लिनक्स/linux-0.01.tar/fs/file dev.c
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< लिनक्स | linux-0.01.tar
#include <errno.h> #include <fcntl.h> #include <linux/sched.h> #include <linux/kernel.h> #include <asm/segment.h> #define MIN(a,b) (((a)<(b))?(a):(b)) #define MAX(a,b) (((a)>(b))?(a):(b)) int file_read(struct m_inode * inode, struct file * filp, char * buf, int count) { int left,chars,nr; struct buffer_head * bh; if ((left=count)<=0) return 0; while (left) { if (nr = bmap(inode,(filp->f_pos)/BLOCK_SIZE)) { if (!(bh=bread(inode->i_dev,nr))) break; } else bh = NULL; nr = filp->f_pos % BLOCK_SIZE; chars = MIN( BLOCK_SIZE-nr , left ); filp->f_pos += chars; left -= chars; if (bh) { char * p = nr + bh->b_data; while (chars-->0) put_fs_byte(*(p++),buf++); brelse(bh); } else { while (chars-->0) put_fs_byte(0,buf++); } } inode->i_atime = CURRENT_TIME; return (count-left)?(count-left):-ERROR; } int file_write(struct m_inode * inode, struct file * filp, char * buf, int count) { off_t pos; int block,c; struct buffer_head * bh; char * p; int i=0; /* * ok, append may not work when many processes are writing at the same time * but so what. That way leads to madness anyway. */ if (filp->f_flags & O_APPEND) pos = inode->i_size; else pos = filp->f_pos; while (i<count) { if (!(block = create_block(inode,pos/BLOCK_SIZE))) break; if (!(bh=bread(inode->i_dev,block))) break; c = pos % BLOCK_SIZE; p = c + bh->b_data; bh->b_dirt = 1; c = BLOCK_SIZE-c; if (c > count-i) c = count-i; pos += c; if (pos > inode->i_size) { inode->i_size = pos; inode->i_dirt = 1; } i += c; while (c-->0) *(p++) = get_fs_byte(buf++); brelse(bh); } inode->i_mtime = CURRENT_TIME; if (!(filp->f_flags & O_APPEND)) { filp->f_pos = pos; inode->i_ctime = CURRENT_TIME; } return (i?i:-1); }