vi: allow line addresses to have an offset

Line addresses in colon commands can be defined using an expression
that includes '+' or '-' operators.  The implementation follows
traditional vi:

- The first term in the expression defines an address.  It can be
  an absolute line number, '.', '$', a search or a marker.

- The second and subsequent terms must be non-negative integers.

- If the first term is missing '.' is assumed.  If the operator is
  missing addition is assumed.  If the final term in missing an
  offset of 1 is assumed.

Thus the following are valid addresses:

  .+1   .+   +   .1
  .-1   .-   -

The following are not valid (though they are in vim):

  .+$   .$   2+.

function                                             old     new   delta
colon                                               3701    3844    +143
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/0 up/down: 143/0)             Total: 143 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 72 insertions, 46 deletions

diff --git a/editors/vi.c b/editors/vi.c
index 0866e0fa9..6dd951421 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -2342,67 +2342,93 @@ static char *char_search(char *p, const char *pat, int dir_and_range)
 
 //----- The Colon commands -------------------------------------
 #if ENABLE_FEATURE_VI_COLON
-static char *get_one_address(char *p, int *addr)        // get colon addr, if present
+static char *get_one_address(char *p, int *result)      // get colon addr, if present
 {
-        int st;
+        int st, num, sign, addr, new_addr;
 # if ENABLE_FEATURE_VI_YANKMARK || ENABLE_FEATURE_VI_SEARCH
         char *q, c;
 # endif
         IF_FEATURE_VI_SEARCH(int dir;)
 
-        *addr = -1;                     // assume no addr
-        if (*p == '.') {        // the current line
-                p++;
-                *addr = count_lines(text, dot);
-        }
+        addr = -1;                      // assume no addr
+        sign = 0;
+        for (;;) {
+                new_addr = -1;
+                if (isblank(*p)) {
+                        p++;
+                } else if (*p == '.') { // the current line
+                        p++;
+                        new_addr = count_lines(text, dot);
+                }
 # if ENABLE_FEATURE_VI_YANKMARK
-        else if (*p == '\'') {  // is this a mark addr
-                p++;
-                c = tolower(*p);
-                p++;
-                q = NULL;
-                if (c >= 'a' && c <= 'z') {
-                        // we have a mark
-                        c = c - 'a';
-                        q = mark[(unsigned char) c];
+                else if (*p == '\'') {  // is this a mark addr
+                        p++;
+                        c = tolower(*p);
+                        p++;
+                        q = NULL;
+                        if (c >= 'a' && c <= 'z') {
+                                // we have a mark
+                                c = c - 'a';
+                                q = mark[(unsigned char) c];
+                        }
+                        if (q == NULL)  // is mark valid
+                                return NULL;
+                        new_addr = count_lines(text, q);
                 }
-                if (q == NULL)  // is mark valid
-                        return NULL;
-                *addr = count_lines(text, q);
-        }
 # endif
 # if ENABLE_FEATURE_VI_SEARCH
-        else if (*p == '/' || *p == '?') {      // a search pattern
-                c = *p;
-                q = strchrnul(p + 1, c);
-                if (p + 1 != q) {
-                        // save copy of new pattern
-                        free(last_search_pattern);
-                        last_search_pattern = xstrndup(p, q - p);
+                else if (*p == '/' || *p == '?') {      // a search pattern
+                        c = *p;
+                        q = strchrnul(p + 1, c);
+                        if (p + 1 != q) {
+                                // save copy of new pattern
+                                free(last_search_pattern);
+                                last_search_pattern = xstrndup(p, q - p);
+                        }
+                        p = q;
+                        if (*p == c)
+                                p++;
+                        if (c == '/') {
+                                q = next_line(dot);
+                                dir = (FORWARD << 1) | FULL;
+                        } else {
+                                q = begin_line(dot);
+                                dir = ((unsigned)BACK << 1) | FULL;
+                        }
+                        q = char_search(q, last_search_pattern + 1, dir);
+                        if (q == NULL)
+                                return NULL;
+                        new_addr = count_lines(text, q);
                 }
-                p = q;
-                if (*p == c)
+# endif
+                else if (*p == '$') {   // the last line in file
                         p++;
-                if (c == '/') {
-                        q = next_line(dot);
-                        dir = (FORWARD << 1) | FULL;
+                        new_addr = count_lines(text, end - 1);
+                } else if (isdigit(*p)) {
+                        sscanf(p, "%d%n", &num, &st);
+                        p += st;
+                        if (addr < 0) { // specific line number
+                                addr = num;
+                        } else {        // offset from current addr
+                                addr += sign >= 0 ? num : -num;
+                        }
+                        sign = 0;
+                } else if (*p == '-' || *p == '+') {
+                        sign = *p++ == '-' ? -1 : 1;
+                        if (addr < 0) { // default address is dot
+                                addr = count_lines(text, dot);
+                        }
                 } else {
-                        q = begin_line(dot);
-                        dir = ((unsigned)BACK << 1) | FULL;
+                        addr += sign;   // consume unused trailing sign
+                        break;
+                }
+                if (new_addr >= 0) {
+                        if (addr >= 0)  // only one new address per expression
+                                return NULL;
+                        addr = new_addr;
                 }
-                q = char_search(q, last_search_pattern + 1, dir);
-                if (q == NULL)
-                        return NULL;
-                *addr = count_lines(text, q);
-        }
-# endif
-        else if (*p == '$') {   // the last line in file
-                p++;
-                *addr = count_lines(text, end - 1);
-        } else if (isdigit(*p)) {       // specific line number
-                sscanf(p, "%d%n", addr, &st);
-                p += st;
         }
+        *result = addr;
         return p;
 }