cairo-type1-subset.c

按照官方的说法：Cairo is a vector graphics library with cross-device output support. 翻译过来

    "oslash", "oe", "germandbls", 0, 0, 0, 0
};

static void
use_standard_encoding_glyph (cairo_type1_font_subset_t *font, int index)
{
    const char *glyph_name;

    if (index < 0 || index > 255)
	return;

    glyph_name = ps_standard_encoding[index];
    if (glyph_name == NULL)
	return;

    index = cairo_type1_font_subset_lookup_glyph (font,
						  glyph_name,
						  strlen(glyph_name));
    if (index < 0)
	return;

    cairo_type1_font_subset_use_glyph (font, index);
}

#define TYPE1_CHARSTRING_COMMAND_ESCAPE		(12)
#define TYPE1_CHARSTRING_COMMAND_SEAC		(32 + 6)

static void
cairo_type1_font_subset_look_for_seac(cairo_type1_font_subset_t *font,
				      const char *name, int name_length,
				      const char *encrypted_charstring, int encrypted_charstring_length)
{
    unsigned char *charstring;
    const unsigned char *end;
    const unsigned char *p;
    int stack[5], sp, value;
    int command;

    charstring = malloc (encrypted_charstring_length);
    if (charstring == NULL)
	return;

    cairo_type1_font_subset_decrypt_charstring ((const unsigned char *)
						encrypted_charstring,
						encrypted_charstring_length,
						charstring);
    end = charstring + encrypted_charstring_length;

    p = charstring + 4;
    sp = 0;

    while (p < end) {
        if (*p < 32) {
	    command = *p++;

	    if (command == TYPE1_CHARSTRING_COMMAND_ESCAPE)
		command = 32 + *p++;

	    switch (command) {
	    case TYPE1_CHARSTRING_COMMAND_SEAC:
		/* The seac command takes five integer arguments.  The
		 * last two are glyph indices into the PS standard
		 * encoding give the names of the glyphs that this
		 * glyph is composed from.  All we need to do is to
		 * make sure those glyphs are present in the subset
		 * under their standard names. */
		use_standard_encoding_glyph (font, stack[3]);
		use_standard_encoding_glyph (font, stack[4]);
		sp = 0;
		break;

	    default:
		sp = 0;
		break;
	    }
        } else {
            /* integer argument */
	    p = cairo_type1_font_subset_decode_integer (p, &value);
	    if (sp < 5)
		stack[sp++] = value;
        }
    }

    free (charstring);
}

static void
write_used_glyphs (cairo_type1_font_subset_t *font,
		   const char *name, int name_length,
		   const char *charstring, int charstring_length)
{
    char buffer[256];
    int length;

    length = snprintf (buffer, sizeof buffer,
		       "/%.*s %d %s ",
		       name_length, name, charstring_length, font->rd);
    cairo_type1_font_subset_write_encrypted (font, buffer, length);
    cairo_type1_font_subset_write_encrypted (font,
					     charstring, charstring_length);
    length = snprintf (buffer, sizeof buffer, "%s\n", font->nd);
    cairo_type1_font_subset_write_encrypted (font, buffer, length);
}

typedef void (*glyph_func_t) (cairo_type1_font_subset_t *font,
			      const char *name, int name_length,
			      const char *charstring, int charstring_length);

static const char *
cairo_type1_font_subset_for_each_glyph (cairo_type1_font_subset_t *font,
					const char *dict_start,
					const char *dict_end,
					glyph_func_t func)
{
    int charstring_length, name_length, glyph_index;
    const char *p, *charstring, *name;
    char *end;

    /* We're looking at '/' in the name of the first glyph.  The glyph
     * definitions are on the form:
     *
     *   /name 23 RD <23 binary bytes> ND
     *
     * or alternatively using -| and |- instead of RD and ND.
     *
     * We parse the glyph name and see if it is in the subset.  If it
     * is, we call the specified callback with the glyph name and
     * glyph data, otherwise we just skip it.  We need to parse
     * through a glyph definition; we can't just find the next '/',
     * since the binary data could contain a '/'.
     */

    p = dict_start;

    while (*p == '/') {
	name = p + 1;
	p = skip_token (p, dict_end);
	name_length = p - name;

	charstring_length = strtol (p, &end, 10);
	if (p == end) {
	    font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	    return NULL;
	}

	/* Skip past -| or RD to binary data.  There is exactly one space
	 * between the -| or RD token and the encrypted data, thus '+ 1'. */
	charstring = skip_token (end, dict_end) + 1;

	/* Skip binary data and |- or ND token. */
	p = skip_token (charstring + charstring_length, dict_end);
	while (p < dict_end && isspace(*p))
	    p++;

	/* In case any of the skip_token() calls above reached EOF, p will
	 * be equal to dict_end. */
	if (p == dict_end) {
	    font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	    return NULL;
	}

	glyph_index = cairo_type1_font_subset_lookup_glyph (font,
							    name, name_length);
	if (font->glyphs[glyph_index].subset_index >= 0)
	    func (font, name, name_length, charstring, charstring_length);
    }

    return p;
}


static const char *
cairo_type1_font_subset_write_private_dict (cairo_type1_font_subset_t *font,
					    const char                *name)
{
    const char *p, *charstrings, *dict_start;
    const char *closefile_token;
    char buffer[32], *glyph_count_end;
    int num_charstrings, length;

    /* The private dict holds hint information, common subroutines and
     * the actual glyph definitions (charstrings).
     *
     * FIXME: update this comment.
     *
     * What we do here is scan directly the /CharString token, which
     * marks the beginning of the glyph definitions.  Then we parse
     * through the glyph definitions and weed out the glyphs not in
     * our subset.  Everything else before and after the glyph
     * definitions is copied verbatim to the output.  It might be
     * worthwile to figure out which of the common subroutines are
     * used by the glyphs in the subset and get rid of the rest. */

    /* FIXME: The /Subrs array contains binary data and could
     * conceivably have "/CharStrings" in it, so we might need to skip
     * this more cleverly. */
    charstrings = find_token (font->cleartext, font->cleartext_end, "/CharStrings");
    if (charstrings == NULL) {
	font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	return NULL;
    }

    /* Scan past /CharStrings and the integer following it. */
    p = charstrings + strlen ("/CharStrings");
    num_charstrings = strtol (p, &glyph_count_end, 10);
    if (p == glyph_count_end) {
	font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	return NULL;
    }

    /* Look for a '/' which marks the beginning of the first glyph
     * definition. */
    for (p = glyph_count_end; p < font->cleartext_end; p++)
	if (*p == '/')
	    break;
    if (p == font->cleartext_end) {
	font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	return NULL;
    }
    dict_start = p;

    if (cairo_type1_font_subset_get_glyph_names_and_widths (font))
	return NULL;

    /* Now that we have the private dictionary broken down in
     * sections, do the first pass through the glyph definitions to
     * figure out which subrs and othersubrs are use and which extra
     * glyphs may be required by the seac operator. */
    p = cairo_type1_font_subset_for_each_glyph (font,
						dict_start,
						font->cleartext_end,
						cairo_type1_font_subset_look_for_seac);

    closefile_token = find_token (p, font->cleartext_end, "closefile");
    if (closefile_token == NULL) {
	font->status = CAIRO_INT_STATUS_UNSUPPORTED;
	return NULL;
    }

    if (cairo_type1_font_subset_get_glyph_names_and_widths (font))
	return NULL;

    /* We're ready to start outputting. First write the header,
     * i.e. the public part of the font dict.*/
    if (cairo_type1_font_subset_write_header (font, name))
	return NULL;

    font->base.header_size = _cairo_output_stream_get_position (font->output);


    /* Start outputting the private dict.  First output everything up
     * to the /CharStrings token. */
    cairo_type1_font_subset_write_encrypted (font, font->cleartext,
					     charstrings - font->cleartext);

    /* Write out new charstring count */
    length = snprintf (buffer, sizeof buffer,
		       "/CharStrings %d", font->num_glyphs);
    cairo_type1_font_subset_write_encrypted (font, buffer, length);

    /* Write out text between the charstring count and the first
     * charstring definition */
    cairo_type1_font_subset_write_encrypted (font, glyph_count_end,
					     dict_start - glyph_count_end);

    /* Write out the charstring definitions for each of the glyphs in
     * the subset. */
    p = cairo_type1_font_subset_for_each_glyph (font,
						dict_start,
						font->cleartext_end,
						write_used_glyphs);

    /* Output what's left between the end of the glyph definitions and
     * the end of the private dict to the output. */
    cairo_type1_font_subset_write_encrypted (font, p,
					     closefile_token - p + strlen ("closefile") + 1);
    _cairo_output_stream_write (font->output, "\n", 1);

    return p;
}

static cairo_status_t
cairo_type1_font_subset_write_trailer(cairo_type1_font_subset_t *font)
{
    const char *cleartomark_token;
    int i;
    static const char zeros[65] =
	"0000000000000000000000000000000000000000000000000000000000000000\n";

    /* Some fonts have conditional save/restore around the entire font
     * dict, so we need to retain whatever postscript code that may
     * come after 'cleartomark'. */

    for (i = 0; i < 8; i++)
	_cairo_output_stream_write (font->output, zeros, sizeof zeros);

    cleartomark_token = find_token (font->type1_data, font->type1_end, "cleartomark");
    if (cleartomark_token == NULL)
	return font->status = CAIRO_INT_STATUS_UNSUPPORTED;

    _cairo_output_stream_write (font->output, cleartomark_token,
				font->type1_end - cleartomark_token);

    return font->status;
}

static cairo_status_t
type1_font_write (void *closure, const unsigned char *data, unsigned int length)
{
    cairo_type1_font_subset_t *font = closure;

    font->status =
	_cairo_array_append_multiple (&font->contents, data, length);

    return font->status;
}

static cairo_status_t
cairo_type1_font_subset_write (cairo_type1_font_subset_t *font,
			       const char *name)
{
    if (cairo_type1_font_subset_find_segments (font))
	return font->status;

    if (cairo_type1_font_subset_decrypt_eexec_segment (font))
	return font->status;

    /* Determine which glyph definition delimiters to use. */
    if (find_token (font->cleartext, font->cleartext_end, "/-|") != NULL) {
	font->rd = "-|";
	font->nd = "|-";
    } else if (find_token (font->cleartext, font->cleartext_end, "/RD") != NULL) {
	font->rd = "RD";
	font->nd = "ND";
    } else {
	/* Don't know *what* kind of font this is... */
	return font->status = CAIRO_INT_STATUS_UNSUPPORTED;
    }

    font->eexec_key = private_dict_key;
    font->hex_encode = TRUE;
    font->hex_column = 0;

    cairo_type1_font_subset_write_private_dict (font, name);

    font->base.data_size = _cairo_output_stream_get_position (font->output) -
	font->base.header_size;

    cairo_type1_font_subset_write_trailer (font);

    font->base.trailer_size =
	_cairo_output_stream_get_position (font->output) -
	font->base.header_size - font->base.data_size;

    return font->status;
}

static cairo_status_t
cairo_type1_font_subset_generate (void       *abstract_font,
				  const char *name)

{
    cairo_type1_font_subset_t *font = abstract_font;
    cairo_ft_unscaled_font_t *ft_unscaled_font;
    unsigned long ret;

    ft_unscaled_font = (cairo_ft_unscaled_font_t *) font->base.unscaled_font;
    font->face = _cairo_ft_unscaled_font_lock_face (ft_unscaled_font);

    /* If anything fails below, it's out of memory. */
    font->status = CAIRO_STATUS_NO_MEMORY;

    font->type1_length = font->face->stream->size;
    font->type1_data = malloc (font->type1_length);
    if (font->type1_data == NULL)
	goto fail;

    if (font->face->stream->read) {
	ret = font->face->stream->read (font->face->stream, 0,
					(unsigned char *) font->type1_data,
					font->type1_length);
	if (ret != font->type1_length)
	    goto fail;
    } else {
	memcpy (font->type1_data,
		font->face->stream->base, font->type1_length);
    }

    if (_cairo_array_grow_by (&font->contents, 4096) != CAIRO_STATUS_SUCCESS)
	goto fail;

    font->output = _cairo_output_stream_create (type1_font_write, NULL, font);
    if (font->output == NULL)
	goto fail;

    font->status = CAIRO_STATUS_SUCCESS;
    cairo_type1_font_subset_write (font, name);

    font->base.data = _cairo_array_index (&font->contents, 0);

 fail:
    _cairo_ft_unscaled_font_unlock_face (ft_unscaled_font);

    return font->status;
}

static void
cairo_type1_font_subset_destroy (void *abstract_font)
{
    cairo_type1_font_subset_t *font = abstract_font;
    int i;

    /* If the subset generation failed, some of the pointers below may
     * be NULL depending on at which point the error occurred. */

    _cairo_array_fini (&font->contents);

    free (font->type1_data);
    if (font->glyphs != NULL)
	for (i = 0; i < font->base.num_glyphs; i++) {
	    free (font->glyphs[i].name);
	}

    _cairo_unscaled_font_destroy (font->base.unscaled_font);

    free (font->base.base_font);
    free (font->glyphs);
    free (font);
}


cairo_status_t
_cairo_type1_subset_init (cairo_type1_subset_t		*type1_subset,
			  const char			*name,
			  cairo_scaled_font_subset_t	*scaled_font_subset)
{
    cairo_type1_font_subset_t *font;
    cairo_status_t status;
    unsigned long parent_glyph, length;
    int i;
    cairo_unscaled_font_t *unscaled_font;

    /* XXX: Need to fix this to work with a general cairo_unscaled_font_t. */
    if (!_cairo_scaled_font_is_ft (scaled_font_subset->scaled_font))
	return CAIRO_INT_STATUS_UNSUPPORTED;

    unscaled_font = _cairo_ft_scaled_font_get_unscaled_font (scaled_font_subset->scaled_font);

    status = _cairo_type1_font_subset_create (unscaled_font, &font);
    if (status)
	return status;

    for (i = 0; i < scaled_font_subset->num_glyphs; i++) {
	parent_glyph = scaled_font_subset->glyphs[i];
	cairo_type1_font_subset_use_glyph (font, parent_glyph);
    }

    /* Pull in the .notdef glyph */
    cairo_type1_font_subset_use_glyph (font, 0);

    status = cairo_type1_font_subset_generate (font, name);
    if (status)
	goto fail1;

    type1_subset->base_font = strdup (font->base.base_font);
    if (type1_subset->base_font == NULL)
	goto fail1;

    type1_subset->widths = calloc (sizeof (int), font->num_glyphs);
    if (type1_subset->widths == NULL)
	goto fail2;
    for (i = 0; i < font->base.num_glyphs; i++) {
	if (font->glyphs[i].subset_index < 0)
	    continue;
	type1_subset->widths[font->glyphs[i].subset_index] =
	    font->glyphs[i].width;
    }

    type1_subset->x_min = font->base.x_min;
    type1_subset->y_min = font->base.y_min;
    type1_subset->x_max = font->base.x_max;
    type1_subset->y_max = font->base.y_max;
    type1_subset->ascent = font->base.ascent;
    type1_subset->descent = font->base.descent;

    length = font->base.header_size + font->base.data_size +
	font->base.trailer_size;
    type1_subset->data = malloc (length);
    if (type1_subset->data == NULL)
	goto fail3;

    memcpy (type1_subset->data,
	    _cairo_array_index (&font->contents, 0), length);

    type1_subset->header_length = font->base.header_size;
    type1_subset->data_length = font->base.data_size;
    type1_subset->trailer_length = font->base.trailer_size;

    cairo_type1_font_subset_destroy (font);

    return CAIRO_STATUS_SUCCESS;

 fail3:
    free (type1_subset->widths);
 fail2:
    free (type1_subset->base_font);
 fail1:
    cairo_type1_font_subset_destroy (font);

    return status;
}

void
_cairo_type1_subset_fini (cairo_type1_subset_t *subset)
{
    free (subset->base_font);
    free (subset->widths);
    free (subset->data);
}