www.pudn.com > slow.zip > doc.C

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	doc.c 
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/* Modem for MIPS   AJF	  January 1995 
   Send a document (T.4), in Group 3 format on stdin */ 
 
#include  
 
#include "modem.h" 
 
#define MAXPAGES 50 
#define VERSION	 1 
 
static FILE *g3file; 
static int pageptrs[MAXPAGES];	/* ptr to start of page in file */ 
static int pagebits[MAXPAGES];	/* num. of bits in each page	*/ 
 
 
global void initdoc() 
  { g3file = tmpfile(); 
    if (g3file == NULL) giveup("can't create temporary file"); 
  } 
 
global void readdoc() 
  { /* Copy document from stdin to g3file */ 
    infomsg("Reading input..."); 
    int vsn, xres, yres; 
    int ni = scanf("! %d %d %d\n", &vsn, &xres, &yres); 
    unless (ni == 3 && vsn == VERSION && xres == 200 && (yres == 100 || yres == 200)) 
      giveup("input is not in Group 3 format"); 
    if (yres == 200) options |= opt_H; 
    numpages = 0; 
    int ch = getchar(); 
    while (ch >= 0 && numpages < MAXPAGES) 
      { pageptrs[numpages] = ftell(g3file); 
	int nbits = 0; 
	/* Transfer one page from stdin to g3file */ 
	uint prevbits = ~0; int neols = 0; 
	while (neols < 5) 
	  { if (ch < 0) goto l; /* ignore (we hope, short) partial page */ 
	    uchar c = ch; 
	    for (int j = 0; j < 8 && neols < 5; j++) 
	      { prevbits = (prevbits << 1) | (c >> 7); 
		c <<= 1; nbits++; 
		/* 6 consecutive EOLs mark end of page; note that 2 consec. EOLs never occur in body of page */ 
		if ((prevbits & 0xffffff) == 0x001001) neols++; 
	      } 
	    putc(ch, g3file); 
	    ch = getchar(); 
	  } 
	pagebits[numpages++] = nbits-72;	/* don't count the RTC in the bit count */ 
      } 
l:  if (ch >= 0) giveup("sorry, too many pages"); 
    if (fflush(g3file) != 0) giveup("write error on temp file"); 
  } 
 
global void sendpage(int pn, int scanbits) 
  { /* Copy one page from g3file to V.29 */ 
    if (options & opt_v) fprintf(stderr, ">>> Page %d\n", pn); 
    if (pn < 1 || pn > numpages) giveup("bug: bad page page number: %d", pn); 
    fseek(g3file, pageptrs[pn-1], 0); 
    int nb = 0, lb = 0; 
    uint prevbits = ~0; 
    while (nb < pagebits[pn-1]) 
      { uchar c = getc(g3file); 
	for (int j = 0; j < 8 && nb < pagebits[pn-1]; j++) 
	  { int b = c >> 7; 
	    prevbits = (prevbits << 1) | b; 
	    if ((prevbits & 0xfff) == 0x001)	/* EOL */ 
	      { while (lb++ < scanbits) putbit(0);  /* pad scan line to achieve min. scan time */ 
		lb = 0; 
	      } 
	    putbit(b); 
	    lb++; nb++; c <<= 1; 
	  } 
      } 
    while (lb++ < scanbits) putbit(0);	/* pad final scan line */ 
    for (int i=0; i<6; i++)		/* send RTC */ 
      { for (int j=0; j<11; j++) putbit(0); 
	putbit(1); 
      } 
    for (int i=0; i<50; i++) putbit(0); /* flush buffer */ 
  } 
 
global void receivepage(int pn) 
  { /* Copy one page from V.29 to g3file */ 
    if (options & opt_v) fprintf(stderr, "<<< Page %d\n", pn); 
    if (pn < 1) giveup("bug: bad page page number: %d", pn); 
    uint prevbits = ~0; int neols = 0; 
    while (neols < 5) 
      { uchar n; int nb = 0; 
	while (nb < 8 && neols < 5) 
	  { int b = getbit(); 
	    prevbits = (prevbits << 1) | b; 
	    n = (n << 1) | b; 
	    nb++; 
	    /* 6 consecutive EOLs mark end of page; note that 2 consec. EOLs never occur in body of page */ 
	    if ((prevbits & 0xffffff) == 0x001001) neols++; 
	  } 
	while (nb < 8) { n <<= 1; nb++; } 
	putc(n, g3file); 
      } 
    if (fflush(g3file) != 0) giveup("write error on temp file"); 
  } 
 
global void writedoc() 
  { /* Copy document from g3file to stdout */ 
    infomsg("Writing output..."); 
    printf("! %d %d %d\n", VERSION, 200, (options & opt_H) ? 200 : 100); 
    rewind(g3file); 
    int ch = getc(g3file); 
    while (ch >= 0) { putchar(ch); ch = getc(g3file); } 
    if (fflush(stdout) != 0) giveup("write error on stdout"); 
  }