move several applets to more correct ex-project. No code changes.

1 files changed, 1282 insertions, 0 deletions

diff --git a/editors/diff.c b/editors/diff.c
new file mode 100644
index 0000000..830c15e
--- /dev/null
+++ b/editors/diff.c
@@ -0,0 +1,1282 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Mini diff implementation for busybox, adapted from OpenBSD diff.
+ *
+ * Copyright (C) 2006 by Robert Sullivan <cogito.ergo.cogito@hotmail.com>
+ * Copyright (c) 2003 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Sponsored in part by the Defense Advanced Research Projects
+ * Agency (DARPA) and Air Force Research Laboratory, Air Force
+ * Materiel Command, USAF, under agreement number F39502-99-1-0512.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+
+#define FSIZE_MAX 32768
+
+/*
+ * Output flags
+ */
+#define D_HEADER        1	/* Print a header/footer between files */
+#define D_EMPTY1        2	/* Treat first file as empty (/dev/null) */
+#define D_EMPTY2        4	/* Treat second file as empty (/dev/null) */
+
+/*
+ * Status values for print_status() and diffreg() return values
+ * Guide:
+ * D_SAME - files are the same
+ * D_DIFFER - files differ
+ * D_BINARY - binary files differ
+ * D_COMMON - subdirectory common to both dirs
+ * D_ONLY - file only exists in one dir
+ * D_MISMATCH1 - path1 a dir, path2 a file
+ * D_MISMATCH2 - path1 a file, path2 a dir
+ * D_ERROR - error occurred
+ * D_SKIPPED1 - skipped path1 as it is a special file
+ * D_SKIPPED2 - skipped path2 as it is a special file
+ */
+
+#define D_SAME		0
+#define D_DIFFER	(1<<0)
+#define D_BINARY	(1<<1)
+#define D_COMMON	(1<<2)
+#define D_ONLY		(1<<3)
+#define D_MISMATCH1	(1<<4)
+#define D_MISMATCH2	(1<<5)
+#define D_ERROR		(1<<6)
+#define D_SKIPPED1	(1<<7)
+#define D_SKIPPED2	(1<<8)
+
+/* Command line options */
+#define FLAG_a	(1<<0)
+#define FLAG_b	(1<<1)
+#define FLAG_d  (1<<2)
+#define FLAG_i	(1<<3)
+#define FLAG_L	(1<<4)
+#define FLAG_N	(1<<5)
+#define FLAG_q	(1<<6)
+#define FLAG_r	(1<<7)
+#define FLAG_s	(1<<8)
+#define FLAG_S	(1<<9)
+#define FLAG_t	(1<<10)
+#define FLAG_T	(1<<11)
+#define FLAG_U	(1<<12)
+#define	FLAG_w	(1<<13)
+
+struct cand {
+	int x;
+	int y;
+	int pred;
+};
+
+struct line {
+	int serial;
+	int value;
+};
+
+/*
+ * The following struct is used to record change information
+ * doing a "context" or "unified" diff.  (see routine "change" to
+ * understand the highly mnemonic field names)
+ */
+struct context_vec {
+	int a;          /* start line in old file */
+	int b;          /* end line in old file */
+	int c;          /* start line in new file */
+	int d;          /* end line in new file */
+};
+
+struct globals {
+	USE_FEATURE_DIFF_DIR(char **dl;)
+	USE_FEATURE_DIFF_DIR(int dl_count;)
+	/* This is the default number of lines of context. */
+	int context;
+	size_t max_context;
+	int status;
+	char *start;
+	const char *label1;
+	const char *label2;
+	struct line *file[2];
+	int *J;          /* will be overlaid on class */
+	int *class;      /* will be overlaid on file[0] */
+	int *klist;      /* will be overlaid on file[0] after class */
+	int *member;     /* will be overlaid on file[1] */
+	int clen;
+	int len[2];
+	int pref, suff;  /* length of prefix and suffix */
+	int slen[2];
+	bool anychange;
+	long *ixnew;     /* will be overlaid on file[1] */
+	long *ixold;     /* will be overlaid on klist */
+	struct cand *clist;  /* merely a free storage pot for candidates */
+	int clistlen;    /* the length of clist */
+	struct line *sfile[2];   /* shortened by pruning common prefix/suffix */
+	struct context_vec *context_vec_start;
+	struct context_vec *context_vec_end;
+	struct context_vec *context_vec_ptr;
+	struct stat stb1, stb2;
+};
+#define G (*ptr_to_globals)
+#define dl                 (G.dl                )
+#define dl_count           (G.dl_count          )
+#define context            (G.context           )
+#define max_context        (G.max_context       )
+#define status             (G.status            )
+#define start              (G.start             )
+#define label1             (G.label1            )
+#define label2             (G.label2            )
+#define file               (G.file              )
+#define J                  (G.J                 )
+#define class              (G.class             )
+#define klist              (G.klist             )
+#define member             (G.member            )
+#define clen               (G.clen              )
+#define len                (G.len               )
+#define pref               (G.pref              )
+#define suff               (G.suff              )
+#define slen               (G.slen              )
+#define anychange          (G.anychange         )
+#define ixnew              (G.ixnew             )
+#define ixold              (G.ixold             )
+#define clist              (G.clist             )
+#define clistlen           (G.clistlen          )
+#define sfile              (G.sfile             )
+#define context_vec_start  (G.context_vec_start )
+#define context_vec_end    (G.context_vec_end   )
+#define context_vec_ptr    (G.context_vec_ptr   )
+#define stb1               (G.stb1              )
+#define stb2               (G.stb2              )
+#define INIT_G() do { \
+	PTR_TO_GLOBALS = xzalloc(sizeof(G)); \
+	context = 3; \
+	max_context = 64; \
+} while (0)
+
+
+static void print_only(const char *path, size_t dirlen, const char *entry)
+{
+	if (dirlen > 1)
+		dirlen--;
+	printf("Only in %.*s: %s\n", (int) dirlen, path, entry);
+}
+
+static void print_status(int val, char *path1, char *path2, char *entry)
+{
+	const char * const _entry = entry ? entry : "";
+	char * const _path1 = entry ? concat_path_file(path1, _entry) : path1;
+	char * const _path2 = entry ? concat_path_file(path2, _entry) : path2;
+
+	switch (val) {
+	case D_ONLY:
+		print_only(path1, strlen(path1), entry);
+		break;
+	case D_COMMON:
+		printf("Common subdirectories: %s and %s\n", _path1, _path2);
+		break;
+	case D_BINARY:
+		printf("Binary files %s and %s differ\n", _path1, _path2);
+		break;
+	case D_DIFFER:
+		if (option_mask32 & FLAG_q)
+			printf("Files %s and %s differ\n", _path1, _path2);
+		break;
+	case D_SAME:
+		if (option_mask32 & FLAG_s)
+			printf("Files %s and %s are identical\n", _path1, _path2);
+		break;
+	case D_MISMATCH1:
+		printf("File %s is a %s while file %s is a %s\n",
+			   _path1, "directory", _path2, "regular file");
+		break;
+	case D_MISMATCH2:
+		printf("File %s is a %s while file %s is a %s\n",
+			   _path1, "regular file", _path2, "directory");
+		break;
+	case D_SKIPPED1:
+		printf("File %s is not a regular file or directory and was skipped\n",
+			   _path1);
+		break;
+	case D_SKIPPED2:
+		printf("File %s is not a regular file or directory and was skipped\n",
+			   _path2);
+		break;
+	}
+	if (entry) {
+		free(_path1);
+		free(_path2);
+	}
+}
+static void fiddle_sum(int *sum, int t)
+{
+	*sum = (int)(*sum * 127 + t);
+}
+/*
+ * Hash function taken from Robert Sedgewick, Algorithms in C, 3d ed., p 578.
+ */
+static int readhash(FILE * f)
+{
+	int i, t, space;
+	int sum;
+
+	sum = 1;
+	space = 0;
+	if (!(option_mask32 & (FLAG_b | FLAG_w))) {
+		for (i = 0; (t = getc(f)) != '\n'; i++) {
+			if (t == EOF) {
+				if (i == 0)
+					return 0;
+				break;
+			}
+			fiddle_sum(&sum, t);
+		}
+	} else {
+		for (i = 0;;) {
+			switch (t = getc(f)) {
+			case '\t':
+			case '\r':
+			case '\v':
+			case '\f':
+			case ' ':
+				space++;
+				continue;
+			default:
+				if (space && !(option_mask32 & FLAG_w)) {
+					i++;
+					space = 0;
+				}
+				fiddle_sum(&sum, t);
+				i++;
+				continue;
+			case EOF:
+				if (i == 0)
+					return 0;
+				/* FALLTHROUGH */
+			case '\n':
+				break;
+			}
+			break;
+		}
+	}
+	/*
+	 * There is a remote possibility that we end up with a zero sum.
+	 * Zero is used as an EOF marker, so return 1 instead.
+	 */
+	return (sum == 0 ? 1 : sum);
+}
+
+
+/*
+ * Check to see if the given files differ.
+ * Returns 0 if they are the same, 1 if different, and -1 on error.
+ */
+static int files_differ(FILE * f1, FILE * f2, int flags)
+{
+	size_t i, j;
+
+	if ((flags & (D_EMPTY1 | D_EMPTY2)) || stb1.st_size != stb2.st_size
+	 || (stb1.st_mode & S_IFMT) != (stb2.st_mode & S_IFMT)
+	) {
+		return 1;
+	}
+	while (1) {
+		i = fread(bb_common_bufsiz1,            1, BUFSIZ/2, f1);
+		j = fread(bb_common_bufsiz1 + BUFSIZ/2, 1, BUFSIZ/2, f2);
+		if (i != j)
+			return 1;
+		if (i == 0)
+			return (ferror(f1) || ferror(f2));
+		if (memcmp(bb_common_bufsiz1,
+		           bb_common_bufsiz1 + BUFSIZ/2, i) != 0)
+			return 1;
+	}
+}
+
+
+static void prepare(int i, FILE * fd, off_t filesize)
+{
+	struct line *p;
+	int h;
+	size_t j, sz;
+
+	rewind(fd);
+
+	sz = (filesize <= FSIZE_MAX ? filesize : FSIZE_MAX) / 25;
+	if (sz < 100)
+		sz = 100;
+
+	p = xmalloc((sz + 3) * sizeof(struct line));
+	j = 0;
+	while ((h = readhash(fd))) {
+		if (j == sz) {
+			sz = sz * 3 / 2;
+			p = xrealloc(p, (sz + 3) * sizeof(struct line));
+		}
+		p[++j].value = h;
+	}
+	len[i] = j;
+	file[i] = p;
+}
+
+
+static void prune(void)
+{
+	int i, j;
+
+	for (pref = 0; pref < len[0] && pref < len[1] &&
+		 file[0][pref + 1].value == file[1][pref + 1].value; pref++)
+		 ;
+	for (suff = 0; suff < len[0] - pref && suff < len[1] - pref &&
+		 file[0][len[0] - suff].value == file[1][len[1] - suff].value;
+		 suff++)
+		 ;
+	for (j = 0; j < 2; j++) {
+		sfile[j] = file[j] + pref;
+		slen[j] = len[j] - pref - suff;
+		for (i = 0; i <= slen[j]; i++)
+			sfile[j][i].serial = i;
+	}
+}
+
+
+static void equiv(struct line *a, int n, struct line *b, int m, int *c)
+{
+	int i, j;
+
+	i = j = 1;
+	while (i <= n && j <= m) {
+		if (a[i].value < b[j].value)
+			a[i++].value = 0;
+		else if (a[i].value == b[j].value)
+			a[i++].value = j;
+		else
+			j++;
+	}
+	while (i <= n)
+		a[i++].value = 0;
+	b[m + 1].value = 0;
+	j = 0;
+	while (++j <= m) {
+		c[j] = -b[j].serial;
+		while (b[j + 1].value == b[j].value) {
+			j++;
+			c[j] = b[j].serial;
+		}
+	}
+	c[j] = -1;
+}
+
+
+static int isqrt(int n)
+{
+	int y, x;
+
+	if (n == 0)
+		return 0;
+	x = 1;
+	do {
+		y = x;
+		x = n / x;
+		x += y;
+		x /= 2;
+	} while ((x - y) > 1 || (x - y) < -1);
+
+	return x;
+}
+
+
+static int newcand(int x, int y, int pred)
+{
+	struct cand *q;
+
+	if (clen == clistlen) {
+		clistlen = clistlen * 11 / 10;
+		clist = xrealloc(clist, clistlen * sizeof(struct cand));
+	}
+	q = clist + clen;
+	q->x = x;
+	q->y = y;
+	q->pred = pred;
+	return clen++;
+}
+
+
+static int search(int *c, int k, int y)
+{
+	int i, j, l, t;
+
+	if (clist[c[k]].y < y)	/* quick look for typical case */
+		return k + 1;
+	i = 0;
+	j = k + 1;
+	while (1) {
+		l = i + j;
+		if ((l >>= 1) <= i)
+			break;
+		t = clist[c[l]].y;
+		if (t > y)
+			j = l;
+		else if (t < y)
+			i = l;
+		else
+			return l;
+	}
+	return l + 1;
+}
+
+
+static int stone(int *a, int n, int *b, int *c)
+{
+	int i, k, y, j, l;
+	int oldc, tc, oldl;
+	unsigned int numtries;
+
+#if ENABLE_FEATURE_DIFF_MINIMAL
+	const unsigned int bound =
+		(option_mask32 & FLAG_d) ? UINT_MAX : MAX(256, isqrt(n));
+#else
+	const unsigned int bound = MAX(256, isqrt(n));
+#endif
+	k = 0;
+	c[0] = newcand(0, 0, 0);
+	for (i = 1; i <= n; i++) {
+		j = a[i];
+		if (j == 0)
+			continue;
+		y = -b[j];
+		oldl = 0;
+		oldc = c[0];
+		numtries = 0;
+		do {
+			if (y <= clist[oldc].y)
+				continue;
+			l = search(c, k, y);
+			if (l != oldl + 1)
+				oldc = c[l - 1];
+			if (l <= k) {
+				if (clist[c[l]].y <= y)
+					continue;
+				tc = c[l];
+				c[l] = newcand(i, y, oldc);
+				oldc = tc;
+				oldl = l;
+				numtries++;
+			} else {
+				c[l] = newcand(i, y, oldc);
+				k++;
+				break;
+			}
+		} while ((y = b[++j]) > 0 && numtries < bound);
+	}
+	return k;
+}
+
+
+static void unravel(int p)
+{
+	struct cand *q;
+	int i;
+
+	for (i = 0; i <= len[0]; i++)
+		J[i] = i <= pref ? i : i > len[0] - suff ? i + len[1] - len[0] : 0;
+	for (q = clist + p; q->y != 0; q = clist + q->pred)
+		J[q->x + pref] = q->y + pref;
+}
+
+
+static void unsort(struct line *f, int l, int *b)
+{
+	int *a, i;
+
+	a = xmalloc((l + 1) * sizeof(int));
+	for (i = 1; i <= l; i++)
+		a[f[i].serial] = f[i].value;
+	for (i = 1; i <= l; i++)
+		b[i] = a[i];
+	free(a);
+}
+
+
+static int skipline(FILE * f)
+{
+	int i, c;
+
+	for (i = 1; (c = getc(f)) != '\n' && c != EOF; i++)
+		continue;
+	return i;
+}
+
+
+/*
+ * Check does double duty:
+ *  1.  ferret out any fortuitous correspondences due
+ *      to confounding by hashing (which result in "jackpot")
+ *  2.  collect random access indexes to the two files
+ */
+static void check(FILE * f1, FILE * f2)
+{
+	int i, j, jackpot, c, d;
+	long ctold, ctnew;
+
+	rewind(f1);
+	rewind(f2);
+	j = 1;
+	ixold[0] = ixnew[0] = 0;
+	jackpot = 0;
+	ctold = ctnew = 0;
+	for (i = 1; i <= len[0]; i++) {
+		if (J[i] == 0) {
+			ixold[i] = ctold += skipline(f1);
+			continue;
+		}
+		while (j < J[i]) {
+			ixnew[j] = ctnew += skipline(f2);
+			j++;
+		}
+		if ((option_mask32 & FLAG_b) || (option_mask32 & FLAG_w)
+			|| (option_mask32 & FLAG_i)) {
+			while (1) {
+				c = getc(f1);
+				d = getc(f2);
+				/*
+				 * GNU diff ignores a missing newline
+				 * in one file if bflag || wflag.
+				 */
+				if (((option_mask32 & FLAG_b) || (option_mask32 & FLAG_w)) &&
+					((c == EOF && d == '\n') || (c == '\n' && d == EOF))) {
+					break;
+				}
+				ctold++;
+				ctnew++;
+				if ((option_mask32 & FLAG_b) && isspace(c) && isspace(d)) {
+					do {
+						if (c == '\n')
+							break;
+						ctold++;
+					} while (isspace(c = getc(f1)));
+					do {
+						if (d == '\n')
+							break;
+						ctnew++;
+					} while (isspace(d = getc(f2)));
+				} else if (option_mask32 & FLAG_w) {
+					while (isspace(c) && c != '\n') {
+						c = getc(f1);
+						ctold++;
+					}
+					while (isspace(d) && d != '\n') {
+						d = getc(f2);
+						ctnew++;
+					}
+				}
+				if (c != d) {
+					jackpot++;
+					J[i] = 0;
+					if (c != '\n' && c != EOF)
+						ctold += skipline(f1);
+					if (d != '\n' && c != EOF)
+						ctnew += skipline(f2);
+					break;
+				}
+				if (c == '\n' || c == EOF)
+					break;
+			}
+		} else {
+			while (1) {
+				ctold++;
+				ctnew++;
+				if ((c = getc(f1)) != (d = getc(f2))) {
+					J[i] = 0;
+					if (c != '\n' && c != EOF)
+						ctold += skipline(f1);
+					if (d != '\n' && c != EOF)
+						ctnew += skipline(f2);
+					break;
+				}
+				if (c == '\n' || c == EOF)
+					break;
+			}
+		}
+		ixold[i] = ctold;
+		ixnew[j] = ctnew;
+		j++;
+	}
+	for (; j <= len[1]; j++)
+		ixnew[j] = ctnew += skipline(f2);
+}
+
+
+/* shellsort CACM #201 */
+static void sort(struct line *a, int n)
+{
+	struct line *ai, *aim, w;
+	int j, m = 0, k;
+
+	if (n == 0)
+		return;
+	for (j = 1; j <= n; j *= 2)
+		m = 2 * j - 1;
+	for (m /= 2; m != 0; m /= 2) {
+		k = n - m;
+		for (j = 1; j <= k; j++) {
+			for (ai = &a[j]; ai > a; ai -= m) {
+				aim = &ai[m];
+				if (aim < ai)
+					break;	/* wraparound */
+				if (aim->value > ai[0].value ||
+					(aim->value == ai[0].value && aim->serial > ai[0].serial))
+					break;
+				w.value = ai[0].value;
+				ai[0].value = aim->value;
+				aim->value = w.value;
+				w.serial = ai[0].serial;
+				ai[0].serial = aim->serial;
+				aim->serial = w.serial;
+			}
+		}
+	}
+}
+
+
+static void uni_range(int a, int b)
+{
+	if (a < b)
+		printf("%d,%d", a, b - a + 1);
+	else if (a == b)
+		printf("%d", b);
+	else
+		printf("%d,0", b);
+}
+
+
+static void fetch(long *f, int a, int b, FILE * lb, int ch)
+{
+	int i, j, c, lastc, col, nc;
+
+	if (a > b)
+		return;
+	for (i = a; i <= b; i++) {
+		fseek(lb, f[i - 1], SEEK_SET);
+		nc = f[i] - f[i - 1];
+		if (ch != '\0') {
+			putchar(ch);
+			if (option_mask32 & FLAG_T)
+				putchar('\t');
+		}
+		col = 0;
+		for (j = 0, lastc = '\0'; j < nc; j++, lastc = c) {
+			if ((c = getc(lb)) == EOF) {
+				printf("\n\\ No newline at end of file\n");
+				return;
+			}
+			if (c == '\t' && (option_mask32 & FLAG_t)) {
+				do {
+					putchar(' ');
+				} while (++col & 7);
+			} else {
+				putchar(c);
+				col++;
+			}
+		}
+	}
+}
+
+
+static int asciifile(FILE * f)
+{
+#if ENABLE_FEATURE_DIFF_BINARY
+	int i, cnt;
+#endif
+
+	if ((option_mask32 & FLAG_a) || f == NULL)
+		return 1;
+
+#if ENABLE_FEATURE_DIFF_BINARY
+	rewind(f);
+	cnt = fread(bb_common_bufsiz1, 1, BUFSIZ, f);
+	for (i = 0; i < cnt; i++) {
+		if (!isprint(bb_common_bufsiz1[i])
+		 && !isspace(bb_common_bufsiz1[i])) {
+			return 0;
+		}
+	}
+#endif
+	return 1;
+}
+
+
+/* dump accumulated "unified" diff changes */
+static void dump_unified_vec(FILE * f1, FILE * f2)
+{
+	struct context_vec *cvp = context_vec_start;
+	int lowa, upb, lowc, upd;
+	int a, b, c, d;
+	char ch;
+
+	if (context_vec_start > context_vec_ptr)
+		return;
+
+	b = d = 0;			/* gcc */
+	lowa = MAX(1, cvp->a - context);
+	upb = MIN(len[0], context_vec_ptr->b + context);
+	lowc = MAX(1, cvp->c - context);
+	upd = MIN(len[1], context_vec_ptr->d + context);
+
+	printf("@@ -");
+	uni_range(lowa, upb);
+	printf(" +");
+	uni_range(lowc, upd);
+	printf(" @@\n");
+
+	/*
+	 * Output changes in "unified" diff format--the old and new lines
+	 * are printed together.
+	 */
+	for (; cvp <= context_vec_ptr; cvp++) {
+		a = cvp->a;
+		b = cvp->b;
+		c = cvp->c;
+		d = cvp->d;
+
+		/*
+		 * c: both new and old changes
+		 * d: only changes in the old file
+		 * a: only changes in the new file
+		 */
+		if (a <= b && c <= d)
+			ch = 'c';
+		else
+			ch = (a <= b) ? 'd' : 'a';
+#if 0
+		switch (ch) {
+		case 'c':
+			fetch(ixold, lowa, a - 1, f1, ' ');
+			fetch(ixold, a, b, f1, '-');
+			fetch(ixnew, c, d, f2, '+');
+			break;
+		case 'd':
+			fetch(ixold, lowa, a - 1, f1, ' ');
+			fetch(ixold, a, b, f1, '-');
+			break;
+		case 'a':
+			fetch(ixnew, lowc, c - 1, f2, ' ');
+			fetch(ixnew, c, d, f2, '+');
+			break;
+		}
+#else
+		if (ch == 'c' || ch == 'd') {
+			fetch(ixold, lowa, a - 1, f1, ' ');
+			fetch(ixold, a, b, f1, '-');
+		}
+		if (ch == 'a')
+			fetch(ixnew, lowc, c - 1, f2, ' ');
+		if (ch == 'c' || ch == 'a')
+			fetch(ixnew, c, d, f2, '+');
+#endif
+		lowa = b + 1;
+		lowc = d + 1;
+	}
+	fetch(ixnew, d + 1, upd, f2, ' ');
+
+	context_vec_ptr = context_vec_start - 1;
+}
+
+
+static void print_header(const char *file1, const char *file2)
+{
+	if (label1)
+		printf("--- %s\n", label1);
+	else
+		printf("--- %s\t%s", file1, ctime(&stb1.st_mtime));
+	if (label2)
+		printf("+++ %s\n", label2);
+	else
+		printf("+++ %s\t%s", file2, ctime(&stb2.st_mtime));
+}
+
+
+/*
+ * Indicate that there is a difference between lines a and b of the from file
+ * to get to lines c to d of the to file.  If a is greater than b then there
+ * are no lines in the from file involved and this means that there were
+ * lines appended (beginning at b).  If c is greater than d then there are
+ * lines missing from the to file.
+ */
+static void change(char *file1, FILE * f1, char *file2, FILE * f2, int a,
+				   int b, int c, int d)
+{
+	if ((a > b && c > d) || (option_mask32 & FLAG_q)) {
+		anychange = 1;
+		return;
+	}
+
+	/*
+	 * Allocate change records as needed.
+	 */
+	if (context_vec_ptr == context_vec_end - 1) {
+		ptrdiff_t offset = context_vec_ptr - context_vec_start;
+
+		max_context <<= 1;
+		context_vec_start = xrealloc(context_vec_start,
+				max_context * sizeof(struct context_vec));
+		context_vec_end = context_vec_start + max_context;
+		context_vec_ptr = context_vec_start + offset;
+	}
+	if (anychange == 0) {
+		/*
+		 * Print the context/unidiff header first time through.
+		 */
+		print_header(file1, file2);
+	} else if (a > context_vec_ptr->b + (2 * context) + 1 &&
+			   c > context_vec_ptr->d + (2 * context) + 1) {
+		/*
+		 * If this change is more than 'context' lines from the
+		 * previous change, dump the record and reset it.
+		 */
+		dump_unified_vec(f1, f2);
+	}
+	context_vec_ptr++;
+	context_vec_ptr->a = a;
+	context_vec_ptr->b = b;
+	context_vec_ptr->c = c;
+	context_vec_ptr->d = d;
+	anychange = 1;
+}
+
+
+static void output(char *file1, FILE * f1, char *file2, FILE * f2)
+{
+	/* Note that j0 and j1 can't be used as they are defined in math.h.
+	 * This also allows the rather amusing variable 'j00'... */
+	int m, i0, i1, j00, j01;
+
+	rewind(f1);
+	rewind(f2);
+	m = len[0];
+	J[0] = 0;
+	J[m + 1] = len[1] + 1;
+	for (i0 = 1; i0 <= m; i0 = i1 + 1) {
+		while (i0 <= m && J[i0] == J[i0 - 1] + 1)
+			i0++;
+		j00 = J[i0 - 1] + 1;
+		i1 = i0 - 1;
+		while (i1 < m && J[i1 + 1] == 0)
+			i1++;
+		j01 = J[i1 + 1] - 1;
+		J[i1] = j01;
+		change(file1, f1, file2, f2, i0, i1, j00, j01);
+	}
+	if (m == 0) {
+		change(file1, f1, file2, f2, 1, 0, 1, len[1]);
+	}
+	if (anychange != 0 && !(option_mask32 & FLAG_q)) {
+		dump_unified_vec(f1, f2);
+	}
+}
+
+/*
+ * The following code uses an algorithm due to Harold Stone,
+ * which finds a pair of longest identical subsequences in
+ * the two files.
+ *
+ * The major goal is to generate the match vector J.
+ * J[i] is the index of the line in file1 corresponding
+ * to line i file0. J[i] = 0 if there is no
+ * such line in file1.
+ *
+ * Lines are hashed so as to work in core. All potential
+ * matches are located by sorting the lines of each file
+ * on the hash (called ``value''). In particular, this
+ * collects the equivalence classes in file1 together.
+ * Subroutine equiv replaces the value of each line in
+ * file0 by the index of the first element of its
+ * matching equivalence in (the reordered) file1.
+ * To save space equiv squeezes file1 into a single
+ * array member in which the equivalence classes
+ * are simply concatenated, except that their first
+ * members are flagged by changing sign.
+ *
+ * Next the indices that point into member are unsorted into
+ * array class according to the original order of file0.
+ *
+ * The cleverness lies in routine stone. This marches
+ * through the lines of file0, developing a vector klist
+ * of "k-candidates". At step i a k-candidate is a matched
+ * pair of lines x,y (x in file0 y in file1) such that
+ * there is a common subsequence of length k
+ * between the first i lines of file0 and the first y
+ * lines of file1, but there is no such subsequence for
+ * any smaller y. x is the earliest possible mate to y
+ * that occurs in such a subsequence.
+ *
+ * Whenever any of the members of the equivalence class of
+ * lines in file1 matable to a line in file0 has serial number
+ * less than the y of some k-candidate, that k-candidate
+ * with the smallest such y is replaced. The new
+ * k-candidate is chained (via pred) to the current
+ * k-1 candidate so that the actual subsequence can
+ * be recovered. When a member has serial number greater
+ * that the y of all k-candidates, the klist is extended.
+ * At the end, the longest subsequence is pulled out
+ * and placed in the array J by unravel
+ *
+ * With J in hand, the matches there recorded are
+ * checked against reality to assure that no spurious
+ * matches have crept in due to hashing. If they have,
+ * they are broken, and "jackpot" is recorded--a harmless
+ * matter except that a true match for a spuriously
+ * mated line may now be unnecessarily reported as a change.
+ *
+ * Much of the complexity of the program comes simply
+ * from trying to minimize core utilization and
+ * maximize the range of doable problems by dynamically
+ * allocating what is needed and reusing what is not.
+ * The core requirements for problems larger than somewhat
+ * are (in words) 2*length(file0) + length(file1) +
+ * 3*(number of k-candidates installed),  typically about
+ * 6n words for files of length n.
+ */
+static unsigned diffreg(char * ofile1, char * ofile2, int flags)
+{
+	char *file1 = ofile1;
+	char *file2 = ofile2;
+	FILE *f1 = stdin, *f2 = stdin;
+	unsigned rval;
+	int i;
+
+	anychange = 0;
+	context_vec_ptr = context_vec_start - 1;
+
+	if (S_ISDIR(stb1.st_mode) != S_ISDIR(stb2.st_mode))
+		return (S_ISDIR(stb1.st_mode) ? D_MISMATCH1 : D_MISMATCH2);
+
+	rval = D_SAME;
+
+	if (LONE_DASH(file1) && LONE_DASH(file2))
+		goto closem;
+
+	if (flags & D_EMPTY1)
+		f1 = xfopen(bb_dev_null, "r");
+	else if (NOT_LONE_DASH(file1))
+		f1 = xfopen(file1, "r");
+	if (flags & D_EMPTY2)
+		f2 = xfopen(bb_dev_null, "r");
+	else if (NOT_LONE_DASH(file2))
+		f2 = xfopen(file2, "r");
+
+/* We can't diff non-seekable stream - we use rewind(), fseek().
+ * This can be fixed (volunteers?).
+ * Meanwhile we should check it here by stat'ing input fds,
+ * but I am lazy and check that in main() instead.
+ * Check in main won't catch "diffing fifos buried in subdirectories"
+ * failure scenario - not very likely in real life... */
+
+	i = files_differ(f1, f2, flags);
+	if (i == 0)
+		goto closem;
+	else if (i != 1) {	/* 1 == ok */
+		/* error */
+		status |= 2;
+		goto closem;
+	}
+
+	if (!asciifile(f1) || !asciifile(f2)) {
+		rval = D_BINARY;
+		status |= 1;
+		goto closem;
+	}
+
+	prepare(0, f1, stb1.st_size);
+	prepare(1, f2, stb2.st_size);
+	prune();
+	sort(sfile[0], slen[0]);
+	sort(sfile[1], slen[1]);
+
+	member = (int *) file[1];
+	equiv(sfile[0], slen[0], sfile[1], slen[1], member);
+	member = xrealloc(member, (slen[1] + 2) * sizeof(int));
+
+	class = (int *) file[0];
+	unsort(sfile[0], slen[0], class);
+	class = xrealloc(class, (slen[0] + 2) * sizeof(int));
+
+	klist = xmalloc((slen[0] + 2) * sizeof(int));
+	clen = 0;
+	clistlen = 100;
+	clist = xmalloc(clistlen * sizeof(struct cand));
+	i = stone(class, slen[0], member, klist);
+	free(member);
+	free(class);
+
+	J = xrealloc(J, (len[0] + 2) * sizeof(int));
+	unravel(klist[i]);
+	free(clist);
+	free(klist);
+
+	ixold = xrealloc(ixold, (len[0] + 2) * sizeof(long));
+	ixnew = xrealloc(ixnew, (len[1] + 2) * sizeof(long));
+	check(f1, f2);
+	output(file1, f1, file2, f2);
+
+ closem:
+	if (anychange) {
+		status |= 1;
+		if (rval == D_SAME)
+			rval = D_DIFFER;
+	}
+	fclose_if_not_stdin(f1);
+	fclose_if_not_stdin(f2);
+	if (file1 != ofile1)
+		free(file1);
+	if (file2 != ofile2)
+		free(file2);
+	return rval;
+}
+
+
+#if ENABLE_FEATURE_DIFF_DIR
+static void do_diff(char *dir1, char *path1, char *dir2, char *path2)
+{
+	int flags = D_HEADER;
+	int val;
+	char *fullpath1 = NULL; /* if -N */
+	char *fullpath2 = NULL;
+
+	if (path1)
+		fullpath1 = concat_path_file(dir1, path1);
+	if (path2)
+		fullpath2 = concat_path_file(dir2, path2);
+
+	if (!fullpath1 || stat(fullpath1, &stb1) != 0) {
+		flags |= D_EMPTY1;
+		memset(&stb1, 0, sizeof(stb1));
+		if (path2) {
+			free(fullpath1);
+			fullpath1 = concat_path_file(dir1, path2);
+		}
+	}
+	if (!fullpath2 || stat(fullpath2, &stb2) != 0) {
+		flags |= D_EMPTY2;
+		memset(&stb2, 0, sizeof(stb2));
+		stb2.st_mode = stb1.st_mode;
+		if (path1) {
+			free(fullpath2);
+			fullpath2 = concat_path_file(dir2, path1);
+		}
+	}
+
+	if (stb1.st_mode == 0)
+		stb1.st_mode = stb2.st_mode;
+
+	if (S_ISDIR(stb1.st_mode) && S_ISDIR(stb2.st_mode)) {
+		printf("Common subdirectories: %s and %s\n", fullpath1, fullpath2);
+		goto ret;
+	}
+
+	if (!S_ISREG(stb1.st_mode) && !S_ISDIR(stb1.st_mode))
+		val = D_SKIPPED1;
+	else if (!S_ISREG(stb2.st_mode) && !S_ISDIR(stb2.st_mode))
+		val = D_SKIPPED2;
+	else
+		val = diffreg(fullpath1, fullpath2, flags);
+
+	print_status(val, fullpath1, fullpath2, NULL);
+ ret:
+	free(fullpath1);
+	free(fullpath2);
+}
+#endif
+
+
+#if ENABLE_FEATURE_DIFF_DIR
+static int dir_strcmp(const void *p1, const void *p2)
+{
+	return strcmp(*(char *const *) p1, *(char *const *) p2);
+}
+
+
+/* This function adds a filename to dl, the directory listing. */
+static int add_to_dirlist(const char *filename,
+		struct stat ATTRIBUTE_UNUSED * sb, void *userdata,
+		int depth ATTRIBUTE_UNUSED)
+{
+	/* +2: with space for eventual trailing NULL */
+	dl = xrealloc(dl, (dl_count+2) * sizeof(dl[0]));
+	dl[dl_count] = xstrdup(filename + (int)(ptrdiff_t)userdata);
+	dl_count++;
+	return TRUE;
+}
+
+
+/* This returns a sorted directory listing. */
+static char **get_dir(char *path)
+{
+	dl_count = 0;
+	dl = xzalloc(sizeof(dl[0]));
+
+	/* If -r has been set, then the recursive_action function will be
+	 * used. Unfortunately, this outputs the root directory along with
+	 * the recursed paths, so use void *userdata to specify the string
+	 * length of the root directory - '(void*)(strlen(path)+)'.
+	 * add_to_dirlist then removes root dir prefix. */
+
+	if (option_mask32 & FLAG_r) {
+		recursive_action(path, ACTION_RECURSE|ACTION_FOLLOWLINKS,
+					add_to_dirlist, NULL,
+					(void*)(strlen(path)+1), 0);
+	} else {
+		DIR *dp;
+		struct dirent *ep;
+
+		dp = warn_opendir(path);
+		while ((ep = readdir(dp))) {
+			if (!strcmp(ep->d_name, "..") || LONE_CHAR(ep->d_name, '.'))
+				continue;
+			add_to_dirlist(ep->d_name, NULL, (void*)(int)0, 0);
+		}
+		closedir(dp);
+	}
+
+	/* Sort dl alphabetically. */
+	qsort(dl, dl_count, sizeof(char *), dir_strcmp);
+
+	dl[dl_count] = NULL;
+	return dl;
+}
+
+
+static void diffdir(char *p1, char *p2)
+{
+	char **dirlist1, **dirlist2;
+	char *dp1, *dp2;
+	int pos;
+
+	/* Check for trailing slashes. */
+	dp1 = last_char_is(p1, '/');
+	if (dp1 != NULL)
+		*dp1 = '\0';
+	dp2 = last_char_is(p2, '/');
+	if (dp2 != NULL)
+		*dp2 = '\0';
+
+	/* Get directory listings for p1 and p2. */
+
+	dirlist1 = get_dir(p1);
+	dirlist2 = get_dir(p2);
+
+	/* If -S was set, find the starting point. */
+	if (start) {
+		while (*dirlist1 != NULL && strcmp(*dirlist1, start) < 0)
+			dirlist1++;
+		while (*dirlist2 != NULL && strcmp(*dirlist2, start) < 0)
+			dirlist2++;
+		if ((*dirlist1 == NULL) || (*dirlist2 == NULL))
+			bb_error_msg(bb_msg_invalid_arg, "NULL", "-S");
+	}
+
+	/* Now that both dirlist1 and dirlist2 contain sorted directory
+	 * listings, we can start to go through dirlist1. If both listings
+	 * contain the same file, then do a normal diff. Otherwise, behaviour
+	 * is determined by whether the -N flag is set. */
+	while (*dirlist1 != NULL || *dirlist2 != NULL) {
+		dp1 = *dirlist1;
+		dp2 = *dirlist2;
+		pos = dp1 == NULL ? 1 : dp2 == NULL ? -1 : strcmp(dp1, dp2);
+		if (pos == 0) {
+			do_diff(p1, dp1, p2, dp2);
+			dirlist1++;
+			dirlist2++;
+		} else if (pos < 0) {
+			if (option_mask32 & FLAG_N)
+				do_diff(p1, dp1, p2, NULL);
+			else
+				print_only(p1, strlen(p1) + 1, dp1);
+			dirlist1++;
+		} else {
+			if (option_mask32 & FLAG_N)
+				do_diff(p1, NULL, p2, dp2);
+			else
+				print_only(p2, strlen(p2) + 1, dp2);
+			dirlist2++;
+		}
+	}
+}
+#endif
+
+
+int diff_main(int argc, char **argv);
+int diff_main(int argc, char **argv)
+{
+	bool gotstdin = 0;
+	char *U_opt;
+	char *f1, *f2;
+	llist_t *L_arg = NULL;
+
+	INIT_G();
+
+	/* exactly 2 params; collect multiple -L <label> */
+	opt_complementary = "=2:L::";
+	getopt32(argc, argv, "abdiL:NqrsS:tTU:wu"
+			"p" /* ignored (for compatibility) */,
+			&L_arg, &start, &U_opt);
+	/*argc -= optind;*/
+	argv += optind;
+	while (L_arg) {
+		if (label1 && label2)
+			bb_show_usage();
+		if (!label1)
+			label1 = L_arg->data;
+		else { /* then label2 is NULL */
+			label2 = label1;
+			label1 = L_arg->data;
+		}
+		/* we leak L_arg here... */
+		L_arg = L_arg->link;
+	}
+	if (option_mask32 & FLAG_U)
+		context = xatoi_u(U_opt);
+
+	/*
+	 * Do sanity checks, fill in stb1 and stb2 and call the appropriate
+	 * driver routine.  Both drivers use the contents of stb1 and stb2.
+	 */
+
+	f1 = argv[0];
+	f2 = argv[1];
+	if (LONE_DASH(f1)) {
+		fstat(STDIN_FILENO, &stb1);
+		gotstdin = 1;
+	} else
+		xstat(f1, &stb1);
+	if (LONE_DASH(f2)) {
+		fstat(STDIN_FILENO, &stb2);
+		gotstdin = 1;
+	} else
+		xstat(f2, &stb2);
+	if (gotstdin && (S_ISDIR(stb1.st_mode) || S_ISDIR(stb2.st_mode)))
+		bb_error_msg_and_die("can't compare - to a directory");
+	if (S_ISDIR(stb1.st_mode) && S_ISDIR(stb2.st_mode)) {
+#if ENABLE_FEATURE_DIFF_DIR
+		diffdir(f1, f2);
+#else
+		bb_error_msg_and_die("directory comparison not supported");
+#endif
+	} else {
+		if (S_ISDIR(stb1.st_mode)) {
+			f1 = concat_path_file(f1, f2);
+			xstat(f1, &stb1);
+		}
+		if (S_ISDIR(stb2.st_mode)) {
+			f2 = concat_path_file(f2, f1);
+			xstat(f2, &stb2);
+		}
+/* XXX: FIXME: */
+/* We can't diff e.g. stdin supplied by a pipe - we use rewind(), fseek().
+ * This can be fixed (volunteers?) */
+		if (!S_ISREG(stb1.st_mode) || !S_ISREG(stb2.st_mode))
+			bb_error_msg_and_die("can't diff non-seekable stream");
+		print_status(diffreg(f1, f2, 0), f1, f2, NULL);
+	}
+	return status;
+}