guestfs_write, guestfs_write_append: Reimplement to avoid protocol limits.

Note that we keep the old daemon calls, but rename them as
"internal_write" and "internal_write_append".  This lets us implement
the new library-side calls more efficiently in the common case when
the uploaded content is smaller than the message buffer.  In most
cases the new calls won't end up using a temporary file.

TODO

@@ -568,6 +568,3 @@ the p.o.v of the API and ABI.
  - guestfs_lstatlist
  - guestfs_lxattrlist
  - guestfs_readlinklist
- - guestfs_write
- - guestfs_write_append
- - guestfs_write_file

daemon/file.c

@@ -211,7 +211,7 @@ do_write_file (const char *path, const char *content, int size)
 }
 
 int
-do_write (const char *path, const char *content, size_t size)
+do_internal_write (const char *path, const char *content, size_t size)
 {
   int fd;
 
@@ -239,7 +239,7 @@ do_write (const char *path, const char *content, size_t size)
 }
 
 int
-do_write_append (const char *path, const char *content, size_t size)
+do_internal_write_append (const char *path, const char *content, size_t size)
 {
   int fd;
 

generator/generator_actions.ml

@@ -2104,6 +2104,54 @@ Note that this function cannot correctly handle binary files
 as end of string).  For those you need to use the C<guestfs_read_file>
 function and split the buffer into lines yourself." };
 
+  { defaults with
+    name = "write";
+    style = RErr, [Pathname "path"; BufferIn "content"], [];
+    tests = [
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write"; "new file contents"];
+         ["cat"; "/write"]], "new file contents");
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write2"; "\nnew file contents\n"];
+         ["cat"; "/write2"]], "\nnew file contents\n");
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write3"; "\n\n"];
+         ["cat"; "/write3"]], "\n\n");
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write4"; ""];
+         ["cat"; "/write4"]], "");
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write5"; "\n\n\n"];
+         ["cat"; "/write5"]], "\n\n\n");
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write6"; "\n"];
+         ["cat"; "/write6"]], "\n")
+    ];
+    shortdesc = "create a new file";
+    longdesc = "\
+This call creates a file called C<path>.  The content of the
+file is the string C<content> (which can contain any 8 bit data).
+
+See also C<guestfs_write_append>." };
+
+  { defaults with
+    name = "write_append";
+    style = RErr, [Pathname "path"; BufferIn "content"], [];
+    tests = [
+      InitScratchFS, Always, TestOutput (
+        [["write"; "/write_append"; "line1\n"];
+         ["write_append"; "/write_append"; "line2\n"];
+         ["write_append"; "/write_append"; "line3a"];
+         ["write_append"; "/write_append"; "line3b\n"];
+         ["cat"; "/write_append"]], "line1\nline2\nline3aline3b\n")
+    ];
+    shortdesc = "append content to end of file";
+    longdesc = "\
+This call appends C<content> to the end of file C<path>.  If
+C<path> does not exist, then a new file is created.
+
+See also C<guestfs_write>." };
+
 ]
 
 (* daemon_functions are any functions which cause some action
@@ -7082,29 +7130,30 @@ of bytes in C<pattern>.  The pattern is truncated if necessary
 to ensure the length of the file is exactly C<len> bytes." };
 
   { defaults with
-    name = "write";
+    name = "internal_write";
     style = RErr, [Pathname "path"; BufferIn "content"], [];
     proc_nr = Some 246;
+    in_fish = false; in_docs = false;
     protocol_limit_warning = true;
     tests = [
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write"; "new file contents"];
+        [["internal_write"; "/internal_write"; "new file contents"];
-         ["cat"; "/write"]], "new file contents");
+         ["cat"; "/internal_write"]], "new file contents");
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write2"; "\nnew file contents\n"];
+        [["internal_write"; "/internal_write2"; "\nnew file contents\n"];
-         ["cat"; "/write2"]], "\nnew file contents\n");
+         ["cat"; "/internal_write2"]], "\nnew file contents\n");
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write3"; "\n\n"];
+        [["internal_write"; "/internal_write3"; "\n\n"];
-         ["cat"; "/write3"]], "\n\n");
+         ["cat"; "/internal_write3"]], "\n\n");
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write4"; ""];
+        [["internal_write"; "/internal_write4"; ""];
-         ["cat"; "/write4"]], "");
+         ["cat"; "/internal_write4"]], "");
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write5"; "\n\n\n"];
+        [["internal_write"; "/internal_write5"; "\n\n\n"];
-         ["cat"; "/write5"]], "\n\n\n");
+         ["cat"; "/internal_write5"]], "\n\n\n");
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write6"; "\n"];
+        [["internal_write"; "/internal_write6"; "\n"];
-         ["cat"; "/write6"]], "\n")
+         ["cat"; "/internal_write6"]], "\n")
     ];
     shortdesc = "create a new file";
     longdesc = "\
@@ -7943,17 +7992,18 @@ is resized to the maximum size.
 See also L<btrfs(8)>." };
 
   { defaults with
-    name = "write_append";
+    name = "internal_write_append";
     style = RErr, [Pathname "path"; BufferIn "content"], [];
     proc_nr = Some 290;
+    in_fish = false; in_docs = false;
     protocol_limit_warning = true;
     tests = [
       InitScratchFS, Always, TestOutput (
-        [["write"; "/write_append"; "line1\n"];
+        [["write"; "/internal_write_append"; "line1\n"];
-         ["write_append"; "/write_append"; "line2\n"];
+         ["internal_write_append"; "/internal_write_append"; "line2\n"];
-         ["write_append"; "/write_append"; "line3a"];
+         ["internal_write_append"; "/internal_write_append"; "line3a"];
-         ["write_append"; "/write_append"; "line3b\n"];
+         ["internal_write_append"; "/internal_write_append"; "line3b\n"];
-         ["cat"; "/write_append"]], "line1\nline2\nline3aline3b\n")
+         ["cat"; "/internal_write_append"]], "line1\nline2\nline3aline3b\n")
     ];
     shortdesc = "append content to end of file";
     longdesc = "\

src/file.c

@@ -28,6 +28,7 @@
 #include <sys/stat.h>
 
 #include "full-read.h"
+#include "full-write.h"
 
 #include "guestfs.h"
 #include "guestfs-internal.h"
@@ -290,3 +291,81 @@ guestfs__find (guestfs_h *g, const char *directory)
   }
   return NULL;
 }
+
+static int
+write_or_append (guestfs_h *g, const char *path,
+                 const char *content, size_t size,
+                 int append)
+{
+  char *tmpfile = NULL;
+  int fd = -1;
+  int64_t filesize;
+
+  /* If the content is small enough, use guestfs_internal_write{,_append}
+   * since that call is more efficient.
+   */
+  if (size <= 2*1024*1024)
+    return
+      (!append ? guestfs_internal_write : guestfs_internal_write_append)
+      (g, path, content, size);
+
+  /* Write the content out to a temporary file. */
+  tmpfile = safe_asprintf (g, "%s/write%d", g->tmpdir, ++g->unique);
+
+  fd = open (tmpfile, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0600);
+  if (fd == -1) {
+    perrorf (g, "open: %s", tmpfile);
+    goto err;
+  }
+
+  if (full_write (fd, content, size) != size) {
+    perrorf (g, "write: %s", tmpfile);
+    goto err;
+  }
+
+  if (close (fd) == -1) {
+    perrorf (g, "close: %s", tmpfile);
+    goto err;
+  }
+  fd = -1;
+
+  if (!append) {
+    if (guestfs_upload (g, tmpfile, path) == -1)
+      goto err;
+  }
+  else {
+    /* XXX Should have an 'upload-append' call to make this atomic. */
+    filesize = guestfs_filesize (g, path);
+    if (filesize == -1)
+      goto err;
+    if (guestfs_upload_offset (g, tmpfile, path, filesize) == -1)
+      goto err;
+  }
+
+  unlink (tmpfile);
+  free (tmpfile);
+  return 0;
+
+ err:
+  if (fd >= 0)
+    close (fd);
+  if (tmpfile) {
+    unlink (tmpfile);
+    free (tmpfile);
+  }
+  return -1;
+}
+
+int
+guestfs__write (guestfs_h *g, const char *path,
+                const char *content, size_t size)
+{
+  return write_or_append (g, path, content, size, 0);
+}
+
+int
+guestfs__write_append (guestfs_h *g, const char *path,
+                       const char *content, size_t size)
+{
+  return write_or_append (g, path, content, size, 1);
+}