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pc(1): add pb (thanks, BurnZeZ); add bit numbering

--- a/sys/man/1/pc

+++ b/sys/man/1/pc

@@ -65,6 +65,9 @@

 .I hex(n)

 Display \fIn\fR in hexadecimal.

 .TP

+.I pb(n, b)

+Display \fIn\fR in base \fIb\fR (currently must be one of 0, 2, 8, 10, 16; 0 uses the defined output base).

+.TP

 .I abs(n)

 Absolute value of \fIn\fR.

 .TP

@@ -135,6 +138,10 @@

 Use truncating division (same as C).

 \fIa\fR / \fIb\fR is rounded towards zero.

 \fIa\fR % \fIb\fR can be negative.

+.TP

+\fL\'\fR 1

+Enable numbering bits (disable with 0).

+If the base is a power of two, print the number of the corresponding bit above each digit.

 .SH SOURCE

 .B /sys/src/cmd/pc.y

 .SH "SEE ALSO"

--- a/sys/src/cmd/pc.y

+++ b/sys/src/cmd/pc.y

@@ -7,7 +7,7 @@

 #include <thread.h>

 #include <libsec.h>

-int inbase = 10, outbase, divmode, sep, fail, prompt;

+int inbase = 10, outbase, divmode, sep, heads, fail, prompt;

 enum { MAXARGS = 16 };

 typedef struct Num Num;

@@ -228,11 +228,38 @@

 	return *p;

 }

+static void

+printhead(int n, int s, int sp, char *t)

+{

+	char *q;

+	int i, j, k;

+	

+	for(i = 1; i < n; i *= 10)

+		;

+	while(i /= 10, i != 0){

+		q = t;

+		*--q = 0;

+		for(j = 0, k = 0; j < n; j += s, k++){

+			if(k == sep && sep != 0){

+				*--q = ' ';

+				k = 0;

+			}

+			if(j >= i || j == 0 && i == 1)

+				*--q = '0' + j / i % 10;

+			else

+				*--q = ' ';

+		}

+		for(j = 0; j < sp; j++)

+			*--q = ' ';

+		print("%s\n", q);

+	}

+}

+

 void

 numprint(Num *n)

 {

 	int b;

-	int l, i;

+	int l, i, st, sp;

 	char *s, *t, *p, *q;

 	if(n == nil) return;

@@ -246,6 +273,18 @@

 	l = strlen(s);

 	t = emalloc(l * 2 + 4);

 	q = t + l * 2 + 4;

+	if(heads){

+		switch(b){

+		case 16: st = 4; sp = 2; break;

+		case 8: st = 3; sp = 1; break;

+		case 2: st = 1; sp = 2; break;

+		default: st = 0; sp = 0;

+		}

+		if(n->sign < 0)

+			sp++;

+		if(st != 0)

+			printhead(mpsignif(n), st, sp, q);

+	}

 	*--q = 0;

 	for(p = s + l - 1, i = 0; p >= s && *p != '-'; p--, i++){

 		if(sep != 0 && i == sep){

@@ -409,6 +448,19 @@

 		numdecref(last);

 		last = nil;

 	}

+	| '\'' { save = inbase; inbase = 10; } expr {

+		inbase = save;

+		save = heads;

+		if(!fail) 

+			heads = mptoi($3);

+		if(heads != 0 && heads != 1){

+			error("no.");

+			heads = save;

+		}

+		numdecref($3);

+		numdecref(last);

+		last = nil;

+	}

 	| error

 expr: LNUM

@@ -639,6 +691,30 @@

 }

 Num *

+fnpb(int, Num **a)

+{

+	Num *r;

+	int b;

+	

+	if(toint(a[1], &b, 1)){

+	out:

+		numdecref(a[0]);

+		numdecref(a[1]);

+		return nil;

+	}

+	if(b != 0 && b != 2 && b != 8 && b != 10 && b != 16){

+		error("unsupported base");

+		goto out;

+	}

+	r = nummod(a[0]);

+	if(b == 0)

+		r->b = 0;

+	else

+		r->b = STRONG | b;

+	return r;

+}

+

+Num *

 fnabs(int, Num **a)

 {

 	Num *r;

@@ -903,6 +979,7 @@

 	regfunc("dec", fndec, 1);

 	regfunc("oct", fnoct, 1);

 	regfunc("bin", fnbin, 1);

+	regfunc("pb", fnpb, 2);

 	regfunc("abs", fnabs, 1);

 	regfunc("round", fnround, 2);

 	regfunc("floor", fnfloor, 2);