From a2666a200eaeb3982cd0f28d3f677ed4901cba3d Mon Sep 17 00:00:00 2001
From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Sat, 5 Feb 2022 12:28:06 +1100
Subject: [PATCH] gxl2gv: replace inline stack implementation with generic API

Similar to previous changes to `gc` in 4e2875fd7376338259dcb3ccc8f029d58bdf22dd,
this replaces some duplicated functionality with the generic Graphviz stack
implementation. This removes the previously hard coded nested subgraph limit of
32. The number of supported subgraphs in now solely limited by available memory.

Gitlab: #1793
---
 cmd/tools/gxl2gv.c | 48 +++++++++++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/cmd/tools/gxl2gv.c b/cmd/tools/gxl2gv.c
index 47cb165a6..223b5c844 100644
--- a/cmd/tools/gxl2gv.c
+++ b/cmd/tools/gxl2gv.c
@@ -12,6 +12,7 @@
 #include    "convert.h"
 #include    <cgraph/agxbuf.h>
 #include    <cgraph/exit.h>
+#include    <cgraph/stack.h>
 #include    <common/memory.h>
 #ifdef HAVE_EXPAT
 #include    <expat.h>
@@ -24,7 +25,6 @@
 #define XML_STATUS_ERROR 0
 #endif
 
-#define STACK_DEPTH	32
 #define BUFSIZE		20000
 #define SMALLBUF	1000
 #define NAMEBUF		100
@@ -115,8 +115,7 @@ static Agraph_t *G;		/* Current graph */
 static Agnode_t *N;		/* Set if Current_class == TAG_NODE */
 static Agedge_t *E;		/* Set if Current_class == TAG_EDGE */
 
-static int GSP;
-static Agraph_t *Gstack[STACK_DEPTH];
+static gv_stack_t Gstack;
 
 typedef struct {
     Dtlink_t link;
@@ -212,26 +211,34 @@ static int isAnonGraph(const char *name)
 
 static void push_subg(Agraph_t * g)
 {
-    if (GSP == STACK_DEPTH) {
-	fprintf(stderr, "gxl2gv: Too many (> %d) nestings of subgraphs\n",
-		STACK_DEPTH);
-	graphviz_exit(1);
-    } else if (GSP == 0)
-	root = g;
-    G = Gstack[GSP++] = g;
+  // insert the new graph
+  stack_push_or_exit(&Gstack, g);
+
+  // save the root if this is the first graph
+  if (stack_size(&Gstack) == 1) {
+    root = g;
+  }
+
+  // update the top graph
+  G = g;
 }
 
 static Agraph_t *pop_subg(void)
 {
-    Agraph_t *g;
-    if (GSP == 0) {
-	fprintf(stderr, "gxl2gv: Gstack underflow in graph parser\n");
-	graphviz_exit(1);
-    }
-    g = Gstack[--GSP];
-    if (GSP > 0)
-	G = Gstack[GSP - 1];
-    return g;
+  // is the stack empty?
+  if (stack_is_empty(&Gstack)) {
+    fprintf(stderr, "gxl2gv: Gstack underflow in graph parser\n");
+    graphviz_exit(EXIT_FAILURE);
+  }
+
+  // pop the top graph
+  Agraph_t *g = stack_pop(&Gstack);
+
+  // update the top graph
+  if (!stack_is_empty(&Gstack))
+    G = stack_top(&Gstack);
+
+  return g;
 }
 
 static Agnode_t *bind_node(const char *name)
@@ -444,7 +451,7 @@ startElementHandler(void *userData, const char *name, const char **atts)
 	    edgeMode = atts[pos];
 	}
 
-	if (GSP == 0) {
+	if (stack_is_empty(&Gstack)) {
 	    if (strcmp(edgeMode, "directed") == 0) {
 		g = agopen((char *) id, Agdirected, &AgDefaultDisc);
 	    } else if (strcmp(edgeMode, "undirected") == 0) {
@@ -727,6 +734,7 @@ Agraph_t *gxl_to_gv(FILE * gxlFile)
     } while (!done);
     XML_ParserFree(parser);
     freeUserdata(udata);
+    stack_reset(&Gstack);
 
     return root;
 }
-- 
2.40.0