Merge branch 'ro/ssdiff'

13 files changed, 586 insertions, 25 deletions

diff --git a/Makefile b/Makefile
index 4e101d3..f8a4d47 100644
--- a/Makefile
+++ b/Makefile
@@ -93,6 +93,7 @@ OBJECTS += ui-refs.o
 OBJECTS += ui-repolist.o
 OBJECTS += ui-shared.o
 OBJECTS += ui-snapshot.o
+OBJECTS += ui-ssdiff.o
 OBJECTS += ui-stats.o
 OBJECTS += ui-summary.o
 OBJECTS += ui-tag.o
diff --git a/cgit.c b/cgit.c
index 08cb5d2..4f68a4b 100644
--- a/cgit.c
+++ b/cgit.c
@@ -184,6 +184,8 @@ void config_cb(const char *name, const char *value)
                 ctx.cfg.summary_branches = atoi(value);
         else if (!strcmp(name, "summary-tags"))
                 ctx.cfg.summary_tags = atoi(value);
+        else if (!strcmp(name, "side-by-side-diffs"))
+                ctx.cfg.ssdiff = atoi(value);
         else if (!strcmp(name, "agefile"))
                 ctx.cfg.agefile = xstrdup(value);
         else if (!strcmp(name, "renamelimit"))
@@ -242,6 +244,8 @@ static void querystring_cb(const char *name, const char *value)
                 ctx.qry.showmsg = atoi(value);
         } else if (!strcmp(name, "period")) {
                 ctx.qry.period = xstrdup(value);
+        } else if (!strcmp(name, "ss")) {
+                ctx.qry.ssdiff = atoi(value);
         }
 }
 
@@ -284,6 +288,7 @@ static void prepare_context(struct cgit_context *ctx)
         ctx->cfg.summary_branches = 10;
         ctx->cfg.summary_log = 10;
         ctx->cfg.summary_tags = 10;
+        ctx->cfg.ssdiff = 0;
         ctx->env.cgit_config = xstrdupn(getenv("CGIT_CONFIG"));
         ctx->env.http_host = xstrdupn(getenv("HTTP_HOST"));
         ctx->env.https = xstrdupn(getenv("HTTPS"));
diff --git a/cgit.css b/cgit.css
index ef7d3c1..0cb894a 100644
--- a/cgit.css
+++ b/cgit.css
@@ -606,3 +606,102 @@ table.hgraph div.bar {
         background-color: #eee;
         height: 1em;
 }
+
+table.ssdiff {
+        width: 100%;
+}
+
+table.ssdiff td {
+        font-size: 75%;
+        font-family: monospace;
+        white-space: pre;
+        padding: 1px 4px 1px 4px;
+        border-left: solid 1px #aaa;
+        border-right: solid 1px #aaa;
+}
+
+table.ssdiff td.add {
+        color: black;
+        background: #cfc;
+        min-width: 50%;
+}
+
+table.ssdiff td.add_dark {
+        color: black;
+        background: #aca;
+        min-width: 50%;
+}
+
+table.ssdiff span.add {
+        background: #cfc;
+        font-weight: bold;
+}
+
+table.ssdiff td.del {
+        color: black;
+        background: #fcc;
+        min-width: 50%;
+}
+
+table.ssdiff td.del_dark {
+        color: black;
+        background: #caa;
+        min-width: 50%;
+}
+
+table.ssdiff span.del {
+        background: #fcc;
+        font-weight: bold;
+}
+
+table.ssdiff td.changed {
+        color: black;
+        background: #ffc;
+        min-width: 50%;
+}
+
+table.ssdiff td.changed_dark {
+        color: black;
+        background: #cca;
+        min-width: 50%;
+}
+
+table.ssdiff td.lineno {
+        color: black;
+        background: #eee;
+        text-align: right;
+        width: 3em;
+        min-width: 3em;
+}
+
+table.ssdiff td.hunk {
+        color: #black;
+        background: #ccf;
+        border-top: solid 1px #aaa;
+        border-bottom: solid 1px #aaa;
+}
+
+table.ssdiff td.head {
+        border-top: solid 1px #aaa;
+        border-bottom: solid 1px #aaa;
+}
+
+table.ssdiff td.head div.head {
+        font-weight: bold;
+        color: black;
+}
+
+table.ssdiff td.foot {
+        border-top: solid 1px #aaa;
+        border-left: none;
+        border-right: none;
+        border-bottom: none;
+}
+
+table.ssdiff td.space {
+        border: none;
+}
+
+table.ssdiff td.space div {
+        min-height: 3em;
+}
\ No newline at end of file
diff --git a/cgit.h b/cgit.h
index 39853df..5941ec0 100644
--- a/cgit.h
+++ b/cgit.h
@@ -143,6 +143,7 @@ struct cgit_query {
         int nohead;
         char *sort;
         int showmsg;
+        int ssdiff;
 };
 
 struct cgit_config {
@@ -195,6 +196,7 @@ struct cgit_config {
         int summary_branches;
         int summary_log;
         int summary_tags;
+        int ssdiff;
         struct string_list mimetypes;
         struct cgit_filter *about_filter;
         struct cgit_filter *commit_filter;
diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index e69140b..70e4c78 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -245,6 +245,10 @@ section::
         after this option will inherit the current section name. Default value:
         none.
 
+side-by-side-diffs::
+        If set to "1" shows side-by-side diffs instead of unidiffs per
+        default. Default value: "0".
+
 snapshots::
         Text which specifies the default set of snapshot formats generated by
         cgit. The value is a space-separated list of zero or more of the
diff --git a/ui-commit.c b/ui-commit.c
index f5b0ae5..b5e3c01 100644
--- a/ui-commit.c
+++ b/ui-commit.c
@@ -58,9 +58,14 @@ void cgit_print_commit(char *hex)
         html("</td></tr>\n");
         html("<tr><th>commit</th><td colspan='2' class='sha1'>");
         tmp = sha1_to_hex(commit->object.sha1);
-        cgit_commit_link(tmp, NULL, NULL, ctx.qry.head, tmp);
+        cgit_commit_link(tmp, NULL, NULL, ctx.qry.head, tmp, 0);
         html(" (");
         cgit_patch_link("patch", NULL, NULL, NULL, tmp);
+        html(") (");
+        if ((ctx.qry.ssdiff && !ctx.cfg.ssdiff) || (!ctx.qry.ssdiff && ctx.cfg.ssdiff))
+                cgit_commit_link("unidiff", NULL, NULL, ctx.qry.head, tmp, 1);
+        else
+                cgit_commit_link("side-by-side diff", NULL, NULL, ctx.qry.head, tmp, 1);
         html(")</td></tr>\n");
         html("<tr><th>tree</th><td colspan='2' class='sha1'>");
         tmp = xstrdup(hex);
@@ -78,10 +83,10 @@ void cgit_print_commit(char *hex)
                 html("<tr><th>parent</th>"
                      "<td colspan='2' class='sha1'>");
                 cgit_commit_link(sha1_to_hex(p->item->object.sha1), NULL, NULL,
-                                 ctx.qry.head, sha1_to_hex(p->item->object.sha1));
+                                 ctx.qry.head, sha1_to_hex(p->item->object.sha1), 0);
                 html(" (");
                 cgit_diff_link("diff", NULL, NULL, ctx.qry.head, hex,
-                               sha1_to_hex(p->item->object.sha1), NULL);
+                               sha1_to_hex(p->item->object.sha1), NULL, 0);
                 html(")</td></tr>");
                 parents++;
         }
diff --git a/ui-diff.c b/ui-diff.c
index 2196745..a92a768 100644
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -9,6 +9,7 @@
 #include "cgit.h"
 #include "html.h"
 #include "ui-shared.h"
+#include "ui-ssdiff.h"
 
 unsigned char old_rev_sha1[20];
 unsigned char new_rev_sha1[20];
@@ -32,6 +33,7 @@ static struct fileinfo {
         int binary:1;
 } *items;
 
+static int use_ssdiff = 0;
 
 static void print_fileinfo(struct fileinfo *info)
 {
@@ -83,7 +85,7 @@ static void print_fileinfo(struct fileinfo *info)
         }
         htmlf("</td><td class='%s'>", class);
         cgit_diff_link(info->new_path, NULL, NULL, ctx.qry.head, ctx.qry.sha1,
-                       ctx.qry.sha2, info->new_path);
+                       ctx.qry.sha2, info->new_path, 0);
         if (info->status == DIFF_STATUS_COPIED || info->status == DIFF_STATUS_RENAMED)
                 htmlf(" (%s from %s)",
                       info->status == DIFF_STATUS_COPIED ? "copied" : "renamed",
@@ -158,7 +160,7 @@ void cgit_print_diffstat(const unsigned char *old_sha1,
 
         html("<div class='diffstat-header'>");
         cgit_diff_link("Diffstat", NULL, NULL, ctx.qry.head, ctx.qry.sha1,
-                       ctx.qry.sha2, NULL);
+                       ctx.qry.sha2, NULL, 0);
         html("</div>");
         html("<table summary='diffstat' class='diffstat'>");
         max_changes = 0;
@@ -246,26 +248,54 @@ static void header(unsigned char *sha1, char *path1, int mode1,
         html("</div>");
 }
 
+static void print_ssdiff_link()
+{
+        if (!strcmp(ctx.qry.page, "diff")) {
+                if (use_ssdiff)
+                        cgit_diff_link("Unidiff", NULL, NULL, ctx.qry.head,
+                                       ctx.qry.sha1, ctx.qry.sha2, ctx.qry.path, 1);
+                else
+                        cgit_diff_link("Side-by-side diff", NULL, NULL,
+                                       ctx.qry.head, ctx.qry.sha1,
+                                       ctx.qry.sha2, ctx.qry.path, 1);
+        }
+}
+
 static void filepair_cb(struct diff_filepair *pair)
 {
         unsigned long old_size = 0;
         unsigned long new_size = 0;
         int binary = 0;
+        linediff_fn print_line_fn = print_line;
 
+        if (use_ssdiff) {
+                cgit_ssdiff_header_begin();
+                print_line_fn = cgit_ssdiff_line_cb;
+        }
         header(pair->one->sha1, pair->one->path, pair->one->mode,
                pair->two->sha1, pair->two->path, pair->two->mode);
+        if (use_ssdiff)
+                cgit_ssdiff_header_end();
         if (S_ISGITLINK(pair->one->mode) || S_ISGITLINK(pair->two->mode)) {
                 if (S_ISGITLINK(pair->one->mode))
-                        print_line(fmt("-Subproject %s", sha1_to_hex(pair->one->sha1)), 52);
+                        print_line_fn(fmt("-Subproject %s", sha1_to_hex(pair->one->sha1)), 52);
                 if (S_ISGITLINK(pair->two->mode))
-                        print_line(fmt("+Subproject %s", sha1_to_hex(pair->two->sha1)), 52);
+                        print_line_fn(fmt("+Subproject %s", sha1_to_hex(pair->two->sha1)), 52);
+                if (use_ssdiff)
+                        cgit_ssdiff_footer();
                 return;
         }
-        if (cgit_diff_files(pair->one->sha1, pair->two->sha1, &old_size, 
-                            &new_size, &binary, print_line))
+        if (cgit_diff_files(pair->one->sha1, pair->two->sha1, &old_size,
+                            &new_size, &binary, print_line_fn))
                 cgit_print_error("Error running diff");
-        if (binary)
-                html("Binary files differ");
+        if (binary) {
+                if (use_ssdiff)
+                        html("<tr><td colspan='4'>Binary files differ</td></tr>");
+                else
+                        html("Binary files differ");
+        }
+        if (use_ssdiff)
+                cgit_ssdiff_footer();
 }
 
 void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefix)
@@ -303,11 +333,21 @@ void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefi
                 if (!commit2 || parse_commit(commit2))
                         cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(old_rev_sha1)));
         }
+
+        if ((ctx.qry.ssdiff && !ctx.cfg.ssdiff) || (!ctx.qry.ssdiff && ctx.cfg.ssdiff))
+                use_ssdiff = 1;
+
+        print_ssdiff_link();
         cgit_print_diffstat(old_rev_sha1, new_rev_sha1);
 
-        html("<table summary='diff' class='diff'>");
-        html("<tr><td>");
+        if (use_ssdiff) {
+                html("<table summary='ssdiff' class='ssdiff'>");
+        } else {
+                html("<table summary='diff' class='diff'>");
+                html("<tr><td>");
+        }
         cgit_diff_tree(old_rev_sha1, new_rev_sha1, filepair_cb, prefix);
-        html("</td></tr>");
+        if (!use_ssdiff)
+                html("</td></tr>");
         html("</table>");
 }
diff --git a/ui-log.c b/ui-log.c
index f3132c9..0947604 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -66,7 +66,7 @@ void show_commit_decorations(struct commit *commit)
                 else {
                         strncpy(buf, deco->name, sizeof(buf) - 1);
                         cgit_commit_link(buf, NULL, "deco", ctx.qry.head,
-                                sha1_to_hex(commit->object.sha1));
+                                sha1_to_hex(commit->object.sha1), 0);
                 }
                 deco = deco->next;
         }
@@ -89,7 +89,7 @@ void print_commit(struct commit *commit)
         htmlf("</td><td%s>",
                 ctx.qry.showmsg ? " class='logsubject'" : "");
         cgit_commit_link(info->subject, NULL, NULL, ctx.qry.head,
-                         sha1_to_hex(commit->object.sha1));
+                         sha1_to_hex(commit->object.sha1), 0);
         show_commit_decorations(commit);
         html("</td><td>");
         html_txt(info->author);
diff --git a/ui-refs.c b/ui-refs.c
index d3b4f6e..33d9bec 100644
--- a/ui-refs.c
+++ b/ui-refs.c
@@ -74,7 +74,7 @@ static int print_branch(struct refinfo *ref)
         html("</td><td>");
 
         if (ref->object->type == OBJ_COMMIT) {
-                cgit_commit_link(info->subject, NULL, NULL, name, NULL);
+                cgit_commit_link(info->subject, NULL, NULL, name, NULL, 0);
                 html("</td><td>");
                 html_txt(info->author);
                 html("</td><td colspan='2'>");
diff --git a/ui-shared.c b/ui-shared.c
index 3a9e67b..08ea003 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -317,7 +317,7 @@ void cgit_log_link(char *name, char *title, char *class, char *head,
 }
 
 void cgit_commit_link(char *name, char *title, char *class, char *head,
-                      char *rev)
+                      char *rev, int toggle_ssdiff)
 {
         if (strlen(name) > ctx.cfg.max_msg_len && ctx.cfg.max_msg_len >= 15) {
                 name[ctx.cfg.max_msg_len] = '\0';
@@ -325,7 +325,23 @@ void cgit_commit_link(char *name, char *title, char *class, char *head,
                 name[ctx.cfg.max_msg_len - 2] = '.';
                 name[ctx.cfg.max_msg_len - 3] = '.';
         }
-        reporevlink("commit", name, title, class, head, rev, NULL);
+
+        char *delim;
+
+        delim = repolink(title, class, "commit", head, NULL);
+        if (rev && strcmp(rev, ctx.qry.head)) {
+                html(delim);
+                html("id=");
+                html_url_arg(rev);
+                delim = "&amp;";
+        }
+        if ((ctx.qry.ssdiff && !toggle_ssdiff) || (!ctx.qry.ssdiff && toggle_ssdiff)) {
+                html(delim);
+                html("ss=1");
+        }
+        html("'>");
+        html_txt(name);
+        html("</a>");
 }
 
 void cgit_refs_link(char *name, char *title, char *class, char *head,
@@ -341,7 +357,8 @@ void cgit_snapshot_link(char *name, char *title, char *class, char *head,
 }
 
 void cgit_diff_link(char *name, char *title, char *class, char *head,
-                    char *new_rev, char *old_rev, char *path)
+                    char *new_rev, char *old_rev, char *path,
+                    int toggle_ssdiff)
 {
         char *delim;
 
@@ -356,6 +373,11 @@ void cgit_diff_link(char *name, char *title, char *class, char *head,
                 html(delim);
                 html("id2=");
                 html_url_arg(old_rev);
+                delim = "&amp;";
+        }
+        if ((ctx.qry.ssdiff && !toggle_ssdiff) || (!ctx.qry.ssdiff && toggle_ssdiff)) {
+                html(delim);
+                html("ss=1");
         }
         html("'>");
         html_txt(name);
@@ -383,7 +405,7 @@ void cgit_object_link(struct object *obj)
         shortrev[10] = '\0';
         if (obj->type == OBJ_COMMIT) {
                 cgit_commit_link(fmt("commit %s...", shortrev), NULL, NULL,
-                                 ctx.qry.head, fullrev);
+                                 ctx.qry.head, fullrev, 0);
                 return;
         } else if (obj->type == OBJ_TREE)
                 page = "tree";
@@ -695,9 +717,9 @@ void cgit_print_pageheader(struct cgit_context *ctx)
                 cgit_tree_link("tree", NULL, hc(cmd, "tree"), ctx->qry.head,
                                ctx->qry.sha1, NULL);
                 cgit_commit_link("commit", NULL, hc(cmd, "commit"),
-                                 ctx->qry.head, ctx->qry.sha1);
+                                 ctx->qry.head, ctx->qry.sha1, 0);
                 cgit_diff_link("diff", NULL, hc(cmd, "diff"), ctx->qry.head,
-                               ctx->qry.sha1, ctx->qry.sha2, NULL);
+                               ctx->qry.sha1, ctx->qry.sha2, NULL, 0);
                 if (ctx->repo->max_stats)
                         cgit_stats_link("stats", NULL, hc(cmd, "stats"),
                                         ctx->qry.head, NULL);
diff --git a/ui-shared.h b/ui-shared.h
index b12aa89..9ebc1f9 100644
--- a/ui-shared.h
+++ b/ui-shared.h
@@ -23,7 +23,7 @@ extern void cgit_log_link(char *name, char *title, char *class, char *head,
                           char *rev, char *path, int ofs, char *grep,
                           char *pattern, int showmsg);
 extern void cgit_commit_link(char *name, char *title, char *class, char *head,
-                             char *rev);
+                             char *rev, int toggle_ssdiff);
 extern void cgit_patch_link(char *name, char *title, char *class, char *head,
                             char *rev);
 extern void cgit_refs_link(char *name, char *title, char *class, char *head,
@@ -31,7 +31,8 @@ extern void cgit_refs_link(char *name, char *title, char *class, char *head,
 extern void cgit_snapshot_link(char *name, char *title, char *class,
                                char *head, char *rev, char *archivename);
 extern void cgit_diff_link(char *name, char *title, char *class, char *head,
-                           char *new_rev, char *old_rev, char *path);
+                           char *new_rev, char *old_rev, char *path,
+                           int toggle_ssdiff);
 extern void cgit_stats_link(char *name, char *title, char *class, char *head,
                             char *path);
 extern void cgit_object_link(struct object *obj);
diff --git a/ui-ssdiff.c b/ui-ssdiff.c
new file mode 100644
index 0000000..408e620
--- /dev/null
+++ b/ui-ssdiff.c
@@ -0,0 +1,369 @@
+#include "cgit.h"
+#include "html.h"
+#include "ui-shared.h"
+
+extern int use_ssdiff;
+
+static int current_old_line, current_new_line;
+
+struct deferred_lines {
+        int line_no;
+        char *line;
+        struct deferred_lines *next;
+};
+
+static struct deferred_lines *deferred_old, *deferred_old_last;
+static struct deferred_lines *deferred_new, *deferred_new_last;
+
+static char *longest_common_subsequence(char *A, char *B)
+{
+        int i, j, ri;
+        int m = strlen(A);
+        int n = strlen(B);
+        int L[m + 1][n + 1];
+        int tmp1, tmp2;
+        int lcs_length;
+        char *result;
+
+        for (i = m; i >= 0; i--) {
+                for (j = n; j >= 0; j--) {
+                        if (A[i] == '\0' || B[j] == '\0') {
+                                L[i][j] = 0;
+                        } else if (A[i] == B[j]) {
+                                L[i][j] = 1 + L[i + 1][j + 1];
+                        } else {
+                                tmp1 = L[i + 1][j];
+                                tmp2 = L[i][j + 1];
+                                L[i][j] = (tmp1 > tmp2 ? tmp1 : tmp2);
+                        }
+                }
+        }
+
+        lcs_length = L[0][0];
+        result = xmalloc(lcs_length + 2);
+        memset(result, 0, sizeof(*result) * (lcs_length + 2));
+
+        ri = 0;
+        i = 0;
+        j = 0;
+        while (i < m && j < n) {
+                if (A[i] == B[j]) {
+                        result[ri] = A[i];
+                        ri += 1;
+                        i += 1;
+                        j += 1;
+                } else if (L[i + 1][j] >= L[i][j + 1]) {
+                        i += 1;
+                } else {
+                        j += 1;
+                }
+        }
+        return result;
+}
+
+static int line_from_hunk(char *line, char type)
+{
+        char *buf1, *buf2;
+        int len;
+
+        buf1 = strchr(line, type);
+        if (buf1 == NULL)
+                return 0;
+        buf1 += 1;
+        buf2 = strchr(buf1, ',');
+        if (buf2 == NULL)
+                return 0;
+        len = buf2 - buf1;
+        buf2 = xmalloc(len + 1);
+        strncpy(buf2, buf1, len);
+        buf2[len] = '\0';
+        int res = atoi(buf2);
+        free(buf2);
+        return res;
+}
+
+static char *replace_tabs(char *line)
+{
+        char *prev_buf = line;
+        char *cur_buf;
+        int linelen = strlen(line);
+        int n_tabs = 0;
+        int i;
+        char *result;
+        char *spaces = "        ";
+
+        if (linelen == 0) {
+                result = xmalloc(1);
+                result[0] = '\0';
+                return result;
+        }
+
+        for (i = 0; i < linelen; i++)
+                if (line[i] == '\t')
+                        n_tabs += 1;
+        result = xmalloc(linelen + n_tabs * 8 + 1);
+        result[0] = '\0';
+
+        while (1) {
+                cur_buf = strchr(prev_buf, '\t');
+                if (!cur_buf) {
+                        strcat(result, prev_buf);
+                        break;
+                } else {
+                        strcat(result, " ");
+                        strncat(result, spaces, 8 - (strlen(result) % 8));
+                        strncat(result, prev_buf, cur_buf - prev_buf);
+                }
+                prev_buf = cur_buf + 1;
+        }
+        return result;
+}
+
+static int calc_deferred_lines(struct deferred_lines *start)
+{
+        struct deferred_lines *item = start;
+        int result = 0;
+        while (item) {
+                result += 1;
+                item = item->next;
+        }
+        return result;
+}
+
+static void deferred_old_add(char *line, int line_no)
+{
+        struct deferred_lines *item = xmalloc(sizeof(struct deferred_lines));
+        item->line = xstrdup(line);
+        item->line_no = line_no;
+        item->next = NULL;
+        if (deferred_old) {
+                deferred_old_last->next = item;
+                deferred_old_last = item;
+        } else {
+                deferred_old = deferred_old_last = item;
+        }
+}
+
+static void deferred_new_add(char *line, int line_no)
+{
+        struct deferred_lines *item = xmalloc(sizeof(struct deferred_lines));
+        item->line = xstrdup(line);
+        item->line_no = line_no;
+        item->next = NULL;
+        if (deferred_new) {
+                deferred_new_last->next = item;
+                deferred_new_last = item;
+        } else {
+                deferred_new = deferred_new_last = item;
+        }
+}
+
+static void print_part_with_lcs(char *class, char *line, char *lcs)
+{
+        int line_len = strlen(line);
+        int i, j;
+        char c[2] = " ";
+        int same = 1;
+
+        j = 0;
+        for (i = 0; i < line_len; i++) {
+                c[0] = line[i];
+                if (same) {
+                        if (line[i] == lcs[j])
+                                j += 1;
+                        else {
+                                same = 0;
+                                htmlf("<span class='%s'>", class);
+                        }
+                } else if (line[i] == lcs[j]) {
+                        same = 1;
+                        htmlf("</span>");
+                        j += 1;
+                }
+                html_txt(c);
+        }
+}
+
+static void print_ssdiff_line(char *class,
+                              int old_line_no,
+                              char *old_line,
+                              int new_line_no,
+                              char *new_line, int individual_chars)
+{
+        char *lcs = NULL;
+        if (old_line)
+                old_line = replace_tabs(old_line + 1);
+        if (new_line)
+                new_line = replace_tabs(new_line + 1);
+        if (individual_chars && old_line && new_line)
+                lcs = longest_common_subsequence(old_line, new_line);
+        html("<tr>");
+        if (old_line_no > 0)
+                htmlf("<td class='lineno'>%d</td><td class='%s'>",
+                      old_line_no, class);
+        else if (old_line)
+                htmlf("<td class='lineno'></td><td class='%s'>", class);
+        else
+                htmlf("<td class='lineno'></td><td class='%s_dark'>", class);
+        if (old_line) {
+                if (lcs)
+                        print_part_with_lcs("del", old_line, lcs);
+                else
+                        html_txt(old_line);
+        }
+
+        html("</td>");
+        if (new_line_no > 0)
+                htmlf("<td class='lineno'>%d</td><td class='%s'>",
+                      new_line_no, class);
+        else if (new_line)
+                htmlf("<td class='lineno'></td><td class='%s'>", class);
+        else
+                htmlf("<td class='lineno'></td><td class='%s_dark'>", class);
+        if (new_line) {
+                if (lcs)
+                        print_part_with_lcs("add", new_line, lcs);
+                else
+                        html_txt(new_line);
+        }
+
+        html("</td></tr>");
+        if (lcs)
+                free(lcs);
+        if (new_line)
+                free(new_line);
+        if (old_line)
+                free(old_line);
+}
+
+static void print_deferred_old_lines()
+{
+        struct deferred_lines *iter_old, *tmp;
+        iter_old = deferred_old;
+        while (iter_old) {
+                print_ssdiff_line("del", iter_old->line_no,
+                                  iter_old->line, -1, NULL, 0);
+                tmp = iter_old->next;
+                free(iter_old);
+                iter_old = tmp;
+        }
+}
+
+static void print_deferred_new_lines()
+{
+        struct deferred_lines *iter_new, *tmp;
+        iter_new = deferred_new;
+        while (iter_new) {
+                print_ssdiff_line("add", -1, NULL,
+                                  iter_new->line_no, iter_new->line, 0);
+                tmp = iter_new->next;
+                free(iter_new);
+                iter_new = tmp;
+        }
+}
+
+static void print_deferred_changed_lines()
+{
+        struct deferred_lines *iter_old, *iter_new, *tmp;
+        int n_old_lines = calc_deferred_lines(deferred_old);
+        int n_new_lines = calc_deferred_lines(deferred_new);
+        int individual_chars = (n_old_lines == n_new_lines ? 1 : 0);
+
+        iter_old = deferred_old;
+        iter_new = deferred_new;
+        while (iter_old || iter_new) {
+                if (iter_old && iter_new)
+                        print_ssdiff_line("changed", iter_old->line_no,
+                                          iter_old->line,
+                                          iter_new->line_no, iter_new->line,
+                                          individual_chars);
+                else if (iter_old)
+                        print_ssdiff_line("changed", iter_old->line_no,
+                                          iter_old->line, -1, NULL, 0);
+                else if (iter_new)
+                        print_ssdiff_line("changed", -1, NULL,
+                                          iter_new->line_no, iter_new->line, 0);
+                if (iter_old) {
+                        tmp = iter_old->next;
+                        free(iter_old);
+                        iter_old = tmp;
+                }
+
+                if (iter_new) {
+                        tmp = iter_new->next;
+                        free(iter_new);
+                        iter_new = tmp;
+                }
+        }
+}
+
+void cgit_ssdiff_print_deferred_lines()
+{
+        if (!deferred_old && !deferred_new)
+                return;
+        if (deferred_old && !deferred_new)
+                print_deferred_old_lines();
+        else if (!deferred_old && deferred_new)
+                print_deferred_new_lines();
+        else
+                print_deferred_changed_lines();
+        deferred_old = deferred_old_last = NULL;
+        deferred_new = deferred_new_last = NULL;
+}
+
+/*
+ * print a single line returned from xdiff
+ */
+void cgit_ssdiff_line_cb(char *line, int len)
+{
+        char c = line[len - 1];
+        line[len - 1] = '\0';
+        if (line[0] == '@') {
+                current_old_line = line_from_hunk(line, '-');
+                current_new_line = line_from_hunk(line, '+');
+        }
+
+        if (line[0] == ' ') {
+                if (deferred_old || deferred_new)
+                        cgit_ssdiff_print_deferred_lines();
+                print_ssdiff_line("ctx", current_old_line, line,
+                                  current_new_line, line, 0);
+                current_old_line += 1;
+                current_new_line += 1;
+        } else if (line[0] == '+') {
+                deferred_new_add(line, current_new_line);
+                current_new_line += 1;
+        } else if (line[0] == '-') {
+                deferred_old_add(line, current_old_line);
+                current_old_line += 1;
+        } else if (line[0] == '@') {
+                html("<tr><td colspan='4' class='hunk'>");
+                html_txt(line);
+                html("</td></tr>");
+        } else {
+                html("<tr><td colspan='4' class='ctx'>");
+                html_txt(line);
+                html("</td></tr>");
+        }
+        line[len - 1] = c;
+}
+
+void cgit_ssdiff_header_begin()
+{
+        current_old_line = -1;
+        current_new_line = -1;
+        html("<tr><td class='space' colspan='4'><div></div></td></tr>");
+        html("<tr><td class='head' colspan='4'>");
+}
+
+void cgit_ssdiff_header_end()
+{
+        html("</td><tr>");
+}
+
+void cgit_ssdiff_footer()
+{
+        if (deferred_old || deferred_new)
+                cgit_ssdiff_print_deferred_lines();
+        html("<tr><td class='foot' colspan='4'></td></tr>");
+}
diff --git a/ui-ssdiff.h b/ui-ssdiff.h
new file mode 100644
index 0000000..64b4b12
--- /dev/null
+++ b/ui-ssdiff.h
@@ -0,0 +1,13 @@
+#ifndef UI_SSDIFF_H
+#define UI_SSDIFF_H
+
+extern void cgit_ssdiff_print_deferred_lines();
+
+extern void cgit_ssdiff_line_cb(char *line, int len);
+
+extern void cgit_ssdiff_header_begin();
+extern void cgit_ssdiff_header_end();
+
+extern void cgit_ssdiff_footer();
+
+#endif /* UI_SSDIFF_H */