/* expand.c -- Byte Pair Encoding decompression */

/* Copyright 1996 Philip Gage */

/* Byte Pair Compression appeared in the September 1997

 * issue of C/C++ Users Journal. The original source code

 * may still be found at the web site of the magazine

 * (www.cuj.com).

 *

 * The decompressor has been modified by me (Thiadmer

 * Riemersma) to accept a string as input, instead of a

 * complete file.

 */

#include <assert.h>

#include <stdio.h>

#include "sc.h"

#define STACKSIZE 16

SC_FUNC int strexpand(char *dest, unsigned char *source, int maxlen, unsigned char pairtable[128][2])

{

  unsigned char stack[STACKSIZE];

  short c, top = 0;

  int len;

  assert(maxlen > 0);

  len = 1;              /* already 1 byte for '\0' */

  for (;;) {

    /* Pop byte from stack or read byte from the input string */

    if (top)

      c = stack[--top];

    else if ((c = *(unsigned char *)source++) == '\0')

      break;

    /* Push pair on stack or output byte to the output string */

    if (c > 127) {

      assert(top+2 <= STACKSIZE);

      stack[top++] = pairtable[c-128][1];

      stack[top++] = pairtable[c-128][0];

    }

    else {

      len++;

      if (maxlen > 1) { /* reserve one byte for the '\0' */

        *dest++ = (char)c;

        maxlen--;

      }

    }

  }

  *dest = '\0';

  return len;           /* return number of bytes decoded */

}

#if 0 /*for testing*/

#include "sc5.scp"

int main (int argc, char **argv)

{

  int i;

  char str[128];

  for (i=0; i<58; i++) {

    strexpand(str, errmsg[i], sizeof str, SCPACK_TABLE);

    printf("%s", str);

  } /* for */

  return 0;

}

#endif