/**************************************************************************** * libc/stdio/lib_setvbuf.c * * Copyright (C) 2017 Gregory Nutt. All rights reserved. * Author: Alan Carvalho de Assis * Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT will THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include "libc.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: setvbuf * * Description: * The setvbuf() function may be used after the stream pointed to by * stream is associated with an open file but before any other operation * (other than an unsuccessful call to setvbuf()) is performed on the * stream. The argument type determines how stream will be buffered, as * follows: * * _IOFBF - Will cause input/output to be fully buffered. * _IOLBF - Will cause input/output to be line buffered. * _IONBF - Will cause input/output to be unbuffered. * * If buf is not a null pointer, the array it points to may be used instead * of a buffer allocated by setvbuf() and the argument size specifies the size * of the array; otherwise, size may determine the size of a buffer allocated * by the setvbuf() function. The contents of the array at any time are * unspecified. * * Input Parameters: * stream - the stream to flush * buffer - the user allocate buffer. If NULL, will allocates a buffer of * specified size * mode - specifies a mode for file buffering * size - size of buffer * * Returned Value: * Upon successful completion, setvbuf() will return 0. Otherwise, it will * return a non-zero value if an invalid value is given for type or if the * request cannot be honored, [CX] and may set errno to indicate the error * ****************************************************************************/ int setvbuf(FAR FILE *stream, FAR char *buffer, int mode, size_t size) { #ifndef CONFIG_STDIO_DISABLE_BUFFERING FAR unsigned char *newbuf; uint8_t flags; int errcode; /* Verify arguments */ /* Make sure that a valid mode was provided */ if (mode != _IOFBF && mode != _IOLBF && mode != _IONBF) { errcode = EINVAL; goto errout; } /* If a buffer pointer is provided, then it must have a non-zero size */ if (buffer != NULL && size == 0) { errcode = EINVAL; goto errout; } /* My assumption is that if size is zero for modes {_IOFBF, _IOLBF} the * caller is only attempting to change the buffering mode. In this case, * the existing buffer should be re-used (if there is one). If there is no * existing buffer, then I suppose we should allocate one of the default * size? */ if ((mode == _IOFBF || mode == _IOLBF) && size == 0 && stream->fs_bufstart == NULL) { size = BUFSIZ; } /* A non-zero size (or a non-NULL buffer) with mode = _IONBF makes no * sense but is, apparently, permissible. We simply force the buffer to * NULL and size to zero in this case without complaining. */ else if (mode == _IONBF) { buffer = NULL; size = 0; } /* Make sure that we have exclusive access to the stream */ lib_take_semaphore(stream); /* setvbuf() may only be called AFTER the file has been opened and BEFORE * any operations have been performed on the string. */ /* Return EBADF if the file is not open */ if (stream->fs_fd < 0) { errcode = EBADF; goto errout_with_semaphore; } /* Return EBUSY if operations have already been performed on the buffer. * Here we really only verify that there is no valid data in the existing * buffer. * * REVIST: There could be race conditions here, could there not? */ if (stream->fs_bufpos != stream->fs_bufstart) { errcode = EBUSY; goto errout_with_semaphore; } /* Initialize by clearing related flags. We try to avoid any permanent * changes to the stream structure until we know that we will be * successful. */ flags = stream->fs_flags & ~(__FS_FLAG_LBF | __FS_FLAG_UBF); /* Allocate a new buffer if one is needed or reuse the existing buffer it * is appropriate to do so. */ switch (mode) { case _IOLBF: flags |= __FS_FLAG_LBF; /* Fall through */ case _IOFBF: /* Use the existing buffer if size == 0 */ if (size > 0) { /* A new buffer is needed. Did the caller provide the buffer * memory? */ if (buffer != NULL) { newbuf = (FAR unsigned char *)buffer; /* Indicate that we have an I/O buffer managed by the caller of * setvbuf. */ flags |= __FS_FLAG_UBF; } else { newbuf = (FAR unsigned char *)lib_malloc(size); if (newbuf == NULL) { errcode = ENOMEM; goto errout_with_semaphore; } } } else { /* Re-use the existing buffer and retain some existing flags. * This supports changing the buffering mode without changing * the buffer. */ DEBUGASSERT(stream->fs_bufstart != NULL); flags |= stream->fs_flags & __FS_FLAG_UBF; goto reuse_buffer; } break; case _IONBF: /* No buffer needed... We must be performing unbuffered I/O */ newbuf = NULL; break; default: PANIC(); } /* Do not release the previous buffer if it was allocated by the user * on a previous call to setvbuf(). */ if (stream->fs_bufstart != NULL && (stream->fs_flags & __FS_FLAG_UBF) == 0) { lib_free(stream->fs_bufstart); } /* Set the new buffer information */ stream->fs_bufstart = newbuf; stream->fs_bufpos = newbuf; stream->fs_bufread = newbuf; stream->fs_bufend = newbuf + size; /* Update the stream flags and return success */ reuse_buffer: stream->fs_flags = flags; lib_give_semaphore(stream); return OK; errout_with_semaphore: lib_give_semaphore(stream); errout: set_errno(errcode); return ERROR; #else /* Return that setvbuf() is not supported */ set_errno(ENOSYS); return ERROR; #endif }