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134 lines
3.6 KiB
C
134 lines
3.6 KiB
C
/*
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index: frame index data structure and functions
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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 "index.h"
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#include "debug.h"
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/* The next expected frame offset, one step ahead. */
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static off_t fi_next(struct frame_index *fi)
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{
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return (off_t)fi->fill*fi->step;
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}
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/* Shrink down the used index to the half.
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Be careful with size = 1 ... there's no shrinking possible there. */
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static void fi_shrink(struct frame_index *fi)
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{
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if(fi->fill < 2) return; /* Won't shrink below 1. */
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else
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{ /* Double the step, half the fill. Should work as well for fill%2 = 1 */
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size_t c;
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debug2("shrink index with fill %lu and step %lu", (unsigned long)fi->fill, (unsigned long)fi->step);
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fi->step *= 2;
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fi->fill /= 2;
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/* Move the data down. */
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for(c = 0; c < fi->fill; ++c)
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fi->data[c] = fi->data[2*c];
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}
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fi->next = fi_next(fi);
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}
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void fi_init(struct frame_index *fi)
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{
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fi->data = NULL;
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fi->step = 1;
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fi->fill = 0;
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fi->size = 0;
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fi->grow_size = 0;
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fi->next = fi_next(fi);
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}
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void fi_exit(struct frame_index *fi)
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{
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debug2("fi_exit: %p and %lu", (void*)fi->data, (unsigned long)fi->size);
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if(fi->size && fi->data != NULL) free(fi->data);
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fi_init(fi); /* Be prepared for further fun, still. */
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}
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int fi_resize(struct frame_index *fi, size_t newsize)
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{
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off_t *newdata = NULL;
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if(newsize == fi->size) return 0;
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if(newsize > 0 && newsize < fi->size)
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{ /* When we reduce buffer size a bit, shrink stuff. */
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while(fi->fill > newsize){ fi_shrink(fi); }
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}
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newdata = safe_realloc(fi->data, newsize*sizeof(off_t));
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if(newsize == 0 || newdata != NULL)
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{
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fi->data = newdata;
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fi->size = newsize;
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if(fi->fill > fi->size) fi->fill = fi->size;
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fi->next = fi_next(fi);
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debug2("new index of size %lu at %p", (unsigned long)fi->size, (void*)fi->data);
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return 0;
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}
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else
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{
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error("failed to resize index!");
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return -1;
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}
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}
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void fi_add(struct frame_index *fi, off_t pos)
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{
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debug3("wanting to add to fill %lu, step %lu, size %lu", (unsigned long)fi->fill, (unsigned long)fi->step, (unsigned long)fi->size);
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if(fi->fill == fi->size)
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{ /* Index is full, we need to shrink... or grow. */
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/* Store the current frame number to check later if we still want it. */
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off_t framenum = fi->fill*fi->step;
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/* If we want not / cannot grow, we shrink. */
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if( !(fi->grow_size && fi_resize(fi, fi->size+fi->grow_size)==0) )
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fi_shrink(fi);
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/* Now check if we still want to add this frame (could be that not, because of changed step). */
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if(fi->next != framenum) return;
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}
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/* When we are here, we want that frame. */
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if(fi->fill < fi->size) /* safeguard for size=1, or just generally */
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{
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debug1("adding to index at %p", (void*)(fi->data+fi->fill));
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fi->data[fi->fill] = pos;
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++fi->fill;
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fi->next = fi_next(fi);
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debug3("added pos %li to index with fill %lu and step %lu", (long) pos, (unsigned long)fi->fill, (unsigned long)fi->step);
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}
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}
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int fi_set(struct frame_index *fi, off_t *offsets, off_t step, size_t fill)
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{
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if(fi_resize(fi, fill) == -1) return -1;
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fi->step = step;
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if(offsets != NULL)
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{
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memcpy(fi->data, offsets, fill*sizeof(off_t));
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fi->fill = fill;
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}
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else
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{
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/* allocation only, no entries in index yet */
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fi->fill = 0;
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}
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fi->next = fi_next(fi);
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debug3("set new index of fill %lu, size %lu at %p",
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(unsigned long)fi->fill, (unsigned long)fi->size, (void*)fi->data);
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return 0;
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}
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void fi_reset(struct frame_index *fi)
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{
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debug1("reset with size %"SIZE_P, (size_p)fi->size);
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fi->fill = 0;
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fi->step = 1;
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fi->next = fi_next(fi);
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}
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