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/*
* Decompress the application.HLP file
* or load the application.TXT file if the .HLP file
* does not exist
*/
#include <assert.h>
#include "dflat.h"
#include "htree.h"
static int in8;
static int ct8 = 8;
static FILE *fi;
static BYTECOUNTER bytectr;
struct htr *HelpTree;
static int root;
/* ------- open the help database file -------- */
FILE *OpenHelpFile(const char *fn, const char *md)
{
int treect, i;
char helpname[65];
/* Get the name of the help file */
BuildFileName(helpname, fn, ".hlp");
if ((fi = fopen(helpname, md)) == NULL)
return NULL;
if (HelpTree == NULL)
{
fread(&bytectr, sizeof bytectr, 1, fi); /* Read the byte count */
fread(&treect, sizeof treect, 1, fi); /* Read the frequency count */
fread(&root, sizeof root, 1, fi); /* Read the root offset */
HelpTree=calloc(treect-256, sizeof(struct htr));
if (HelpTree != NULL)
{
for (i=0;i<treect-256;i++) /* Read in the tree */
{
fread(&HelpTree[i].left, sizeof(int), 1, fi);
fread(&HelpTree[i].right, sizeof(int), 1, fi);
}
}
}
return fi;
}
/* ----- read a line of text from the help database ----- */
void *GetHelpLine(char *line)
{
int h;
*line = '\0';
while (TRUE)
{
/* Decompress a line from the file */
h=root;
/* Walk the Huffman tree */
while (h > 255)
{
/* h is a node pointer */
if (ct8 == 8)
{
/* Read 8 bits of compressed data */
if ((in8 = fgetc(fi)) == EOF)
{
*line = '\0';
return NULL;
}
ct8 = 0;
}
/* Point to left or right node based on msb */
if (in8 & 0x80)
h = HelpTree[h-256].left;
else
h = HelpTree[h-256].right;
/* Shift the next bit in */
in8 <<= 1;
ct8++;
}
/* h < 255 = decompressed character */
if (h == '\r') /* Skip the '\r' character */
continue;
*line++ = h; /* Put the character in the buffer */
if (h == '\n') /* End of line */
break;
}
*line = '\0'; /* Null-terminate the line */
return line;
}
/* --- compute the database file byte and bit position --- */
void HelpFilePosition(long *offset, int *bit)
{
*offset = ftell(fi);
if (ct8 < 8)
--*offset;
*bit = ct8;
}
/* -- position the database to the specified byte and bit -- */
void SeekHelpLine(long offset, int bit)
{
int fs = fseek(fi, offset, 0);
assert(fs == 0);
ct8 = bit;
if (ct8 < 8)
{
in8 = fgetc(fi);
in8 <<= bit;
}
}
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