Mozilla/mozilla/modules/libpref/src/nsSafeSaveFile.cpp

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 * for the specific language governing rights and limitations under the
 * License.
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 * The Original Code is Mozilla Communicator client code.
 *
 * The Initial Developer of the Original Code is 
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 * Contributor(s):
 * Brian Nesse <bnesse@netscape.com>
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#include "nsSafeSaveFile.h"
#include "prmem.h"

// Definitions
#define BACKUP_FILE_EXTENSION NS_LITERAL_CSTRING(".bak")


nsSafeSaveFile::nsSafeSaveFile(nsIFile *aTargetFile, PRInt32 aNumBackupCopies)
 : mTargetNameLen(0),
   mBackupCount(aNumBackupCopies)
{
    nsCAutoString tempFileName;  
    const char *  temp;
    nsresult      rv;

    // determine the actual filename (less the extension)
    rv = aTargetFile->GetLeafName(mTargetFileName);
    if (NS_FAILED(rv)) // yikes! out of memory
        return;

    temp = strrchr(mTargetFileName.get(), '.');
    if (temp)
       mTargetNameLen = temp - mTargetFileName.get();
    else
       mTargetNameLen = mTargetFileName.Length();

    // create a new file object that points to the temp file
    tempFileName = Substring(mTargetFileName, 0, mTargetNameLen) + NS_LITERAL_CSTRING(".tmp");
    rv = aTargetFile->Clone(getter_AddRefs(mTempFile));
    if (NS_SUCCEEDED(rv))
        mTempFile->SetLeafName(tempFileName);
}

void nsSafeSaveFile::CleanupFailedSave(void)
{
    NS_ASSERTION(mTempFile, "Must create a temp file first!");

    // the save failed, remove the temp file
    mTempFile->Remove(PR_FALSE);
}

nsresult nsSafeSaveFile::GetSaveFile(nsIFile **_retval)
{
    if (mTargetFileName.IsEmpty() || !mTempFile)
        return(NS_ERROR_OUT_OF_MEMORY);

    *_retval = mTempFile;
    NS_ADDREF(*_retval);

    return(NS_OK);
}

nsresult nsSafeSaveFile::PostProcessSave(void)
{
    nsCOMPtr<nsIFile> backupFile;
    nsCAutoString     fileName;
    nsresult          rv;
    PRBool            bExists;

    NS_ASSERTION(mTempFile, "Must create a temp file first!");

    rv = mTempFile->Clone(getter_AddRefs(backupFile));
    if (NS_FAILED(rv)) // yikes! out of memory, probably best to not continue
        return rv;

    if (mBackupCount > 0) {
        // kill the (oldest) backup copy, if necessary
        fileName = Substring(mTargetFileName, 0, mTargetNameLen) + BACKUP_FILE_EXTENSION;
        if (mBackupCount > 1)
            fileName.AppendInt(mBackupCount - 1);
        backupFile->SetLeafName(fileName);
    } else {
        // no backups desired, delete the previous save
        backupFile->SetLeafName(mTargetFileName);
    }

    // remove the file as determined by the logic above
    backupFile->Remove(PR_FALSE);

    // now manage the backup copies
    if (mBackupCount > 0) {
        PRInt32 backupCount = mBackupCount;
        fileName = Substring(mTargetFileName, 0, mTargetNameLen) + BACKUP_FILE_EXTENSION;
        while (--backupCount > 0) {
            // bump all of the redundant backups up one (i.e. bak -> bak1, bak1 -> bak2, etc.)
            if (backupCount > 1)
                fileName.AppendInt(backupCount - 1);
            backupFile->SetLeafName(fileName);
            backupFile->Exists(&bExists);
            if (bExists) {
                fileName.Truncate(mTargetNameLen + (sizeof(BACKUP_FILE_EXTENSION) - 1));
                fileName.AppendInt(backupCount);
                // fail silently because it's not important enough to bail on the save for
                backupFile->MoveTo(0, fileName);
            }
            fileName.Truncate(mTargetNameLen + (sizeof(BACKUP_FILE_EXTENSION) - 1));
        };

        // rename the previous save to .bak (i.e. <filename.js> to <filename.bak>)
        backupFile->SetLeafName(mTargetFileName);
        rv = backupFile->MoveTo(0, fileName);
        if (NS_FAILED(rv))
            return rv;
    }

    // finally rename the temp file to the original name (i.e. <filename.tmp> to <filename.js>)
    rv = mTempFile->MoveTo(0, mTargetFileName);
    return rv;
}

nsresult nsSafeSaveFile::PurgeOldestBackup(void)
{
    nsCOMPtr<nsIFile> backupFile;
    nsCAutoString     fileName;
    nsresult          rv;

    NS_ASSERTION(mTempFile, "Must create a temp file first!");

    rv = mTempFile->Clone(getter_AddRefs(backupFile));
    if (NS_FAILED(rv)) // yikes! out of memory, probably best to not continue
        return rv;

    // can't delete what you're not creating
    if (mBackupCount == 0)
        return NS_ERROR_FILE_NOT_FOUND;

    PRInt32 backupCount = mBackupCount;
    fileName = Substring(mTargetFileName, 0, mTargetNameLen) + BACKUP_FILE_EXTENSION;
    while (--backupCount >= 0) {
        if (backupCount)
            fileName.AppendInt(backupCount);
        backupFile->SetLeafName(fileName);
        rv = backupFile->Remove(PR_FALSE);
        if (NS_SUCCEEDED(rv)) {
            return NS_OK;
        }
        fileName.Truncate(mTargetNameLen + (sizeof(BACKUP_FILE_EXTENSION) - 1));
    };

    return NS_ERROR_FILE_NOT_FOUND;
}