tar/util.c - third_party/libarchive - Git at Google

 /*-
  * Copyright (c) 2003-2007 Tim Kientzle
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "bsdtar_platform.h"
 __FBSDID("$FreeBSD: src/usr.bin/tar/util.c,v 1.23 2008/12/15 06:00:25 kientzle Exp $");

 #ifdef HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>  /* Linux doesn't define mode_t, etc. in sys/stat.h. */
 #endif
 #include <ctype.h>
 #ifdef HAVE_ERRNO_H
 #include <errno.h>
 #endif
 #ifdef HAVE_STDARG_H
 #include <stdarg.h>
 #endif
 #include <stdio.h>
 #ifdef HAVE_STDLIB_H
 #include <stdlib.h>
 #endif
 #ifdef HAVE_STRING_H
 #include <string.h>
 #endif
 #ifdef HAVE_WCTYPE_H
 #include <wctype.h>
 #else
 /* If we don't have wctype, we need to hack up some version of iswprint(). */
 #define iswprint isprint
 #endif

 #include "bsdtar.h"

 static void	bsdtar_vwarnc(struct bsdtar *, int code,
 		    const char *fmt, va_list ap);
 static size_t	bsdtar_expand_char(char *, size_t, char);
 static const char *strip_components(const char *path, int elements);

 /* TODO:  Hack up a version of mbtowc for platforms with no wide
  * character support at all.  I think the following might suffice,
  * but it needs careful testing.
  * #if !HAVE_MBTOWC
  * #define mbtowc(wcp, p, n) ((*wcp = *p), 1)
  * #endif
  */

 /*
  * Print a string, taking care with any non-printable characters.
  *
  * Note that we use a stack-allocated buffer to receive the formatted
  * string if we can.  This is partly performance (avoiding a call to
  * malloc()), partly out of expedience (we have to call vsnprintf()
  * before malloc() anyway to find out how big a buffer we need; we may
  * as well point that first call at a small local buffer in case it
  * works), but mostly for safety (so we can use this to print messages
  * about out-of-memory conditions).
  */

 void
 safe_fprintf(FILE *f, const char *fmt, ...)
 {
 	char fmtbuff_stack[256]; /* Place to format the printf() string. */
 	char outbuff[256]; /* Buffer for outgoing characters. */
 	char *fmtbuff_heap; /* If fmtbuff_stack is too small, we use malloc */
 	char *fmtbuff;  /* Pointer to fmtbuff_stack or fmtbuff_heap. */
 	int fmtbuff_length;
 	int length;
 	va_list ap;
 	const char *p;
 	unsigned i;
 	wchar_t wc;
 	char try_wc;

 	/* Use a stack-allocated buffer if we can, for speed and safety. */
 	fmtbuff_heap = NULL;
 	fmtbuff_length = sizeof(fmtbuff_stack);
 	fmtbuff = fmtbuff_stack;

 	/* Try formatting into the stack buffer. */
 	va_start(ap, fmt);
 	length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);
 	va_end(ap);

 	/* If the result was too large, allocate a buffer on the heap. */
 	if (length >= fmtbuff_length) {
 		fmtbuff_length = length+1;
 		fmtbuff_heap = malloc(fmtbuff_length);

 		/* Reformat the result into the heap buffer if we can. */
 		if (fmtbuff_heap != NULL) {
 			fmtbuff = fmtbuff_heap;
 			va_start(ap, fmt);
 			length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);
 			va_end(ap);
 		} else {
 			/* Leave fmtbuff pointing to the truncated
 			 * string in fmtbuff_stack. */
 			length = sizeof(fmtbuff_stack) - 1;
 		}
 	}

 	/* Note: mbrtowc() has a cleaner API, but mbtowc() seems a bit
 	 * more portable, so we use that here instead. */
 	mbtowc(NULL, NULL, 0); /* Reset the shift state. */

 	/* Write data, expanding unprintable characters. */
 	p = fmtbuff;
 	i = 0;
 	try_wc = 1;
 	while (*p != '\0') {
 		int n;

 		/* Convert to wide char, test if the wide
 		 * char is printable in the current locale. */
 		if (try_wc && (n = mbtowc(&wc, p, length)) != -1) {
 			length -= n;
 			if (iswprint(wc) && wc != L'\\') {
 				/* Printable, copy the bytes through. */
 				while (n-- > 0)
 					outbuff[i++] = *p++;
 			} else {
 				/* Not printable, format the bytes. */
 				while (n-- > 0)
 					i += bsdtar_expand_char(
 					    outbuff, i, *p++);
 			}
 		} else {
 			/* After any conversion failure, don't bother
 			 * trying to convert the rest. */
 			i += bsdtar_expand_char(outbuff, i, *p++);
 			try_wc = 0;
 		}

 		/* If our output buffer is full, dump it and keep going. */
 		if (i > (sizeof(outbuff) - 20)) {
 			outbuff[i++] = '\0';
 			fprintf(f, "%s", outbuff);
 			i = 0;
 		}
 	}
 	outbuff[i++] = '\0';
 	fprintf(f, "%s", outbuff);

 	/* If we allocated a heap-based formatting buffer, free it now. */
 	if (fmtbuff_heap != NULL)
 		free(fmtbuff_heap);
 }

 /*
  * Render an arbitrary sequence of bytes into printable ASCII characters.
  */
 static size_t
 bsdtar_expand_char(char *buff, size_t offset, char c)
 {
 	size_t i = offset;

 	if (isprint(c) && c != '\\')
 		buff[i++] = c;
 	else {
 		buff[i++] = '\\';
 		switch (c) {
 		case '\a': buff[i++] = 'a'; break;
 		case '\b': buff[i++] = 'b'; break;
 		case '\f': buff[i++] = 'f'; break;
 		case '\n': buff[i++] = 'n'; break;
 #if '\r' != '\n'
 		/* On some platforms, \n and \r are the same. */
 		case '\r': buff[i++] = 'r'; break;
 #endif
 		case '\t': buff[i++] = 't'; break;
 		case '\v': buff[i++] = 'v'; break;
 		case '\\': buff[i++] = '\\'; break;
 		default:
 			sprintf(buff + i, "%03o", 0xFF & (int)c);
 			i += 3;
 		}
 	}

 	return (i - offset);
 }

 static void
 bsdtar_vwarnc(struct bsdtar *bsdtar, int code, const char *fmt, va_list ap)
 {
 	fprintf(stderr, "%s: ", bsdtar->progname);
 	vfprintf(stderr, fmt, ap);
 	if (code != 0)
 		fprintf(stderr, ": %s", strerror(code));
 	fprintf(stderr, "\n");
 }

 void
 bsdtar_warnc(struct bsdtar *bsdtar, int code, const char *fmt, ...)
 {
 	va_list ap;

 	va_start(ap, fmt);
 	bsdtar_vwarnc(bsdtar, code, fmt, ap);
 	va_end(ap);
 }

 void
 bsdtar_errc(struct bsdtar *bsdtar, int eval, int code, const char *fmt, ...)
 {
 	va_list ap;

 	va_start(ap, fmt);
 	bsdtar_vwarnc(bsdtar, code, fmt, ap);
 	va_end(ap);
 	exit(eval);
 }

 int
 yes(const char *fmt, ...)
 {
 	char buff[32];
 	char *p;
 	ssize_t l;

 	va_list ap;
 	va_start(ap, fmt);
 	vfprintf(stderr, fmt, ap);
 	va_end(ap);
 	fprintf(stderr, " (y/N)? ");
 	fflush(stderr);

 	l = read(2, buff, sizeof(buff) - 1);
 	if (l <= 0)
 		return (0);
 	buff[l] = 0;

 	for (p = buff; *p != '\0'; p++) {
 		if (isspace(0xff & (int)*p))
 			continue;
 		switch(*p) {
 		case 'y': case 'Y':
 			return (1);
 		case 'n': case 'N':
 			return (0);
 		default:
 			return (0);
 		}
 	}

 	return (0);
 }

 /*
  * Read lines from file and do something with each one.  If option_null
  * is set, lines are terminated with zero bytes; otherwise, they're
  * terminated with newlines.
  *
  * This uses a self-sizing buffer to handle arbitrarily-long lines.
  * If the "process" function returns non-zero for any line, this
  * function will return non-zero after attempting to process all
  * remaining lines.
  */
 int
 process_lines(struct bsdtar *bsdtar, const char *pathname,
     int (*process)(struct bsdtar *, const char *))
 {
 	FILE *f;
 	char *buff, *buff_end, *line_start, *line_end, *p;
 	size_t buff_length, new_buff_length, bytes_read, bytes_wanted;
 	int separator;
 	int ret;

 	separator = bsdtar->option_null ? '\0' : '\n';
 	ret = 0;

 	if (strcmp(pathname, "-") == 0)
 		f = stdin;
 	else
 		f = fopen(pathname, "r");
 	if (f == NULL)
 		bsdtar_errc(bsdtar, 1, errno, "Couldn't open %s", pathname);
 	buff_length = 8192;
 	buff = malloc(buff_length);
 	if (buff == NULL)
 		bsdtar_errc(bsdtar, 1, ENOMEM, "Can't read %s", pathname);
 	line_start = line_end = buff_end = buff;
 	for (;;) {
 		/* Get some more data into the buffer. */
 		bytes_wanted = buff + buff_length - buff_end;
 		bytes_read = fread(buff_end, 1, bytes_wanted, f);
 		buff_end += bytes_read;
 		/* Process all complete lines in the buffer. */
 		while (line_end < buff_end) {
 			if (*line_end == separator) {
 				*line_end = '\0';
 				if ((*process)(bsdtar, line_start) != 0)
 					ret = -1;
 				line_start = line_end + 1;
 				line_end = line_start;
 			} else
 				line_end++;
 		}
 		if (feof(f))
 			break;
 		if (ferror(f))
 			bsdtar_errc(bsdtar, 1, errno,
 			    "Can't read %s", pathname);
 		if (line_start > buff) {
 			/* Move a leftover fractional line to the beginning. */
 			memmove(buff, line_start, buff_end - line_start);
 			buff_end -= line_start - buff;
 			line_end -= line_start - buff;
 			line_start = buff;
 		} else {
 			/* Line is too big; enlarge the buffer. */
 			new_buff_length = buff_length * 2;
 			if (new_buff_length <= buff_length)
 				bsdtar_errc(bsdtar, 1, ENOMEM,
 				    "Line too long in %s", pathname);
 			buff_length = new_buff_length;
 			p = realloc(buff, buff_length);
 			if (p == NULL)
 				bsdtar_errc(bsdtar, 1, ENOMEM,
 				    "Line too long in %s", pathname);
 			buff_end = p + (buff_end - buff);
 			line_end = p + (line_end - buff);
 			line_start = buff = p;
 		}
 	}
 	/* At end-of-file, handle the final line. */
 	if (line_end > line_start) {
 		*line_end = '\0';
 		if ((*process)(bsdtar, line_start) != 0)
 			ret = -1;
 	}
 	free(buff);
 	if (f != stdin)
 		fclose(f);
 	return (ret);
 }

 /*-
  * The logic here for -C <dir> attempts to avoid
  * chdir() as long as possible.  For example:
  * "-C /foo -C /bar file"          needs chdir("/bar") but not chdir("/foo")
  * "-C /foo -C bar file"           needs chdir("/foo/bar")
  * "-C /foo -C bar /file1"         does not need chdir()
  * "-C /foo -C bar /file1 file2"   needs chdir("/foo/bar") before file2
  *
  * The only correct way to handle this is to record a "pending" chdir
  * request and combine multiple requests intelligently until we
  * need to process a non-absolute file.  set_chdir() adds the new dir
  * to the pending list; do_chdir() actually executes any pending chdir.
  *
  * This way, programs that build tar command lines don't have to worry
  * about -C with non-existent directories; such requests will only
  * fail if the directory must be accessed.
  */
 void
 set_chdir(struct bsdtar *bsdtar, const char *newdir)
 {
 	if (newdir[0] == '/') {
 		/* The -C /foo -C /bar case; dump first one. */
 		free(bsdtar->pending_chdir);
 		bsdtar->pending_chdir = NULL;
 	}
 	if (bsdtar->pending_chdir == NULL)
 		/* Easy case: no previously-saved dir. */
 		bsdtar->pending_chdir = strdup(newdir);
 	else {
 		/* The -C /foo -C bar case; concatenate */
 		char *old_pending = bsdtar->pending_chdir;
 		size_t old_len = strlen(old_pending);
 		bsdtar->pending_chdir = malloc(old_len + strlen(newdir) + 2);
 		if (old_pending[old_len - 1] == '/')
 			old_pending[old_len - 1] = '\0';
 		if (bsdtar->pending_chdir != NULL)
 			sprintf(bsdtar->pending_chdir, "%s/%s",
 			    old_pending, newdir);
 		free(old_pending);
 	}
 	if (bsdtar->pending_chdir == NULL)
 		bsdtar_errc(bsdtar, 1, errno, "No memory");
 }

 void
 do_chdir(struct bsdtar *bsdtar)
 {
 	if (bsdtar->pending_chdir == NULL)
 		return;

 	if (chdir(bsdtar->pending_chdir) != 0) {
 		bsdtar_errc(bsdtar, 1, 0, "could not chdir to '%s'\n",
 		    bsdtar->pending_chdir);
 	}
 	free(bsdtar->pending_chdir);
 	bsdtar->pending_chdir = NULL;
 }

 const char *
 strip_components(const char *path, int elements)
 {
 	const char *p = path;

 	while (elements > 0) {
 		switch (*p++) {
 		case '/':
 			elements--;
 			path = p;
 			break;
 		case '\0':
 			/* Path is too short, skip it. */
 			return (NULL);
 		}
 	}

 	while (*path == '/')
 	       ++path;
 	if (*path == '\0')
 	       return (NULL);

 	return (path);
 }

 /*
  * Handle --strip-components and any future path-rewriting options.
  * Returns non-zero if the pathname should not be extracted.
  *
  * TODO: Support pax-style regex path rewrites.
  */
 int
 edit_pathname(struct bsdtar *bsdtar, struct archive_entry *entry)
 {
 	const char *name = archive_entry_pathname(entry);
 #if HAVE_REGEX_H
 	char *subst_name;
 #endif
 	int r;

 #if HAVE_REGEX_H
 	r = apply_substitution(bsdtar, name, &subst_name, 0);
 	if (r == -1) {
 		bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
 		return 1;
 	}
 	if (r == 1) {
 		archive_entry_copy_pathname(entry, subst_name);
 		if (*subst_name == '\0') {
 			free(subst_name);
 			return -1;
 		} else
 			free(subst_name);
 		name = archive_entry_pathname(entry);
 	}

 	if (archive_entry_hardlink(entry)) {
 		r = apply_substitution(bsdtar, archive_entry_hardlink(entry), &subst_name, 1);
 		if (r == -1) {
 			bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
 			return 1;
 		}
 		if (r == 1) {
 			archive_entry_copy_hardlink(entry, subst_name);
 			free(subst_name);
 		}
 	}
 	if (archive_entry_symlink(entry) != NULL) {
 		r = apply_substitution(bsdtar, archive_entry_symlink(entry), &subst_name, 1);
 		if (r == -1) {
 			bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
 			return 1;
 		}
 		if (r == 1) {
 			archive_entry_copy_symlink(entry, subst_name);
 			free(subst_name);
 		}
 	}
 #endif

 	/* Strip leading dir names as per --strip-components option. */
 	if (bsdtar->strip_components > 0) {
 		const char *linkname = archive_entry_hardlink(entry);

 		name = strip_components(name, bsdtar->strip_components);
 		if (name == NULL)
 			return (1);

 		if (linkname != NULL) {
 			linkname = strip_components(linkname,
 			    bsdtar->strip_components);
 			if (linkname == NULL)
 				return (1);
 			archive_entry_copy_hardlink(entry, linkname);
 		}
 	}

 	/* Strip redundant leading '/' characters. */
 	while (name[0] == '/' && name[1] == '/')
 		name++;

 	/* Strip leading '/' unless user has asked us not to. */
 	if (name[0] == '/' && !bsdtar->option_absolute_paths) {
 		/* Generate a warning the first time this happens. */
 		if (!bsdtar->warned_lead_slash) {
 			bsdtar_warnc(bsdtar, 0,
 			    "Removing leading '/' from member names");
 			bsdtar->warned_lead_slash = 1;
 		}
 		name++;
 		/* Special case: Stripping leading '/' from "/" yields ".". */
 		if (*name == '\0')
 			name = ".";
 	}

 	/* Safely replace name in archive_entry. */
 	if (name != archive_entry_pathname(entry)) {
 		char *q = strdup(name);
 		archive_entry_copy_pathname(entry, q);
 		free(q);
 	}
 	return (0);
 }

 /*
  * Like strcmp(), but try to be a little more aware of the fact that
  * we're comparing two paths.  Right now, it just handles leading
  * "./" and trailing '/' specially, so that "a/b/" == "./a/b"
  *
  * TODO: Make this better, so that "./a//b/./c/" == "a/b/c"
  * TODO: After this works, push it down into libarchive.
  * TODO: Publish the path normalization routines in libarchive so
  * that bsdtar can normalize paths and use fast strcmp() instead
  * of this.
  */

 int
 pathcmp(const char *a, const char *b)
 {
 	/* Skip leading './' */
 	if (a[0] == '.' && a[1] == '/' && a[2] != '\0')
 		a += 2;
 	if (b[0] == '.' && b[1] == '/' && b[2] != '\0')
 		b += 2;
 	/* Find the first difference, or return (0) if none. */
 	while (*a == *b) {
 		if (*a == '\0')
 			return (0);
 		a++;
 		b++;
 	}
 	/*
 	 * If one ends in '/' and the other one doesn't,
 	 * they're the same.
 	 */
 	if (a[0] == '/' && a[1] == '\0' && b[0] == '\0')
 		return (0);
 	if (a[0] == '\0' && b[0] == '/' && b[1] == '\0')
 		return (0);
 	/* They're really different, return the correct sign. */
 	return (*(const unsigned char *)a - *(const unsigned char *)b);
 }
	/*-
	* Copyright (c) 2003-2007 Tim Kientzle
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "bsdtar_platform.h"
	__FBSDID("$FreeBSD: src/usr.bin/tar/util.c,v 1.23 2008/12/15 06:00:25 kientzle Exp $");

	#ifdef HAVE_SYS_STAT_H
	#include <sys/stat.h>
	#endif
	#ifdef HAVE_SYS_TYPES_H
	#include <sys/types.h> /* Linux doesn't define mode_t, etc. in sys/stat.h. */
	#endif
	#include <ctype.h>
	#ifdef HAVE_ERRNO_H
	#include <errno.h>
	#endif
	#ifdef HAVE_STDARG_H
	#include <stdarg.h>
	#endif
	#include <stdio.h>
	#ifdef HAVE_STDLIB_H
	#include <stdlib.h>
	#endif
	#ifdef HAVE_STRING_H
	#include <string.h>
	#endif
	#ifdef HAVE_WCTYPE_H
	#include <wctype.h>
	#else
	/* If we don't have wctype, we need to hack up some version of iswprint(). */
	#define iswprint isprint
	#endif

	#include "bsdtar.h"

	static void bsdtar_vwarnc(struct bsdtar *, int code,
	const char *fmt, va_list ap);
	static size_t bsdtar_expand_char(char *, size_t, char);
	static const char strip_components(const char path, int elements);

	/* TODO: Hack up a version of mbtowc for platforms with no wide
	* character support at all. I think the following might suffice,
	* but it needs careful testing.
	* #if !HAVE_MBTOWC
	* #define mbtowc(wcp, p, n) ((wcp = p), 1)
	* #endif
	*/

	/*
	* Print a string, taking care with any non-printable characters.
	*
	* Note that we use a stack-allocated buffer to receive the formatted
	* string if we can. This is partly performance (avoiding a call to
	* malloc()), partly out of expedience (we have to call vsnprintf()
	* before malloc() anyway to find out how big a buffer we need; we may
	* as well point that first call at a small local buffer in case it
	* works), but mostly for safety (so we can use this to print messages
	* about out-of-memory conditions).
	*/

	void
	safe_fprintf(FILE f, const char fmt, ...)
	{
	char fmtbuff_stack[256]; /* Place to format the printf() string. */
	char outbuff[256]; /* Buffer for outgoing characters. */
	char fmtbuff_heap; / If fmtbuff_stack is too small, we use malloc */
	char fmtbuff; / Pointer to fmtbuff_stack or fmtbuff_heap. */
	int fmtbuff_length;
	int length;
	va_list ap;
	const char *p;
	unsigned i;
	wchar_t wc;
	char try_wc;

	/* Use a stack-allocated buffer if we can, for speed and safety. */
	fmtbuff_heap = NULL;
	fmtbuff_length = sizeof(fmtbuff_stack);
	fmtbuff = fmtbuff_stack;

	/* Try formatting into the stack buffer. */
	va_start(ap, fmt);
	length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);
	va_end(ap);

	/* If the result was too large, allocate a buffer on the heap. */
	if (length >= fmtbuff_length) {
	fmtbuff_length = length+1;
	fmtbuff_heap = malloc(fmtbuff_length);

	/* Reformat the result into the heap buffer if we can. */
	if (fmtbuff_heap != NULL) {
	fmtbuff = fmtbuff_heap;
	va_start(ap, fmt);
	length = vsnprintf(fmtbuff, fmtbuff_length, fmt, ap);
	va_end(ap);
	} else {
	/* Leave fmtbuff pointing to the truncated
	* string in fmtbuff_stack. */
	length = sizeof(fmtbuff_stack) - 1;
	}
	}

	/* Note: mbrtowc() has a cleaner API, but mbtowc() seems a bit
	* more portable, so we use that here instead. */
	mbtowc(NULL, NULL, 0); /* Reset the shift state. */

	/* Write data, expanding unprintable characters. */
	p = fmtbuff;
	i = 0;
	try_wc = 1;
	while (*p != '\0') {
	int n;

	/* Convert to wide char, test if the wide
	* char is printable in the current locale. */
	if (try_wc && (n = mbtowc(&wc, p, length)) != -1) {
	length -= n;
	if (iswprint(wc) && wc != L'\\') {
	/* Printable, copy the bytes through. */
	while (n-- > 0)
	outbuff[i++] = *p++;
	} else {
	/* Not printable, format the bytes. */
	while (n-- > 0)
	i += bsdtar_expand_char(
	outbuff, i, *p++);
	}
	} else {
	/* After any conversion failure, don't bother
	* trying to convert the rest. */
	i += bsdtar_expand_char(outbuff, i, *p++);
	try_wc = 0;
	}

	/* If our output buffer is full, dump it and keep going. */
	if (i > (sizeof(outbuff) - 20)) {
	outbuff[i++] = '\0';
	fprintf(f, "%s", outbuff);
	i = 0;
	}
	}
	outbuff[i++] = '\0';
	fprintf(f, "%s", outbuff);

	/* If we allocated a heap-based formatting buffer, free it now. */
	if (fmtbuff_heap != NULL)
	free(fmtbuff_heap);
	}

	/*
	* Render an arbitrary sequence of bytes into printable ASCII characters.
	*/
	static size_t
	bsdtar_expand_char(char *buff, size_t offset, char c)
	{
	size_t i = offset;

	if (isprint(c) && c != '\\')
	buff[i++] = c;
	else {
	buff[i++] = '\\';
	switch (c) {
	case '\a': buff[i++] = 'a'; break;
	case '\b': buff[i++] = 'b'; break;
	case '\f': buff[i++] = 'f'; break;
	case '\n': buff[i++] = 'n'; break;
	#if '\r' != '\n'
	/* On some platforms, \n and \r are the same. */
	case '\r': buff[i++] = 'r'; break;
	#endif
	case '\t': buff[i++] = 't'; break;
	case '\v': buff[i++] = 'v'; break;
	case '\\': buff[i++] = '\\'; break;
	default:
	sprintf(buff + i, "%03o", 0xFF & (int)c);
	i += 3;
	}
	}

	return (i - offset);
	}

	static void
	bsdtar_vwarnc(struct bsdtar bsdtar, int code, const char fmt, va_list ap)
	{
	fprintf(stderr, "%s: ", bsdtar->progname);
	vfprintf(stderr, fmt, ap);
	if (code != 0)
	fprintf(stderr, ": %s", strerror(code));
	fprintf(stderr, "\n");
	}

	void
	bsdtar_warnc(struct bsdtar bsdtar, int code, const char fmt, ...)
	{
	va_list ap;

	va_start(ap, fmt);
	bsdtar_vwarnc(bsdtar, code, fmt, ap);
	va_end(ap);
	}

	void
	bsdtar_errc(struct bsdtar bsdtar, int eval, int code, const char fmt, ...)
	{
	va_list ap;

	va_start(ap, fmt);
	bsdtar_vwarnc(bsdtar, code, fmt, ap);
	va_end(ap);
	exit(eval);
	}

	int
	yes(const char *fmt, ...)
	{
	char buff[32];
	char *p;
	ssize_t l;

	va_list ap;
	va_start(ap, fmt);
	vfprintf(stderr, fmt, ap);
	va_end(ap);
	fprintf(stderr, " (y/N)? ");
	fflush(stderr);

	l = read(2, buff, sizeof(buff) - 1);
	if (l <= 0)
	return (0);
	buff[l] = 0;

	for (p = buff; *p != '\0'; p++) {
	if (isspace(0xff & (int)*p))
	continue;
	switch(*p) {
	case 'y': case 'Y':
	return (1);
	case 'n': case 'N':
	return (0);
	default:
	return (0);
	}
	}

	return (0);
	}

	/*
	* Read lines from file and do something with each one. If option_null
	* is set, lines are terminated with zero bytes; otherwise, they're
	* terminated with newlines.
	*
	* This uses a self-sizing buffer to handle arbitrarily-long lines.
	* If the "process" function returns non-zero for any line, this
	* function will return non-zero after attempting to process all
	* remaining lines.
	*/
	int
	process_lines(struct bsdtar bsdtar, const char pathname,
	int (process)(struct bsdtar , const char *))
	{
	FILE *f;
	char buff, buff_end, line_start, line_end, *p;
	size_t buff_length, new_buff_length, bytes_read, bytes_wanted;
	int separator;
	int ret;

	separator = bsdtar->option_null ? '\0' : '\n';
	ret = 0;

	if (strcmp(pathname, "-") == 0)
	f = stdin;
	else
	f = fopen(pathname, "r");
	if (f == NULL)
	bsdtar_errc(bsdtar, 1, errno, "Couldn't open %s", pathname);
	buff_length = 8192;
	buff = malloc(buff_length);
	if (buff == NULL)
	bsdtar_errc(bsdtar, 1, ENOMEM, "Can't read %s", pathname);
	line_start = line_end = buff_end = buff;
	for (;;) {
	/* Get some more data into the buffer. */
	bytes_wanted = buff + buff_length - buff_end;
	bytes_read = fread(buff_end, 1, bytes_wanted, f);
	buff_end += bytes_read;
	/* Process all complete lines in the buffer. */
	while (line_end < buff_end) {
	if (*line_end == separator) {
	*line_end = '\0';
	if ((*process)(bsdtar, line_start) != 0)
	ret = -1;
	line_start = line_end + 1;
	line_end = line_start;
	} else
	line_end++;
	}
	if (feof(f))
	break;
	if (ferror(f))
	bsdtar_errc(bsdtar, 1, errno,
	"Can't read %s", pathname);
	if (line_start > buff) {
	/* Move a leftover fractional line to the beginning. */
	memmove(buff, line_start, buff_end - line_start);
	buff_end -= line_start - buff;
	line_end -= line_start - buff;
	line_start = buff;
	} else {
	/* Line is too big; enlarge the buffer. */
	new_buff_length = buff_length * 2;
	if (new_buff_length <= buff_length)
	bsdtar_errc(bsdtar, 1, ENOMEM,
	"Line too long in %s", pathname);
	buff_length = new_buff_length;
	p = realloc(buff, buff_length);
	if (p == NULL)
	bsdtar_errc(bsdtar, 1, ENOMEM,
	"Line too long in %s", pathname);
	buff_end = p + (buff_end - buff);
	line_end = p + (line_end - buff);
	line_start = buff = p;
	}
	}
	/* At end-of-file, handle the final line. */
	if (line_end > line_start) {
	*line_end = '\0';
	if ((*process)(bsdtar, line_start) != 0)
	ret = -1;
	}
	free(buff);
	if (f != stdin)
	fclose(f);
	return (ret);
	}

	/*-
	* The logic here for -C <dir> attempts to avoid
	* chdir() as long as possible. For example:
	* "-C /foo -C /bar file" needs chdir("/bar") but not chdir("/foo")
	* "-C /foo -C bar file" needs chdir("/foo/bar")
	* "-C /foo -C bar /file1" does not need chdir()
	* "-C /foo -C bar /file1 file2" needs chdir("/foo/bar") before file2
	*
	* The only correct way to handle this is to record a "pending" chdir
	* request and combine multiple requests intelligently until we
	* need to process a non-absolute file. set_chdir() adds the new dir
	* to the pending list; do_chdir() actually executes any pending chdir.
	*
	* This way, programs that build tar command lines don't have to worry
	* about -C with non-existent directories; such requests will only
	* fail if the directory must be accessed.
	*/
	void
	set_chdir(struct bsdtar bsdtar, const char newdir)
	{
	if (newdir[0] == '/') {
	/* The -C /foo -C /bar case; dump first one. */
	free(bsdtar->pending_chdir);
	bsdtar->pending_chdir = NULL;
	}
	if (bsdtar->pending_chdir == NULL)
	/* Easy case: no previously-saved dir. */
	bsdtar->pending_chdir = strdup(newdir);
	else {
	/* The -C /foo -C bar case; concatenate */
	char *old_pending = bsdtar->pending_chdir;
	size_t old_len = strlen(old_pending);
	bsdtar->pending_chdir = malloc(old_len + strlen(newdir) + 2);
	if (old_pending[old_len - 1] == '/')
	old_pending[old_len - 1] = '\0';
	if (bsdtar->pending_chdir != NULL)
	sprintf(bsdtar->pending_chdir, "%s/%s",
	old_pending, newdir);
	free(old_pending);
	}
	if (bsdtar->pending_chdir == NULL)
	bsdtar_errc(bsdtar, 1, errno, "No memory");
	}

	void
	do_chdir(struct bsdtar *bsdtar)
	{
	if (bsdtar->pending_chdir == NULL)
	return;

	if (chdir(bsdtar->pending_chdir) != 0) {
	bsdtar_errc(bsdtar, 1, 0, "could not chdir to '%s'\n",
	bsdtar->pending_chdir);
	}
	free(bsdtar->pending_chdir);
	bsdtar->pending_chdir = NULL;
	}

	const char *
	strip_components(const char *path, int elements)
	{
	const char *p = path;

	while (elements > 0) {
	switch (*p++) {
	case '/':
	elements--;
	path = p;
	break;
	case '\0':
	/* Path is too short, skip it. */
	return (NULL);
	}
	}

	while (*path == '/')
	++path;
	if (*path == '\0')
	return (NULL);

	return (path);
	}

	/*
	* Handle --strip-components and any future path-rewriting options.
	* Returns non-zero if the pathname should not be extracted.
	*
	* TODO: Support pax-style regex path rewrites.
	*/
	int
	edit_pathname(struct bsdtar bsdtar, struct archive_entry entry)
	{
	const char *name = archive_entry_pathname(entry);
	#if HAVE_REGEX_H
	char *subst_name;
	#endif
	int r;

	#if HAVE_REGEX_H
	r = apply_substitution(bsdtar, name, &subst_name, 0);
	if (r == -1) {
	bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
	return 1;
	}
	if (r == 1) {
	archive_entry_copy_pathname(entry, subst_name);
	if (*subst_name == '\0') {
	free(subst_name);
	return -1;
	} else
	free(subst_name);
	name = archive_entry_pathname(entry);
	}

	if (archive_entry_hardlink(entry)) {
	r = apply_substitution(bsdtar, archive_entry_hardlink(entry), &subst_name, 1);
	if (r == -1) {
	bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
	return 1;
	}
	if (r == 1) {
	archive_entry_copy_hardlink(entry, subst_name);
	free(subst_name);
	}
	}
	if (archive_entry_symlink(entry) != NULL) {
	r = apply_substitution(bsdtar, archive_entry_symlink(entry), &subst_name, 1);
	if (r == -1) {
	bsdtar_warnc(bsdtar, 0, "Invalid substitution, skipping entry");
	return 1;
	}
	if (r == 1) {
	archive_entry_copy_symlink(entry, subst_name);
	free(subst_name);
	}
	}
	#endif

	/* Strip leading dir names as per --strip-components option. */
	if (bsdtar->strip_components > 0) {
	const char *linkname = archive_entry_hardlink(entry);

	name = strip_components(name, bsdtar->strip_components);
	if (name == NULL)
	return (1);

	if (linkname != NULL) {
	linkname = strip_components(linkname,
	bsdtar->strip_components);
	if (linkname == NULL)
	return (1);
	archive_entry_copy_hardlink(entry, linkname);
	}
	}

	/* Strip redundant leading '/' characters. */
	while (name[0] == '/' && name[1] == '/')
	name++;

	/* Strip leading '/' unless user has asked us not to. */
	if (name[0] == '/' && !bsdtar->option_absolute_paths) {
	/* Generate a warning the first time this happens. */
	if (!bsdtar->warned_lead_slash) {
	bsdtar_warnc(bsdtar, 0,
	"Removing leading '/' from member names");
	bsdtar->warned_lead_slash = 1;
	}
	name++;
	/* Special case: Stripping leading '/' from "/" yields ".". */
	if (*name == '\0')
	name = ".";
	}

	/* Safely replace name in archive_entry. */
	if (name != archive_entry_pathname(entry)) {
	char *q = strdup(name);
	archive_entry_copy_pathname(entry, q);
	free(q);
	}
	return (0);
	}

	/*
	* Like strcmp(), but try to be a little more aware of the fact that
	* we're comparing two paths. Right now, it just handles leading
	* "./" and trailing '/' specially, so that "a/b/" == "./a/b"
	*
	* TODO: Make this better, so that "./a//b/./c/" == "a/b/c"
	* TODO: After this works, push it down into libarchive.
	* TODO: Publish the path normalization routines in libarchive so
	* that bsdtar can normalize paths and use fast strcmp() instead
	* of this.
	*/

	int
	pathcmp(const char a, const char b)
	{
	/* Skip leading './' */
	if (a[0] == '.' && a[1] == '/' && a[2] != '\0')
	a += 2;
	if (b[0] == '.' && b[1] == '/' && b[2] != '\0')
	b += 2;
	/* Find the first difference, or return (0) if none. */
	while (a == b) {
	if (*a == '\0')
	return (0);
	a++;
	b++;
	}
	/*
	* If one ends in '/' and the other one doesn't,
	* they're the same.
	*/
	if (a[0] == '/' && a[1] == '\0' && b[0] == '\0')
	return (0);
	if (a[0] == '\0' && b[0] == '/' && b[1] == '\0')
	return (0);
	/* They're really different, return the correct sign. */
	return ((const unsigned char )a - (const unsigned char )b);
	}