pstrndup()

Started by Karel Zakover 22 years ago8 messagespatches

zakkr@zf.jcu.cz

over 22 years ago

Hi guys,

we have pstrdup(char *string) and this tiny patch adds
pstrndup(char *sting, Size len).

By the way, I a little played with the apache memory managment and
they have the others interesting routines like ap_pstrcat(...) that
concatenate all arguments (last must be NULL) to new allocated
string. Is something like this interesting for PostgreSQL?

Karel

--
Karel Zak <zakkr@zf.jcu.cz>
http://home.zf.jcu.cz/~zakkr/

Bruce Momjian

bruce@momjian.us

over 22 years ago

In reply to: Karel Zak (#1)

Re: pstrndup()

Karel, do you plan to use pstrndup for some purpose? I assume so.

---------------------------------------------------------------------------

Karel Zak wrote:

Hi guys,

we have pstrdup(char *string) and this tiny patch adds
pstrndup(char *sting, Size len).

By the way, I a little played with the apache memory managment and
they have the others interesting routines like ap_pstrcat(...) that
concatenate all arguments (last must be NULL) to new allocated
string. Is something like this interesting for PostgreSQL?

Karel

--
Karel Zak <zakkr@zf.jcu.cz>
http://home.zf.jcu.cz/~zakkr/

[ Attachment, skipping... ]

---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Tom Lane

tgl@sss.pgh.pa.us

over 22 years ago

In reply to: Bruce Momjian (#2)

Re: pstrndup()

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel, do you plan to use pstrndup for some purpose? I assume so.

I am not familiar with strndup. If the spec is like strncpy, I would
vote against including it ... strncpy is so broken that we had to invent
our own variant ...

regards, tom lane

Karel Zak

zakkr@zf.jcu.cz

over 22 years ago

In reply to: Tom Lane (#3)

Re: pstrndup()

On Sun, Mar 21, 2004 at 11:45:18PM -0500, Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel, do you plan to use pstrndup for some purpose? I assume so.

I think PostgreSQL should supports basic operation with
allocation/strings if it's open for users' C functions and we expect
our own memory system usage.

I am not familiar with strndup. If the spec is like strncpy, I would
vote against including it ... strncpy is so broken that we had to invent
our own variant ...

POSIX strncpy() is different, a result from strncpy needn't be zero
terminated. You're right it's horrible function.

The result of strndup() is always zero terminated. It's more safe and
strndup() is binary safe because it doesn't check something in input
string. The pstrndup() is based on PostgreSQL memory managment.

Karel

--
Karel Zak <zakkr@zf.jcu.cz>
http://home.zf.jcu.cz/~zakkr/

Bruce Momjian

bruce@momjian.us

over 22 years ago

In reply to: Karel Zak (#4)

Re: pstrndup()

Karel Zak wrote:

On Sun, Mar 21, 2004 at 11:45:18PM -0500, Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel, do you plan to use pstrndup for some purpose? I assume so.

I think PostgreSQL should supports basic operation with
allocation/strings if it's open for users' C functions and we expect
our own memory system usage.

I am not familiar with strndup. If the spec is like strncpy, I would
vote against including it ... strncpy is so broken that we had to invent
our own variant ...

POSIX strncpy() is different, a result from strncpy needn't be zero
terminated. You're right it's horrible function.

The result of strndup() is always zero terminated. It's more safe and
strndup() is binary safe because it doesn't check something in input
string. The pstrndup() is based on PostgreSQL memory managment.

Can you find places to use this function our backend? Seems that should
be part of the patch.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Tom Lane

tgl@sss.pgh.pa.us

over 22 years ago

In reply to: Bruce Momjian (#5)

Re: pstrndup()

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel Zak wrote:

The result of strndup() is always zero terminated. It's more safe and
strndup() is binary safe because it doesn't check something in input
string. The pstrndup() is based on PostgreSQL memory managment.

Can you find places to use this function our backend? Seems that should
be part of the patch.

A bit of googling showed that strndup does appear in the "Linux
standards base", but it is not to be found in the Single Unix Spec.
That makes it at most quasi-standard IMHO.

Like Bruce, I'd like to see a more convincing use-case before adopting
not-very-standard functions. I don't think people will expect pstrndup
to exist, or be very likely to use it if it's there, or necessarily know
what its behavior is (for sure I was confused by the naming similarity
with strncpy). That's a lot of strikes for something that replaces only
three lines of C ...

regards, tom lane

Karel Zak

zakkr@zf.jcu.cz

over 22 years ago

In reply to: Tom Lane (#6)

Re: pstrndup()

On Mon, Mar 22, 2004 at 10:04:01AM -0500, Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel Zak wrote:

The result of strndup() is always zero terminated. It's more safe and
strndup() is binary safe because it doesn't check something in input
string. The pstrndup() is based on PostgreSQL memory managment.

Can you find places to use this function our backend? Seems that should
be part of the patch.

A bit of googling showed that strndup does appear in the "Linux
standards base", but it is not to be found in the Single Unix Spec.
That makes it at most quasi-standard IMHO.

man strndup

CONFORMING TO
SVID 3, BSD 4.3

with strncpy). That's a lot of strikes for something that replaces only
three lines of C ...

How often are bugs with "add '\0' to last item of array"?

Well, forget this patch...

Karel

--
Karel Zak <zakkr@zf.jcu.cz>
http://home.zf.jcu.cz/~zakkr/

Bruce Momjian

bruce@momjian.us

over 22 years ago

In reply to: Karel Zak (#7)

Re: pstrndup()

Karel Zak wrote:

On Mon, Mar 22, 2004 at 10:04:01AM -0500, Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

Karel Zak wrote:

The result of strndup() is always zero terminated. It's more safe and
strndup() is binary safe because it doesn't check something in input
string. The pstrndup() is based on PostgreSQL memory managment.

Can you find places to use this function our backend? Seems that should
be part of the patch.

A bit of googling showed that strndup does appear in the "Linux
standards base", but it is not to be found in the Single Unix Spec.
That makes it at most quasi-standard IMHO.

man strndup

CONFORMING TO
SVID 3, BSD 4.3

Strange, I don't see it on FreeBSD or BSD/OS. I wonder if it was
removed in BSD 4.4.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

pstrndup()

Attachments: