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/* recycle.c */
/* Author:
* Steve Kirkendall
* 14407 SW Teal Blvd. #C
* Beaverton, OR 97005
* kirkenda@cs.pdx.edu
*/
/* This file contains the functions perform garbage collection and allocate
* reusable blocks.
*/
#include "config.h"
#include "vi.h"
#ifndef NO_RECYCLE
/* this whole file would have be skipped if NO_RECYCLE is defined */
extern long lseek();
#define BTST(bitno, byte) ((byte) & (1 << (bitno)))
#define BSET(bitno, byte) ((byte) |= (1 << (bitno)))
#define BCLR(bitno, byte) ((byte) &= ~(1 << (bitno)))
#define TST(blkno) ((blkno) < MAXBIT ? BTST((blkno) & 7, bitmap[(blkno) >> 3]) : 1)
#define SET(blkno) if ((blkno) < MAXBIT) BSET((blkno) & 7, bitmap[(blkno) >> 3])
#define CLR(blkno) if ((blkno) < MAXBIT) BCLR((blkno) & 7, bitmap[(blkno) >> 3])
/* bitmap of free blocks in first 4096k of tmp file */
static unsigned char bitmap[512];
#define MAXBIT (sizeof bitmap << 3)
/* this function locates all free blocks in the current tmp file */
void garbage()
{
int i;
BLK oldhdr;
/* start by assuming every block is free */
for (i = 0; i < sizeof bitmap; i++)
{
bitmap[i] = 255;
}
/* header block isn't free */
#ifndef lint
CLR(0);
#endif
/* blocks needed for current hdr aren't free */
for (i = 1; i < MAXBLKS; i++)
{
CLR(hdr.n[i]);
}
/* blocks needed for undo version aren't free */
lseek(tmpfd, 0L, 0);
if (read(tmpfd, &oldhdr, (unsigned)sizeof oldhdr) != sizeof oldhdr)
{
msg("garbage() failed to read oldhdr??");
for (i = 0; i < sizeof bitmap; i++)
{
bitmap[i] = 0;
}
return;
}
for (i = 1; i < MAXBLKS; i++)
{
CLR(oldhdr.n[i]);
}
/* blocks needed for cut buffers aren't free */
for (i = cutneeds(&oldhdr) - 1; i >= 0; i--)
{
CLR(oldhdr.n[i]);
}
}
/* This function allocates the first available block in the tmp file */
long allocate()
{
int i;
long offset;
/* search for the first byte with a free bit set */
for (i = 0; i < sizeof bitmap && bitmap[i] == 0; i++)
{
}
/* if we hit the end of the bitmap, return the end of the file */
if (i == sizeof bitmap)
{
offset = lseek(tmpfd, 0L, 2);
}
else /* compute the offset for the free block */
{
for (i <<= 3; TST(i) == 0; i++)
{
}
offset = (long)i * (long)BLKSIZE;
/* mark the block as "allocated" */
CLR(i);
}
return offset;
}
#endif
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