libxl: New utility functions in for reading and writing files.

We introduce these functions in libxl_utils.h:

  int libxl_read_file_contents(struct libxl_ctx *ctx, const char
  *filename,
                               void **data_r, int *datalen_r);
  int libxl_read_exactly(struct libxl_ctx *ctx, int fd, void *data,
  ssize_t sz,
                         const char *filename, const char *what);
  int libxl_write_exactly(struct libxl_ctx *ctx, int fd, const void
  *data,
                          ssize_t sz, const char *filename, const char
  *what);

They will be needed by the following patches.  They have to be in
libxl.a rather than libxutil.a because they will be used, amongst
other places, in libxl itself.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/tools/libxl/libxl_utils.h b/tools/libxl/libxl_utils.h
index 05fa4e368f..65e7e31d23 100644
--- a/tools/libxl/libxl_utils.h
+++ b/tools/libxl/libxl_utils.h
@@ -26,5 +26,23 @@ int libxl_is_stubdom(struct libxl_ctx *ctx, uint32_t domid, uint32_t *target_dom
 int libxl_create_logfile(struct libxl_ctx *ctx, char *name, char **full_name);
 int libxl_string_to_phystype(struct libxl_ctx *ctx, char *s, libxl_disk_phystype *phystype);
 
+int libxl_read_file_contents(struct libxl_ctx *ctx, const char *filename,
+                             void **data_r, int *datalen_r);
+  /* Reads the contents of the plain file filename into a mallocd
+   * buffer.  Returns 0 or errno.  Any errors other than ENOENT are logged.
+   * If the file is empty, *data_r and *datalen_r are set to 0.
+   * On error, *data_r and *datalen_r are undefined.
+   * data_r and/or datalen_r may be 0.
+   */
+
+int libxl_read_exactly(struct libxl_ctx *ctx, int fd, void *data, ssize_t sz,
+                       const char *filename, const char *what);
+int libxl_write_exactly(struct libxl_ctx *ctx, int fd, const void *data,
+                        ssize_t sz, const char *filename, const char *what);
+  /* Returns 0 or errno.  If file is truncated on reading, returns
+   * EPROTO and you have no way to tell how much was read.  Errors are
+   * logged using filename (which is only used for logging) and what
+   * (which may be 0). */
+    
 #endif