sortientry.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include "stdinc.h"
#include "dat.h"
#include "fns.h"

typedef struct IEBuck	IEBuck;
typedef struct IEBucks	IEBucks;

enum
{
	ClumpChunks	= 32*1024
};

struct IEBuck
{
	u32int	head;		/* head of chain of chunks on the disk */
	u32int	used;		/* usage of the last chunk */
	u64int	total;		/* total number of bytes in this bucket */
	u8int	*buf;		/* chunk of entries for this bucket */
};

struct IEBucks
{
	Part	*part;
	u64int	off;		/* offset for writing data in the partition */
	u32int	chunks;		/* total chunks written to fd */
	u64int	max;		/* max bytes entered in any one bucket */
	int	bits;		/* number of bits in initial bucket sort */
	int	nbucks;		/* 1 << bits, the number of buckets */
	u32int	size;		/* bytes in each of the buckets chunks */
	u32int	usable;		/* amount usable for IEntry data */
	u8int	*buf;		/* buffer for all chunks */
	IEBuck	*bucks;
};

#define	U32GET(p)	(((p)[0]<<24)|((p)[1]<<16)|((p)[2]<<8)|(p)[3])
#define	U32PUT(p,v)	(p)[0]=(v)>>24;(p)[1]=(v)>>16;(p)[2]=(v)>>8;(p)[3]=(v)

static IEBucks	*initIEBucks(Part *part, int bits, u32int size);
static int	flushIEBuck(IEBucks *ib, int b, int reset);
static int	flushIEBucks(IEBucks *ib);
static u32int	sortIEBuck(IEBucks *ib, int b);
static u64int	sortIEBucks(IEBucks *ib);
static int	sprayIEntry(IEBucks *ib, IEntry *ie);
static u32int	readArenaInfo(IEBucks *ib, Arena *arena, u64int a);
static u32int	readIEBuck(IEBucks *ib, int b);
static void	freeIEBucks(IEBucks *ib);

/*
 * build a sorted file with all Ientries which should be in ix.
 * assumes the arenas' directories are up to date.
 * reads each, converts the entries to index entries,
 * and sorts them.
 */
u64int
sortRawIEntries(Index *ix, Part *tmp, u64int *base)
{
	IEBucks *ib;
	u64int clumps, sorted;
	u32int n;
	int i, ok;

//ZZZ should allow configuration of bits, bucket size
	ib = initIEBucks(tmp, 8, 64*1024);
	if(ib == nil){
		setErr(EOk, "can't create sorting buckets: %R");
		return TWID64;
	}
	ok = 1;
	clumps = 0;
	for(i = 0; i < ix->narenas; i++){
		n = readArenaInfo(ib, ix->arenas[i], ix->amap[i].start);
		if(n == TWID32){
			ok = 0;
			break;
		}
		clumps += n;
	}
	if(ok){
fprint(2, "got %lld clumps - starting sort\n", clumps);
		sorted = sortIEBucks(ib);
		*base = (u64int)ib->chunks * ib->size;
		if(sorted != clumps){
			fprint(2, "sorting messed up: clumps=%lld sorted=%lld\n", clumps, sorted);
			ok = 0;
		}
	}
	freeIEBucks(ib);
	if(!ok)
		return TWID64;
	return clumps;
}

/*
 * read in all of the arena's clump directory,
 * convert to IEntry format, and bucket sort based
 * on the first few bits.
 */
static u32int
readArenaInfo(IEBucks *ib, Arena *arena, u64int a)
{
	IEntry ie;
	ClumpInfo *ci, *cis;
	u32int clump;
	int i, n, ok;

//ZZZ remove fprint?
	if(arena->clumps)
		fprint(2, "reading directory for arena=%s with %d entries\n", arena->name, arena->clumps);

	cis = MKN(ClumpInfo, ClumpChunks);
	ok = 1;
	memset(&ie, 0, sizeof(IEntry));
	for(clump = 0; clump < arena->clumps && ok; clump += n){
		n = ClumpChunks;
		if(n > arena->clumps - clump)
			n = arena->clumps - clump;
		if(readClumpInfos(arena, clump, cis, n) != n){
			setErr(EOk, "arena directory read failed: %R");
			ok = 0;
			break;
		}

		for(i = 0; i < n; i++){
			ci = &cis[i];
			ie.ia.type = ci->type;
			ie.ia.size = ci->uncsize;
			ie.ia.addr = a;
			a += ci->size + ClumpSize;
			ie.ia.blocks = (ci->size + ClumpSize + (1 << ABlockLog) - 1) >> ABlockLog;
			scoreCp(ie.score, ci->score);
			if(!sprayIEntry(ib, &ie)){
				setErr(EOk, "can't put entry into bucket: %R");
				ok = 0;
				break;
			}
		}
	}
	free(cis);
	if(!ok)
		return TWID32;
	return clump;
}

/*
 * initialize the external bucket sorting data structures
 */
static IEBucks*
initIEBucks(Part *part, int bits, u32int size)
{
	IEBucks *ib;
	int i;

	ib = MKZ(IEBucks);
	if(ib == nil){
		setErr(EOk, "out of memory");
		return nil;
	}
	ib->bits = bits;
	ib->nbucks = 1 << bits;
	ib->size = size;
	ib->usable = (size - U32Size) / IEntrySize * IEntrySize;
	ib->bucks = MKNZ(IEBuck, ib->nbucks);
	if(ib->bucks == nil){
		setErr(EOk, "out of memory allocation sorting buckets");
		freeIEBucks(ib);
		return nil;
	}
	ib->buf = MKN(u8int, size * (1 << bits));
	if(ib->buf == nil){
		setErr(EOk, "out of memory allocating sorting buckets' buffers");
		freeIEBucks(ib);
		return nil;
	}
	for(i = 0; i < ib->nbucks; i++){
		ib->bucks[i].head = TWID32;
		ib->bucks[i].buf = &ib->buf[i * size];
	}
	ib->part = part;
	return ib;
}

static void
freeIEBucks(IEBucks *ib)
{
	if(ib == nil)
		return;
	free(ib->bucks);
	free(ib->buf);
	free(ib);
}

/*
 * initial sort: put the entry into the correct bucket
 */
static int
sprayIEntry(IEBucks *ib, IEntry *ie)
{
	u32int n;
	int b;

	b = hashBits(ie->score, ib->bits);
	n = ib->bucks[b].used;
	packIEntry(ie, &ib->bucks[b].buf[n]);
	n += IEntrySize;
	ib->bucks[b].used = n;
	if(n + IEntrySize <= ib->usable)
		return 1;
	return flushIEBuck(ib, b, 1);
}

/*
 * finish sorting:
 * for each bucket, read it in and sort it
 * write out the the final file
 */
static u64int
sortIEBucks(IEBucks *ib)
{
	u64int tot;
	u32int n;
	int i;

	if(!flushIEBucks(ib))
		return TWID64;
	for(i = 0; i < ib->nbucks; i++)
		ib->bucks[i].buf = nil;
	ib->off = (u64int)ib->chunks * ib->size;
	free(ib->buf);
fprint(2, "ib->max = %lld\n", ib->max);
fprint(2, "ib->chunks = %ud\n", ib->chunks);
	ib->buf = MKN(u8int, ib->max + U32Size);
	if(ib->buf == nil){
		setErr(EOk, "out of memory allocating final sorting buffer; try more buckets");
		return TWID64;
	}
	tot = 0;
	for(i = 0; i < ib->nbucks; i++){
		n = sortIEBuck(ib, i);
		if(n == TWID32)
			return TWID64;
		tot += n;
	}
	return tot;
}

/*
 * sort from bucket b of ib into the output file to
 */
static u32int
sortIEBuck(IEBucks *ib, int b)
{
	u32int n;

	n = readIEBuck(ib, b);
	if(n == TWID32)
		return TWID32;
	qsort(ib->buf, n, IEntrySize, ientryCmp);
	if(!writePart(ib->part, ib->off, ib->buf, n * IEntrySize)){
		setErr(EOk, "can't write sorted bucket: %R");
		return TWID32;
	}
	ib->off += n * IEntrySize;
	return n;
}

/*
 * write out a single bucket
 */
static int
flushIEBuck(IEBucks *ib, int b, int reset)
{
	u32int n;

	if(ib->bucks[b].used == 0)
		return 1;
	n = ib->bucks[b].used;
	U32PUT(&ib->bucks[b].buf[n], ib->bucks[b].head);
	n += U32Size;
	if(!writePart(ib->part, (u64int)ib->chunks * ib->size, ib->bucks[b].buf, n)){
		setErr(EOk, "can't write sorting bucket to file: %R");
		return 0;
	}
	ib->bucks[b].head = ib->chunks++;
	ib->bucks[b].total += ib->bucks[b].used;
	if(reset)
		ib->bucks[b].used = 0;
	return 1;
}

/*
 * write out all of the buckets, and compute
 * the maximum size of any bucket
 */
static int
flushIEBucks(IEBucks *ib)
{
	int i;

	for(i = 0; i < ib->nbucks; i++){
		if(!flushIEBuck(ib, i, 0))
			return 0;
		if(ib->bucks[i].total > ib->max)
			ib->max = ib->bucks[i].total;
	}
	return 1;
}

/*
 * read in the chained buffers for bucket b,
 * and return it's total number of IEntries
 */
static u32int
readIEBuck(IEBucks *ib, int b)
{
	u32int head, n, m;

	head = ib->bucks[b].head;
	n = 0;
	m = ib->bucks[b].used;
	if(m == 0)
		m = ib->usable;
fprint(2, "%d total = %lld\n", b, ib->bucks[b].total);
	while(head != TWID32){
		if(!readPart(ib->part, (u64int)head * ib->size, &ib->buf[n], m + U32Size)){
fprint(2, "n = %ud\n", n);
			setErr(EOk, "can't read index sort bucket: %R");
			return TWID32;
		}
		n += m;
		head = U32GET(&ib->buf[n]);
		m = ib->usable;
	}
fprint(2, "n = %ud\n", n);
	return n / IEntrySize;
}