69 lines
1.6 KiB
C
69 lines
1.6 KiB
C
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/* expand.c -- Byte Pair Encoding decompression */
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/* Copyright 1996 Philip Gage */
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/* Byte Pair Compression appeared in the September 1997
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* issue of C/C++ Users Journal. The original source code
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* may still be found at the web site of the magazine
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* (www.cuj.com).
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*
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* The decompressor has been modified by me (Thiadmer
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* Riemersma) to accept a string as input, instead of a
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* complete file.
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*/
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#include <assert.h>
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#include <stdio.h>
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#include "sc.h"
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#define STACKSIZE 16
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SC_FUNC int strexpand(char *dest, unsigned char *source, int maxlen, unsigned char pairtable[128][2])
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{
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unsigned char stack[STACKSIZE];
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short c, top = 0;
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int len;
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assert(maxlen > 0);
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len = 1; /* already 1 byte for '\0' */
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for (;;) {
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/* Pop byte from stack or read byte from the input string */
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if (top)
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c = stack[--top];
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else if ((c = *(unsigned char *)source++) == '\0')
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break;
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/* Push pair on stack or output byte to the output string */
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if (c > 127) {
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assert(top+2 <= STACKSIZE);
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stack[top++] = pairtable[c-128][1];
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stack[top++] = pairtable[c-128][0];
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}
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else {
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len++;
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if (maxlen > 1) { /* reserve one byte for the '\0' */
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*dest++ = (char)c;
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maxlen--;
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}
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}
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}
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*dest = '\0';
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return len; /* return number of bytes decoded */
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}
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#if 0 /*for testing*/
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#include "sc5.scp"
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int main (int argc, char **argv)
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{
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int i;
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char str[128];
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for (i=0; i<58; i++) {
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strexpand(str, errmsg[i], sizeof str, SCPACK_TABLE);
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printf("%s", str);
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} /* for */
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return 0;
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}
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#endif
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