From cb2acb1081e13b4b27a76c6b5311115528e49c59 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas
Date: Sun, 28 Jun 2015 21:35:46 +0300
Subject: Add missing_ok option to the SQL functions for reading files.

This makes it possible to use the functions without getting errors, if there
is a chance that the file might be removed or renamed concurrently.
pg_rewind needs to do just that, although this could be useful for other
purposes too. (The changes to pg_rewind to use these functions will come in
a separate commit.)

The read_binary_file() function isn't very well-suited for extensions.c's
purposes anymore, if it ever was. So bite the bullet and make a copy of it
in extension.c, tailored for that use case. This seems better than the
accidental code reuse, even if it's a some more lines of code.

Michael Paquier, with plenty of kibitzing by me.
---
 src/backend/commands/extension.c | 69 ++++++++++++++++++++++++++++++++--------
 1 file changed, 56 insertions(+), 13 deletions(-)

(limited to 'src/backend/commands')

diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 5cc74d03c11..2b1dcd0d19c 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -25,6 +25,8 @@
 
 #include <dirent.h>
 #include <limits.h>
+#include <sys/file.h>
+#include <sys/stat.h>
 #include <unistd.h>
 
 #include "access/htup_details.h"
@@ -51,6 +53,7 @@
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
+#include "utils/memutils.h"
 #include "utils/rel.h"
 #include "utils/snapmgr.h"
 #include "utils/tqual.h"
@@ -103,6 +106,7 @@ static void ApplyExtensionUpdates(Oid extensionOid,
 					  ExtensionControlFile *pcontrol,
 					  const char *initialVersion,
 					  List *updateVersions);
+static char *read_whole_file(const char *filename, int *length);
 
 
 /*
@@ -635,12 +639,11 @@ read_extension_script_file(const ExtensionControlFile *control,
 						   const char *filename)
 {
 	int			src_encoding;
-	bytea	   *content;
 	char	   *src_str;
 	char	   *dest_str;
 	int			len;
 
-	content = read_binary_file(filename, 0, -1);
+	src_str = read_whole_file(filename, &len);
 
 	/* use database encoding if not given */
 	if (control->encoding < 0)
@@ -649,21 +652,15 @@ read_extension_script_file(const ExtensionControlFile *control,
 		src_encoding = control->encoding;
 
 	/* make sure that source string is valid in the expected encoding */
-	len = VARSIZE_ANY_EXHDR(content);
-	src_str = VARDATA_ANY(content);
 	pg_verify_mbstr_len(src_encoding, src_str, len, false);
 
-	/* convert the encoding to the database encoding */
+	/*
+	 * Convert the encoding to the database encoding. read_whole_file
+	 * null-terminated the string, so if no conversion happens the string is
+	 * valid as is.
+	 */
 	dest_str = pg_any_to_server(src_str, len, src_encoding);
 
-	/* if no conversion happened, we have to arrange for null termination */
-	if (dest_str == src_str)
-	{
-		dest_str = (char *) palloc(len + 1);
-		memcpy(dest_str, src_str, len);
-		dest_str[len] = '\0';
-	}
-
 	return dest_str;
 }
 
@@ -3008,3 +3005,49 @@ ExecAlterExtensionContentsStmt(AlterExtensionContentsStmt *stmt,
 
 	return extension;
 }
+
+/*
+ * Read the whole of file into memory.
+ *
+ * The file contents are returned as a single palloc'd chunk. For convenience
+ * of the callers, an extra \0 byte is added to the end.
+ */
+static char *
+read_whole_file(const char *filename, int *length)
+{
+	char	   *buf;
+	FILE	   *file;
+	size_t		bytes_to_read;
+	struct stat fst;
+
+	if (stat(filename, &fst) < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not stat file \"%s\": %m", filename)));
+
+	if (fst.st_size > (MaxAllocSize - 1))
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("file too large")));
+	bytes_to_read = (size_t) fst.st_size;
+
+	if ((file = AllocateFile(filename, PG_BINARY_R)) == NULL)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open file \"%s\" for reading: %m",
+						filename)));
+
+	buf = (char *) palloc(bytes_to_read + 1);
+
+	*length = fread(buf, 1, bytes_to_read, file);
+
+	if (ferror(file))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not read file \"%s\": %m", filename)));
+
+	FreeFile(file);
+
+	buf[*length] = '\0';
+	return buf;
+}
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