Annotation of src/usr.bin/more/input.c, Revision 1.1
1.1 ! deraadt 1: /*
! 2: * Copyright (c) 1988 Mark Nudleman
! 3: * Copyright (c) 1988 Regents of the University of California.
! 4: * All rights reserved.
! 5: *
! 6: * Redistribution and use in source and binary forms, with or without
! 7: * modification, are permitted provided that the following conditions
! 8: * are met:
! 9: * 1. Redistributions of source code must retain the above copyright
! 10: * notice, this list of conditions and the following disclaimer.
! 11: * 2. Redistributions in binary form must reproduce the above copyright
! 12: * notice, this list of conditions and the following disclaimer in the
! 13: * documentation and/or other materials provided with the distribution.
! 14: * 3. All advertising materials mentioning features or use of this software
! 15: * must display the following acknowledgement:
! 16: * This product includes software developed by the University of
! 17: * California, Berkeley and its contributors.
! 18: * 4. Neither the name of the University nor the names of its contributors
! 19: * may be used to endorse or promote products derived from this software
! 20: * without specific prior written permission.
! 21: *
! 22: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
! 23: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! 24: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! 25: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
! 26: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
! 27: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
! 28: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
! 29: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
! 30: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
! 31: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
! 32: * SUCH DAMAGE.
! 33: */
! 34:
! 35: #ifndef lint
! 36: /* from: static char sccsid[] = "@(#)input.c 5.4 (Berkeley) 6/1/90"; */
! 37: static char *rcsid = "$Id: input.c,v 1.2 1993/11/09 05:09:07 cgd Exp $";
! 38: #endif /* not lint */
! 39:
! 40: /*
! 41: * High level routines dealing with getting lines of input
! 42: * from the file being viewed.
! 43: *
! 44: * When we speak of "lines" here, we mean PRINTABLE lines;
! 45: * lines processed with respect to the screen width.
! 46: * We use the term "raw line" to refer to lines simply
! 47: * delimited by newlines; not processed with respect to screen width.
! 48: */
! 49:
! 50: #include <sys/types.h>
! 51: #include <less.h>
! 52:
! 53: extern int squeeze;
! 54: extern int sigs;
! 55: extern char *line;
! 56:
! 57: off_t ch_tell();
! 58:
! 59: /*
! 60: * Get the next line.
! 61: * A "current" position is passed and a "new" position is returned.
! 62: * The current position is the position of the first character of
! 63: * a line. The new position is the position of the first character
! 64: * of the NEXT line. The line obtained is the line starting at curr_pos.
! 65: */
! 66: off_t
! 67: forw_line(curr_pos)
! 68: off_t curr_pos;
! 69: {
! 70: off_t new_pos;
! 71: register int c;
! 72:
! 73: if (curr_pos == NULL_POSITION || ch_seek(curr_pos))
! 74: return (NULL_POSITION);
! 75:
! 76: c = ch_forw_get();
! 77: if (c == EOI)
! 78: return (NULL_POSITION);
! 79:
! 80: prewind();
! 81: for (;;)
! 82: {
! 83: if (sigs)
! 84: return (NULL_POSITION);
! 85: if (c == '\n' || c == EOI)
! 86: {
! 87: /*
! 88: * End of the line.
! 89: */
! 90: new_pos = ch_tell();
! 91: break;
! 92: }
! 93:
! 94: /*
! 95: * Append the char to the line and get the next char.
! 96: */
! 97: if (pappend(c))
! 98: {
! 99: /*
! 100: * The char won't fit in the line; the line
! 101: * is too long to print in the screen width.
! 102: * End the line here.
! 103: */
! 104: new_pos = ch_tell() - 1;
! 105: break;
! 106: }
! 107: c = ch_forw_get();
! 108: }
! 109: (void) pappend('\0');
! 110:
! 111: if (squeeze && *line == '\0')
! 112: {
! 113: /*
! 114: * This line is blank.
! 115: * Skip down to the last contiguous blank line
! 116: * and pretend it is the one which we are returning.
! 117: */
! 118: while ((c = ch_forw_get()) == '\n')
! 119: if (sigs)
! 120: return (NULL_POSITION);
! 121: if (c != EOI)
! 122: (void) ch_back_get();
! 123: new_pos = ch_tell();
! 124: }
! 125:
! 126: return (new_pos);
! 127: }
! 128:
! 129: /*
! 130: * Get the previous line.
! 131: * A "current" position is passed and a "new" position is returned.
! 132: * The current position is the position of the first character of
! 133: * a line. The new position is the position of the first character
! 134: * of the PREVIOUS line. The line obtained is the one starting at new_pos.
! 135: */
! 136: off_t
! 137: back_line(curr_pos)
! 138: off_t curr_pos;
! 139: {
! 140: off_t new_pos, begin_new_pos;
! 141: int c;
! 142:
! 143: if (curr_pos == NULL_POSITION || curr_pos <= (off_t)0 ||
! 144: ch_seek(curr_pos-1))
! 145: return (NULL_POSITION);
! 146:
! 147: if (squeeze)
! 148: {
! 149: /*
! 150: * Find out if the "current" line was blank.
! 151: */
! 152: (void) ch_forw_get(); /* Skip the newline */
! 153: c = ch_forw_get(); /* First char of "current" line */
! 154: (void) ch_back_get(); /* Restore our position */
! 155: (void) ch_back_get();
! 156:
! 157: if (c == '\n')
! 158: {
! 159: /*
! 160: * The "current" line was blank.
! 161: * Skip over any preceeding blank lines,
! 162: * since we skipped them in forw_line().
! 163: */
! 164: while ((c = ch_back_get()) == '\n')
! 165: if (sigs)
! 166: return (NULL_POSITION);
! 167: if (c == EOI)
! 168: return (NULL_POSITION);
! 169: (void) ch_forw_get();
! 170: }
! 171: }
! 172:
! 173: /*
! 174: * Scan backwards until we hit the beginning of the line.
! 175: */
! 176: for (;;)
! 177: {
! 178: if (sigs)
! 179: return (NULL_POSITION);
! 180: c = ch_back_get();
! 181: if (c == '\n')
! 182: {
! 183: /*
! 184: * This is the newline ending the previous line.
! 185: * We have hit the beginning of the line.
! 186: */
! 187: new_pos = ch_tell() + 1;
! 188: break;
! 189: }
! 190: if (c == EOI)
! 191: {
! 192: /*
! 193: * We have hit the beginning of the file.
! 194: * This must be the first line in the file.
! 195: * This must, of course, be the beginning of the line.
! 196: */
! 197: new_pos = ch_tell();
! 198: break;
! 199: }
! 200: }
! 201:
! 202: /*
! 203: * Now scan forwards from the beginning of this line.
! 204: * We keep discarding "printable lines" (based on screen width)
! 205: * until we reach the curr_pos.
! 206: *
! 207: * {{ This algorithm is pretty inefficient if the lines
! 208: * are much longer than the screen width,
! 209: * but I don't know of any better way. }}
! 210: */
! 211: if (ch_seek(new_pos))
! 212: return (NULL_POSITION);
! 213: loop:
! 214: begin_new_pos = new_pos;
! 215: prewind();
! 216:
! 217: do
! 218: {
! 219: c = ch_forw_get();
! 220: if (c == EOI || sigs)
! 221: return (NULL_POSITION);
! 222: new_pos++;
! 223: if (c == '\n')
! 224: break;
! 225: if (pappend(c))
! 226: {
! 227: /*
! 228: * Got a full printable line, but we haven't
! 229: * reached our curr_pos yet. Discard the line
! 230: * and start a new one.
! 231: */
! 232: (void) pappend('\0');
! 233: (void) ch_back_get();
! 234: new_pos--;
! 235: goto loop;
! 236: }
! 237: } while (new_pos < curr_pos);
! 238:
! 239: (void) pappend('\0');
! 240:
! 241: return (begin_new_pos);
! 242: }
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