cb.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>
#include <bio.h>
#include "cb.h"
#include "cbtype.h"

void
main(int argc, char *argv[])
{
	Biobuf stdin, stdout;

	while (--argc > 0 && (*++argv)[0] == '-'){
		switch ((*argv)[1]){
		case 's':
			strict = 1;
			continue;
		case 'j':
			join = 1;
			continue;
		case 'l':
			if((*argv)[2] != '\0'){
				maxleng = atoi( &((*argv)[2]) );
			}
			else{
				maxleng = atoi(*++argv);
				argc--;
			}
			maxtabs = maxleng/TABLENG - 2;
			maxleng -= (maxleng + 5)/10;
			continue;
		default:
			fprint(2, "cb: illegal option %c\n", *argv[1]);
			exits("boom");
		}
	}
	Binit(&stdout, 1, OWRITE);
	output = &stdout;
	if (argc <= 0){
		Binit(&stdin, 0, OREAD);
		input = &stdin;
		work();
	} else {
		while (argc-- > 0){
			if ((input = Bopen( *argv, OREAD)) == 0){
				fprint(2, "cb: cannot open input file %s\n", *argv);
				exits("boom");
			}
			work();
			argv++;
		}
	}
	exits(0);
}
void
work(void)
{
	int c, cc;
	struct keyw *lptr;
	char *pt;
	int ct;

	while ((c = getch()) != Beof){
		switch (c){
		case '{':
			if ((lptr = lookup(lastlook,p)) != 0){
				if (lptr->type == ELSE)gotelse();
				else if(lptr->type == DO)gotdo();
				else if(lptr->type == STRUCT)structlev++;
			}
			if(++clev >= &ind[CLEVEL-1]){
				fprint(2,"too many levels of curly brackets\n");
				clev = &ind[CLEVEL-1];
			}
			clev->pdepth = 0;
			clev->tabs = (clev-1)->tabs;
			clearif(clev);
			if(strict && clev->tabs > 0)
				putspace(' ',NO);
			putch(c,NO);
			getnl();
			if(keyflag == DATADEF){
				OUT;
			}
			else {
				OUTK;
			}
			clev->tabs++;
			pt = getnext(0);		/* to handle initialized structures */
			if(*pt == '{'){		/* hide one level of {} */
				while((c=getch()) != '{')
					if(c == Beof)error("{");
				putch(c,NO);
				if(strict){
					putch(' ',NO);
					eatspace();
				}
				keyflag = SINIT;
			}
			continue;
		case '}':
			pt = getnext(0);		/* to handle initialized structures */
			if(*pt == ','){
				if(strict){
					putspace(' ',NO);
					eatspace();
				}
				putch(c,NO);
				putch(*pt,NO);
				*pt = '\0';
				ct = getnl();
				pt = getnext(0);
				if(*pt == '{'){
					OUT;
					while((cc = getch()) != '{')
						if(cc == Beof)error("}");
					putch(cc,NO);
					if(strict){
						putch(' ',NO);
						eatspace();
					}
					getnext(0);
					continue;
				}
				else if(strict || ct){
					OUT;
				}
				continue;
			}
			else if(keyflag == SINIT && *pt == '}'){
				if(strict)
					putspace(' ',NO);
				putch(c,NO);
				getnl();
				OUT;
				keyflag = DATADEF;
				*pt = '\0';
				pt = getnext(0);
			}
			outs(clev->tabs);
			if(--clev < ind)clev = ind;
			ptabs(clev->tabs);
			putch(c,NO);
			lbegin = 0;
			lptr=lookup(pt,lastplace+1);
			c = *pt;
			if(*pt == ';' || *pt == ','){
				putch(*pt,NO);
				*pt = '\0';
				lastplace=pt;
			}
			ct = getnl();
			if((dolevel && clev->tabs <= dotabs[dolevel]) || (structlev )
			    || (lptr != 0 &&lptr->type == ELSE&& clev->pdepth == 0)){
				if(c == ';'){
					OUTK;
				}
				else if(strict || (lptr != 0 && lptr->type == ELSE && ct == 0)){
					putspace(' ',NO);
					eatspace();
				}
				else if(lptr != 0 && lptr->type == ELSE){
					OUTK;
				}
				if(structlev){
					structlev--;
					keyflag = DATADEF;
				}
			}
			else {
				OUTK;
				if(strict && clev->tabs == 0){
					if((c=getch()) != '\n'){
						Bputc(output, '\n');
						Bputc(output, '\n');
						unget(c);
					}
					else {
						lineno++;
						Bputc(output, '\n');
						if((c=getch()) != '\n')unget(c);
						else lineno++;
						Bputc(output, '\n');
					}
				}
			}
			if(lptr != 0 && lptr->type == ELSE && clev->pdepth != 0){
				UNBUMP;
			}
			if(lptr == 0 || lptr->type != ELSE){
				clev->iflev = 0;
				if(dolevel && docurly[dolevel] == NO && clev->tabs == dotabs[dolevel]+1)
					clev->tabs--;
				else if(clev->pdepth != 0){
					UNBUMP;
				}
			}
			continue;
		case '(':
			paren++;
			if ((lptr = lookup(lastlook,p)) != 0){
				if(!(lptr->type == TYPE || lptr->type == STRUCT))keyflag=KEYWORD;
				if (strict){
					putspace(lptr->punc,NO);
					opflag = 1;
				}
				putch(c,NO);
				if (lptr->type == IF)gotif();
			}
			else {
				putch(c,NO);
				lastlook = p;
				opflag = 1;
			}
			continue;
		case ')':
			if(--paren < 0)paren = 0;
			putch(c,NO);
			if((lptr = lookup(lastlook,p)) != 0){
				if(lptr->type == TYPE || lptr->type == STRUCT)
					opflag = 1;
			}
			else if(keyflag == DATADEF)opflag = 1;
			else opflag = 0;
			outs(clev->tabs);
			pt = getnext(1);
			if ((ct = getnl()) == 1 && !strict){
				if(dolevel && clev->tabs <= dotabs[dolevel])
					resetdo();
				if(clev->tabs > 0 && (paren != 0 || keyflag == 0)){
					if(join){
						eatspace();
						putch(' ',YES);
						continue;
					} else {
						OUT;
						split = 1;
						continue;
					}
				}
				else if(clev->tabs > 0 && *pt != '{'){
					BUMP;
				}
				OUTK;
			}
			else if(strict){
				if(clev->tabs == 0){
					if(*pt != ';' && *pt != ',' && *pt != '(' && *pt != '['){
						OUTK;
					}
				}
				else {
					if(keyflag == KEYWORD && paren == 0){
						if(dolevel && clev->tabs <= dotabs[dolevel]){
							resetdo();
							eatspace();
							continue;
						}
						if(*pt != '{'){
							BUMP;
							OUTK;
						}
						else {
							*pt='\0';
							eatspace();
							unget('{');
						}
					}
					else if(ct){
						if(paren){
							if(join){
								eatspace();
							} else {
								split = 1;
								OUT;
							}
						}
						else {
							OUTK;
						}
					}
				}
			}
			else if(dolevel && clev->tabs <= dotabs[dolevel])
				resetdo();
			continue;
		case ' ':
		case '\t':
			if ((lptr = lookup(lastlook,p)) != 0){
				if(!(lptr->type==TYPE||lptr->type==STRUCT))
					keyflag = KEYWORD;
				else if(paren == 0)keyflag = DATADEF;
				if(strict){
					if(lptr->type != ELSE){
						if(lptr->type == TYPE){
							if(paren != 0)putch(' ',YES);
						}
						else
							putch(lptr->punc,NO);
						eatspace();
					}
				}
				else putch(c,YES);
				switch(lptr->type){
				case CASE:
					outs(clev->tabs-1);
					continue;
				case ELSE:
					pt = getnext(1);
					eatspace();
					if((cc = getch()) == '\n' && !strict){
						unget(cc);
					}
					else {
						unget(cc);
						if(checkif(pt))continue;
					}
					gotelse();
					if(strict) unget(c);
					if(getnl() == 1 && !strict){
						OUTK;
						if(*pt != '{'){
							BUMP;
						}
					}
					else if(strict){
						if(*pt != '{'){
							OUTK;
							BUMP;
						}
					}
					continue;
				case IF:
					gotif();
					continue;
				case DO:
					gotdo();
					pt = getnext(1);
					if(*pt != '{'){
						eatallsp();
						OUTK;
						docurly[dolevel] = NO;
						dopdepth[dolevel] = clev->pdepth;
						clev->pdepth = 0;
						clev->tabs++;
					}
					continue;
				case TYPE:
					if(paren)continue;
					if(!strict)continue;
					gottype(lptr);
					continue;
				case STRUCT:
					gotstruct();
					continue;
				}
			}
			else if (lbegin == 0 || p > string) 
				if(strict)
					putch(c,NO);
				else putch(c,YES);
			continue;
		case ';':
			putch(c,NO);
			if(paren != 0){
				if(strict){
					putch(' ',YES);
					eatspace();
				}
				opflag = 1;
				continue;
			}
			outs(clev->tabs);
			pt = getnext(0);
			lptr=lookup(pt,lastplace+1);
			if(lptr == 0 || lptr->type != ELSE){
				clev->iflev = 0;
				if(clev->pdepth != 0){
					UNBUMP;
				}
				if(dolevel && docurly[dolevel] == NO && clev->tabs <= dotabs[dolevel]+1)
					clev->tabs--;
/*
				else if(clev->pdepth != 0){
					UNBUMP;
				}
*/
			}
			getnl();
			OUTK;
			continue;
		case '\n':
			if ((lptr = lookup(lastlook,p)) != 0){
				pt = getnext(1);
				if (lptr->type == ELSE){
					if(strict)
						if(checkif(pt))continue;
					gotelse();
					OUTK;
					if(*pt != '{'){
						BUMP;
					}
				}
				else if(lptr->type == DO){
					OUTK;
					gotdo();
					if(*pt != '{'){
						docurly[dolevel] = NO;
						dopdepth[dolevel] = clev->pdepth;
						clev->pdepth = 0;
						clev->tabs++;
					}
				}
				else {
					OUTK;
					if(lptr->type == STRUCT)gotstruct();
				}
			}
			else if(p == string)Bputc(output, '\n');
			else {
				if(clev->tabs > 0 &&(paren != 0 || keyflag == 0)){
					if(join){
						putch(' ',YES);
						eatspace();
						continue;
					} else {
						OUT;
						split = 1;
						continue;
					}
				}
				else if(keyflag == KEYWORD){
					OUTK;
					continue;
				}
				OUT;
			}
			continue;
		case '"':
		case '\'':
			putch(c,NO);
			while ((cc = getch()) != c){
				if(cc == Beof)
					error("\" or '");
				putch(cc,NO);
				if (cc == '\\'){
					putch(getch(),NO);
				}
				if (cc == '\n'){
					outs(clev->tabs);
					lbegin = 1;
					count = 0;
				}
			}
			putch(cc,NO);
			opflag=0;
			if (getnl() == 1){
				unget('\n');
			}
			continue;
		case '\\':
			putch(c,NO);
			putch(getch(),NO);
			continue;
		case '?':
			question = 1;
			gotop(c);
			continue;
		case ':':
			if ((cc = getch()) == ':') {
				putch(c,NO);
				putch(cc,NO);
				continue;
			}
			unget(cc);
			if (question == 1){
				question = 0;
				gotop(c);
				continue;
			}
			putch(c,NO);
			if(structlev)continue;
			if ((lptr = lookup(lastlook,p)) != 0){
				if (lptr->type == CASE)outs(clev->tabs - 1);
			}
			else {
				lbegin = 0;
				outs(clev->tabs);
			}
			getnl();
			OUTK;
			continue;
		case '/':
			if ((cc = getch()) == '/') {
				putch(c,NO);
				putch(cc,NO);
				cpp_comment(YES);
				OUT;
				lastlook = 0;
				continue;
			}
			else if (cc != '*') {
				unget(cc);
				gotop(c);
				continue;
			}
			putch(c,NO);
			putch(cc,NO);
			cc = comment(YES);
			if(getnl() == 1){
				if(cc == 0){
					OUT;
				}
				else {
					outs(0);
					Bputc(output, '\n');
					lbegin = 1;
					count = 0;
				}
				lastlook = 0;
			}
			continue;