From 758f820bcc0f68aeebac1717e537ca13a320b909 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 18:11:47 +0200 Subject: Adding upstream version 9.1. Signed-off-by: Daniel Baumann --- lib/freadseek.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 145 insertions(+) create mode 100644 lib/freadseek.c (limited to 'lib/freadseek.c') diff --git a/lib/freadseek.c b/lib/freadseek.c new file mode 100644 index 0000000..2e0c0a2 --- /dev/null +++ b/lib/freadseek.c @@ -0,0 +1,145 @@ +/* Skipping input from a FILE stream. + Copyright (C) 2007-2022 Free Software Foundation, Inc. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + This file 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 Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see . */ + +#include + +/* Specification. */ +#include "freadseek.h" + +#include +#include + +#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 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_EOF_SEEN || defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 + /* GNU libc, BeOS, Haiku, Linux libc5 */ + fp->_IO_read_ptr += increment; +#elif defined __sferror || defined __DragonFly__ || defined __ANDROID__ + /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Minix 3, Android */ + 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, UnixWare, mingw, MSVC, NonStop Kernel, OpenVMS */ + 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 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; + + /* 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; +} -- cgit v1.2.3