nss_files: Add generic code for set*ent, end*ent and file open

This reduces RSS usage if nss_files is not actually used, and can
be used later to make NSS data thread-specific.  It also results in
a small code size reduction.

Before:

   text	   data	    bss	    dec	    hex	filename
   2288	      0	     72	   2360	    938	nss/files-alias.os
   1807	      0	     72	   1879	    757	nss/files-ethers.os
   1371	      0	     72	   1443	    5a3	nss/files-grp.os
   6246	      0	     72	   6318	   18ae	nss/files-hosts.os
    869	      0	      0	    869	    365	nss/files-initgroups.os
    666	      0	      0	    666	    29a	nss/files-init.os
   1934	      0	      0	   1934	    78e	nss/files-netgrp.os
   2353	      0	     72	   2425	    979	nss/files-network.os
   2130	      0	     72	   2202	    89a	nss/files-proto.os
   1372	      0	     72	   1444	    5a4	nss/files-pwd.os
   2124	      0	     72	   2196	    894	nss/files-rpc.os
   2265	      0	     72	   2337	    921	nss/files-service.os
   1125	      0	     72	   1197	    4ad	nss/files-sgrp.os
   1124	      0	     72	   1196	    4ac	nss/files-spwd.os

After:

   text	   data	    bss	    dec	    hex	filename
   2040	      0	      0	   2040	    7f8	nss/files-alias.os
   1599	      0	      0	   1599	    63f	nss/files-ethers.os
   1155	      0	      0	   1155	    483	nss/files-grp.os
   6010	      0	      0	   6010	   177a	nss/files-hosts.os
    869	      0	      0	    869	    365	nss/files-initgroups.os
    666	      0	      0	    666	    29a	nss/files-init.os
   1934	      0	      0	   1934	    78e	nss/files-netgrp.os
   2129	      0	      0	   2129	    851	nss/files-network.os
   1914	      0	      0	   1914	    77a	nss/files-proto.os
   1156	      0	      0	   1156	    484	nss/files-pwd.os
   1908	      0	      0	   1908	    774	nss/files-rpc.os
   2057	      0	      0	   2057	    809	nss/files-service.os
    909	      0	      0	    909	    38d	nss/files-sgrp.os
    908	      0	      0	    908	    38c	nss/files-spwd.os
   1090	      0	      8	   1098	    44a	nss/nss_files_data.os

27674 code bytes before, 26344 code bytes after, so it is an overall
win despite the extra initialization code.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 60 insertions, 0 deletions

diff --git a/include/nss_files.h b/include/nss_files.h
index 6a0dcdb85b..7bf1951496 100644
--- a/include/nss_files.h
+++ b/include/nss_files.h
@@ -20,6 +20,9 @@
 #define _NSS_FILES_H
 
 #include <stdio.h>
+#if IS_IN (libc)
+#include <libc-lock.h>
+#endif
 
 /* Open PATH for reading, as a data source for nss_files.  */
 FILE *__nss_files_fopen (const char *path);
@@ -47,6 +50,63 @@ int __nss_readline_seek (FILE *fp, off64_t offset) attribute_hidden;
 int __nss_parse_line_result (FILE *fp, off64_t offset, int parse_line_result);
 libc_hidden_proto (__nss_parse_line_result)
 
+/* Per-file data.  Used by the *ent functions that need to preserve
+   state across calls.  */
+struct nss_files_per_file_data
+{
+  FILE *stream;
+#if IS_IN (libc)
+  /* The size of locks changes between libc and nss_files, so this
+     member must be last and is only available in libc.  */
+  __libc_lock_define (, lock);
+#endif
+};
+
+/* File index for __nss_files_data_get.  */
+enum nss_files_file
+  {
+    nss_file_aliasent,
+    nss_file_etherent,
+    nss_file_grent,
+    nss_file_hostent,
+    nss_file_netent,
+    nss_file_protoent,
+    nss_file_pwent,
+    nss_file_rpcent,
+    nss_file_servent,
+    nss_file_sgent,
+    nss_file_spent,
+
+    nss_file_count
+  };
+
+/* Obtains a pointer to the per-file data for FILE, which is written
+   to *PDATA, and tries to open the file at PATH for it.  On success,
+   returns NSS_STATUS_SUCCESS, and the caller must later call
+   __nss_files_data_put.  On failure, NSS_STATUS_TRYAGAIN is returned,
+   and *ERRNOP and *HERRNOP are updated if these pointers are not
+   null.  */
+enum nss_status __nss_files_data_open (struct nss_files_per_file_data **pdata,
+                                       enum nss_files_file file,
+                                       const char *path,
+                                       int *errnop, int *herrnop);
+libc_hidden_proto (__nss_files_data_open)
+
+/* Unlock the per-file data, previously obtained by
+   __nss_files_data_open.  */
+void __nss_files_data_put (struct nss_files_per_file_data *data);
+libc_hidden_proto (__nss_files_data_put)
+
+/* Performs the set*ent operation for FILE.  PATH is the file to
+   open.  */
+enum nss_status __nss_files_data_setent (enum nss_files_file file,
+                                           const char *path);
+libc_hidden_proto (__nss_files_data_setent)
+
+/* Performs the end*ent operation for FILE.  */
+enum nss_status __nss_files_data_endent (enum nss_files_file file);
+libc_hidden_proto (__nss_files_data_endent)
+
 struct parser_data;
 
 /* Instances of the parse_line function from