terminal.c

putty

		assert(runlen >= 2 && runlen <= 129);
		b->data[runpos] = runlen + 0x80 - 2;

		hdrpos = b->len;
		hdrsize = 0;
		add(b, 0);
		/* And ensure this run doesn't interfere with the next. */
		prevlen = prevpos = 0;
		prev2 = FALSE;

		continue;
	    } else {
		/*
		 * Just flag that the previous two literals were
		 * identical, in case we find a third identical one
		 * we want to turn into a run.
		 */
		prev2 = TRUE;
		prevlen = thislen;
		prevpos = thispos;
	    }
	} else {
	    prev2 = FALSE;
	    prevlen = thislen;
	    prevpos = thispos;
	}

	/*
	 * This character isn't (yet) part of a run. Add it to
	 * hdrsize.
	 */
	hdrsize++;
	if (hdrsize == 128) {
	    b->data[hdrpos] = hdrsize - 1;
	    hdrpos = b->len;
	    hdrsize = 0;
	    add(b, 0);
	    prevlen = prevpos = 0;
	    prev2 = FALSE;
	}
    }

    /*
     * Clean up.
     */
    if (hdrsize > 0) {
	assert(hdrsize <= 128);
	b->data[hdrpos] = hdrsize - 1;
    } else {
	b->len = hdrpos;
    }
}
static void makeliteral_chr(struct buf *b, termchar *c, unsigned long *state)
{
    /*
     * My encoding for characters is UTF-8-like, in that it stores
     * 7-bit ASCII in one byte and uses high-bit-set bytes as
     * introducers to indicate a longer sequence. However, it's
     * unlike UTF-8 in that it doesn't need to be able to
     * resynchronise, and therefore I don't want to waste two bits
     * per byte on having recognisable continuation characters.
     * Also I don't want to rule out the possibility that I may one
     * day use values 0x80000000-0xFFFFFFFF for interesting
     * purposes, so unlike UTF-8 I need a full 32-bit range.
     * Accordingly, here is my encoding:
     * 
     * 00000000-0000007F: 0xxxxxxx (but see below)
     * 00000080-00003FFF: 10xxxxxx xxxxxxxx
     * 00004000-001FFFFF: 110xxxxx xxxxxxxx xxxxxxxx
     * 00200000-0FFFFFFF: 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
     * 10000000-FFFFFFFF: 11110ZZZ xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
     * 
     * (`Z' is like `x' but is always going to be zero since the
     * values I'm encoding don't go above 2^32. In principle the
     * five-byte form of the encoding could extend to 2^35, and
     * there could be six-, seven-, eight- and nine-byte forms as
     * well to allow up to 64-bit values to be encoded. But that's
     * completely unnecessary for these purposes!)
     * 
     * The encoding as written above would be very simple, except
     * that 7-bit ASCII can occur in several different ways in the
     * terminal data; sometimes it crops up in the D800 page
     * (CSET_ASCII) but at other times it's in the 0000 page (real
     * Unicode). Therefore, this encoding is actually _stateful_:
     * the one-byte encoding of 00-7F actually indicates `reuse the
     * upper three bytes of the last character', and to encode an
     * absolute value of 00-7F you need to use the two-byte form
     * instead.
     */
    if ((c->chr & ~0x7F) == *state) {
	add(b, (unsigned char)(c->chr & 0x7F));
    } else if (c->chr < 0x4000) {
	add(b, (unsigned char)(((c->chr >> 8) & 0x3F) | 0x80));
	add(b, (unsigned char)(c->chr & 0xFF));
    } else if (c->chr < 0x200000) {
	add(b, (unsigned char)(((c->chr >> 16) & 0x1F) | 0xC0));
	add(b, (unsigned char)((c->chr >> 8) & 0xFF));
	add(b, (unsigned char)(c->chr & 0xFF));
    } else if (c->chr < 0x10000000) {
	add(b, (unsigned char)(((c->chr >> 24) & 0x0F) | 0xE0));
	add(b, (unsigned char)((c->chr >> 16) & 0xFF));
	add(b, (unsigned char)((c->chr >> 8) & 0xFF));
	add(b, (unsigned char)(c->chr & 0xFF));
    } else {
	add(b, 0xF0);
	add(b, (unsigned char)((c->chr >> 24) & 0xFF));
	add(b, (unsigned char)((c->chr >> 16) & 0xFF));
	add(b, (unsigned char)((c->chr >> 8) & 0xFF));
	add(b, (unsigned char)(c->chr & 0xFF));
    }
    *state = c->chr & ~0xFF;
}
static void makeliteral_attr(struct buf *b, termchar *c, unsigned long *state)
{
    /*
     * My encoding for attributes is 16-bit-granular and assumes
     * that the top bit of the word is never required. I either
     * store a two-byte value with the top bit clear (indicating
     * just that value), or a four-byte value with the top bit set
     * (indicating the same value with its top bit clear).
     * 
     * However, first I permute the bits of the attribute value, so
     * that the eight bits of colour (four in each of fg and bg)
     * which are never non-zero unless xterm 256-colour mode is in
     * use are placed higher up the word than everything else. This
     * ensures that attribute values remain 16-bit _unless_ the
     * user uses extended colour.
     */
    unsigned attr, colourbits;

    attr = c->attr;

    assert(ATTR_BGSHIFT > ATTR_FGSHIFT);

    colourbits = (attr >> (ATTR_BGSHIFT + 4)) & 0xF;
    colourbits <<= 4;
    colourbits |= (attr >> (ATTR_FGSHIFT + 4)) & 0xF;

    attr = (((attr >> (ATTR_BGSHIFT + 8)) << (ATTR_BGSHIFT + 4)) |
	    (attr & ((1 << (ATTR_BGSHIFT + 4))-1)));
    attr = (((attr >> (ATTR_FGSHIFT + 8)) << (ATTR_FGSHIFT + 4)) |
	    (attr & ((1 << (ATTR_FGSHIFT + 4))-1)));

    attr |= (colourbits << (32-9));

    if (attr < 0x8000) {
	add(b, (unsigned char)((attr >> 8) & 0xFF));
	add(b, (unsigned char)(attr & 0xFF));
    } else {
	add(b, (unsigned char)(((attr >> 24) & 0x7F) | 0x80));
	add(b, (unsigned char)((attr >> 16) & 0xFF));
	add(b, (unsigned char)((attr >> 8) & 0xFF));
	add(b, (unsigned char)(attr & 0xFF));
    }
}
static void makeliteral_cc(struct buf *b, termchar *c, unsigned long *state)
{
    /*
     * For combining characters, I just encode a bunch of ordinary
     * chars using makeliteral_chr, and terminate with a \0
     * character (which I know won't come up as a combining char
     * itself).
     * 
     * I don't use the stateful encoding in makeliteral_chr.
     */
    unsigned long zstate;
    termchar z;

    while (c->cc_next) {
	c += c->cc_next;

	assert(c->chr != 0);

	zstate = 0;
	makeliteral_chr(b, c, &zstate);
    }

    z.chr = 0;
    zstate = 0;
    makeliteral_chr(b, &z, &zstate);
}

static termline *decompressline(unsigned char *data, int *bytes_used);

static unsigned char *compressline(termline *ldata)
{
    struct buf buffer = { NULL, 0, 0 }, *b = &buffer;

    /*
     * First, store the column count, 7 bits at a time, least
     * significant `digit' first, with the high bit set on all but
     * the last.
     */
    {
	int n = ldata->cols;
	while (n >= 128) {
	    add(b, (unsigned char)((n & 0x7F) | 0x80));
	    n >>= 7;
	}
	add(b, (unsigned char)(n));
    }

    /*
     * Next store the lattrs; same principle.
     */
    {
	int n = ldata->lattr;
	while (n >= 128) {
	    add(b, (unsigned char)((n & 0x7F) | 0x80));
	    n >>= 7;
	}
	add(b, (unsigned char)(n));
    }

    /*
     * Now we store a sequence of separate run-length encoded
     * fragments, each containing exactly as many symbols as there
     * are columns in the ldata.
     * 
     * All of these have a common basic format:
     * 
     *  - a byte 00-7F indicates that X+1 literals follow it
     * 	- a byte 80-FF indicates that a single literal follows it
     * 	  and expects to be repeated (X-0x80)+2 times.
     * 
     * The format of the `literals' varies between the fragments.
     */
    makerle(b, ldata, makeliteral_chr);
    makerle(b, ldata, makeliteral_attr);
    makerle(b, ldata, makeliteral_cc);

    /*
     * Diagnostics: ensure that the compressed data really does
     * decompress to the right thing.
     * 
     * This is a bit performance-heavy for production code.
     */
#ifdef TERM_CC_DIAGS
#ifndef CHECK_SB_COMPRESSION
    {
	int dused;
	termline *dcl;
	int i;

#ifdef DIAGNOSTIC_SB_COMPRESSION
	for (i = 0; i < b->len; i++) {
	    printf(" %02x ", b->data[i]);
	}
	printf("\n");
#endif

	dcl = decompressline(b->data, &dused);
	assert(b->len == dused);
	assert(ldata->cols == dcl->cols);
	assert(ldata->lattr == dcl->lattr);
	for (i = 0; i < ldata->cols; i++)
	    assert(termchars_equal(&ldata->chars[i], &dcl->chars[i]));

#ifdef DIAGNOSTIC_SB_COMPRESSION
	printf("%d cols (%d bytes) -> %d bytes (factor of %g)\n",
	       ldata->cols, 4 * ldata->cols, dused,
	       (double)dused / (4 * ldata->cols));
#endif

	freeline(dcl);
    }
#endif
#endif /* TERM_CC_DIAGS */

    /*
     * Trim the allocated memory so we don't waste any, and return.
     */
    return sresize(b->data, b->len, unsigned char);
}

static void readrle(struct buf *b, termline *ldata,
		    void (*readliteral)(struct buf *b, termchar *c,
					termline *ldata, unsigned long *state))
{
    int n = 0;
    unsigned long state = 0;

    while (n < ldata->cols) {
	int hdr = get(b);

	if (hdr >= 0x80) {
	    /* A run. */

	    int pos = b->len, count = hdr + 2 - 0x80;
	    while (count--) {
		assert(n < ldata->cols);
		b->len = pos;
		readliteral(b, ldata->chars + n, ldata, &state);
		n++;
	    }
	} else {
	    /* Just a sequence of consecutive literals. */

	    int count = hdr + 1;
	    while (count--) {
		assert(n < ldata->cols);
		readliteral(b, ldata->chars + n, ldata, &state);
		n++;
	    }
	}
    }

    assert(n == ldata->cols);
}
static void readliteral_chr(struct buf *b, termchar *c, termline *ldata,
			    unsigned long *state)
{
    int byte;

    /*
     * 00000000-0000007F: 0xxxxxxx
     * 00000080-00003FFF: 10xxxxxx xxxxxxxx
     * 00004000-001FFFFF: 110xxxxx xxxxxxxx xxxxxxxx
     * 00200000-0FFFFFFF: 1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
     * 10000000-FFFFFFFF: 11110ZZZ xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
     */

    byte = get(b);
    if (byte < 0x80) {
	c->chr = byte | *state;
    } else if (byte < 0xC0) {
	c->chr = (byte &~ 0xC0) << 8;
	c->chr |= get(b);
    } else if (byte < 0xE0) {
	c->chr = (byte &~ 0xE0) << 16;
	c->chr |= get(b) << 8;
	c->chr |= get(b);
    } else if (byte < 0xF0) {
	c->chr = (byte &~ 0xF0) << 24;
	c->chr |= get(b) << 16;
	c->chr |= get(b) << 8;
	c->chr |= get(b);
    } else {
	assert(byte == 0xF0);
	c->chr = get(b) << 24;
	c->chr |= get(b) << 16;
	c->chr |= get(b) << 8;
	c->chr |= get(b);
    }
    *state = c->chr & ~0xFF;
}
static void readliteral_attr(struct buf *b, termchar *c, termline *ldata,
			     unsigned long *state)
{
    unsigned val, attr, colourbits;

    val = get(b) << 8;
    val |= get(b);

    if (val >= 0x8000) {
	val &= ~0x8000;
	val <<= 16;
	val |= get(b) << 8;
	val |= get(b);
    }

    colourbits = (val >> (32-9)) & 0xFF;
    attr = (val & ((1<<(32-9))-1));

    attr = (((attr >> (ATTR_FGSHIFT + 4)) << (ATTR_FGSHIFT + 8)) |
	    (attr & ((1 << (ATTR_FGSHIFT + 4))-1)));
    attr = (((attr >> (ATTR_BGSHIFT + 4)) << (ATTR_BGSHIFT + 8)) |
	    (attr & ((1 << (ATTR_BGSHIFT + 4))-1)));

    attr |= (colourbits >> 4) << (ATTR_BGSHIFT + 4);
    attr |= (colourbits & 0xF) << (ATTR_FGSHIFT + 4);

    c->attr = attr;
}
static void readliteral_cc(struct buf *b, termchar *c, termline *ldata,
			   unsigned long *state)
{
    termchar n;
    unsigned long zstate;
    int x = c - ldata->chars;

    c->cc_next = 0;

    while (1) {
	zstate = 0;
	readliteral_chr(b, &n, ldata, &zstate);
	if (!n.chr)
	    break;
	add_cc(ldata, x, n.chr);
    }
}

static termline *decompressline(unsigned char *data, int *bytes_used)
{
    int ncols, byte, shift;
    struct buf buffer, *b = &buffer;
    termline *ldata;

    b->data = data;
    b->len = 0;

    /*
     * First read in the column count.
     */
    ncols = shift = 0;
    do {
	byte = get(b);
	ncols |= (byte & 0x7F) << shift;
	shift += 7;
    } while (byte & 0x80);

    /*
     * Now create the output termline.
     */
    ldata = snew(termline);
    ldata->chars = snewn(ncols, termchar);
    ldata->cols = ldata->size = ncols;
    ldata->temporary = TRUE;
    ldata->cc_free = 0;

    /*
     * We must set all the cc pointers in ldata->chars to 0 right
     * now, so that cc diagnostics that verify the integrity of the
     * whole line will make sense while we're in the middle of
     * building it up.
     */
    {
	int i;
	for (i = 0; i < ldata->cols; i++)
	    ldata->chars[i].cc_next = 0;
    }

    /*
     * Now read in the lattr.
     */
    ldata->lattr = shift = 0;
    do {
	byte = get(b);
	ldata->lattr |= (byte & 0x7F) << shift;
	shift += 7;
    } while (byte & 0x80);

    /*
     * Now we read in each of the RLE streams in turn.
     */
    readrle(b, ldata, readliteral_chr);
    readrle(b, ldata, readliteral_attr);
    readrle(b, ldata, readliteral_cc);

    /* Return the number of bytes read, for diagnostic purposes. */