From 292e1ce9dbfc287fb2f114882878c7342078b886 Mon Sep 17 00:00:00 2001
From: Thomas Bernard <miniupnp@free.fr>
Date: Sat, 30 Jan 2021 11:43:53 +0100
Subject: [PATCH] Custom implementation of Realpath()

---
 src/io.h           |  1 +
 src/realpath.c     | 59 +++++++++++++++++++++++++++++++++++++++++++++-
 src/tests/testio.c | 22 +++++++++++++++++
 3 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/src/io.h b/src/io.h
index 8f6eb26e..08f38b94 100644
--- a/src/io.h
+++ b/src/io.h
@@ -37,6 +37,7 @@
 #define IO_H__
 
 #include <stdio.h>
+#include "struct.h"
 
 
 /** @defgroup io File input/output
diff --git a/src/realpath.c b/src/realpath.c
index 6861e4e5..340aadcf 100644
--- a/src/realpath.c
+++ b/src/realpath.c
@@ -16,10 +16,67 @@
 #endif
 
 #if defined(__AROS__) || defined(__BEOS__) || defined(__MORPHOS__) || defined(__GP2X__) || defined(__WIZ__) || defined(__CAANOO__) || defined(__amigaos__) || defined(__SWITCH__)
+
+#include "io.h"
+#include "gfx2log.h"
+#include "gfx2mem.h"
 // These platforms don't have realpath().
+// Our custom implementation uses chdir() and relies on
+// errno == ENOTDIR when trying to change directory to a file
 char *Realpath(const char *_path)
 {
-  return strdup(_path);
+  char * rpath = NULL;
+  char * current_dir_save;
+
+  // backup current directory
+  current_dir_save = Get_current_directory(NULL, NULL, 0);
+  if (current_dir_save == NULL) {
+    // error
+    return NULL;
+  }
+
+  if (chdir(_path) < 0) {
+    if (errno == ENOTDIR) {
+      const char * position;
+      const char * filename;
+      char * directory;
+      position = Find_last_separator(_path);
+      if (position != NULL) {
+        size_t dirlen = position - _path;
+        filename = position + 1;
+        directory = GFX2_malloc(dirlen);
+        if (directory != NULL) {
+          memcpy(directory, _path, dirlen);
+          directory[dirlen] = '\0';
+          GFX2_Log(GFX2_DEBUG, "Directory : \"%s\", filename : \"%s\"\n", directory, filename);
+          if (chdir(directory) == 0) {
+            char * dirpart = Get_current_directory(NULL, NULL, 0);
+            if (dirpart != NULL) {
+              size_t len = strlen(dirpart) + strlen(filename) + 2;
+              rpath = GFX2_malloc(len);
+              if (rpath != NULL) {
+                snprintf(rpath, len, "%s%s%s", dirpart, PATH_SEPARATOR, filename);
+              }
+              free(dirpart);
+            }
+          } else {
+            GFX2_Log(GFX2_ERROR, "chdir(\"%s\") : %s\n", directory, strerror(errno));
+          }
+          free(directory);
+        }
+      }
+    } else {
+      GFX2_Log(GFX2_ERROR, "chdir(\"%s\") : %s\n", _path, strerror(errno));
+    }
+  } else {
+    // _path is a directory
+    rpath = Get_current_directory(NULL, NULL, 0);
+  }
+
+  // "restore" current directory
+  chdir(current_dir_save);
+  free(current_dir_save);
+  return rpath;
 }
             
 #elif defined(__WIN32__) || defined(WIN32)
diff --git a/src/tests/testio.c b/src/tests/testio.c
index 84d4f0fa..98f46ee2 100644
--- a/src/tests/testio.c
+++ b/src/tests/testio.c
@@ -306,8 +306,11 @@ int Test_File_exists(char * errmsg)
 
 int Test_Realpath(char * errmsg)
 {
+  char filepath[256];
   char * path;
+  FILE * f;
 
+  // Directory test
   path = Realpath(tmpdir);
   if (path == NULL)
   {
@@ -316,6 +319,25 @@ int Test_Realpath(char * errmsg)
   }
   GFX2_Log(GFX2_DEBUG, "Realpath(\"%s\") returned \"%s\"\n", tmpdir, path);
   free(path);
+
+  // File test
+  snprintf(filepath, sizeof(filepath), "%s/tempfile.txt", tmpdir);
+  f = fopen(filepath, "w");
+  if (f == NULL) {
+    snprintf(errmsg, ERRMSG_LENGTH, "Failed to create \"%s\"", filepath);
+    return 0;
+  }
+  fputs("TEST\n", f);
+  fclose(f);
+  path = Realpath(filepath);
+  Remove_path(filepath);
+  if (path == NULL)
+  {
+    snprintf(errmsg, ERRMSG_LENGTH, "Realpath(\"%s\") returned NULL", filepath);
+    return 0;
+  }
+  GFX2_Log(GFX2_DEBUG, "Realpath(\"%s\") returned \"%s\"\n", filepath, path);
+  free(path);
   return 1;
 }