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#include "lock.hpp"
#include <unistd.h>
#include <cstdio>
#include "cxxstdio.hpp"
#include "socket.hpp"
#include "../poison.hpp"
/// number of backups to keep
static
const int backup_count = 10;
/// Protected file writing
/// (Until the file is closed, it keeps the old file)
// Start writing a tmpfile
FILE *lock_fopen(const char *filename, int *info)
{
FILE *fp;
int no = getpid();
// Get a filename that doesn't already exist
std::string newfile;
do
{
newfile = STRPRINTF("%s_%d.tmp", filename, no++);
fp = fopen_(newfile.c_str(), "wx");
}
while (!fp);
*info = --no;
return fp;
}
// Delete the old file and rename the new file
void lock_fclose(FILE *fp, const char *filename, int *info)
{
if (fp)
{
fclose_(fp);
int n = backup_count;
std::string old_filename = STRPRINTF("%s.%d", filename, n);
while (--n)
{
std::string newer_filename = STRPRINTF("%s.%d", filename, n);
rename(newer_filename.c_str(), old_filename.c_str());
old_filename = std::move(newer_filename);
}
rename(filename, old_filename.c_str());
std::string tmpfile = STRPRINTF("%s_%d.tmp", filename, *info);
rename(tmpfile.c_str(), filename);
}
}
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