1 /* 2 * Copyright (c) 2000-2001, 2004 Proofpoint, Inc. and its suppliers. 3 * All rights reserved. 4 * Copyright (c) 1990, 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 * Chris Torek. 9 * 10 * By using this file, you agree to the terms and conditions set 11 * forth in the LICENSE file which can be found at the top level of 12 * the sendmail distribution. 13 */ 14 15 #include <sm/gen.h> 16 SM_IDSTR(id, "@(#)$Id: ungetc.c,v 1.31 2013-11-22 20:51:44 ca Exp $") 17 18 #include <stdlib.h> 19 #include <string.h> 20 #include <signal.h> 21 #include <sm/time.h> 22 #include <errno.h> 23 #include <sm/io.h> 24 #include <sm/heap.h> 25 #include <sm/assert.h> 26 #include <sm/conf.h> 27 #include "local.h" 28 29 static void sm_submore_x __P((SM_FILE_T *)); 30 31 /* 32 ** SM_SUBMORE_X -- expand ungetc buffer 33 ** 34 ** Expand the ungetc buffer `in place'. That is, adjust fp->f_p when 35 ** the buffer moves, so that it points the same distance from the end, 36 ** and move the bytes in the buffer around as necessary so that they 37 ** are all at the end (stack-style). 38 ** 39 ** Parameters: 40 ** fp -- the file pointer 41 ** 42 ** Results: 43 ** none. 44 ** 45 ** Exceptions: 46 ** F:sm_heap -- out of memory 47 */ 48 49 static void 50 sm_submore_x(fp) 51 SM_FILE_T *fp; 52 { 53 register int i; 54 register unsigned char *p; 55 56 if (fp->f_ub.smb_base == fp->f_ubuf) 57 { 58 /* Get a buffer; f_ubuf is fixed size. */ 59 p = sm_malloc_x((size_t) SM_IO_BUFSIZ); 60 fp->f_ub.smb_base = p; 61 fp->f_ub.smb_size = SM_IO_BUFSIZ; 62 p += SM_IO_BUFSIZ - sizeof(fp->f_ubuf); 63 for (i = sizeof(fp->f_ubuf); --i >= 0;) 64 p[i] = fp->f_ubuf[i]; 65 fp->f_p = p; 66 return; 67 } 68 i = fp->f_ub.smb_size; 69 p = sm_realloc_x(fp->f_ub.smb_base, i << 1); 70 71 /* no overlap (hence can use memcpy) because we doubled the size */ 72 (void) memcpy((void *) (p + i), (void *) p, (size_t) i); 73 fp->f_p = p + i; 74 fp->f_ub.smb_base = p; 75 fp->f_ub.smb_size = i << 1; 76 } 77 78 /* 79 ** SM_IO_UNGETC -- place a character back into the buffer just read 80 ** 81 ** Parameters: 82 ** fp -- the file pointer affected 83 ** timeout -- time to complete ungetc 84 ** c -- the character to place back 85 ** 86 ** Results: 87 ** On success, returns value of character placed back, 0-255. 88 ** Returns SM_IO_EOF if c == SM_IO_EOF or if last operation 89 ** was a write and flush failed. 90 ** 91 ** Exceptions: 92 ** F:sm_heap -- out of memory 93 */ 94 95 int 96 sm_io_ungetc(fp, timeout, c) 97 register SM_FILE_T *fp; 98 int timeout; 99 int c; 100 { 101 SM_REQUIRE_ISA(fp, SmFileMagic); 102 if (c == SM_IO_EOF) 103 return SM_IO_EOF; 104 if (timeout == SM_TIME_IMMEDIATE) 105 { 106 /* 107 ** Ungetting the buffer will take time and we are wanted to 108 ** return immediately. So... 109 */ 110 111 errno = EAGAIN; 112 return SM_IO_EOF; 113 } 114 115 if (!Sm_IO_DidInit) 116 sm_init(); 117 if ((fp->f_flags & SMRD) == 0) 118 { 119 /* 120 ** Not already reading: no good unless reading-and-writing. 121 ** Otherwise, flush any current write stuff. 122 */ 123 124 if ((fp->f_flags & SMRW) == 0) 125 return SM_IO_EOF; 126 if (fp->f_flags & SMWR) 127 { 128 if (sm_flush(fp, &timeout)) 129 return SM_IO_EOF; 130 fp->f_flags &= ~SMWR; 131 fp->f_w = 0; 132 fp->f_lbfsize = 0; 133 } 134 fp->f_flags |= SMRD; 135 } 136 c = (unsigned char) c; 137 138 /* 139 ** If we are in the middle of ungetc'ing, just continue. 140 ** This may require expanding the current ungetc buffer. 141 */ 142 143 if (HASUB(fp)) 144 { 145 if (fp->f_r >= fp->f_ub.smb_size) 146 sm_submore_x(fp); 147 *--fp->f_p = c; 148 fp->f_r++; 149 return c; 150 } 151 fp->f_flags &= ~SMFEOF; 152 153 /* 154 ** If we can handle this by simply backing up, do so, 155 ** but never replace the original character. 156 ** (This makes sscanf() work when scanning `const' data.) 157 */ 158 159 if (fp->f_bf.smb_base != NULL && fp->f_p > fp->f_bf.smb_base && 160 fp->f_p[-1] == c) 161 { 162 fp->f_p--; 163 fp->f_r++; 164 return c; 165 } 166 167 /* 168 ** Create an ungetc buffer. 169 ** Initially, we will use the `reserve' buffer. 170 */ 171 172 fp->f_ur = fp->f_r; 173 fp->f_up = fp->f_p; 174 fp->f_ub.smb_base = fp->f_ubuf; 175 fp->f_ub.smb_size = sizeof(fp->f_ubuf); 176 fp->f_ubuf[sizeof(fp->f_ubuf) - 1] = c; 177 fp->f_p = &fp->f_ubuf[sizeof(fp->f_ubuf) - 1]; 178 fp->f_r = 1; 179 180 return c; 181 } 182