[Gnash-commit] [SCM] Gnash branch, master, updated. release_0_8_9_final-468-gbfc794c

[Sandro Santilli]

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- Log -----------------------------------------------------------------
http://git.savannah.gnu.org/cgit//commit/?id=bfc794c3074ad787031015d456209f5c3b3c1818


commit bfc794c3074ad787031015d456209f5c3b3c1818
Author: Jonas 'Sortie' Termansen <address@hidden>
Date:   Sat Jul 9 19:05:25 2011 +0200

    Don't memcpy data if you need to endian-swap it anyways.
    
    Formerly, the code memcpy'd the data to a new buffer,
    and then endian-swapped it, thus doing twice the work.
    Now it should do the endian-swapping during the copy phase.
    The compiler will usually optimize the byte swap into a single
    rot8 instruction - I assume BE CPUs have the same instruction.

diff --git a/libmedia/AudioDecoderSimple.cpp b/libmedia/AudioDecoderSimple.cpp
index 80a2e0f..0415c4c 100644
--- a/libmedia/AudioDecoderSimple.cpp
+++ b/libmedia/AudioDecoderSimple.cpp
@@ -370,7 +370,7 @@ AudioDecoderSimple::decode(const boost::uint8_t* input, 
boost::uint32_t inputSiz
 {
 
        unsigned char* decodedData = NULL;
-       int outsize = 0;
+       boost::uint32_t outsize = 0;
 
     switch (_codec) {
        case AUDIO_CODEC_ADPCM:
@@ -405,10 +405,11 @@ AudioDecoderSimple::decode(const boost::uint8_t* input, 
boost::uint32_t inputSiz
                        outsize = inputSize * (_stereo ? 4 : 2);
 
                } else {
+                       // Allocate a destination buffer
                        // Read 16-bit data into buffer
                        decodedData = new unsigned char[inputSize];
-                       memcpy((char *)decodedData, input, inputSize);
-
+                       outsize = inputSize;
+                       
                        // Convert 16-bit little-endian data to host-endian.
 
                        // Runtime detection of host endianness costs almost
@@ -423,19 +424,30 @@ AudioDecoderSimple::decode(const boost::uint8_t* input, 
boost::uint32_t inputSiz
                        } u = { 0x0001 };
 
                        switch (u.c.c0) {
+                               default:        // Impossible
+                                       log_error(_("Host endianness not 
detected in AudioDecoderSimple"));
+                                       // Just carry on anyway...
                                case 0x01:      // Little-endian host: sample 
is already native.
+                                       // If the input data is the output 
data, then we probably
+                                       // can't move the data faster than 
memcpy.
+                                       memcpy((char *)decodedData, input, 
inputSize);
                                        break;
                                case 0x00:  // Big-endian host
                                        // Swap sample bytes to get big-endian 
format.
                                        assert((inputSize & 1) == 0);
-                                       for (unsigned i = 0; i < inputSize; 
i+=2)
+
+                                       // Cast the buffers to help the 
compiler understand that we
+                                       // swapping 16-bit words. This should 
produce a single-instruction
+                                       // swap for each 16-bit word.
+                                       const boost::uint16_t* input16 = 
reinterpret_cast<const boost::uint16_t*>(input);
+                                       boost::uint16_t* decodedData16 = 
reinterpret_cast<boost::uint16_t*>(decodedData);
+                                       unsigned inputSize16 = inputSize / 
sizeof(boost::uint16_t);
+                                       for ( unsigned i = 0; i < inputSize16; 
i++ )
                                        {
-                                               std::swap(decodedData[i], 
decodedData[i+1]);
+                                               boost::uint16_t sample = 
input16[i];
+                                               decodedData16[i] = ((sample << 
8) & 0xFF00) | ((sample >> 8) & 0x00FF);
                                        }
                                        break;
-                       default:        // Impossible
-                                       log_error(_("Host endianness not 
detected in AudioDecoderSimple"));
-                                       // Just carry on anyway...
                        }
                }
                break;

-----------------------------------------------------------------------

Summary of changes:
 libmedia/AudioDecoderSimple.cpp |   28 ++++++++++++++++++++--------
 1 files changed, 20 insertions(+), 8 deletions(-)


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