vi: allow regular expressions in ':s' commands

BusyBox vi has never supported the use of regular expressions in
search/replace (':s') commands.  Implement this using GNU regex
when VI_REGEX_SEARCH is enabled.

The implementation:

- uses basic regular expressions, to match those used in the search
  command;

- only supports substitution of back references ('\0' - '\9') in the
  replacement string.  Any other character following a backslash is
  treated as that literal character.

VI_REGEX_SEARCH isn't enabled in the default build.  In that case:

function                                             old     new   delta
colon                                               4036    4033      -3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-3)               Total: -3 bytes

When VI_REGEX_SEARCH is enabled:

function                                             old     new   delta
colon                                               4036    4378    +342
.rodata                                           108207  108229     +22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 364/0)             Total: 364 bytes

v2: Rebase.  Code shrink.  Ensure empty replacement string is null terminated.

Signed-off-by: Andrey Dobrovolsky <andrey.dobrovolsky.odessa@gmail.com>
Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

0 files changed, 0 insertions, 0 deletions