/* Skipping input from a FILE stream.
- Copyright (C) 2007-2008 Free Software Foundation, Inc.
+ Copyright (C) 2007-2014 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
#include <unistd.h>
#include "freadahead.h"
+#include "freadptr.h"
-int
-freadseek (FILE *fp, size_t offset)
-{
- size_t buffered;
- int fd;
-
- if (offset == 0)
- return 0;
+#include "stdio-impl.h"
- /* Increment the in-memory pointer. This is very cheap (no system calls). */
- buffered = freadahead (fp);
- if (buffered > 0)
- {
- size_t increment = (buffered < offset ? buffered : offset);
-
- /* Keep this code in sync with freadahead and freadptr! */
-#if defined _IO_ferror_unlocked /* GNU libc, BeOS */
- fp->_IO_read_ptr += increment;
-#elif defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
- fp->_p += increment;
- fp->_r -= increment;
-#elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw */
-# if defined __sun && defined _LP64 /* Solaris/{SPARC,AMD64} 64-bit */
-# define fp_ ((struct { unsigned char *_ptr; \
- unsigned char *_base; \
- unsigned char *_end; \
- long _cnt; \
- int _file; \
- unsigned int _flag; \
- } *) fp)
- fp_->_ptr += increment;
- fp_->_cnt -= increment;
-# else
- fp->_ptr += increment;
- fp->_cnt -= increment;
-# endif
+/* Increment the in-memory pointer. INCREMENT must be at most the buffer size
+ returned by freadptr().
+ This is very cheap (no system calls). */
+static void
+freadptrinc (FILE *fp, size_t increment)
+{
+ /* Keep this code in sync with freadptr! */
+#if HAVE___FREADPTRINC /* musl libc */
+ __freadptrinc (fp, increment);
+#elif defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+ fp->_IO_read_ptr += increment;
+#elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin */
+ fp_->_p += increment;
+ fp_->_r -= increment;
+#elif defined __EMX__ /* emx+gcc */
+ fp->_ptr += increment;
+ fp->_rcount -= increment;
+#elif defined __minix /* Minix */
+ fp_->_ptr += increment;
+ fp_->_count -= increment;
+#elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, NonStop Kernel */
+ fp_->_ptr += increment;
+ fp_->_cnt -= increment;
#elif defined __UCLIBC__ /* uClibc */
# ifdef __STDIO_BUFFERS
- fp->__bufpos += increment;
+ fp->__bufpos += increment;
# else
- abort ();
+ abort ();
# endif
#elif defined __QNX__ /* QNX */
- fp->_Next += increment;
+ fp->_Next += increment;
+#elif defined __MINT__ /* Atari FreeMiNT */
+ fp->__bufp += increment;
+#elif defined EPLAN9 /* Plan9 */
+ fp->rp += increment;
+#elif defined SLOW_BUT_NO_HACKS /* users can define this */
#else
#error "Please port gnulib freadseek.c to your platform! Look at the definition of getc, getc_unlocked on your system, then report this to bug-gnulib."
#endif
+}
+
+int
+freadseek (FILE *fp, size_t offset)
+{
+ size_t total_buffered;
+ int fd;
+
+ if (offset == 0)
+ return 0;
- offset -= increment;
+ /* Seek over the already read and buffered input as quickly as possible,
+ without doing any system calls. */
+ total_buffered = freadahead (fp);
+ /* This loop is usually executed at most twice: once for ungetc buffer (if
+ present) and once for the main buffer. */
+ while (total_buffered > 0)
+ {
+ size_t buffered;
+
+ if (freadptr (fp, &buffered) != NULL && buffered > 0)
+ {
+ size_t increment = (buffered < offset ? buffered : offset);
+
+ freadptrinc (fp, increment);
+ offset -= increment;
+ if (offset == 0)
+ return 0;
+ total_buffered -= increment;
+ if (total_buffered == 0)
+ break;
+ }
+ /* Read one byte. If we were reading from the ungetc buffer, this
+ switches the stream back to the main buffer. */
+ if (fgetc (fp) == EOF)
+ goto eof;
+ offset--;
if (offset == 0)
- return 0;
+ return 0;
+ total_buffered--;
}
/* Test whether the stream is seekable or not. */
if (fd >= 0 && lseek (fd, 0, SEEK_CUR) >= 0)
{
/* FP refers to a regular file. fseek is most efficient in this case. */
- return fseek (fp, offset, SEEK_CUR);
+ return fseeko (fp, offset, SEEK_CUR);
}
else
{
/* FP is a non-seekable stream, possibly not even referring to a file
- descriptor. Read OFFSET bytes explicitly and discard them. */
+ descriptor. Read OFFSET bytes explicitly and discard them. */
char buf[4096];
do
- {
- size_t count = (sizeof (buf) < offset ? sizeof (buf) : offset);
- if (fread (buf, 1, count, fp) < count)
- {
- if (ferror (fp))
- /* EOF, or error before or while reading. */
- return EOF;
- else
- /* Encountered EOF. */
- return 0;
- }
- offset -= count;
- }
+ {
+ size_t count = (sizeof (buf) < offset ? sizeof (buf) : offset);
+ if (fread (buf, 1, count, fp) < count)
+ goto eof;
+ offset -= count;
+ }
while (offset > 0);
return 0;
}
+
+ eof:
+ /* EOF, or error before or while reading. */
+ if (ferror (fp))
+ return EOF;
+ else
+ /* Encountered EOF. */
+ return 0;
}
projects / gnulib.git / blobdiff