Directory reading

How to read a million inodes as fast as possible. More...

Defines
#define	HAVE_GETDENTS64   1
	If the system fulfills all necessary checks to use getdents(), this macro is set.
Typedefs
typedef int	dir__handle
	The type of handle.
typedef struct dirent64	fsvs_dirent
	A compatibility structure.
Functions
int	dir__start_enum (dir__handle *dh, char *path)
	Starts enumeration of the given path.
int	dir__enum (dir__handle dh, fsvs_dirent *dirp, unsigned int count)
	The enumeration function.
int	dir__close (dir__handle dh)
	Simply closes the handle dh.
int	dir__get_dir_size (dir__handle dh, struct sstat_t *st)
	How to get the length of a directory (in bytes), from a handle dh, into st->size.

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Detailed Description

How to read a million inodes as fast as possible.

Why?

Why do we care for getdents64 instead of simply using the (portable) readdir()?

• getdents64 gives 64bit inodes (which we need on big filesystems)
• as getdents64 gives up to (currently) 4096 bytes of directory data, we save some amount of library and/or kernel calls - for 32 byte per directory entry (estimated, measured, averaged) we get a maximum of about 128 directory entries per call - which saves many syscalls and much time. Not counting the overhead of the apr- and libc-layers ... which we should (have to) use for eg. windows.

How?

We have two kinds of directory reading codes.

• A fast one with getdents64() (linux-specific)
• A compatibility layer using opendir() / readdir() / closedir().

Which one to use is defined by configure.

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Define Documentation

#define HAVE_GETDENTS64   1

If the system fulfills all necessary checks to use getdents(), this macro is set.

Definition at line 62 of file direnum.c.

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Typedef Documentation

typedef int dir__handle

The type of handle.

Definition at line 73 of file direnum.c.

typedef struct dirent64 fsvs_dirent

A compatibility structure.

It has an inode; a name; and a record length in it, to get from one record to the next.

Definition at line 77 of file direnum.c.

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Function Documentation

int dir__close

(

dir__handle

dh

)

[inline]

Simply closes the handle dh.

Definition at line 111 of file direnum.c.

References STOPIF_CODE_ERR.

Referenced by dir__enumerator().

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int dir__enum	(	dir__handle	dh,
		fsvs_dirent *	dirp,
		unsigned int	count
	)			[inline]

The enumeration function.

Parameters:

	dh	The handle given by dir__start_enum.
	dirp	The space where data should be returned
	count	The maximum number of bytes in dirp.

Returns:

The number of bytes used in dirp.

Definition at line 103 of file direnum.c.

Referenced by dir__enumerator().

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int dir__get_dir_size	(	dir__handle	dh,
		struct sstat_t *	st
	)			[inline]

How to get the length of a directory (in bytes), from a handle dh, into st->size.

Definition at line 126 of file direnum.c.

References hlp__fstat(), and STOPIF.

Referenced by dir__enumerator().

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int dir__start_enum	(	dir__handle *	dh,
		char *	path
	)			[inline]

Starts enumeration of the given path.

The directory handle is returned in *dirp.

Returns:

0 for success, or an error code.

Definition at line 83 of file direnum.c.

References STOPIF_CODE_ERR.

Referenced by dir__enumerator().

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