simplify loops

Signed-off-by: Rosen Penev <rosenp@gmail.com>

include/exiv2/jp2image.hpp

@@ -82,6 +82,7 @@ class EXIV2API Jp2Image : public Image {
   void encodeJp2Header(const DataBuf& boxBuf, DataBuf& outBuf);
   //@}
 
+  static std::string toAscii(uint32_t n);
 };  // class Jp2Image
 
 // *****************************************************************************

src/bmffimage.cpp

@@ -84,17 +84,16 @@ BmffImage::BmffImage(BasicIo::UniquePtr io, bool /* create */) :
 
 std::string BmffImage::toAscii(uint32_t n) {
   const auto p = reinterpret_cast<const char*>(&n);
-  std::string result;
-  for (int i = 0; i < 4; i++) {
-    char c = p[isBigEndianPlatform() ? i : (3 - i)];
-    result += [c]() {
-      if (32 <= c && c < 127)
-        return c;  // only allow 7-bit printable ascii
-      if (c == 0)
-        return '_';  // show 0 as _
-      return '.';    // others .
-    }();
-  }
+  std::string result(4, '.');
+  std::transform(p, p + 4, result.begin(), [](char c) {
+    if (32 <= c && c < 127)
+      return c;  // only allow 7-bit printable ascii
+    if (c == 0)
+      return '_';  // show 0 as _
+    return '.';    // others .
+  });
+  if (!isBigEndianPlatform())
+    std::reverse(result.begin(), result.end());
   return result;
 }
 

src/jp2image.cpp

@@ -72,26 +72,6 @@ void lf(std::ostream& out, bool& bLF) {
   }
 }
 
-bool isBigEndian() {
-  union {
-    uint32_t i;
-    char c[4];
-  } e = {0x01000000};
-
-  return e.c[0] != 0;
-}
-
-// Obtains the ascii version from the box.type
-std::string toAscii(long n) {
-  const auto p = reinterpret_cast<const char*>(&n);
-  std::string result;
-  bool bBigEndian = isBigEndian();
-  for (int i = 0; i < 4; i++) {
-    result += p[bBigEndian ? i : (3 - i)];
-  }
-  return result;
-}
-
 void boxes_check(size_t b, size_t m) {
   if (b > m) {
 #ifdef EXIV2_DEBUG_MESSAGES
@@ -117,6 +97,15 @@ 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())
+    std::reverse(result.begin(), result.end());
+  return result;
+}
+
 std::string Jp2Image::mimeType() const {
   return "image/jp2";
 }