109 lines
2.2 KiB
C
109 lines
2.2 KiB
C
/* recycle.c */
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/* Author:
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* Steve Kirkendall
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* 16820 SW Tallac Way
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* Beaverton, OR 97006
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* kirkenda@jove.cs.pdx.edu, or ...uunet!tektronix!psueea!jove!kirkenda
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*/
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/* This file contains the functions perform garbage collection and allocate
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* reusable blocks.
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*/
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#include "vi.h"
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#ifndef NO_RECYCLE
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/* this whole file would have be skipped if NO_RECYCLE is defined */
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extern long lseek();
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#define BTST(bitno, byte) ((byte) & (1 << (bitno)))
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#define BSET(bitno, byte) ((byte) |= (1 << (bitno)))
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#define BCLR(bitno, byte) ((byte) &= ~(1 << (bitno)))
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#define TST(blkno) ((blkno) < MAXBIT ? BTST((blkno) & 7, bitmap[(blkno) >> 3]) : 1)
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#define SET(blkno) if ((blkno) < MAXBIT) BSET((blkno) & 7, bitmap[(blkno) >> 3])
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#define CLR(blkno) if ((blkno) < MAXBIT) BCLR((blkno) & 7, bitmap[(blkno) >> 3])
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/* bitmap of free blocks in first 4096k of tmp file */
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static unsigned char bitmap[512];
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#define MAXBIT (sizeof bitmap << 3)
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/* this function locates all free blocks in the current tmp file */
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garbage()
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{
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int i;
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BLK oldhdr;
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/* start by assuming every block is free */
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for (i = 0; i < sizeof bitmap; i++)
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{
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bitmap[i] = 255;
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}
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/* header block isn't free */
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CLR(0);
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/* blocks needed for current hdr aren't free */
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for (i = 1; i < MAXBLKS; i++)
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{
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CLR(hdr.n[i]);
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}
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/* blocks needed for undo version aren't free */
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lseek(tmpfd, 0L, 0);
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if (read(tmpfd, &oldhdr, sizeof oldhdr) != sizeof oldhdr)
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{
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msg("garbage() failed to read oldhdr??");
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for (i = 0; i < sizeof bitmap; i++)
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{
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bitmap[i] = 0;
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}
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return;
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}
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for (i = 1; i < MAXBLKS; i++)
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{
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CLR(oldhdr.n[i]);
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}
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/* blocks needed for cut buffers aren't free */
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for (i = cutneeds(&oldhdr) - 1; i >= 0; i--)
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{
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CLR(oldhdr.n[i]);
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}
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}
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/* This function allocates the first available block in the tmp file */
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long allocate()
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{
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int i;
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long offset;
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/* search for the first byte with a free bit set */
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for (i = 0; i < sizeof bitmap && bitmap[i] == 0; i++)
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{
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}
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/* if we hit the end of the bitmap, return the end of the file */
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if (i == sizeof bitmap)
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{
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offset = lseek(tmpfd, 0L, 2);
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}
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else /* compute the offset for the free block */
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{
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for (i <<= 3; TST(i) == 0; i++)
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{
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}
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offset = (long)i * (long)BLKSIZE;
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/* mark the block as "allocated" */
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CLR(i);
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}
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return offset;
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}
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#endif
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