mirror of
https://github.com/reactos/reactos.git
synced 2024-11-02 21:09:15 +00:00
135 lines
3.5 KiB
C
135 lines
3.5 KiB
C
/* ------------------- decomp.c -------------------- */
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/*
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* Decompress the application.HLP file
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* or load the application.TXT file if the .HLP file
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* does not exist
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*/
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#include "dflat.h"
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#include "htree.h"
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static int in8;
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static int ct8 = 8;
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static FILE *fi;
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static DF_BYTECOUNTER bytectr;
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static int LoadingASCII;
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struct DfHTr *DfHelpTree;
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static int root;
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/* ------- open the help database file -------- */
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FILE *DfOpenHelpFile(void)
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{
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char *cp;
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int treect, i;
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char helpname[65];
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/* -------- get the name of the help file ---------- */
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DfBuildFileName(helpname, ".hlp");
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LoadingASCII = FALSE;
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if ((fi = fopen(helpname, "rb")) == NULL) {
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/* ---- no .hlp file, look for .txt file ---- */
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if ((cp = strrchr(helpname, '.')) != NULL) {
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strcpy(cp, ".TXT");
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fi = fopen(helpname, "rt");
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}
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if (fi == NULL)
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return NULL;
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LoadingASCII = TRUE;
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}
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if (!LoadingASCII && DfHelpTree == NULL) {
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/* ----- read the byte count ------ */
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fread(&bytectr, sizeof bytectr, 1, fi);
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/* ----- read the frequency count ------ */
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fread(&treect, sizeof treect, 1, fi);
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/* ----- read the root offset ------ */
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fread(&root, sizeof root, 1, fi);
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DfHelpTree = DfCalloc(treect-256, sizeof(struct DfHTr));
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/* ---- read in the tree --- */
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for (i = 0; i < treect-256; i++) {
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fread(&DfHelpTree[i].left, sizeof(int), 1, fi);
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fread(&DfHelpTree[i].right, sizeof(int), 1, fi);
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}
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}
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return fi;
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}
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/* ----- read a line of text from the help database ----- */
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void *DfGetHelpLine(char *line)
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{
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int h;
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if (LoadingASCII) {
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void *hp;
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do
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hp = fgets(line, 160, fi);
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while (*line == ';');
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return hp;
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}
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*line = '\0';
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while (TRUE) {
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/* ----- decompress a line from the file ------ */
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h = root;
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/* ----- walk the Huffman tree ----- */
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while (h > 255) {
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/* --- h is a node pointer --- */
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if (ct8 == 8) {
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/* --- read 8 bits of compressed data --- */
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if ((in8 = fgetc(fi)) == EOF) {
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*line = '\0';
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return NULL;
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}
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ct8 = 0;
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}
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/* -- point to left or right node based on msb -- */
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if (in8 & 0x80)
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h = DfHelpTree[h-256].left;
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else
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h = DfHelpTree[h-256].right;
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/* --- shift the next bit in --- */
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in8 <<= 1;
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ct8++;
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}
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/* --- h < 255 = decompressed character --- */
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if (h == '\r')
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continue; /* skip the '\r' character */
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/* --- put the character in the buffer --- */
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*line++ = h;
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/* --- if '\n', end of line --- */
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if (h == '\n')
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break;
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}
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*line = '\0'; /* null-terminate the line */
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return line;
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}
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/* --- compute the database file byte and bit position --- */
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void DfHelpFilePosition(long *offset, int *bit)
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{
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*offset = ftell(fi);
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if (LoadingASCII)
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*bit = 0;
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else {
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if (ct8 < 8)
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--*offset;
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*bit = ct8;
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}
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}
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/* -- position the database to the specified byte and bit -- */
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void DfSeekHelpLine(long offset, int bit)
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{
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int i;
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fseek(fi, offset, 0);
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if (!LoadingASCII) {
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ct8 = bit;
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if (ct8 < 8) {
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in8 = fgetc(fi);
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for (i = 0; i < bit; i++)
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in8 <<= 1;
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}
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}
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}
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