Re: closein, freadahead and ungetc

[Bruno Haible]

Eric Blake wrote:
> |   - freadptr is changed to also return the size of the buffer.
> |       extern const char * freadptr (FILE *stream, size_t *sizep);
> |     When the return value is non-NULL, *sizep is set to the size of the
> |     buffer whose address is the return value.
> 
> Sounds fine to me.

Here is the first part, the extended freadptr API.

2008-03-09  Bruno Haible  <address@hidden>

        Extend freadptr to return also the buffer size.
        * lib/freadptr.h (freadptr): Add sizep argument.
        * lib/freadptr.c: Include freadptr.h, not freadahead.h.
        (freadptr): Add sizep argument. Determine buffer size like freadahead
        does.
        * tests/test-freadptr.c: Don't include freadahead.h.
        (main): Adapt for new calling convention of freadptr.
        * tests/test-freadptr2.c: New file, based on tests/test-freadahead.c.
        * tests/test-freadptr2.sh: New file, based on tests/test-freadahead.sh.
        * modules/freadptr-tests (Files): Add tests/test-freadptr2.c,
        tests/test-freadptr2.sh.
        (Depends): Remove freadahead.
        (TESTS): Add test-freadptr2.sh.
        (check_PROGRAMS): Add test-freadptr2.

*** lib/freadptr.h.orig 2008-03-10 00:14:43.000000000 +0100
--- lib/freadptr.h      2008-03-09 23:10:57.000000000 +0100
***************
*** 22,40 ****
  #endif
  
  /* Assuming the stream STREAM is open for reading:
!    Return a pointer to the input buffer of STREAM.
!    If freadahead (STREAM) > 0, the result is either a pointer to
!    freadahead (STREAM) bytes, or NULL.  The latter case can happen after
!    use of 'ungetc (..., STREAM)'.
!    If freadahead (STREAM) == 0, the result is not usable; it may be NULL.
!    In this case, you should use getc (STREAM), fgetc (STREAM), or
!    fread (..., STREAM) to access the input from STREAM.
  
     The resulting pointer becomes invalid upon any operation on STREAM.
  
     STREAM must not be wide-character oriented.  */
  
! extern const char * freadptr (FILE *stream);
  
  #ifdef __cplusplus
  }
--- 22,38 ----
  #endif
  
  /* Assuming the stream STREAM is open for reading:
!    Return a pointer to the input buffer of STREAM, or NULL.
!    If the returned pointer is non-NULL, *SIZEP is set to the (positive) size
!    of the input buffer.
!    If the returned pointer is NULL, you should use getc (STREAM),
!    fgetc (STREAM), or fread (..., STREAM) to access the input from STREAM.
  
     The resulting pointer becomes invalid upon any operation on STREAM.
  
     STREAM must not be wide-character oriented.  */
  
! extern const char * freadptr (FILE *stream, size_t *sizep);
  
  #ifdef __cplusplus
  }
*** lib/freadptr.c.orig 2008-03-10 00:14:43.000000000 +0100
--- lib/freadptr.c      2008-03-10 00:11:51.000000000 +0100
***************
*** 17,31 ****
  #include <config.h>
  
  /* Specification.  */
! #include "freadahead.h"
  
  const char *
! freadptr (FILE *fp)
  {
    /* Keep this code in sync with freadahead!  */
  #if defined _IO_ferror_unlocked     /* GNU libc, BeOS */
    return (const char *) fp->_IO_read_ptr;
  #elif defined __sferror             /* FreeBSD, NetBSD, OpenBSD, MacOS X, 
Cygwin */
    return (const char *) fp->_p;
  #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, 
mingw */
  # if defined __sun && defined _LP64 /* Solaris/{SPARC,AMD64} 64-bit */
--- 17,45 ----
  #include <config.h>
  
  /* Specification.  */
! #include "freadptr.h"
  
  const char *
! freadptr (FILE *fp, size_t *sizep)
  {
+   size_t size;
+ 
    /* Keep this code in sync with freadahead!  */
  #if defined _IO_ferror_unlocked     /* GNU libc, BeOS */
+   if (fp->_IO_write_ptr > fp->_IO_write_base)
+     return NULL;
+   size = fp->_IO_read_end - fp->_IO_read_ptr;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp->_IO_read_ptr;
  #elif defined __sferror             /* FreeBSD, NetBSD, OpenBSD, MacOS X, 
Cygwin */
+   if ((fp->_flags & __SWR) != 0 || fp->_r < 0)
+     return NULL;
+   size = fp->_r;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp->_p;
  #elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, 
mingw */
  # if defined __sun && defined _LP64 /* Solaris/{SPARC,AMD64} 64-bit */
***************
*** 36,54 ****
                         int _file; \
                         unsigned int _flag; \
                       } *) fp)
    return (const char *) fp_->_ptr;
  # else
    return (const char *) fp->_ptr;
  # endif
  #elif defined __UCLIBC__            /* uClibc */
  # ifdef __STDIO_BUFFERS
    return (const char *) fp->__bufpos;
  # else
    return NULL;
  # endif
  #elif defined __QNX__               /* QNX */
    return (const char *) fp->_Next;
  #else
!  #error "Please port gnulib freadptr.c to your platform! Look at the 
definition of getc, getc_unlocked on your system, then report this to 
bug-gnulib."
  #endif
  }
--- 50,93 ----
                         int _file; \
                         unsigned int _flag; \
                       } *) fp)
+   if ((fp_->_flag & _IOWRT) != 0)
+     return NULL;
+   size = fp_->_cnt;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp_->_ptr;
  # else
+   if ((fp->_flag & _IOWRT) != 0)
+     return NULL;
+   size = fp->_cnt;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp->_ptr;
  # endif
  #elif defined __UCLIBC__            /* uClibc */
  # ifdef __STDIO_BUFFERS
+   if (fp->__modeflags & __FLAG_WRITING)
+     return NULL;
+   size = fp->__bufread - fp->__bufpos;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp->__bufpos;
  # else
    return NULL;
  # endif
  #elif defined __QNX__               /* QNX */
+   if ((fp->_Mode & 0x2000 /* _MWRITE */) != 0)
+     return NULL;
+   /* fp->_Buf <= fp->_Next <= fp->_Rend */
+   size = fp->_Rend - fp->_Next;
+   if (size == 0)
+     return NULL;
+   *sizep = size;
    return (const char *) fp->_Next;
  #else
!  #error "Please port gnulib freadptr.c to your platform! Look at the 
definition of fflush, fread, getc, getc_unlocked on your system, then report 
this to bug-gnulib."
  #endif
  }
*** tests/test-freadptr.c.orig  2008-03-10 00:14:43.000000000 +0100
--- tests/test-freadptr.c       2008-03-09 23:26:37.000000000 +0100
***************
*** 25,32 ****
  #include <string.h>
  #include <unistd.h>
  
- #include "freadahead.h"
- 
  #define ASSERT(expr) \
    do                                                                       \
      {                                                                      \
--- 25,30 ----
***************
*** 46,125 ****
    ASSERT (fread (buf, 1, nbytes, stdin) == nbytes);
  
    if (lseek (0, 0, SEEK_CUR) == nbytes)
!     /* An unbuffered stdio, such as BeOS or on uClibc compiled without
!        __STDIO_BUFFERS.  Or stdin is a pipe.  */
!     ASSERT (freadahead (stdin) == 0);
    else
      {
        /* Normal buffered stdio.  */
        const char stdin_contents[] =
        "#!/bin/sh\n\n./test-freadptr${EXEEXT} 5 < \"$srcdir/test-freadptr.sh\" 
|| exit 1\ncat \"$srcdir/test-freadptr.sh\" | ./test-freadptr${EXEEXT} 5 || 
exit 1\nexit 0\n";
        const char *expected = stdin_contents + nbytes;
!       size_t available;
        size_t available2;
        size_t available3;
  
        /* Test normal behaviour.  */
-       available = freadahead (stdin);
-       ASSERT (available != 0);
-       ASSERT (available <= strlen (expected));
        {
!       const char *ptr = freadptr (stdin);
  
        ASSERT (ptr != NULL);
!       ASSERT (memcmp (ptr, expected, available) == 0);
        }
  
        /* Test behaviour after normal ungetc.  */
        ungetc (fgetc (stdin), stdin);
!       available2 = freadahead (stdin);
!       ASSERT (/* available2 == available - 1 || */ available2 == available);
! #if 0
!       if (available2 == available - 1)
!       {
!         ASSERT (freadptr (stdin) == NULL);
!       }
!       else
! #endif
!       {
!         const char *ptr = freadptr (stdin);
! 
!         ASSERT (ptr != NULL);
!         ASSERT (memcmp (ptr, expected, available) == 0);
!       }
  
        /* Test behaviour after arbitrary ungetc.  */
        fgetc (stdin);
        ungetc ('@', stdin);
!       available3 = freadahead (stdin);
!       ASSERT (available3 == 0 || available3 == 1 || /* available3 == 
available - 1 || */ available3 == available);
!       if (available3 == 0)
!       ;
!       else if (available3 == 1)
!       {
!         const char *ptr = freadptr (stdin);
! 
!         if (ptr != NULL)
!           {
!             ASSERT (ptr[0] == '@');
!           }
!       }
! #if 0
!       else if (available3 == available - 1)
!       {
!         ASSERT (freadptr (stdin) == NULL);
!       }
! #endif
!       else
!       {
!         const char *ptr = freadptr (stdin);
! 
!         if (ptr != NULL)
!           {
!             ASSERT (ptr[0] == '@');
!             ASSERT (memcmp (ptr + 1, expected + 1, available - 1) == 0);
!           }
!       }
      }
  
    return 0;
--- 44,103 ----
    ASSERT (fread (buf, 1, nbytes, stdin) == nbytes);
  
    if (lseek (0, 0, SEEK_CUR) == nbytes)
!     {
!       /* An unbuffered stdio, such as BeOS or on uClibc compiled without
!        __STDIO_BUFFERS.  Or stdin is a pipe.  */
!       size_t size;
!       ASSERT (freadptr (stdin, &size) == NULL);
!     }
    else
      {
        /* Normal buffered stdio.  */
        const char stdin_contents[] =
        "#!/bin/sh\n\n./test-freadptr${EXEEXT} 5 < \"$srcdir/test-freadptr.sh\" 
|| exit 1\ncat \"$srcdir/test-freadptr.sh\" | ./test-freadptr${EXEEXT} 5 || 
exit 1\nexit 0\n";
        const char *expected = stdin_contents + nbytes;
!       size_t available1;
        size_t available2;
        size_t available3;
  
        /* Test normal behaviour.  */
        {
!       const char *ptr = freadptr (stdin, &available1);
  
        ASSERT (ptr != NULL);
!       ASSERT (available1 != 0);
!       ASSERT (available1 <= strlen (expected));
!       ASSERT (memcmp (ptr, expected, available1) == 0);
        }
  
        /* Test behaviour after normal ungetc.  */
        ungetc (fgetc (stdin), stdin);
!       {
!       const char *ptr = freadptr (stdin, &available2);
! 
!       if (ptr != NULL)
!         {
!           ASSERT (available2 == available1);
!           ASSERT (memcmp (ptr, expected, available2) == 0);
!         }
!       }
  
        /* Test behaviour after arbitrary ungetc.  */
        fgetc (stdin);
        ungetc ('@', stdin);
!       {
!       const char *ptr = freadptr (stdin, &available3);
! 
!       if (ptr != NULL)
!         {
!           ASSERT (available3 == 1 || available3 == available1);
!           ASSERT (ptr[0] == '@');
!           if (available3 > 1)
!             {
!               ASSERT (memcmp (ptr + 1, expected + 1, available3 - 1) == 0);
!             }
!         }
!       }
      }
  
    return 0;
*** modules/freadptr-tests.orig 2008-03-10 00:14:43.000000000 +0100
--- modules/freadptr-tests      2008-03-09 23:17:39.000000000 +0100
***************
*** 1,15 ****
  Files:
  tests/test-freadptr.c
  tests/test-freadptr.sh
  
  Depends-on:
  lseek
- freadahead
  unistd
  
  configure.ac:
  
  Makefile.am:
! TESTS += test-freadptr.sh
  TESTS_ENVIRONMENT += EXEEXT='@EXEEXT@' srcdir='$(srcdir)'
! check_PROGRAMS += test-freadptr
--- 1,16 ----
  Files:
  tests/test-freadptr.c
  tests/test-freadptr.sh
+ tests/test-freadptr2.c
+ tests/test-freadptr2.sh
  
  Depends-on:
  lseek
  unistd
  
  configure.ac:
  
  Makefile.am:
! TESTS += test-freadptr.sh test-freadptr2.sh
  TESTS_ENVIRONMENT += EXEEXT='@EXEEXT@' srcdir='$(srcdir)'
! check_PROGRAMS += test-freadptr test-freadptr2
======================== tests/test-freadptr2.c ==============================
/* Test of freadptr() function.
   Copyright (C) 2007-2008 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <address@hidden>, 2007.  */

#include <config.h>

#include "freadptr.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define ASSERT(expr) \
  do                                                                         \
    {                                                                        \
      if (!(expr))                                                           \
        {                                                                    \
          fprintf (stderr, "%s:%d: assertion failed\n", __FILE__, __LINE__); \
          abort ();                                                          \
        }                                                                    \
    }                                                                        \
  while (0)

static int
freadptrbufsize (FILE *fp)
{
  size_t size = 0;

  freadptr (fp, &size);
  return size;
}

int
main (int argc, char **argv)
{
  int nbytes = atoi (argv[1]);
  if (nbytes > 0)
    {
      void *buf = malloc (nbytes);
      ASSERT (fread (buf, 1, nbytes, stdin) == nbytes);
    }

  if (nbytes == 0)
    ASSERT (freadptrbufsize (stdin) == 0);
  else
    {
      if (lseek (0, 0, SEEK_CUR) == nbytes)
        /* An unbuffered stdio, such as BeOS or on uClibc compiled without
           __STDIO_BUFFERS.  */
        ASSERT (freadptrbufsize (stdin) == 0);
      else
        /* Normal buffered stdio.  */
        ASSERT (freadptrbufsize (stdin) != 0);
    }

  return 0;
}
======================== tests/test-freadptr2.sh =============================
#!/bin/sh

./test-freadptr2${EXEEXT} 0 < "$srcdir/test-freadptr2.sh" || exit 1
./test-freadptr2${EXEEXT} 5 < "$srcdir/test-freadptr2.sh" || exit 1
exit 0