/*-------------------------------------------------------------------------
?*
?*?adminpack.c
?*
?*
?*?Copyright?（c）?2002-2017?PostgreSQL?Global?Development?Group
?*
?*?Author:?Andreas?Pflug?
?*
?*?IDENTIFICATION
?*	??contrib/adminpack/adminpack.c
?*
?*-------------------------------------------------------------------------
?*/
#include?“postgres.h“

#include?
#include?
#include?

#include?“catalog/pg_type.h“
#include?“funcapi.h“
#include?“miscadmin.h“
#include?“postmaster/syslogger.h“
#include?“storage/fd.h“
#include?“utils/builtins.h“
#include?“utils/datetime.h“


#ifdef?WIN32

#ifdef?rename
#undef?rename
#endif

#ifdef?unlink
#undef?unlink
#endif
#endif

PG_MODULE_MAGIC;

PG_FUNCTION_INFO_V1（pg_file_write）;
PG_FUNCTION_INFO_V1（pg_file_rename）;
PG_FUNCTION_INFO_V1（pg_file_unlink）;
PG_FUNCTION_INFO_V1（pg_logdir_ls）;

typedef?struct
{
	char	???*location;
	DIR		???*dirdesc;
}?directory_fctx;

/*-----------------------
?*?some?helper?functions
?*/

/*
?*?Convert?a?“text“?filename?argument?to?C?string?and?check?it‘s?allowable.
?*
?*?Filename?may?be?absolute?or?relative?to?the?DataDir?but?we?only?allow
?*?absolute?paths?that?match?DataDir?or?Log_directory.
?*/
static?char?*
convert_and_check_filename（text?*arg?bool?logAllowed）
{
	char	???*filename?=?text_to_cstring（arg）;

	canonicalize_path（filename）;	/*?filename?can?change?length?here?*/

	if?（is_absolute_path（filename））
	{
		/*?Disallow?‘/a/b/data/..‘?*/
		if?（path_contains_parent_reference（filename））
			ereport（ERROR
					（errcode（ERRCODE_INSUFFICIENT_PRIVILEGE）
					?（errmsg（“reference?to?parent?directory?（\“..\“）?not?allowed“））））;

		/*
		?*?Allow?absolute?paths?if?within?DataDir?or?Log_directory?even
		?*?though?Log_directory?might?be?outside?DataDir.
		?*/
		if?（!path_is_prefix_of_path（DataDir?filename）?&&
			（!logAllowed?||?!is_absolute_path（Log_directory）?||
			?!path_is_prefix_of_path（Log_directory?filename）））
			ereport（ERROR
					（errcode（ERRCODE_INSUFFICIENT_PRIVILEGE）
					?（errmsg（“absolute?path?not?allowed“））））;
	}
	else?if?（!path_is_relative_and_below_cwd（filename））
		ereport（ERROR
				（errcode（ERRCODE_INSUFFICIENT_PRIVILEGE）
				?（errmsg（“path?must?be?in?or?below?the?current?directory“））））;

	return?filename;
}


/*
?*?check?for?superuser?bark?if?not.
?*/
static?void
requireSuperuser（void）
{
	if?（!superuser（））
		ereport（ERROR
				（errcode（ERRCODE_INSUFFICIENT_PRIVILEGE）
				?（errmsg（“only?superuser?may?access?generic?file?functions“））））;
}



/*?------------------------------------
?*?generic?file?handling?functions
?*/

Datum
pg_file_write（PG_FUNCTION_ARGS）
{
	FILE	???*f;
	char	???*filename;
	text	???*data;
	int64		count?=?0;

	requireSuperuser（）;

	filename?=?convert_and_check_filename（PG_GETARG_TEXT_PP（0）?false）;
	data?=?PG_GETARG_TEXT_PP（1）;

	if?（!PG_GETARG_BOOL（2））
	{
		struct?stat?fst;

		if?（stat（filename?&fst）?>=?0）
			ereport（ERROR
					（ERRCODE_DUPLICATE_FILE
					?errmsg（“file?\“%s\“?exists