From df56a03abfcb26dee23fffce536326168af6afb8 Mon Sep 17 00:00:00 2001
From: Dirk Farin <dirk.farin@gmail.com>
Date: Tue, 15 Oct 2024 21:20:48 +0200
Subject: [PATCH] simplify reading/writing floats

---
 libheif/bitstream.cc | 65 ++++----------------------------------------
 libheif/bitstream.h  | 10 ++-----
 2 files changed, 8 insertions(+), 67 deletions(-)

diff --git a/libheif/bitstream.cc b/libheif/bitstream.cc
index 1b73bb0eec..cddc34d2c3 100644
--- a/libheif/bitstream.cc
+++ b/libheif/bitstream.cc
@@ -270,12 +270,10 @@ uint32_t BitstreamRange::read32()
                      (buf[3]));
 }
 
-float BitstreamRange::readFloat32()
+float BitstreamRange::read_float32()
 {
-    int i = read32();
-    float f;
-    memcpy(&f, &i, sizeof(float));
-    return f;
+    uint32_t i = read32();
+    return std::bit_cast<float>(i); // this works directly on the value layout, thus we do not have to worry about memory layout
 }
 
 
@@ -351,33 +349,6 @@ int64_t BitstreamRange::read64s()
 }
 
 
-float BitstreamRange::read_float32()
-{
-  assert(sizeof(float)==4);
-
-  if (!prepare_read(4)) {
-    return 0;
-  }
-
-  uint8_t buf[4];
-
-  auto istr = get_istream();
-  bool success = istr->read((char*) buf, 4);
-
-  if (!success) {
-    set_eof_while_reading();
-    return 0;
-  }
-
-#if !IS_BIG_ENDIAN
-  std::swap(buf[0],buf[3]);
-  std::swap(buf[1],buf[2]);
-#endif
-
-  return *reinterpret_cast<float*>(buf);
-}
-
-
 std::string BitstreamRange::read_string()
 {
   std::string str;
@@ -723,11 +694,9 @@ void StreamWriter::write32(uint32_t v)
 }
 
 
-void StreamWriter::writeFloat32(float v)
+void StreamWriter::write_float32(float v)
 {
-  uint32_t i;
-  memcpy(&i, &v, sizeof(float));
-  write32(i);
+  write32(std::bit_cast<uint32_t>(v)); // this works directly on the value layout, thus we do not have to worry about memory layout
 }
 
 
@@ -770,30 +739,6 @@ void StreamWriter::write64(int64_t v)
 }
 
 
-void StreamWriter::write_float32(float v)
-{
-  assert(sizeof(float)==4);
-
-  uint8_t buf[4];
-  *reinterpret_cast<float*>(buf) = v;
-
-#if !IS_BIG_ENDIAN
-  std::swap(buf[0], buf[3]);
-  std::swap(buf[1], buf[2]);
-#endif
-
-  if (m_position + 4 > m_data.size()) {
-    m_data.resize(m_position + 4);
-  }
-
-  m_data[m_position++] = buf[0];
-  m_data[m_position++] = buf[1];
-  m_data[m_position++] = buf[2];
-  m_data[m_position++] = buf[3];
-}
-
-
-
 void StreamWriter::write(int size, uint64_t value)
 {
   if (size == 1) {
diff --git a/libheif/bitstream.h b/libheif/bitstream.h
index 5941956fb2..0f8e5a9422 100644
--- a/libheif/bitstream.h
+++ b/libheif/bitstream.h
@@ -270,14 +270,12 @@ class BitstreamRange
   /**
    * Read 32 bit floating point value from the bitstream.
    *
-   * The data is assumed to be in big endian format.
+   * The file data is assumed to be in big endian format.
    */
-  float readFloat32();
+  float read_float32();
 
   int64_t read64s();
 
-  float read_float32();
-
   std::string read_string();
 
   bool read(uint8_t* data, size_t n);
@@ -442,7 +440,7 @@ class StreamWriter
 
   void write64(uint64_t);
 
-  void writeFloat32(float);
+  void write_float32(float);
 
   void write64(int64_t);
 
@@ -454,8 +452,6 @@ class StreamWriter
 
   void write(const StreamWriter&);
 
-  void write_float32(float);
-
   void skip(int n);
 
   void insert(int nBytes);