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/*
 * asc85enc.c
 * Copyright (C) 2000-2003 A.J. van Os; Released under GPL
 *
 * Description:
 * Functions to for ASCII 85 encoding
 *
 *====================================================================
 * This part of the software is based on:
 * asc85ec.c - ASCII85 and Hex encoding for PostScript Level 2 and PDF
 * Copyright (C) 1994-99 Thomas Merz (tm@muc.de)
 *====================================================================
 * The credit should go to him, but all the bugs are mine.
 */

#include <stdio.h>
#include "antiword.h"

static const ULONG      aulPower85[5] = {
        1UL, 85UL, 85UL * 85, 85UL * 85 * 85, 85UL * 85 * 85 * 85,
};
static int      iOutBytes = 0;  /* Number of characters in an output line */
static char     cCharPrev = '\0';

/*
 * Two percent characters at the start of a line will cause trouble
 * with some post-processing software. In order to avoid this, we
 * simply insert a line break if we encounter two percent characters
 * at the start of the line. Of course, this rather simplistic
 * algorithm may lead to a large line count in pathological cases,
 * but the chance for hitting such a case is very small, and even
 * so it's only a cosmetic flaw and not a functional restriction.
 */

/*
 * vOutputByte - output one byte
 */
static void
vOutputByte(ULONG ulChar, FILE *pOutFile)
{
        if (iOutBytes == 1 && cCharPrev == '%' && ulChar == (ULONG)'%') {
                if (putc('\n', pOutFile) != EOF) {
                        iOutBytes = 0;
                }
        }
        if (putc((int)ulChar, pOutFile) == EOF) {
                return;
        }
        iOutBytes++;
        if (iOutBytes > 63) {
                if (putc('\n', pOutFile) != EOF) {
                        iOutBytes = 0;
                }
        }
        cCharPrev = (char)ulChar;
} /* end of vOutputByte */

/*
 * vASCII85EncodeByte - ASCII 85 encode a byte
 */
void
vASCII85EncodeByte(FILE *pOutFile, int iByte)
{
        static ULONG    ulBuffer[4] = { 0, 0, 0, 0 };
        static int      iInBuffer = 0;
        ULONG   ulValue, ulTmp;
        int     iIndex;

        fail(pOutFile == NULL);
        fail(iInBuffer < 0);
        fail(iInBuffer > 3);

        if (iByte == EOF) {
                /* End Of File, time to clean up */
                if (iInBuffer > 0 && iInBuffer < 4) {
                        /* Encode the remaining bytes */
                        ulValue = 0;
                        for (iIndex = iInBuffer - 1; iIndex >= 0; iIndex--) {
                                ulValue |=
                                        ulBuffer[iIndex] << (8 * (3 - iIndex));
                        }
                        for (iIndex = 4; iIndex >= 4 - iInBuffer; iIndex--) {
                                ulTmp = ulValue / aulPower85[iIndex];
                                vOutputByte(ulTmp + '!', pOutFile);
                                ulValue -= ulTmp * aulPower85[iIndex];
                        }
                }
                /* Add the End Of Data marker */
                (void)putc('~', pOutFile);
                (void)putc('>', pOutFile);
                (void)putc('\n', pOutFile);
                /* Reset the control variables */
                iInBuffer = 0;
                iOutBytes = 0;
                cCharPrev = '\0';
                return;
        }

        ulBuffer[iInBuffer] = (ULONG)iByte & 0xff;
        iInBuffer++;

        if (iInBuffer >= 4) {
                ulValue = (ulBuffer[0] << 24) | (ulBuffer[1] << 16) |
                        (ulBuffer[2] << 8) | ulBuffer[3];
                if (ulValue == 0) {
                        vOutputByte((ULONG)'z', pOutFile); /* Shortcut for 0 */
                } else {
                        for (iIndex = 4; iIndex >= 0; iIndex--) {
                                ulTmp = ulValue / aulPower85[iIndex];
                                vOutputByte(ulTmp + '!', pOutFile);
                                ulValue -= ulTmp * aulPower85[iIndex];
                        }
                }
                /* Reset the buffer */
                iInBuffer = 0;
        }
} /* end of vASCII85EncodeByte */

/*
 * vASCII85EncodeArray - ASCII 85 encode a byte array
 */
void
vASCII85EncodeArray(FILE *pInFile, FILE *pOutFile, size_t tLength)
{
        size_t  tCount;
        int     iByte;

        fail(pInFile == NULL);
        fail(pOutFile == NULL);

        DBG_DEC(tLength);

        for (tCount = 0; tCount < tLength; tCount++) {
                iByte = iNextByte(pInFile);
                if (iByte == EOF) {
                        break;
                }
                vASCII85EncodeByte(pOutFile, iByte);
        }
} /* end of vASCII85EncodeArray */

/*
 * vASCII85EncodeFile - ASCII 85 encode part of a file
 */
void
vASCII85EncodeFile(FILE *pInFile, FILE *pOutFile, size_t tLength)
{
        fail(pInFile == NULL);
        fail(pOutFile == NULL);
        fail(tLength == 0);

        vASCII85EncodeArray(pInFile, pOutFile, tLength);
        vASCII85EncodeByte(pOutFile, EOF);
} /* end of vASCII85EncodeFile */