diff options
Diffstat (limited to 'gnulib/lib/freadseek.c')
m--------- | gnulib | 0 | ||||
-rw-r--r-- | gnulib/lib/freadseek.c | 139 |
2 files changed, 139 insertions, 0 deletions
diff --git a/gnulib b/gnulib deleted file mode 160000 -Subproject 443bc5ffcf7429e557f4a371b0661abe98ddbc1 diff --git a/gnulib/lib/freadseek.c b/gnulib/lib/freadseek.c new file mode 100644 index 0000000..4fbad2d --- /dev/null +++ b/gnulib/lib/freadseek.c @@ -0,0 +1,139 @@ +/* Skipping input from a FILE stream. + Copyright (C) 2007-2011 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/>. */ + +#include <config.h> + +/* Specification. */ +#include "freadseek.h" + +#include <stdlib.h> +#include <unistd.h> + +#include "freadahead.h" +#include "freadptr.h" + +#include "stdio-impl.h" + +/* Increment the in-memory pointer. INCREMENT must be at most the buffer size + returned by freadptr(). + This is very cheap (no system calls). */ +static inline void +freadptrinc (FILE *fp, size_t increment) +{ + /* Keep this code in sync with freadptr! */ +#if 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, MacOS 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; +# else + abort (); +# endif +#elif defined __QNX__ /* QNX */ + fp->_Next += increment; +#elif defined __MINT__ /* Atari FreeMiNT */ + fp->__bufp += 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; + + /* 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; + total_buffered--; + } + + /* Test whether the stream is seekable or not. */ + fd = fileno (fp); + if (fd >= 0 && lseek (fd, 0, SEEK_CUR) >= 0) + { + /* FP refers to a regular file. fseek is most efficient in this case. */ + 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. */ + char buf[4096]; + + do + { + 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; +} |