fgetsany.c

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/************************************************************************/
/**

   \file       fgetsany.c
   
   \version    V1.1
   \date       07.07.14
   \brief      Like fgets(), but allocates memory and returns pointer
               to memory block
   
   \copyright  (c) UCL / Dr. Andrew C. R. Martin 1995-2014
   \author     Dr. Andrew C. R. Martin
   \par
               Institute of Structural & Molecular Biology,
               University College London,
               Gower Street,
               London.
               WC1E 6BT.
   \par
               andrew@bioinf.org.uk
               andrew.martin@ucl.ac.uk
               
**************************************************************************

   This code is NOT IN THE PUBLIC DOMAIN, but it may be copied
   according to the conditions laid out in the accompanying file
   COPYING.DOC.

   The code may be modified as required, but any modifications must be
   documented so that the person responsible can be identified.

   The code may not be sold commercially or included as part of a 
   commercial product except as described in the file COPYING.DOC.

**************************************************************************

   Description:
   ============


   blFgetsany() provides a routine like fgets() for reading strings from
   a file, but does not require you to impose a limit on the length of
   string which may be read. fgetsany() allocates memory to store a
   string of any length and returns a pointer to that allocated memory.
   After use, this memory must be freed by the calling routine.

**************************************************************************

   Usage:
   ======

   blFgetsany() returns NULL on end-of-file and if memory allocation
   failed. It uses the global `errno' variable to indicate a memory
   allocation failure (errno==ENOMEM). 

   Typical usage is as follows:

\code

   #include "bioplib/general.h"

   main()
   {
      char *ptr;
      FILE *fp;
   
      fp = fopen("test.txt","r");
   
      while((ptr=blFgetsany(fp))!=NULL)
      {
         printf("%s",ptr);
         free(ptr);
      }
   
      if(errno)
         perror("SYSTEM ERROR");
   }

\endcode

**************************************************************************

   Revision History:
   =================

-  V1.0  11.09.95 Original    By: ACRM
-  V1.1  07.07.14 Use bl prefix for functions By: CTP

*************************************************************************/
/* Doxygen
   -------
   #GROUP    General Programming
   #SUBGROUP File IO
   #FUNCTION  blFgetsany()
   blFgetsany() provides a routine like fgets() for reading strings from
   a file, but does not require you to impose a limit on the length of
   string which may be read. 
*/
/************************************************************************/
/* Includes
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

/************************************************************************/
/* Defines and macros
*/
#define MAXBUFF 80   /* Memory allocated in chunks of this size         */

/************************************************************************/
/* Globals
*/

extern int errno;

/************************************************************************/
/* Prototypes
*/

/************************************************************************/
/*>char *blFgetsany(FILE *fp)
   --------------------------
*//**

   \param[in]     *fp           File pointer open for reading
   \return                      Allocated string or NULL on EOF and
                                no memory (errno==ENOMEM)

   blFgetsany() provides a routine like fgets() for reading strings from
   a file, but does not require you to impose a limit on the length of
   string which may be read. blFgetsany() allocates memory to store a
   string of any length and returns a pointer to that allocated memory.
   After use, this memory must be freed by the calling routine.

   blFgetsany() returns NULL on end-of-file and if memory allocation
   failed. It uses the global `errno' variable to indicate a memory
   allocation failure (errno==ENOMEM). 

-  11.09.95 Original    By: ACRM
-  07.07.14 Use bl prefix for functions By: CTP
*/
char *blFgetsany(FILE *fp)
{
   int  bufflen = MAXBUFF,
        buffpos = 0,
        ch;
   char *buffer = NULL;

   /* Get a character and test for end of file                          */
   if((ch = fgetc(fp))==EOF)
      return(NULL);

   /* If it wasn't EOF, put the character back in the input stream      */
   ungetc(ch, fp);
   
   /* OK, wasn't EOF, so allocate initial buffer space                  */
   if((buffer = (char *)malloc(bufflen * sizeof(char)))==NULL)
   {
      errno = ENOMEM;
      return(NULL);
   }

   /* Read characters from file                                         */
   do 
   {
      ch = fgetc(fp);

      /* If it's not end of file, store the character                   */
      if(ch != EOF)
      {
         buffer[buffpos] = ch;

         /* Increment buffer position and test for overflow             */
         if(++buffpos == bufflen)
         {
            bufflen += MAXBUFF;
   
            /* Allocate additional space on overflow                    */
            if((buffer = realloc(buffer, bufflen))==NULL)
            {
               errno = ENOMEM;
               return(NULL);
            }
         }
      }
   }  while((ch != EOF) && (ch != '\n'));
   
   /* Terminate the string                                              */
   buffer[buffpos] = '\0';

   /* If haven't used all the buffer, shrink it down to used size       */
   if(++buffpos < bufflen)
   {
      if((buffer = realloc(buffer, bufflen))==NULL)
      {
         errno = ENOMEM;
         return(NULL);
      }
   }
   
   return(buffer);
}