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Analogue of ReadLine() in C

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  Analogue of ReadLine() in C Максим Фомин <maxim@maxim-fomin.ru> - 2011-10-19 12:26 -0700
    Re: Analogue of ReadLine() in C China Blue Corn Chips <chine.bleu@yahoo.com> - 2011-10-19 13:05 -0700
      Re: Analogue of ReadLine() in C China Blue Corn Chips <chine.bleu@yahoo.com> - 2011-10-19 20:50 -0700
        Re: Analogue of ReadLine() in C Seebs <usenet-nospam@seebs.net> - 2011-10-20 07:42 +0000
          Re: Analogue of ReadLine() in C China Blue Corn Chips <chine.bleu@yahoo.com> - 2011-10-20 02:51 -0700
            Re: Analogue of ReadLine() in C gazelle@shell.xmission.com (Kenny McCormack) - 2011-10-20 12:52 +0000
            Re: Analogue of ReadLine() in C "BartC" <bc@freeuk.com> - 2011-10-20 14:31 +0100
              Re: Analogue of ReadLine() in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-10-20 08:05 -0700
                Re: Analogue of ReadLine() in C gazelle@shell.xmission.com (Kenny McCormack) - 2011-10-20 15:15 +0000
                Re: Analogue of ReadLine() in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-20 16:50 +0100
                Re: Analogue of ReadLine() in C "BartC" <bc@freeuk.com> - 2011-10-20 23:23 +0100
                  Re: Analogue of ReadLine() in C Keith Thompson <kst-u@mib.org> - 2011-10-20 15:34 -0700
                    Re: Analogue of ReadLine() in C Ian Collins <ian-news@hotmail.com> - 2011-10-21 14:10 +1300
                    Re: Analogue of ReadLine() in C "BartC" <bc@freeuk.com> - 2011-10-21 10:30 +0100
                      Re: Analogue of ReadLine() in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-10-21 05:59 -0700
                      Re: Analogue of ReadLine() in C Keith Thompson <kst-u@mib.org> - 2011-10-21 10:58 -0700
                        Re: Analogue of ReadLine() in C "BartC" <bc@freeuk.com> - 2011-10-22 20:00 +0100
                          Re: Analogue of ReadLine() in C Ian Collins <ian-news@hotmail.com> - 2011-10-23 08:09 +1300
                          Re: Analogue of ReadLine() in C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-10-22 23:55 -0700
              Re: Analogue of ReadLine() in C Ian Collins <ian-news@hotmail.com> - 2011-10-21 08:34 +1300
            Re: Analogue of ReadLine() in C Seebs <usenet-nospam@seebs.net> - 2011-10-20 17:57 +0000
            Re: Analogue of ReadLine() in C Markus Wichmann <nullplan@gmx.net> - 2011-10-23 23:03 +0200
              Re: Analogue of ReadLine() in C Acid Washed China Blue Jeans <chine.bleu@yahoo.com> - 2011-10-24 00:31 -0700
              Re: Analogue of ReadLine() in C Richard Damon <news.x.richarddamon@xoxy.net> - 2011-10-24 08:10 -0400
    Re: Analogue of ReadLine() in C 88888 Dihedral <dihedral88888@googlemail.com> - 2011-10-19 14:04 -0700
      Re: Analogue of ReadLine() in C Kaz Kylheku <kaz@kylheku.com> - 2011-10-19 21:52 +0000
    Re: Analogue of ReadLine() in C Ike Naar <ike@iceland.freeshell.org> - 2011-10-19 22:34 +0000
    Re: Analogue of ReadLine() in C pete <pfiland@mindspring.com> - 2011-10-19 19:02 -0400
      Re: Analogue of ReadLine() in C pete <pfiland@mindspring.com> - 2011-10-20 00:36 -0400
    Re: Analogue of ReadLine() in C Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-10-20 00:11 -0700
      Re: Analogue of ReadLine() in C Максим Фомин <maxim@maxim-fomin.ru> - 2011-10-20 01:59 -0700
    Re: Analogue of ReadLine() in C James Kuyper <jameskuyper@verizon.net> - 2011-10-20 06:57 -0400
    Re: Analogue of ReadLine() in C Markus Wichmann <nullplan@gmx.net> - 2011-10-20 18:40 +0200
      Re: Analogue of ReadLine() in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-20 18:20 +0100
        Re: Analogue of ReadLine() in C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-10-21 08:58 +0000
          Re: Analogue of ReadLine() in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-21 19:12 +0100
          Re: Analogue of ReadLine() in C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-10-21 19:35 +0100
            Re: Analogue of ReadLine() in C "io_x" <a@b.c.invalid> - 2011-10-22 18:58 +0200
          Re: Analogue of ReadLine() in C David Thompson <dave.thompson2@verizon.net> - 2011-10-28 01:34 -0400
    Re: Analogue of ReadLine() in C Michael Angelo Ravera <maravera@prodigy.net> - 2011-10-20 13:32 -0700
      Re: Analogue of ReadLine() in C James Kuyper <jameskuyper@verizon.net> - 2011-10-20 16:42 -0400
      Re: Analogue of ReadLine() in C "Morris Keesan" <mkeesan@post.harvard.edu> - 2011-10-20 16:47 -0400
    Re: Analogue of ReadLine() in C Shao Miller <sha0.miller@gmail.com> - 2012-01-07 14:37 -0500

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#11923

On 10/20/2011 04:32 PM, Michael Angelo Ravera wrote:
...
> The reason that you code fails is that you can't generally realloc
> what you haven't [m|c|0]alloc'd.

What's the 0 for? 0alloc'd?

You are also allowed to realloc() a null pointer, or a pointer returned
by a previous successful call to realloc() that has not yet been free()d
or successfully realloc()d again. As far as I can see, those are the
only two things this code ever realloc()s. Have I missed something?

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#11924

On Thu, 20 Oct 2011 16:32:06 -0400, Michael Angelo Ravera  
<maravera@prodigy.net> wrote:

> The reason that you code fails is that you can't generally realloc what  
> you haven't [m|c|0]alloc'd.

Wrong.  From the C99 standard, ISO/IEC 9899:1999 (E)

7.20.3.4 The realloc function

Synopsis
       #include <stdlib.h>
       void *realloc(void *ptr, size_t size);
...
If ptr is a null pointer, the realloc function behaves like the
malloc function for the specified size.

-- 
Morris Keesan -- mkeesan@post.harvard.edu

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#15554

On 10/19/2011 15:26, Максим Фомин wrote:
> I need function similar to ReadLine() in any other language.
> The program below fails[1] when data more then LAG_SIZE is passed
>
> [...code...]

I guess the biggest line you can handle is limited by the biggest 
contiguous range of memory that you can allocate.  Maybe you could 
allocate as large a buffer as possible when your program starts, then 
each time you read a line, try to fill the buffer from the beginning and 
worry about what happens when you don't find a newline before that 
buffer has been filled.

Here's a silly little bit of code to allocate a large buffer, which is 
also available at http://codepad.org/nLoYZzej:

   /* For use with C89 */

   #include <stddef.h>
   #include <stdlib.h>

   static void * biggest_buf(void);

   int main(void) {
       char * foo;

       foo = biggest_buf();
       free(foo);
       return EXIT_SUCCESS;
     }

   static void * biggest_buf(void) {
       char * big_buf;
       size_t max_size, big_size, test_size, highest_test;

       /* Find the maximum size_t */
       max_size = 0;
       --max_size;

       switch (1) while (1) {
           /* big_size < test_size < highest_test */
           big_buf = malloc(test_size);
           if (!big_buf) {
               if (test_size == big_size) {
                   /* Maximum allocation has changed.  Start over */
                   case 1:
                   test_size = highest_test = max_size;
                   big_size = 0;
                   continue;
                 }
               /*
                * We couldn't allocate a bigger buffer than last time.
                * Split the difference and try a smaller allocation
                */
               highest_test = test_size;
               test_size = (test_size - big_size) / 2 + big_size;
               continue;
             }

           /* Check if we've found the biggest allocation */
           if (test_size == big_size) {
               /* All done */
               break;
             }

           /* Otherwise, we might be able to allocate more */
           free(big_buf);
           big_size = test_size;
           test_size = (highest_test - big_size) / 2 + big_size;
           continue;
         }
       return big_buf;
     }

- Shao Miller

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