60 lines
2.2 KiB
C
60 lines
2.2 KiB
C
#ifndef MPG123_H_INDEX
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#define MPG123_H_INDEX
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/*
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index: frame index data structure and functions
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This is for keeping track of frame positions for accurate seeking.
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Now in it's own file, with initial code from frame.c and parse.c .
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The idea of the index with a certain amount of entries is to cover
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all yet-encountered frame positions with minimal coarseness.
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Meaning: At first every frame position is recorded, then, when
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the index is full, every second position is trown away to make
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space. Next time it is full, the same happens. And so on.
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In this manner we maintain a good resolution with the given
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maximum index size while covering the whole stream.
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copyright 2007-8 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Thomas Orgis
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*/
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#include "config.h"
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#include "compat.h"
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struct frame_index
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{
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off_t *data; /* actual data, the frame positions */
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off_t step; /* advancement in frame number per index point */
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off_t next; /* frame offset supposed to come next into the index */
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size_t size; /* total number of possible entries */
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size_t fill; /* number of used entries */
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size_t grow_size; /* if > 0: index allowed to grow on need with these steps, instead of lowering resolution */
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};
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/* The condition for a framenum to be appended to the index.
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if(FI_NEXT(fr->index, fr->num)) fi_add(offset); */
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#define FI_NEXT(fi, framenum) ((fi).size && framenum == (fi).next)
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/* Initialize stuff, set things to zero and NULL... */
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void fi_init(struct frame_index *fi);
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/* Deallocate/zero things. */
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void fi_exit(struct frame_index *fi);
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/* Prepare a given size, preserving current fill, if possible.
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If the new size is smaller than fill, the entry density is reduced.
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Return 0 on success. */
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int fi_resize(struct frame_index *fi, size_t newsize);
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/* Append a frame position, reducing index density if needed. */
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void fi_add(struct frame_index *fi, off_t pos);
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/* Replace the frame index */
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int fi_set(struct frame_index *fi, off_t *offsets, off_t step, size_t fill);
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/* Empty the index (setting fill=0 and step=1), but keep current size. */
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void fi_reset(struct frame_index *fi);
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#endif
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