haiku/src/servers/app/BGet++.cpp

/*
 * Copyright 2001-2005, Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		John Walker <kelvin@fourmilab.ch>
 *		DarkWyrm <bpmagic@columbus.rr.com>
 *		Stephan Aßmus <superstippi@gmx.de>
 *
 *	BGET pool allocator
 */

/*
	This class is based on the BGET pool allocator. Original code was in standard
	ANSI C with a bunch of static variables. The original code was placed into the
	MemPool class and the original allocation, release, and compacting functions
	were made into virtual members. MemPool also, unlike the original code, makes 
	use of malloc() and free() to handle dynamic memory needs. AreaPool is a MemPool
	subclass which uses areas to handle memory management needs in large chunks.
*/


// Buffer allocation size quantum: all buffers allocated are a multiple of this size.  '
// This MUST be a power of two.
#define SizeQuant   4

#include <stdio.h>
#include <OS.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

//  Declare the interface, including the requested buffer size type, ssize_t.
#include "BGet++.h"

// some handy short cuts
#define BH(p)	((bhead*) (p))
#define BDH(p)	((bdhead*) (p))
#define BFH(p)	((bfhead*) (p))

//  Minimum allocation quantum:
#define QLSize	(sizeof(struct qlinks))
#define SizeQ	((SizeQuant > QLSize) ? SizeQuant : QLSize)

// End sentinel: value placed in bsize field of dummy block delimiting end of
// pool block. The most negative number which will fit in a ssize_t, 
// defined in a way that the compiler will accept.
#define ESent	((ssize_t) (-(((1L << (sizeof(ssize_t) * 8 - 2)) - 1) * 2) - 2))


MemPool::MemPool()
	: fTotalAlloced(0),
 	  fGetCount(0),
 	  fReleaseCount(0),
 	  fNumpblk(0),
 	  fNumpget(0),
 	  fNumprel(0),
 	  fNumdget(0),
 	  fNumdrel(0),
 	  fExpIncr(0),
 	  fPoolLength(0)
{
	fFreeList.bh = (bhead){ 0, 0 };
	fFreeList.ql = (qlinks){ &fFreeList, &fFreeList };
}


MemPool::~MemPool()
{
}

//  Allocate a buffer from the available space in the memory pool
void*
MemPool::GetBuffer(ssize_t requested_size, bool zero)
{
    ssize_t size = requested_size;
    void *buf;

	int compactseq = 0;

    assert(size > 0);

    if (size < (ssize_t)SizeQ)
    {
    	// Need at least room for the queue links.
		size = SizeQ;
    }

#if SizeQuant > 1
    size = (size + (SizeQuant - 1)) & (~(SizeQuant - 1));
#endif
	
	// Add overhead in allocated buffer to size required.
    size += sizeof(struct bhead);     

    bfhead *b;
    bfhead *best;
    // If a compact function was provided in the call to bectl(), wrap
    // a loop around the allocation process  to  allow	compaction  to
    // intervene in case we don't find a suitable buffer in the chain.
    while (1) 
    {
		b = fFreeList.ql.flink;
		best = &fFreeList;
	
	
		// Scan the free list searching for the first buffer big enough
		// to hold the requested size buffer.
	
		while (b != &fFreeList) 
		{
		    if (b->bh.bsize >= size) 
		    {
				if ((best == &fFreeList) || (b->bh.bsize < best->bh.bsize)) 
				{
				    best = b;
				}
		    }
		    
		    b = b->ql.flink;		  // Link to next buffer
		}
		b = best;
		
		while (b != &fFreeList) 
		{
		    if ((ssize_t) b->bh.bsize >= size) 
		    {
	
				// Buffer is big enough to satisfy the request. Allocate it to the caller.  
				// We must decide whether the buffer is large enough to split into the part 
				// given to the caller and a free buffer that remains on the free list, or
				// whether the entire buffer should be removed from the free list and given 
				// to the caller in its entirety. We only split the buffer if enough room 
				// remains for a header plus the minimum quantum of allocation.
		
				if ((b->bh.bsize - size) > (ssize_t)(SizeQ + (sizeof(struct bhead)))) 
				{
				    struct bhead *ba, *bn;
		
				    ba = BH(((char *) b) + (b->bh.bsize - size));
				    bn = BH(((char *) ba) + size);
				    assert(bn->prevfree == b->bh.bsize);
				    
				    // Subtract size from length of free block.
				    b->bh.bsize -= size;
				    
				    // Link allocated buffer to the previous free buffer.
				    ba->prevfree = b->bh.bsize;
				    
				    // Plug negative size into user buffer.
				    ba->bsize = -(ssize_t) size;
				    
				    // Mark buffer after this one not preceded by free block.
				    bn->prevfree = 0;
		
				    fTotalAlloced += size;
				    fGetCount++;		  // Increment number of GetBuffer() calls
					
				    buf = (void *) ((((char *) ba) + sizeof(struct bhead)));
				    return buf;
				}
				else
				{
				    struct bhead *ba;
		
				    ba = BH(((char *) b) + b->bh.bsize);
				    assert(ba->prevfree == b->bh.bsize);
		
					// The buffer isn't big enough to split.  Give  the  whole
					// shebang to the caller and remove it from the free list.
		
				    assert(b->ql.blink->ql.flink == b);
				    assert(b->ql.flink->ql.blink == b);
				    b->ql.blink->ql.flink = b->ql.flink;
				    b->ql.flink->ql.blink = b->ql.blink;
		
				    fTotalAlloced += b->bh.bsize;
				    fGetCount++;		  // Increment number of GetBuffer() calls
					
				    // Negate size to mark buffer allocated.
				    b->bh.bsize = -(b->bh.bsize);
		
				    // Zero the back pointer in the next buffer in memory
				    // to indicate that this buffer is allocated.
				    ba->prevfree = 0;
		
				    // Give user buffer starting at queue links.
				    buf =  (void *) &(b->ql);
				    return buf;
				}
		    }
		    b = b->ql.flink;		  // Link to next buffer
		}
		
	
		// We failed to find a buffer.  If there's a compact  function
		// defined,  notify  it  of the size requested.  If it returns
		// TRUE, try the allocation again.
	
		if(!CompactMem(size, ++compactseq))
		    break;
    }

    // No buffer available with requested size free.

    // Don't give up yet -- look in the reserve supply.
	if (size > (ssize_t)(fExpIncr - sizeof(struct bhead))) 
	{
	    // Request	is  too  large	to  fit in a single expansion
	    // block.  Try to satisy it by a direct buffer acquisition.
	    struct bdhead *bdh;

	    size += sizeof(struct bdhead) - sizeof(struct bhead);
	    if ((bdh = BDH(AcquireMem((ssize_t) size))) != NULL) 
	    {
			//  Mark the buffer special by setting the size field
			//  of its header to zero.
			bdh->bh.bsize = 0;
			bdh->bh.prevfree = 0;
			bdh->tsize = size;
	
			fTotalAlloced += size;
			
			// Increment number of GetBuffer() calls
			fGetCount++;
			
			// Direct GetBuffer() call count
			fNumdget++;
	
			buf =  (void *) (bdh + 1);
			return buf;
	    }

	}
	else
	{

	    //	Try to obtain a new expansion block
	    void *newpool;

	    if ((newpool = AcquireMem((ssize_t) fExpIncr)) != NULL) 
	    {
			AddToPool(newpool, fExpIncr);
			
			// This can't, I say, can't get into a loop
            buf =  GetBuffer(requested_size);

			return buf;
	    }
	}

    //	Still no buffer available
    return NULL;

	// Code from bgetz -- zeroing code
/*
	char *buf = (char *) GetBuffer(size);

    if (buf != NULL) 
    {
	   	struct bhead *b;
		ssize_t rsize;
	
		b = BH(buf - sizeof(struct bhead));
		rsize = -(b->bsize);
		
		if (rsize == 0) 
		{
		    struct bdhead *bd;
		
		    bd = BDH(buf - sizeof(struct bdhead));
		    rsize = bd->tsize - sizeof(struct bdhead);
		}
		else 
		{
		    rsize -= sizeof(struct bhead);
		}
		
		assert(rsize >= size);
		memset(buf, 0, (MemSize) rsize);
    }
    return ((void *) buf);
*/

}

// Reallocate a buffer.  This is a minimal implementation, simply in terms 
// of ReleaseBuffer()  and  GetBuffer(). It could be enhanced to allow the 
// buffer to grow into adjacent free blocks and to avoid moving data unnecessarily.
void*
MemPool::ReallocateBuffer(void *buf, ssize_t size)
{
    void *nbuf;
    
    // Old size of buffer
    ssize_t osize;
    struct bhead *b;

    if ((nbuf = GetBuffer(size)) == NULL)
    {
    	// Acquire new buffer
		return NULL;
    }
    
    if (buf == NULL) 
    {
		return nbuf;
    }
    b = BH(((char *) buf) - sizeof(struct bhead));
    osize = -b->bsize;

    if (osize == 0) 
    {
		//  Buffer acquired directly through acqfcn.
		struct bdhead *bd;
	
		bd = BDH(((char *) buf) - sizeof(struct bdhead));
		osize = bd->tsize - sizeof(struct bdhead);
    }
    else
		osize -= sizeof(struct bhead);
    assert(osize > 0);
    
    // Copy the data
    memcpy((char *) nbuf, (char *) buf, (int) ((size < osize) ? size : osize));
    ReleaseBuffer(buf);
    return nbuf;
}

//  BREL  --  Release a buffer. 
void
MemPool::ReleaseBuffer(void *buf)
{
	struct bfhead *b, *bn;

    b = BFH(((char *) buf) - sizeof(struct bhead));
	
	// Increment number of ReleaseBuffer() calls
    fReleaseCount++;

    assert(buf != NULL);
	
	// Directly-acquired buffer?
    if (b->bh.bsize == 0)
    {
		struct bdhead *bdh;
	
		bdh = BDH(((char *) buf) - sizeof(struct bdhead));
		assert(b->bh.prevfree == 0);
	
		fTotalAlloced -= bdh->tsize;
		assert(fTotalAlloced >= 0);
		
		// Number of direct releases
		fNumdrel++;
	
		memset((char *) buf, 0x55, (int) (bdh->tsize - sizeof(struct bdhead)));
	
		// Release it directly.
		ReleaseMem((void *) bdh);
		return;
    }


    // Buffer size must be negative, indicating that the buffer is allocated.
    if (b->bh.bsize >= 0) 
    {
		bn = NULL;
    }
    assert(b->bh.bsize < 0);

    //	Back pointer in next buffer must be zero, indicating the same thing:
    assert(BH((char *) b - b->bh.bsize)->prevfree == 0);

    fTotalAlloced += b->bh.bsize;
    assert(fTotalAlloced >= 0);


    // If the back link is nonzero, the previous buffer is free. 

    if (b->bh.prevfree != 0) 
    {
		// The previous buffer is free.  Consolidate this buffer  with	it
		// by  adding  the  length  of	this  buffer  to the previous free
		// buffer.  Note that we subtract the size  in	the  buffer  being
		// released,  since  it's  negative to indicate that the buffer is allocated.
	
		register ssize_t size = b->bh.bsize;
	
	    // Make the previous buffer the one we're working on.
		assert(BH((char *) b - b->bh.prevfree)->bsize == b->bh.prevfree);
		b = BFH(((char *) b) - b->bh.prevfree);
		b->bh.bsize -= size;
    }
    else 
    {
		// The previous buffer isn't allocated.  Insert this buffer on the 
		// free list as an isolated free block.
		assert(fFreeList.ql.blink->ql.flink == &fFreeList);
		assert(fFreeList.ql.flink->ql.blink == &fFreeList);
		b->ql.flink = &fFreeList;
		b->ql.blink = fFreeList.ql.blink;
		fFreeList.ql.blink = b;
		b->ql.blink->ql.flink = b;
		b->bh.bsize = -b->bh.bsize;
    }

	// Now we look at the next buffer in memory, located by advancing from
	// the  start  of  this  buffer  by its size, to see if that buffer is
	// free.  If it is, we combine  this  buffer  with	the  next  one	in
	// memory, dechaining the second buffer from the free list.

    bn =  BFH(((char *) b) + b->bh.bsize);
    if (bn->bh.bsize > 0) 
    {
		// The buffer is free.	Remove it from the free list and add
		// its size to that of our buffer.
		assert(BH((char *) bn + bn->bh.bsize)->prevfree == bn->bh.bsize);
		assert(bn->ql.blink->ql.flink == bn);
		assert(bn->ql.flink->ql.blink == bn);
		bn->ql.blink->ql.flink = bn->ql.flink;
		bn->ql.flink->ql.blink = bn->ql.blink;
		b->bh.bsize += bn->bh.bsize;
	
		// Finally,  advance  to   the	buffer	that   follows	the  newly
		// consolidated free block.  We must set its  backpointer  to  the
		// head  of  the  consolidated free block.  We know the next block
		// must be an allocated block because the process of recombination
		// guarantees  that  two  free	blocks will never be contiguous in
		// memory.
		bn = BFH(((char *) b) + b->bh.bsize);
    }

    memset(((char *) b) + sizeof(struct bfhead), 0x55,(int) (b->bh.bsize - sizeof(struct bfhead)));

    assert(bn->bh.bsize < 0);

    // The next buffer is allocated.  Set the backpointer in it  to  point
    // to this buffer; the previous free buffer in memory.
    bn->bh.prevfree = b->bh.bsize;

	// If a block-release function is defined, and this free buffer
	// constitutes the entire block, release it.  Note that  fPoolLength
	// is  defined  in  such a way that the test will fail unless all
	// pool blocks are the same size.

    if (((ssize_t) b->bh.bsize) == (ssize_t)(fPoolLength - sizeof(struct bhead))) 
	{
		assert(b->bh.prevfree == 0);
		assert(BH((char *) b + b->bh.bsize)->bsize == ESent);
		assert(BH((char *) b + b->bh.bsize)->prevfree == b->bh.bsize);
		
		//  Unlink the buffer from the free list 
		b->ql.blink->ql.flink = b->ql.flink;
		b->ql.flink->ql.blink = b->ql.blink;
	
		ReleaseMem(b);
		
		// Nr of expansion block releases
		fNumprel++;
		
		// Total number of blocks
		fNumpblk--;
		assert(fNumpblk == fNumpget - fNumprel);
    }
}

// Add a region of memory to the buffer pool.
void
MemPool::AddToPool(void *buffer, ssize_t length)
{
	if (buffer == NULL || length <= 0)
		return;

	length &= ~(SizeQuant - 1);

	if (fPoolLength == 0) 
		fPoolLength = length;
	else if (length != fPoolLength)
		fPoolLength = -1;

	// Number of block acquisitions
	fNumpget++;

	// Number of blocks total
	fNumpblk++;
	assert(fNumpblk == fNumpget - fNumprel);

	// Since the block is initially occupied by a single free  buffer,
	// it  had	better	not  be  (much) larger than the largest buffer
	// whose size we can store in bhead.bsize.
	assert(length - sizeof(struct bhead) <= -((ssize_t) ESent + 1));

	struct bfhead *b = BFH(buffer);

	// Clear  the  backpointer at  the start of the block to indicate that
	// there  is  no  free  block  prior  to  this   one.    That   blocks
	// recombination when the first block in memory is released.
	b->bh.prevfree = 0;

	// Chain the new block to the free list.
	assert(fFreeList.ql.blink->ql.flink == &fFreeList);
	assert(fFreeList.ql.flink->ql.blink == &fFreeList);
	b->ql.flink = &fFreeList;
	b->ql.blink = fFreeList.ql.blink;
	fFreeList.ql.blink = b;
	b->ql.blink->ql.flink = b;

	// Create a dummy allocated buffer at the end of the pool.	This dummy
	// buffer is seen when a buffer at the end of the pool is released and
	// blocks  recombination  of  the last buffer with the dummy buffer at
	// the end.  The length in the dummy buffer  is  set  to  the  largest
	// negative  number  to  denote  the  end  of  the pool for diagnostic
	// routines (this specific value is  not  counted  on  by  the  actual
	// allocation and release functions).

	length -= sizeof(struct bhead);
	b->bh.bsize = length;

	memset(((char *)b) + sizeof(struct bfhead), 0x55, (int)(length - sizeof(struct bfhead)));

	struct bhead *bn = BH(((char *) b) + length);
	bn->prevfree = length;

    // Definition of ESent assumes two's complement!
    assert((~0) == -1);
    bn->bsize = ESent;
}


// Return buffer allocation free space statistics. 
void
MemPool::Stats(ssize_t *curalloc, ssize_t *totfree, ssize_t *maxfree,
			   long *nget, long *nrel)
{
    struct bfhead *b = fFreeList.ql.flink;

    *nget = fGetCount;
    *nrel = fReleaseCount;
    *curalloc = fTotalAlloced;
    *totfree = 0;
    *maxfree = -1;
    while (b != &fFreeList) 
    {
		assert(b->bh.bsize > 0);
		*totfree += b->bh.bsize;
		if (b->bh.bsize > *maxfree) 
		{
		    *maxfree = b->bh.bsize;
		}
		
		// Link to next buffer
		b = b->ql.flink;
    }
}


// Return extended statistics 
void
MemPool::ExtendedStats(ssize_t *pool_incr, long *npool, long *npget, long *nprel, 
					   long *ndget, long *ndrel)
{
    *pool_incr = (fPoolLength < 0) ? -fExpIncr : fExpIncr;
    *npool = fNumpblk;
    *npget = fNumpget;
    *nprel = fNumprel;
    *ndget = fNumdget;
    *ndrel = fNumdrel;
}


// Dump the data in a buffer. This is called with the user data pointer, 
// and backs up to the buffer header.  It will dump either a free block 
// or an allocated one.
void
MemPool::BufferDump(void *buf)
{
    struct bfhead *b;
    unsigned char *bdump;
    ssize_t bdlen;

    b = BFH(((char *) buf) - sizeof(struct bhead));
    assert(b->bh.bsize != 0);
    if (b->bh.bsize < 0) 
    {
		bdump = (unsigned char *) buf;
		bdlen = (-b->bh.bsize) - sizeof(struct bhead);
    }
    else
    {
		bdump = (unsigned char *) (((char *) b) + sizeof(struct bfhead));
		bdlen = b->bh.bsize - sizeof(struct bfhead);
    }

    while (bdlen > 0) 
    {
		int i, dupes = 0;
		ssize_t l = bdlen;
		char bhex[50], bascii[20];
	
		if (l > 16) 
		{
		    l = 16;
		}
	
		for (i = 0; i < l; i++) 
		{
	        sprintf(bhex + i * 3, "%02X ", bdump[i]);
	        bascii[i] = isprint(bdump[i]) ? bdump[i] : ' ';
		}
		bascii[i] = 0;
	        printf("%-48s   %s\n", bhex, bascii);
		bdump += l;
		bdlen -= l;
		while ((bdlen > 16) && (memcmp((char *) (bdump - 16),(char *) bdump, 16) == 0)) 
		{
		    dupes++;
		    bdump += 16;
		    bdlen -= 16;
		}

		if (dupes > 1) 
		{
		    printf("     (%d lines [%d bytes] identical to above line skipped)\n",
						dupes, dupes * 16);
		}
		else
		{
			if (dupes == 1) 
			{
			    bdump -= 16;
			    bdlen += 16;
			}
	    }
    }
}

// Dump a buffer pool. The buffer headers are always listed. If DUMPALLOC is 
// nonzero, the contents of allocated buffers are  dumped. If DUMPFREE is 
// nonzero,  free blocks are dumped as well. If FreeWipe checking is enabled,
// free blocks which have been clobbered will always be dumped.
void
MemPool::PoolDump(void *buf, bool dumpalloc, bool dumpfree)
{
    struct bfhead *b = BFH(buf);

    while (b->bh.bsize != ESent) 
    {
		ssize_t bs = b->bh.bsize;
	
		if (bs < 0) 
		{
		    bs = -bs;
	            printf("Allocated buffer: size %6ld bytes.\n", (long) bs);
		    if (dumpalloc) 
		    {
				BufferDump((void *) (((char *) b) + sizeof(struct bhead)));
		    }
		} 
		else 
		{
			char *lerr = "";

		    assert(bs > 0);
		    if ((b->ql.blink->ql.flink != b) ||	(b->ql.flink->ql.blink != b)) 
			{
	                lerr = "  (Bad free list links)";
		    }
	            printf("Free block:       size %6ld bytes.%s\n",
			(long) bs, lerr);
	
		    lerr = ((char *) b) + sizeof(struct bfhead);
		    if ((bs > (ssize_t)sizeof(struct bfhead)) && ((*lerr != 0x55) ||
				(memcmp(lerr, lerr + 1, (int) (bs - (sizeof(struct bfhead) + 1))) != 0))) 
			{
				printf("(Contents of above free block have been overstored.)\n");
				BufferDump((void *) (((char *) b) + sizeof(struct bhead)));
		    } 
		    else
			{
			    if (dumpfree) 
			    {
					BufferDump((void *) (((char *) b) + sizeof(struct bhead)));
			    }
			 }
		}
		b = BFH(((char *) b) + bs);
    }
}

// Validate a buffer pool.
int
MemPool::Validate(void *buf)
{
    struct bfhead *b = BFH(buf);

    while (b->bh.bsize != ESent) 
    {
		ssize_t bs = b->bh.bsize;

		if (bs < 0) 
		{
		    bs = -bs;
		}
		else 
		{
            char *lerr = "";
	
		    assert(bs > 0);
		    if (bs <= 0) 
		    {
				return 0;
		    }
		    
		    if ((b->ql.blink->ql.flink != b) || (b->ql.flink->ql.blink != b)) 
		    {
	                printf("Free block: size %6ld bytes.  (Bad free list links)\n",
					     (long) bs);
				assert(0);
				return 0;
		    }
	
		    lerr = ((char *) b) + sizeof(struct bfhead);
		    if ((bs > (ssize_t)sizeof(struct bfhead)) && ((*lerr != 0x55) ||
					(memcmp(lerr, lerr + 1,(int) (bs - (sizeof(struct bfhead) + 1))) != 0))) 
			{
				printf("(Contents of above free block have been overstored.)\n");
				BufferDump((void *) (((char *) b) + sizeof(struct bhead)));
				assert(0);
				return 0;
		    }
	
		}
		b = BFH(((char *) b) + bs);
    }
    return 1;
}


int*
MemPool::CompactMem(ssize_t sizereq, int sequence)
{
	return NULL;
}


void*
MemPool::AcquireMem(ssize_t size)
{
	return malloc(size);
}


void
MemPool::ReleaseMem(void *buffer)
{
	free(buffer);
}


//	#pragma mark -


AreaPool::AreaPool(const char* name, size_t initialSize)
	:
	fName(name)
{
	if (initialSize > 0)
		AddToPool(AcquireMem(initialSize), initialSize);
}


AreaPool::~AreaPool()
{
}


void*
AreaPool::AcquireMem(ssize_t size)
{
	area_id area;
	void* address;

	// make size a multiple of B_PAGE_SIZE
	size = (size + B_PAGE_SIZE - 1) & ~(B_PAGE_SIZE - 1);

	area = create_area(fName, &address, B_ANY_ADDRESS, size,
		B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);

	if (area < B_OK) {
	   	printf("ERROR: AreaPool couldn't allocate area!!\n");
	   	return NULL;
	}

	return address;
}


void
AreaPool::ReleaseMem(void *buffer)
{
	area_id trash = area_for(buffer);
	if (trash < B_ERROR)
		return;

	delete_area(trash);
}