cmd/pack: rewrite in Go

Replace the pack command, a C program, with a clean reimplementation in Go.
It does not need to reproduce the full feature set and it is no longer used by
the build chain, but has a role in looking inside archives created by the build
chain directly.

Since it's not in C, it is no longer build by dist, so remove it from cmd/dist and
make it a "tool" in cmd/go terminology.

Fixes #2705

R=rsc, dave, minux.ma, josharian
CC=golang-codereviews
https://golang.org/cl/52310044

src/cmd/dist/build.c

@@ -1300,7 +1300,6 @@ static char *buildorder[] = {
 
 	"cmd/addr2line",
 	"cmd/objdump",
-	"cmd/pack",
 	"cmd/prof",
 
 	"cmd/cc",  // must be before c
@@ -1379,7 +1378,6 @@ static char *cleantab[] = {
 	"cmd/gc",
 	"cmd/go",	
 	"cmd/objdump",
-	"cmd/pack",
 	"cmd/prof",
 	"lib9",
 	"libbio",

src/cmd/go/pkg.go

@@ -309,6 +309,7 @@ var goTools = map[string]targetDir{
 	"cmd/fix":                              toTool,
 	"cmd/link":                             toTool,
 	"cmd/nm":                               toTool,
+	"cmd/pack":                             toTool,
 	"cmd/yacc":                             toTool,
 	"code.google.com/p/go.tools/cmd/cover": toTool,
 	"code.google.com/p/go.tools/cmd/godoc": toBin,

src/cmd/pack/Makefile

-# Copyright 2012 The Go Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file.
-
-include ../../Make.dist

src/cmd/pack/ar.c

-// Inferno utils/iar/ar.c
-// http://code.google.com/p/inferno-os/source/browse/utils/iar/ar.c
-//
-//	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
-//	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
-//	Portions Copyright © 1997-1999 Vita Nuova Limited
-//	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
-//	Portions Copyright © 2004,2006 Bruce Ellis
-//	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
-//	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
-//	Portions Copyright © 2009 The Go Authors. All rights reserved.
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in
-// all copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
-// THE SOFTWARE.
-
-/*
- * ar - portable (ascii) format version
- */
-
-/* protect a couple of our names */
-#define select your_select
-#define rcmd your_rcmd
-
-#include <u.h>
-#include <libc.h>
-#include <bio.h>
-#include <mach.h>
-#include "../../libmach/obj.h"
-#include <ar.h>
-
-#undef select
-#undef rcmd
-
-/*
- *	The algorithm uses up to 3 temp files.  The "pivot member" is the
- *	archive member specified by and a, b, or i option.  The temp files are
- *	astart - contains existing members up to and including the pivot member.
- *	amiddle - contains new files moved or inserted behind the pivot.
- *	aend - contains the existing members that follow the pivot member.
- *	When all members have been processed, function 'install' streams the
- * 	temp files, in order, back into the archive.
- */
-
-typedef struct	Arsymref
-{
-	char	*name;
-	char *file;
-	int	type;
-	int	len;
-	vlong	offset;
-	struct	Arsymref *next;
-} Arsymref;
-
-typedef struct	Armember	/* Temp file entry - one per archive member */
-{
-	struct Armember	*next;
-	struct ar_hdr	hdr;
-	long		size;
-	long		date;
-	void		*member;
-} Armember;
-
-typedef	struct Arfile		/* Temp file control block - one per tempfile */
-{
-	char	*fname;		/* paging file name */
-	vlong	size;
-	Armember *head;		/* head of member chain */
-	Armember *tail;		/* tail of member chain */
-	Arsymref *sym;		/* head of defined symbol chain */
-} Arfile;
-
-typedef struct Hashchain
-{
-	char	*name;
-	char *file;
-	struct Hashchain *next;
-} Hashchain;
-
-#define	NHASH	1024
-
-/*
- *	macro to portably read/write archive header.
- *	'cmd' is read/write/Bread/Bwrite, etc.
- */
-#define	HEADER_IO(cmd, f, h)	cmd(f, h.name, sizeof(h.name)) != sizeof(h.name)\
-				|| cmd(f, h.date, sizeof(h.date)) != sizeof(h.date)\
-				|| cmd(f, h.uid, sizeof(h.uid)) != sizeof(h.uid)\
-				|| cmd(f, h.gid, sizeof(h.gid)) != sizeof(h.gid)\
-				|| cmd(f, h.mode, sizeof(h.mode)) != sizeof(h.mode)\
-				|| cmd(f, h.size, sizeof(h.size)) != sizeof(h.size)\
-				|| cmd(f, h.fmag, sizeof(h.fmag)) != sizeof(h.fmag)
-
-		/* constants and flags */
-char	*man =		"mrxtdpq";
-char	*opt =		"uvnbailogS";
-char	artemp[] =	"/tmp/vXXXXX";
-char	movtemp[] =	"/tmp/v1XXXXX";
-char	tailtemp[] =	"/tmp/v2XXXXX";
-char	symdef[] =	"__.GOSYMDEF";
-char	pkgdef[] =	"__.PKGDEF";
-
-int	aflag;				/* command line flags */
-int	bflag;
-int	cflag;
-int	gflag;
-int	oflag;
-int	uflag;
-int	vflag;
-int	Pflag;	/* remove leading file prefix */
-int	Sflag;	/* force mark Go package as safe */
-
-int	errors;
-
-Arfile *astart, *amiddle, *aend;	/* Temp file control block pointers */
-int	allobj = 1;			/* set when all members are object files of the same type */
-int	symdefsize;			/* size of symdef file */
-char	*pkgstmt;		/* string "package foo" */
-char	*objhdr;		/* string "go object darwin 386 release.2010-01-01 2345+" */
-int	dupfound;			/* flag for duplicate symbol */
-Hashchain	*hash[NHASH];		/* hash table of text symbols */
-
-#define	ARNAMESIZE	sizeof(astart->tail->hdr.name)
-
-char	poname[ARNAMESIZE+1];		/* name of pivot member */
-char	*file;				/* current file or member being worked on */
-Biobuf	bout;
-Biobuf bar;
-char	*prefix;
-int	pkgdefsafe;		/* was __.PKGDEF marked safe? */
-
-void	arcopy(Biobuf*, Arfile*, Armember*);
-int	arcreate(char*);
-void	arfree(Arfile*);
-void	arinsert(Arfile*, Armember*);
-void	*armalloc(int);
-char *arstrdup(char*);
-void	armove(Biobuf*, Arfile*, Armember*);
-void	arread(Biobuf*, Armember*);
-void	arstream(int, Arfile*);
-int	arwrite(int, Armember*);
-int	bamatch(char*, char*);
-int	duplicate(char*, char**);
-Armember *getdir(Biobuf*);
-void	getpkgdef(char**, int*);
-void	install(char*, Arfile*, Arfile*, Arfile*, int);
-void	loadpkgdata(char*, int);
-void	longt(Armember*);
-int	match(int, char**);
-void	mesg(int, char*);
-Arfile	*newtempfile(char*);
-Armember *newmember(void);
-void	objsym(Sym*, void*);
-int	openar(char*, int, int);
-void	pmode(long);
-void	rl(int);
-void	scanobj(Biobuf*, Arfile*, long);
-void	scanpkg(Biobuf*, long);
-void	select(int*, long);
-void	setcom(void(*)(char*, int, char**));
-void	skip(Biobuf*, vlong);
-void	checksafe(Biobuf*, vlong);
-int	symcomp(void*, void*);
-void	trim(char*, char*, int);
-void	usage(void);
-void	wrerr(void);
-void	wrsym(Biobuf*, long, Arsymref*);
-int	arread_cutprefix(Biobuf*, Armember*);
-
-void	rcmd(char*, int, char**);		/* command processing */
-void	dcmd(char*, int, char**);
-void	xcmd(char*, int, char**);
-void	tcmd(char*, int, char**);
-void	pcmd(char*, int, char**);
-void	mcmd(char*, int, char**);
-void	qcmd(char*, int, char**);
-void	(*comfun)(char*, int, char**);
-
-void
-main(int argc, char *argv[])
-{
-	char *cp;
-
-	Binit(&bout, 1, OWRITE);
-	if(argc < 3)
-		usage();
-	for (cp = argv[1]; *cp; cp++) {
-		switch(*cp) {
-		case 'a':	aflag = 1;	break;
-		case 'b':	bflag = 1;	break;
-		case 'c':	cflag = 1;	break;
-		case 'd':	setcom(dcmd);	break;
-		case 'g':	gflag = 1; break;
-		case 'i':	bflag = 1;	break;
-		case 'l':
-				strcpy(artemp, "vXXXXX");
-				strcpy(movtemp, "v1XXXXX");
-				strcpy(tailtemp, "v2XXXXX");
-				break;
-		case 'm':	setcom(mcmd);	break;
-		case 'o':	oflag = 1;	break;
-		case 'p':	setcom(pcmd);	break;
-		case 'q':	setcom(qcmd);	break;
-		case 'r':	setcom(rcmd);	break;
-		case 't':	setcom(tcmd);	break;
-		case 'u':	uflag = 1;	break;
-		case 'v':	vflag = 1;	break;
-		case 'x':	setcom(xcmd);	break;
-		case 'S':	Sflag = 1;  break;
-		case 'P':	Pflag = 1;  break;
-		default:
-			fprint(2, "pack: bad option `%c'\n", *cp);
-			exits("error");
-		}
-	}
-	if (aflag && bflag) {
-		fprint(2, "pack: only one of 'a' and 'b' can be specified\n");
-		usage();
-	}
-	if(aflag || bflag) {
-		trim(argv[2], poname, sizeof(poname));
-		argv++;
-		argc--;
-		if(argc < 3)
-			usage();
-	}
-	if(Pflag) {
-		if(argc < 4) {
-			fprint(2, "pack: P flag requires prefix argument\n");
-			usage();
-		}
-		prefix = argv[2];
-		argv++;
-		argc--;
-	}
-	if(comfun == 0) {
-		if(uflag == 0) {
-			fprint(2, "pack: one of [%s] must be specified\n", man);
-			usage();
-		}
-		setcom(rcmd);
-	}
-	cp = argv[2];
-	argc -= 3;
-	argv += 3;
-	(*comfun)(cp, argc, argv);	/* do the command */
-	if(errors && cflag)
-		remove(cp);
-	cp = 0;
-	while (argc--) {
-		if (*argv) {
-			fprint(2, "pack: %s not found\n", *argv);
-			cp = "error";
-		}
-		argv++;
-	}
-	if (errors)
-		cp = "error";
-	exits(cp);
-}
-/*
- *	select a command
- */
-void
-setcom(void (*fun)(char *, int, char**))
-{
-
-	if(comfun != 0) {
-		fprint(2, "pack: only one of [%s] allowed\n", man);
-		usage();
-	}
-	comfun = fun;
-}
-/*
- *	perform the 'r' and 'u' commands
- */
-void
-rcmd(char *arname, int count, char **files)
-{
-	int fd;
-	int i;
-	Arfile *ap;
-	Armember *bp;
-	Dir *d;
-	Biobuf *bfile;
-
-	fd = openar(arname, ORDWR, 1);
-	if (fd >= 0) {
-		Binit(&bar, fd, OREAD);
-		Bseek(&bar,seek(fd,0,1), 1);
-	}
-	astart = newtempfile(artemp);
-	ap = astart;
-	aend = 0;
-	for(i = 0; fd >= 0; i++) {
-		bp = getdir(&bar);
-		if (!bp)
-			break;
-		if (bamatch(file, poname)) {		/* check for pivot */
-			aend = newtempfile(tailtemp);
-			ap = aend;
-		}
-			/* pitch symdef file */
-		if (i == 0 && strcmp(file, symdef) == 0) {
-			skip(&bar, bp->size);
-			continue;
-		}
-			/* pitch pkgdef file but remember whether it was marked safe */
-		if (gflag && strcmp(file, pkgdef) == 0) {
-			checksafe(&bar, bp->size);
-			continue;
-		}
-		/*
-		 * the plan 9 ar treats count == 0 as equivalent
-		 * to listing all the archive's files on the command line:
-		 * it will try to open every file name in the archive
-		 * and copy that file into the archive if it exists.
-		 * for go we disable that behavior, because we use
-		 * r with no files to make changes to the archive itself,
-		 * using the S or P flags.
-		 */
-		if (!match(count, files)) {
-			scanobj(&bar, ap, bp->size);
-			arcopy(&bar, ap, bp);
-			continue;
-		}
-		bfile = Bopen(file, OREAD);
-		if (!bfile) {
-			if (count != 0) {
-				fprint(2, "pack: cannot open %s\n", file);
-				errors++;
-			}
-			scanobj(&bar, ap, bp->size);
-			arcopy(&bar, ap, bp);
-			continue;
-		}
-		d = dirfstat(Bfildes(bfile));
-		if(d == nil)
-			fprint(2, "pack: cannot stat %s: %r\n", file);
-		if (uflag && (d==nil || d->mtime <= bp->date)) {
-			scanobj(&bar, ap, bp->size);
-			arcopy(&bar, ap, bp);
-			Bterm(bfile);
-			free(d);
-			continue;
-		}
-		mesg('r', file);
-		skip(&bar, bp->size);
-		scanobj(bfile, ap, d->length);
-		free(d);
-		armove(bfile, ap, bp);
-		Bterm(bfile);
-	}
-	if(fd >= 0)
-		close(fd);
-		/* copy in remaining files named on command line */
-	for (i = 0; i < count; i++) {
-		file = files[i];
-		if(file == 0)
-			continue;
-		files[i] = 0;
-		bfile = Bopen(file, OREAD);
-		if (!bfile) {
-			fprint(2, "pack: cannot open %s\n", file);
-			errors++;
-		} else {
-			mesg('a', file);
-			d = dirfstat(Bfildes(bfile));
-			if (d == nil)
-				fprint(2, "can't stat %s\n", file);
-			else {
-				scanobj(bfile, astart, d->length);
-				armove(bfile, astart, newmember());
-				free(d);
-			}
-			Bterm(bfile);
-		}
-	}
-	if(fd < 0 && !cflag)
-		install(arname, astart, 0, aend, 1);	/* issue 'creating' msg */
-	else
-		install(arname, astart, 0, aend, 0);
-}
-
-void
-dcmd(char *arname, int count, char **files)
-{
-	Armember *bp;
-	int fd, i;
-
-	if (!count)
-		return;
-	fd = openar(arname, ORDWR, 0);
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	astart = newtempfile(artemp);
-	for (i = 0; bp = getdir(&bar); i++) {
-		if(match(count, files)) {
-			mesg('d', file);
-			skip(&bar, bp->size);
-			if (strcmp(file, symdef) == 0)
-				allobj = 0;
-		} else if (i == 0 && strcmp(file, symdef) == 0) {
-			skip(&bar, bp->size);
-		} else if (gflag && strcmp(file, pkgdef) == 0) {
-			skip(&bar, bp->size);
-		} else {
-			scanobj(&bar, astart, bp->size);
-			arcopy(&bar, astart, bp);
-		}
-	}
-	close(fd);
-	install(arname, astart, 0, 0, 0);
-}
-
-void
-xcmd(char *arname, int count, char **files)
-{
-	int fd, f, mode, i;
-	Armember *bp;
-	Dir dx;
-
-	fd = openar(arname, OREAD, 0);
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	i = 0;
-	while (bp = getdir(&bar)) {
-		if(count == 0 || match(count, files)) {
-			mode = strtoul(bp->hdr.mode, 0, 8) & 0777;
-			f = create(file, OWRITE, mode);
-			if(f < 0) {
-				fprint(2, "pack: %s cannot create\n", file);
-				skip(&bar, bp->size);
-			} else {
-				mesg('x', file);
-				arcopy(&bar, 0, bp);
-				if (write(f, bp->member, bp->size) < 0)
-					wrerr();
-				if(oflag && bp->date != 0) {
-					nulldir(&dx);
-					dx.atime = bp->date;
-					dx.mtime = bp->date;
-					if(dirwstat(file, &dx) < 0)
-						perror(file);
-				}
-				free(bp->member);
-				close(f);
-			}
-			free(bp);
-			if (count && ++i >= count)
-				break;
-		} else {
-			skip(&bar, bp->size);
-			free(bp);
-		}
-	}
-	close(fd);
-}
-void
-pcmd(char *arname, int count, char **files)
-{
-	int fd;
-	Armember *bp;
-
-	fd = openar(arname, OREAD, 0);
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	while(bp = getdir(&bar)) {
-		if(count == 0 || match(count, files)) {
-			if(vflag)
-				print("\n<%s>\n\n", file);
-			arcopy(&bar, 0, bp);
-			if (write(1, bp->member, bp->size) < 0)
-				wrerr();
-		} else
-			skip(&bar, bp->size);
-		free(bp);
-	}
-	close(fd);
-}
-void
-mcmd(char *arname, int count, char **files)
-{
-	int fd, i;
-	Arfile *ap;
-	Armember *bp;
-
-	if (count == 0)
-		return;
-	fd = openar(arname, ORDWR, 0);
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	astart = newtempfile(artemp);
-	amiddle = newtempfile(movtemp);
-	aend = 0;
-	ap = astart;
-	for (i = 0; bp = getdir(&bar); i++) {
-		if (bamatch(file, poname)) {
-			aend = newtempfile(tailtemp);
-			ap = aend;
-		}
-		if(match(count, files)) {
-			mesg('m', file);
-			scanobj(&bar, amiddle, bp->size);
-			arcopy(&bar, amiddle, bp);
-		} else if (ap == astart && i == 0 && strcmp(file, symdef) == 0) {
-			/*
-			 * pitch the symdef file if it is at the beginning
-			 * of the archive and we aren't inserting in front
-			 * of it (ap == astart).
-			 */
-			skip(&bar, bp->size);
-		} else if (ap == astart && gflag && strcmp(file, pkgdef) == 0) {
-			/*
-			 * pitch the pkgdef file if we aren't inserting in front
-			 * of it (ap == astart).
-			 */
-			skip(&bar, bp->size);
-		} else {
-			scanobj(&bar, ap, bp->size);
-			arcopy(&bar, ap, bp);
-		}
-	}
-	close(fd);
-	if (poname[0] && aend == 0)
-		fprint(2, "pack: %s not found - files moved to end.\n", poname);
-	install(arname, astart, amiddle, aend, 0);
-}
-void
-tcmd(char *arname, int count, char **files)
-{
-	int fd;
-	Armember *bp;
-	char name[ARNAMESIZE+1];
-
-	fd = openar(arname, OREAD, 0);
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	while(bp = getdir(&bar)) {
-		if(count == 0 || match(count, files)) {
-			if(vflag)
-				longt(bp);
-			trim(file, name, ARNAMESIZE);
-			Bprint(&bout, "%s\n", name);
-		}
-		skip(&bar, bp->size);
-		free(bp);
-	}
-	close(fd);
-}
-void
-qcmd(char *arname, int count, char **files)
-{
-	int fd, i;
-	Armember *bp;
-	Biobuf *bfile;
-
-	if(aflag || bflag) {
-		fprint(2, "pack: abi not allowed with q\n");
-		exits("error");
-	}
-	fd = openar(arname, ORDWR, 1);
-	if (fd < 0) {
-		if(!cflag)
-			fprint(2, "pack: creating %s\n", arname);
-		fd = arcreate(arname);
-	}
-	Binit(&bar, fd, OREAD);
-	Bseek(&bar,seek(fd,0,1), 1);
-	/* leave note group behind when writing archive; i.e. sidestep interrupts */
-	rfork(RFNOTEG);
-	Bseek(&bar, 0, 2);
-	bp = newmember();
-	for(i=0; i<count && files[i]; i++) {
-		file = files[i];
-		files[i] = 0;
-		bfile = Bopen(file, OREAD);
-		if(!bfile) {
-			fprint(2, "pack: cannot open %s\n", file);
-			errors++;
-		} else {
-			mesg('q', file);
-			armove(bfile, 0, bp);
-			if (!arwrite(fd, bp))
-				wrerr();
-			free(bp->member);
-			bp->member = 0;
-			Bterm(bfile);
-		}
-	}
-	free(bp);
-	close(fd);
-}
-
-/*
- *	does the object header line p match the last one we saw?
- *	update *lastp if it gets more specific.
- */
-int
-matchhdr(char *p, char **lastp)
-{
-	int n;
-	char *last;
-	
-	// no information?
-	last = *lastp;
-	if(last == nil) {
-		*lastp = strdup(p);
-		return 1;
-	}
-
-	// identical match?
-	if(strcmp(last, p) == 0)
-		return 1;
-
-	// last has extra fields
-	n = strlen(p);
-	if(n < strlen(last) && last[n] == ' ')
-		return 1;
-
-	// p has extra fields - save in last
-	n = strlen(last);
-	if(n < strlen(p) && p[n] == ' ') {
-		free(last);
-		*lastp = strdup(p);
-		return 1;
-	}
-	
-	return 0;
-}	
-
-/*
- *	extract the symbol references from an object file
- */
-void
-scanobj(Biobuf *b, Arfile *ap, long size)
-{
-	int goobject;
-	vlong offset;
-	uchar buf[4];
-	char *p;
-
-	if (!allobj)			/* non-object file encountered */
-		return;
-	offset = Boffset(b);
-
-	memset(buf, 0, sizeof buf);
-	Bread(b, buf, 4);
-	
-	/* maybe a foreign object file?  that's okay */
-	if((buf[0] == 0x7F && buf[1] == 'E' && buf[2] == 'L' && buf[3] == 'F') ||   // ELF
-	   (buf[0] == 0x4c && buf[1] == 0x01 || buf[0] == 0x64 && buf[1] == 0x86) || // Windows PE
-	   (buf[0] == 0xFE && buf[1] == 0xED && buf[2] == 0xFA && (buf[3]&~1) == 0xCE) ||  // Mach-O big-endian
-	   (buf[3] == 0xFE && buf[2] == 0xED && buf[1] == 0xFA && (buf[0]&~1) == 0xCE)) {  // Mach-O little-endian
-		Bseek(b, offset, 0);
-		return;
-	}
-	
-	goobject = 1;
-	Bseek(b, offset, 0);
-	p = Brdstr(b, '\n', 1);
-	
-	// After the go object header comes the Go metadata,
-	// followed by ! on a line by itself.  If this is not a Go object,
-	// the ! comes immediately.  Catch that so we can avoid
-	// the call to scanpkg below, since scanpkg assumes that the
-	// Go metadata is present.
-	if(BGETC(b) == '!')
-		goobject = 0;
-	Bseek(b, offset, 0);
-
-	if(p == nil || strncmp(p, "go object ", 10) != 0) {
-		fprint(2, "pack: malformed object file %s\n", file);
-		errors++;
-		free(p);
-		return;
-	}
-	
-	if (!matchhdr(p, &objhdr)) {
-		fprint(2, "pack: inconsistent object file %s: [%s] vs [%s]\n", file, p, objhdr);
-		errors++;
-		allobj = 0;
-		free(p);
-		return;
-	}
-	free(p);
-
-	USED(ap);
-	if (gflag && goobject) {
-		scanpkg(b, size);
-		Bseek(b, offset, 0);
-	}
-}
-
-/*
- *	does line contain substring (length-limited)
- */
-int
-strstrn(char *line, int len, char *sub)
-{
-	int i;
-	int sublen;
-
-	sublen = strlen(sub);
-	for (i = 0; i < len - sublen; i++)
-		if (memcmp(line+i, sub, sublen) == 0)
-			return 1;
-	return 0;
-}
-
-/*
- *	package import data
- */
-int	safe = 1;
-char*	pkgname;
-char*	importblock;
-
-void
-getpkgdef(char **datap, int *lenp)
-{
-	char *tag, *hdr;
-
-	if(pkgname == nil) {
-		pkgname = "__emptyarchive__";
-		importblock = "";
-	}
-	
-	tag = "";
-	if(safe || Sflag)
-		tag = "safe";
-
-	hdr = "empty archive";
-	if(objhdr != nil)
-		hdr = objhdr;
-
-	*datap = smprint("%s\nimport\n$$\npackage %s %s\n%s\n$$\n", hdr, pkgname, tag, importblock);
-	*lenp = strlen(*datap);
-}
-
-/*
- *	extract the package definition data from an object file.
- *	there can be only one.
- */
-void
-scanpkg(Biobuf *b, long size)
-{
-	long n;
-	int c;
-	long start, end, pkgsize;
-	char *data, *line, pkgbuf[1024], *pkg;
-	int first;
-
-	/*
-	 * scan until $$
-	 */
-	for (n=0; n<size; ) {
-		c = BGETC(b);
-		if(c == Beof)
-			break;
-		n++;
-		if(c != '$')
-			continue;
-		c = BGETC(b);
-		if(c == Beof)
-			break;
-		n++;
-		if(c != '$')
-			continue;
-		goto foundstart;
-	}
-	// fprint(2, "pack: warning: no package import section in %s\n", file);
-	if(b != &bar || !pkgdefsafe)
-		safe = 0;	// non-Go file (C or assembly)
-	return;
-
-foundstart:
-	/* found $$; skip rest of line */
-	while((c = BGETC(b)) != '\n')
-		if(c == Beof)
-			goto bad;
-
-	/* how big is it? */
-	first = 1;
-	start = end = 0;
-	for (n=0; n<size; n+=Blinelen(b)) {
-		line = Brdstr(b, '\n', 0);
-		if (line == nil)
-			goto bad;
-		if (first && strstrn(line, Blinelen(b), "package ")) {
-			if (Blinelen(b) > sizeof(pkgbuf)-1)
-				goto bad;
-			memmove(pkgbuf, line, Blinelen(b));
-			pkgbuf[Blinelen(b)] = '\0';
-			pkg = pkgbuf;
-			while(*pkg == ' ' || *pkg == '\t')
-				pkg++;
-			if(strncmp(pkg, "package ", 8) != 0)
-				goto bad;
-			pkg += 8;
-			data = pkg;
-			while(*pkg != ' ' && *pkg != '\n' && *pkg != '\0')
-				pkg++;
-			pkgname = armalloc(pkg - data + 1);
-			memmove(pkgname, data, pkg - data);
-			pkgname[pkg-data] = '\0';
-			if(strcmp(pkg, " safe\n") != 0 && (b != &bar || !pkgdefsafe))
-				safe = 0;
-			start = Boffset(b);  // after package statement
-			first = 0;
-			free(line);
-			continue;
-		}
-		if(line[0] == '$' && line[1] == '$') {
-			free(line);
-			goto foundend;
-		}
-		end = Boffset(b);  // before closing $$
-		free(line);
-	}
-bad:
-	fprint(2, "pack: bad package import section in %s\n", file);
-	errors++;
-	return;
-
-foundend:
-	if (start == 0)
-		return;
-	if (end == 0)
-		goto bad;
-	if(importblock != nil) {
-		fprint(2, "pack: multiple Go object files\n");
-		errors++;
-		return;
-	}
-	pkgsize = end-start;
-	data = armalloc(end - start + 1);
-	Bseek(b, start, 0);
-	if (Bread(b, data, pkgsize) != pkgsize) {
-		fprint(2, "pack: error reading package import section in %s\n", file);
-		errors++;
-		return;
-	}
-	data[end-start] = '\0';
-	importblock = data;
-}
-
-/*
- *	add text and data symbols to the symbol list
- */
-void
-objsym(Sym *s, void *p)
-{
-	int n;
-	Arsymref *as;
-	Arfile *ap;
-	char *ofile;
-
-	if (s->type != 'T' &&  s->type != 'D')
-		return;
-	ap = (Arfile*)p;
-	as = armalloc(sizeof(Arsymref));
-	as->offset = ap->size;
-	as->name = arstrdup(s->name);
-	as->file = arstrdup(file);
-	if(s->type == 'T' && duplicate(as->name, &ofile)) {
-		dupfound = 1;
-		fprint(2, "duplicate text symbol: %s and %s: %s\n", as->file, ofile, as->name);
-		errors++;
-		free(as->name);
-		free(as);
-		return;
-	}
-	as->type = s->type;
-	n = strlen(s->name);
-	symdefsize += 4+(n+1)+1;
-	as->len = n;
-	as->next = ap->sym;
-	ap->sym = as;
-}
-
-/*
- *	Check the symbol table for duplicate text symbols
- */
-int
-hashstr(char *name)
-{
-	uint32 h;
-	char *cp;
-
-	h = 0;
-	for(cp = name; *cp; h += *cp++)
-		h *= 1119;
-	return h & 0xfffffff;
-}
-
-int
-duplicate(char *name, char **ofile)
-{
-	Hashchain *p;
-	int h;
-
-	h = hashstr(name) % NHASH;
-
-	for(p = hash[h]; p; p = p->next)
-		if(strcmp(p->name, name) == 0) {
-			*ofile = p->file;
-			return 1;
-		}
-	p = armalloc(sizeof(Hashchain));
-	p->next = hash[h];
-	p->name = name;
-	p->file = file;
-	hash[h] = p;
-	*ofile = nil;
-	return 0;
-}
-
-/*
- *	open an archive and validate its header
- */
-int
-openar(char *arname, int mode, int errok)
-{
-	int fd;
-	char mbuf[SARMAG];
-
-	fd = open(arname, mode);
-	if(fd >= 0){
-		if(read(fd, mbuf, SARMAG) != SARMAG || strncmp(mbuf, ARMAG, SARMAG)) {
-			fprint(2, "pack: %s not in archive format\n", arname);
-			exits("error");
-		}
-	}else if(!errok){
-		fprint(2, "pack: cannot open %s: %r\n", arname);
-		exits("error");
-	}
-	return fd;
-}
-
-/*
- *	create an archive and set its header
- */
-int
-arcreate(char *arname)
-{
-	int fd;
-
-	fd = create(arname, OWRITE, 0664);
-	if(fd < 0){
-		fprint(2, "pack: cannot create %s: %r\n", arname);
-		exits("error");
-	}
-	if(write(fd, ARMAG, SARMAG) != SARMAG)
-		wrerr();
-	return fd;
-}
-
-/*
- *		error handling
- */
-void
-wrerr(void)
-{
-	perror("pack: write error");
-	exits("error");
-}
-
-void
-rderr(void)
-{
-	perror("pack: read error");
-	exits("error");
-}
-
-void
-phaseerr(int offset)
-{
-	fprint(2, "pack: phase error at offset %d\n", offset);
-	exits("error");
-}
-
-void
-usage(void)
-{
-	fprint(2, "usage: pack [%s][%s][P prefix] archive files ...\n", opt, man);
-	exits("error");
-}
-
-/*
- *	read the header for the next archive member
- */
-Armember *
-getdir(Biobuf *b)
-{
-	Armember *bp;
-	char *cp;
-	static char name[ARNAMESIZE+1];
-
-	bp = newmember();
-	if(HEADER_IO(Bread, b, bp->hdr)) {
-		free(bp);
-		return 0;
-	}
-	if(strncmp(bp->hdr.fmag, ARFMAG, sizeof(bp->hdr.fmag)))
-		phaseerr(Boffset(b));
-	strncpy(name, bp->hdr.name, sizeof(bp->hdr.name));
-	cp = name+sizeof(name)-1;
-	while(*--cp==' ')
-		;
-	cp[1] = '\0';
-	file = arstrdup(name);
-	bp->date = strtol(bp->hdr.date, 0, 0);
-	bp->size = strtol(bp->hdr.size, 0, 0);
-	return bp;
-}
-
-/*
- *	Copy the file referenced by fd to the temp file
- */
-void
-armove(Biobuf *b, Arfile *ap, Armember *bp)
-{
-	char *cp;
-	Dir *d;
-	vlong n;
-
-	d = dirfstat(Bfildes(b));
-	if (d == nil) {
-		fprint(2, "pack: cannot stat %s\n", file);
-		return;
-	}
-
-	trim(file, bp->hdr.name, sizeof(bp->hdr.name));
-	for (cp = strchr(bp->hdr.name, 0);		/* blank pad on right */
-		cp < bp->hdr.name+sizeof(bp->hdr.name); cp++)
-			*cp = ' ';
-	sprint(bp->hdr.date, "%-12ld", 0L);  // was d->mtime but removed for idempotent builds
-	sprint(bp->hdr.uid, "%-6d", 0);
-	sprint(bp->hdr.gid, "%-6d", 0);
-	sprint(bp->hdr.mode, "%-8lo", d->mode);
-	sprint(bp->hdr.size, "%-10lld", d->length);
-	strncpy(bp->hdr.fmag, ARFMAG, 2);
-	bp->size = d->length;
-	arread(b, bp);
-	n = bp->size;
-	if (n&1)
-		n++;
-	if (ap) {
-		arinsert(ap, bp);
-		ap->size += n+SAR_HDR;
-	}
-	free(d);
-}
-
-/*
- *	Copy the archive member at the current offset into the temp file.
- */
-void
-arcopy(Biobuf *b, Arfile *ap, Armember *bp)
-{
-	long n;
-
-	arread(b, bp);
-	n = bp->size;
-	if (n & 01)
-		n++;
-	if (ap) {
-		arinsert(ap, bp);
-		ap->size += n+SAR_HDR;
-	}
-}
-
-/*
- *	Skip an archive member
- */
-void
-skip(Biobuf *bp, vlong len)
-{
-	if (len & 01)
-		len++;
-	Bseek(bp, len, 1);
-}
-
-void
-checksafe(Biobuf *bp, vlong len)
-{
-	char *p;
-	vlong end;
-
-	if (len & 01)
-		len++;
-	end = Boffset(bp) + len;
-
-	p = Brdline(bp, '\n');
-	if(p == nil || strncmp(p, "go object ", 10) != 0)
-		goto done;
-	for(;;) {
-		p = Brdline(bp, '\n');
-		if(p == nil || Boffset(bp) >= end)
-			goto done;
-		if(strncmp(p, "$$\n", 3) == 0)
-			break;
-	}
-	p = Brdline(bp, '\n');
-	if(p == nil || Boffset(bp) > end)
-		goto done;
-	if(Blinelen(bp) > 8+6 && strncmp(p, "package ", 8) == 0 && strncmp(p+Blinelen(bp)-6, " safe\n", 6) == 0)
-		pkgdefsafe = 1;
-
-done:
-	Bseek(bp, end, 0);
-}
-
-/*
- *	Stream the three temp files to an archive
- */
-void
-install(char *arname, Arfile *astart, Arfile *amiddle, Arfile *aend, int createflag)
-{
-	int fd;
-
-	if(allobj && dupfound) {
-		fprint(2, "%s not changed\n", arname);
-		return;
-	}
-	/* leave note group behind when copying back; i.e. sidestep interrupts */
-	rfork(RFNOTEG);
-
-	if(createflag)
-		fprint(2, "pack: creating %s\n", arname);
-	fd = arcreate(arname);
-
-	if(allobj)
-		rl(fd);
-
-	if (astart) {
-		arstream(fd, astart);
-		arfree(astart);
-	}
-	if (amiddle) {
-		arstream(fd, amiddle);
-		arfree(amiddle);
-	}
-	if (aend) {
-		arstream(fd, aend);
-		arfree(aend);
-	}
-	close(fd);
-}
-
-void
-rl(int fd)
-{
-	Biobuf b;
-	char *cp;
-	struct ar_hdr a;
-	long len;
-	int headlen;
-	char *pkgdefdata;
-	int pkgdefsize;
-
-	pkgdefdata = nil;
-	pkgdefsize = 0;
-
-	Binit(&b, fd, OWRITE);
-	Bseek(&b,seek(fd,0,1), 0);
-
-	len = symdefsize;
-	if(len&01)
-		len++;
-	sprint(a.date, "%-12ld", 0L);  // time(0)
-	sprint(a.uid, "%-6d", 0);
-	sprint(a.gid, "%-6d", 0);
-	sprint(a.mode, "%-8lo", 0644L);
-	sprint(a.size, "%-10ld", len);
-	strncpy(a.fmag, ARFMAG, 2);
-	strcpy(a.name, symdef);
-	for (cp = strchr(a.name, 0);		/* blank pad on right */
-		cp < a.name+sizeof(a.name); cp++)
-			*cp = ' ';
-	if(HEADER_IO(Bwrite, &b, a))
-			wrerr();
-
-	headlen = Boffset(&b);
-	len += headlen;
-	if (gflag) {
-		getpkgdef(&pkgdefdata, &pkgdefsize);
-		len += SAR_HDR + pkgdefsize;
-		if (len & 1)
-			len++;
-	}
-	if (astart) {
-		wrsym(&b, len, astart->sym);
-		len += astart->size;
-	}
-	if(amiddle) {
-		wrsym(&b, len, amiddle->sym);
-		len += amiddle->size;
-	}
-	if(aend)
-		wrsym(&b, len, aend->sym);
-
-	if(symdefsize&0x01)
-		BPUTC(&b, 0);
-
-	if (gflag) {
-		len = pkgdefsize;
-		sprint(a.date, "%-12ld", 0L);  // time(0)
-		sprint(a.uid, "%-6d", 0);
-		sprint(a.gid, "%-6d", 0);
-		sprint(a.mode, "%-8lo", 0644L);
-		sprint(a.size, "%-10ld", (len + 1) & ~1);
-		strncpy(a.fmag, ARFMAG, 2);
-		strcpy(a.name, pkgdef);
-		for (cp = strchr(a.name, 0);		/* blank pad on right */
-			cp < a.name+sizeof(a.name); cp++)
-				*cp = ' ';
-		if(HEADER_IO(Bwrite, &b, a))
-				wrerr();
-
-		if (Bwrite(&b, pkgdefdata, pkgdefsize) != pkgdefsize)
-			wrerr();
-		if(len&0x01)
-			BPUTC(&b, 0);
-	}
-	Bterm(&b);
-}
-
-/*
- *	Write the defined symbols to the symdef file
- */
-void
-wrsym(Biobuf *bp, long offset, Arsymref *as)
-{
-	int off;
-
-	while(as) {
-		BPUTC(bp, as->type);
-		off = as->offset+offset;
-		BPUTLE4(bp, off);
-		if (Bwrite(bp, as->name, as->len+1) != as->len+1)
-			wrerr();
-		as = as->next;
-	}
-}
-
-/*
- *	Check if the archive member matches an entry on the command line.
- */
-int
-match(int count, char **files)
-{
-	int i;
-	char name[ARNAMESIZE+1];
-
-	for(i=0; i<count; i++) {
-		if(files[i] == 0)
-			continue;
-		trim(files[i], name, ARNAMESIZE);
-		if(strncmp(name, file, ARNAMESIZE) == 0) {
-			file = files[i];
-			files[i] = 0;
-			return 1;
-		}
-	}
-	return 0;
-}
-
-/*
- *	compare the current member to the name of the pivot member
- */
-int
-bamatch(char *file, char *pivot)
-{
-	static int state = 0;
-
-	switch(state)
-	{
-	case 0:			/* looking for position file */
-		if (aflag) {
-			if (strncmp(file, pivot, ARNAMESIZE) == 0)
-				state = 1;
-		} else if (bflag) {
-			if (strncmp(file, pivot, ARNAMESIZE) == 0) {
-				state = 2;	/* found */
-				return 1;
-			}
-		}
-		break;
-	case 1:			/* found - after previous file */
-		state = 2;
-		return 1;
-	case 2:			/* already found position file */
-		break;
-	}
-	return 0;
-}
-
-/*
- *	output a message, if 'v' option was specified
- */
-void
-mesg(int c, char *file)
-{
-
-	if(vflag)
-		Bprint(&bout, "%c - %s\n", c, file);
-}
-
-/*
- *	isolate file name by stripping leading directories and trailing slashes
- */
-void
-trim(char *s, char *buf, int n)
-{
-	char *p, *q;
-
-	for(;;) {
-		p = strrchr(s, '/');
-		q = strrchr(s, '\\');
-		if (q > p)
-			p = q;
-		if (!p) {		/* no (back)slash in name */
-			strncpy(buf, s, n);
-			return;
-		}
-		if (p[1] != 0) {	/* p+1 is first char of file name */
-			strncpy(buf, p+1, n);
-			return;
-		}
-		*p = 0;			/* strip trailing (back)slash */
-	}
-}
-
-/*
- *	utilities for printing long form of 't' command
- */
-#define	SUID	04000
-#define	SGID	02000
-#define	ROWN	0400
-#define	WOWN	0200
-#define	XOWN	0100
-#define	RGRP	040
-#define	WGRP	020
-#define	XGRP	010
-#define	ROTH	04
-#define	WOTH	02
-#define	XOTH	01
-#define	STXT	01000
-
-void
-longt(Armember *bp)
-{
-	char *cp;
-
-	pmode(strtoul(bp->hdr.mode, 0, 8));
-	Bprint(&bout, "%3ld/%1ld", strtol(bp->hdr.uid, 0, 0), strtol(bp->hdr.gid, 0, 0));
-	Bprint(&bout, "%7ld", bp->size);
-	cp = ctime(bp->date);
-	Bprint(&bout, " %-12.12s %-4.4s ", cp+4, cp+24);
-}
-
-int	m1[] = { 1, ROWN, 'r', '-' };
-int	m2[] = { 1, WOWN, 'w', '-' };
-int	m3[] = { 2, SUID, 's', XOWN, 'x', '-' };
-int	m4[] = { 1, RGRP, 'r', '-' };
-int	m5[] = { 1, WGRP, 'w', '-' };
-int	m6[] = { 2, SGID, 's', XGRP, 'x', '-' };
-int	m7[] = { 1, ROTH, 'r', '-' };
-int	m8[] = { 1, WOTH, 'w', '-' };
-int	m9[] = { 2, STXT, 't', XOTH, 'x', '-' };
-
-int	*m[] = { m1, m2, m3, m4, m5, m6, m7, m8, m9};
-
-void
-pmode(long mode)
-{
-	int **mp;
-
-	for(mp = &m[0]; mp < &m[9];)
-		select(*mp++, mode);
-}
-
-void
-select(int *ap, long mode)
-{
-	int n;
-
-	n = *ap++;
-	while(--n>=0 && (mode&*ap++)==0)
-		ap++;
-	BPUTC(&bout, *ap);
-}
-
-/*
- *	Temp file I/O subsystem.  We attempt to cache all three temp files in
- *	core.  When we run out of memory we spill to disk.
- *	The I/O model assumes that temp files:
- *		1) are only written on the end
- *		2) are only read from the beginning
- *		3) are only read after all writing is complete.
- *	The architecture uses one control block per temp file.  Each control
- *	block anchors a chain of buffers, each containing an archive member.
- */
-Arfile *
-newtempfile(char *name)		/* allocate a file control block */
-{
-	Arfile *ap;
-
-	ap = armalloc(sizeof(Arfile));
-	ap->fname = name;
-	return ap;
-}
-
-Armember *
-newmember(void)			/* allocate a member buffer */
-{
-	return armalloc(sizeof(Armember));
-}
-
-void
-arread(Biobuf *b, Armember *bp)	/* read an image into a member buffer */
-{
-	int i;
-	vlong off;
-
-	bp->member = armalloc(bp->size);
-	
-	// If P flag is set, let arread_cutprefix try.
-	// If it succeeds, we're done.  If not, fall back
-	// to a direct copy.
-	off = Boffset(b);
-	if(Pflag && arread_cutprefix(b, bp))
-		return;
-	Bseek(b, off, 0);
-
-	i = Bread(b, bp->member, bp->size);
-	if (i < 0) {
-		free(bp->member);
-		bp->member = 0;
-		rderr();
-	}
-	if(bp->size&1)
-		BGETC(b);
-}
-
-/*
- * insert a member buffer into the member chain
- */
-void
-arinsert(Arfile *ap, Armember *bp)
-{
-	bp->next = 0;
-	if (!ap->tail)
-		ap->head = bp;
-	else
-		ap->tail->next = bp;
-	ap->tail = bp;
-}
-
-/*
- *	stream the members in a temp file to the file referenced by 'fd'.
- */
-void
-arstream(int fd, Arfile *ap)
-{
-	Armember *bp;
-
-	/* dump the in-core buffers */
-	for (bp = ap->head; bp; bp = bp->next) {
-		if (!arwrite(fd, bp))
-			wrerr();
-	}
-}
-
-/*
- *	write a member to 'fd'.
- */
-int
-arwrite(int fd, Armember *bp)
-{
-	int len;
-
-	if(HEADER_IO(write, fd, bp->hdr))
-		return 0;
-	len = bp->size;
-	if (len & 01)
-		len++;
-	if (write(fd, bp->member, len) != len)
-		return 0;
-	return 1;
-}
-
-void
-arfree(Arfile *ap)		/* free a member buffer */
-{
-	Armember *bp, *next;
-
-	for (bp = ap->head; bp; bp = next) {
-		next = bp->next;
-		if (bp->member)
-			free(bp->member);
-		free(bp);
-	}
-	free(ap);
-}
-
-/*
- *	allocate space for a control block or member buffer.  if the malloc
- *	fails we try to reclaim space by spilling previously allocated
- *	member buffers.
- */
-void *
-armalloc(int n)
-{
-	char *cp;
-
-	// bump so that arwrite can do the same
-	if(n&1)
-		n++;
-
-	cp = malloc(n);
-	if (cp) {
-		memset(cp, 0, n);
-		return cp;
-	}
-	fprint(2, "pack: out of memory\n");
-	exits("malloc");
-	return 0;
-}
-
-char *
-arstrdup(char *s)
-{
-	char *t;
-
-	t = armalloc(strlen(s) + 1);
-	strcpy(t, s);
-	return t;
-}
-
-#define isdelim(c) ((c) == '/' || (c) == '\\')
-
-/*
- *	check if p is start of windows full path, like C:\ or c:/.
- *	return 1 if so. also set drive parameter to its
- *	upper-case drive letter.
- */
-int
-iswinpathstart(char *p, char *drive)
-{
-	if('A' <= p[0] || p[0] <= 'Z')
-		*drive = p[0];
-	else if('a' <= p[0] || p[0] <= 'z')
-		*drive = p[0] - ('a' - 'A');
-	else
-		return 0;
-	return p[1] == ':' && isdelim(p[2]);
-}
-
-/*
- *	copy b into bp->member but rewrite object
- *	during copy to drop prefix from all file names.
- *	return 1 if b was recognized as an object file
- *	and copied successfully, 0 otherwise.
- */
-int
-arread_cutprefix(Biobuf *b, Armember *bp)
-{
-	// TODO: reimplement
-	USED(b);
-	USED(bp);
-
-	return 0;
-}

src/cmd/pack/doc.go

-// Copyright 2009 The Go Authors. All rights reserved.
+// Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build ignore
-
 /*
 
-Pack is a variant of the Plan 9 ar tool.  The original is documented at
+Pack is a simple version of the traditional Unix ar tool.
+It implements only the operations needed by Go.
 
-	http://plan9.bell-labs.com/magic/man2html/1/ar
+Usage:
+	go tool pack op file.a [name...]
 
-It adds a special Go-specific section __.PKGDEF that collects all the
-Go type information from the files in the archive; that section is
-used by the compiler when importing the package during compilation.
+Pack applies the operation to the archive, using the names as arguments to the operation.
 
-Usage:
-	go tool pack [uvnbailogS][mrxtdpq][P prefix] archive files ...
+The operation op is given by one of these letters:
+
+	p	print files from the archive
+	r	append files (from the file system) to the archive
+	t	list files from the archive
+	x	extract files from the archive
+
+For the p, t, and x commands, listing no names on the command line
+causes the operation to apply to all files in the archive.
 
-The new option 'g' causes pack to maintain the __.PKGDEF section
-as files are added to the archive.
+In contrast to Unix ar, the r operation always appends to the archive,
+even if a file with the given name already exists in the archive. In this way
+pack's r operation is more like Unix ar's rq operation.
 
-The new option 'S' forces pack to mark the archive as safe.
+Adding the letter v to an operation, as in pv or rv, enables verbose operation:
+For the p command, each file is prefixed by the name on a line by itself.
+For the r command, names are printed as files are added.
+For the t command, the listing includes additional file metadata.
+For the x command, names are printed as files are extracted.
 
-The new option 'P' causes pack to remove the given prefix
-from file names in the line number information in object files
-that are already stored in or added to the archive.
 */
 package main

src/cmd/pack/pack.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+)
+
+/*
+The archive format is:
+
+First, on a line by itself
+	!<arch>
+
+Then zero or more file records. Each file record has a fixed-size one-line header
+followed by data bytes followed by an optional padding byte. The header is:
+
+	%-16s%-12d%-6d%-6d%-8o%-10d`
+	name mtime uid gid mode size
+
+(note the trailing backquote). The %-16s here means at most 16 *bytes* of
+the name, and if shorter, space padded on the right.
+*/
+
+const usageMessage = `Usage: pack op file.a [name....]
+Where op is one of prtx optionally followed by v for verbose output.
+For more information, run
+	godoc cmd/pack`
+
+func usage() {
+	fmt.Fprintln(os.Stderr, usageMessage)
+	os.Exit(2)
+}
+
+func main() {
+	log.SetFlags(0)
+	// need "pack op archive" at least.
+	if len(os.Args) < 3 {
+		usage()
+	}
+	setOp(os.Args[1])
+	var ar *Archive
+	switch op {
+	case 'p':
+		ar = archive(os.Args[2], os.O_RDONLY, os.Args[3:])
+		ar.scan(ar.printContents)
+	case 'r':
+		ar = archive(os.Args[2], os.O_RDWR, os.Args[3:])
+		ar.scan(ar.skipContents)
+		ar.addFiles()
+	case 't':
+		ar = archive(os.Args[2], os.O_RDONLY, os.Args[3:])
+		ar.scan(ar.tableOfContents)
+	case 'x':
+		ar = archive(os.Args[2], os.O_RDONLY, os.Args[3:])
+		ar.scan(ar.extractContents)
+	default:
+		usage()
+	}
+	if len(ar.files) > 0 {
+		log.Fatalf("pack: file %q not in archive", ar.files[0])
+	}
+}
+
+// The unusual ancestry means the arguments are not Go-standard.
+// These variables hold the decoded operation specified by the first argument.
+// op holds the operation we are doing (prtx).
+// verbose tells whether the 'v' option was specified.
+var (
+	op      rune
+	verbose bool
+)
+
+// setOp parses the operation string (first argument).
+func setOp(arg string) {
+	for _, r := range arg {
+		switch r {
+		case 'p', 'r', 't', 'x':
+			if op != 0 {
+				// At most one can be set.
+				usage()
+			}
+			op = r
+		case 'v':
+			if verbose {
+				// Can be set only once.
+				usage()
+			}
+			verbose = true
+		default:
+			usage()
+		}
+	}
+}
+
+const (
+	arHeader    = "!<arch>\n"
+	entryHeader = "%s%-12d%-6d%-6d%-8o%-10d`\n"
+	// In entryHeader the first entry, the name, is always printed as 16 bytes right-padded.
+	entryLen   = 16 + 12 + 6 + 6 + 8 + 10 + 1 + 1
+	timeFormat = "Jan _2 15:04 2006"
+)
+
+// An Archive represents an open archive file. It is always scanned sequentially
+// from start to end, without backing up.
+type Archive struct {
+	fd    *os.File // Open file descriptor.
+	files []string // Explicit list of files to be processed.
+}
+
+// archive opens (or if necessary creates) the named archive.
+func archive(name string, mode int, files []string) *Archive {
+	fd, err := os.OpenFile(name, mode, 0)
+	if err != nil && mode == os.O_RDWR && os.IsNotExist(err) {
+		fd, err = create(name)
+	}
+	if err != nil {
+		log.Fatal("pack: ", err)
+	}
+	mustBeArchive(fd)
+	return &Archive{
+		fd:    fd,
+		files: files,
+	}
+}
+
+// create creates and initializes an archive that does not exist.
+func create(name string) (*os.File, error) {
+	fd, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return nil, err
+	}
+	fmt.Fprint(fd, arHeader)
+	fd.Seek(0, 0)
+	return fd, nil
+}
+
+// mustBeArchive verifies the header of the file. It assumes the file offset
+// is 0 coming in, and leaves it positioned immediately after the header.
+func mustBeArchive(fd *os.File) {
+	buf := make([]byte, len(arHeader))
+	_, err := io.ReadFull(fd, buf)
+	if err != nil || string(buf) != arHeader {
+		log.Fatal("pack: file is not an archive: bad header")
+	}
+}
+
+// An Entry is the internal representation of the per-file header information of one entry in the archive.
+type Entry struct {
+	name  string
+	mtime int64
+	uid   int
+	gid   int
+	mode  os.FileMode
+	size  int64
+}
+
+func (e *Entry) String() string {
+	return fmt.Sprintf("%s %6d/%-6d %12d %s %s",
+		(e.mode & 0777).String(),
+		e.uid,
+		e.gid,
+		e.size,
+		time.Unix(e.mtime, 0).Format(timeFormat),
+		e.name)
+}
+
+// readMetadata reads and parses the metadata for the next entry in the archive.
+func (ar *Archive) readMetadata() *Entry {
+	buf := make([]byte, entryLen)
+	_, err := io.ReadFull(ar.fd, buf)
+	if err == io.EOF {
+		// No entries left.
+		return nil
+	}
+	if err != nil || buf[entryLen-2] != '`' || buf[entryLen-1] != '\n' {
+		log.Fatal("pack: file is not an archive: bad entry")
+	}
+	entry := new(Entry)
+	entry.name = strings.TrimRight(string(buf[:16]), " ")
+	if len(entry.name) == 0 {
+		log.Fatal("pack: file is not an archive: bad name")
+	}
+	buf = buf[16:]
+	str := string(buf)
+	get := func(width, base, bitsize int) int64 {
+		v, err := strconv.ParseInt(strings.TrimRight(str[:width], " "), base, bitsize)
+		if err != nil {
+			log.Fatal("pack: file is not an archive: bad number in entry: ", err)
+		}
+		str = str[width:]
+		return v
+	}
+	// %-16s%-12d%-6d%-6d%-8o%-10d`
+	entry.mtime = get(12, 10, 64)
+	entry.uid = int(get(6, 10, 32))
+	entry.gid = int(get(6, 10, 32))
+	entry.mode = os.FileMode(get(8, 8, 32))
+	entry.size = get(10, 10, 64)
+	return entry
+}
+
+// scan scans the archive and executes the specified action on each entry.
+// When action returns, the file offset is at the start of the next entry.
+func (ar *Archive) scan(action func(*Entry)) {
+	for {
+		entry := ar.readMetadata()
+		if entry == nil {
+			break
+		}
+		action(entry)
+	}
+}
+
+// listEntry prints to standard output a line describing the entry.
+func listEntry(ar *Archive, entry *Entry, verbose bool) {
+	if verbose {
+		fmt.Fprintf(stdout, "%s\n", entry)
+	} else {
+		fmt.Fprintf(stdout, "%s\n", entry.name)
+	}
+}
+
+// output copies the entry to the specified writer.
+func (ar *Archive) output(entry *Entry, w io.Writer) {
+	n, err := io.Copy(w, io.LimitReader(ar.fd, entry.size))
+	if err != nil {
+		log.Fatal("pack: ", err)
+	}
+	if n != entry.size {
+		log.Fatal("pack: short file")
+	}
+	if entry.size&1 == 1 {
+		_, err := ar.fd.Seek(1, 1)
+		if err != nil {
+			log.Fatal("pack: ", err)
+		}
+	}
+}
+
+// skip skips the entry without reading it.
+func (ar *Archive) skip(entry *Entry) {
+	size := entry.size
+	if size&1 == 1 {
+		size++
+	}
+	_, err := ar.fd.Seek(size, 1)
+	if err != nil {
+		log.Fatal("pack: ", err)
+	}
+}
+
+// match reports whether the entry matches the argument list.
+// If it does, it also drops the file from the to-be-processed list.
+func (ar *Archive) match(entry *Entry) bool {
+	if len(ar.files) == 0 {
+		return true
+	}
+	for i, name := range ar.files {
+		if entry.name == name {
+			copy(ar.files[i:], ar.files[i+1:])
+			ar.files = ar.files[:len(ar.files)-1]
+			return true
+		}
+	}
+	return false
+}
+
+// addFiles adds files to the archive. The archive is known to be
+// sane and we are positioned at the end. No attempt is made
+// to check for existing files.
+func (ar *Archive) addFiles() {
+	if len(ar.files) == 0 {
+		usage()
+	}
+	for _, file := range ar.files {
+		if verbose {
+			fmt.Printf("%s\n", file)
+		}
+		fd, err := os.Open(file)
+		if err != nil {
+			log.Fatal("pack: ", err)
+		}
+		ar.addFile(fd)
+	}
+	ar.files = nil
+}
+
+// FileLike abstracts the few methods we need, so we can test without needing real files.
+type FileLike interface {
+	Name() string
+	Stat() (os.FileInfo, error)
+	Read([]byte) (int, error)
+	Close() error
+}
+
+// addFile adds a single file to the archive
+func (ar *Archive) addFile(fd FileLike) {
+	defer fd.Close()
+	// Format the entry.
+	// First, get its info.
+	info, err := fd.Stat()
+	if err != nil {
+		log.Fatal("pack: ", err)
+	}
+	// mtime, uid, gid are all zero so repeated builds produce identical output.
+	mtime := int64(0)
+	uid := 0
+	gid := 0
+	n, err := fmt.Fprintf(ar.fd, entryHeader, exactly16Bytes(info.Name()), mtime, uid, gid, info.Mode(), info.Size())
+	if err != nil || n != entryLen {
+		log.Fatal("pack: writing entry header: ", err)
+	}
+	n64, err := io.Copy(ar.fd, fd)
+	if err != nil {
+		log.Fatal("pack: writing file: ", err)
+	}
+	if n64 != info.Size() {
+		log.Fatal("pack: writing file: wrote %d bytes; file is size %d", n64, info.Size())
+	}
+	if info.Size()&1 == 1 {
+		_, err = ar.fd.Write([]byte{0})
+		if err != nil {
+			log.Fatal("pack: writing archive: ", err)
+		}
+	}
+}
+
+// exactly16Bytes truncates the string if necessary so it is at most 16 bytes long,
+// then pads the result with spaces to be exactly 16 bytes.
+// Fmt uses runes for its width calculation, but we need bytes in the entry header.
+func exactly16Bytes(s string) string {
+	for len(s) > 16 {
+		_, wid := utf8.DecodeLastRuneInString(s)
+		s = s[:len(s)-wid]
+	}
+	const sixteenSpaces = "                "
+	s += sixteenSpaces[:16-len(s)]
+	return s
+}
+
+// Finally, the actual commands. Each is an action.
+
+// can be modified for testing.
+var stdout io.Writer = os.Stdout
+
+// printContents implements the 'p' command.
+func (ar *Archive) printContents(entry *Entry) {
+	if ar.match(entry) {
+		if verbose {
+			listEntry(ar, entry, false)
+		}
+		ar.output(entry, stdout)
+	} else {
+		ar.skip(entry)
+	}
+}
+
+// skipContents implements the first part of the 'r' command.
+// It just scans the archive to make sure it's intact.
+func (ar *Archive) skipContents(entry *Entry) {
+	ar.skip(entry)
+}
+
+// tableOfContents implements the 't' command.
+func (ar *Archive) tableOfContents(entry *Entry) {
+	if ar.match(entry) {
+		listEntry(ar, entry, verbose)
+	}
+	ar.skip(entry)
+}
+
+// extractContents implements the 'x' command.
+func (ar *Archive) extractContents(entry *Entry) {
+	if ar.match(entry) {
+		if verbose {
+			listEntry(ar, entry, false)
+		}
+		fd, err := os.OpenFile(entry.name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, entry.mode)
+		if err != nil {
+			log.Fatal("pack: ", err)
+		}
+		ar.output(entry, fd)
+		fd.Close()
+	} else {
+		ar.skip(entry)
+	}
+}

src/cmd/pack/pack_test.go

+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+	"unicode/utf8"
+)
+
+func TestExactly16Bytes(t *testing.T) {
+	var tests = []string{
+		"",
+		"a",
+		"日本語",
+		"1234567890123456",
+		"12345678901234567890",
+		"1234567890123本語4567890",
+		"12345678901234日本語567890",
+		"123456789012345日本語67890",
+		"1234567890123456日本語7890",
+		"1234567890123456日本語7日本語890",
+	}
+	for _, str := range tests {
+		got := exactly16Bytes(str)
+		if len(got) != 16 {
+			t.Errorf("exactly16Bytes(%q) is %q, length %d", str, got, len(got))
+		}
+		// Make sure it is full runes.
+		for _, c := range got {
+			if c == utf8.RuneError {
+				t.Errorf("exactly16Bytes(%q) is %q, has partial rune", str, got)
+			}
+		}
+	}
+}
+
+// tmpDir creates a temporary directory and returns its name.
+func tmpDir(t *testing.T) string {
+	name, err := ioutil.TempDir("", "pack")
+	if err != nil {
+		t.Fatal(err)
+	}
+	return name
+}
+
+// Test that we can create an archive, write to it, and get the same contents back.
+// Tests the rv and then the pv command on a new archive.
+func TestCreate(t *testing.T) {
+	dir := tmpDir(t)
+	defer os.RemoveAll(dir)
+	name := filepath.Join(dir, "pack.a")
+	ar := archive(name, os.O_RDWR, nil)
+	// Add an entry by hand.
+	ar.addFile(helloFile.Reset())
+	ar.fd.Close()
+	// Now check it.
+	ar = archive(name, os.O_RDONLY, []string{helloFile.name})
+	var buf bytes.Buffer
+	stdout = &buf
+	verbose = true
+	defer func() {
+		stdout = os.Stdout
+		verbose = false
+	}()
+	ar.scan(ar.printContents)
+	ar.fd.Close()
+	result := buf.String()
+	// Expect verbose output plus file contents.
+	expect := fmt.Sprintf("%s\n%s", helloFile.name, helloFile.contents)
+	if result != expect {
+		t.Fatalf("expected %q got %q", expect, result)
+	}
+}
+
+// Test that we can create an archive, put some files in it, and get back a correct listing.
+// Tests the tv command.
+func TestTableOfContents(t *testing.T) {
+	dir := tmpDir(t)
+	defer os.RemoveAll(dir)
+	name := filepath.Join(dir, "pack.a")
+	ar := archive(name, os.O_RDWR, nil)
+	// Add some entries by hand.
+	ar.addFile(helloFile.Reset())
+	ar.addFile(goodbyeFile.Reset())
+	ar.fd.Close()
+	// Now print it.
+	ar = archive(name, os.O_RDONLY, nil)
+	var buf bytes.Buffer
+	stdout = &buf
+	verbose = true
+	defer func() {
+		stdout = os.Stdout
+		verbose = false
+	}()
+	ar.scan(ar.tableOfContents)
+	ar.fd.Close()
+	result := buf.String()
+	// Expect verbose listing.
+	expect := fmt.Sprintf("%s\n%s\n", helloFile.Entry(), goodbyeFile.Entry())
+	if result != expect {
+		t.Fatalf("expected %q got %q", expect, result)
+	}
+	// Do it again without verbose.
+	verbose = false
+	buf.Reset()
+	ar = archive(name, os.O_RDONLY, nil)
+	ar.scan(ar.tableOfContents)
+	ar.fd.Close()
+	result = buf.String()
+	// Expect non-verbose listing.
+	expect = fmt.Sprintf("%s\n%s\n", helloFile.name, goodbyeFile.name)
+	if result != expect {
+		t.Fatalf("expected %q got %q", expect, result)
+	}
+}
+
+// Test that we can create an archive, put some files in it, and get back a file.
+// Tests the x command.
+func TestExtract(t *testing.T) {
+	dir := tmpDir(t)
+	defer os.RemoveAll(dir)
+	name := filepath.Join(dir, "pack.a")
+	ar := archive(name, os.O_RDWR, nil)
+	// Add some entries by hand.
+	ar.addFile(helloFile.Reset())
+	ar.addFile(goodbyeFile.Reset())
+	ar.fd.Close()
+	// Now extract one file. We chdir to the directory of the archive for simplicity.
+	pwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal("os.Getwd: ", err)
+	}
+	err = os.Chdir(dir)
+	if err != nil {
+		t.Fatal("os.Chdir: ", err)
+	}
+	defer func() {
+		err := os.Chdir(pwd)
+		if err != nil {
+			t.Fatal("os.Chdir: ", err)
+		}
+	}()
+	ar = archive(name, os.O_RDONLY, []string{goodbyeFile.name})
+	ar.scan(ar.extractContents)
+	ar.fd.Close()
+	data, err := ioutil.ReadFile(goodbyeFile.name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Expect contents of file.
+	result := string(data)
+	expect := goodbyeFile.contents
+	if result != expect {
+		t.Fatalf("expected %q got %q", expect, result)
+	}
+}
+
+// Fake implementation of files.
+
+var helloFile = &FakeFile{
+	name:     "hello",
+	contents: "hello world", // 11 bytes, an odd number.
+	mode:     0644,
+}
+
+var goodbyeFile = &FakeFile{
+	name:     "goodbye",
+	contents: "Sayonara, Jim", // 13 bytes, another odd number.
+	mode:     0644,
+}
+
+// FakeFile implements FileLike and also os.FileInfo.
+type FakeFile struct {
+	name     string
+	contents string
+	mode     os.FileMode
+	offset   int
+}
+
+// Reset prepares a FakeFile for reuse.
+func (f *FakeFile) Reset() *FakeFile {
+	f.offset = 0
+	return f
+}
+
+// FileLike methods.
+
+func (f *FakeFile) Name() string {
+	// A bit of a cheat: we only have a basename, so that's also ok for FileInfo.
+	return f.name
+}
+
+func (f *FakeFile) Stat() (os.FileInfo, error) {
+	return f, nil
+}
+
+func (f *FakeFile) Read(p []byte) (int, error) {
+	if f.offset >= len(f.contents) {
+		return 0, io.EOF
+	}
+	n := copy(p, f.contents[f.offset:])
+	f.offset += n
+	return n, nil
+}
+
+func (f *FakeFile) Close() error {
+	return nil
+}
+
+// os.FileInfo methods.
+
+func (f *FakeFile) Size() int64 {
+	return int64(len(f.contents))
+}
+
+func (f *FakeFile) Mode() os.FileMode {
+	return f.mode
+}
+
+func (f *FakeFile) ModTime() time.Time {
+	return time.Time{}
+}
+
+func (f *FakeFile) IsDir() bool {
+	return false
+}
+
+func (f *FakeFile) Sys() interface{} {
+	return nil
+}
+
+// Special helpers.
+
+func (f *FakeFile) Entry() *Entry {
+	return &Entry{
+		name:  f.name,
+		mtime: 0, // Defined to be zero.
+		uid:   0, // Ditto.
+		gid:   0, // Ditto.
+		mode:  f.mode,
+		size:  int64(len(f.contents)),
+	}
+}