InputStream: make Seek() always absolute

Remove the "whence" parameter that is not actually necessary, and only
complicates the InputStream implementations.

src/archive/plugins/ZzipArchivePlugin.cxx

@@ -125,7 +125,7 @@ struct ZzipInputStream final : public InputStream {
 	/* virtual methods from InputStream */
 	bool IsEOF() override;
 	size_t Read(void *ptr, size_t size, Error &error) override;
-	bool Seek(offset_type offset, int whence, Error &error) override;
+	bool Seek(offset_type offset, Error &error) override;
 };
 
 InputStream *
@@ -165,9 +165,9 @@ ZzipInputStream::IsEOF()
 }
 
 bool
-ZzipInputStream::Seek(offset_type new_offset, int whence, Error &error)
+ZzipInputStream::Seek(offset_type new_offset, Error &error)
 {
-	zzip_off_t ofs = zzip_seek(file, new_offset, whence);
+	zzip_off_t ofs = zzip_seek(file, new_offset, SEEK_SET);
 	if (ofs != -1) {
 		error.Set(zzip_domain, "zzip_seek() has failed");
 		offset = ofs;

src/decoder/plugins/AudiofileDecoderPlugin.cxx

@@ -92,13 +92,17 @@ audiofile_file_destroy(AFvirtualfile *vfile)
 }
 
 static AFfileoffset
-audiofile_file_seek(AFvirtualfile *vfile, AFfileoffset offset, int is_relative)
+audiofile_file_seek(AFvirtualfile *vfile, AFfileoffset _offset,
+		    int is_relative)
 {
 	InputStream &is = *(InputStream *)vfile->closure;
-	int whence = (is_relative ? SEEK_CUR : SEEK_SET);
+
+	InputStream::offset_type offset = _offset;
+	if (is_relative)
+		offset += is.GetOffset();
 
 	Error error;
-	if (is.LockSeek(offset, whence, error)) {
+	if (is.LockSeek(offset, IgnoreError())) {
 		return is.GetOffset();
 	} else {
 		return -1;

src/decoder/plugins/DsdLib.cxx

@@ -30,9 +30,7 @@
 #include "tag/TagId3.hxx"
 #include "util/Error.hxx"
 
-#include <unistd.h>
 #include <string.h>
-#include <stdio.h> /* for SEEK_SET, SEEK_CUR */
 
 #ifdef HAVE_ID3TAG
 #include <id3tag.h>
@@ -63,7 +61,7 @@ dsdlib_skip_to(Decoder *decoder, InputStream &is,
 	       int64_t offset)
 {
 	if (is.IsSeekable())
-		return is.Seek(offset, SEEK_SET, IgnoreError());
+		return is.Seek(offset, IgnoreError());
 
 	if (is.GetOffset() > offset)
 		return false;
@@ -96,7 +94,7 @@ dsdlib_skip(Decoder *decoder, InputStream &is,
 		return true;
 
 	if (is.IsSeekable())
-		return is.Seek(delta, SEEK_CUR, IgnoreError());
+		return is.Seek(is.GetOffset() + delta, IgnoreError());
 
 	char buffer[8192];
 	while (delta > 0) {

src/decoder/plugins/FaadDecoderPlugin.cxx

@@ -186,7 +186,7 @@ faad_song_duration(DecoderBuffer *buffer, InputStream &is)
 		/* obtain the duration from the ADTS header */
 		float song_length = adts_song_duration(buffer);
 
-		is.LockSeek(tagsize, SEEK_SET, IgnoreError());
+		is.LockSeek(tagsize, IgnoreError());
 
 		decoder_buffer_clear(buffer);
 		decoder_buffer_fill(buffer);

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -120,10 +120,29 @@ mpd_ffmpeg_stream_seek(void *opaque, int64_t pos, int whence)
 {
 	AvioStream *stream = (AvioStream *)opaque;
 
-	if (whence == AVSEEK_SIZE)
+	switch (whence) {
+	case SEEK_SET:
+		break;
+
+	case SEEK_CUR:
+		pos += stream->input.GetOffset();
+		break;
+
+	case SEEK_END:
+		if (!stream->input.KnownSize())
+			return -1;
+
+		pos += stream->input.GetSize();
+		break;
+
+	case AVSEEK_SIZE:
 		return stream->input.GetSize();
 
-	if (!stream->input.LockSeek(pos, whence, IgnoreError()))
+	default:
+		return -1;
+	}
+
+	if (!stream->input.LockSeek(pos, IgnoreError()))
 		return -1;
 
 	return stream->input.GetOffset();

src/decoder/plugins/FlacIOHandle.cxx

@@ -62,12 +62,31 @@ FlacIORead(void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle)
 }
 
 static int
-FlacIOSeek(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
+FlacIOSeek(FLAC__IOHandle handle, FLAC__int64 _offset, int whence)
 {
 	InputStream *is = (InputStream *)handle;
 
-	Error error;
-	return is->LockSeek(offset, whence, error) ? 0 : -1;
+	InputStream::offset_type offset = _offset;
+	switch (whence) {
+	case SEEK_SET:
+		break;
+
+	case SEEK_CUR:
+		offset += is->GetOffset();
+		break;
+
+	case SEEK_END:
+		if (!is->KnownSize())
+			return -1;
+
+		offset += is->GetSize();
+		break;
+
+	default:
+		return -1;
+	}
+
+	return is->LockSeek(offset, IgnoreError()) ? 0 : -1;
 }
 
 static FLAC__int64

src/decoder/plugins/FlacInput.cxx

@@ -51,7 +51,7 @@ FlacInput::Seek(FLAC__uint64 absolute_byte_offset)
 		return FLAC__STREAM_DECODER_SEEK_STATUS_UNSUPPORTED;
 
 	::Error error;
-	if (!input_stream.LockSeek(absolute_byte_offset, SEEK_SET, error)) {
+	if (!input_stream.LockSeek(absolute_byte_offset, error)) {
 		LogError(error);
 		return FLAC__STREAM_DECODER_SEEK_STATUS_ERROR;
 	}

src/decoder/plugins/MadDecoderPlugin.cxx

@@ -208,7 +208,7 @@ inline bool
 MadDecoder::Seek(long offset)
 {
 	Error error;
-	if (!input_stream.LockSeek(offset, SEEK_SET, error))
+	if (!input_stream.LockSeek(offset, error))
 		return false;
 
 	mad_stream_buffer(&stream, input_buffer, 0);

src/decoder/plugins/MpcdecDecoderPlugin.cxx

@@ -57,7 +57,7 @@ mpc_seek_cb(mpc_reader *reader, mpc_int32_t offset)
 	struct mpc_decoder_data *data =
 		(struct mpc_decoder_data *)reader->data;
 
-	return data->is.LockSeek(offset, SEEK_SET, IgnoreError());
+	return data->is.LockSeek(offset, IgnoreError());
 }
 
 static mpc_int32_t

src/decoder/plugins/OggFind.cxx

@@ -22,8 +22,6 @@
 #include "OggSyncState.hxx"
 #include "util/Error.hxx"
 
-#include <stdio.h>
-
 bool
 OggFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet)
 {
@@ -41,28 +39,31 @@ OggFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet)
 
 bool
 OggSeekPageAtOffset(OggSyncState &oy, ogg_stream_state &os, InputStream &is,
-		    InputStream::offset_type offset, int whence)
+		    InputStream::offset_type offset)
 {
 	oy.Reset();
 
 	/* reset the stream to clear any previous partial packet
 	   data */
 	ogg_stream_reset(&os);
 
-	return is.LockSeek(offset, whence, IgnoreError()) &&
+	return is.LockSeek(offset, IgnoreError()) &&
 		oy.ExpectPageSeekIn(os);
 }
 
 bool
 OggSeekFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet,
 	       InputStream &is)
 {
-	if (is.KnownSize() && is.GetRest() < 65536)
+	if (!is.KnownSize())
+		return false;
+
+	if (is.GetRest() < 65536)
 		return OggFindEOS(oy, os, packet);
 
 	if (!is.CheapSeeking())
 		return false;
 
-	return OggSeekPageAtOffset(oy, os, is, -65536, SEEK_END) &&
+	return OggSeekPageAtOffset(oy, os, is, is.GetSize() - 65536) &&
 		OggFindEOS(oy, os, packet);
 }

src/decoder/plugins/OggFind.hxx

@@ -41,7 +41,7 @@ OggFindEOS(OggSyncState &oy, ogg_stream_state &os, ogg_packet &packet);
  */
 bool
 OggSeekPageAtOffset(OggSyncState &oy, ogg_stream_state &os, InputStream &is,
-		    InputStream::offset_type offset, int whence);
+		    InputStream::offset_type offset);
 
 /**
  * Try to find the end-of-stream (EOS) packet.  Seek to the end of the

src/decoder/plugins/OpusDecoderPlugin.cxx

@@ -199,7 +199,7 @@ LoadEOSPacket(InputStream &is, Decoder *decoder, int serialno,
 	ogg_stream_clear(&os);
 
 	/* restore the previous file position */
-	is.Seek(old_offset, SEEK_SET, IgnoreError());
+	is.Seek(old_offset, IgnoreError());
 
 	return result;
 }
@@ -344,7 +344,7 @@ MPDOpusDecoder::Seek(OggSyncState &oy, double where_s)
 	InputStream::offset_type offset(where_granulepos * input_stream.GetSize()
 					/ eos_granulepos);
 
-	if (!OggSeekPageAtOffset(oy, os, input_stream, offset, SEEK_SET))
+	if (!OggSeekPageAtOffset(oy, os, input_stream, offset))
 		return false;
 
 	decoder_timestamp(decoder, where_s);

src/decoder/plugins/PcmDecoderPlugin.cxx

@@ -26,7 +26,6 @@
 #include "Log.hxx"
 
 #include <string.h>
-#include <stdio.h> /* for SEEK_SET */
 
 static void
 pcm_stream_decode(Decoder &decoder, InputStream &is)
@@ -76,7 +75,7 @@ pcm_stream_decode(Decoder &decoder, InputStream &is)
 							decoder_seek_where(decoder));
 
 			Error error;
-			if (is.LockSeek(offset, SEEK_SET, error)) {
+			if (is.LockSeek(offset, error)) {
 				decoder_command_finished(decoder);
 			} else {
 				LogError(error);

src/decoder/plugins/SndfileDecoderPlugin.cxx

@@ -41,11 +41,31 @@ sndfile_vio_get_filelen(void *user_data)
 }
 
 static sf_count_t
-sndfile_vio_seek(sf_count_t offset, int whence, void *user_data)
+sndfile_vio_seek(sf_count_t _offset, int whence, void *user_data)
 {
 	InputStream &is = *(InputStream *)user_data;
 
-	if (!is.LockSeek(offset, whence, IgnoreError()))
+	InputStream::offset_type offset = _offset;
+	switch (whence) {
+	case SEEK_SET:
+		break;
+
+	case SEEK_CUR:
+		offset += is.GetOffset();
+		break;
+
+	case SEEK_END:
+		if (!is.KnownSize())
+			return -1;
+
+		offset += is.GetSize();
+		break;
+
+	default:
+		return -1;
+	}
+
+	if (!is.LockSeek(offset, IgnoreError()))
 		return -1;
 
 	return is.GetOffset();

src/decoder/plugins/VorbisDecoderPlugin.cxx

@@ -70,15 +70,37 @@ static size_t ogg_read_cb(void *ptr, size_t size, size_t nmemb, void *data)
 	return ret / size;
 }
 
-static int ogg_seek_cb(void *data, ogg_int64_t offset, int whence)
+static int ogg_seek_cb(void *data, ogg_int64_t _offset, int whence)
 {
 	VorbisInputStream *vis = (VorbisInputStream *)data;
+	InputStream &is = vis->input_stream;
 
-	Error error;
-	return vis->seekable &&
-		(vis->decoder == nullptr ||
-		 decoder_get_command(*vis->decoder) != DecoderCommand::STOP) &&
-		vis->input_stream.LockSeek(offset, whence, error)
+	if (!vis->seekable ||
+	    (vis->decoder != nullptr &&
+	     decoder_get_command(*vis->decoder) == DecoderCommand::STOP))
+		return -1;
+
+	InputStream::offset_type offset = _offset;
+	switch (whence) {
+	case SEEK_SET:
+		break;
+
+	case SEEK_CUR:
+		offset += is.GetOffset();
+		break;
+
+	case SEEK_END:
+		if (!is.KnownSize())
+			return -1;
+
+		offset += is.GetSize();
+		break;
+
+	default:
+		return -1;
+	}
+
+	return is.LockSeek(offset, IgnoreError())
 		? 0 : -1;
 }
 

src/decoder/plugins/WavpackDecoderPlugin.cxx

@@ -392,13 +392,35 @@ wavpack_input_get_pos(void *id)
 static int
 wavpack_input_set_pos_abs(void *id, uint32_t pos)
 {
-	return wpin(id)->is.LockSeek(pos, SEEK_SET, IgnoreError()) ? 0 : -1;
+	return wpin(id)->is.LockSeek(pos, IgnoreError()) ? 0 : -1;
 }
 
 static int
 wavpack_input_set_pos_rel(void *id, int32_t delta, int mode)
 {
-	return wpin(id)->is.LockSeek(delta, mode, IgnoreError()) ? 0 : -1;
+	InputStream &is = wpin(id)->is;
+
+	InputStream::offset_type offset = delta;
+	switch (mode) {
+	case SEEK_SET:
+		break;
+
+	case SEEK_CUR:
+		offset += is.GetOffset();
+		break;
+
+	case SEEK_END:
+		if (!is.KnownSize())
+			return -1;
+
+		offset += is.GetSize();
+		break;
+
+	default:
+		return -1;
+	}
+
+	return is.LockSeek(offset, IgnoreError()) ? 0 : -1;
 }
 
 static int