/* Try to skip over a specified number of bytes. */
public void skipData(int amountToSkip)
throws ChecksumException, EOFException, FileNotFoundException, DatabaseException {
try {
readData(amountToSkip, false);
} catch (DatabaseException e) {
reportProblem(e);
throw e;
}
}
/**
* Variant of readNextEntry that throws FileNotFoundException and ChecksumException, rather than
* wrapping them in an EnvironmentFailureException and invalidating the enviornment. This allows
* users of this class (see cleaner.FileProcessor), and subclasses that override readNextEntry
* (see ScavengerFileReader and LastFileReader), to handle these exceptions specially.
*/
public final boolean readNextEntryAllowExceptions()
throws FileNotFoundException, ChecksumException {
boolean foundEntry = false;
long savedCurrentEntryOffset = currentEntryOffset;
long savedNextEntryOffset = nextEntryOffset;
try {
while ((!eof) && (!foundEntry)) {
/* Read the invariant portion of the next header. */
getLogEntryInReadBuffer();
ByteBuffer dataBuffer = readData(LogEntryHeader.MIN_HEADER_SIZE, true); // collectData
readBasicHeader(dataBuffer);
boolean isTarget;
boolean isChecksumTarget;
boolean collectData;
if (currentEntryHeader.isVariableLength()) {
/*
* For all variable length entries, init the checksum w/the
* invariant portion of the header, before we know whether
* the entry is a target for this reader. This has
* to be done before we read the variable portion of the
* header, because readData() only guarantees that it
* returns a dataBuffer that contains the next bytes that
* are needed, and has no guarantee that it holds any bytes
* that were previously read. The act of calling
* readData() to obtain the optional portion may reset the
* dataBuffer, and nudge the invariant part of the header
* out of the buffer returned by readData()
*/
startChecksum(dataBuffer);
int optionalPortionLen = currentEntryHeader.getVariablePortionSize();
/* Load the optional part of the header into a buffer. */
dataBuffer = readData(optionalPortionLen, true);
/*
* Add to checksum while the buffer is positioned at
* the start of the new bytes.
*/
addToChecksum(dataBuffer, optionalPortionLen);
/* Now read the optional bytes. */
currentEntryHeader.readVariablePortion(dataBuffer);
}
/*
* We've read the header of the next logrec. Move up our
* offsets if we're moving forward. If we're moving
* backwards, we set our offset before we read the header,
* because we knew where the entry started.
*/
if (forward) {
currentEntryOffset = nextEntryOffset;
nextEntryOffset +=
currentEntryHeader.getSize()
+ // header size
currentEntryHeader.getItemSize(); // item size
}
try {
isTarget = isTargetEntry();
isChecksumTarget = (isTarget || alwaysValidateChecksum);
if (!currentEntryHeader.isVariableLength()) {
startChecksum(dataBuffer, isChecksumTarget);
}
collectData = (isChecksumTarget && doChecksumOnRead) || isTarget;
/*
* Read in the body of the next entry. Note that even if
* this isn't a targeted entry, we have to move the buffer
* position along.
*/
dataBuffer = readData(currentEntryHeader.getItemSize(), collectData);
} catch (Throwable e) {
if (forward) {
currentEntryOffset = savedCurrentEntryOffset;
nextEntryOffset = savedNextEntryOffset;
}
throw e;
}
/* Validate the log entry checksum. */
validateChecksum(dataBuffer, isChecksumTarget);
if (isTarget) {
/*
* For a target entry, call the subclass reader's
* processEntry method to do whatever we need with the
* entry. It returns true if this entry is one that should
* be returned. Note that some entries, although targeted
* and read, are not returned.
*/
if (processEntry(dataBuffer)) {
foundEntry = true;
nRead++;
}
} else if (collectData) {
/*
* For a non-target entry that was validated, the buffer is
* positioned at the start of the entry; skip over it.
*/
skipEntry(dataBuffer);
}
}
} catch (EOFException e) {
eof = true;
} catch (DatabaseException e) {
eof = true;
/* Report on error. */
reportProblem(e);
throw e;
}
return foundEntry;
}