Changes between Version 80 and Version 81 of library_stdio

Timestamp:

Jun 11, 2015, 7:52:02 PM (9 years ago)

Author:

alain

Comment:

--

library_stdio

@@ -165 +165 @@
  ==  __File system related system calls__ ==
 
-The Giet-VM supports a FAT32 file system.
-
- === 1) int '''giet_fat_open'''( const char* pathname, unsigned int flags ) ===
-This function open a file identified by the ''pathname'' argument. The read/write ''flags''  are not supported yet: no effect. Return -1 in case or error.
-
- === 2) void '''giet_fat_read'''( unsigned int fd, void* buffer, unsigned int count, unsigned int offset ) ===
-Read ''count'' sectors from a file identified by the ''fd'' argument, skipping ''offset'' sectors in file, and writing into the user memory ''buffer''. The user buffer base address should be 64 bytes aligned.
-In case or error, it makes a giet_exit().
-
- === 3) void '''giet_fat_write'''( unsigned int fd, void* buffer, unsigned int count, unsigned int offset ) ===
-Write ''count'' sectors into a file identified by the ''fd'' argument, skipping ''offset'' sectors in file, and reading from the user memory ''buffer''. The user buffer base address should be 64 bytes aligned.
-In case or error, it makes a giet_exit().
-
- === 4) void '''giet_fat_close'''( unsigned int fd ) ===
-Close a file identified by the ''fd'' file descriptor.
-
+The Giet-VM supports a FAT32 file system, and uses distributed data structures to access the file system:
+ * The Inode-Tree (distributed on all clusters) is the internal representation of the File System tree.
+ * The Fat-Cache (distributed on all clusters) is used to cache the FAT region of the block device.
+ * The Fat-Cache (distributed on all clusters / one cache per open file) is used to cache the DATA region of the block device.
+ * The File-Descriptor-Array (in cluster[0,0]) contains the open files descriptors.
+ * The Fat-Descriptor (in cluster[0,0] contains the FAT32 general information.
+
+=== 1) int '''giet_fat_open'''( char* pathname ) ===
+This function allocates a file descriptor to the calling task, for the file identified by its absolute "pathname". 
+If several tasks try to open the same file, each task obtains a private file descriptor.
+The semantic is similar to the UNIX open() function, but the UNIX oflags and the UNIX access rights are not supported. 
+If the file does not exist in the specified directory, it is created.
+If the specified directory does not exist, an error is returned.
+
+WARNING: A node name (file or directory) cannot be larger than 30 characters. 
+
+Returns the file descriptor index if success
+Returns  -1 if error.
+
+=== 2)  '''void giet_fat_close'''( unsigned int fd_id ) ===
+Close a file identified by the ''fd_id'' file descriptor.
+It decrements the reference count in the inode associated to the file, and release the fd_id entry in the file descriptors array.
+If the reference count is zero, it writes all dirty clusters on block device, and releases the memory allocated to the file_cache.
+
+=== 3) '''void get_fat_file_info'''( unsigned int fd_id , unsigned int* size , unsigned int* offset ) ===
+This function returns the "size" and the current "offset" value for a file identified  by the "fd_id" argument. 
+
+=== 4) int '''giet_fat_read'''( unsigned int fd_id , void* buffer , unsigned int count ) ===
+This function has the same semantic as the UNIX "read()" function. It transfers "count" bytes from the kernel File_Cache associated to the file identified by "fd_id", to the user "buffer", starting from the current file offset. The offset value is incremented by count.
+In case of miss in the File_Cache, it loads all involved clusters into cache.
+
+Returns number of bytes actually transferred if success.
+Returns 0 if (offset + count) is larger than the file size. 
+Returns -1 if error.
+
+ === 5) int '''giet_fat_write'''( unsigned int fd_id , void* buffer, unsigned int count ) ===
+This function has the same semantic as the UNIX "write()" function. It transfers "count" bytes from the user "buffer" to the kernel File_Cache associated to the file identified by "fd_id", starting from the current file offset. The offset value is incremented by count. It increases the file size and allocate new clusters if (count + offset) is larger than the current file size. Then it loads and updates all involved clusters in the cache.
+The FAT region on block device is updated if new clusters are allocated, but the block device DATA region is NOT updated.
+
+Returns number of bytes actually transferred if success.
+Returns -1 if error.
+
+=== int '''giet_fat_lseek'''( unsigned int fd_id , unsigned int offset , unsigned int whence ) ===
+This function has the same semantic as the UNIX lseek() function.
+It repositions the offset in the file descriptor "fd_id", according to the "offset" and "whence" arguments.
+The two accepted values for the whence argument are SEEK_SET (new_offset <= offset), and SEEK_CUR (new_offset <= current_offset + offset).
+
+Returns new offset value (bytes) if success.
+Returns -1 if error.
+
+=== int '''giet_fat_rm'''( char* pathname ) ===
+This function has the same semantic as the UNIX unlink() function.
+It deletes a file identified by the absolute "pathname" argument from the sile system.
+AN error is reported if the references count (number of open file descriptor) is not zero.
+All clusters allocated to this file in the block device DATA region are released.
+The Inode-Tree is updated.
+the Fat-Cache is updated, and the FAT region is updated on the block device. 
+The memory allocated for the associated File_Cache is released.
+
+Returns 0 if success.
+Returns -1 if error.
+
+=== int '''get_fat_mkdir( char* pathname ) ===
+This function has the same semantic as the UNIX mkdir() function.
+It creates in the file system the directory specified by the absolute "pathname" argument.  
+The Inode-Tree is updated.
+One cluster is allocated to the new directory, containing the "." and ".." entries.
+The associated File-Cache is created.
+The Fat-Cache is updated, and the FAT region on block device is updated.
+The DATA region on block device is updated.
+
+Returns 0 if success.
+Returns -1 if error.
+
+=== void '''get_fat_rmdir'''( char* pathname ) ===
+This function has the same semantic as the UNIX mkdir() function.
+It deletes the directory specified by the absolute "pathname" argument from the file system.
+The Fat-Cache is updated, and the FAT region on block device is updated.
+The Inode-Tree is updated.
+The memory allocated to the File-Cache is released.
+
+Returns 0 if success.
+Returns -1 if error.
 
  == __Network related system call__ ==