less: total cleanup and bugfix.

Doesn't die horribly on binary files anymore.
In fact, they _100%_ work now. Control chars
are in reverse video, including DEL and that idiocy of VT-10x,
Meta-ESC [inventor of which should be prohibited from reproducing].
Regex search is fixed also. When you specify search ('/' key),
control chars turn into dots (unhighlighted),
and found occurrences highlighted instead. This is reversible.
Memory management fixed (was leaky as hell) and optimized.
Linewrapping fixed and thoroughly tested.
Max buffer size made configurable.
~ 600 bytes saved.

1 files changed, 236 insertions, 248 deletions

diff --git a/miscutils/less.c b/miscutils/less.c
index 7350067..6843ddd 100644
--- a/miscutils/less.c
+++ b/miscutils/less.c
@@ -8,30 +8,20 @@
  */
 
 /*
- *      This program needs a lot of development, so consider it in a beta stage
- *      at best.
+ * TODO:
+ * - Add more regular expression support - search modifiers, certain matches, etc.
+ * - Add more complex bracket searching - currently, nested brackets are
+ * not considered.
+ * - Add support for "F" as an input. This causes less to act in
+ * a similar way to tail -f.
+ * - Allow horizontal scrolling.
  *
- *      TODO:
- *      - Add more regular expression support - search modifiers, certain matches, etc.
- *      - Add more complex bracket searching - currently, nested brackets are
- *      not considered.
- *      - Add support for "F" as an input. This causes less to act in
- *      a similar way to tail -f.
- *      - Check for binary files, and prompt the user if a binary file
- *      is detected.
- *      - Allow horizontal scrolling. Currently, lines simply continue onto
- *      the next line, per the terminal's discretion
- *
- *      Notes:
- *      - filename is an array and not a pointer because that avoids all sorts
- *      of complications involving the fact that something that is pointed to
- *      will be changed if the pointer is changed.
- *      - the inp file pointer is used so that keyboard input works after
- *      redirected input has been read from stdin
-*/
+ * Notes:
+ * - the inp file pointer is used so that keyboard input works after
+ * redirected input has been read from stdin
+ */
 
 #include "busybox.h"
-
 #if ENABLE_FEATURE_LESS_REGEXP
 #include "xregex.h"
 #endif
@@ -70,12 +60,13 @@ static int height;
 static int width;
 static char **files;
 static char *filename;
-static char **buffer;
+static const char **buffer;
 static char **flines;
 static int current_file = 1;
 static int line_pos;
 static int num_flines;
 static int num_files = 1;
+static const char *empty_line_marker = "~";
 
 /* Command line options */
 #define FLAG_E 1
@@ -84,7 +75,6 @@ static int num_files = 1;
 #define FLAG_N (1<<3)
 #define FLAG_TILDE (1<<4)
 /* hijack command line options variable for internal state vars */
-#define LESS_STATE_PAST_EOF  (1<<5)
 #define LESS_STATE_MATCH_BACKWARDS (1<<6)
 
 #if ENABLE_FEATURE_LESS_MARKS
@@ -93,11 +83,11 @@ static int num_marks;
 #endif
 
 #if ENABLE_FEATURE_LESS_REGEXP
-static int match_found;
 static int *match_lines;
 static int match_pos;
 static int num_matches;
-static regex_t old_pattern;
+static regex_t pattern;
+static int pattern_valid;
 #endif
 
 /* Needed termios structures */
@@ -174,52 +164,57 @@ static void data_readlines(void)
 	unsigned i;
 	unsigned n = 1;
 	int w = width;
-	char *last_nl = (char*)1; /* "not NULL" */
-	char *current_line;
+	/* "remained unused space" in a line (0 if line fills entire width) */
+	int rem, last_rem = 1; /* "not 0" */
+	char *current_line, *p;
 	FILE *fp;
 
 	fp = filename ? xfopen(filename, "r") : stdin;
 	flines = NULL;
 	if (option_mask32 & FLAG_N) {
 		w -= 6;
-		if (w < 1) w = 1; /* paranoia */
 	}
 	for (i = 0; !feof(fp) && i <= MAXLINES; i++) {
 		flines = xrealloc(flines, (i+1) * sizeof(char *));
-
 		current_line = xmalloc(w);
  again:
-		current_line[0] = '\0';
-		fgets(current_line, w, fp);
+		p = current_line;
+		rem = w - 1;
+		do {
+			int c = getc(fp);
+			if (c == EOF) break;
+			if (c == '\n') break;
+			/* NUL is substituted by '\n'! */
+			if (c == '\0') c = '\n';
+			*p++ = c;
+		} while (--rem);
+		*p = '\0';
 		if (fp != stdin)
 			die_if_ferror(fp, filename);
 
-		/* Corner case: linewrap with only '\n' wrapping */
-		/* Looks ugly on screen, so we handle it specially */
-		if (!last_nl && current_line[0] == '\n') {
-			last_nl = (char*)1; /* "not NULL" */
+		/* Corner case: linewrap with only "" wrapping to next line */
+		/* Looks ugly on screen, so we do not store this empty line */
+		if (!last_rem && !current_line[0]) {
+			last_rem = 1; /* "not 0" */
 			n++;
 			goto again;
 		}
-		last_nl = last_char_is(current_line, '\n');
-		if (last_nl)
-			*last_nl = '\0';
+		last_rem = rem;
 		if (option_mask32 & FLAG_N) {
 			flines[i] = xasprintf((n <= 99999) ? "%5u %s" : "%05u %s",
 						n % 100000, current_line);
 			free(current_line);
-			if (last_nl)
+			if (rem)
 				n++;
 		} else {
 			flines[i] = xrealloc(current_line, strlen(current_line)+1);
 		}
 	}
-	num_flines = i - 2;
+	num_flines = i - 1; /* buggie: 'num_flines' must be 'max_fline' */
 
 	/* Reset variables for a new file */
 
 	line_pos = 0;
-	option_mask32 &= ~LESS_STATE_PAST_EOF;
 
 	fclose(fp);
 }
@@ -238,36 +233,28 @@ static void m_status_print(void)
 {
 	int percentage;
 
-	if (!(option_mask32 & LESS_STATE_PAST_EOF)) {
-		if (!line_pos) {
-			if (num_files > 1) {
-				printf("%s%s %s%i%s%i%s%i-%i/%i ", HIGHLIGHT,
-					filename, "(file ", current_file, " of ", num_files, ") lines ",
-					line_pos + 1, line_pos + height - 1, num_flines + 1);
-			} else {
-				printf("%s%s lines %i-%i/%i ", HIGHLIGHT,
-					filename, line_pos + 1, line_pos + height - 1,
-					num_flines + 1);
-			}
-		} else {
-			printf("%s %s lines %i-%i/%i ", HIGHLIGHT, filename,
+	if (!line_pos) {
+		if (num_files > 1) {
+			printf("%s%s %s%i%s%i%s%i-%i/%i ", HIGHLIGHT,
+				filename, "(file ", current_file, " of ", num_files, ") lines ",
 				line_pos + 1, line_pos + height - 1, num_flines + 1);
-		}
-
-		if (line_pos == num_flines - height + 2) {
-			printf("(END) %s", NORMAL);
-			if ((num_files > 1) && (current_file != num_files))
-				printf("%s- Next: %s%s", HIGHLIGHT, files[current_file], NORMAL);
 		} else {
-			percentage = calc_percent();
-			printf("%i%% %s", percentage, NORMAL);
+			printf("%s%s lines %i-%i/%i ", HIGHLIGHT,
+				filename, line_pos + 1, line_pos + height - 1,
+				num_flines + 1);
 		}
 	} else {
-		printf("%s%s lines %i-%i/%i (END) ", HIGHLIGHT, filename,
-				line_pos + 1, num_flines + 1, num_flines + 1);
+		printf("%s %s lines %i-%i/%i ", HIGHLIGHT, filename,
+			line_pos + 1, line_pos + height - 1, num_flines + 1);
+	}
+
+	if (line_pos >= num_flines - height + 2) {
+		printf("(END) %s", NORMAL);
 		if ((num_files > 1) && (current_file != num_files))
-			printf("- Next: %s", files[current_file]);
-		printf("%s", NORMAL);
+			printf("%s- Next: %s%s", HIGHLIGHT, files[current_file], NORMAL);
+	} else {
+		percentage = calc_percent();
+		printf("%i%% %s", percentage, NORMAL);
 	}
 }
 
@@ -315,22 +302,123 @@ static void status_print(void)
 #endif
 }
 
+static char controls[] =
+	/**/"\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"
+	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f"
+	"\x7f\x9b"; /* DEL and infamous Meta-ESC :( */
+static char ctrlconv[] =
+	/* Note that on input NUL is converted to '\n' ('\x0a') */
+	/* Therefore we subst '\n' with '@', not 'J' */
+	"\x40\x41\x42\x43\x44\x45\x46\x47\x48\x49\x40\x4b\x4c\x4d\x4e\x4f"
+	"\x50\x51\x52\x53\x54\x55\x56\x57\x58\x59\x5a\x5b\x5c\x5d\x5e\x5f";
+
+static void print_found(const char *line)
+{
+	int match_status;
+	int eflags;
+	char *growline;
+	regmatch_t match_structs;
+
+	char buf[width];
+	const char *str = line;
+	char *p = buf;
+	size_t n;
+
+	while (*str) {
+		n = strcspn(str, controls);
+		if (n) {
+			if (!str[n]) break;
+			memcpy(p, str, n);
+			p += n;
+			str += n;
+		}
+		n = strspn(str, controls);
+		memset(p, '.', n);
+		p += n;
+		str += n;
+		/*
+		do {
+			if (*str == '\x7f') { *p++ = '?'; str++; }
+			else if (*str == '\x9b') { *p++ = '{'; str++; }
+			else *p++ = ctrlconv[(unsigned char)*str++];
+		} while (--n);
+		*/
+	}
+	strcpy(p, str);
+
+	/* buf[] holds quarantined version of str */
+
+	/* Each part of the line that matches has the HIGHLIGHT
+	   and NORMAL escape sequences placed around it.
+	   NB: we regex against line, but insert text
+	   from quarantined copy (buf[]) */
+	str = buf;
+	growline = NULL;
+	eflags = 0;
+	goto start;
+
+	while (match_status == 0) {
+		char *new = xasprintf("%s" "%.*s" "%s" "%.*s" "%s",
+				growline ? : "",
+				match_structs.rm_so, str,
+				HIGHLIGHT,
+				match_structs.rm_eo - match_structs.rm_so,
+						str + match_structs.rm_so,
+				NORMAL);
+		free(growline); growline = new;
+		str += match_structs.rm_eo;
+		line += match_structs.rm_eo;
+		eflags = REG_NOTBOL;
+ start:
+		/* Most of the time doesn't find the regex, optimize for that */
+		match_status = regexec(&pattern, line, 1, &match_structs, eflags);
+	}
+
+	if (!growline) {
+		puts(str);
+		return;
+	}
+	printf("%s%s\n", growline, str);
+	free(growline);
+}
+
+static void print_ascii(const char *str)
+{
+	char buf[width];
+	char *p;
+	size_t n;
+
+	while (*str) {
+		n = strcspn(str, controls);
+		if (n) {
+			if (!str[n]) break;
+			printf("%.*s", n, str);
+			str += n;
+		}
+		n = strspn(str, controls);
+		p = buf;
+		do {
+			if (*str == '\x7f') { *p++ = '?'; str++; }
+			else if (*str == '\x9b') { *p++ = '{'; str++; }
+			else *p++ = ctrlconv[(unsigned char)*str++];
+		} while (--n);
+		*p = '\0';
+		printf("%s%s%s", HIGHLIGHT, buf, NORMAL);
+	}
+	puts(str);
+}
+
 /* Print the buffer */
 static void buffer_print(void)
 {
 	int i;
 
 	printf("%s", CLEAR);
-	if (num_flines >= height - 2) {
-		for (i = 0; i < height - 1; i++)
-			printf("%.*s\n", width, buffer[i]);
-	} else {
-		for (i = 1; i < (height - 1 - num_flines); i++)
-			putchar('\n');
-		for (i = 0; i < height - 1; i++)
-			printf("%.*s\n", width, buffer[i]);
-	}
-
+	for (i = 0; i < height - 1; i++)
+		if (pattern_valid)
+			print_found(buffer[i]);
+		else
+			print_ascii(buffer[i]);
 	status_print();
 }
 
@@ -339,20 +427,20 @@ static void buffer_init(void)
 {
 	int i;
 
-	if (buffer == NULL) {
+	if (!buffer) {
 		/* malloc the number of lines needed for the buffer */
 		buffer = xmalloc(height * sizeof(char *));
 	}
 
 	/* Fill the buffer until the end of the file or the
 	   end of the buffer is reached */
-	for (i = 0; (i < (height - 1)) && (i <= num_flines); i++) {
+	for (i = 0; i < height - 1 && i <= num_flines; i++) {
 		buffer[i] = flines[i];
 	}
 
 	/* If the buffer still isn't full, fill it with blank lines */
-	for (; i < (height - 1); i++) {
-		buffer[i] = "";
+	for (; i < height - 1; i++) {
+		buffer[i] = empty_line_marker;
 	}
 }
 
@@ -361,72 +449,38 @@ static void buffer_down(int nlines)
 {
 	int i;
 
-	if (!(option_mask32 & LESS_STATE_PAST_EOF)) {
-		if (line_pos + (height - 3) + nlines < num_flines) {
-			line_pos += nlines;
+	if (line_pos + (height - 3) + nlines < num_flines) {
+		line_pos += nlines;
+		for (i = 0; i < (height - 1); i++) {
+			buffer[i] = flines[line_pos + i];
+		}
+	} else {
+		/* As the number of lines requested was too large, we just move
+		to the end of the file */
+		while (line_pos + (height - 3) + 1 < num_flines) {
+			line_pos += 1;
 			for (i = 0; i < (height - 1); i++) {
 				buffer[i] = flines[line_pos + i];
 			}
-		} else {
-			/* As the number of lines requested was too large, we just move
-			to the end of the file */
-			while (line_pos + (height - 3) + 1 < num_flines) {
-				line_pos += 1;
-				for (i = 0; i < (height - 1); i++) {
-					buffer[i] = flines[line_pos + i];
-				}
-			}
 		}
-
-		/* We exit if the -E flag has been set */
-		if ((option_mask32 & FLAG_E) && (line_pos + (height - 2) == num_flines))
-			tless_exit(0);
 	}
+
+	/* We exit if the -E flag has been set */
+	if ((option_mask32 & FLAG_E) && (line_pos + (height - 2) == num_flines))
+		tless_exit(0);
 }
 
 static void buffer_up(int nlines)
 {
 	int i;
-	int tilde_line;
 
-	if (!(option_mask32 & LESS_STATE_PAST_EOF)) {
-		if (line_pos - nlines >= 0) {
-			line_pos -= nlines;
-			for (i = 0; i < (height - 1); i++) {
-				buffer[i] = flines[line_pos + i];
-			}
-		} else {
-		/* As the requested number of lines to move was too large, we
-		   move one line up at a time until we can't. */
-			while (line_pos != 0) {
-				line_pos -= 1;
-				for (i = 0; i < (height - 1); i++) {
-					buffer[i] = flines[line_pos + i];
-				}
-			}
-		}
-	}
-	else {
-		/* Work out where the tildes start */
-		tilde_line = num_flines - line_pos + 3;
-
-		line_pos -= nlines;
-		/* Going backwards nlines lines has taken us to a point where
-		   nothing is past the EOF, so we revert to normal. */
-		if (line_pos < num_flines - height + 3) {
-			option_mask32 &= ~LESS_STATE_PAST_EOF;
-			buffer_up(nlines);
+	line_pos -= nlines;
+	if (line_pos < 0) line_pos = 0;
+	for (i = 0; i < height - 1; i++) {
+		if (line_pos + i <= num_flines) {
+			buffer[i] = flines[line_pos + i];
 		} else {
-			/* We only move part of the buffer, as the rest
-			is past the EOF */
-			for (i = 0; i < (height - 1); i++) {
-				if (i < tilde_line - nlines + 1) {
-					buffer[i] = flines[line_pos + i];
-				} else {
-					if (line_pos >= num_flines - height + 2)
-						buffer[i] = "~";
-				}
-			}
+			buffer[i] = empty_line_marker;
 		}
 	}
 }
@@ -434,28 +488,19 @@ static void buffer_up(int nlines)
 static void buffer_line(int linenum)
 {
 	int i;
-	option_mask32 &= ~LESS_STATE_PAST_EOF;
 
 	if (linenum < 0 || linenum > num_flines) {
 		clear_line();
 		printf("%s%s%i%s", HIGHLIGHT, "Cannot seek to line number ", linenum + 1, NORMAL);
-	}
-	else if (linenum < (num_flines - height - 2)) {
-		for (i = 0; i < (height - 1); i++) {
-			buffer[i] = flines[linenum + i];
-		}
-		line_pos = linenum;
-		buffer_print();
 	} else {
-		for (i = 0; i < (height - 1); i++) {
-			if (linenum + i < num_flines + 2)
+		for (i = 0; i < height - 1; i++) {
+			if (linenum + i <= num_flines)
 				buffer[i] = flines[linenum + i];
-			else
-				buffer[i] = (option_mask32 & FLAG_TILDE) ? "" : "~";
+			else {
+				buffer[i] = empty_line_marker;
+			}
 		}
 		line_pos = linenum;
-		/* Set past_eof so buffer_down and buffer_up act differently */
-		option_mask32 |= LESS_STATE_PAST_EOF;
 		buffer_print();
 	}
 }
@@ -563,76 +608,37 @@ static void colon_process(void)
 	}
 }
 
-#if ENABLE_FEATURE_LESS_REGEXP
-/* The below two regular expression handler functions NEED development. */
-
-/* Get a regular expression from the user, and then go through the current
-   file line by line, running a processing regex function on each one. */
-
-static char *process_regex_on_line(char *line, regex_t *pattern, int action)
+static int normalize_match_pos(int match)
 {
-/* UNTESTED. LOOKED BUGGY AND LEAKY AS HELL. */
-/* FIXED. NEED TESTING. */
-	/* 'line' should be either returned or free()ed */
-
-	/* This function takes the regex and applies it to the line.
-	   Each part of the line that matches has the HIGHLIGHT
-	   and NORMAL escape sequences placed around it by
-	   insert_highlights if action = 1, or has the escape sequences
-	   removed if action = 0, and then the line is returned. */
-	int match_status;
-	char *line2 = line;
-	char *growline = xstrdup("");
-	char *ng;
-	regmatch_t match_structs;
-
-	match_found = 0;
-	match_status = regexec(pattern, line2, 1, &match_structs, 0);
-
-	while (match_status == 0) {
-		match_found = 1;
-		if (action) {
-			ng = xasprintf("%s%.*s%s%.*s%s", growline,
-				match_structs.rm_so, line2, HIGHLIGHT,
-				match_structs.rm_eo - match_structs.rm_so,
-				line2 + match_structs.rm_so, NORMAL);
-		} else {
-			ng = xasprintf("%s%.*s%.*s", growline,
-				match_structs.rm_so - 4, line2,
-				match_structs.rm_eo - match_structs.rm_so,
-				line2 + match_structs.rm_so);
-		}
-		free(growline); growline = ng;
-		line2 += match_structs.rm_eo;
-		match_status = regexec(pattern, line2, 1, &match_structs, REG_NOTBOL);
-	}
-
-	if (match_found) {
-		ng = xasprintf("%s%s", growline, line2);
-		free(line);
-	} else {
-		ng = line;
-	}
-	free(growline);
-	return ng;
+	match_pos = match;
+	if (match < 0)
+		return (match_pos = 0);
+	if (match >= num_matches)
+{
+		match_pos = num_matches - 1;
+}
+	return match_pos;
 }
 
+#if ENABLE_FEATURE_LESS_REGEXP
 static void goto_match(int match)
 {
-	/* This goes to a specific match - all line positions of matches are
-	   stored within the match_lines[] array. */
-	if ((match < num_matches) && (match >= 0)) {
-		buffer_line(match_lines[match]);
-		match_pos = match;
-	}
+	buffer_line(match_lines[normalize_match_pos(match)]);
 }
 
 static void regex_process(void)
 {
 	char *uncomp_regex;
-	int i;
-	int j = 0;
-	regex_t pattern;
+
+	/* Reset variables */
+	match_lines = xrealloc(match_lines, sizeof(int));
+	match_lines[0] = -1;
+	match_pos = 0;
+	num_matches = 0;
+	if (pattern_valid) {
+		regfree(&pattern);
+		pattern_valid = 0;
+	}
 
 	/* Get the uncompiled regular expression from the user */
 	clear_line();
@@ -640,56 +646,33 @@ static void regex_process(void)
 	uncomp_regex = xmalloc_getline(inp);
 	if (!uncomp_regex || !uncomp_regex[0]) {
 		free(uncomp_regex);
-		if (num_matches)
-			goto_match((option_mask32 & LESS_STATE_MATCH_BACKWARDS)
-						? match_pos - 1 : match_pos + 1);
-		else
-			buffer_print();
+		buffer_print();
 		return;
 	}
 
 	/* Compile the regex and check for errors */
 	xregcomp(&pattern, uncomp_regex, 0);
 	free(uncomp_regex);
+	pattern_valid = 1;
 
-	if (num_matches) {
-		/* Get rid of all the highlights we added previously */
-		for (i = 0; i <= num_flines; i++) {
-			flines[i] = process_regex_on_line(flines[i], &old_pattern, 0);
+	/* Run the regex on each line of the current file */
+	for (match_pos = 0; match_pos <= num_flines; match_pos++) {
+		if (regexec(&pattern, flines[match_pos], 0, NULL, 0) == 0) {
+			match_lines = xrealloc(match_lines, (num_matches+1) * sizeof(int));
+			match_lines[num_matches++] = match_pos;
 		}
 	}
-	old_pattern = pattern;
 
-	/* Reset variables */
-	match_lines = xrealloc(match_lines, sizeof(int));
-	match_lines[0] = -1;
-	match_pos = 0;
-	num_matches = 0;
-	match_found = 0;
-	/* Run the regex on each line of the current file here */
-	for (i = 0; i <= num_flines; i++) {
-		flines[i] = process_regex_on_line(flines[i], &pattern, 1);
-		if (match_found) {
-			match_lines = xrealloc(match_lines, (j + 1) * sizeof(int));
-			match_lines[j] = i;
-			j++;
-		}
+	if (num_matches == 0 || num_flines <= height - 2) {
+		buffer_print();
+		return;
 	}
-
-	num_matches = j;
-	if ((match_lines[0] != -1) && (num_flines > height - 2)) {
-		if (option_mask32 & LESS_STATE_MATCH_BACKWARDS) {
-			for (i = 0; i < num_matches; i++) {
-				if (match_lines[i] > line_pos) {
-					match_pos = i - 1;
-					buffer_line(match_lines[match_pos]);
-					break;
-				}
-			}
-		} else
-			buffer_line(match_lines[0]);
-	} else
-		buffer_init();
+	for (match_pos = 0; match_pos < num_matches; match_pos++) {
+		if (match_lines[match_pos] > line_pos)
+			break;
+	}
+	if (option_mask32 & LESS_STATE_MATCH_BACKWARDS) match_pos--;
+	buffer_line(match_lines[normalize_match_pos(match_pos)]);
 }
 #endif
 
@@ -1111,11 +1094,16 @@ int less_main(int argc, char **argv)
 	inp = xfopen(CURRENT_TTY, "r");
 
 	get_terminal_width_height(fileno(inp), &width, &height);
+	if (width < 10 || height < 3)
+		bb_error_msg_and_die("too narrow here");
+
+	if (option_mask32 & FLAG_TILDE) empty_line_marker = "";
+
 	data_readlines();
 
+	tcgetattr(fileno(inp), &term_orig);
 	signal(SIGTERM, sig_catcher);
 	signal(SIGINT, sig_catcher);
-	tcgetattr(fileno(inp), &term_orig);
 
 	term_vi = term_orig;
 	term_vi.c_lflag &= (~ICANON & ~ECHO);