diff options
Diffstat (limited to 'nuttx/fs/mmap/fs_rammap.c')
-rw-r--r-- | nuttx/fs/mmap/fs_rammap.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/nuttx/fs/mmap/fs_rammap.c b/nuttx/fs/mmap/fs_rammap.c new file mode 100644 index 000000000..0eaf313b5 --- /dev/null +++ b/nuttx/fs/mmap/fs_rammap.c @@ -0,0 +1,238 @@ +/**************************************************************************** + * fs/mmap/fs_rammmap.c + * + * Copyright (C) 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * 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 SHALL 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 <nuttx/config.h> + +#include <sys/types.h> +#include <sys/mman.h> + +#include <string.h> +#include <unistd.h> +#include <errno.h> +#include <debug.h> + +#include <nuttx/kmalloc.h> + +#include "fs_internal.h" +#include "fs_rammap.h" + +#ifdef CONFIG_FS_RAMMAP + +/**************************************************************************** + * Global Data + ****************************************************************************/ + +/* This is the list of all mapped files */ + +struct fs_allmaps_s g_rammaps; + +/**************************************************************************** + * Global Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: rammap_initialize + * + * Description: + * Verified that this capability has been initialized. + * + * Input Parameters: + * None + * + * Returned Value: + * None + * + ****************************************************************************/ + +void rammap_initialize(void) +{ + if (!g_rammaps.initialized) + { + sem_init(&g_rammaps.exclsem, 0, 1); + g_rammaps.initialized = true; + } +} + +/**************************************************************************** + * Name: rammmap + * + * Description: + * Support simulation of memory mapped files by copying files into RAM. + * + * Parameters: + * fd file descriptor of the backing file -- required. + * length The length of the mapping. For exception #1 above, this length + * ignored: The entire underlying media is always accessible. + * offset The offset into the file to map + * + * Returned Value: + * On success, rammmap() returns a pointer to the mapped area. On error, the + * value MAP_FAILED is returned, and errno is set appropriately. + * + * EBADF + * 'fd' is not a valid file descriptor. + * EINVAL + * 'length' or 'offset' are invalid + * ENOMEM + * Insufficient memory is available to map the file. + * + ****************************************************************************/ + +FAR void *rammap(int fd, size_t length, off_t offset) +{ + FAR struct fs_rammap_s *map; + FAR uint8_t *alloc; + FAR uint8_t *rdbuffer; + ssize_t nread; + off_t fpos; + int err; + int ret; + + /* There is a major design flaw that I have not yet thought of fix for: + * The goal is to have a single region of memory that represents a single + * file and can be shared by many threads. That is, given a filename a + * thread should be able to open the file, get a file descriptor, and + * call mmap() to get a memory region. Different file descriptors opened + * with the same file path should get the same memory region when mapped. + * + * The design flaw is that I don't have sufficient knowledge to know that + * these different file descriptors map to the same file. So, for the time + * being, a new memory region is created each time that rammap() is called. + * Not very useful! + */ + + /* Allocate a region of memory of the specified size */ + + alloc = (FAR uint8_t *)kmalloc(sizeof(struct fs_rammap_s) + length); + if (!alloc) + { + fdbg("Region allocation failed, length: %d\n", (int)length); + err = ENOMEM; + goto errout; + } + + /* Initialize the region */ + + map = (FAR struct fs_rammap_s *)alloc; + memset(map, 0, sizeof(struct fs_rammap_s)); + map->addr = alloc + sizeof(struct fs_rammap_s); + map->length = length; + map->offset = offset; + + /* Seek to the specified file offset */ + + fpos = lseek(fd, offset, SEEK_SET); + if (fpos == (off_t)-1) + { + /* Seek failed... errno has already been set, but EINVAL is probably + * the correct response. + */ + + fdbg("Seek to position %d failed\n", (int)offset); + err = ENOMEM; + goto errout_with_region; + } + + /* Read the file data into the memory region */ + + rdbuffer = map->addr; + while (length > 0) + { + nread = read(fd, rdbuffer, length); + if (nread < 0) + { + /* Handle the special case where the read was interrupted by a + * signal. + */ + + if (nread != EINTR) + { + /* All other read errors are bad. errno is already set. + * (but maybe should be forced to EINVAL?) + */ + + fdbg("Read failed: %d\n", (int)offset); + goto errout_with_errno; + } + + /* Check for end of file. */ + + if (nread == 0) + { + break; + } + + /* Increment number of bytes read */ + + rdbuffer += nread; + length -= nread; + } + } + + /* Zero any memory beyond the amount read from the file */ + + memset(rdbuffer, 0, length); + + /* Add the buffer to the list of regions */ + + rammap_initialize(); + ret = sem_wait(&g_rammaps.exclsem); + if (ret < 0) + { + goto errout_with_errno; + } + + map->flink = g_rammaps.head; + g_rammaps.head = map; + + sem_post(&g_rammaps.exclsem); + return map->addr; + +errout_with_region: + kfree(alloc); +errout: + errno = err; + return MAP_FAILED; + +errout_with_errno: + kfree(alloc); + return MAP_FAILED; +} + +#endif /* CONFIG_FS_RAMMAP */ |