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1 #ifndef MPG123_H_INDEX
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2 #define MPG123_H_INDEX
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3
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4 /*
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5 index: frame index data structure and functions
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6
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7 This is for keeping track of frame positions for accurate seeking.
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8 Now in it's own file, with initial code from frame.c and parse.c .
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9
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10 The idea of the index with a certain amount of entries is to cover
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11 all yet-encountered frame positions with minimal coarseness.
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12 Meaning: At first every frame position is recorded, then, when
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13 the index is full, every second position is trown away to make
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14 space. Next time it is full, the same happens. And so on.
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15 In this manner we maintain a good resolution with the given
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16 maximum index size while covering the whole stream.
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17
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18 copyright 2007-8 by the mpg123 project - free software under the terms of the LGPL 2.1
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19 see COPYING and AUTHORS files in distribution or http://mpg123.org
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20 initially written by Thomas Orgis
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21 */
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22
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23 #include "config.h"
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24 #include "compat.h"
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25
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26 struct frame_index
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27 {
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28 off_t *data; /* actual data, the frame positions */
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29 off_t step; /* advancement in frame number per index point */
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30 off_t next; /* frame offset supposed to come next into the index */
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31 size_t size; /* total number of possible entries */
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32 size_t fill; /* number of used entries */
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33 size_t grow_size; /* if > 0: index allowed to grow on need with these steps, instead of lowering resolution */
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34 };
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35
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36 /* The condition for a framenum to be appended to the index.
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37 if(FI_NEXT(fr->index, fr->num)) fi_add(offset); */
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38 #define FI_NEXT(fi, framenum) ((fi).size && framenum == (fi).next)
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39
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40 /* Initialize stuff, set things to zero and NULL... */
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41 void fi_init(struct frame_index *fi);
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42 /* Deallocate/zero things. */
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43 void fi_exit(struct frame_index *fi);
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44
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45 /* Prepare a given size, preserving current fill, if possible.
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46 If the new size is smaller than fill, the entry density is reduced.
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47 Return 0 on success. */
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48 int fi_resize(struct frame_index *fi, size_t newsize);
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49
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50 /* Append a frame position, reducing index density if needed. */
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51 void fi_add(struct frame_index *fi, off_t pos);
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52
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53 /* Empty the index (setting fill=0 and step=1), but keep current size. */
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54 void fi_reset(struct frame_index *fi);
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55
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56 #endif
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