From a296ac40d4cef68e4979b655f87cbc7c022be5c0 Mon Sep 17 00:00:00 2001
From: Valtteri Koskivuori <vkoskiv@gmail.com>
Date: Sat, 11 Nov 2023 19:51:01 +0200
Subject: [PATCH] Remove support for negative offsets in wavefront parser

I checked, and none of the meshes I've used for testing seem to
actually this.
Negative offsets would index off the end of vertex buffers, but
supporting this requires that we iterate over the wavefront file at
least twice - Once to count the totals, and a second pass to do the
actual parsing.
Seems like a very small gain for all that additional parsing required,
and I'm hoping to delete this parser entirely in the near future anyway,
so I don't really mind if it's not fully compliant.
---
 .../loaders/formats/wavefront/wavefront.c     | 54 ++++++-------------
 1 file changed, 15 insertions(+), 39 deletions(-)

diff --git a/src/utils/loaders/formats/wavefront/wavefront.c b/src/utils/loaders/formats/wavefront/wavefront.c
index 3b70ed37..0681d12f 100644
--- a/src/utils/loaders/formats/wavefront/wavefront.c
+++ b/src/utils/loaders/formats/wavefront/wavefront.c
@@ -6,6 +6,7 @@
 //  Copyright © 2019-2023 Valtteri Koskivuori. All rights reserved.
 //
 
+#include <stdint.h>
 #include <string.h>
 #include "../../../../includes.h"
 #include "../../../../datatypes/mesh.h"
@@ -68,21 +69,21 @@ static inline size_t parse_polys(lineBuffer *line, struct poly *buf) {
 	return polycount;
 }
 
-static int fixIndex(size_t max, int oldIndex) {
-	if (oldIndex == 0) // Unused
-		return -1;
-	
-	if (oldIndex < 0) // Relative to end of list
-		return (int)max + oldIndex;
-	
-	return oldIndex - 1;// Normal indexing
+static inline int fixIndex(int idx) {
+	if (idx == 0) return -1; // Unused
+	// Wavefront is supposed to support negative indexing, which
+	// would mean we would index off the end of the vertex list.
+	// But supporting that makes parsing super inefficient, and
+	// I've never seen a file that actually does that, so we don't
+	// support it anymore.
+	return idx - 1;// Normal indexing
 }
 
-static void fixIndices(struct poly *p, size_t totalVertices, size_t totalTexCoords, size_t totalNormals) {
+static inline void fixIndices(struct poly *p) {
 	for (int i = 0; i < MAX_CRAY_VERTEX_COUNT; ++i) {
-		p->vertexIndex[i] = fixIndex(totalVertices, p->vertexIndex[i]);
-		p->textureIndex[i] = fixIndex(totalTexCoords, p->textureIndex[i]);
-		p->normalIndex[i] = fixIndex(totalNormals, p->normalIndex[i]);
+		p->vertexIndex[i] = fixIndex(p->vertexIndex[i]);
+		p->textureIndex[i] = fixIndex(p->textureIndex[i]);
+		p->normalIndex[i] = fixIndex(p->normalIndex[i]);
 	}
 }
 
@@ -107,29 +108,6 @@ struct mesh_arr parse_wavefront(const char *file_path, struct file_cache *cache)
 	char *assetPath = get_file_path(file_path);
 	
 	char buf[LINEBUFFER_MAXSIZE];
-	// Count totals and preallocate space
-	size_t total_vertices  = 0;
-	size_t total_texcoords = 0;
-	size_t total_normals   = 0;
-	size_t total_polys     = 0;
-	char *head = firstLine(file);
-	lineBuffer line0 = { .buf = buf };
-	while (head) {
-		if (head[0] == 'v') {
-			total_vertices++;
-		} else if (head[0] == 'f') {
-			fillLineBuffer(&line0, head, ' ');
-			if (line0.amountOf.tokens > 4)
-				total_polys += 2;
-			else
-				total_polys++;
-		} else if (head[0] == 'v' && head[1] == 'n') {
-			total_normals++;
-		} else if (head[0] == 'v' && head[1] == 't') {
-			total_texcoords++;
-		}
-		head = nextLine(file);
-	};
 
 	int current_material_idx = 0;
 	
@@ -142,7 +120,7 @@ struct mesh_arr parse_wavefront(const char *file_path, struct file_cache *cache)
 	struct poly polybuf[2];
 
 	//Start processing line-by-line, state machine style.
-	head = firstLine(file);
+	char *head = firstLine(file);
 	lineBuffer line = { .buf = buf };
 	while (head) {
 		fillLineBuffer(&line, head, ' ');
@@ -169,9 +147,7 @@ struct mesh_arr parse_wavefront(const char *file_path, struct file_cache *cache)
 			size_t count = parse_polys(&line, polybuf);
 			for (size_t i = 0; i < count; ++i) {
 				struct poly p = polybuf[i];
-				//TODO: Check if we actually need the file totals here
-				// fixIndices(&p, current->vbuf->vertices.count, current->vbuf->texture_coords.count, current->vbuf->normals.count);
-				fixIndices(&p, total_vertices, total_texcoords, total_normals);
+				fixIndices(&p);
 				//FIXME
 				// current->surface_area += get_poly_area(&p, current->vertices.items);
 				p.materialIndex = current_material_idx;