dd.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 <u.h>
#include <libc.h>

#define	BIG	2147483647
#define	LCASE	(1<<0)
#define	UCASE	(1<<1)
#define	SWAB	(1<<2)
#define NERR	(1<<3)
#define SYNC	(1<<4)
int	cflag;
int	fflag;
char	*string;
char	*ifile;
char	*ofile;
char	*ibuf;
char	*obuf;
vlong	skip;
vlong	oseekn;
vlong	iseekn;
vlong	count;
long	files	= 1;
long	ibs	= 512;
long	obs	= 512;
long	bs;
long	cbs;
long	ibc;
long	obc;
long	cbc;
long	nifr;
long	nipr;
long	nofr;
long	nopr;
long	ntrunc;
int dotrunc = 1;
int	ibf;
int	obf;
char	*op;
int	nspace;
uchar	etoa[256];
uchar	atoe[256];
uchar	atoibm[256];
int	quiet;

void	flsh(void);
int	match(char *s);
vlong	number(long big);
void	cnull(int cc);
void	null(int c);
void	ascii(int cc);
void	unblock(int cc);
void	ebcdic(int cc);
void	ibm(int cc);
void	block(int cc);
void	term(char*);
void	stats(void);

#define	iskey(s)	((key[0] == '-') && (strcmp(key+1, s) == 0))

int
main(int argc, char *argv[])
{
	void (*conv)(int);
	char *ip;
	char *key;
	int a, c;

	conv = null;
	for(c=1; c<argc; c++) {
		key = argv[c++];
		if(c >= argc){
			fprint(2, "dd: arg %s needs a value\n", key);
			exits("arg");
		}
		string = argv[c];
		if(iskey("ibs")) {
			ibs = number(BIG);
			continue;
		}
		if(iskey("obs")) {
			obs = number(BIG);
			continue;
		}
		if(iskey("cbs")) {
			cbs = number(BIG);
			continue;
		}
		if(iskey("bs")) {
			bs = number(BIG);
			continue;
		}
		if(iskey("if")) {
			ifile = string;
			continue;
		}
		if(iskey("of")) {
			ofile = string;
			continue;
		}
		if(iskey("trunc")) {
			dotrunc = number(BIG);
			continue;
		}
		if(iskey("quiet")) {
			quiet = number(BIG);
			continue;
		}
		if(iskey("skip")) {
			skip = number(BIG);
			continue;
		}
		if(iskey("seek") || iskey("oseek")) {
			oseekn = number(BIG);
			continue;
		}
		if(iskey("iseek")) {
			iseekn = number(BIG);
			continue;
		}
		if(iskey("count")) {
			count = number(BIG);
			continue;
		}
		if(iskey("files")) {
			files = number(BIG);
			continue;
		}
		if(iskey("conv")) {
		cloop:
			if(match(","))
				goto cloop;
			if(*string == '\0')
				continue;
			if(match("ebcdic")) {
				conv = ebcdic;
				goto cloop;
			}
			if(match("ibm")) {
				conv = ibm;
				goto cloop;
			}
			if(match("ascii")) {
				conv = ascii;
				goto cloop;
			}
			if(match("block")) {
				conv = block;
				goto cloop;
			}
			if(match("unblock")) {
				conv = unblock;
				goto cloop;
			}
			if(match("lcase")) {
				cflag |= LCASE;
				goto cloop;
			}
			if(match("ucase")) {
				cflag |= UCASE;
				goto cloop;
			}
			if(match("swab")) {
				cflag |= SWAB;
				goto cloop;
			}
			if(match("noerror")) {
				cflag |= NERR;
				goto cloop;
			}
			if(match("sync")) {
				cflag |= SYNC;
				goto cloop;
			}
		}
		fprint(2, "dd: bad arg: %s\n", key);
		exits("arg");
	}
	if(conv == null && cflag&(LCASE|UCASE))
		conv = cnull;
	if(ifile)
		ibf = open(ifile, 0);
	else
		ibf = dup(0, -1);
	if(ibf < 0) {
		fprint(2, "dd: open %s: %r\n", ifile);
		exits("open");
	}
	if(ofile){
		if(dotrunc)
			obf = create(ofile, 1, 0664);
		else
			obf = open(ofile, 1);
		if(obf < 0) {
			fprint(2, "dd: create %s: %r\n", ofile);
			exits("create");
		}
	}else{
		obf = dup(1, -1);
		if(obf < 0) {
			fprint(2, "dd: can't dup file descriptor: %s: %r\n", ofile);
			exits("dup");
		}
	}
	if(bs)
		ibs = obs = bs;
	if(ibs == obs && conv == null)
		fflag++;
	if(ibs == 0 || obs == 0) {
		fprint(2, "dd: counts: cannot be zero\n");
		exits("counts");
	}
	ibuf = sbrk(ibs);
	if(fflag)
		obuf = ibuf;
	else
		obuf = sbrk(obs);
	sbrk(64);	/* For good measure */
	if(ibuf == (char *)-1 || obuf == (char *)-1) {
		fprint(2, "dd: not enough memory: %r\n");
		exits("memory");
	}
	ibc = 0;
	obc = 0;
	cbc = 0;
	op = obuf;

/*
	if(signal(SIGINT, SIG_IGN) != SIG_IGN)
		signal(SIGINT, term);
*/
	seek(obf, obs*oseekn, 1);
	seek(ibf, ibs*iseekn, 1);
	while(skip) {
		read(ibf, ibuf, ibs);
		skip--;
	}

	ip = 0;
loop:
	if(ibc-- == 0) {
		ibc = 0;
		if(count==0 || nifr+nipr!=count) {
			if(cflag&(NERR|SYNC))
			for(ip=ibuf+ibs; ip>ibuf;)
				*--ip = 0;
			ibc = read(ibf, ibuf, ibs);
		}
		if(ibc == -1) {
			perror("read");
			if((cflag&NERR) == 0) {
				flsh();
				term("errors");
			}
			ibc = 0;
			for(c=0; c<ibs; c++)
				if(ibuf[c] != 0)
					ibc = c+1;
			seek(ibf, ibs, 1);
			stats();
		}else if(ibc == 0 && --files<=0) {
			flsh();
			term(nil);
		}
		if(ibc != ibs) {
			nipr++;
			if(cflag&SYNC)
				ibc = ibs;
		} else
			nifr++;
		ip = ibuf;
		c = (ibc>>1) & ~1;
		if(cflag&SWAB && c)
		do {
			a = *ip++;
			ip[-1] = *ip;
			*ip++ = a;
		} while(--c);
		ip = ibuf;
		if(fflag) {
			obc = ibc;
			flsh();
			ibc = 0;
		}
		goto loop;
	}
	c = 0;
	c |= *ip++;
	c &= 0377;
	(*conv)(c);
	goto loop;
}

void
flsh(void)
{
	int c;

	if(obc) {
		/* don't perror dregs of previous errors on a short write */
		werrstr("");
		c = write(obf, obuf, obc);
		if(c != obc) {
			if(c > 0)
				++nopr;
			perror("write");
			term("errors");
		}
		if(obc == obs)
			nofr++;
		else
			nopr++;
		obc = 0;
	}
}

int
match(char *s)
{
	char *cs;

	cs = string;
	while(*cs++ == *s)
		if(*s++ == '\0')
			goto true;
	if(*s != '\0')
		return 0;

true:
	cs--;
	string = cs;
	return 1;
}

vlong
number(long big)
{
	char *cs;
	vlong n;

	cs = string;
	n = 0;
	while(*cs >= '0' && *cs <= '9')
		n = n*10 + *cs++ - '0';
	for(;;)
	switch(*cs++) {

	case 'k':
		n *= 1024;
		continue;

/*	case 'w':
		n *= sizeof(int);
		continue;
*/

	case 'b':
		n *= 512;
		continue;

/*	case '*':*/
	case 'x':
		string = cs;
		n *= number(BIG);

	case '\0':
		if(n>=big || n<0) {
			fprint(2, "dd: argument %lld out of range\n", n);
			exits("range");
		}
		return n;
	}
	/* never gets here */
}

void
cnull(int cc)
{
	int c;

	c = cc;
	if((cflag&UCASE) && c>='a' && c<='z')
		c += 'A'-'a';
	if((cflag&LCASE) && c>='A' && c<='Z')
		c += 'a'-'A';
	null(c);
}

void
null(int c)
{

	*op = c;
	op++;
	if(++obc >= obs) {
		flsh();
		op = obuf;
	}
}

void
ascii(int cc)
{
	int c;

	c = etoa[cc];
	if(cbs == 0) {
		cnull(c);
		return;
	}
	if(c == ' ') {
		nspace++;
		goto out;
	}
	while(nspace > 0) {
		null(' ');
		nspace--;
	}
	cnull(c);

out:
	if(++cbc >= cbs) {
		null('\n');
		cbc = 0;
		nspace = 0;
	}
}

void
unblock(int cc)
{
	int c;

	c = cc & 0377;
	if(cbs == 0) {
		cnull(c);
		return;
	}
	if(c == ' ') {
		nspace++;
		goto out;
	}
	while(nspace > 0) {
		null(' ');
		nspace--;
	}
	cnull(c);

out:
	if(++cbc >= cbs) {
		null('\n');
		cbc = 0;
		nspace = 0;
	}
}

void
ebcdic(int cc)
{
	int c;

	c = cc;
	if(cflag&UCASE && c>='a' && c<='z')
		c += 'A'-'a';
	if(cflag&LCASE && c>='A' && c<='Z')
		c += 'a'-'A';
	c = atoe[c];
	if(cbs == 0) {
		null(c);
		return;
	}
	if(cc == '\n') {
		while(cbc < cbs) {
			null(atoe[' ']);
			cbc++;
		}
		cbc = 0;
		return;
	}
	if(cbc == cbs)
		ntrunc++;
	cbc++;
	if(cbc <= cbs)
		null(c);
}

void
ibm(int cc)
{
	int c;

	c = cc;
	if(cflag&UCASE && c>='a' && c<='z')
		c += 'A'-'a';
	if(cflag&LCASE && c>='A' && c<='Z')
		c += 'a'-'A';
	c = atoibm[c] & 0377;
	if(cbs == 0) {
		null(c);
		return;
	}
	if(cc == '\n') {
		while(cbc < cbs) {
			null(atoibm[' ']);
			cbc++;
		}
		cbc = 0;
		return;
	}
	if(cbc == cbs)
		ntrunc++;
	cbc++;
	if(cbc <= cbs)
		null(c);
}

void
block(int cc)
{
	int c;

	c = cc;
	if(cflag&UCASE && c>='a' && c<='z')
		c += 'A'-'a';
	if(cflag&LCASE && c>='A' && c<='Z')
		c += 'a'-'A';
	c &= 0377;
	if(cbs == 0) {
		null(c);
		return;
	}
	if(cc == '\n') {
		while(cbc < cbs) {
			null(' ');
			cbc++;
		}
		cbc = 0;
		return;
	}
	if(cbc == cbs)
		ntrunc++;
	cbc++;
	if(cbc <= cbs)
		null(c);
}

void
term(char *status)
{
	stats();
	exits(status);
}

void
stats(void)
{
	if(quiet)
		return;
	fprint(2, "%lud+%lud records in\n", nifr, nipr);
	fprint(2, "%lud+%lud records out\n", nofr, nopr);
	if(ntrunc)
		fprint(2, "%lud truncated records\n", ntrunc);
}

uchar	etoa[] =
{
	0000,0001,0002,0003,0234,0011,0206,0177,
	0227,0215,0216,0013,0014,0015,0016,0017,
	0020,0021,0022,0023,0235,0205,0010,0207,
	0030,0031,0222,0217,0034,0035,0036,0037,
	0200,0201,0202,0203,0204,0012,0027,0033,
	0210,0211,0212,0213,0214,0005,0006,0007,
	0220,0221,0026,0223,0224,0225,0226,0004,
	0230,0231,0232,0233,0024,0025,0236,0032,
	0040,0240,0241,0242,0243,0244,0245,0246,
	0247,0250,0133,0056,0074,0050,0053,0041,
	0046,0251,0252,0253,0254,0255,0256,0257,
	0260,0261,0135,0044,0052,0051,0073,0136,
	0055,0057,0262,0263,0264,0265,0266,0267,
	0270,0271,0174,0054,0045,0137,0076,0077,
	0272,0273,0274,0275,0276,0277,0300,0301,
	0302,0140,0072,0043,0100,0047,0075,0042,
	0303,0141,0142,0143,0144,0145,0146,0147,
	0150,0151,0304,0305,0306,0307,0310,0311,
	0312,0152,0153,0154,0155,0156,0157,0160,
	0161,0162,0313,0314,0315,0316,0317,0320,
	0321,0176,0163,0164,0165,0166,0167,0170,
	0171,0172,0322,0323,0324,0325,0326,0327,
	0330,0331,0332,0333,0334,0335,0336,0337,
	0340,0341,0342,0343,0344,0345,0346,0347,
	0173,0101,0102,0103,0104,0105,0106,0107,
	0110,0111,0350,0351,0352,0353,0354,0355,
	0175,0112,0113,0114,0115,0116,0117,0120,
	0121,0122,0356,0357,0360,0361,0362,0363,
	0134,0237,0123,0124,0125,0126,0127,0130,
	0131,0132,0364,0365,0366,0367,0370,0371,
	0060,0061,0062,0063,0064,0065,0066,0067,
	0070,0071,0372,0373,0374,0375,0376,0377,
};
uchar	atoe[] =
{
	0000,0001,0002,0003,0067,0055,0056,0057,
	0026,0005,0045,0013,0014,0015,0016,0017,
	0020,0021,0022,0023,0074,0075,0062,0046,
	0030,0031,0077,0047,0034,0035,0036,0037,
	0100,0117,0177,0173,0133,0154,0120,0175,
	0115,0135,0134,0116,0153,0140,0113,0141,
	0360,0361,0362,0363,0364,0365,0366,0367,
	0370,0371,0172,0136,0114,0176,0156,0157,
	0174,0301,0302,0303,0304,0305,0306,0307,
	0310,0311,0321,0322,0323,0324,0325,0326,
	0327,0330,0331,0342,0343,0344,0345,0346,
	0347,0350,0351,0112,0340,0132,0137,0155,
	0171,0201,0202,0203,0204,0205,0206,0207,
	0210,0211,0221,0222,0223,0224,0225,0226,
	0227,0230,0231,0242,0243,0244,0245,0246,
	0247,0250,0251,0300,0152,0320,0241,0007,
	0040,0041,0042,0043,0044,0025,0006,0027,
	0050,0051,0052,0053,0054,0011,0012,0033,
	0060,0061,0032,0063,0064,0065,0066,0010,
	0070,0071,0072,0073,0004,0024,0076,0341,
	0101,0102,0103,0104,0105,0106,0107,0110,
	0111,0121,0122,0123,0124,0125,0126,0127,
	0130,0131,0142,0143,0144,0145,0146,0147,
	0150,0151,0160,0161,0162,0163,0164,0165,
	0166,0167,0170,0200,0212,0213,0214,0215,
	0216,0217,0220,0232,0233,0234,0235,0236,
	0237,0240,0252,0253,0254,0255,0256,0257,
	0260,0261,0262,0263,0264,0265,0266,0267,
	0270,0271,0272,0273,0274,0275,0276,0277,
	0312,0313,0314,0315,0316,0317,0332,0333,
	0334,0335,0336,0337,0352,0353,0354,0355,
	0356,0357,0372,0373,0374,0375,0376,0377,
};
uchar	atoibm[] =
{
	0000,0001,0002,0003,0067,0055,0056,0057,
	0026,0005,0045,0013,0014,0015,0016,0017,
	0020,0021,0022,0023,0074,0075,0062,0046,
	0030,0031,0077,0047,0034,0035,0036,0037,
	0100,0132,0177,0173,0133,0154,0120,0175,
	0115,0135,0134,0116,0153,0140,0113,0141,
	0360,0361,0362,0363,0364,0365,0366,0367,
	0370,0371,0172,0136,0114,0176,0156,0157,
	0174,0301,0302,0303,0304,0305,0306,0307,
	0310,0311,0321,0322,0323,0324,0325,0326,
	0327,0330,0331,0342,0343,0344,0345,0346,
	0347,0350,0351,0255,0340,0275,0137,0155,
	0171,0201,0202,0203,0204,0205,0206,0207,
	0210,0211,0221,0222,0223,0224,0225,0226,
	0227,0230,0231,0242,0243,0244,0245,0246,
	0247,0250,0251,0300,0117,0320,0241,0007,
	0040,0041,0042,0043,0044,0025,0006,0027,
	0050,0051,0052,0053,0054,0011,0012,0033,
	0060,0061,0032,0063,0064,0065,0066,0010,
	0070,0071,0072,0073,0004,0024,0076,0341,
	0101,0102,0103,0104,0105,0106,0107,0110,
	0111,0121,0122,0123,0124,0125,0126,0127,
	0130,0131,0142,0143,0144,0145,0146,0147,
	0150,0151,0160,0161,0162,0163,0164,0165,
	0166,0167,0170,0200,0212,0213,0214,0215,
	0216,0217,0220,0232,0233,0234,0235,0236,
	0237,0240,0252,0253,0254,0255,0256,0257,
	0260,0261,0262,0263,0264,0265,0266,0267,
	0270,0271,0272,0273,0274,0275,0276,0277,
	0312,0313,0314,0315,0316,0317,0332,0333,
	0334,0335,0336,0337,0352,0353,0354,0355,
	0356,0357,0372,0373,0374,0375,0376,0377,
};