Fix importing of binary STLs in big-endian architectures (#4143)

Fix from https://github.com/admesh/admesh/pull/26

xs/src/admesh/portable_endian.h

@@ -0,0 +1,123 @@
+/* portable_endian.h
+ * from https://gist.github.com/panzi/6856583
+ * "License": Public Domain
+ * I, Mathias Panzenböck, place this file hereby into the public domain. Use it
+ * at your own risk for whatever you like.  In case there are jurisdictions
+ * that don't support putting things in the public domain you can also consider
+ * it to be "dual licensed" under the BSD, MIT and Apache licenses, if you want
+ * to. This code is trivial anyway. Consider it an example on how to get the
+ * endian conversion functions on different platforms.
+ */
+
+#ifndef PORTABLE_ENDIAN_H__
+#define PORTABLE_ENDIAN_H__
+
+#if (defined(_WIN16) || defined(_WIN32) || defined(_WIN64)) && !defined(__WINDOWS__)
+
+#	define __WINDOWS__
+
+#endif
+
+#if defined(__linux__) || defined(__CYGWIN__)
+
+#	include <endian.h>
+
+#elif defined(__APPLE__)
+
+#	include <libkern/OSByteOrder.h>
+
+#	define htobe16(x) OSSwapHostToBigInt16(x)
+#	define htole16(x) OSSwapHostToLittleInt16(x)
+#	define be16toh(x) OSSwapBigToHostInt16(x)
+#	define le16toh(x) OSSwapLittleToHostInt16(x)
+ 
+#	define htobe32(x) OSSwapHostToBigInt32(x)
+#	define htole32(x) OSSwapHostToLittleInt32(x)
+#	define be32toh(x) OSSwapBigToHostInt32(x)
+#	define le32toh(x) OSSwapLittleToHostInt32(x)
+ 
+#	define htobe64(x) OSSwapHostToBigInt64(x)
+#	define htole64(x) OSSwapHostToLittleInt64(x)
+#	define be64toh(x) OSSwapBigToHostInt64(x)
+#	define le64toh(x) OSSwapLittleToHostInt64(x)
+
+#	define __BYTE_ORDER    BYTE_ORDER
+#	define __BIG_ENDIAN    BIG_ENDIAN
+#	define __LITTLE_ENDIAN LITTLE_ENDIAN
+#	define __PDP_ENDIAN    PDP_ENDIAN
+
+#elif defined(__OpenBSD__)
+
+#	include <sys/endian.h>
+
+#elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
+
+#	include <sys/endian.h>
+
+#	define be16toh(x) betoh16(x)
+#	define le16toh(x) letoh16(x)
+
+#	define be32toh(x) betoh32(x)
+#	define le32toh(x) letoh32(x)
+
+#	define be64toh(x) betoh64(x)
+#	define le64toh(x) letoh64(x)
+
+#elif defined(__WINDOWS__)
+
+/* #	include <winsock2.h> */
+#	include <sys/param.h>
+
+#	if BYTE_ORDER == LITTLE_ENDIAN
+
+#		define htobe16(x) htons(x)
+#		define htole16(x) (x)
+#		define be16toh(x) ntohs(x)
+#		define le16toh(x) (x)
+ 
+#		define htobe32(x) htonl(x)
+#		define htole32(x) (x)
+#		define be32toh(x) ntohl(x)
+#		define le32toh(x) (x)
+ 
+#		define htobe64(x) htonll(x)
+#		define htole64(x) (x)
+#		define be64toh(x) ntohll(x)
+#		define le64toh(x) (x)
+
+#	elif BYTE_ORDER == BIG_ENDIAN
+
+		/* that would be xbox 360 */
+#		define htobe16(x) (x)
+#		define htole16(x) __builtin_bswap16(x)
+#		define be16toh(x) (x)
+#		define le16toh(x) __builtin_bswap16(x)
+ 
+#		define htobe32(x) (x)
+#		define htole32(x) __builtin_bswap32(x)
+#		define be32toh(x) (x)
+#		define le32toh(x) __builtin_bswap32(x)
+ 
+#		define htobe64(x) (x)
+#		define htole64(x) __builtin_bswap64(x)
+#		define be64toh(x) (x)
+#		define le64toh(x) __builtin_bswap64(x)
+
+#	else
+
+#		error byte order not supported
+
+#	endif
+
+#	define __BYTE_ORDER    BYTE_ORDER
+#	define __BIG_ENDIAN    BIG_ENDIAN
+#	define __LITTLE_ENDIAN LITTLE_ENDIAN
+#	define __PDP_ENDIAN    PDP_ENDIAN
+
+#else
+
+#	error platform not supported
+
+#endif
+
+#endif

xs/src/admesh/stlinit.c

@@ -21,11 +21,13 @@
  */
 
 #include <float.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <math.h>
 
+#include "portable_endian.h"
 #include "stl.h"
 
 #ifndef SEEK_SET
@@ -68,7 +70,7 @@ stl_initialize(stl_file *stl) {
 void
 stl_count_facets(stl_file *stl, const ADMESH_CHAR *file) {
   long           file_size;
-  int            header_num_facets;
+  uint32_t       header_num_facets;
   int            num_facets;
   int            i;
   size_t         s;
@@ -123,7 +125,7 @@ stl_count_facets(stl_file *stl, const ADMESH_CHAR *file) {
     }
 
     /* Read the int following the header.  This should contain # of facets */
-    if((!fread(&header_num_facets, sizeof(int), 1, stl->fp)) || (num_facets != header_num_facets)) {
+    if((!fread(&header_num_facets, sizeof(uint32_t), 1, stl->fp)) || (uint32_t)num_facets != le32toh(header_num_facets)) {
       fprintf(stderr,
               "Warning: File size doesn't match number of facets in the header\n");
 
@@ -260,7 +262,24 @@ stl_reallocate(stl_file *stl) {
 void
 stl_read(stl_file *stl, int first_facet, int first) {
   stl_facet facet;
-  int   i;
+  int   i, j;
+  const int facet_float_length = 12;
+  float *facet_floats[12];
+  char facet_buffer[12 * sizeof(float)];
+  uint32_t endianswap_buffer;  /* for byteswapping operations */
+
+  facet_floats[0] = &facet.normal.x;
+  facet_floats[1] = &facet.normal.y;
+  facet_floats[2] = &facet.normal.z;
+  facet_floats[3] = &facet.vertex[0].x;
+  facet_floats[4] = &facet.vertex[0].y;
+  facet_floats[5] = &facet.vertex[0].z;
+  facet_floats[6] = &facet.vertex[1].x;
+  facet_floats[7] = &facet.vertex[1].y;
+  facet_floats[8] = &facet.vertex[1].z;
+  facet_floats[9] = &facet.vertex[2].x;
+  facet_floats[10] = &facet.vertex[2].y;
+  facet_floats[11] = &facet.vertex[2].z;
 
   if (stl->error) return;
 
@@ -274,11 +293,19 @@ stl_read(stl_file *stl, int first_facet, int first) {
     if(stl->stats.type == binary)
       /* Read a single facet from a binary .STL file */
     {
-      /* we assume little-endian architecture! */
-      if (fread(&facet, 1, SIZEOF_STL_FACET, stl->fp) != SIZEOF_STL_FACET) {
+      if(fread(facet_buffer, sizeof(facet_buffer), 1, stl->fp)
+         + fread(&facet.extra, sizeof(char), 2, stl->fp) != 3) {
+        perror("Cannot read facet");
         stl->error = 1;
         return;
       }
+
+      for(j = 0; j < facet_float_length; j++) {
+        /* convert LE float to host byte order */
+        memcpy(&endianswap_buffer, facet_buffer + j * sizeof(float), 4);
+        endianswap_buffer = le32toh(endianswap_buffer);
+        memcpy(facet_floats[j], &endianswap_buffer, 4);
+      }
     } else
       /* Read a single facet from an ASCII .STL file */
     {