Path: csiph.com!x330-a1.tempe.blueboxinc.net!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!border3.nntp.dca.giganews.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail
NNTP-Posting-Date: Wed, 19 Oct 2011 18:02:33 -0500
Message-ID: <4E9F570F.5A16@mindspring.com>
Date: Wed, 19 Oct 2011 19:02:39 -0400
From: pete <pfiland@mindspring.com>
Reply-To: pfiland@mindspring.com
Organization: PF
X-Mailer: Mozilla 3.04Gold (WinNT; I)
MIME-Version: 1.0
Newsgroups: comp.lang.c
Subject: Re: Analogue of ReadLine() in C
References: <91b648bd-bf1e-4093-97a4-77b7300a94c5@c1g2000vbw.googlegroups.com>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 178
X-Usenet-Provider: http://www.giganews.com
NNTP-Posting-Host: 4.156.228.190
X-Trace: sv3-SMc/vGjPIWO/FDIaB9+p1HL120RL8QubPJ9LagranneZT5x7DMpKZyIObzbaS+JifxFyW2MQOxCBIgY!VuoaPSd8lW44bdVe6skWVhr8xP5VEtAB2BoDqFprBsfFauBPFjxfvalT1GEytKoWpMSz52v71fyw!MXLz8H/UwPA=
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
X-Original-Bytes: 5750
Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:11894

=?UTF-8?B?0JzQsNC60YHQuNC8INCk0L7QvNC40L0=?= wrote:
> 
> I need function similar to ReadLine() in any other language.
> The program below fails[1] when data more then LAG_SIZE is passed
> 
> #include <stdio.h>
> #include <stdbool.h>
> #include <string.h>
> #include <stdlib.h>
> 
> char * read_line(void)
> {
>         bool read_more = true;
>         enum { LAG_SIZE = 32 };
>         char *return_buf = NULL;
>         char *new_line_pos = NULL;
>         char tmp_buf[LAG_SIZE] = {'\0'};
>         size_t size = 0;
>         while (read_more && fgets(tmp_buf, LAG_SIZE, stdin)){
>                 char *tmp_realloc;
>                 size += LAG_SIZE;
>                 tmp_realloc = realloc(return_buf, size);
>                 if (!tmp_realloc){
>                         free(return_buf);
>                         return_buf = NULL;
>                         break;
>                 }
>                 return_buf = tmp_realloc;
>                 memset(return_buf + size - LAG_SIZE, '\0', LAG_SIZE);
>                 new_line_pos = strchr(tmp_buf, '\n');
>                 if (new_line_pos){
>                         *new_line_pos = '\0';
>                         read_more = false;
>                 }
>                 strcat(return_buf, tmp_buf);
>                 memset(tmp_buf, '\0', LAG_SIZE);
>         }
>         return return_buf;
> }
> 
> void loop(void)
> {
>         bool repeat = true;
>         while (repeat){
>                 char *command;
>                 printf("Enter> ");
>                 command = read_line();
>                 if (command && !strcmp(command, "exit"))
>                         repeat = false;
>                 free(command);
>         }
> }
> 
> int main(void)
> {
>         loop();
>         return 0;
> }
> 
> [1]: *** glibc detected *** ./a.out: realloc(): invalid next size:
> 0x0804b008 ***

/* BEGIN read_line_test.c */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>

void loop(void);

int read_line(char **lineptr, 
              size_t *n, 
              FILE *stream, 
              size_t *size);

int 
main(void)
{
    loop();
    return 0;
}

void 
loop(void)
{
    int rc;
    char *command = NULL;
    size_t n = 0;

    do {
        printf("Enter> ");
        rc = read_line(&command, &n, stdin, NULL);
    } while (rc > -1 && strcmp(command, "exit"));
    free(command);
}

int 
read_line(char **lineptr, size_t *n, FILE *stream, size_t *size)
{
    int rc;
    size_t count = 0;
    size_t min = 2;

    while ((rc = getc(stream)) != EOF 
        || !feof(stream) && !ferror(stream)) 
    {
        if (++count == (size_t)-2) {
            if (rc != '\n') {
                (*lineptr)[count - 1] = (char)rc;
                (*lineptr)[count++] = '\0';
            } else {
                (*lineptr)[count - 1] = '\0'; 
            }
            break;
        }
        if (++min > *n) {
            void *p;
            size_t max;
            size_t next;

            for (next = min ^ min - 1; min > next; ++next) {
                next *= 2;
            }
            do {
                max = next;
                next = (max - min) / 2 + min;
                p = realloc(*lineptr, max);
            } while (p == NULL && max != min);
            if (p == NULL) {
                if (*n > count) {
                    if (rc != '\n') {
                        (*lineptr)[count - 1] = (char)rc;
                        (*lineptr)[count++] = '\0';
                    } else {
                        (*lineptr)[count - 1] = '\0'; 
                    }
                } else {
                    ungetc(rc, stream);
                    --count;
                    if (*n != 0) {
                        (*lineptr)[count++] = '\0';
                    }
                }
                if (size != NULL) {
                    *size = count;
                }
                count = 0;
                break;
            } else {
                *lineptr = p;
                *n = max;
            }
        }
        if (rc != '\n') {
            (*lineptr)[count - 1] = (char)rc;
        } else {
            (*lineptr)[count - 1] = '\0'; 
            break;
        }
    }
    if (rc != EOF || !feof(stream) && !ferror(stream)) {
        rc = INT_MAX > count ? count : INT_MAX;
    } else {
        if (*n > count) {
            (*lineptr)[count++] = '\0';
        }
    }
    if (size != NULL && rc != 0) {
        *size = count;
    }
    return rc;
}

/* END read_line_test.c */

-- 
pete