232 lines
7.3 KiB
C++
232 lines
7.3 KiB
C++
#include "./oggiterator.h"
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#include "../exceptions.h"
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#include <iostream>
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using namespace std;
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namespace Media {
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/*!
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* \class Media::OggIterator
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* \brief The OggIterator class helps iterating through all segments of an OGG bitstream.
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*
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* If an OggIterator has just been constructed it is invalid. To fetch the first page from
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* the stream call the reset() method. The iterator will now point to the first segment of the
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* first page.
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*
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* To go on call the appropriate methods. Parsing exceptions and IO exceptions might occur during iteration.
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*
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* The internal buffer of OGG pages might be accessed using the pages() method.
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*/
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/*!
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* \brief Sets the stream and related parameters and clears all available pages.
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* \remarks Invalidates the iterator. Use reset() to continue iteration.
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*/
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void OggIterator::clear(istream &stream, uint64 startOffset, uint64 streamSize)
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{
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m_stream = &stream;
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m_startOffset = startOffset;
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m_streamSize = streamSize;
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m_pages.clear();
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}
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/*!
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* \brief Resets the iterator to point at the first segment of the first page (matching the filter if set).
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*
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* Fetched pages (directly accessable through the page() method) remain after resetting the iterator. Use
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* clear() to clear all pages.
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*/
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void OggIterator::reset()
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{
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for(m_page = m_segment = m_offset = 0; m_page < m_pages.size() || fetchNextPage(); ++m_page) {
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const OggPage &page = m_pages[m_page];
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if(!page.segmentSizes().empty() && matchesFilter(page)) {
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// page is not empty and matches ID filter if set
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m_offset = page.startOffset() + page.headerSize();
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break;
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}
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}
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// no matching page found -> iterator is invalid
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}
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/*!
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* \brief Increases the current position by one page.
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* \remarks The iterator must be valid. The iterator might be invalidated.
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*/
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void OggIterator::nextPage()
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{
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while(++m_page < m_pages.size() || fetchNextPage()) {
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const OggPage &page = m_pages[m_page];
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if(!page.segmentSizes().empty() && matchesFilter(page)) {
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// page is not empty and matches ID filter if set
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m_segment = m_bytesRead = 0;
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m_offset = page.startOffset() + page.headerSize();
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return;
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}
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}
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// no next page available -> iterator is in invalid state
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}
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/*!
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* \brief Increases the current position by one segment.
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* \remarks The iterator must be valid. The iterator might be invalidated.
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*/
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void OggIterator::nextSegment()
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{
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const OggPage &page = m_pages[m_page];
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if(matchesFilter(page) && ++m_segment < page.segmentSizes().size()) {
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// current page has next segment
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m_bytesRead = 0;
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m_offset += page.segmentSizes()[m_segment - 1];
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} else {
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// next (matching) page has next segment
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nextPage();
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}
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}
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/*!
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* \brief Decreases the current position by one page.
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* \remarks The iterator must be valid. The iterator might be invalidated.
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*/
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void OggIterator::previousPage()
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{
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while(m_page) {
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const OggPage &page = m_pages[--m_page];
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if(matchesFilter(page)) {
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m_offset = page.dataOffset(m_segment = page.segmentSizes().size() - 1);
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return;
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}
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}
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}
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/*!
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* \brief Decreases the current position by one segment.
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* \remarks The iterator must be valid. The iterator might be invalidated.
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*/
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void OggIterator::previousSegment()
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{
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const OggPage &page = m_pages[m_page];
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if(m_segment && matchesFilter(page)) {
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m_offset -= page.segmentSizes()[m_segment--];
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} else {
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previousPage();
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}
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}
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/*!
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* \brief Reads \a count bytes from the OGG stream and writes it to the specified \a buffer.
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* \remarks
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* - Might increase the current page index and/or the current segment index.
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* - Page headers are skipped (this is the whole purpose of this method).
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* \throws Throws a TruncatedDataException if the end of the stream is reached before \a count bytes
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* have been read.
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* \sa readAll()
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* \sa currentCharacterOffset()
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* \sa seekForward()
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*/
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void OggIterator::read(char *buffer, size_t count)
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{
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size_t bytesRead = 0;
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while(*this && count) {
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const uint32 available = currentSegmentSize() - m_bytesRead;
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stream().seekg(currentCharacterOffset());
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if(count <= available) {
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stream().read(buffer + bytesRead, count);
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m_bytesRead += count;
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return;
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} else {
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stream().read(buffer + bytesRead, available);
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nextSegment();
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bytesRead += available;
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count -= available;
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}
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}
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if(count) {
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// still bytes to read but no more available
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throw TruncatedDataException();
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}
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}
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/*!
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* \brief Reads all bytes from the OGG stream and writes it to the specified \a buffer.
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* \remarks
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* - Might increase the current page index and/or the current segment index.
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* - Page headers are skipped (this is the whole purpose of this method).
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* - Does not read more than \a max bytes from the buffer.
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* \sa read()
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* \sa currentCharacterOffset()
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* \sa seekForward()
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*/
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size_t OggIterator::readAll(char *buffer, size_t max)
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{
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size_t bytesRead = 0;
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while(*this && max) {
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const uint32 available = currentSegmentSize() - m_bytesRead;
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stream().seekg(currentCharacterOffset());
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if(max <= available) {
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stream().read(buffer + bytesRead, max);
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m_bytesRead += max;
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return bytesRead + max;
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} else {
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stream().read(buffer + bytesRead, available);
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nextSegment();
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bytesRead += available;
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max -= available;
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}
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}
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return bytesRead;
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}
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/*!
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* \brief Advances the position of the next character to be read from the OGG stream by \a count bytes.
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* \remarks
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* - Might increase the current page index and/or the current segment index.
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* - Page headers are skipped (this is the whole purpose of this method).
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* - Seeking backward is not implemented yet since there is currently no use for such a method.
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* \throws Throws a TruncatedDataException if the end of the stream is exceeded.
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* \sa currentCharacterOffset()
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* \sa read()
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*/
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void OggIterator::ignore(size_t count)
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{
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uint32 available = currentSegmentSize() - m_bytesRead;
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while(*this) {
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available = currentSegmentSize() - m_bytesRead;
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if(count <= available) {
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m_bytesRead += count;
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return;
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} else {
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nextSegment();
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count -= available;
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}
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}
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throw TruncatedDataException();
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}
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/*!
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* \brief Fetches the next page.
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*
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* A new page can only be fetched if the current page is the last page in the buffer and if the
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* end of the input stream has not been reached yet.
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*
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* \returns Returns an indication whether the next page could be fetched.
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* \throws Throws std::ios_base::failure when an IO error occurs.
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* \throws Throws Failure when a parsing error occurs.
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*/
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bool OggIterator::fetchNextPage()
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{
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if(m_page == m_pages.size()) { // can only fetch the next page if the current page is the last page
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m_offset = m_pages.empty() ? m_startOffset : m_pages.back().startOffset() + m_pages.back().totalSize();
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if(m_offset < m_streamSize) {
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m_pages.emplace_back(*m_stream, m_offset, static_cast<int32>(m_streamSize - m_offset));
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return true;
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}
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}
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return false;
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}
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}
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