/* $NetBSD: forward.c,v 1.25 2003/08/07 11:16:01 agc Exp $ */ /*- * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Edward Sze-Tyan Wang. * * 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 of the University 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 REGENTS 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 REGENTS 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. */ #include #ifndef lint #if 0 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; #endif __RCSID("$NetBSD: forward.c,v 1.25 2003/08/07 11:16:01 agc Exp $"); #endif /* not lint */ #include #include #include #include #include #include #include #include #include #include #include #include #include "extern.h" static int rlines(FILE *, long, struct stat *); /* defines for inner loop actions */ #define USE_SLEEP 0 #define USE_KQUEUE 1 #define ADD_EVENTS 2 /* * forward -- display the file, from an offset, forward. * * There are eight separate cases for this -- regular and non-regular * files, by bytes or lines and from the beginning or end of the file. * * FBYTES byte offset from the beginning of the file * REG seek * NOREG read, counting bytes * * FLINES line offset from the beginning of the file * REG read, counting lines * NOREG read, counting lines * * RBYTES byte offset from the end of the file * REG seek * NOREG cyclically read characters into a wrap-around buffer * * RLINES * REG mmap the file and step back until reach the correct offset. * NOREG cyclically read lines into a wrap-around array of buffers */ void forward(FILE *fp, enum STYLE style, long int off, struct stat *sbp) { int ch, n; int kq=-1, action=USE_SLEEP; struct stat statbuf; dev_t lastdev; ino_t lastino; struct kevent ev[2]; /* Keep track of file's previous incarnation. */ lastdev = sbp->st_dev; lastino = sbp->st_ino; switch(style) { case FBYTES: if (off == 0) break; if (S_ISREG(sbp->st_mode)) { if (sbp->st_size < off) off = sbp->st_size; if (fseek(fp, off, SEEK_SET) == -1) { ierr(); return; } } else while (off--) if ((ch = getc(fp)) == EOF) { if (ferror(fp)) { ierr(); return; } break; } break; case FLINES: if (off == 0) break; for (;;) { if ((ch = getc(fp)) == EOF) { if (ferror(fp)) { ierr(); return; } break; } if (ch == '\n' && !--off) break; } break; case RBYTES: if (S_ISREG(sbp->st_mode)) { if (sbp->st_size >= off && fseek(fp, -off, SEEK_END) == -1) { ierr(); return; } } else if (off == 0) { while (getc(fp) != EOF); if (ferror(fp)) { ierr(); return; } } else { if (bytes(fp, off)) return; } break; case RLINES: if (S_ISREG(sbp->st_mode)) { if (!off) { if (fseek(fp, 0L, SEEK_END) == -1) { ierr(); return; } } else { if (rlines(fp, off, sbp)) return; } } else if (off == 0) { while (getc(fp) != EOF); if (ferror(fp)) { ierr(); return; } } else { if (lines(fp, off)) return; } break; default: break; } if (fflag) { kq = kqueue(); if (kq < 0) err(1, "kqueue"); action = ADD_EVENTS; } for (;;) { while ((ch = getc(fp)) != EOF) { if (putchar(ch) == EOF) oerr(); } if (ferror(fp)) { ierr(); return; } (void)fflush(stdout); if (!fflag) break; clearerr(fp); switch (action) { case ADD_EVENTS: n = 0; memset(ev, 0, sizeof(ev)); if (fflag == 2 && fileno(fp) != STDIN_FILENO) { EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, EV_ADD | EV_ENABLE | EV_CLEAR, NOTE_DELETE | NOTE_RENAME, 0, 0); n++; } EV_SET(&ev[n], fileno(fp), EVFILT_READ, EV_ADD | EV_ENABLE, 0, 0, 0); n++; if (kevent(kq, ev, n, NULL, 0, NULL) < 0) { close(kq); kq = -1; action = USE_SLEEP; } else { action = USE_KQUEUE; } break; case USE_KQUEUE: if (kevent(kq, NULL, 0, ev, 1, NULL) < 0) err(1, "kevent"); if (ev[0].filter == EVFILT_VNODE) { /* file was rotated, wait until it reappears */ action = USE_SLEEP; } else if (ev[0].data < 0) { /* file shrank, reposition to end */ if (fseek(fp, 0L, SEEK_END) == -1) { ierr(); return; } } break; case USE_SLEEP: /* * We pause for one second after displaying any data * that has accumulated since we read the file. */ (void) sleep(1); if (fflag == 2 && fileno(fp) != STDIN_FILENO && stat(fname, &statbuf) != -1) { if (statbuf.st_ino != sbp->st_ino || statbuf.st_dev != sbp->st_dev || statbuf.st_rdev != sbp->st_rdev || statbuf.st_nlink == 0) { fp = freopen(fname, "r", fp); if (fp == NULL) { ierr(); break; } *sbp = statbuf; if (kq != -1) action = ADD_EVENTS; } else if (kq != -1) action = USE_KQUEUE; } break; } } if (fflag && kq != -1) close(kq); } /* * rlines -- display the last offset lines of the file. * * Non-zero return means than a (non-fatal) error occurred. */ static int rlines(FILE *fp, long int off, struct stat *sbp) { off_t file_size; off_t file_remaining; char *p; char *start; off_t mmap_size; off_t mmap_offset; off_t mmap_remaining; #define MMAP_MAXSIZE (10 * 1024 * 1024) if (!(file_size = sbp->st_size)) return (0); file_remaining = file_size; if (file_remaining > MMAP_MAXSIZE) { mmap_size = MMAP_MAXSIZE; mmap_offset = file_remaining - MMAP_MAXSIZE; } else { mmap_size = file_remaining; mmap_offset = 0; } while (off) { start = mmap(NULL, (size_t)mmap_size, PROT_READ, MAP_FILE|MAP_SHARED, fileno(fp), mmap_offset); if (start == MAP_FAILED) { err(0, "%s: %s", fname, strerror(EFBIG)); return (1); } mmap_remaining = mmap_size; /* Last char is special, ignore whether newline or not. */ for (p = start + mmap_remaining - 1 ; --mmap_remaining ; ) if (*--p == '\n' && !--off) { ++p; break; } file_remaining -= mmap_size - mmap_remaining; if (off == 0) break; if (file_remaining == 0) break; if (munmap(start, mmap_size)) { err(0, "%s: %s", fname, strerror(errno)); return (1); } if (mmap_offset >= MMAP_MAXSIZE) { mmap_offset -= MMAP_MAXSIZE; } else { mmap_offset = 0; mmap_size = file_remaining; } } /* * Output the (perhaps partial) data in this mmap'd block. */ WR(p, mmap_size - mmap_remaining); file_remaining += mmap_size - mmap_remaining; if (munmap(start, mmap_size)) { err(0, "%s: %s", fname, strerror(errno)); return (1); } /* * Set the file pointer to reflect the length displayed. * This will cause the caller to redisplay the data if/when * needed. */ if (fseeko(fp, file_remaining, SEEK_SET) == -1) { ierr(); return (1); } return (0); }