/*
   Microsoft Mosaic
   
   Copyright 1995 Microsoft, Inc.
   All Rights Reserved

   Create 1/27/95 Chris Franklin CMF

 */

#include "all.h"
#include "safestrm.h"
#include "stdio.h"

#ifdef FEATURE_IMG_THREADS

#define MIN_BLOCK 0x1000
#define DAT_SIZE 4
typedef struct _DATABLOCK
{
	struct _DATABLOCK *pnext;
	unsigned long cbAlloc;
	unsigned char udata[DAT_SIZE];
} DATABLOCK,*PDATABLOCK;
#define HYSTERESIS_SIZE 0x800

static const long crc_32_tab[] =
{
        0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL, 0x076DC419L, 0x706AF48FL, 0xE963A535L, 0x9E6495A3L,
        0x0EDB8832L, 0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L, 0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L, 0x90BF1D91L,
        0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL, 0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L,
        0x136C9856L, 0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL, 0x14015C4FL, 0x63066CD9L, 0xFA0F3D63L, 0x8D080DF5L,
        0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L, 0xA2677172L, 0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL,
        0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L, 0x32D86CE3L, 0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L,
        0x26D930ACL, 0x51DE003AL, 0xC8D75180L, 0xBFD06116L, 0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L, 0xB8BDA50FL,
        0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L, 0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL,

        0x76DC4190L, 0x01DB7106L, 0x98D220BCL, 0xEFD5102AL, 0x71B18589L, 0x06B6B51FL, 0x9FBFE4A5L, 0xE8B8D433L,
        0x7807C9A2L, 0x0F00F934L, 0x9609A88EL, 0xE10E9818L, 0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L,
        0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL, 0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L,
        0x65B0D9C6L, 0x12B7E950L, 0x8BBEB8EAL, 0xFCB9887CL, 0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L,
        0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L, 0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL,
        0x4369E96AL, 0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L, 0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL, 0xDD0D7CC9L,
        0x5005713CL, 0x270241AAL, 0xBE0B1010L, 0xC90C2086L, 0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
        0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L, 0x59B33D17L, 0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL,

        0xEDB88320L, 0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL, 0xEAD54739L, 0x9DD277AFL, 0x04DB2615L, 0x73DC1683L,
        0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L, 0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L,
        0xF00F9344L, 0x8708A3D2L, 0x1E01F268L, 0x6906C2FEL, 0xF762575DL, 0x806567CBL, 0x196C3671L, 0x6E6B06E7L,
        0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL, 0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L,
        0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L, 0xD1BB67F1L, 0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL,
        0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L, 0x41047A60L, 0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL, 0x4669BE79L,
        0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L, 0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL,
        0xC5BA3BBEL, 0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L, 0xC2D7FFA7L, 0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL,

        0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL, 0x026D930AL, 0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L,
        0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L, 0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L,
        0x86D3D2D4L, 0xF1D4E242L, 0x68DDB3F8L, 0x1FDA836EL, 0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L, 0x18B74777L,
        0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL, 0x8F659EFFL, 0xF862AE69L, 0x616BFFD3L, 0x166CCF45L,
        0xA00AE278L, 0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L, 0xA7672661L, 0xD06016F7L, 0x4969474DL, 0x3E6E77DBL,
        0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L, 0x37D83BF0L, 0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
        0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L, 0xBAD03605L, 0xCDD70693L, 0x54DE5729L, 0x23D967BFL,
        0xB3667A2EL, 0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L, 0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL, 0x2D02EF8DL
};

/* update running CRC calculation with contents of a buffer */

unsigned long CRC32Compute(unsigned char *pb,unsigned long cb,unsigned long crc32)
{
    //** Put CRC in form loop want it
    crc32 = (-1L - crc32);

    while (cb--)
    {
        crc32 = crc_32_tab[(BYTE)crc32 ^ *pb++] ^ ((crc32 >> 8) & 0x00FFFFFFL);
    }

    //** Put CRC in form client wants it
    return (-1L - crc32);
}


//	initializes a SAFESTREAM.  doesn't allocate it, assumes SAFESTREAM is either
//	allocated statically or as member of another struct.  Call SS_New the first
//	time and SS_Reset to reinit contents each time.
//	Returns: TRUE on error.
boolean bSS_New(PSAFESTREAM self)
{
	memset(self,0,sizeof(SAFESTREAM));
	self->evDataRead = CreateEvent(NULL,	// no security
								   FALSE,	// automatic reset
								   FALSE,	// initially false
								   NULL);	// unnamed
	if (self->evDataRead == NULL) return TRUE;
	return FALSE;
}

//	reinitializes a SAFESTREAM that has already been init'ed by bSS_New
void SS_Reset(PSAFESTREAM self)
{
	HANDLE evDataRead = self->evDataRead;
	PDATABLOCK pblock = self->pfirst;
	PDATABLOCK pnext;

	memset(self,0,sizeof(SAFESTREAM));
	self->cbCheckSum = CRC32_INITIAL_VALUE;
	self->evDataRead = evDataRead;
	while (pblock)
	{
		pnext = pblock->pnext;
		GTR_FREE(pblock);
		pblock = pnext;
	}
}

//	frees a SAFESTREAM that has been init'ed by bSS_New
void SS_Free(PSAFESTREAM self)
{
	SS_Reset(self);
	CloseHandle(self->evDataRead);
	self->evDataRead = NULL;
}

//	writes cbCount bytes of data in pdata to end of self.  frees unneeded blocks
//	(ie those that have been already read)
//	Returns:  TRUE on success, FALSE on failure.  On error sets errorCode and
//		bEOF
boolean bSS_Write(PSAFESTREAM self,unsigned char *pudata,unsigned long cbCount)
{
	PDATABLOCK pwrite = self->pwrite;
	PDATABLOCK pnext;
	PDATABLOCK pblock;
	unsigned long cbWrite = self->cbWrite;
	unsigned long cbOldWrite = cbWrite;
	unsigned long cbWriteBase = self->cbWriteBase;
	unsigned long cbAlloc;
	unsigned long cbPrevAlloc = 0;
	unsigned long cbXfer = 0;
	unsigned long cbOffset;
	enum GuitError errorCode = errNoError;

#define	HEADER_SIZE (sizeof(DATABLOCK)- DAT_SIZE)

	if (pwrite)
	{
		cbOffset = cbWrite - cbWriteBase;
		cbXfer = cbCount;
		cbPrevAlloc = pwrite->cbAlloc; 
		if(cbOffset+cbCount > cbPrevAlloc) cbXfer = cbPrevAlloc - cbOffset;
		if (cbXfer) memcpy(&pwrite->udata[cbOffset],pudata,cbXfer);
		cbWrite += cbXfer;
	}

//	If can't fit data in current block, alloc one big enough for remainder,
//	but round total size of DATABLOCK structure to MIN_BLOCK.

	if (cbCount > cbXfer)
	{
	
//	At this point we can free blocks that have been read.
//	NOTE: if pfirst == NULL, then so are pwrite and pread
//	NOTE: due to concurrency, pblock may be != to self->pread at loop end

		pblock = self->pfirst;
		while (pblock != self->pread)
		{
			pnext = pblock->pnext;
			GTR_FREE(pblock);
			pblock = pnext;
		}
		self->pfirst = pblock;
			
		pudata += cbXfer;
		cbXfer = cbCount - cbXfer;
		cbAlloc = ((cbXfer + HEADER_SIZE + MIN_BLOCK-1) /  MIN_BLOCK ) * MIN_BLOCK;
		pblock = GTR_MALLOC(cbAlloc);
		if (pblock == NULL)
		{
			errorCode = errOUTOFMEM;
			goto exitPoint;
		}
		if (self->pfirst == NULL) 
		{
			self->pread = self->pfirst = pblock;
		}
		else pwrite->pnext = pblock;
		pwrite = pblock;
		cbAlloc -= HEADER_SIZE;
		pwrite->pnext = NULL;
		pwrite->cbAlloc = cbAlloc;
		cbWriteBase += cbPrevAlloc;
		self->cbTotal += cbAlloc; 
		memcpy(&pwrite->udata[0],pudata,cbXfer);
		cbWrite	+= cbXfer;
	}

exitPoint:
	self->cbWrite = cbWrite;
	self->cbWriteBase = cbWriteBase;
	self->pwrite = pwrite;
	if (cbWrite >= self->cbNeed && self->cbNeed > self->cbSignalWrite && (cbOldWrite == 0 || (cbWrite-self->cbRead) > HYSTERESIS_SIZE))
	{
		if (!SetEvent(self->evDataRead)) errorCode = errInternalError;
		else self->cbSignalWrite = cbWrite;
	}
	if (errorCode != errNoError) SS_EOF(self,errorCode);
	return errorCode == errNoError ? TRUE:FALSE;
}

//	reads cbCount bytes into pudata, unless EOF occurs in which case less
//	are read.
//	Returns: the actual number of bytes read
unsigned long cbSS_Read(PSAFESTREAM self,unsigned char *pudata,unsigned long cbCount)
{
	unsigned long cbRead = self->cbRead;
	unsigned long cbReadBase = self->cbReadBase;
	unsigned long cbToXfer;
	unsigned long cbXfer;
	unsigned long cbOffset;
	PDATABLOCK pread;
	unsigned char *puread = pudata;

	self->cbNeed = cbRead + cbCount;
	while ((!self->bEOF) && self->cbNeed > self->cbWrite)
	{
		WaitForSingleObject(self->evDataRead,INFINITE);
	}

//	after EOF self->cbWrite cannot change
	if (self->cbNeed > self->cbWrite) cbCount = self->cbWrite-cbRead;
	pread = self->pread;
	cbToXfer = cbCount;
	cbOffset = cbRead-cbReadBase;

	while (cbToXfer)
	{
		cbXfer = pread->cbAlloc - cbOffset;
		if (cbXfer > cbToXfer) cbXfer = cbToXfer;

//	NOTE: we never follow the pwrite->pnext link before we know that there
//	is data beyond this block.  this implies that we may have already
//	read all the data in pwrite.
		if (cbXfer)
		{
			memcpy(puread,&pread->udata[cbOffset],cbXfer);
			puread += cbXfer;
			cbToXfer -= cbXfer;
			cbRead += cbXfer;
		}
		if (cbToXfer) {
#ifdef XX_DEBUG
			if (pread->pnext == NULL)
			{
				XX_Assert((0), ("bad links found in cbSS_Read\n"));
			}
#endif
			cbOffset = 0;
			cbReadBase += pread->cbAlloc;
			pread = pread->pnext;
		}
	}
			
	self->pread = pread;
	self->cbReadBase = cbReadBase;
	self->cbRead = cbRead;
	self->cbCheckSum = CRC32Compute(pudata,cbCount,self->cbCheckSum);
	return cbCount;
}

//	writer calls SS_EOF when it has no more data to write and also indicates
//	why the stream has finished.  reader detects EOF when cbSS_Read returns
//	fewer bytes than requested.
void SS_EOF(PSAFESTREAM self,enum GuitErr errorCode)
{
	if (self->errorCode == errNoError) self->errorCode = errorCode;
	self->bEOF = TRUE;
	if (!SetEvent(self->evDataRead)) self->errorCode = errInternalError;
}

//	reader calls cbSS_ErrorCode to interrogate the reason for EOF.  this is
//	only valid for reader after EOF has been detected - ie reader detects EOF.
//	the writer may interogate/set it at any time.
enum GuitErr cbSS_ErrorCode(PSAFESTREAM self)
{
	return self->errorCode;
}	

//	returns checksum of all bytes read at point of call
extern unsigned long cbSS_CheckSum(PSAFESTREAM self)
{
	return self->cbCheckSum;
}

//	returns number of bytes read at point of call
extern unsigned long cbSS_BytesRead(PSAFESTREAM self)
{
	return self->cbRead;
}
#endif