InputStream: make Seek() always absolute

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

27 files changed, 181 insertions, 124 deletions

diff --git a/src/archive/plugins/ZzipArchivePlugin.cxx b/src/archive/plugins/ZzipArchivePlugin.cxx
index 436ebc793..396055c71 100644
--- a/src/archive/plugins/ZzipArchivePlugin.cxx
+++ b/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;
diff --git a/src/decoder/plugins/AudiofileDecoderPlugin.cxx b/src/decoder/plugins/AudiofileDecoderPlugin.cxx
index 262c4a5bf..a3f0ee380 100644
--- a/src/decoder/plugins/AudiofileDecoderPlugin.cxx
+++ b/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;
diff --git a/src/decoder/plugins/DsdLib.cxx b/src/decoder/plugins/DsdLib.cxx
index f77d8f59a..2bd532a05 100644
--- a/src/decoder/plugins/DsdLib.cxx
+++ b/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) {
diff --git a/src/decoder/plugins/FaadDecoderPlugin.cxx b/src/decoder/plugins/FaadDecoderPlugin.cxx
index e80665d24..c7f72da15 100644
--- a/src/decoder/plugins/FaadDecoderPlugin.cxx
+++ b/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);
diff --git a/src/decoder/plugins/FfmpegDecoderPlugin.cxx b/src/decoder/plugins/FfmpegDecoderPlugin.cxx
index 22a42477d..9139a622b 100644
--- a/src/decoder/plugins/FfmpegDecoderPlugin.cxx
+++ b/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();
diff --git a/src/decoder/plugins/FlacIOHandle.cxx b/src/decoder/plugins/FlacIOHandle.cxx
index 6444e02cf..b5f9f5ec0 100644
--- a/src/decoder/plugins/FlacIOHandle.cxx
+++ b/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
diff --git a/src/decoder/plugins/FlacInput.cxx b/src/decoder/plugins/FlacInput.cxx
index d7fc72025..5b4c3104d 100644
--- a/src/decoder/plugins/FlacInput.cxx
+++ b/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;
 	}
diff --git a/src/decoder/plugins/MadDecoderPlugin.cxx b/src/decoder/plugins/MadDecoderPlugin.cxx
index ffd63a2ac..886aa1795 100644
--- a/src/decoder/plugins/MadDecoderPlugin.cxx
+++ b/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);
diff --git a/src/decoder/plugins/MpcdecDecoderPlugin.cxx b/src/decoder/plugins/MpcdecDecoderPlugin.cxx
index 18f6e7673..f86cb3c81 100644
--- a/src/decoder/plugins/MpcdecDecoderPlugin.cxx
+++ b/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
diff --git a/src/decoder/plugins/OggFind.cxx b/src/decoder/plugins/OggFind.cxx
index d7a3dc04a..15e9c5c92 100644
--- a/src/decoder/plugins/OggFind.cxx
+++ b/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)
 {
@@ -41,7 +39,7 @@ 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)
 {
 	oy.Reset();
 
@@ -49,7 +47,7 @@ OggSeekPageAtOffset(OggSyncState &oy, ogg_stream_state &os, InputStream &is,
 	   data */
 	ogg_stream_reset(&os);
 
-	return is.LockSeek(offset, whence, IgnoreError()) &&
+	return is.LockSeek(offset, IgnoreError()) &&
 		oy.ExpectPageSeekIn(os);
 }
 
@@ -57,12 +55,15 @@ 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);
 }
diff --git a/src/decoder/plugins/OggFind.hxx b/src/decoder/plugins/OggFind.hxx
index d93b87505..8ced7fd86 100644
--- a/src/decoder/plugins/OggFind.hxx
+++ b/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
diff --git a/src/decoder/plugins/OpusDecoderPlugin.cxx b/src/decoder/plugins/OpusDecoderPlugin.cxx
index 983d17278..27c559272 100644
--- a/src/decoder/plugins/OpusDecoderPlugin.cxx
+++ b/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);
diff --git a/src/decoder/plugins/PcmDecoderPlugin.cxx b/src/decoder/plugins/PcmDecoderPlugin.cxx
index e7e593550..3b9c60691 100644
--- a/src/decoder/plugins/PcmDecoderPlugin.cxx
+++ b/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);
diff --git a/src/decoder/plugins/SndfileDecoderPlugin.cxx b/src/decoder/plugins/SndfileDecoderPlugin.cxx
index 6d9e0d31e..cf3aa61d5 100644
--- a/src/decoder/plugins/SndfileDecoderPlugin.cxx
+++ b/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();
diff --git a/src/decoder/plugins/VorbisDecoderPlugin.cxx b/src/decoder/plugins/VorbisDecoderPlugin.cxx
index 4fe44e9e8..72542e3a2 100644
--- a/src/decoder/plugins/VorbisDecoderPlugin.cxx
+++ b/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;
 }
 
diff --git a/src/decoder/plugins/WavpackDecoderPlugin.cxx b/src/decoder/plugins/WavpackDecoderPlugin.cxx
index 9d65775c1..2f60090c1 100644
--- a/src/decoder/plugins/WavpackDecoderPlugin.cxx
+++ b/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
diff --git a/src/input/InputStream.cxx b/src/input/InputStream.cxx
index e7307540d..657b9df09 100644
--- a/src/input/InputStream.cxx
+++ b/src/input/InputStream.cxx
@@ -23,7 +23,6 @@
 #include "util/UriUtil.hxx"
 
 #include <assert.h>
-#include <stdio.h> /* for SEEK_SET */
 
 InputStream::~InputStream()
 {
@@ -75,29 +74,17 @@ InputStream::CheapSeeking() const
 }
 
 bool
-InputStream::Seek(gcc_unused offset_type new_offset, gcc_unused int whence,
+InputStream::Seek(gcc_unused offset_type new_offset,
 		  gcc_unused Error &error)
 {
 	return false;
 }
 
 bool
-InputStream::LockSeek(offset_type _offset, int whence, Error &error)
+InputStream::LockSeek(offset_type _offset, Error &error)
 {
 	const ScopeLock protect(mutex);
-	return Seek(_offset, whence, error);
-}
-
-bool
-InputStream::Rewind(Error &error)
-{
-	return Seek(0, SEEK_SET, error);
-}
-
-bool
-InputStream::LockRewind(Error &error)
-{
-	return LockSeek(0, SEEK_SET, error);
+	return Seek(_offset, error);
 }
 
 Tag *
diff --git a/src/input/InputStream.hxx b/src/input/InputStream.hxx
index 5f754940b..25e99de3d 100644
--- a/src/input/InputStream.hxx
+++ b/src/input/InputStream.hxx
@@ -275,22 +275,26 @@ public:
 	 * The caller must lock the mutex.
 	 *
 	 * @param offset the relative offset
-	 * @param whence the base of the seek, one of SEEK_SET, SEEK_CUR, SEEK_END
 	 */
-	virtual bool Seek(offset_type offset, int whence, Error &error);
+	virtual bool Seek(offset_type offset, Error &error);
 
 	/**
 	 * Wrapper for Seek() which locks and unlocks the mutex; the
 	 * caller must not be holding it already.
 	 */
-	bool LockSeek(offset_type offset, int whence, Error &error);
+	bool LockSeek(offset_type offset, Error &error);
 
 	/**
 	 * Rewind to the beginning of the stream.  This is a wrapper
-	 * for Seek(0, SEEK_SET, error).
+	 * for Seek(0, error).
 	 */
-	bool Rewind(Error &error);
-	bool LockRewind(Error &error);
+	bool Rewind(Error &error) {
+		return Seek(0, error);
+	}
+
+	bool LockRewind(Error &error) {
+		return LockSeek(0, error);
+	}
 
 	/**
 	 * Returns true if the stream has reached end-of-file.
diff --git a/src/input/ProxyInputStream.cxx b/src/input/ProxyInputStream.cxx
index 7b6e9f937..d65fb5df1 100644
--- a/src/input/ProxyInputStream.cxx
+++ b/src/input/ProxyInputStream.cxx
@@ -63,9 +63,9 @@ ProxyInputStream::Update()
 }
 
 bool
-ProxyInputStream::Seek(offset_type new_offset, int whence, Error &error)
+ProxyInputStream::Seek(offset_type new_offset, Error &error)
 {
-	bool success = input.Seek(new_offset, whence, error);
+	bool success = input.Seek(new_offset, error);
 	CopyAttributes();
 	return success;
 }
diff --git a/src/input/ProxyInputStream.hxx b/src/input/ProxyInputStream.hxx
index b2049fbc0..727ae5917 100644
--- a/src/input/ProxyInputStream.hxx
+++ b/src/input/ProxyInputStream.hxx
@@ -45,7 +45,7 @@ public:
 	/* virtual methods from InputStream */
 	bool Check(Error &error) override;
 	void Update() override;
-	bool Seek(offset_type new_offset, int whence, Error &error) override;
+	bool Seek(offset_type new_offset, Error &error) override;
 	bool IsEOF() override;
 	Tag *ReadTag() override;
 	bool IsAvailable() override;
diff --git a/src/input/plugins/CdioParanoiaInputPlugin.cxx b/src/input/plugins/CdioParanoiaInputPlugin.cxx
index 534084e0d..6f1ea976a 100644
--- a/src/input/plugins/CdioParanoiaInputPlugin.cxx
+++ b/src/input/plugins/CdioParanoiaInputPlugin.cxx
@@ -99,7 +99,7 @@ class CdioParanoiaInputStream 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;
 };
 
 static constexpr Domain cdio_domain("cdio");
@@ -272,21 +272,8 @@ input_cdio_open(const char *uri,
 }
 
 bool
-CdioParanoiaInputStream::Seek(InputPlugin::offset_type new_offset,
-			      int whence, Error &error)
+CdioParanoiaInputStream::Seek(offset_type new_offset, Error &error)
 {
-	/* calculate absolute offset */
-	switch (whence) {
-	case SEEK_SET:
-		break;
-	case SEEK_CUR:
-		new_offset += offset;
-		break;
-	case SEEK_END:
-		new_offset += size;
-		break;
-	}
-
 	if (new_offset < 0 || new_offset > size) {
 		error.Format(cdio_domain, "Invalid offset to seek %ld (%ld)",
 			     (long int)new_offset, (long int)size);
diff --git a/src/input/plugins/CurlInputPlugin.cxx b/src/input/plugins/CurlInputPlugin.cxx
index dc26e0aa2..e464a3ce0 100644
--- a/src/input/plugins/CurlInputPlugin.cxx
+++ b/src/input/plugins/CurlInputPlugin.cxx
@@ -175,7 +175,7 @@ struct CurlInputStream final : public InputStream {
 	}
 
 	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;
 };
 
 class CurlMulti;
@@ -887,12 +887,11 @@ CurlInputStream::InitEasy(Error &error)
 }
 
 inline bool
-CurlInputStream::Seek(InputPlugin::offset_type new_offset, int whence,
-		      Error &error)
+CurlInputStream::Seek(offset_type new_offset, Error &error)
 {
 	assert(IsReady());
 
-	if (whence == SEEK_SET && new_offset == offset)
+	if (new_offset == offset)
 		/* no-op */
 		return true;
 
@@ -901,26 +900,6 @@ CurlInputStream::Seek(InputPlugin::offset_type new_offset, int whence,
 
 	/* calculate the absolute offset */
 
-	switch (whence) {
-	case SEEK_SET:
-		break;
-
-	case SEEK_CUR:
-		new_offset += offset;
-		break;
-
-	case SEEK_END:
-		if (size < 0)
-			/* stream size is not known */
-			return false;
-
-		new_offset += size;
-		break;
-
-	default:
-		return false;
-	}
-
 	if (new_offset < 0)
 		return false;
 
diff --git a/src/input/plugins/FfmpegInputPlugin.cxx b/src/input/plugins/FfmpegInputPlugin.cxx
index 9ae07dbef..6e0260aee 100644
--- a/src/input/plugins/FfmpegInputPlugin.cxx
+++ b/src/input/plugins/FfmpegInputPlugin.cxx
@@ -60,7 +60,7 @@ struct FfmpegInputStream 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;
 };
 
 static constexpr Domain ffmpeg_domain("ffmpeg");
@@ -134,9 +134,9 @@ FfmpegInputStream::IsEOF()
 }
 
 bool
-FfmpegInputStream::Seek(offset_type new_offset, int whence, Error &error)
+FfmpegInputStream::Seek(offset_type new_offset, Error &error)
 {
-	int64_t ret = avio_seek(h, new_offset, whence);
+	int64_t ret = avio_seek(h, new_offset, SEEK_SET);
 
 	if (ret >= 0) {
 		eof = false;
diff --git a/src/input/plugins/FileInputPlugin.cxx b/src/input/plugins/FileInputPlugin.cxx
index 1035973b6..60c316567 100644
--- a/src/input/plugins/FileInputPlugin.cxx
+++ b/src/input/plugins/FileInputPlugin.cxx
@@ -56,7 +56,7 @@ struct FileInputStream final : public InputStream {
 	}
 
 	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;
 };
 
 static InputStream *
@@ -99,11 +99,9 @@ input_file_open(const char *filename,
 }
 
 bool
-FileInputStream::Seek(InputPlugin::offset_type new_offset, int whence,
-		      Error &error)
+FileInputStream::Seek(offset_type new_offset, Error &error)
 {
-	new_offset = (InputPlugin::offset_type)lseek(fd, (off_t)new_offset,
-						     whence);
+	new_offset = (offset_type)lseek(fd, (off_t)new_offset, SEEK_SET);
 	if (new_offset < 0) {
 		error.SetErrno("Failed to seek");
 		return false;
diff --git a/src/input/plugins/NfsInputPlugin.cxx b/src/input/plugins/NfsInputPlugin.cxx
index b73389662..c90f00257 100644
--- a/src/input/plugins/NfsInputPlugin.cxx
+++ b/src/input/plugins/NfsInputPlugin.cxx
@@ -61,7 +61,7 @@ public:
 	}
 
 	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;
 };
 
 size_t
@@ -77,10 +77,10 @@ NfsInputStream::Read(void *ptr, size_t read_size, Error &error)
 }
 
 bool
-NfsInputStream::Seek(offset_type new_offset, int whence, Error &error)
+NfsInputStream::Seek(offset_type new_offset, Error &error)
 {
 	uint64_t current_offset;
-	int result = nfs_lseek(ctx, fh, new_offset, whence,
+	int result = nfs_lseek(ctx, fh, new_offset, SEEK_SET,
 			       &current_offset);
 	if (result < 0) {
 		error.SetErrno(-result, "smbc_lseek() failed");
diff --git a/src/input/plugins/RewindInputPlugin.cxx b/src/input/plugins/RewindInputPlugin.cxx
index c18799c64..95f604044 100644
--- a/src/input/plugins/RewindInputPlugin.cxx
+++ b/src/input/plugins/RewindInputPlugin.cxx
@@ -64,7 +64,7 @@ public:
 	}
 
 	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;
 
 private:
 	/**
@@ -117,13 +117,12 @@ RewindInputStream::Read(void *ptr, size_t read_size, Error &error)
 }
 
 bool
-RewindInputStream::Seek(offset_type new_offset, int whence,
+RewindInputStream::Seek(offset_type new_offset,
 			Error &error)
 {
 	assert(IsReady());
 
-	if (whence == SEEK_SET && tail > 0 &&
-	    new_offset <= (offset_type)tail) {
+	if (tail > 0 && new_offset <= (offset_type)tail) {
 		/* buffered seek */
 
 		assert(!ReadingFromBuffer() ||
@@ -139,7 +138,7 @@ RewindInputStream::Seek(offset_type new_offset, int whence,
 		   buffered range now */
 		tail = 0;
 
-		return ProxyInputStream::Seek(new_offset, whence, error);
+		return ProxyInputStream::Seek(new_offset, error);
 	}
 }
 
diff --git a/src/input/plugins/SmbclientInputPlugin.cxx b/src/input/plugins/SmbclientInputPlugin.cxx
index aa1ba0381..79987180f 100644
--- a/src/input/plugins/SmbclientInputPlugin.cxx
+++ b/src/input/plugins/SmbclientInputPlugin.cxx
@@ -57,7 +57,7 @@ public:
 	}
 
 	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;
 };
 
 /*
@@ -136,11 +136,10 @@ SmbclientInputStream::Read(void *ptr, size_t read_size, Error &error)
 }
 
 bool
-SmbclientInputStream::Seek(InputStream::offset_type new_offset,
-			   int whence, Error &error)
+SmbclientInputStream::Seek(offset_type new_offset, Error &error)
 {
 	smbclient_mutex.lock();
-	off_t result = smbc_lseek(fd, new_offset, whence);
+	off_t result = smbc_lseek(fd, new_offset, SEEK_SET);
 	smbclient_mutex.unlock();
 	if (result < 0) {
 		error.SetErrno("smbc_lseek() failed");