From 71d03c72818f36275d47ee0fe63c9ebb27fd0829 Mon Sep 17 00:00:00 2001
From: Werner Almesberger <werner@almesberger.net>
Date: Sun, 21 Aug 2016 11:34:12 -0300
Subject: [PATCH] eeshow/gfx/pdftoc.c: edit Cairo-generated PDF to insert TOC

Based on schtoc.pl
---
 eeshow/Makefile     |   2 +-
 eeshow/gfx/pdftoc.c | 346 ++++++++++++++++++++++++++++++++++++++++++++
 eeshow/gfx/pdftoc.h |  27 ++++
 3 files changed, 374 insertions(+), 1 deletion(-)
 create mode 100644 eeshow/gfx/pdftoc.c
 create mode 100644 eeshow/gfx/pdftoc.h

diff --git a/eeshow/Makefile b/eeshow/Makefile
index ff4c14b..db3a01b 100644
--- a/eeshow/Makefile
+++ b/eeshow/Makefile
@@ -21,7 +21,7 @@ OBJS = main.o version.o \
        gui/help.o gui/icons.o \
        file/file.o file/git-util.o file/git-file.o file/git-hist.o \
        gfx/style.o gfx/fig.o gfx/record.o gfx/cro.o gfx/diff.o gfx/gfx.o \
-       gfx/text.o gfx/misc.o \
+       gfx/text.o gfx/misc.o gfx/pdftoc.o \
        misc/diag.o
 
 ICONS = delta diff
diff --git a/eeshow/gfx/pdftoc.c b/eeshow/gfx/pdftoc.c
new file mode 100644
index 0000000..5324823
--- /dev/null
+++ b/eeshow/gfx/pdftoc.c
@@ -0,0 +1,346 @@
+/*
+ * gfx/pdftoc.c - PDF writer with TOC generation
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+/*
+ * Strongly influenced by https://neo900.org/git?p=misc;a=tree;f=schtoc
+ *
+ * PDF Reference:
+ * http://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf
+ */
+
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include "misc/util.h"
+#include "misc/diag.h"
+#include "gfx/pdftoc.h"
+
+
+struct title {
+	char *s;
+	struct title *next;
+};
+
+struct object {
+	int gen;
+	unsigned pos;
+	bool is_page;
+};
+
+struct pdftoc {
+	FILE *file;
+
+	enum state {
+		idle,	/* between objects */
+		object,	/* inside an object */
+		catalog,/* inside the catalog object */
+		xref,	/* stopped at xref */
+		trailer,/* going through the trailer */
+	} state;
+
+	struct title *titles;
+	struct title **next_title;
+	unsigned n_titles;
+
+	char *buf;
+	unsigned left;		/* bytes left in buffer */
+	unsigned offset;	/* offset into buffer */
+	unsigned pos;		/* position in file */
+
+	struct object *objs;	/* object array */
+	struct object *curr_obj;
+	int top;		/* highest object number; -1 if no objects */
+
+	int root;		/* catalog dict */
+	int info;		/* information dict, 0 if absent */
+};
+
+
+static bool begins(const char *s, const char *pfx)
+{
+	return !strncmp(s, pfx, strlen(pfx));
+}
+
+
+struct pdftoc *pdftoc_begin(const char *file)
+{
+	struct pdftoc *ctx;
+
+	ctx = alloc_type(struct pdftoc);
+	if (file) {
+		ctx->file = fopen(file, "w");
+		if (!ctx->file)
+			diag_pfatal(file);
+	} else {
+		ctx->file = stdout;
+	}
+
+	ctx->state = idle;
+
+	ctx->titles = NULL;
+	ctx->next_title = &ctx->titles;
+	ctx->n_titles = 0;
+
+	ctx->buf = NULL;
+	ctx->left = 0;
+	ctx->offset = 0;
+	ctx->pos = 0;
+
+	ctx->objs = NULL;
+	ctx->top = -1;
+
+	ctx->root = 0;
+	ctx->info = 0;
+
+	return ctx;
+}
+
+
+static void add_object(struct pdftoc *ctx, int id, int gen, unsigned pos)
+{
+	struct object *obj;
+
+	if (id > ctx->top) {
+		ctx->objs = realloc(ctx->objs,
+		    (id + 1) * sizeof(struct object));
+		memset(ctx->objs + ctx->top + 1 , 0,
+		    (id - ctx->top) * sizeof(struct object));
+		ctx->top = id;
+	}
+
+	obj = ctx->objs + id;
+	ctx->curr_obj = obj;
+	obj->gen = gen;
+	obj->pos = pos;
+	obj->is_page = 0;
+}
+
+
+static bool parse_object(struct pdftoc *ctx, const char *s)
+{
+	int id, gen;
+	int n = 0;
+
+	if (sscanf(s, "%d %d obj%n", &id, &gen, &n) != 2 || !n)
+		return 0;
+	add_object(ctx, id, gen, ctx->pos);
+	return 1;
+}
+
+
+static void line(struct pdftoc *ctx, const char *s)
+{
+
+	switch (ctx->state) {
+	case idle:
+		if (parse_object(ctx, s)) {
+			ctx->state = object;
+			break;
+		}
+		if (begins(s, "xref")) {
+			ctx->state = xref;
+			break;
+		}
+		break;
+	case object:
+		if (begins(s, "endobj")) {
+			ctx->state = idle;
+			break;
+		}
+		if (begins(s, "<< /Type /Page")) {
+			ctx->curr_obj->is_page = 1;
+			break;
+		}
+		if (begins(s, "<< /Type /Catalog")) {
+			ctx->state = catalog;
+			break;
+		}
+		break;
+	case catalog:
+		if (begins(s, ">>")) {
+			ctx->state = object;
+			ctx->pos += fprintf(ctx->file,
+			    "   /Outlines %u 0 R\n",
+			    ctx->top + 1);
+			break;
+		}
+		break;
+	case xref:
+		abort();
+	case trailer:
+		if (sscanf(s, "   /Root %d 0 R", &ctx->root) == 1)
+			break;
+		if (sscanf(s, "   /Info %d 0 R", &ctx->info) == 1)
+			break;
+		break;
+	default:
+		abort();
+	}
+}
+
+
+static void parse_buffer(struct pdftoc *ctx, bool do_write)
+{
+	unsigned size, wrote;
+	char *nl;
+
+	while (ctx->state != xref) {
+		nl = memchr(ctx->buf + ctx->offset, '\n', ctx->left);
+		if (!nl)
+			break;
+		*nl = 0;
+		size = nl - (ctx->buf + ctx->offset);
+		line(ctx, ctx->buf + ctx->offset);
+		*nl = '\n';
+		if (ctx->state == xref)
+			break;
+		if (do_write) {
+			wrote = fwrite(ctx->buf + ctx->offset, 1, size + 1,
+			    ctx->file);
+			if (wrote != size + 1)
+				diag_pfatal("fwrite");
+			ctx->pos += size + 1;
+		}
+		ctx->offset += size + 1;
+		ctx->left -= size + 1;
+	}
+}
+
+
+bool pdftoc_write(struct pdftoc *ctx, const void *data, unsigned length)
+{
+	char *buf;
+
+	buf = alloc_size(ctx->left + length + 1);
+	memcpy(buf, ctx->buf + ctx->offset, ctx->left);
+	memcpy(buf + ctx->left, data, length);
+	ctx->offset = 0;
+	ctx->left += length;
+	free(ctx->buf);
+	ctx->buf = buf;
+
+	parse_buffer(ctx, 1);
+
+	return 1;
+}
+
+
+void pdftoc_title(struct pdftoc *ctx, const char *title)
+{
+	struct title *t;
+
+	t = alloc_type(struct title);
+	t->s = stralloc(title);
+	*ctx->next_title = t;
+	t->next = NULL;
+	ctx->next_title = &t->next;
+	ctx->n_titles++;
+}
+
+
+static void write_trailer(struct pdftoc *ctx)
+{
+	unsigned n = ctx->top + 1;
+	const struct object *obj = ctx->objs;
+	const struct object *end = ctx->objs + ctx->top + 1;
+	const struct title *t;
+	unsigned outline, tail;
+
+	/* Outline root */
+
+	outline = n;
+	add_object(ctx, n, 0, ctx->pos);
+	tail = fprintf(ctx->file,
+	    "%u 0 obj\n<<\n"
+	    "   /Count %u\n"
+	    "   /First %u 0 R\n"
+	    "   /Last %u 0 R\n"
+	    ">>\nendobj\n",
+	    n, ctx->n_titles, n + 1, n + ctx->n_titles);
+
+	/* Outline items */
+
+	n++;
+	for (t = ctx->titles; t; t = t->next) {
+		while (!obj->is_page) {
+			assert(obj != end);
+			obj++;
+		}
+		add_object(ctx, n, 0, ctx->pos + tail);
+		tail += fprintf(ctx->file,
+		    "%u 0 obj\n<<\n"
+		    "   /Title (%s)\n"
+		    "   /Parent %u 0 R\n",
+		    n, t->s, outline);
+		if (t != ctx->titles)
+			tail += fprintf(ctx->file,
+			    "   /Prev %u 0 R\n", n - 1);
+		if (t->next)
+			tail += fprintf(ctx->file,
+			    "   /Next %u 0 R\n", n + 1);
+		tail += fprintf(ctx->file,
+		    "   /Dest [%u %u R /Fit]\n"
+		    ">>\nendobj\n",
+		    (unsigned) (obj - ctx->objs), obj->gen);
+		n++;
+		obj++;
+	}
+
+	/* xref table */
+
+	fprintf(ctx->file, "xref\n0 %u\n", n);
+	for (obj = ctx->objs; obj != ctx->objs + ctx->top + 1; obj++)
+		fprintf(ctx->file,
+		    "%010u %05u %c \n",
+		    obj->pos, obj->pos ? 0 : 65535, obj->pos ? 'n' : 'f');
+
+	fprintf(ctx->file,
+	    "trailer\n"
+	    "<< /Size %u\n"
+	    "   /Root %u 0 R\n",
+	    n, ctx->root);
+	if (ctx->info)
+		fprintf(ctx->file, "   /Info %u 0 R\n", ctx->info);
+	fprintf(ctx->file, ">>\nstartxref\n%u\n%%%%EOF\n", ctx->pos + tail);
+}
+
+
+void pdftoc_end(struct pdftoc *ctx)
+{
+	struct title *next;
+
+	assert(ctx->state == xref);
+	ctx->state = trailer;
+	parse_buffer(ctx, 0);
+	if (ctx->left) {
+		fatal("%u bytes left in buffer at end\n", ctx->left);
+		exit(1);
+	}
+
+	write_trailer(ctx);
+
+	if (fclose(ctx->file) < 0)
+		diag_pfatal("fclose");
+
+	while (ctx->titles) {
+		next = ctx->titles->next;
+		free(ctx->titles->s);
+		free(ctx->titles);
+		ctx->titles = next;
+	}
+	free(ctx->buf);
+	free(ctx);
+}
diff --git a/eeshow/gfx/pdftoc.h b/eeshow/gfx/pdftoc.h
new file mode 100644
index 0000000..8ccdbe5
--- /dev/null
+++ b/eeshow/gfx/pdftoc.h
@@ -0,0 +1,27 @@
+/*
+ * gfx/pdftoc.h - PDF writer with TOC generation
+ *
+ * Written 2016 by Werner Almesberger
+ * Copyright 2016 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#ifndef GFX_PDFTOC_H
+#define	GFX_PDFTOC_H
+
+#include <stdbool.h>
+
+
+struct pdftoc;
+
+struct pdftoc *pdftoc_begin(const char *file);
+bool pdftoc_write(struct pdftoc *ctx, const void *data, unsigned length);
+void pdftoc_title(struct pdftoc *ctx, const char *title);
+void pdftoc_end(struct pdftoc *ctx);
+
+#endif /* !GFX_PDFTOC_H */