webm2pes: fix PesOptionalHeader::SetPtsBits w/big-endian

PesOptionalHeader::Write() currently writes the low order bits first, so
they're packed according to its 'big-endian' comment.

Bug: webm:1806
Change-Id: I1f3e2b0916594fc8e83537854d69507692de693f

1 files changed, 21 insertions, 20 deletions

diff --git a/m2ts/webm2pes.cc b/m2ts/webm2pes.cc
index afa8a6b..a4169c0 100644
--- a/m2ts/webm2pes.cc
+++ b/m2ts/webm2pes.cc
@@ -33,9 +33,6 @@ std::string ToString(const char* str) {
 //
 
 void PesOptionalHeader::SetPtsBits(std::int64_t pts_90khz) {
-  std::uint64_t* pts_bits = &pts.bits;
-  *pts_bits = 0;
-
   // PTS is broken up and stored in 40 bits as shown:
   //
   //  PES PTS Only flag
@@ -48,32 +45,36 @@ void PesOptionalHeader::SetPtsBits(std::int64_t pts_90khz) {
   const std::uint32_t pts2 = (pts_90khz >> 15) & 0x7FFF;
   const std::uint32_t pts3 = pts_90khz & 0x7FFF;
 
-  std::uint8_t buffer[5] = {0};
-  // PTS only flag.
-  buffer[0] |= 1 << 5;
-  // Top 3 bits of PTS and 1 bit marker.
-  buffer[0] |= pts1 << 1;
-  // Marker.
-  buffer[0] |= 1;
+  pts.bits = 0;
 
-  // Next 15 bits of pts and 1 bit marker.
-  // Top 8 bits of second PTS chunk.
-  buffer[1] |= (pts2 >> 7) & 0xff;
   // bottom 7 bits of second PTS chunk.
-  buffer[2] |= (pts2 << 1);
+  pts.bits |= (pts3 << 1) & 0xff;
   // Marker.
-  buffer[2] |= 1;
+  pts.bits |= 1;
 
   // Last 15 bits of pts and 1 bit marker.
   // Top 8 bits of second PTS chunk.
-  buffer[3] |= (pts3 >> 7) & 0xff;
+  pts.bits <<= 8;
+  pts.bits |= (pts3 >> 7) & 0xff;
+
   // bottom 7 bits of second PTS chunk.
-  buffer[4] |= (pts3 << 1) & 0xff;
+  pts.bits <<= 8;
+  pts.bits |= (pts2 << 1);
   // Marker.
-  buffer[4] |= 1;
+  pts.bits |= 1;
 
-  // Write bits into PesHeaderField.
-  std::memcpy(reinterpret_cast<std::uint8_t*>(pts_bits), buffer, 5);
+  // Next 15 bits of pts and 1 bit marker.
+  // Top 8 bits of second PTS chunk.
+  pts.bits <<= 8;
+  pts.bits |= (pts2 >> 7) & 0xff;
+
+  // PTS only flag.
+  pts.bits <<= 8;
+  pts.bits |= 1 << 5;
+  // Top 3 bits of PTS and 1 bit marker.
+  pts.bits |= pts1 << 1;
+  // Marker.
+  pts.bits |= 1;
 }
 
 // Writes fields to |buffer| and returns true. Returns false when write or