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#include "profiles.hh"
Path createGeneration(Path profile, Path outPath, Path drvPath)
{
Path profileDir = dirOf(profile);
string profileName = baseNameOf(profile);
unsigned int num = 0;
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() && n >= num) num = n + 1;
}
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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