asc85enc.c

   1 /*
   2  * asc85enc.c
   3  * Copyright (C) 2000-2003 A.J. van Os; Released under GPL
   4  *
   5  * Description:
   6  * Functions to for ASCII 85 encoding
   7  *
   8  *====================================================================
   9  * This part of the software is based on:
  10  * asc85ec.c - ASCII85 and Hex encoding for PostScript Level 2 and PDF
  11  * Copyright (C) 1994-99 Thomas Merz (tm@muc.de)
  12  *====================================================================
  13  * The credit should go to him, but all the bugs are mine.
  14  */
  15
  16 #include <stdio.h>
  17 #include "antiword.h"
  18
  19 static const ULONG      aulPower85[5] = {
  20         1UL, 85UL, 85UL * 85, 85UL * 85 * 85, 85UL * 85 * 85 * 85,
  21 };
  22 static int      iOutBytes = 0;  /* Number of characters in an output line */
  23 static char     cCharPrev = '\0';
  24
  25 /*
  26  * Two percent characters at the start of a line will cause trouble
  27  * with some post-processing software. In order to avoid this, we
  28  * simply insert a line break if we encounter two percent characters
  29  * at the start of the line. Of course, this rather simplistic
  30  * algorithm may lead to a large line count in pathological cases,
  31  * but the chance for hitting such a case is very small, and even
  32  * so it's only a cosmetic flaw and not a functional restriction.
  33  */
  34
  35 /*
  36  * vOutputByte - output one byte
  37  */
  38 static void
  39 vOutputByte(ULONG ulChar, FILE *pOutFile)
  40 {
  41         if (iOutBytes == 1 && cCharPrev == '%' && ulChar == (ULONG)'%') {
  42                 if (putc('\n', pOutFile) != EOF) {
  43                         iOutBytes = 0;
  44                 }
  45         }
  46         if (putc((int)ulChar, pOutFile) == EOF) {
  47                 return;
  48         }
  49         iOutBytes++;
  50         if (iOutBytes > 63) {
  51                 if (putc('\n', pOutFile) != EOF) {
  52                         iOutBytes = 0;
  53                 }
  54         }
  55         cCharPrev = (char)ulChar;
  56 } /* end of vOutputByte */
  57
  58 /*
  59  * vASCII85EncodeByte - ASCII 85 encode a byte
  60  */
  61 void
  62 vASCII85EncodeByte(FILE *pOutFile, int iByte)
  63 {
  64         static ULONG    ulBuffer[4] = { 0, 0, 0, 0 };
  65         static int      iInBuffer = 0;
  66         ULONG   ulValue, ulTmp;
  67         int     iIndex;
  68
  69         fail(pOutFile == NULL);
  70         fail(iInBuffer < 0);
  71         fail(iInBuffer > 3);
  72
  73         if (iByte == EOF) {
  74                 /* End Of File, time to clean up */
  75                 if (iInBuffer > 0 && iInBuffer < 4) {
  76                         /* Encode the remaining bytes */
  77                         ulValue = 0;
  78                         for (iIndex = iInBuffer - 1; iIndex >= 0; iIndex--) {
  79                                 ulValue |=
  80                                         ulBuffer[iIndex] << (8 * (3 - iIndex));
  81                         }
  82                         for (iIndex = 4; iIndex >= 4 - iInBuffer; iIndex--) {
  83                                 ulTmp = ulValue / aulPower85[iIndex];
  84                                 vOutputByte(ulTmp + '!', pOutFile);
  85                                 ulValue -= ulTmp * aulPower85[iIndex];
  86                         }
  87                 }
  88                 /* Add the End Of Data marker */
  89                 (void)putc('~', pOutFile);
  90                 (void)putc('>', pOutFile);
  91                 (void)putc('\n', pOutFile);
  92                 /* Reset the control variables */
  93                 iInBuffer = 0;
  94                 iOutBytes = 0;
  95                 cCharPrev = '\0';
  96                 return;
  97         }
  98
  99         ulBuffer[iInBuffer] = (ULONG)iByte & 0xff;
 100         iInBuffer++;
 101
 102         if (iInBuffer >= 4) {
 103                 ulValue = (ulBuffer[0] << 24) | (ulBuffer[1] << 16) |
 104                         (ulBuffer[2] << 8) | ulBuffer[3];
 105                 if (ulValue == 0) {
 106                         vOutputByte((ULONG)'z', pOutFile); /* Shortcut for 0 */
 107                 } else {
 108                         for (iIndex = 4; iIndex >= 0; iIndex--) {
 109                                 ulTmp = ulValue / aulPower85[iIndex];
 110                                 vOutputByte(ulTmp + '!', pOutFile);
 111                                 ulValue -= ulTmp * aulPower85[iIndex];
 112                         }
 113                 }
 114                 /* Reset the buffer */
 115                 iInBuffer = 0;
 116         }
 117 } /* end of vASCII85EncodeByte */
 118
 119 /*
 120  * vASCII85EncodeArray - ASCII 85 encode a byte array
 121  */
 122 void
 123 vASCII85EncodeArray(FILE *pInFile, FILE *pOutFile, size_t tLength)
 124 {
 125         size_t  tCount;
 126         int     iByte;
 127
 128         fail(pInFile == NULL);
 129         fail(pOutFile == NULL);
 130
 131         DBG_DEC(tLength);
 132
 133         for (tCount = 0; tCount < tLength; tCount++) {
 134                 iByte = iNextByte(pInFile);
 135                 if (iByte == EOF) {
 136                         break;
 137                 }
 138                 vASCII85EncodeByte(pOutFile, iByte);
 139         }
 140 } /* end of vASCII85EncodeArray */
 141
 142 /*
 143  * vASCII85EncodeFile - ASCII 85 encode part of a file
 144  */
 145 void
 146 vASCII85EncodeFile(FILE *pInFile, FILE *pOutFile, size_t tLength)
 147 {
 148         fail(pInFile == NULL);
 149         fail(pOutFile == NULL);
 150         fail(tLength == 0);
 151
 152         vASCII85EncodeArray(pInFile, pOutFile, tLength);
 153         vASCII85EncodeByte(pOutFile, EOF);
 154 } /* end of vASCII85EncodeFile */