[PATCH 10/19] libctf: write CTF files to memory, and CTF archives to fds

[Nick Alcock <nick dot alcock at oracle dot com>]

Before now, we've been able to write CTF files to gzFile descriptors or
fds, and CTF archives to named files only.

Make this a bit less irregular by allowing CTF archives to be written
to fds with the new function ctf_arc_write_fd: also allow CTF
files to be written to a new memory buffer via ctf_write_mem.

(It would be nice to complete things by adding a new function to write
CTF archives to memory, but this is too difficult to do given the short
time the linker is expected to be writing them out: we will transition
to a better format in format v4, though we will always support reading
CTF archives that are stored in .ctf sections.)

include/
	* ctf-api.h (ctf_arc_write_fd): New.
	(ctf_write_mem): Likewise.
	(ctf_gzwrite): Spacing fix.

libctf/
	* ctf-archive.c (ctf_arc_write): Split off, and reimplement in terms
	of...
	(ctf_arc_write_fd): ... this new function.
	* ctf-create.c (ctf_write_mem): New.
---
 include/ctf-api.h    |  5 ++-
 libctf/ctf-archive.c | 93 +++++++++++++++++++++++++++-----------------
 libctf/ctf-create.c  | 51 ++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 36 deletions(-)

diff --git a/include/ctf-api.h b/include/ctf-api.h
index ba3cc34cad..c122f4c13e 100644
--- a/include/ctf-api.h
+++ b/include/ctf-api.h
@@ -258,6 +258,8 @@ extern void ctf_file_close (ctf_file_t *);
 
 extern int ctf_arc_write (const char *, ctf_file_t **, size_t,
 			  const char **, size_t);
+extern int ctf_arc_write_fd (int, ctf_file_t **, size_t, const char **,
+			     size_t);
 
 extern const char *ctf_cuname (ctf_file_t *);
 extern void ctf_cuname_set (ctf_file_t *, const char *);
@@ -376,8 +378,9 @@ extern ctf_snapshot_id_t ctf_snapshot (ctf_file_t *);
 extern int ctf_rollback (ctf_file_t *, ctf_snapshot_id_t);
 extern int ctf_discard (ctf_file_t *);
 extern int ctf_write (ctf_file_t *, int);
-extern int ctf_gzwrite (ctf_file_t * fp, gzFile fd);
+extern int ctf_gzwrite (ctf_file_t *fp, gzFile fd);
 extern int ctf_compress_write (ctf_file_t * fp, int fd);
+extern unsigned char *ctf_write_mem (ctf_file_t *, size_t *, size_t threshold);
 
 extern void ctf_setdebug (int debug);
 extern int ctf_getdebug (void);
diff --git a/libctf/ctf-archive.c b/libctf/ctf-archive.c
index a13bac8cd6..6a161f94b2 100644
--- a/libctf/ctf-archive.c
+++ b/libctf/ctf-archive.c
@@ -47,17 +47,17 @@ static int arc_mmap_unmap (void *header, size_t headersz, const char **errmsg);
 /* bsearch() internal state.  */
 static __thread char *search_nametbl;
 
-/* Write out a CTF archive.  The entries in CTF_FILES are referenced by name:
-   the names are passed in the names array, which must have CTF_FILES entries.
+/* Write out a CTF archive to the start of the file referenced by the passed-in
+   fd.  The entries in CTF_FILES are referenced by name: the names are passed in
+   the names array, which must have CTF_FILES entries.
 
    Returns 0 on success, or an errno, or an ECTF_* value.  */
 int
-ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
-	       const char **names, size_t threshold)
+ctf_arc_write_fd (int fd, ctf_file_t **ctf_files, size_t ctf_file_cnt,
+		  const char **names, size_t threshold)
 {
   const char *errmsg;
   struct ctf_archive *archdr;
-  int fd;
   size_t i;
   char dummy = 0;
   size_t headersz;
@@ -68,15 +68,9 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
   off_t nameoffs;
   struct ctf_archive_modent *modent;
 
-  ctf_dprintf ("Writing archive %s with %lu files\n", file,
+  ctf_dprintf ("Writing CTF archive with %lu files\n",
 	       (unsigned long) ctf_file_cnt);
 
-  if ((fd = open (file, O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0666)) < 0)
-    {
-      errmsg = "ctf_arc_write(): cannot create %s: %s\n";
-      goto err;
-    }
-
   /* Figure out the size of the mmap()ed header, including the
      ctf_archive_modent array.  We assume that all of this needs no
      padding: a likely assumption, given that it's all made up of
@@ -91,20 +85,20 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
   ctf_startoffs = headersz;
   if (lseek (fd, ctf_startoffs - 1, SEEK_SET) < 0)
     {
-      errmsg = "ctf_arc_write(): cannot extend file while writing %s: %s\n";
-      goto err_close;
+      errmsg = "ctf_arc_write(): cannot extend file while writing: %s\n";
+      goto err;
     }
 
   if (write (fd, &dummy, 1) < 0)
     {
-      errmsg = "ctf_arc_write(): cannot extend file while writing %s: %s\n";
-      goto err_close;
+      errmsg = "ctf_arc_write(): cannot extend file while writing: %s\n";
+      goto err;
     }
 
   if ((archdr = arc_mmap_header (fd, headersz)) == NULL)
     {
-      errmsg = "ctf_arc_write(): Cannot mmap() %s: %s\n";
-      goto err_close;
+      errmsg = "ctf_arc_write(): Cannot mmap(): %s\n";
+      goto err;
     }
 
   /* Fill in everything we can, which is everything other than the name
@@ -137,7 +131,7 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
   nametbl = malloc (namesz);
   if (nametbl == NULL)
     {
-      errmsg = "Error writing named CTF to %s: %s\n";
+      errmsg = "Error writing named CTF to archive: %s\n";
       goto err_unmap;
     }
 
@@ -154,12 +148,12 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
       if ((off < 0) && (off > -ECTF_BASE))
 	{
 	  errmsg = "ctf_arc_write(): Cannot determine file "
-	    "position while writing %s: %s";
+	    "position while writing to archive: %s";
 	  goto err_free;
 	}
       if (off < 0)
 	{
-	  errmsg = "ctf_arc_write(): Cannot write CTF file to %s: %s\n";
+	  errmsg = "ctf_arc_write(): Cannot write CTF file to archive: %s\n";
 	  errno = off * -1;
 	  goto err_free;
 	}
@@ -181,7 +175,7 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
   if ((nameoffs = lseek (fd, 0, SEEK_CUR)) < 0)
     {
       errmsg = "ctf_arc_write(): Cannot get current file position "
-	"in %s: %s\n";
+	"in archive: %s\n";
       goto err_free;
     }
   archdr->ctfa_names = htole64 (nameoffs);
@@ -191,7 +185,7 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
       ssize_t len;
       if ((len = write (fd, np, namesz)) < 0)
 	{
-	  errmsg = "ctf_arc_write(): Cannot write name table in %s: %s\n";
+	  errmsg = "ctf_arc_write(): Cannot write name table to archive: %s\n";
 	  goto err_free;
 	}
       namesz -= len;
@@ -202,29 +196,58 @@ ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
   if (arc_mmap_writeout (fd, archdr, headersz, &errmsg) < 0)
     goto err_unmap;
   if (arc_mmap_unmap (archdr, headersz, &errmsg) < 0)
-    goto err_unlink;
-  if (close (fd) < 0)
-    {
-      errmsg = "ctf_arc_write(): Cannot close after writing to %s: %s\n";
-      goto err_unlink;
-    }
-
+    goto err;
   return 0;
 
 err_free:
   free (nametbl);
 err_unmap:
   arc_mmap_unmap (archdr, headersz, NULL);
-err_close:
-  close (fd);
-err_unlink:
-  unlink (file);
 err:
-  ctf_dprintf (errmsg, file, errno < ECTF_BASE ? strerror (errno) :
+  ctf_dprintf (errmsg, errno < ECTF_BASE ? strerror (errno) :
 	       ctf_errmsg (errno));
   return errno;
 }
 
+/* Write out a CTF archive.  The entries in CTF_FILES are referenced by name:
+   the names are passed in the names array, which must have CTF_FILES entries.
+
+   If the filename is NULL, create a temporary file and return a pointer to it.
+
+   Returns 0 on success, or an errno, or an ECTF_* value.  */
+int
+ctf_arc_write (const char *file, ctf_file_t ** ctf_files, size_t ctf_file_cnt,
+	       const char **names, size_t threshold)
+{
+  int err;
+  int fd;
+
+  if ((fd = open (file, O_RDWR | O_CREAT | O_TRUNC | O_CLOEXEC, 0666)) < 0)
+    {
+      ctf_dprintf ("ctf_arc_write(): cannot create %s: %s\n", file,
+		   strerror (errno));
+      return errno;
+    }
+
+  err = ctf_arc_write_fd (fd, ctf_files, ctf_file_cnt, names, threshold);
+  if (err)
+    goto err;
+
+  if ((err = close (fd)) < 0)
+    {
+      ctf_dprintf ("ctf_arc_write(): Cannot close after writing to archive: "
+		   "%s\n", strerror (errno));
+      goto err;
+    }
+
+ err:
+  close (fd);
+  if (err < 0)
+    unlink (file);
+
+  return err;
+}
+
 /* Write one CTF file out.  Return the file position of the written file (or
    rather, of the file-size uint64_t that precedes it): negative return is a
    negative errno or ctf_errno value.  On error, the file position may no longer
diff --git a/libctf/ctf-create.c b/libctf/ctf-create.c
index 4ea288e451..5b6cc8b597 100644
--- a/libctf/ctf-create.c
+++ b/libctf/ctf-create.c
@@ -2012,6 +2012,57 @@ ret:
   return err;
 }
 
+/* Optionally compress the specified CTF data stream and return it as a new
+   dynamically-allocated string.  */
+unsigned char *
+ctf_write_mem (ctf_file_t *fp, size_t *size, size_t threshold)
+{
+  unsigned char *buf;
+  unsigned char *bp;
+  ctf_header_t *hp;
+  ssize_t header_len = sizeof (ctf_header_t);
+  ssize_t compress_len;
+  size_t max_compress_len = compressBound (fp->ctf_size);
+  int rc;
+
+  if (fp->ctf_size < threshold)
+    max_compress_len = fp->ctf_size;
+  if ((buf = malloc (max_compress_len
+		     + sizeof (struct ctf_header))) == NULL)
+    {
+      ctf_set_errno (fp, ENOMEM);
+      return NULL;
+    }
+
+  hp = (ctf_header_t *) buf;
+  memcpy (hp, fp->ctf_header, header_len);
+  bp = buf + sizeof (struct ctf_header);
+  *size = sizeof (struct ctf_header);
+
+  compress_len = max_compress_len;
+
+  if (fp->ctf_size < threshold)
+    {
+      hp->cth_flags &= ~CTF_F_COMPRESS;
+      memcpy (bp, fp->ctf_buf, fp->ctf_size);
+      *size += fp->ctf_size;
+    }
+  else
+    {
+      hp->cth_flags |= CTF_F_COMPRESS;
+      if ((rc = compress (bp, (uLongf *) &compress_len,
+			  fp->ctf_buf, fp->ctf_size)) != Z_OK)
+	{
+	  ctf_dprintf ("zlib deflate err: %s\n", zError (rc));
+	  ctf_set_errno (fp, ECTF_COMPRESS);
+	  ctf_free (buf);
+	  return NULL;
+	}
+      *size += compress_len;
+    }
+  return buf;
+}
+
 /* Write the uncompressed CTF data stream to the specified file descriptor.  */
 int
 ctf_write (ctf_file_t *fp, int fd)
-- 
2.22.0.238.g049a27acdc