Add mkntemp, atomic_symlink4

Signed-off-by: Laurent Bercot <ska@appnovation.com>

7 files changed, 89 insertions, 35 deletions

diff --git a/doc/libunixonacid/unix-transactional.html b/doc/libunixonacid/unix-transactional.html
index 9a36173..b429001 100644
--- a/doc/libunixonacid/unix-transactional.html
+++ b/doc/libunixonacid/unix-transactional.html
@@ -128,5 +128,22 @@ The difference between these two functions is the same as that between
 <tt>rm_rf</tt> and <tt>rm_rf_tmp</tt> in <tt>djbunix</tt>.
 </p>
 
+<h3> Atomic symbolic link creation <h3>
+
+<p>
+<code> int atomic_symlink4 (char const *target, char const *name, char *buf, size_t len) </code>
+Atomically makes a symlink named <em>name</em> pointing to <em>target</em>. If
+<em>name</em> designated an existing file, it is unlinked. Does not work if
+<em>name</em> is an existing directory (but <em>will</em> work if it is a
+symlink to a directory!) Returns 1 on success, and 0 (and sets errno) on
+error. <br>
+In addition, if <em>buf</em> is not NULL, and points
+to a buffer of nonzero length <em>len</em>, then if <em>name</em> exists prior to the
+call, it must be a symbolic link, and its target be shorter than <em>len</em> bytes.
+If these conditions are fulfilled, the operation succeeds, and <em>buf</em> then
+contains the previous target of <em>name</em>, with a terminating NULL. If they are not,
+the function fails with 0 (errno is ENAMETOOLONG if the buffer is too small).
+</p>
+
 </body>
 </html>
diff --git a/package/deps.mak b/package/deps.mak
index f6481ae..b4fe193 100644
--- a/package/deps.mak
+++ b/package/deps.mak
@@ -54,7 +54,7 @@ src/include/skalibs/tai.h: src/include/skalibs/gccattributes.h src/include/skali
 src/include/skalibs/textclient.h: src/include/skalibs/allreadwrite.h src/include/skalibs/tai.h src/include/skalibs/textmessage.h
 src/include/skalibs/textmessage.h: src/include/skalibs/allreadwrite.h src/include/skalibs/bufalloc.h src/include/skalibs/buffer.h src/include/skalibs/gccattributes.h src/include/skalibs/stralloc.h src/include/skalibs/tai.h
 src/include/skalibs/unix-timed.h: src/include/skalibs/bufalloc.h src/include/skalibs/buffer.h src/include/skalibs/functypes.h src/include/skalibs/stralloc.h src/include/skalibs/tai.h
-src/include/skalibs/unix-transactional.h: src/include/skalibs/direntry.h src/include/skalibs/stralloc.h
+src/include/skalibs/unix-transactional.h: src/include/skalibs/direntry.h src/include/skalibs/gccattributes.h src/include/skalibs/stralloc.h
 src/include/skalibs/unixconnection.h: src/include/skalibs/unixmessage.h
 src/include/skalibs/unixmessage.h: src/include/skalibs/buffer.h src/include/skalibs/cbuffer.h src/include/skalibs/gccattributes.h src/include/skalibs/genalloc.h src/include/skalibs/stralloc.h src/include/skalibs/tai.h
 src/include/skalibs/unixonacid.h: src/include/skalibs/ancil.h src/include/skalibs/kolbak.h src/include/skalibs/skaclient.h src/include/skalibs/textclient.h src/include/skalibs/textmessage.h src/include/skalibs/unix-timed.h src/include/skalibs/unix-transactional.h src/include/skalibs/unixconnection.h src/include/skalibs/unixmessage.h
@@ -185,6 +185,7 @@ src/libposixplz/mkfiletemp.o src/libposixplz/mkfiletemp.lo: src/libposixplz/mkfi
 src/libposixplz/mkhtemp.o src/libposixplz/mkhtemp.lo: src/libposixplz/mkhtemp.c src/include/skalibs/posixplz.h
 src/libposixplz/mklinktemp.o src/libposixplz/mklinktemp.lo: src/libposixplz/mklinktemp.c src/include/skalibs/djbunix.h src/libposixplz/posixplz-internal.h src/include/skalibs/posixplz.h
 src/libposixplz/mkltemp.o src/libposixplz/mkltemp.lo: src/libposixplz/mkltemp.c src/include/skalibs/posixplz.h
+src/libposixplz/mkntemp.o src/libposixplz/mkntemp.lo: src/libposixplz/mkntemp.c src/include/skalibs/posixplz.h
 src/libposixplz/mkptemp.o src/libposixplz/mkptemp.lo: src/libposixplz/mkptemp.c src/include/skalibs/posixplz.h
 src/libposixplz/mkptemp2.o src/libposixplz/mkptemp2.lo: src/libposixplz/mkptemp2.c src/include/skalibs/posixplz.h
 src/libposixplz/mkptemp3.o src/libposixplz/mkptemp3.lo: src/libposixplz/mkptemp3.c src/include/skalibs/djbunix.h src/include/skalibs/fcntl.h src/include/skalibs/posixplz.h
@@ -745,7 +746,8 @@ src/libunixonacid/ancil_recv_fd.o src/libunixonacid/ancil_recv_fd.lo: src/libuni
 src/libunixonacid/ancil_send_fd.o src/libunixonacid/ancil_send_fd.lo: src/libunixonacid/ancil_send_fd.c src/include/skalibs/ancil.h src/include/skalibs/nonposix.h src/include/skalibs/posixishard.h
 src/libunixonacid/atomic_rm_rf.o src/libunixonacid/atomic_rm_rf.lo: src/libunixonacid/atomic_rm_rf.c src/include/skalibs/skamisc.h src/include/skalibs/unix-transactional.h
 src/libunixonacid/atomic_rm_rf_tmp.o src/libunixonacid/atomic_rm_rf_tmp.lo: src/libunixonacid/atomic_rm_rf_tmp.c src/include/skalibs/djbunix.h src/include/skalibs/random.h src/include/skalibs/stralloc.h src/include/skalibs/unix-transactional.h
-src/libunixonacid/atomic_symlink.o src/libunixonacid/atomic_symlink.lo: src/libunixonacid/atomic_symlink.c src/include/skalibs/posixplz.h src/include/skalibs/unix-transactional.h
+src/libunixonacid/atomic_symlink.o src/libunixonacid/atomic_symlink.lo: src/libunixonacid/atomic_symlink.c src/include/skalibs/unix-transactional.h
+src/libunixonacid/atomic_symlink4.o src/libunixonacid/atomic_symlink4.lo: src/libunixonacid/atomic_symlink4.c src/include/skalibs/posixplz.h src/include/skalibs/unix-transactional.h
 src/libunixonacid/bufalloc_timed_flush.o src/libunixonacid/bufalloc_timed_flush.lo: src/libunixonacid/bufalloc_timed_flush.c src/include/skalibs/bufalloc.h src/include/skalibs/functypes.h src/include/skalibs/unix-timed.h
 src/libunixonacid/buffer_timed_fill.o src/libunixonacid/buffer_timed_fill.lo: src/libunixonacid/buffer_timed_fill.c src/include/skalibs/allreadwrite.h src/include/skalibs/buffer.h src/include/skalibs/functypes.h src/include/skalibs/unix-timed.h
 src/libunixonacid/buffer_timed_flush.o src/libunixonacid/buffer_timed_flush.lo: src/libunixonacid/buffer_timed_flush.c src/include/skalibs/buffer.h src/include/skalibs/functypes.h src/include/skalibs/unix-timed.h
diff --git a/src/include/skalibs/posixplz.h b/src/include/skalibs/posixplz.h
index 558ccae..3c6c520 100644
--- a/src/include/skalibs/posixplz.h
+++ b/src/include/skalibs/posixplz.h
@@ -45,6 +45,7 @@ extern int mkdirp (char const *, mode_t) ;
 extern int mkdirp2 (char *, mode_t) ;
 extern int mkfiletemp (char *, create_func_ref, mode_t, void *) ;
 extern int mklinktemp (char const *, char *, link_func_ref) ;
+extern int mkntemp (char *) ;
 extern int mkptemp (char *) ;
 extern int mkptemp2 (char *, unsigned int) ;
 extern int mkptemp3 (char *, mode_t, unsigned int) ;
diff --git a/src/include/skalibs/unix-transactional.h b/src/include/skalibs/unix-transactional.h
index 73a8d7f..9b884f9 100644
--- a/src/include/skalibs/unix-transactional.h
+++ b/src/include/skalibs/unix-transactional.h
@@ -7,6 +7,7 @@
 #include <sys/stat.h>
 #include <sys/uio.h>
 
+#include <skalibs/gccattributes.h>
 #include <skalibs/direntry.h>
 #include <skalibs/stralloc.h>
 
@@ -47,6 +48,7 @@ extern size_t openwritevnclose_at (int, char const *, struct iovec const *, unsi
 
 extern int atomic_rm_rf (char const *) ;
 extern int atomic_rm_rf_tmp (char const *, stralloc *) ;
-extern int atomic_symlink (char const *, char const *, char const *) ;
+extern int atomic_symlink (char const *, char const *, char const *) gccattr_deprecated ;
+extern int atomic_symlink4 (char const *, char const *, char *, size_t) ;
 
 #endif
diff --git a/src/libposixplz/mkntemp.c b/src/libposixplz/mkntemp.c
new file mode 100644
index 0000000..42d542b
--- /dev/null
+++ b/src/libposixplz/mkntemp.c
@@ -0,0 +1,19 @@
+/* ISC license. */
+
+#include <unistd.h>
+#include <errno.h>
+
+#include <skalibs/posixplz.h>
+
+static int f (char const *fn, mode_t mode, void *data)
+{
+  (void)mode ;
+  (void)data ;
+  return access(fn, F_OK) == 0 ? (errno = EEXIST, -1) :
+    errno == ENOENT ? (errno = 0, 0) : -1 ;
+}
+
+int mkntemp (char *s)
+{
+  return mkfiletemp(s, &f, 0, 0) ;
+}
diff --git a/src/libunixonacid/atomic_symlink.c b/src/libunixonacid/atomic_symlink.c
index a4c7ecf..13e82e6 100644
--- a/src/libunixonacid/atomic_symlink.c
+++ b/src/libunixonacid/atomic_symlink.c
@@ -1,39 +1,9 @@
 /* ISC license. */
 
-#include <string.h>
-#include <unistd.h>
-#include <errno.h>
-#include <stdio.h>
-
-#include <skalibs/posixplz.h>
 #include <skalibs/unix-transactional.h>
 
 int atomic_symlink (char const *target, char const *name, char const *suffix)
 {
-  {
-    int e = errno ;
-    if (symlink(target, name) == 0) return 1 ;
-    if (errno != EEXIST) return 0 ;
-    errno = e ;
-  }
-  {
-    size_t namelen = strlen(name) ;
-    size_t suffixlen = suffix ? strlen(suffix) + 1 : 0 ;
-    char tmp[namelen + suffixlen + 8] ;
-    memcpy(tmp, name, namelen) ;
-    if (suffix)
-    {
-      tmp[namelen] = ':' ;
-      memcpy(tmp + namelen + 1, suffix, suffixlen - 1) ;
-    }
-    memcpy(tmp + namelen + suffixlen, ":XXXXXX", 7) ;
-    tmp[namelen + suffixlen + 7] = 0 ;
-    if (mkltemp(target, tmp) == -1) return 0 ;
-    if (rename(tmp, name) < 0)
-    {
-      unlink_void(tmp) ;
-      return 0 ;
-    }
-  }
-  return 1 ;
+  (void)suffix ;
+  return atomic_symlink4(target, name, 0, 0) ;
 }
diff --git a/src/libunixonacid/atomic_symlink4.c b/src/libunixonacid/atomic_symlink4.c
new file mode 100644
index 0000000..7b18a5e
--- /dev/null
+++ b/src/libunixonacid/atomic_symlink4.c
@@ -0,0 +1,43 @@
+/* ISC license. */
+
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdio.h>
+
+#include <skalibs/posixplz.h>
+#include <skalibs/unix-transactional.h>
+
+int atomic_symlink4 (char const *target, char const *name, char *oldbuf, size_t oldlen)
+{
+  {
+    int e = errno ;
+    if (symlink(target, name) == 0)
+    {
+      if (oldbuf && oldlen) *oldbuf = 0 ;
+      return 1 ;
+    }
+    if (errno != EEXIST) return 0 ;
+    errno = e ;
+  }
+  {
+    size_t namelen = strlen(name) ;
+    char tmp[namelen + 32] ;
+    if (oldbuf && oldlen)
+    {
+      ssize_t r = readlink(name, oldbuf, oldlen) ;
+      if (r == -1) return 0 ;
+      if (r >= oldlen) return (errno = ENAMETOOLONG, 0) ;
+      oldbuf[r] = 0 ;
+    }
+    memcpy(tmp, name, namelen) ;
+    memcpy(tmp + namelen, ":skalibs-atomic_symlink4:XXXXXX", 32) ;
+    if (mkltemp(target, tmp) == -1) return 0 ;
+    if (rename(tmp, name) == -1)
+    {
+      unlink_void(tmp) ;
+      return 0 ;
+    }
+  }
+  return 1 ;
+}