VxFS provides an enhanced API to simplify reading and parsing the FCL file in two ways:
The following sample code fragment reads the FCL superblock, checks that the state of the FCL is VX_FCLS_ON, issues a call to vxfs_fcl_sync to obtain a finishing offset to read to, determines the first valid offset in the FCL file, then reads the entries in 8K chunks from this offset. The section process fcl entries is what an application developer must supply to process the entries in the FCL file.
#include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/fcntl.h> #include <errno.h> #include <fcl.h> #include <vxfsutil.h> #define FCL_READSZ 8192 char* fclname = "/mnt/lost+found/changelog"; int read_fcl(fclname) char* fclname; { struct fcl_sb fclsb; uint64_t off, lastoff; size_t size; char buf[FCL_READSZ], *bufp = buf; int fd; int err = 0; if ((fd = open(fclname, O_RDONLY)) < 0) { return ENOENT; } if ((off = lseek(fd, 0, SEEK_SET)) != 0) { close(fd); return EIO; } size = read(fd, &fclsb, sizeof (struct fcl_sb)); if (size < 0) { close(fd); return EIO; } if (fclsb.fc_state == VX_FCLS_OFF) { close(fd); return 0; } if (err = vxfs_fcl_sync(fclname, &lastoff)) { close(fd); return err; } if ((off = lseek(fd, off_t, uint64_t)) != uint64_t) { close(fd); return EIO; } while (off < lastoff) { if ((size = read(fd, bufp, FCL_READSZ)) <= 0) { close(fd); return errno; } /* process fcl entries */ off += size; } close(fd); return 0; }