diff.c

/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "quote.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "xdiff-interface.h"
#include "color.h"
#include "attr.h"
#include "run-command.h"
#include "utf8.h"
#include "userdiff.h"
#include "sigchain.h"
#include "submodule.h"
#include "ll-merge.h"

#ifdef NO_FAST_WORKING_DIRECTORY
#define FAST_WORKING_DIRECTORY 0
#else
#define FAST_WORKING_DIRECTORY 1
#endif

static int diff_detect_rename_default;
static int diff_rename_limit_default = 200;
static int diff_suppress_blank_empty;
int diff_use_color_default = -1;
static const char *diff_word_regex_cfg;
static const char *external_diff_cmd_cfg;
int diff_auto_refresh_index = 1;
static int diff_mnemonic_prefix;
static int diff_no_prefix;
static struct diff_options default_diff_options;

static char diff_colors[][COLOR_MAXLEN] = {
	GIT_COLOR_RESET,
	GIT_COLOR_NORMAL,	/* PLAIN */
	GIT_COLOR_BOLD,		/* METAINFO */
	GIT_COLOR_CYAN,		/* FRAGINFO */
	GIT_COLOR_RED,		/* OLD */
	GIT_COLOR_GREEN,	/* NEW */
	GIT_COLOR_YELLOW,	/* COMMIT */
	GIT_COLOR_BG_RED,	/* WHITESPACE */
	GIT_COLOR_NORMAL,	/* FUNCINFO */
};

static int parse_diff_color_slot(const char *var, int ofs)
{
	if (!strcasecmp(var+ofs, "plain"))
		return DIFF_PLAIN;
	if (!strcasecmp(var+ofs, "meta"))
		return DIFF_METAINFO;
	if (!strcasecmp(var+ofs, "frag"))
		return DIFF_FRAGINFO;
	if (!strcasecmp(var+ofs, "old"))
		return DIFF_FILE_OLD;
	if (!strcasecmp(var+ofs, "new"))
		return DIFF_FILE_NEW;
	if (!strcasecmp(var+ofs, "commit"))
		return DIFF_COMMIT;
	if (!strcasecmp(var+ofs, "whitespace"))
		return DIFF_WHITESPACE;
	if (!strcasecmp(var+ofs, "func"))
		return DIFF_FUNCINFO;
	return -1;
}

static int git_config_rename(const char *var, const char *value)
{
	if (!value)
		return DIFF_DETECT_RENAME;
	if (!strcasecmp(value, "copies") || !strcasecmp(value, "copy"))
		return  DIFF_DETECT_COPY;
	return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
}

/*
 * These are to give UI layer defaults.
 * The core-level commands such as git-diff-files should
 * never be affected by the setting of diff.renames
 * the user happens to have in the configuration file.
 */
int git_diff_ui_config(const char *var, const char *value, void *cb)
{
	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
		diff_use_color_default = git_config_colorbool(var, value, -1);
		return 0;
	}
	if (!strcmp(var, "diff.renames")) {
		diff_detect_rename_default = git_config_rename(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.autorefreshindex")) {
		diff_auto_refresh_index = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.mnemonicprefix")) {
		diff_mnemonic_prefix = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.noprefix")) {
		diff_no_prefix = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.external"))
		return git_config_string(&external_diff_cmd_cfg, var, value);
	if (!strcmp(var, "diff.wordregex"))
		return git_config_string(&diff_word_regex_cfg, var, value);

	if (!strcmp(var, "diff.ignoresubmodules"))
		handle_ignore_submodules_arg(&default_diff_options, value);

	return git_diff_basic_config(var, value, cb);
}

int git_diff_basic_config(const char *var, const char *value, void *cb)
{
	if (!strcmp(var, "diff.renamelimit")) {
		diff_rename_limit_default = git_config_int(var, value);
		return 0;
	}

	switch (userdiff_config(var, value)) {
		case 0: break;
		case -1: return -1;
		default: return 0;
	}

	if (!prefixcmp(var, "diff.color.") || !prefixcmp(var, "color.diff.")) {
		int slot = parse_diff_color_slot(var, 11);
		if (slot < 0)
			return 0;
		if (!value)
			return config_error_nonbool(var);
		color_parse(value, var, diff_colors[slot]);
		return 0;
	}

	/* like GNU diff's --suppress-blank-empty option  */
	if (!strcmp(var, "diff.suppressblankempty") ||
			/* for backwards compatibility */
			!strcmp(var, "diff.suppress-blank-empty")) {
		diff_suppress_blank_empty = git_config_bool(var, value);
		return 0;
	}

	if (!prefixcmp(var, "submodule."))
		return parse_submodule_config_option(var, value);

	return git_color_default_config(var, value, cb);
}

static char *quote_two(const char *one, const char *two)
{
	int need_one = quote_c_style(one, NULL, NULL, 1);
	int need_two = quote_c_style(two, NULL, NULL, 1);
	struct strbuf res = STRBUF_INIT;

	if (need_one + need_two) {
		strbuf_addch(&res, '"');
		quote_c_style(one, &res, NULL, 1);
		quote_c_style(two, &res, NULL, 1);
		strbuf_addch(&res, '"');
	} else {
		strbuf_addstr(&res, one);
		strbuf_addstr(&res, two);
	}
	return strbuf_detach(&res, NULL);
}

static const char *external_diff(void)
{
	static const char *external_diff_cmd = NULL;
	static int done_preparing = 0;

	if (done_preparing)
		return external_diff_cmd;
	external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
	if (!external_diff_cmd)
		external_diff_cmd = external_diff_cmd_cfg;
	done_preparing = 1;
	return external_diff_cmd;
}

static struct diff_tempfile {
	const char *name; /* filename external diff should read from */
	char hex[41];
	char mode[10];
	char tmp_path[PATH_MAX];
} diff_temp[2];

typedef unsigned long (*sane_truncate_fn)(char *line, unsigned long len);

struct emit_callback {
	int color_diff;
	unsigned ws_rule;
	int blank_at_eof_in_preimage;
	int blank_at_eof_in_postimage;
	int lno_in_preimage;
	int lno_in_postimage;
	sane_truncate_fn truncate;
	const char **label_path;
	struct diff_words_data *diff_words;
	struct diff_options *opt;
	int *found_changesp;
	struct strbuf *header;
};

static int count_lines(const char *data, int size)
{
	int count, ch, completely_empty = 1, nl_just_seen = 0;
	count = 0;
	while (0 < size--) {
		ch = *data++;
		if (ch == '\n') {
			count++;
			nl_just_seen = 1;
			completely_empty = 0;
		}
		else {
			nl_just_seen = 0;
			completely_empty = 0;
		}
	}
	if (completely_empty)
		return 0;
	if (!nl_just_seen)
		count++; /* no trailing newline */
	return count;
}

static int fill_mmfile(mmfile_t *mf, struct diff_filespec *one)
{
	if (!DIFF_FILE_VALID(one)) {
		mf->ptr = (char *)""; /* does not matter */
		mf->size = 0;
		return 0;
	}
	else if (diff_populate_filespec(one, 0))
		return -1;

	mf->ptr = one->data;
	mf->size = one->size;
	return 0;
}

static int count_trailing_blank(mmfile_t *mf, unsigned ws_rule)
{
	char *ptr = mf->ptr;
	long size = mf->size;
	int cnt = 0;

	if (!size)
		return cnt;
	ptr += size - 1; /* pointing at the very end */
	if (*ptr != '\n')
		; /* incomplete line */
	else
		ptr--; /* skip the last LF */
	while (mf->ptr < ptr) {
		char *prev_eol;
		for (prev_eol = ptr; mf->ptr <= prev_eol; prev_eol--)
			if (*prev_eol == '\n')
				break;
		if (!ws_blank_line(prev_eol + 1, ptr - prev_eol, ws_rule))
			break;
		cnt++;
		ptr = prev_eol - 1;
	}
	return cnt;
}

static void check_blank_at_eof(mmfile_t *mf1, mmfile_t *mf2,
			       struct emit_callback *ecbdata)
{
	int l1, l2, at;
	unsigned ws_rule = ecbdata->ws_rule;
	l1 = count_trailing_blank(mf1, ws_rule);
	l2 = count_trailing_blank(mf2, ws_rule);
	if (l2 <= l1) {
		ecbdata->blank_at_eof_in_preimage = 0;
		ecbdata->blank_at_eof_in_postimage = 0;
		return;
	}
	at = count_lines(mf1->ptr, mf1->size);
	ecbdata->blank_at_eof_in_preimage = (at - l1) + 1;

	at = count_lines(mf2->ptr, mf2->size);
	ecbdata->blank_at_eof_in_postimage = (at - l2) + 1;
}

static void emit_line_0(struct diff_options *o, const char *set, const char *reset,
			int first, const char *line, int len)
{
	int has_trailing_newline, has_trailing_carriage_return;
	int nofirst;
	FILE *file = o->file;

	if (o->output_prefix) {
		struct strbuf *msg = NULL;
		msg = o->output_prefix(o, o->output_prefix_data);
		assert(msg);
		fwrite(msg->buf, msg->len, 1, file);
	}

	if (len == 0) {
		has_trailing_newline = (first == '\n');
		has_trailing_carriage_return = (!has_trailing_newline &&
						(first == '\r'));
		nofirst = has_trailing_newline || has_trailing_carriage_return;
	} else {
		has_trailing_newline = (len > 0 && line[len-1] == '\n');
		if (has_trailing_newline)
			len--;
		has_trailing_carriage_return = (len > 0 && line[len-1] == '\r');
		if (has_trailing_carriage_return)
			len--;
		nofirst = 0;
	}

	if (len || !nofirst) {
		fputs(set, file);
		if (!nofirst)
			fputc(first, file);
		fwrite(line, len, 1, file);
		fputs(reset, file);
	}
	if (has_trailing_carriage_return)
		fputc('\r', file);
	if (has_trailing_newline)
		fputc('\n', file);
}

static void emit_line(struct diff_options *o, const char *set, const char *reset,
		      const char *line, int len)
{
	emit_line_0(o, set, reset, line[0], line+1, len-1);
}

static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
{
	if (!((ecbdata->ws_rule & WS_BLANK_AT_EOF) &&
	      ecbdata->blank_at_eof_in_preimage &&
	      ecbdata->blank_at_eof_in_postimage &&
	      ecbdata->blank_at_eof_in_preimage <= ecbdata->lno_in_preimage &&
	      ecbdata->blank_at_eof_in_postimage <= ecbdata->lno_in_postimage))
		return 0;
	return ws_blank_line(line, len, ecbdata->ws_rule);
}

static void emit_add_line(const char *reset,
			  struct emit_callback *ecbdata,
			  const char *line, int len)
{
	const char *ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
	const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_NEW);

	if (!*ws)
		emit_line_0(ecbdata->opt, set, reset, '+', line, len);
	else if (new_blank_line_at_eof(ecbdata, line, len))
		/* Blank line at EOF - paint '+' as well */
		emit_line_0(ecbdata->opt, ws, reset, '+', line, len);
	else {
		/* Emit just the prefix, then the rest. */
		emit_line_0(ecbdata->opt, set, reset, '+', "", 0);
		ws_check_emit(line, len, ecbdata->ws_rule,
			      ecbdata->opt->file, set, reset, ws);
	}
}

static void emit_hunk_header(struct emit_callback *ecbdata,
			     const char *line, int len)
{
	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
	const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
	const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
	static const char atat[2] = { '@', '@' };
	const char *cp, *ep;
	struct strbuf msgbuf = STRBUF_INIT;
	int org_len = len;
	int i = 1;

	/*
	 * As a hunk header must begin with "@@ -<old>, +<new> @@",
	 * it always is at least 10 bytes long.
	 */
	if (len < 10 ||
	    memcmp(line, atat, 2) ||
	    !(ep = memmem(line + 2, len - 2, atat, 2))) {
		emit_line(ecbdata->opt, plain, reset, line, len);
		return;
	}
	ep += 2; /* skip over @@ */

	/* The hunk header in fraginfo color */
	strbuf_add(&msgbuf, frag, strlen(frag));
	strbuf_add(&msgbuf, line, ep - line);
	strbuf_add(&msgbuf, reset, strlen(reset));

	/*
	 * trailing "\r\n"
	 */
	for ( ; i < 3; i++)
		if (line[len - i] == '\r' || line[len - i] == '\n')
			len--;

	/* blank before the func header */
	for (cp = ep; ep - line < len; ep++)
		if (*ep != ' ' && *ep != '\t')
			break;
	if (ep != cp) {
		strbuf_add(&msgbuf, plain, strlen(plain));
		strbuf_add(&msgbuf, cp, ep - cp);
		strbuf_add(&msgbuf, reset, strlen(reset));
	}

	if (ep < line + len) {
		strbuf_add(&msgbuf, func, strlen(func));
		strbuf_add(&msgbuf, ep, line + len - ep);
		strbuf_add(&msgbuf, reset, strlen(reset));
	}

	strbuf_add(&msgbuf, line + len, org_len - len);
	emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
	strbuf_release(&msgbuf);
}

static struct diff_tempfile *claim_diff_tempfile(void) {
	int i;
	for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
		if (!diff_temp[i].name)
			return diff_temp + i;
	die("BUG: diff is failing to clean up its tempfiles");
}

static int remove_tempfile_installed;

static void remove_tempfile(void)
{
	int i;
	for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
		if (diff_temp[i].name == diff_temp[i].tmp_path)
			unlink_or_warn(diff_temp[i].name);
		diff_temp[i].name = NULL;
	}
}

static void remove_tempfile_on_signal(int signo)
{
	remove_tempfile();
	sigchain_pop(signo);
	raise(signo);
}

static void print_line_count(FILE *file, int count)
{
	switch (count) {
	case 0:
		fprintf(file, "0,0");
		break;
	case 1:
		fprintf(file, "1");
		break;
	default:
		fprintf(file, "1,%d", count);
		break;
	}
}

static void emit_rewrite_lines(struct emit_callback *ecb,
			       int prefix, const char *data, int size)
{
	const char *endp = NULL;
	static const char *nneof = " No newline at end of file\n";
	const char *old = diff_get_color(ecb->color_diff, DIFF_FILE_OLD);
	const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);

	while (0 < size) {
		int len;

		endp = memchr(data, '\n', size);
		len = endp ? (endp - data + 1) : size;
		if (prefix != '+') {
			ecb->lno_in_preimage++;
			emit_line_0(ecb->opt, old, reset, '-',
				    data, len);
		} else {
			ecb->lno_in_postimage++;
			emit_add_line(reset, ecb, data, len);
		}
		size -= len;
		data += len;
	}
	if (!endp) {
		const char *plain = diff_get_color(ecb->color_diff,
						   DIFF_PLAIN);
		emit_line_0(ecb->opt, plain, reset, '\\',
			    nneof, strlen(nneof));
	}
}

static void emit_rewrite_diff(const char *name_a,
			      const char *name_b,
			      struct diff_filespec *one,
			      struct diff_filespec *two,
			      struct userdiff_driver *textconv_one,
			      struct userdiff_driver *textconv_two,
			      struct diff_options *o)
{
	int lc_a, lc_b;
	int color_diff = DIFF_OPT_TST(o, COLOR_DIFF);
	const char *name_a_tab, *name_b_tab;
	const char *metainfo = diff_get_color(color_diff, DIFF_METAINFO);
	const char *fraginfo = diff_get_color(color_diff, DIFF_FRAGINFO);
	const char *reset = diff_get_color(color_diff, DIFF_RESET);
	static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
	const char *a_prefix, *b_prefix;
	char *data_one, *data_two;
	size_t size_one, size_two;
	struct emit_callback ecbdata;
	char *line_prefix = "";
	struct strbuf *msgbuf;

	if (o && o->output_prefix) {
		msgbuf = o->output_prefix(o, o->output_prefix_data);
		line_prefix = msgbuf->buf;
	}

	if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
		a_prefix = o->b_prefix;
		b_prefix = o->a_prefix;
	} else {
		a_prefix = o->a_prefix;
		b_prefix = o->b_prefix;
	}

	name_a += (*name_a == '/');
	name_b += (*name_b == '/');
	name_a_tab = strchr(name_a, ' ') ? "\t" : "";
	name_b_tab = strchr(name_b, ' ') ? "\t" : "";

	strbuf_reset(&a_name);
	strbuf_reset(&b_name);
	quote_two_c_style(&a_name, a_prefix, name_a, 0);
	quote_two_c_style(&b_name, b_prefix, name_b, 0);

	size_one = fill_textconv(textconv_one, one, &data_one);
	size_two = fill_textconv(textconv_two, two, &data_two);

	memset(&ecbdata, 0, sizeof(ecbdata));
	ecbdata.color_diff = color_diff;
	ecbdata.found_changesp = &o->found_changes;
	ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
	ecbdata.opt = o;
	if (ecbdata.ws_rule & WS_BLANK_AT_EOF) {
		mmfile_t mf1, mf2;
		mf1.ptr = (char *)data_one;
		mf2.ptr = (char *)data_two;
		mf1.size = size_one;
		mf2.size = size_two;
		check_blank_at_eof(&mf1, &mf2, &ecbdata);
	}
	ecbdata.lno_in_preimage = 1;
	ecbdata.lno_in_postimage = 1;

	lc_a = count_lines(data_one, size_one);
	lc_b = count_lines(data_two, size_two);
	fprintf(o->file,
		"%s%s--- %s%s%s\n%s%s+++ %s%s%s\n%s%s@@ -",
		line_prefix, metainfo, a_name.buf, name_a_tab, reset,
		line_prefix, metainfo, b_name.buf, name_b_tab, reset,
		line_prefix, fraginfo);
	print_line_count(o->file, lc_a);
	fprintf(o->file, " +");
	print_line_count(o->file, lc_b);
	fprintf(o->file, " @@%s\n", reset);
	if (lc_a)
		emit_rewrite_lines(&ecbdata, '-', data_one, size_one);
	if (lc_b)
		emit_rewrite_lines(&ecbdata, '+', data_two, size_two);
	if (textconv_one)
		free((char *)data_one);
	if (textconv_two)
		free((char *)data_two);
}

struct diff_words_buffer {
	mmfile_t text;
	long alloc;
	struct diff_words_orig {
		const char *begin, *end;
	} *orig;
	int orig_nr, orig_alloc;
};

static void diff_words_append(char *line, unsigned long len,
		struct diff_words_buffer *buffer)
{
	ALLOC_GROW(buffer->text.ptr, buffer->text.size + len, buffer->alloc);
	line++;
	len--;
	memcpy(buffer->text.ptr + buffer->text.size, line, len);
	buffer->text.size += len;
	buffer->text.ptr[buffer->text.size] = '\0';
}

struct diff_words_style_elem
{
	const char *prefix;
	const char *suffix;
	const char *color; /* NULL; filled in by the setup code if
			    * color is enabled */
};

struct diff_words_style
{
	enum diff_words_type type;
	struct diff_words_style_elem new, old, ctx;
	const char *newline;
};

struct diff_words_style diff_words_styles[] = {
	{ DIFF_WORDS_PORCELAIN, {"+", "\n"}, {"-", "\n"}, {" ", "\n"}, "~\n" },
	{ DIFF_WORDS_PLAIN, {"{+", "+}"}, {"[-", "-]"}, {"", ""}, "\n" },
	{ DIFF_WORDS_COLOR, {"", ""}, {"", ""}, {"", ""}, "\n" }
};

struct diff_words_data {
	struct diff_words_buffer minus, plus;
	const char *current_plus;
	int last_minus;
	struct diff_options *opt;
	regex_t *word_regex;
	enum diff_words_type type;
	struct diff_words_style *style;
};

static int fn_out_diff_words_write_helper(FILE *fp,
					  struct diff_words_style_elem *st_el,
					  const char *newline,
					  size_t count, const char *buf,
					  const char *line_prefix)
{
	int print = 0;

	while (count) {
		char *p = memchr(buf, '\n', count);
		if (print)
			fputs(line_prefix, fp);
		if (p != buf) {
			if (st_el->color && fputs(st_el->color, fp) < 0)
				return -1;
			if (fputs(st_el->prefix, fp) < 0 ||
			    fwrite(buf, p ? p - buf : count, 1, fp) != 1 ||
			    fputs(st_el->suffix, fp) < 0)
				return -1;
			if (st_el->color && *st_el->color
			    && fputs(GIT_COLOR_RESET, fp) < 0)
				return -1;
		}
		if (!p)
			return 0;
		if (fputs(newline, fp) < 0)
			return -1;
		count -= p + 1 - buf;
		buf = p + 1;
		print = 1;
	}
	return 0;
}

/*
 * '--color-words' algorithm can be described as:
 *
 *   1. collect a the minus/plus lines of a diff hunk, divided into
 *      minus-lines and plus-lines;
 *
 *   2. break both minus-lines and plus-lines into words and
 *      place them into two mmfile_t with one word for each line;
 *
 *   3. use xdiff to run diff on the two mmfile_t to get the words level diff;
 *
 * And for the common parts of the both file, we output the plus side text.
 * diff_words->current_plus is used to trace the current position of the plus file
 * which printed. diff_words->last_minus is used to trace the last minus word
 * printed.
 *
 * For '--graph' to work with '--color-words', we need to output the graph prefix
 * on each line of color words output. Generally, there are two conditions on
 * which we should output the prefix.
 *
 *   1. diff_words->last_minus == 0 &&
 *      diff_words->current_plus == diff_words->plus.text.ptr
 *
 *      that is: the plus text must start as a new line, and if there is no minus
 *      word printed, a graph prefix must be printed.
 *
 *   2. diff_words->current_plus > diff_words->plus.text.ptr &&
 *      *(diff_words->current_plus - 1) == '\n'
 *
 *      that is: a graph prefix must be printed following a '\n'
 */
static int color_words_output_graph_prefix(struct diff_words_data *diff_words)
{
	if ((diff_words->last_minus == 0 &&
		diff_words->current_plus == diff_words->plus.text.ptr) ||
		(diff_words->current_plus > diff_words->plus.text.ptr &&
		*(diff_words->current_plus - 1) == '\n')) {
		return 1;
	} else {
		return 0;
	}
}

static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
{
	struct diff_words_data *diff_words = priv;
	struct diff_words_style *style = diff_words->style;
	int minus_first, minus_len, plus_first, plus_len;
	const char *minus_begin, *minus_end, *plus_begin, *plus_end;
	struct diff_options *opt = diff_words->opt;
	struct strbuf *msgbuf;
	char *line_prefix = "";

	if (line[0] != '@' || parse_hunk_header(line, len,
			&minus_first, &minus_len, &plus_first, &plus_len))
		return;

	assert(opt);
	if (opt->output_prefix) {
		msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
		line_prefix = msgbuf->buf;
	}

	/* POSIX requires that first be decremented by one if len == 0... */
	if (minus_len) {
		minus_begin = diff_words->minus.orig[minus_first].begin;
		minus_end =
			diff_words->minus.orig[minus_first + minus_len - 1].end;
	} else
		minus_begin = minus_end =
			diff_words->minus.orig[minus_first].end;

	if (plus_len) {
		plus_begin = diff_words->plus.orig[plus_first].begin;
		plus_end = diff_words->plus.orig[plus_first + plus_len - 1].end;
	} else
		plus_begin = plus_end = diff_words->plus.orig[plus_first].end;

	if (color_words_output_graph_prefix(diff_words)) {
		fputs(line_prefix, diff_words->opt->file);
	}
	if (diff_words->current_plus != plus_begin) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->ctx, style->newline,
				plus_begin - diff_words->current_plus,
				diff_words->current_plus, line_prefix);
		if (*(plus_begin - 1) == '\n')
			fputs(line_prefix, diff_words->opt->file);
	}
	if (minus_begin != minus_end) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->old, style->newline,
				minus_end - minus_begin, minus_begin,
				line_prefix);
	}
	if (plus_begin != plus_end) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->new, style->newline,
				plus_end - plus_begin, plus_begin,
				line_prefix);
	}

	diff_words->current_plus = plus_end;
	diff_words->last_minus = minus_first;
}

/* This function starts looking at *begin, and returns 0 iff a word was found. */
static int find_word_boundaries(mmfile_t *buffer, regex_t *word_regex,
		int *begin, int *end)
{
	if (word_regex && *begin < buffer->size) {
		regmatch_t match[1];
		if (!regexec(word_regex, buffer->ptr + *begin, 1, match, 0)) {
			char *p = memchr(buffer->ptr + *begin + match[0].rm_so,
					'\n', match[0].rm_eo - match[0].rm_so);
			*end = p ? p - buffer->ptr : match[0].rm_eo + *begin;
			*begin += match[0].rm_so;
			return *begin >= *end;
		}
		return -1;
	}

	/* find the next word */
	while (*begin < buffer->size && isspace(buffer->ptr[*begin]))
		(*begin)++;
	if (*begin >= buffer->size)
		return -1;

	/* find the end of the word */
	*end = *begin + 1;
	while (*end < buffer->size && !isspace(buffer->ptr[*end]))
		(*end)++;

	return 0;
}

/*
 * This function splits the words in buffer->text, stores the list with
 * newline separator into out, and saves the offsets of the original words
 * in buffer->orig.
 */
static void diff_words_fill(struct diff_words_buffer *buffer, mmfile_t *out,
		regex_t *word_regex)
{
	int i, j;
	long alloc = 0;

	out->size = 0;
	out->ptr = NULL;

	/* fake an empty "0th" word */
	ALLOC_GROW(buffer->orig, 1, buffer->orig_alloc);
	buffer->orig[0].begin = buffer->orig[0].end = buffer->text.ptr;
	buffer->orig_nr = 1;

	for (i = 0; i < buffer->text.size; i++) {
		if (find_word_boundaries(&buffer->text, word_regex, &i, &j))
			return;

		/* store original boundaries */
		ALLOC_GROW(buffer->orig, buffer->orig_nr + 1,
				buffer->orig_alloc);
		buffer->orig[buffer->orig_nr].begin = buffer->text.ptr + i;
		buffer->orig[buffer->orig_nr].end = buffer->text.ptr + j;
		buffer->orig_nr++;

		/* store one word */
		ALLOC_GROW(out->ptr, out->size + j - i + 1, alloc);
		memcpy(out->ptr + out->size, buffer->text.ptr + i, j - i);
		out->ptr[out->size + j - i] = '\n';
		out->size += j - i + 1;

		i = j - 1;
	}
}

/* this executes the word diff on the accumulated buffers */
static void diff_words_show(struct diff_words_data *diff_words)
{
	xpparam_t xpp;
	xdemitconf_t xecfg;
	mmfile_t minus, plus;
	struct diff_words_style *style = diff_words->style;

	struct diff_options *opt = diff_words->opt;
	struct strbuf *msgbuf;
	char *line_prefix = "";

	assert(opt);
	if (opt->output_prefix) {
		msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
		line_prefix = msgbuf->buf;
	}

	/* special case: only removal */
	if (!diff_words->plus.text.size) {
		fputs(line_prefix, diff_words->opt->file);
		fn_out_diff_words_write_helper(diff_words->opt->file,
			&style->old, style->newline,
			diff_words->minus.text.size,
			diff_words->minus.text.ptr, line_prefix);
		diff_words->minus.text.size = 0;
		return;
	}

	diff_words->current_plus = diff_words->plus.text.ptr;
	diff_words->last_minus = 0;

	memset(&xpp, 0, sizeof(xpp));
	memset(&xecfg, 0, sizeof(xecfg));
	diff_words_fill(&diff_words->minus, &minus, diff_words->word_regex);
	diff_words_fill(&diff_words->plus, &plus, diff_words->word_regex);
	xpp.flags = 0;
	/* as only the hunk header will be parsed, we need a 0-context */
	xecfg.ctxlen = 0;
	xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
		      &xpp, &xecfg);
	free(minus.ptr);
	free(plus.ptr);
	if (diff_words->current_plus != diff_words->plus.text.ptr +
			diff_words->plus.text.size) {
		if (color_words_output_graph_prefix(diff_words))
			fputs(line_prefix, diff_words->opt->file);
		fn_out_diff_words_write_helper(diff_words->opt->file,
			&style->ctx, style->newline,
			diff_words->plus.text.ptr + diff_words->plus.text.size
			- diff_words->current_plus, diff_words->current_plus,
			line_prefix);
	}
	diff_words->minus.text.size = diff_words->plus.text.size = 0;
}

/* In "color-words" mode, show word-diff of words accumulated in the buffer */
static void diff_words_flush(struct emit_callback *ecbdata)
{
	if (ecbdata->diff_words->minus.text.size ||
	    ecbdata->diff_words->plus.text.size)
		diff_words_show(ecbdata->diff_words);
}

static void free_diff_words_data(struct emit_callback *ecbdata)
{
	if (ecbdata->diff_words) {
		diff_words_flush(ecbdata);
		free (ecbdata->diff_words->minus.text.ptr);
		free (ecbdata->diff_words->minus.orig);
		free (ecbdata->diff_words->plus.text.ptr);
		free (ecbdata->diff_words->plus.orig);
		if (ecbdata->diff_words->word_regex) {
			regfree(ecbdata->diff_words->word_regex);
			free(ecbdata->diff_words->word_regex);
		}
		free(ecbdata->diff_words);
		ecbdata->diff_words = NULL;
	}
}

const char *diff_get_color(int diff_use_color, enum color_diff ix)
{
	if (diff_use_color)
		return diff_colors[ix];
	return "";
}

static unsigned long sane_truncate_line(struct emit_callback *ecb, char *line, unsigned long len)
{
	const char *cp;
	unsigned long allot;
	size_t l = len;

	if (ecb->truncate)
		return ecb->truncate(line, len);
	cp = line;
	allot = l;
	while (0 < l) {
		(void) utf8_width(&cp, &l);
		if (!cp)
			break; /* truncated in the middle? */
	}
	return allot - l;
}

static void find_lno(const char *line, struct emit_callback *ecbdata)
{
	const char *p;
	ecbdata->lno_in_preimage = 0;
	ecbdata->lno_in_postimage = 0;
	p = strchr(line, '-');
	if (!p)
		return; /* cannot happen */
	ecbdata->lno_in_preimage = strtol(p + 1, NULL, 10);
	p = strchr(p, '+');
	if (!p)
		return; /* cannot happen */
	ecbdata->lno_in_postimage = strtol(p + 1, NULL, 10);
}

static void fn_out_consume(void *priv, char *line, unsigned long len)
{
	struct emit_callback *ecbdata = priv;
	const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
	struct diff_options *o = ecbdata->opt;
	char *line_prefix = "";
	struct strbuf *msgbuf;

	if (o && o->output_prefix) {
		msgbuf = o->output_prefix(o, o->output_prefix_data);
		line_prefix = msgbuf->buf;
	}

	if (ecbdata->header) {
		fprintf(ecbdata->opt->file, "%s", ecbdata->header->buf);
		strbuf_reset(ecbdata->header);
		ecbdata->header = NULL;
	}
	*(ecbdata->found_changesp) = 1;

	if (ecbdata->label_path[0]) {
		const char *name_a_tab, *name_b_tab;

		name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
		name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";

		fprintf(ecbdata->opt->file, "%s%s--- %s%s%s\n",
			line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);