Rework pdf_store to fz_store, a part of fz_context.

Firstly, we rename pdf_store to fz_store, reflecting the fact that
there are no pdf specific dependencies on it.

Next, we rework it so that all the objects that can be stored in
the store start with an fz_storable structure. This consists of
a reference count, and a function used to free the object when
the reference count reaches zero.

All the keep/drop functions are then reimplemented by calling
fz_keep_sharable/fz_drop_sharable. The 'drop' functions as supplied
by the callers are thus now 'free' functions, only called if
the reference count drops to 0.

The store changes to keep all the items in the store in the linked
list (which becomes a doubly linked one). We still make use of
the hashtable to index into this list quickly, but we now have
the objects in an LRU ordering within the list.

Every object is put into the store, with a size record; this is
an estimate of how much memory would be freed by freeing that
object.

The store is moved into the context and given a maximum size;
when new things are inserted into the store, care is taken to
ensure that we do not expand beyond this size. We evict any
stored items (that are not in use) starting from the least
recently used.

Finding an object in the store now takes a reference to it already.

LOCK and UNLOCK comments are used to indicate where locks need to
be taken and released to ensure thread safety.

1 files changed, 32 insertions, 22 deletions

diff --git a/pdf/pdf_font.c b/pdf/pdf_font.c
index dfd4782c..ae24df0f 100644
--- a/pdf/pdf_font.c
+++ b/pdf/pdf_font.c
@@ -198,6 +198,7 @@ pdf_load_substitute_font(fz_context *ctx, pdf_font_desc *fontdesc, int mono, int
 		fz_throw(ctx, "cannot find substitute font");
 
 	fontdesc->font = fz_new_font_from_memory(ctx, data, len, 0);
+	fontdesc->size += len;
 	/* RJW: "cannot load freetype font from memory" */
 
 	fontdesc->font->ft_substitute = 1;
@@ -216,6 +217,7 @@ pdf_load_substitute_cjk_font(fz_context *ctx, pdf_font_desc *fontdesc, int ros,
 		fz_throw(ctx, "cannot find builtin CJK font");
 
 	fontdesc->font = fz_new_font_from_memory(ctx, data, len, 0);
+	fontdesc->size += len;
 	/* RJW: "cannot load builtin CJK font" */
 
 	fontdesc->font->ft_substitute = 1;
@@ -288,6 +290,7 @@ pdf_load_embedded_font(pdf_font_desc *fontdesc, pdf_xref *xref, fz_obj *stmref)
 		fz_drop_buffer(ctx, buf);
 		fz_throw(ctx, "cannot load embedded font (%d %d R)", fz_to_num(stmref), fz_to_gen(stmref));
 	}
+	fontdesc->size += buf->len;
 
 	/* save the buffer so we can free it later */
 	fontdesc->font->ft_data = buf->data;
@@ -304,29 +307,31 @@ pdf_load_embedded_font(pdf_font_desc *fontdesc, pdf_xref *xref, fz_obj *stmref)
 pdf_font_desc *
 pdf_keep_font(pdf_font_desc *fontdesc)
 {
-	fontdesc->refs ++;
-	return fontdesc;
+	return (pdf_font_desc *)fz_keep_storable(&fontdesc->storable);
 }
 
 void
 pdf_drop_font(fz_context *ctx, pdf_font_desc *fontdesc)
 {
-	if (fontdesc && --fontdesc->refs == 0)
-	{
-		if (fontdesc->font)
-			fz_drop_font(ctx, fontdesc->font);
-		if (fontdesc->encoding)
-			pdf_drop_cmap(ctx, fontdesc->encoding);
-		if (fontdesc->to_ttf_cmap)
-			pdf_drop_cmap(ctx, fontdesc->to_ttf_cmap);
-		if (fontdesc->to_unicode)
-			pdf_drop_cmap(ctx, fontdesc->to_unicode);
-		fz_free(ctx, fontdesc->cid_to_gid);
-		fz_free(ctx, fontdesc->cid_to_ucs);
-		fz_free(ctx, fontdesc->hmtx);
-		fz_free(ctx, fontdesc->vmtx);
-		fz_free(ctx, fontdesc);
-	}
+	fz_drop_storable(ctx, &fontdesc->storable);
+}
+
+static void
+pdf_free_font_imp(fz_context *ctx, pdf_font_desc *fontdesc)
+{
+	if (fontdesc->font)
+		fz_drop_font(ctx, fontdesc->font);
+	if (fontdesc->encoding)
+		pdf_drop_cmap(ctx, fontdesc->encoding);
+	if (fontdesc->to_ttf_cmap)
+		pdf_drop_cmap(ctx, fontdesc->to_ttf_cmap);
+	if (fontdesc->to_unicode)
+		pdf_drop_cmap(ctx, fontdesc->to_unicode);
+	fz_free(ctx, fontdesc->cid_to_gid);
+	fz_free(ctx, fontdesc->cid_to_ucs);
+	fz_free(ctx, fontdesc->hmtx);
+	fz_free(ctx, fontdesc->vmtx);
+	fz_free(ctx, fontdesc);
 }
 
 pdf_font_desc *
@@ -335,7 +340,8 @@ pdf_new_font_desc(fz_context *ctx)
 	pdf_font_desc *fontdesc;
 
 	fontdesc = fz_malloc(ctx, sizeof(pdf_font_desc));
-	fontdesc->refs = 1;
+	FZ_INIT_STORABLE(fontdesc, 1, pdf_free_font_imp);
+	fontdesc->size = sizeof(pdf_font_desc);
 
 	fontdesc->font = NULL;
 
@@ -497,6 +503,7 @@ pdf_load_simple_font(pdf_xref *xref, fz_obj *dict)
 			fz_warn(ctx, "freetype could not find any cmaps");
 
 		etable = fz_malloc_array(ctx, 256, sizeof(unsigned short));
+		fontdesc->size += 256 * sizeof(unsigned short);
 		for (i = 0; i < 256; i++)
 		{
 			estrings[i] = NULL;
@@ -637,6 +644,7 @@ pdf_load_simple_font(pdf_xref *xref, fz_obj *dict)
 		}
 
 		fontdesc->encoding = pdf_new_identity_cmap(ctx, 0, 1);
+		fontdesc->size += pdf_cmap_size(fontdesc->encoding);
 		fontdesc->cid_to_gid_len = 256;
 		fontdesc->cid_to_gid = etable;
 
@@ -771,6 +779,7 @@ load_cid_font(pdf_xref *xref, fz_obj *dict, fz_obj *encoding, fz_obj *to_unicode
 		{
 			fz_throw(ctx, "syntaxerror: font missing encoding");
 		}
+		fontdesc->size += pdf_cmap_size(fontdesc->encoding);
 
 		pdf_set_font_wmode(fontdesc, pdf_get_wmode(fontdesc->encoding));
 
@@ -787,6 +796,7 @@ load_cid_font(pdf_xref *xref, fz_obj *dict, fz_obj *encoding, fz_obj *to_unicode
 
 				fontdesc->cid_to_gid_len = (buf->len) / 2;
 				fontdesc->cid_to_gid = fz_malloc_array(ctx, fontdesc->cid_to_gid_len, sizeof(unsigned short));
+				fontdesc->size += fontdesc->cid_to_gid_len * sizeof(unsigned short);
 				for (i = 0; i < fontdesc->cid_to_gid_len; i++)
 					fontdesc->cid_to_gid[i] = (buf->data[i * 2] << 8) + buf->data[i * 2 + 1];
 
@@ -1040,6 +1050,7 @@ pdf_make_width_table(fz_context *ctx, pdf_font_desc *fontdesc)
 	font->width_count ++;
 
 	font->width_table = fz_malloc_array(ctx, font->width_count, sizeof(int));
+	fontdesc->size += font->width_count * sizeof(int);
 
 	for (i = 0; i < fontdesc->hmtx_len; i++)
 	{
@@ -1062,9 +1073,8 @@ pdf_load_font(pdf_xref *xref, fz_obj *rdb, fz_obj *dict)
 	fz_context *ctx = xref->ctx;
 	pdf_font_desc *fontdesc;
 
-	if ((fontdesc = pdf_find_item(ctx, xref->store, (pdf_store_drop_fn *)pdf_drop_font, dict)))
+	if ((fontdesc = fz_find_item(ctx, pdf_free_font_imp, dict)))
 	{
-		pdf_keep_font(fontdesc);
 		return fontdesc;
 	}
 
@@ -1103,7 +1113,7 @@ pdf_load_font(pdf_xref *xref, fz_obj *rdb, fz_obj *dict)
 	if (fontdesc->font->ft_substitute && !fontdesc->to_ttf_cmap)
 		pdf_make_width_table(ctx, fontdesc);
 
-	pdf_store_item(ctx, xref->store, (pdf_store_keep_fn *)pdf_keep_font, (pdf_store_drop_fn *)pdf_drop_font, dict, fontdesc);
+	fz_store_item(ctx, dict, fontdesc, fontdesc->size);
 
 	return fontdesc;
 }