From 148a9999536a7faa7403d7a79f8822f3085c19b7 Mon Sep 17 00:00:00 2001
From: William Miles <wmpmiles@gmail.com>
Date: Mon, 5 Sep 2022 20:04:54 +1000
Subject: [PATCH] Implemented walker overlay that calculates decompressed size.

---
 NavmeshList/main.c    |  3 ++-
 espReader/ESPReader.h |  5 +++++
 espReader/Reader.c    | 28 ++++++++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/NavmeshList/main.c b/NavmeshList/main.c
index 3a955c7..d754482 100644
--- a/NavmeshList/main.c
+++ b/NavmeshList/main.c
@@ -23,7 +23,8 @@ int main(void) {
 	size_t read = fread(buffer, sizeof(char), size, fp);
 	assert(read == size);
 
-	espr_print(buffer, size);
+	size_t decompressed = espr_decompressed_size(buffer, size);
+	printf("%llu -> %llu\n", size, decompressed);
 
 	return 0;
 }
diff --git a/espReader/ESPReader.h b/espReader/ESPReader.h
index 2188fa6..df4b336 100644
--- a/espReader/ESPReader.h
+++ b/espReader/ESPReader.h
@@ -267,6 +267,11 @@ extern "C" {
 	 */
 	void espr_print(char *data, size_t size);
 
+	/* Calculates the size of the esp data if all of the compressed records are
+	 * decompressed.
+	 */
+	size_t espr_decompressed_size(char *data, size_t size);
+
 // End C++ guard
 #ifdef __cplusplus
 }
diff --git a/espReader/Reader.c b/espReader/Reader.c
index 4439cbc..182c93f 100644
--- a/espReader/Reader.c
+++ b/espReader/Reader.c
@@ -43,6 +43,7 @@ void print_type4(Type4 val);
 // Utilities
 Timestamp convert_ts(uint16_t ts);
 void print_callback(Node n, void *_);
+void dc_size_cb(Node n, void *dc_size_ptr);
 
 //
 // === FUNCTIONS ===
@@ -88,6 +89,33 @@ void print_callback(Node n, void *pt) {
 	}
 }
 
+size_t espr_decompressed_size(char *data, size_t size) {
+	size_t dc_size = 0;
+	espr_walk(data, size, dc_size_cb, &dc_size);
+	return dc_size;
+}
+
+void dc_size_cb(Node n, void *dc_size_ptr) {
+	size_t *dcsp = dc_size_ptr;
+	switch (n.type) {
+		case NT_GROUP:
+			// Only add header size for groups, internals will be walked
+			*dcsp += sizeof(Group);
+			break;
+		case NT_RECORD:
+			// Add the whole record and header, records are leaf-ish
+			*dcsp += sizeof(Record);
+			if (n.header.record->flags & COMPRESSED_FLAG) {
+				// Read decompressed size
+				*dcsp += *((uint32_t *)n.data);
+			} else
+				*dcsp += n.header.record->size;
+			break;
+		default:
+			assert(false); // invalid node type
+	}
+}
+
 /* Unknown data will be some concatenation of groups and records.
  *
  * `walk_concat` will call the appropriate walking function