Delete all substitutes for path *i. */
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nixDB.delPair(txn, dbSubstitutes, *i);
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}
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txn.commit();
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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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assertStorePath(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 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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unregisterPredecessors(path, txn);
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}
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Path makeStorePath(const string & type,
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Hash & hash, const string & suffix)
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{
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/* e.g., "source:sha256:1abc...:/nix/store:foo.tar.gz" */
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string s = type + ":sha256:" + printHash(hash) + ":"
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+ nixStore + ":" + suffix;
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return nixStore + "/"
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+ printHash32(compressHash(hashString(s, htSHA256), 20))
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+ "-" + suffix;
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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(htSHA256);
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{
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SwitchToOriginalUser sw;
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h = hashPath(srcPath, htSHA256);
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}
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string baseName = baseNameOf(srcPath);
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Path dstPath = makeStorePath("source", h, baseName);
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if (!readOnlyMode && !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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if (pathExists(dstPath)) deletePath(dstPath);
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/* !!! race: srcPath might change between hashPath() and
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here! */
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copyPath(srcPath, dstPath);
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Hash h2 = hashPath(dstPath, htSHA256);
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if (h != h2)
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throw Error(format("contents of `%1%' changed while copying it to `%2%' (%3% -> %4%)")
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% srcPath % dstPath % printHash(h) % printHash(h2));
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makePathReadOnly(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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Path addTextToStore(const string & suffix, const string & s)
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{
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Hash hash = hashString(s, htSHA256);
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Path dstPath = makeStorePath("text", hash, suffix);
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if (!readOnlyMode && !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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if (pathExists(dstPath)) deletePath(dstPath);
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writeStringToFile(dstPath, s);
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makePathReadOnly(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 deleteFromStore(const Path & _path)
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{
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Path path(canonPath(_path));
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assertStorePath(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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printMsg(lvlError, format("path `%1%' disappeared") % path);
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invalidatePath(path, txn);
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} else if (!isInStore(path)) {
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printMsg(lvlError, format("path `%1%' is not in the Nix store") % 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 subKeys;
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nixDB.enumTable(txn, dbSubstitutes, subKeys);
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for (Paths::iterator i = subKeys.begin(); i != subKeys.end(); ++i) {
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Substitutes subs = readSubstitutes(txn, *i);
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if (subs.size() > 0)
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usablePaths.insert(*i);
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else
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nixDB.delPair(txn, dbSubstitutes, *i);
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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 sucKeys;
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nixDB.enumTable(txn, dbSuccessors, sucKeys);
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for (Paths::iterator i = sucKeys.begin(); i != sucKeys.end(); ++i) {
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/* Note that *i itself does not have to be valid, just its
|
|
successor. */
|
|
Path sucPath;
|
|
if (nixDB.queryString(txn, dbSuccessors, *i, sucPath) &&
|
|
usablePaths.find(sucPath) == usablePaths.end())
|
|
{
|
|
printMsg(lvlError,
|
|
format("found successor mapping to non-existent path `%1%'") % sucPath);
|
|
nixDB.delPair(txn, dbSuccessors, *i);
|
|
}
|
|
}
|
|
|
|
/* Check that the keys of the reverse successor mappings are valid
|
|
paths. */
|
|
Paths rsucKeys;
|
|
nixDB.enumTable(txn, dbSuccessorsRev, rsucKeys);
|
|
for (Paths::iterator i = rsucKeys.begin(); i != rsucKeys.end(); ++i) {
|
|
if (usablePaths.find(*i) == usablePaths.end()) {
|
|
printMsg(lvlError,
|
|
format("found reverse successor mapping for non-existent path `%1%'") % *i);
|
|
nixDB.delPair(txn, dbSuccessorsRev, *i);
|
|
}
|
|
}
|
|
|
|
txn.commit();
|
|
}
|