toAscii: replace logic with masking loop

Avoids having to deal with endianness.

Signed-off-by: Rosen Penev <[email protected]>

Author: neheb

src/bmffimage.cpp

@@ -87,15 +87,16 @@ BmffImage::BmffImage(BasicIo::UniquePtr io, bool /* create */, size_t max_box_de
 }  // BmffImage::BmffImage
 
 std::string BmffImage::toAscii(uint32_t n) {
-  const auto p = reinterpret_cast<const char*>(&n);
-  std::string result(p, p + 4);
-  if (!isBigEndianPlatform())
-    std::reverse(result.begin(), result.end());
-  // show 0 as _
-  std::replace(result.begin(), result.end(), '\0', '_');
-  // show non 7-bit printable ascii as .
-  auto f = [](unsigned char c) { return c < 32 || c > 126; };
-  std::replace_if(result.begin(), result.end(), f, '.');
+  std::string result(sizeof(uint32_t), '\0');
+  for (size_t i = 0; i < result.size(); ++i) {
+    auto c = static_cast<unsigned char>(n >> (8 * (3 - i)));
+    if (c == 0)
+      result[i] = '_';
+    else if (c < 32 || c > 126)
+      result[i] = '.';
+    else
+      result[i] = static_cast<char>(c);
+  }
   return result;
 }
 

src/jp2image.cpp

@@ -112,11 +112,11 @@ Jp2Image::Jp2Image(BasicIo::UniquePtr io, bool create) : Image(ImageType::jp2, m
 
 // Obtains the ascii version from the box.type
 std::string Jp2Image::toAscii(uint32_t n) {
-  const auto p = reinterpret_cast<const char*>(&n);
-  std::string result(p, p + 4);
-  if (isBigEndianPlatform())
-    return result;
-  std::reverse(result.begin(), result.end());
+  std::string result(sizeof(uint32_t), '\0');
+  for (size_t i = 0; i < result.size(); ++i) {
+    auto c = static_cast<unsigned char>(n >> (8 * (3 - i)));
+    result[i] = static_cast<char>(c);
+  }
   return result;
 }