Installed Bill Jolitz's flock() code

[unix-history] / usr / src / usr.bin / ex / ex_io.c

diff --git a/usr/src/usr.bin/ex/ex_io.c b/usr/src/usr.bin/ex/ex_io.c
index bf9b889..e564ebb 100644 (file)
--- a/usr/src/usr.bin/ex/ex_io.c
+++ b/usr/src/usr.bin/ex/ex_io.c
@@ -13,6 +13,9 @@ static char *sccsid = "@(#)ex_io.c    7.15 (Berkeley) %G%";
 #include "ex_temp.h"
 #include "ex_tty.h"
 #include "ex_vis.h"
 #include "ex_temp.h"
 #include "ex_tty.h"
 #include "ex_vis.h"

+#ifdef FLOCKFILE
+#include <sys/file.h>
+#endif FLOCKFILE

 
 /*
  * File input/output, source, preserve and recover
 
 /*
  * File input/output, source, preserve and recover


@@ -36,6 +39,17 @@ int  cntln;
 long   cntnull;                /* Count of nulls " */
 long   cntodd;                 /* Count of non-ascii characters " */
 
 long   cntnull;                /* Count of nulls " */
 long   cntodd;                 /* Count of non-ascii characters " */
 

+#ifdef FLOCKFILE
+/*
+ * The alternate, saved and current file are locked the extent of the
+ * time that they are active. If the saved file is exchanged
+ * with the alternate file, the file descriptors are exchanged
+ * and the lock is not released.
+ */
+int    io_savedfile, io_altfile, io_curr ;
+int    lock_savedfile, lock_altfile, lock_curr ;
+#endif FLOCKFILE
+

 /*
  * Parse file name for command encoded by comm.
  * If comm is E then command is doomed and we are
 /*
  * Parse file name for command encoded by comm.
  * If comm is E then command is doomed and we are


@@ -46,12 +60,22 @@ filename(comm)
 {
        register int c = comm, d;
        register int i;
 {
        register int c = comm, d;
        register int i;

+#ifdef FLOCKFILE
+       int lock ;
+
+       lock = 0 ;
+#endif FLOCKFILE

 
        d = ex_getchar();
        if (endcmd(d)) {
                if (savedfile[0] == 0 && comm != 'f')
                        error("No file|No current filename");
                CP(file, savedfile);
 
        d = ex_getchar();
        if (endcmd(d)) {
                if (savedfile[0] == 0 && comm != 'f')
                        error("No file|No current filename");
                CP(file, savedfile);

+#ifdef FLOCKFILE
+               if (io_curr && io_curr != io_savedfile) close(io_curr) ;
+               lock = lock_curr = lock_savedfile ;
+               io_curr = io_savedfile ;
+#endif FLOCKFILE

                wasalt = (isalt > 0) ? isalt-1 : 0;
                isalt = 0;
                oldadot = altdot;
                wasalt = (isalt > 0) ? isalt-1 : 0;
                isalt = 0;
                oldadot = altdot;


@@ -77,17 +101,41 @@ filename(comm)
 
                case 'e':
                        if (savedfile[0]) {
 
                case 'e':
                        if (savedfile[0]) {

+#ifdef FLOCKFILE
+                               if (strcmp(file,savedfile) == 0) break ;
+#endif FLOCKFILE

                                altdot = lineDOT();
                                CP(altfile, savedfile);
                                altdot = lineDOT();
                                CP(altfile, savedfile);

+#ifdef FLOCKFILE
+                               if (io_altfile) close (io_altfile) ;
+                               io_altfile = io_savedfile ;
+                               lock_altfile = lock_savedfile ;
+                               io_savedfile = 0 ;
+#endif FLOCKFILE

                        }
                        CP(savedfile, file);
                        }
                        CP(savedfile, file);

+#ifdef FLOCKFILE
+                       io_savedfile = io_curr ;
+                       lock_savedfile = lock_curr ;
+                       io_curr = 0 ;           lock = lock_curr = 0 ;
+#endif FLOCKFILE

                        break;
 
                default:
                        if (file[0]) {
                        break;
 
                default:
                        if (file[0]) {

+#ifdef FLOCKFILE
+                               if (wasalt) break ;
+#endif

                                if (c != 'E')
                                        altdot = lineDOT();
                                CP(altfile, file);
                                if (c != 'E')
                                        altdot = lineDOT();
                                CP(altfile, file);

+#ifdef FLOCKFILE
+                               if (io_altfile
+                               && io_altfile != io_curr) close (io_altfile) ;
+                               io_altfile = io_curr ;
+                               lock_altfile = lock_curr ;
+                               io_curr = 0 ;           lock = lock_curr = 0 ;
+#endif FLOCKFILE

                        }
                        break;
                }
                        }
                        break;
                }


@@ -103,6 +151,12 @@ filename(comm)
                                ex_printf(" [Not edited]");
                        if (tchng)
                                ex_printf(" [Modified]");
                                ex_printf(" [Not edited]");
                        if (tchng)
                                ex_printf(" [Modified]");

+#ifdef FLOCKFILE
+                       if (lock == LOCK_SH)
+                               ex_printf(" [Shared lock]") ;
+                       else if (lock == LOCK_EX)
+                               ex_printf(" [Exclusive lock]") ;
+#endif FLOCKFILE

                }
                flush();
        } else
                }
                flush();
        } else


@@ -318,6 +372,9 @@ rop(c)
        short magic;
        static int ovro;        /* old value(READONLY) */
        static int denied;      /* 1 if READONLY was set due to file permissions */
        short magic;
        static int ovro;        /* old value(READONLY) */
        static int denied;      /* 1 if READONLY was set due to file permissions */

+#ifdef FLOCKFILE
+       int *lp, *iop ;
+#endif FLOCKFILE

 
        io = open(file, 0);
        if (io < 0) {
 
        io = open(file, 0);
        if (io < 0) {


@@ -410,6 +467,53 @@ rop(c)
                ex_printf(" [Read only]");
                flush();
        }
                ex_printf(" [Read only]");
                flush();
        }

+#ifdef FLOCKFILE
+       /*
+        * Attempt to lock the file. We use an sharable lock if reading
+        * the file, and an exclusive lock if editting a file.
+        * The lock will be released when the file is no longer being
+        * referenced. At any time, the editor can have as many as
+        * three files locked, and with different lock statuses.
+        */
+       /*
+        * if this is either the saved or alternate file or current file,
+        * point to the appropriate descriptor and file lock status.
+        */
+       if (strcmp (file,savedfile) == 0) {
+               if (!io_savedfile) io_savedfile = dup(io) ;
+               lp = &lock_savedfile ;  iop = &io_savedfile ;
+       } else if (strcmp (file,altfile) == 0) {
+               if (!io_altfile) io_altfile = dup(io) ;
+               lp = &lock_altfile ;    iop = &io_altfile ;
+       } else {
+               /* throw away current lock, accquire new current lock */
+               if (io_curr) close (io_curr) ;
+               io_curr = dup(io) ;
+               lp = &lock_curr ;       iop = &io_curr ;
+               lock_curr = 0 ;
+       }
+       if (c == 'r' || value(READONLY) || *lp == 0) {
+               /* if we have a lock already, don't bother */
+               if (!*lp) {
+                       /* try for a shared lock */
+                       if (flock(*iop, LOCK_SH|LOCK_NB) < 0
+                       && errno == EWOULDBLOCK) {
+                               ex_printf (
+                       " [FILE BEING MODIFIED BY ANOTHER PROCESS]") ;
+                               flush();
+                               goto fail_lock ;
+                       } else *lp = LOCK_SH ;
+               }
+       }
+       if ( c != 'r'  && !value(READONLY) && *lp != LOCK_EX) {
+               /* if we are editting the file, upgrade to an exclusive lock. */
+               if (flock(*iop, LOCK_EX|LOCK_NB) < 0 && errno == EWOULDBLOCK) {
+                       ex_printf (" [File open by another process]") ;
+                       flush();
+               } else *lp = LOCK_EX ;
+       }
+fail_lock:
+#endif FLOCKFILE

        if (c == 'r')
                setdot();
        else
        if (c == 'r')
                setdot();
        else


@@ -518,6 +622,9 @@ bool dofname;       /* if 1 call filename, else use savedfile */
        register int c, exclam, nonexist;
        line *saddr1, *saddr2;
        struct stat stbuf;
        register int c, exclam, nonexist;
        line *saddr1, *saddr2;
        struct stat stbuf;

+#ifdef FLOCKFILE
+       int *lp, *iop ;
+#endif FLOCKFILE

 
        c = 0;
        exclam = 0;
 
        c = 0;
        exclam = 0;


@@ -545,6 +652,23 @@ bool dofname;      /* if 1 call filename, else use savedfile */
                lprintf("\"%s\"", file);
        }
        nonexist = stat(file, &stbuf);
                lprintf("\"%s\"", file);
        }
        nonexist = stat(file, &stbuf);

+#ifdef FLOCKFILE
+       /*
+        * if this is either the saved or alternate file or current file,
+        * point to the appropriate descriptor and file lock status.
+        */
+       if (strcmp (file,savedfile) == 0) {
+               lp = &lock_savedfile ;  iop = &io_savedfile ;
+       } else if (strcmp (file,altfile) == 0) {
+               lp = &lock_altfile ;    iop = &io_altfile ;
+       } else {
+               lp = &lock_curr ;       iop = &io_curr ;
+       }
+       if (!*iop && !nonexist){
+               *lp = 0 ;
+               if ((*iop = open(file, 1)) < 0) *iop = 0 ;
+       }
+#endif FLOCKFILE

        switch (c) {
 
        case 0:
        switch (c) {
 
        case 0:


@@ -582,6 +706,17 @@ cre:
 /*
                synctmp();
 */
 /*
                synctmp();
 */

+#ifdef FLOCKFILE
+       if (*iop && !*lp != LOCK_EX && !exclam) {
+               /*
+                * upgrade to a exclusive lock. if can't get, someone else 
+                * has the exclusive lock. bitch to the user.
+                */
+               if (flock(*iop, LOCK_EX|LOCK_NB) < 0 && errno == EWOULDBLOCK)
+       error (" File being modified by another process - use \"w!\" to write");
+                else *lp = LOCK_EX ;
+       }
+#endif FLOCKFILE

 #ifdef V6
                io = creat(file, 0644);
 #else
 #ifdef V6
                io = creat(file, 0644);
 #else


@@ -595,6 +730,10 @@ cre:
                                ex_printf(" [New file]");
                        else if (value(WRITEANY) && edfile() != EDF)
                                ex_printf(" [Existing file]");
                                ex_printf(" [New file]");
                        else if (value(WRITEANY) && edfile() != EDF)
                                ex_printf(" [Existing file]");

+#ifdef FLOCKFILE
+               if (!*iop)
+                       *iop = dup(io) ;
+#endif FLOCKFILE

                break;
 
        case 2:
                break;
 
        case 2:


@@ -605,8 +744,27 @@ cre:
                        syserror();
                }
                lseek(io, 0l, 2);
                        syserror();
                }
                lseek(io, 0l, 2);

+#ifdef FLOCKFILE
+               if (!*iop) *iop = dup(io) ;
+               if (*lp != LOCK_EX && !exclam) {
+                       /*
+                        * upgrade to a exclusive lock. if can't get,
+                        * someone else has the exclusive lock.
+                        * bitch to the user.
+                        */
+                       if (flock(*iop, LOCK_SH|LOCK_NB) < 0
+                       && errno == EWOULDBLOCK)
+                               error (
+" File being modified by another process - use \"w!>>\" to write");
+                       else *lp = LOCK_EX ;
+               }
+#endif FLOCKFILE

                break;
        }
                break;
        }

+#ifdef FLOCKFILE
+       if (flock(*iop, LOCK_EX|LOCK_NB) >= 0)
+               *lp = LOCK_EX ;
+#endif FLOCKFILE

        putfile(0);
 #ifndef        vms
        (void) fsync(io);
        putfile(0);
 #ifndef        vms
        (void) fsync(io);