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#include "profiles.hh"
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
static bool cmpGensByNumber(const Generation & a, const Generation & b)
{
return a.number < b.number;
}
/* Parse a generation name of the format
`<profilename>-<number>-link'. */
static int parseName(const string & profileName, const string & name)
{
if (string(name, 0, profileName.size() + 1) != profileName + "-") return -1;
string s = string(name, profileName.size() + 1);
unsigned int p = s.find("-link");
if (p == string::npos) return -1;
int n;
if (string2Int(string(s, 0, p), n) && n >= 0)
return n;
else
return -1;
}
Generations findGenerations(Path profile, int & curGen)
{
Generations gens;
Path profileDir = dirOf(profile);
string profileName = baseNameOf(profile);
Strings names = readDirectory(profileDir);
for (Strings::iterator i = names.begin(); i != names.end(); ++i) {
int n;
if ((n = parseName(profileName, *i)) != -1) {
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);
curGen = pathExists(profile)
? parseName(profileName, readLink(profile))
: -1;
return gens;
}
static void makeNames(const Path & profile, unsigned int num,
Path & outLink, Path & drvLink)
{
Path prefix = (format("%1%-%2%") % profile % num).str();
outLink = prefix + "-output";
drvLink = prefix + "-drv";
}
Path createGeneration(Path profile, Path outPath, Path drvPath)
{
/* The new generation number should be higher than old the
previous ones. */
int dummy;
Generations gens = findGenerations(profile, dummy);
unsigned int num = gens.size() > 0 ? gens.front().number : 0;
/* Create the new generation. */
Path outLink, drvLink;
while (1) {
makeNames(profile, num, outLink, drvLink);
if (symlink(outPath.c_str(), outLink.c_str()) == 0) break;
if (errno != EEXIST)
throw SysError(format("creating symlink `%1%'") % outLink);
/* Somebody beat us to it, retry with a higher number. */
num++;
}
if (symlink(drvPath.c_str(), drvLink.c_str()) != 0)
throw SysError(format("creating symlink `%1%'") % drvLink);
return outLink;
}
static void removeFile(const Path & path)
{
if (remove(path.c_str()) == -1)
throw SysError(format("cannot unlink `%1%'") % path);
}
void deleteGeneration(const Path & profile, unsigned int gen)
{
Path generation, gcrootDrv;
makeNames(profile, gen, generation, gcrootDrv);
removeFile(generation);
if (pathExists(gcrootDrv)) removeFile(gcrootDrv);
}
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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