util.c

一个linux下NTFS文件格式源代码

/*
 *  util.c
 *  Miscellaneous support
 *
 *  Copyright (C) 1997,1999 Martin von L鰓is
 *  Copyright (C) 1997 R間is Duchesne
 *
 *  The utf8 routines are copied from Python wstrop module.
 */

#include "ntfstypes.h"
#include "struct.h"
#include "util.h"

#include <errno.h>
/* FreeBSD doesn't seem to have EILSEQ in errno.h */
#ifndef EILSEQ
# define EILSEQ	EINVAL
#endif
#include "support.h"

/* Converts a single wide character to a sequence of utf8 bytes.
 * The character is represented in host byte order.
 * Returns the number of bytes, or 0 on error.
 */
static int
to_utf8(ntfs_u16 c,unsigned char* buf)
{
	if(c==0)
		return 0; /* No support for embedded 0 runes */
	if(c<0x80){
		if(buf)buf[0]=(unsigned char)c;
		return 1;
	}
	if(c<0x800){
		if(buf){
			buf[0] = 0xc0 | (c>>6);
			buf[1] = 0x80 | (c & 0x3f);
		}
		return 2;
	}
	if(c<0x10000){
		if(buf){
			buf[0] = 0xe0 | (c>>12);
			buf[1] = 0x80 | ((c>>6) & 0x3f);
			buf[2] = 0x80 | (c & 0x3f);
		}
		return 3;
	}
	/* We don't support characters above 0xFFFF in NTFS */
	return 0;
}

/* Decodes a sequence of utf8 bytes into a single wide character.
 * The character is returned in host byte order.
 * Returns the number of bytes consumed, or 0 on error.
 */
static int
from_utf8(const unsigned char* str,ntfs_u16 *c)
{
	int l=0,i;

	if(*str<0x80){
		*c = *str;
		return 1;
	}
	if(*str<0xc0) /* lead byte must not be 10xxxxxx */
		return 0;   /* is c0 a possible lead byte? */
	if(*str<0xe0){         /* 110xxxxx */
		*c = *str & 0x1f;
		l=2;
	}else if(*str<0xf0){   /* 1110xxxx */
		*c = *str & 0xf;
		l=3;
	}else if(*str<0xf8){   /* 11110xxx */
		*c = *str & 7;
		l=4;
	}else /* We don't support characters above 0xFFFF in NTFS */
		return 0;
	 

	for(i=1;i<l;i++){
		/* all other bytes must be 10xxxxxx */
		if((str[i] & 0xc0) != 0x80)
			return 0;
		*c <<= 6;
		*c |= str[i] & 0x3f;
	}
	return l;
}

/* Converts wide string to UTF-8. Expects two in- and two out-parameters.
 * Returns 0 on success, or error code. 
 * The caller has to free the result string.
 * There is no support for UTF-16, yet
 */
static int ntfs_dupuni2utf8(ntfs_u16* in, int in_len,char **out,int *out_len)
{
	int i,tmp;
	int len8;
	unsigned char *result;

	ntfs_debug(DEBUG_NAME1,"converting l=%d\n",in_len);
	/* count the length of the resulting UTF-8 */
	for(i=len8=0;i<in_len;i++){
		tmp=to_utf8(NTFS_GETU16(in+i),0);
		if(!tmp)
			/* invalid character */
			return EILSEQ;
		len8+=tmp;
	}
	*out=result=ntfs_malloc(len8+1); /* allow for zero-termination */

	if(!result)
		return ENOMEM;
	result[len8]='\0';
	*out_len=len8;
	for(i=len8=0;i<in_len;i++)
		len8+=to_utf8(NTFS_GETU16(in+i),result+len8);
	ntfs_debug(DEBUG_NAME1,"result %p:%s\n",result,result);
	return 0;
}

/* Converts an UTF-8 sequence to a wide string. Same conventions as the
 * previous function
 */
static int ntfs_duputf82uni(unsigned char* in, int in_len,ntfs_u16** out,int *out_len)
{
	int i,tmp;
	int len16;

	ntfs_u16* result;
	ntfs_u16 wtmp;
	for(i=len16=0;i<in_len;i+=tmp,len16++){
		tmp=from_utf8(in+i,&wtmp);
		if(!tmp)
			return EILSEQ;
	}
	*out=result=ntfs_malloc(2*(len16+1));
	if(!result)
		return ENOMEM;
	result[len16]=0;
	*out_len=len16;
	for(i=len16=0;i<in_len;i+=tmp,len16++)
	{
		tmp=from_utf8(in+i, &wtmp);
		NTFS_PUTU16(result+len16, wtmp);
	}
	return 0;
}

/* See above. Produces ISO-8859-1 from wide strings */
static int ntfs_dupuni288591(ntfs_u16* in,int in_len,char** out,int *out_len)
{
	int i;
	char *result;

	/* check for characters out of range */
	for(i=0;i<in_len;i++)
		if(NTFS_GETU16(in+i)>=256)
			return EILSEQ;
	*out=result=ntfs_malloc(in_len+1);
	if(!result)
		return ENOMEM;
	result[in_len]='\0';
	*out_len=in_len;
	for(i=0;i<in_len;i++)
		result[i]=(unsigned char)NTFS_GETU16(in+i);
	return 0;
}

/* See above */
static int ntfs_dup885912uni(unsigned char* in,int in_len,ntfs_u16 **out,int *out_len)
{
	int i;

	ntfs_u16* result;
	*out=result=ntfs_malloc(2*in_len);
	if(!result)
		return ENOMEM;
	*out_len=in_len;
	for(i=0;i<in_len;i++)
		NTFS_PUTU16(result+i,in[i]);
	return 0;
}

/* Encodings dispatcher */
int ntfs_encodeuni(ntfs_volume *vol,ntfs_u16 *in, int in_len,
		   char **out, int *out_len)
{
	if(vol->nct & nct_utf8)
		return ntfs_dupuni2utf8(in,in_len,out,out_len);
	else if(vol->nct & nct_iso8859_1)
		return ntfs_dupuni288591(in,in_len,out,out_len);
	else if(vol->nct & (nct_map|nct_uni_xlate))
		/* uni_xlate is handled inside map */
		return ntfs_dupuni2map(vol,in,in_len,out,out_len);
	else
		return EINVAL; /* unknown encoding */
}

int ntfs_decodeuni(ntfs_volume *vol,char *in, int in_len,
		   ntfs_u16 **out, int *out_len)
{
	if(vol->nct & nct_utf8)
		return ntfs_duputf82uni(in,in_len,out,out_len);
	else if(vol->nct & nct_iso8859_1)
		return ntfs_dup885912uni(in,in_len,out,out_len);
	else if(vol->nct & (nct_map | nct_uni_xlate))
		return ntfs_dupmap2uni(vol,in,in_len,out,out_len);
	else
		return EINVAL;
}

/* Same address space copies */
void ntfs_put(ntfs_io *dest,void *src,ntfs_size_t n)
{
	ntfs_memcpy(dest->param,src,n);
	((char*)dest->param)+=n;
}

void ntfs_get(void* dest,ntfs_io *src,ntfs_size_t n)
{
	ntfs_memcpy(dest,src->param,n);
	((char*)src->param)+=n;
}

void *ntfs_calloc(int size)
{
	void *result=ntfs_malloc(size);
	if(result)
		ntfs_bzero(result,size);
	return result;
}

#if 0
/* copy len unicode characters from from to to :) */
void ntfs_uni2ascii(char *to,char *from,int len)
{
	int i;

	for(i=0;i<len;i++)
		to[i]=from[2*i];
	to[i]='\0';
}
#endif

/* copy len asci characters from from to to :) */
void ntfs_ascii2uni(short int *to,char *from,int len)
{
	int i;

	for(i=0;i<len;i++)
		to[i]=from[i];
	to[i]=0;
}

/* strncmp for Unicode strings */
int ntfs_uni_strncmp(short int* a,short int *b,int n)
{
	int i;

	for(i=0;i<n;i++)
	{
		if(a[i]<b[i])
			return -1;
		if(b[i]<a[i])
			return 1;
	}
	return 0;
}

/* strncmp between Unicode and ASCII strings */
int ntfs_ua_strncmp(short int* a,char* b,int n)
{
	int i;

	for(i=0;i<n;i++)
	{
		if(NTFS_GETU16(a+i)<b[i])
			return -1;
		if(b[i]<NTFS_GETU16(a+i))
			return 1;
	}
	return 0;
}

/* Convert the NT UTC (based 1.1.1601, in hundred nanosecond units)
 * into Unix UTC (based 1.1.1970, in seconds)
 */
ntfs_time_t ntfs_ntutc2unixutc(ntfs_time64_t ntutc)
{
/*
 * This is very gross because
 * 1: We must do 64-bit division on a 32-bit machine
 * 2: We can't use libgcc for long long operations in the kernel
 * 3: Floating point math in the kernel would corrupt user data
 */
	const unsigned int D = 10000000;
	unsigned int H = (unsigned int)(ntutc >> 32);
	unsigned int L = (unsigned int)ntutc;
	unsigned int numerator2;
	unsigned int lowseconds;
	unsigned int result;

	/* It is best to subtract 0x019db1ded53e8000 first. */
	/* Then the 1601-based date becomes a 1970-based date. */
	if(L < (unsigned)0xd53e8000) H--;
	L -= (unsigned)0xd53e8000;
	H -= (unsigned)0x019db1de;

	/*
	 * Now divide 64-bit numbers on a 32-bit machine :-)
	 * With the subtraction already done, the result fits in 32 bits.
	 * The numerator fits in 56 bits and the denominator fits
	 * in 24 bits, so we can shift by 8 bits to make this work.
	 */

	numerator2  = (H<<8) | (L>>24);
	result      = (numerator2 / D);   /* shifted 24 right!! */
	lowseconds  = result << 24;

	numerator2  = ((numerator2-result*D)<<8) | ((L>>16)&0xff);
	result      = (numerator2 / D);   /* shifted 16 right!! */
	lowseconds |= result << 16;

	numerator2  = ((numerator2-result*D)<<8) | ((L>>8)&0xff);
	result      = (numerator2 / D);   /* shifted 8 right!! */
	lowseconds |= result << 8;

	numerator2  = ((numerator2-result*D)<<8) | (L&0xff);
	result      = (numerator2 / D);   /* not shifted */
	lowseconds |= result;

	return lowseconds;
}

/* Convert the Unix UTC into NT UTC */
ntfs_time64_t ntfs_unixutc2ntutc(ntfs_time_t t)
{
	return ((t + (ntfs_time64_t)(369*365+89)*24*3600) * 10000000);
}

/* Fill index name. */

void
ntfs_indexname(char *buf, int type)
{
	char hex[]="0123456789ABCDEF";
	int index;
	*buf++='$';
	*buf++='I';
	for (index=24; index>0; index-=4)
		if((0xF << index) & type)
			break;
	while(index>=0) {
		*buf++ = hex[(type >> index) & 0xF];
		index-=4;
	}
	*buf='\0';
}

/*
 * Local variables:
 * c-file-style: "linux"
 * End:
 */