20060303a

1 files changed, 379 insertions, 0 deletions

diff --git a/appl/cmd/tail.b b/appl/cmd/tail.b
new file mode 100644
index 00000000..07d900d1
--- /dev/null
+++ b/appl/cmd/tail.b
@@ -0,0 +1,379 @@
+implement Tail;
+
+include "sys.m";
+sys: Sys;
+
+include "draw.m";
+
+include "bufio.m";
+bufmod : Bufio;
+Iobuf : import bufmod;
+
+include "string.m";
+	str : String;
+
+count, anycount, follow : int;
+file : ref sys->FD;
+bout : ref Iobuf;
+BSize : con 8*1024;
+
+BEG, END, CHARS, LINES , FWD, REV : con iota;
+ 
+origin := END;
+units := LINES;
+dir := FWD;
+
+
+Tail: module
+{
+	init:	fn(nil: ref Draw->Context, argv: list of string);
+};
+
+
+init(nil: ref Draw->Context, argv: list of string)
+{
+	sys = load Sys Sys->PATH;
+	str = load String String->PATH;
+	bufmod = load Bufio Bufio->PATH;
+	seekable : int;
+	bout = bufmod->fopen(sys->fildes(1),bufmod->OWRITE);
+	argv=parse(tl argv);
+	if(dir==REV && (units==CHARS || follow || origin==BEG))
+		fail("incompatible options");
+	if(!anycount){
+		if (dir==REV)
+			count= 16r7fffffff;
+		else
+			count = 10;
+	}
+	if(origin==BEG && units==LINES && count>0)
+		count--;
+	if(len argv > 1)
+		usage();
+	if(argv == nil || hd argv == "-") {
+		file = sys->fildes(0);
+		seekable = 0;
+	}
+	else {
+		if((file=sys->open(hd argv,sys->OREAD)) == nil )
+			fatal(hd argv);
+		(ok, stat) := sys->fstat(file);
+		seekable = sys->seek(file,big 0,sys->SEEKSTART) == big 0 && stat.length > big 0;
+	}
+
+	if(!seekable && origin==END)
+		keep();
+	else if(!seekable && origin==BEG)
+		skip();
+	else if(units==CHARS && origin==END){
+		tseek(big -count, Sys->SEEKEND);
+		copy();
+	}
+	else if(units==CHARS && origin==BEG){
+		tseek(big count, Sys->SEEKSTART);
+		copy();
+	}
+	else if(units==LINES && origin==END)
+		reverse();
+	else if(units==LINES && origin==BEG)
+		skip();
+	if(follow){
+		if(seekable){
+			d : sys->Dir;
+			d.length=big -1;
+			for(;;){
+				d=trunc(d.length);
+				copy();
+				sys->sleep(5000);
+			}
+		}else{
+			for(;;){
+				copy();
+				sys->sleep(5000);
+			}
+		}
+	}
+	exit;
+}
+
+
+trunc(length : big) : sys->Dir
+{
+	(i,d):=sys->fstat(file);
+	if(d.length < length)
+		d.length = tseek(big 0, sys->SEEKSTART);
+	return d;
+}
+
+
+skip()	# read past head of the file to find tail 
+{
+	n : int;
+	buf := array[BSize] of byte;
+	if(units == CHARS) {
+		for( ; count>0; count -=n) {
+			if (count<BSize) 
+				n=count;
+			else
+				n=BSize;
+			n = tread(buf, n);
+			if(n == 0)
+				return;
+		}
+	} else { # units == LINES
+		i:=0;
+		n=0;
+		while(count > 0) {
+			n = tread(buf, BSize);
+			if(n == 0)
+				return;
+			for(i=0; i<n && count>0; i++)
+				if(buf[i]==byte '\n')
+					count--;
+		}
+		twrite(buf[i:n]);
+	}
+	copy();
+}
+
+
+copy()
+{
+	buf := array[BSize] of byte;
+	while((n := tread(buf, BSize)) > 0){
+		twrite(buf[0:n]);
+	}
+	bout.flush();	
+}
+
+
+keep()	# read whole file, keeping the tail 
+{	# complexity=length(file)*length(tail).  could be linear
+	j, k : int;
+	length:=0;
+	buf : array of byte;
+	tbuf : array of byte;
+	bufsize := 0;
+	for(n:=1; n;) {
+		if(length+BSize > bufsize ) {
+			bufsize += 2*BSize;
+			tbuf = array[bufsize+1] of byte;
+			tbuf[0:]=buf[0:];
+			buf = tbuf;
+		}
+		for( ; n && length<bufsize; length+=n)
+			n = tread(buf[length:], bufsize-length);
+		if(count >= length)
+			continue;
+		if(units == CHARS)
+			j = length - count;
+		else{ # units == LINES 
+			if (int buf[length-1]=='\n')
+				j =  length-1;
+			else
+				j=length;
+			for(k=0; j>0; j--)
+				if(int buf[j-1] == '\n')
+					if(++k >= count)
+						break;
+		}
+		length-=j;
+		buf[0:]=buf[j:j+length];
+	}
+	if(dir == REV) {
+		if(length>0 && buf[length-1]!= byte '\n')
+			buf[length++] = byte '\n';
+		for(j=length-1 ; j>0; j--)
+			if(buf[j-1] == byte '\n') {
+				twrite(buf[j:length]);
+				if(--count <= 0)
+					return;
+				length = j;
+			}
+	}
+	if(count > 0 && length > 0)
+		twrite(buf[0:length]);
+	bout.flush();
+}
+
+reverse()	# count backward and print tail of file 
+{
+	length := 0;
+	n := 0;
+	buf : array of byte;
+	pos := tseek(big 0, sys->SEEKEND);
+	bufsize := 0;
+	for(first:=1; pos>big 0 && count>0; first=0) {
+		if (pos>big BSize)
+			n = BSize;
+		else
+			n = int pos;
+		pos -= big n;
+		if(length+2*n > bufsize) {
+			bufsize += BSize*((length+2*n-bufsize+BSize-1)/BSize);
+			tbuf := array[bufsize+1] of byte;
+			tbuf[0:] = buf;
+			buf = tbuf;
+		}
+		length += n;
+		abuf := array[length] of byte;
+		abuf[0:] = buf[0:length];
+		buf[n:] = abuf;
+		tseek(pos, sys->SEEKSTART);
+		if(tread(buf, n) != n)
+			fatal("length error");
+		if(first && buf[length-1]!= byte '\n')
+			buf[length++] = byte '\n';
+		for(n=length-1 ; n>0 && count>0; n--)
+			if(buf[n-1] == byte '\n') {
+				count--;
+				if(dir == REV){
+					twrite(buf[n:length]);
+					bout.flush();
+				}
+				length = n;
+			}
+	}
+	if(dir == FWD) {
+		if (n==0)
+			tseek(big 0 , sys->SEEKSTART);
+		else
+			tseek(pos+big n+big 1, sys->SEEKSTART);
+			
+		copy();
+	} else if(count > 0)
+		twrite(buf[0:length]);
+	bout.flush();
+}
+
+
+tseek(o : big, p: int) : big
+{
+	o = sys->seek(file, o, p);
+	if(o == big -1)
+		fatal("");
+	return o;
+}
+
+
+tread(buf: array of byte, n: int): int
+{
+	r := sys->read(file, buf, n);
+	if(r == -1)
+		fatal("");
+	return r;
+}
+
+
+twrite(buf:array of byte)
+{
+	str1:= string buf;
+	if(bout.puts(str1)!=len str1)
+		fatal("");
+}
+
+
+		
+fatal(s : string)
+{
+	sys->fprint(sys->fildes(2), "tail: %s: %r\n", s);
+	exit;
+}
+
+fail(s : string)
+{
+	sys->fprint(sys->fildes(2), "tail: %s\n", s);
+	exit;
+}
+
+
+usage()
+{
+	sys->fprint(sys->fildes(2), "usage: tail [-n N] [-c N] [-f] [-r] [+-N[bc][fr]] [file]\n");
+	exit;
+}
+
+
+getnumber(s: string) : int
+{
+	i:=0;
+	if (len s == 0) return 0;
+	if(s[i]=='-' || s[i]=='+') {
+		if (len s == 1)
+			return 0;
+		i++;
+	}
+	if(!(s[i]>='0' && s[i]<='9'))
+		return 0;
+	if(s[0] == '+')
+		origin = BEG;
+	if(anycount++)
+		fail("excess option");
+	if (s[0]=='-')
+		s=s[1:];
+	(count,nil) = str->toint(s,10);
+	if(count < 0){	# protect int args (read, fwrite) 
+		fail("too big");
+	}
+	return 1;
+}
+	
+parse(args : list of string) : list of string 
+{
+	for(; args!=nil ; args = tl args ) {
+		hdarg := hd args;
+		if(getnumber(hdarg))
+			suffix(hdarg);
+		else if(len hdarg > 1 && hdarg[0] == '-')
+			case (hdarg[1]) {
+			 'c' or 'n'=>
+				if (hdarg[1]=='c')
+					units = CHARS;
+				if(len hdarg>2 && getnumber(hdarg[2:]))
+					;
+				else if(tl args != nil && getnumber(hd tl args)) {
+					args = tl args;
+				} else
+					usage();
+			 'r' =>
+				dir = REV;
+			 'f' =>
+				follow++;
+			 '-' =>
+				args = tl args;
+			}
+		else
+			break;
+	}
+	return args;
+}
+
+
+suffix(s : string)
+{
+	i:=0;
+	while(i < len s && str->in(s[i],"0123456789+-"))
+		i++;
+	if (i==len s)
+		return;
+	if (s[i]=='b')
+		if((count*=1024) < 0)
+			fail("too big");
+	if (s[i]=='c' || s[i]=='b')
+		units = CHARS;
+	if (s[i]=='l' || s[i]=='c' || s[i]=='b')
+		i++;
+	if (i<len s){
+		case s[i] {
+		 'r'=>
+			dir = REV;
+			return;
+		 'f'=>
+			follow++;
+			return;
+		}
+	}
+	i++;
+	if (i<len s)
+		usage();
+}