ps_include.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <stdio.h>
#include "../common/common.h"
#include "ps_include.h"

extern int curpostfontid;
extern int curfontsize;

typedef struct {long start, end;} Section;
static char *buf;

static
copy(Biobufhdr *fin, Biobufhdr *fout, Section *s) {
	int cond;
	if (s->end <= s->start)
		return;
	Bseek(fin, s->start, 0);
	while (Bseek(fin, 0L, 1) < s->end && (buf=Brdline(fin, '\n')) != NULL){
		/*
		 * We have to be careful here, because % can legitimately appear
		 * in Ascii85 encodings, and must not be elided.
		 * The goal here is to make any DSC comments impotent without
		 * actually changing the behavior of the Postscript.
		 * Since stripping ``comments'' breaks Ascii85, we can instead just
		 * indent comments a space, which turns DSC comments into non-DSC comments
		 * and has no effect on binary encodings, which are whitespace-blind.
		 */
		if(buf[0] == '%')
			Bputc(fout, ' ');
		Bwrite(fout, buf, Blinelen(fin));
	}
}

/*
 *
 * Reads a PostScript file (*fin), and uses structuring comments to locate the
 * prologue, trailer, global definitions, and the requested page. After the whole
 * file is scanned, the  special ps_include PostScript definitions are copied to
 * *fout, followed by the prologue, global definitions, the requested page, and
 * the trailer. Before returning the initial environment (saved in PS_head) is
 * restored.
 *
 * By default we assume the picture is 8.5 by 11 inches, but the BoundingBox
 * comment, if found, takes precedence.
 *
 */
/*	*fin, *fout;		/* input and output files */
/*	page_no;		/* physical page number from *fin */
/*	whiteout;		/* erase picture area */
/*	outline;		/* draw a box around it and */
/*	scaleboth;		/* scale both dimensions - if not zero */
/*	cx, cy;			/* center of the picture and */
/*	sx, sy;			/* its size - in current coordinates */
/*	ax, ay;			/* left-right, up-down adjustment */
/*	rot;			/* rotation - in clockwise degrees */

void
ps_include(Biobufhdr *fin, Biobufhdr *fout, int page_no, int whiteout,
	int outline, int scaleboth, double cx, double cy, double sx, double sy,
	double ax, double ay, double rot) {
	char		**strp;
	int		foundpage = 0;		/* found the page when non zero */
	int		foundpbox = 0;		/* found the page bounding box */
	int		nglobal = 0;		/* number of global defs so far */
	int		maxglobal = 0;		/* and the number we've got room for */
	Section	prolog, page, trailer;	/* prologue, page, and trailer offsets */
	Section	*global;		/* offsets for all global definitions */
	double	llx, lly;		/* lower left and */
	double	urx, ury;		/* upper right corners - default coords */
	double	w = whiteout != 0;	/* mostly for the var() macro */
	double	o = outline != 0;
	double	s = scaleboth != 0;
	int		i;		/* loop index */

#define has(word)	(strncmp(buf, word, strlen(word)) == 0)
#define grab(n)		((Section *)(nglobal \
			? realloc((char *)global, n*sizeof(Section)) \
			: calloc(n, sizeof(Section))))

	llx = lly = 0;		/* default BoundingBox - 8.5x11 inches */
	urx = 72 * 8.5;
	ury = 72 * 11.0;

	/* section boundaries and bounding box */

	prolog.start = prolog.end = 0;
	page.start = page.end = 0;
	trailer.start = 0;
	Bseek(fin, 0L, 0);

	while ((buf=Brdline(fin, '\n')) != NULL) {
		buf[Blinelen(fin)-1] = '\0';
		if (!has("%%"))
			continue;
		else if (has("%%Page: ")) {
			if (!foundpage)
				page.start = Bseek(fin, 0L, 1);
			sscanf(buf, "%*s %*s %d", &i);
			if (i == page_no)
				foundpage = 1;
			else if (foundpage && page.end <= page.start)
				page.end = Bseek(fin, 0L, 1);
		} else if (has("%%EndPage: ")) {
			sscanf(buf, "%*s %*s %d", &i);
			if (i == page_no) {
				foundpage = 1;
				page.end = Bseek(fin, 0L, 1);
			}
			if (!foundpage)
				page.start = Bseek(fin, 0L, 1);
		} else if (has("%%PageBoundingBox: ")) {
			if (i == page_no) {
				foundpbox = 1;
				sscanf(buf, "%*s %lf %lf %lf %lf",
						&llx, &lly, &urx, &ury);
			}
		} else if (has("%%BoundingBox: ")) {
			if (!foundpbox)
				sscanf(buf,"%*s %lf %lf %lf %lf",
						&llx, &lly, &urx, &ury);
		} else if (has("%%EndProlog") || has("%%EndSetup") || has("%%EndDocumentSetup"))
			prolog.end = page.start = Bseek(fin, 0L, 1);
		else if (has("%%Trailer"))
			trailer.start = Bseek(fin, 0L, 1);
		else if (has("%%BeginGlobal")) {
			if (page.end <= page.start) {
				if (nglobal >= maxglobal) {
					maxglobal += 20;
					global = grab(maxglobal);
				}
				global[nglobal].start = Bseek(fin, 0L, 1);
			}
		} else if (has("%%EndGlobal"))
			if (page.end <= page.start)
				global[nglobal++].end = Bseek(fin, 0L, 1);
	}
	Bseek(fin, 0L, 2);
	if (trailer.start == 0)
		trailer.start = Bseek(fin, 0L, 1);
	trailer.end = Bseek(fin, 0L, 1);

	if (page.end <= page.start)
		page.end = trailer.start;

/*
fprint(2, "prolog=(%d,%d)\n", prolog.start, prolog.end);
fprint(2, "page=(%d,%d)\n", page.start, page.end);
for(i = 0; i < nglobal; i++)
	fprint(2, "global[%d]=(%d,%d)\n", i, global[i].start, global[i].end);
fprint(2, "trailer=(%d,%d)\n", trailer.start, trailer.end);
*/

	/* all output here */
	for (strp = PS_head; *strp != NULL; strp++)
		Bwrite(fout, *strp, strlen(*strp));

	Bprint(fout, "/llx %g def\n", llx);
	Bprint(fout, "/lly %g def\n", lly);
	Bprint(fout, "/urx %g def\n", urx);
	Bprint(fout, "/ury %g def\n", ury);
	Bprint(fout, "/w %g def\n", w);
	Bprint(fout, "/o %g def\n", o);
	Bprint(fout, "/s %g def\n", s);
	Bprint(fout, "/cx %g def\n", cx);
	Bprint(fout, "/cy %g def\n", cy);
	Bprint(fout, "/sx %g def\n", sx);
	Bprint(fout, "/sy %g def\n", sy);
	Bprint(fout, "/ax %g def\n", ax);
	Bprint(fout, "/ay %g def\n", ay);
	Bprint(fout, "/rot %g def\n", rot);

	for (strp = PS_setup; *strp != NULL; strp++)
		Bwrite(fout, *strp, strlen(*strp));

	copy(fin, fout, &prolog);
	for(i = 0; i < nglobal; i++)
		copy(fin, fout, &global[i]);
	copy(fin, fout, &page);
	copy(fin, fout, &trailer);
	for (strp = PS_tail; *strp != NULL; strp++)
		Bwrite(fout, *strp, strlen(*strp));

	if(nglobal)
		free(global);

	/* force the program to reestablish its state */
	curpostfontid = -1;
	curfontsize = -1;
}