hSeek is:exact

Computation hSeek hdl mode i sets the position of handle hdl depending on mode. The offset i is given in terms of 8-bit bytes. If hdl is block- or line-buffered, then seeking to a position which is not in the current buffer will first cause any items in the output buffer to be written to the device, and then cause the input buffer to be discarded. Some handles may not be seekable (see hIsSeekable), or only support a subset of the possible positioning operations (for instance, it may only be possible to seek to the end of a tape, or to a positive offset from the beginning or current position). It is not possible to set a negative I/O position, or for a physical file, an I/O position beyond the current end-of-file. This operation may fail with:

• isIllegalOperationError if the Handle is not seekable, or does not support the requested seek mode.
• isPermissionError if a system resource limit would be exceeded.

Lifted version of hSeek

The file seek functions work much like hseek with the exception that the non-audio data is ignored and the seek only moves within the audio data section of the file. In addition, seeks are defined in number of (multichannel) frames. Therefore, a seek in a stereo file from the current position forward with an offset of 1 would skip forward by one sample of both channels. like lseek(), the whence parameter can be any one of the following three values:

• AbsoluteSeek - The offset is set to the start of the audio data plus offset (multichannel) frames.
• RelativeSeek - The offset is set to its current location plus offset (multichannel) frames.
• SeekFromEnd - The offset is set to the end of the data plus offset (multichannel) frames.

Internally, libsndfile keeps track of the read and write locations using separate read and write pointers. If a file has been opened with a mode of ReadWriteMode, calling either hSeekRead or hSeekWrite allows the read and write pointers to be modified separately. hSeek modifies both the read and the write pointer. Note that the frames offset can be negative and in fact should be when SeekFromEnd is used for the whence parameter. hSeek will return the offset in (multichannel) frames from the start of the audio data, or signal an error when an attempt is made to seek beyond the start or end of the file.