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#include "profiles.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
static bool cmpGensByNumber(const Generation & a, const Generation & b)
{
return a.number < b.number;
}
Generations findGenerations(Path profile)
{
Generations gens;
Path profileDir = dirOf(profile);
string profileName = baseNameOf(profile);
Strings names = readDirectory(profileDir);
for (Strings::iterator i = names.begin(); i != names.end(); ++i) {
if (string(*i, 0, profileName.size() + 1) != profileName + "-") continue;
string s = string(*i, profileName.size() + 1);
int p = s.find("-link");
if (p == string::npos) continue;
istringstream str(string(s, 0, p));
unsigned int n;
if (str >> n && str.eof()) {
Generation gen;
gen.path = profileDir + "/" + *i;
gen.number = n;
struct stat st;
if (lstat(gen.path.c_str(), &st) != 0)
throw SysError(format("statting `%1%'") % gen.path);
gen.creationTime = st.st_mtime;
gens.push_back(gen);
}
}
gens.sort(cmpGensByNumber);
return gens;
}
Path createGeneration(Path profile, Path outPath, Path drvPath)
{
/* The new generation number should be higher than old the
previous ones. */
Generations gens = findGenerations(profile);
unsigned int num = gens.size() > 0 ? gens.front().number : 0;
/* Create the new generation. */
Path generation, gcrootSrc;
while (1) {
Path prefix = (format("%1%-%2%") % profile % num).str();
generation = prefix + "-link";
gcrootSrc = prefix + "-src.gcroot";
if (symlink(outPath.c_str(), generation.c_str()) == 0) break;
if (errno != EEXIST)
throw SysError(format("creating symlink `%1%'") % generation);
/* Somebody beat us to it, retry with a higher number. */
num++;
}
writeStringToFile(gcrootSrc, drvPath);
return generation;
}
void switchLink(Path link, Path target)
{
/* Hacky. */
if (dirOf(target) == dirOf(link)) target = baseNameOf(target);
Path tmp = canonPath(dirOf(link) + "/.new_" + baseNameOf(link));
if (symlink(target.c_str(), tmp.c_str()) != 0)
throw SysError(format("creating symlink `%1%'") % tmp);
/* The rename() system call is supposed to be essentially atomic
on Unix. That is, if we have links `current -> X' and
`new_current -> Y', and we rename new_current to current, a
process accessing current will see X or Y, but never a
file-not-found or other error condition. This is sufficient to
atomically switch user environments. */
if (rename(tmp.c_str(), link.c_str()) != 0)
throw SysError(format("renaming `%1%' to `%2%'") % tmp % link);
}
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