/* Numail Kit - general header for using the kit ** ** Copyright 2001 Dr. Zoidberg Enterprises. All rights reserved. */ #include <MailPrivate.h> #include <stdio.h> #include <Autolock.h> #include <Directory.h> #include <Entry.h> #include <File.h> #include <FindDirectory.h> #include <Locker.h> #include <Messenger.h> #include <Path.h> #include <String.h> #define timeout 5e5 namespace BPrivate { BPath default_mail_directory() { BPath path; if (find_directory(B_USER_DIRECTORY, &path) == B_OK) path.Append("mail"); else path.SetTo("/boot/home/mail/"); return path; } BPath default_mail_in_directory() { BPath path = default_mail_directory(); path.Append("in"); return path; } BPath default_mail_out_directory() { BPath path = default_mail_directory(); path.Append("out"); return path; } status_t WriteMessageFile(const BMessage& archive, const BPath& path, const char* name) { status_t ret = B_OK; BString leaf = name; leaf << ".tmp"; BEntry settings_entry; BFile tmpfile; bigtime_t now = system_time(); create_directory(path.Path(), 0777); { BDirectory account_dir(path.Path()); ret = account_dir.InitCheck(); if (ret != B_OK) { fprintf(stderr, "Couldn't open '%s': %s\n", path.Path(), strerror(ret)); return ret; } // get an entry for the tempfile // Get it here so that failure doesn't create any problems ret = settings_entry.SetTo(&account_dir,leaf.String()); if (ret != B_OK) { fprintf(stderr, "Couldn't create an entry for '%s/%s': %s\n", path.Path(), leaf.String(), strerror(ret)); return ret; } } // // Save to a temporary file // // Our goal is to write to a tempfile and then use 'rename' to // link that file into place once it contains valid contents. // Given the filesystem's guarantee of atomic "rename" oper- // ations this will guarantee that any non-temp files in the // config directory are valid configuration files. // // Ideally, we would be able to do the following: // BFile tmpfile(&account_dir, "tmpfile", B_WRITE_ONLY|B_CREATE_FILE); // // ... // tmpfile.Relink(&account_dir,"realfile"); // But this doesn't work because there is no way in the API // to link based on file descriptor. (There should be, for // exactly this reason, and I see no reason that it can not // be added to the API, but as it is not present now so we'll // have to deal.) It has to be file-descriptor based because // (a) all a BFile knows is its node/FD and (b) the file may // be unlinked at any time, at which point renaming the entry // to clobber the "realfile" will result in an invalid con- // figuration file being created. // // We can't count on not clobbering the tempfile to gain // exclusivity because, if the system crashes between when // we create the tempfile an when we rename it, we will have // a zombie tempfile that will prevent us from doing any more // saves. // // What we can do is: // // Create or open the tempfile // // At this point no one will *clobber* the file, but // // others may open it // Lock the tempfile // // At this point, no one else may open it and we have // // exclusive access to it. Because of the above, we // // know that our entry is still valid // // Truncate the tempfile // Write settings // Sync // Rename to the realfile // // this does not affect the lock, but now open- // // ing the realfile will fail with B_BUSY // Unlock // // If this code is the only code that changes these files, // then we are guaranteed that all realfiles will be valid // settings files. I think that's the best we can do unless // we get the Relink() api. An implementation of the above // follows. // // Create or open ret = B_TIMED_OUT; while (system_time() - now < timeout) //-ATT-no timeout arg. Setting by #define { ret = tmpfile.SetTo(&settings_entry, B_WRITE_ONLY | B_CREATE_FILE); if (ret != B_BUSY) break; // wait 1/100th second snooze((bigtime_t)1e4); } if (ret != B_OK) { fprintf(stderr, "Couldn't open '%s/%s' within the timeout period (%fs): %s\n", path.Path(), leaf.String(), (float)timeout/1e6, strerror(ret)); return ret==B_BUSY? B_TIMED_OUT:ret; } // lock ret = B_TIMED_OUT; while (system_time() - now < timeout) { ret = tmpfile.Lock(); //-ATT-changed account_file to tmpfile. Is that allowed? if (ret != B_BUSY) break; // wait 1/100th second snooze((bigtime_t)1e4); } if (ret != B_OK) { fprintf(stderr, "Couldn't lock '%s/%s' in within the timeout period (%fs): %s\n", path.Path(), leaf.String(), (float)timeout/1e6, strerror(ret)); // Can't remove it here, since it might be someone else's. // Leaving a zombie shouldn't cause any problems tho so // that's OK. return ret==B_BUSY? B_TIMED_OUT:ret; } // truncate tmpfile.SetSize(0); // write ret = archive.Flatten(&tmpfile); if (ret != B_OK) { fprintf(stderr, "Couldn't flatten settings to '%s/%s': %s\n", path.Path(), leaf.String(), strerror(ret)); return ret; } // ensure it's actually writen ret = tmpfile.Sync(); if (ret != B_OK) { fprintf(stderr, "Couldn't sync settings to '%s/%s': %s\n", path.Path(), leaf.String(), strerror(ret)); return ret; } // clobber old settings ret = settings_entry.Rename(name,true); if (ret != B_OK) { fprintf(stderr, "Couldn't clobber old settings '%s/%s': %s\n", path.Path(), name, strerror(ret)); return ret; } return B_OK; } } // namespace BPrivate
