1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1994 Søren Schmidt 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer, 12 * in this position and unchanged. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. The name of the author may not be used to endorse or promote products 17 * derived from this software without specific prior written permission 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 */ 30 31 #include <stdio.h> 32 #include <string.h> 33 #include "decode.h" 34 35 int decode(FILE *fd, char *buffer, int len) 36 { 37 int n, pos = 0, tpos; 38 char *bp, *p; 39 char tbuffer[3]; 40 char temp[128]; 41 42 #define DEC(c) (((c) - ' ') & 0x3f) 43 44 do { 45 if (!fgets(temp, sizeof(temp), fd)) 46 return(0); 47 } while (strncmp(temp, "begin ", 6)); 48 sscanf(temp, "begin %o %s", (unsigned *)&n, temp); 49 bp = buffer; 50 for (;;) { 51 if (!fgets(p = temp, sizeof(temp), fd)) 52 return(0); 53 if ((n = DEC(*p)) <= 0) 54 break; 55 for (++p; n > 0; p += 4, n -= 3) { 56 tpos = 0; 57 if (n >= 3) { 58 tbuffer[tpos++] = DEC(p[0])<<2 | DEC(p[1])>>4; 59 tbuffer[tpos++] = DEC(p[1])<<4 | DEC(p[2])>>2; 60 tbuffer[tpos++] = DEC(p[2])<<6 | DEC(p[3]); 61 } 62 else { 63 if (n >= 1) { 64 tbuffer[tpos++] = 65 DEC(p[0])<<2 | DEC(p[1])>>4; 66 } 67 if (n >= 2) { 68 tbuffer[tpos++] = 69 DEC(p[1])<<4 | DEC(p[2])>>2; 70 } 71 if (n >= 3) { 72 tbuffer[tpos++] = 73 DEC(p[2])<<6 | DEC(p[3]); 74 } 75 } 76 if (tpos == 0) 77 continue; 78 if (tpos + pos > len) { 79 tpos = len - pos; 80 /* 81 * Arrange return value > len to indicate 82 * overflow. 83 */ 84 pos++; 85 } 86 bcopy(tbuffer, bp, tpos); 87 pos += tpos; 88 bp += tpos; 89 if (pos > len) 90 return(pos); 91 } 92 } 93 if (!fgets(temp, sizeof(temp), fd) || strcmp(temp, "end\n")) 94 return(0); 95 return(pos); 96 } 97