Multi-threading support for MuPDF

When we moved over to a context based system, we laid the foundation
for a thread-safe mupdf. This commit should complete that process.

Firstly, fz_clone_context is properly implemented so that it
makes a new context, but shares certain sections (currently
just the allocator, and the store).

Secondly, we add locking (to parts of the code that have
previously just had placeholder LOCK/UNLOCK comments). Functions
to lock and unlock a mutex are added to the allocator structure;
omit these (as is the case today) and no multithreading is
(safely) possible. The context will refuse to clone if these are
not provided.

Finally we flesh out the LOCK/UNLOCK comments to be real calls of
the functions - unfortunately this requires us to plumb fz_context
into the fz_keep_storable function (and all the fz_keep_xxx
functions that call it). This is the largest section of the patch.

No changes expected to any test files.

8 files changed, 41 insertions, 41 deletions

diff --git a/pdf/mupdf.h b/pdf/mupdf.h
index 0e21f930..b1b2a7e1 100644
--- a/pdf/mupdf.h
+++ b/pdf/mupdf.h
@@ -159,7 +159,7 @@ typedef struct pdf_function_s pdf_function;
 
 pdf_function *pdf_load_function(pdf_xref *xref, fz_obj *ref);
 void pdf_eval_function(fz_context *ctx, pdf_function *func, float *in, int inlen, float *out, int outlen);
-pdf_function *pdf_keep_function(pdf_function *func);
+pdf_function *pdf_keep_function(fz_context *ctx, pdf_function *func);
 void pdf_drop_function(fz_context *ctx, pdf_function *func);
 unsigned int pdf_function_size(pdf_function *func);
 
@@ -191,7 +191,7 @@ struct pdf_pattern_s
 };
 
 pdf_pattern *pdf_load_pattern(pdf_xref *xref, fz_obj *obj);
-pdf_pattern *pdf_keep_pattern(pdf_pattern *pat);
+pdf_pattern *pdf_keep_pattern(fz_context *ctx, pdf_pattern *pat);
 void pdf_drop_pattern(fz_context *ctx, pdf_pattern *pat);
 
 /*
@@ -215,7 +215,7 @@ struct pdf_xobject_s
 };
 
 pdf_xobject *pdf_load_xobject(pdf_xref *xref, fz_obj *obj);
-pdf_xobject *pdf_keep_xobject(pdf_xobject *xobj);
+pdf_xobject *pdf_keep_xobject(fz_context *ctx, pdf_xobject *xobj);
 void pdf_drop_xobject(fz_context *ctx, pdf_xobject *xobj);
 
 /*
@@ -263,7 +263,7 @@ struct pdf_cmap_s
 };
 
 pdf_cmap *pdf_new_cmap(fz_context *ctx);
-pdf_cmap *pdf_keep_cmap(pdf_cmap *cmap);
+pdf_cmap *pdf_keep_cmap(fz_context *ctx, pdf_cmap *cmap);
 void pdf_drop_cmap(fz_context *ctx, pdf_cmap *cmap);
 void pdf_free_cmap_imp(fz_context *ctx, fz_storable *cmap);
 unsigned int pdf_cmap_size(pdf_cmap *cmap);
@@ -401,7 +401,7 @@ pdf_font_desc *pdf_load_type3_font(pdf_xref *xref, fz_obj *rdb, fz_obj *obj);
 pdf_font_desc *pdf_load_font(pdf_xref *xref, fz_obj *rdb, fz_obj *obj);
 
 pdf_font_desc *pdf_new_font_desc(fz_context *ctx);
-pdf_font_desc *pdf_keep_font(pdf_font_desc *fontdesc);
+pdf_font_desc *pdf_keep_font(fz_context *ctx, pdf_font_desc *fontdesc);
 void pdf_drop_font(fz_context *ctx, pdf_font_desc *font);
 
 void pdf_debug_font(pdf_font_desc *fontdesc);
diff --git a/pdf/pdf_cmap.c b/pdf/pdf_cmap.c
index bb1c1ea0..4430979c 100644
--- a/pdf/pdf_cmap.c
+++ b/pdf/pdf_cmap.c
@@ -68,9 +68,9 @@ pdf_new_cmap(fz_context *ctx)
 
 /* Could be a macro for speed */
 pdf_cmap *
-pdf_keep_cmap(pdf_cmap *cmap)
+pdf_keep_cmap(fz_context *ctx, pdf_cmap *cmap)
 {
-	return (pdf_cmap *)fz_keep_storable(&cmap->storable);
+	return (pdf_cmap *)fz_keep_storable(ctx, &cmap->storable);
 }
 
 /* Could be a macro for speed */
@@ -87,7 +87,7 @@ pdf_set_usecmap(fz_context *ctx, pdf_cmap *cmap, pdf_cmap *usecmap)
 
 	if (cmap->usecmap)
 		pdf_drop_cmap(ctx, cmap->usecmap);
-	cmap->usecmap = pdf_keep_cmap(usecmap);
+	cmap->usecmap = pdf_keep_cmap(ctx, usecmap);
 
 	if (cmap->codespace_len == 0)
 	{
diff --git a/pdf/pdf_colorspace.c b/pdf/pdf_colorspace.c
index b2f42b8f..b7f9f131 100644
--- a/pdf/pdf_colorspace.c
+++ b/pdf/pdf_colorspace.c
@@ -211,7 +211,7 @@ pdf_expand_indexed_pixmap(fz_context *ctx, fz_pixmap *src)
 	}
 
 	if (src->mask)
-		dst->mask = fz_keep_pixmap(src->mask);
+		dst->mask = fz_keep_pixmap(ctx, src->mask);
 	dst->interpolate = src->interpolate;
 
 	return dst;
diff --git a/pdf/pdf_font.c b/pdf/pdf_font.c
index d0a7241d..b6c59153 100644
--- a/pdf/pdf_font.c
+++ b/pdf/pdf_font.c
@@ -304,9 +304,9 @@ pdf_load_embedded_font(pdf_font_desc *fontdesc, pdf_xref *xref, fz_obj *stmref)
  */
 
 pdf_font_desc *
-pdf_keep_font(pdf_font_desc *fontdesc)
+pdf_keep_font(fz_context *ctx, pdf_font_desc *fontdesc)
 {
-	return (pdf_font_desc *)fz_keep_storable(&fontdesc->storable);
+	return (pdf_font_desc *)fz_keep_storable(ctx, &fontdesc->storable);
 }
 
 void
diff --git a/pdf/pdf_function.c b/pdf/pdf_function.c
index 5cc4524e..61682ac2 100644
--- a/pdf/pdf_function.c
+++ b/pdf/pdf_function.c
@@ -1295,9 +1295,9 @@ eval_stitching_func(fz_context *ctx, pdf_function *func, float in, float *out)
  */
 
 pdf_function *
-pdf_keep_function(pdf_function *func)
+pdf_keep_function(fz_context *ctx, pdf_function *func)
 {
-	return (pdf_function *)fz_keep_storable(&func->storable);
+	return (pdf_function *)fz_keep_storable(ctx, &func->storable);
 }
 
 void
diff --git a/pdf/pdf_interpret.c b/pdf/pdf_interpret.c
index 7bb2da9c..d42684c0 100644
--- a/pdf/pdf_interpret.c
+++ b/pdf/pdf_interpret.c
@@ -867,14 +867,14 @@ pdf_init_gstate(pdf_gstate *gs, fz_matrix ctm)
 	memset(gs->stroke_state.dash_list, 0, sizeof(gs->stroke_state.dash_list));
 
 	gs->stroke.kind = PDF_MAT_COLOR;
-	gs->stroke.colorspace = fz_keep_colorspace(fz_device_gray);
+	gs->stroke.colorspace = fz_device_gray; /* No fz_keep_colorspace as static */
 	gs->stroke.v[0] = 0;
 	gs->stroke.pattern = NULL;
 	gs->stroke.shade = NULL;
 	gs->stroke.alpha = 1;
 
 	gs->fill.kind = PDF_MAT_COLOR;
-	gs->fill.colorspace = fz_keep_colorspace(fz_device_gray);
+	gs->fill.colorspace = fz_device_gray; /* No fz_keep_colorspace as static */
 	gs->fill.v[0] = 0;
 	gs->fill.pattern = NULL;
 	gs->fill.shade = NULL;
@@ -896,14 +896,14 @@ pdf_init_gstate(pdf_gstate *gs, fz_matrix ctm)
 }
 
 static pdf_material *
-pdf_keep_material(pdf_material *mat)
+pdf_keep_material(fz_context *ctx, pdf_material *mat)
 {
 	if (mat->colorspace)
-		fz_keep_colorspace(mat->colorspace);
+		fz_keep_colorspace(ctx, mat->colorspace);
 	if (mat->pattern)
-		pdf_keep_pattern(mat->pattern);
+		pdf_keep_pattern(ctx, mat->pattern);
 	if (mat->shade)
-		fz_keep_shade(mat->shade);
+		fz_keep_shade(ctx, mat->shade);
 	return mat;
 }
 
@@ -920,19 +920,19 @@ pdf_drop_material(fz_context *ctx, pdf_material *mat)
 }
 
 static void
-copy_state(pdf_gstate *gs, pdf_gstate *old)
+copy_state(fz_context *ctx, pdf_gstate *gs, pdf_gstate *old)
 {
 	gs->stroke = old->stroke;
 	gs->fill = old->fill;
 	gs->font = old->font;
 	gs->softmask = old->softmask;
 
-	pdf_keep_material(&gs->stroke);
-	pdf_keep_material(&gs->fill);
+	pdf_keep_material(ctx, &gs->stroke);
+	pdf_keep_material(ctx, &gs->fill);
 	if (gs->font)
-		pdf_keep_font(gs->font);
+		pdf_keep_font(ctx, gs->font);
 	if (gs->softmask)
-		pdf_keep_xobject(gs->softmask);
+		pdf_keep_xobject(ctx, gs->softmask);
 }
 
 
@@ -975,7 +975,7 @@ pdf_new_csi(pdf_xref *xref, fz_device *dev, fz_matrix ctm, char *event, fz_cooki
 		csi->top_ctm = ctm;
 		pdf_init_gstate(&csi->gstate[0], ctm);
 		if (gstate)
-			copy_state(&csi->gstate[0], gstate);
+			copy_state(ctx, &csi->gstate[0], gstate);
 		csi->gtop = 0;
 
 		csi->cookie = cookie;
@@ -1023,12 +1023,12 @@ pdf_gsave(pdf_csi *csi)
 
 	csi->gtop++;
 	gs = &csi->gstate[csi->gtop];
-	pdf_keep_material(&gs->stroke);
-	pdf_keep_material(&gs->fill);
+	pdf_keep_material(ctx, &gs->stroke);
+	pdf_keep_material(ctx, &gs->fill);
 	if (gs->font)
-		pdf_keep_font(gs->font);
+		pdf_keep_font(ctx, gs->font);
 	if (gs->softmask)
-		pdf_keep_xobject(gs->softmask);
+		pdf_keep_xobject(ctx, gs->softmask);
 }
 
 static void
@@ -1114,7 +1114,7 @@ pdf_set_colorspace(pdf_csi *csi, int what, fz_colorspace *colorspace)
 	fz_drop_colorspace(ctx, mat->colorspace);
 
 	mat->kind = PDF_MAT_COLOR;
-	mat->colorspace = fz_keep_colorspace(colorspace);
+	mat->colorspace = fz_keep_colorspace(ctx, colorspace);
 
 	mat->v[0] = 0;
 	mat->v[1] = 0;
@@ -1167,7 +1167,7 @@ pdf_set_shade(pdf_csi *csi, int what, fz_shade *shade)
 		fz_drop_shade(ctx, mat->shade);
 
 	mat->kind = PDF_MAT_SHADE;
-	mat->shade = fz_keep_shade(shade);
+	mat->shade = fz_keep_shade(ctx, shade);
 }
 
 static void
@@ -1186,7 +1186,7 @@ pdf_set_pattern(pdf_csi *csi, int what, pdf_pattern *pat, float *v)
 
 	mat->kind = PDF_MAT_PATTERN;
 	if (pat)
-		mat->pattern = pdf_keep_pattern(pat);
+		mat->pattern = pdf_keep_pattern(ctx, pat);
 	else
 		mat->pattern = NULL;
 
@@ -1234,13 +1234,13 @@ pdf_show_pattern(pdf_csi *csi, pdf_pattern *pat, fz_rect area, int what)
 		if (what == PDF_FILL)
 		{
 			pdf_drop_material(ctx, &gstate->stroke);
-			pdf_keep_material(&gstate->fill);
+			pdf_keep_material(ctx, &gstate->fill);
 			gstate->stroke = gstate->fill;
 		}
 		if (what == PDF_STROKE)
 		{
 			pdf_drop_material(ctx, &gstate->fill);
-			pdf_keep_material(&gstate->stroke);
+			pdf_keep_material(ctx, &gstate->stroke);
 			gstate->fill = gstate->stroke;
 		}
 	}
@@ -1695,11 +1695,11 @@ static void pdf_run_cs_imp(pdf_csi *csi, fz_obj *rdb, int what)
 	else
 	{
 		if (!strcmp(csi->name, "DeviceGray"))
-			colorspace = fz_keep_colorspace(fz_device_gray);
+			colorspace = fz_device_gray; /* No fz_keep_colorspace as static */
 		else if (!strcmp(csi->name, "DeviceRGB"))
-			colorspace = fz_keep_colorspace(fz_device_rgb);
+			colorspace = fz_device_rgb; /* No fz_keep_colorspace as static */
 		else if (!strcmp(csi->name, "DeviceCMYK"))
-			colorspace = fz_keep_colorspace(fz_device_cmyk);
+			colorspace = fz_device_cmyk; /* No fz_keep_colorspace as static */
 		else
 		{
 			dict = fz_dict_gets(rdb, "ColorSpace");
diff --git a/pdf/pdf_pattern.c b/pdf/pdf_pattern.c
index 1fc356c7..2b4d32a2 100644
--- a/pdf/pdf_pattern.c
+++ b/pdf/pdf_pattern.c
@@ -2,9 +2,9 @@
 #include "mupdf.h"
 
 pdf_pattern *
-pdf_keep_pattern(pdf_pattern *pat)
+pdf_keep_pattern(fz_context *ctx, pdf_pattern *pat)
 {
-	return (pdf_pattern *)fz_keep_storable(&pat->storable);
+	return (pdf_pattern *)fz_keep_storable(ctx, &pat->storable);
 }
 
 void
diff --git a/pdf/pdf_xobject.c b/pdf/pdf_xobject.c
index 61daf9a4..e33ac858 100644
--- a/pdf/pdf_xobject.c
+++ b/pdf/pdf_xobject.c
@@ -2,9 +2,9 @@
 #include "mupdf.h"
 
 pdf_xobject *
-pdf_keep_xobject(pdf_xobject *xobj)
+pdf_keep_xobject(fz_context *ctx, pdf_xobject *xobj)
 {
-	return (pdf_xobject *)fz_keep_storable(&xobj->storable);
+	return (pdf_xobject *)fz_keep_storable(ctx, &xobj->storable);
 }
 
 void