Annotation of src/usr.bin/tail/forward.c, Revision 1.1
1.1 ! deraadt 1: /* $NetBSD: forward.c,v 1.6 1994/11/23 07:42:02 jtc Exp $ */
! 2:
! 3: /*-
! 4: * Copyright (c) 1991, 1993
! 5: * The Regents of the University of California. All rights reserved.
! 6: *
! 7: * This code is derived from software contributed to Berkeley by
! 8: * Edward Sze-Tyan Wang.
! 9: *
! 10: * Redistribution and use in source and binary forms, with or without
! 11: * modification, are permitted provided that the following conditions
! 12: * are met:
! 13: * 1. Redistributions of source code must retain the above copyright
! 14: * notice, this list of conditions and the following disclaimer.
! 15: * 2. Redistributions in binary form must reproduce the above copyright
! 16: * notice, this list of conditions and the following disclaimer in the
! 17: * documentation and/or other materials provided with the distribution.
! 18: * 3. All advertising materials mentioning features or use of this software
! 19: * must display the following acknowledgement:
! 20: * This product includes software developed by the University of
! 21: * California, Berkeley and its contributors.
! 22: * 4. Neither the name of the University nor the names of its contributors
! 23: * may be used to endorse or promote products derived from this software
! 24: * without specific prior written permission.
! 25: *
! 26: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 27: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 28: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 29: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 30: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 31: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 32: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 33: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 34: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 35: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 36: * SUCH DAMAGE.
! 37: */
! 38:
! 39: #ifndef lint
! 40: #if 0
! 41: static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93";
! 42: #endif
! 43: static char rcsid[] = "$NetBSD: forward.c,v 1.6 1994/11/23 07:42:02 jtc Exp $";
! 44: #endif /* not lint */
! 45:
! 46: #include <sys/types.h>
! 47: #include <sys/stat.h>
! 48: #include <sys/time.h>
! 49: #include <sys/mman.h>
! 50:
! 51: #include <limits.h>
! 52: #include <fcntl.h>
! 53: #include <errno.h>
! 54: #include <unistd.h>
! 55: #include <stdio.h>
! 56: #include <stdlib.h>
! 57: #include <string.h>
! 58: #include "extern.h"
! 59:
! 60: static void rlines __P((FILE *, long, struct stat *));
! 61:
! 62: /*
! 63: * forward -- display the file, from an offset, forward.
! 64: *
! 65: * There are eight separate cases for this -- regular and non-regular
! 66: * files, by bytes or lines and from the beginning or end of the file.
! 67: *
! 68: * FBYTES byte offset from the beginning of the file
! 69: * REG seek
! 70: * NOREG read, counting bytes
! 71: *
! 72: * FLINES line offset from the beginning of the file
! 73: * REG read, counting lines
! 74: * NOREG read, counting lines
! 75: *
! 76: * RBYTES byte offset from the end of the file
! 77: * REG seek
! 78: * NOREG cyclically read characters into a wrap-around buffer
! 79: *
! 80: * RLINES
! 81: * REG mmap the file and step back until reach the correct offset.
! 82: * NOREG cyclically read lines into a wrap-around array of buffers
! 83: */
! 84: void
! 85: forward(fp, style, off, sbp)
! 86: FILE *fp;
! 87: enum STYLE style;
! 88: long off;
! 89: struct stat *sbp;
! 90: {
! 91: register int ch;
! 92: struct timeval second;
! 93: fd_set zero;
! 94:
! 95: switch(style) {
! 96: case FBYTES:
! 97: if (off == 0)
! 98: break;
! 99: if (S_ISREG(sbp->st_mode)) {
! 100: if (sbp->st_size < off)
! 101: off = sbp->st_size;
! 102: if (fseek(fp, off, SEEK_SET) == -1) {
! 103: ierr();
! 104: return;
! 105: }
! 106: } else while (off--)
! 107: if ((ch = getc(fp)) == EOF) {
! 108: if (ferror(fp)) {
! 109: ierr();
! 110: return;
! 111: }
! 112: break;
! 113: }
! 114: break;
! 115: case FLINES:
! 116: if (off == 0)
! 117: break;
! 118: for (;;) {
! 119: if ((ch = getc(fp)) == EOF) {
! 120: if (ferror(fp)) {
! 121: ierr();
! 122: return;
! 123: }
! 124: break;
! 125: }
! 126: if (ch == '\n' && !--off)
! 127: break;
! 128: }
! 129: break;
! 130: case RBYTES:
! 131: if (S_ISREG(sbp->st_mode)) {
! 132: if (sbp->st_size >= off &&
! 133: fseek(fp, -off, SEEK_END) == -1) {
! 134: ierr();
! 135: return;
! 136: }
! 137: } else if (off == 0) {
! 138: while (getc(fp) != EOF);
! 139: if (ferror(fp)) {
! 140: ierr();
! 141: return;
! 142: }
! 143: } else
! 144: bytes(fp, off);
! 145: break;
! 146: case RLINES:
! 147: if (S_ISREG(sbp->st_mode))
! 148: if (!off) {
! 149: if (fseek(fp, 0L, SEEK_END) == -1) {
! 150: ierr();
! 151: return;
! 152: }
! 153: } else
! 154: rlines(fp, off, sbp);
! 155: else if (off == 0) {
! 156: while (getc(fp) != EOF);
! 157: if (ferror(fp)) {
! 158: ierr();
! 159: return;
! 160: }
! 161: } else
! 162: lines(fp, off);
! 163: break;
! 164: }
! 165:
! 166: /*
! 167: * We pause for one second after displaying any data that has
! 168: * accumulated since we read the file.
! 169: */
! 170: if (fflag) {
! 171: FD_ZERO(&zero);
! 172: second.tv_sec = 1;
! 173: second.tv_usec = 0;
! 174: }
! 175:
! 176: for (;;) {
! 177: while ((ch = getc(fp)) != EOF)
! 178: if (putchar(ch) == EOF)
! 179: oerr();
! 180: if (ferror(fp)) {
! 181: ierr();
! 182: return;
! 183: }
! 184: (void)fflush(stdout);
! 185: if (!fflag)
! 186: break;
! 187: /* Sleep(3) is eight system calls. Do it fast. */
! 188: if (select(0, &zero, &zero, &zero, &second) == -1)
! 189: err(1, "select: %s", strerror(errno));
! 190: clearerr(fp);
! 191: }
! 192: }
! 193:
! 194: /*
! 195: * rlines -- display the last offset lines of the file.
! 196: */
! 197: static void
! 198: rlines(fp, off, sbp)
! 199: FILE *fp;
! 200: long off;
! 201: struct stat *sbp;
! 202: {
! 203: register off_t size;
! 204: register char *p;
! 205: char *start;
! 206:
! 207: if (!(size = sbp->st_size))
! 208: return;
! 209:
! 210: if (size > SIZE_T_MAX) {
! 211: err(0, "%s: %s", fname, strerror(EFBIG));
! 212: return;
! 213: }
! 214:
! 215: if ((start = mmap(NULL, (size_t)size,
! 216: PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) {
! 217: err(0, "%s: %s", fname, strerror(EFBIG));
! 218: return;
! 219: }
! 220:
! 221: /* Last char is special, ignore whether newline or not. */
! 222: for (p = start + size - 1; --size;)
! 223: if (*--p == '\n' && !--off) {
! 224: ++p;
! 225: break;
! 226: }
! 227:
! 228: /* Set the file pointer to reflect the length displayed. */
! 229: size = sbp->st_size - size;
! 230: WR(p, size);
! 231: if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) {
! 232: ierr();
! 233: return;
! 234: }
! 235: if (munmap(start, (size_t)sbp->st_size)) {
! 236: err(0, "%s: %s", fname, strerror(errno));
! 237: return;
! 238: }
! 239: }
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