Improved ArrayBuffer write performance

Massively improved ArrayBuffer Graphics fill performance for bpp<8
espruino · Jan 16, 2015 · 59d7766 · 59d7766
1 parent b983a1b
commit 59d7766
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Showing 4 changed files with 62 additions and 14 deletions.
diff --git a/ChangeLog b/ChangeLog
@@ -37,6 +37,8 @@
             Add Boolean constructor (fix #311)
             Fix difference between String() and String(undefined) (fix #312)
             Fix I2C/SPI on F401/F411-based boards (fix #470, fix #473)
+            Improved ArrayBuffer write performance
+            Massively improved ArrayBuffer Graphics fill performance for bpp<8
 
      1v71 : Allowed WIZnet + CC3000 to be instantiated on any pins
             Fix break inside loop inside case inside function (fix 428)

diff --git a/libs/graphics/lcd_arraybuffer.c b/libs/graphics/lcd_arraybuffer.c
@@ -59,13 +59,30 @@ void lcdSetPixels_ArrayBuffer(JsGraphics *gfx, short x, short y, short pixelCoun
     size_t idx = lcdGetPixelIndex_ArrayBuffer(gfx,x,y,pixelCount);
     JsvArrayBufferIterator it;
     jsvArrayBufferIteratorNew(&it, buf, idx>>3 );
-    short p;
-    for (p=0;p<pixelCount;p++) { // writing individual bits
+
+    unsigned int whiteMask = (1U<<gfx->data.bpp)-1;
+    bool shortCut = col==0 || (col&whiteMask)==whiteMask; // simple black or white fill
+
+    while (pixelCount--) { // writing individual bits
       if (gfx->data.bpp&7/*not a multiple of one byte*/) {
         idx = idx & 7;
+        if (shortCut && idx==0) {
+          // Basically, if we're aligned and we're filling all 0 or all 1
+          // then we can go really quickly and can just fill
+          int wholeBytes = (gfx->data.bpp*(pixelCount+1)) >> 3;
+          if (wholeBytes) {
+            char c = (char)(col?0xFF:0);
+            pixelCount = (short)(pixelCount+1 - (wholeBytes*8/gfx->data.bpp));
+            while (wholeBytes--) {
+              jsvArrayBufferIteratorSetByteValue(&it,  c);
+              jsvArrayBufferIteratorNext(&it);
+            }
+            continue;
+          }
+        }
         unsigned int mask = (unsigned int)(1<<gfx->data.bpp)-1;
         unsigned int existing = (unsigned int)jsvArrayBufferIteratorGetIntegerValue(&it);
-        jsvArrayBufferIteratorSetIntegerValue(&it, (JsVarInt)((existing&~(mask<<idx)) | ((col&mask)<<idx)));
+        jsvArrayBufferIteratorSetByteValue(&it, (char)((existing&~(mask<<idx)) | ((col&mask)<<idx)));
         if (gfx->data.flags & JSGRAPHICSFLAGS_ARRAYBUFFER_VERTICAL_BYTE) {
           jsvArrayBufferIteratorNext(&it);
         } else {
@@ -75,7 +92,7 @@ void lcdSetPixels_ArrayBuffer(JsGraphics *gfx, short x, short y, short pixelCoun
       } else { // we're writing whole bytes
         int i;
         for (i=0;i<gfx->data.bpp;i+=8) {
-          jsvArrayBufferIteratorSetIntegerValue(&it, (JsVarInt)(col >> i));
+          jsvArrayBufferIteratorSetByteValue(&it, (char)(col >> i));
           jsvArrayBufferIteratorNext(&it);
         }
       }

diff --git a/src/jsvariterator.c b/src/jsvariterator.c
@@ -254,6 +254,32 @@ JsVarFloat jsvArrayBufferIteratorGetFloatValue(JsvArrayBufferIterator *it) {
   }
 }
 
+void   jsvArrayBufferIteratorSetIntegerValue(JsvArrayBufferIterator *it, JsVarInt v) {
+  if (it->type == ARRAYBUFFERVIEW_UNDEFINED) return;
+  assert(!it->hasAccessedElement); // we just haven't implemented this case yet
+  char data[8];
+  unsigned int i,dataLen = JSV_ARRAYBUFFER_GET_SIZE(it->type);
+
+  if (JSV_ARRAYBUFFER_IS_FLOAT(it->type)) {
+    if (dataLen==4) { float f = (float)v; memcpy(data,&f,dataLen); }
+    else if (dataLen==8) { double f = (double)v; memcpy(data,&f,dataLen); }
+    else assert(0);
+  } else {
+    // we don't care about sign when writing - as it gets truncated
+    if (dataLen==1) { data[0] = (char)v; }
+    else if (dataLen==2) { *(short*)data = (short)v; }
+    else if (dataLen==4) { *(int*)data = (int)v; }
+    else if (dataLen==8) { *(long long*)data = (long long)v; }
+    else assert(0);
+  }
+
+  for (i=0;i<dataLen;i++) {
+    jsvStringIteratorSetChar(&it->it, data[i]);
+    if (dataLen!=1) jsvStringIteratorNext(&it->it);
+  }
+  if (dataLen!=1) it->hasAccessedElement = true;
+}
+
 void   jsvArrayBufferIteratorSetValue(JsvArrayBufferIterator *it, JsVar *value) {
   if (it->type == ARRAYBUFFERVIEW_UNDEFINED) return;
   assert(!it->hasAccessedElement); // we just haven't implemented this case yet
@@ -268,10 +294,10 @@ void   jsvArrayBufferIteratorSetValue(JsvArrayBufferIterator *it, JsVar *value)
   } else {
     JsVarInt v = jsvGetInteger(value);
     // we don't care about sign when writing - as it gets truncated
-    if (dataLen==1) { char c = (char)v; memcpy(data,&c,dataLen); }
-    else if (dataLen==2) { short c = (short)v; memcpy(data,&c,dataLen); }
-    else if (dataLen==4) { int c = (int)v; memcpy(data,&c,dataLen); }
-    else if (dataLen==8) { long long c = (long long)v; memcpy(data,&c,dataLen); }
+    if (dataLen==1) { data[0] = (char)v; }
+    else if (dataLen==2) { *(short*)data = (short)v; }
+    else if (dataLen==4) { *(int*)data = (int)v; }
+    else if (dataLen==8) { *(long long*)data = (long long)v; }
     else assert(0);
   }
 
@@ -282,6 +308,14 @@ void   jsvArrayBufferIteratorSetValue(JsvArrayBufferIterator *it, JsVar *value)
   if (dataLen!=1) it->hasAccessedElement = true;
 }
 
+void jsvArrayBufferIteratorSetByteValue(JsvArrayBufferIterator *it, char c) {
+  if (JSV_ARRAYBUFFER_GET_SIZE(it->type)!=1) {
+    assert(0);
+    return;
+  }
+  jsvStringIteratorSetChar(&it->it, c);
+}
+
 void jsvArrayBufferIteratorSetValueAndRewind(JsvArrayBufferIterator *it, JsVar *value) {
   JsvStringIterator oldIt = jsvStringIteratorClone(&it->it);
   jsvArrayBufferIteratorSetValue(it, value);
@@ -290,12 +324,6 @@ void jsvArrayBufferIteratorSetValueAndRewind(JsvArrayBufferIterator *it, JsVar *
   it->hasAccessedElement = false;
 }
 
-void   jsvArrayBufferIteratorSetIntegerValue(JsvArrayBufferIterator *it, JsVarInt value) {
-  // FIXME: Do this without the allocation!
-  JsVar *val = jsvNewFromInteger(value);
-  jsvArrayBufferIteratorSetValue(it, val);
-  jsvUnLock(val);
-}
 
 JsVar* jsvArrayBufferIteratorGetIndex(JsvArrayBufferIterator *it) {
   return jsvNewFromInteger((JsVarInt)it->index);

diff --git a/src/jsvariterator.h b/src/jsvariterator.h
@@ -207,6 +207,7 @@ JsVarFloat jsvArrayBufferIteratorGetFloatValue(JsvArrayBufferIterator *it);
 void   jsvArrayBufferIteratorSetValue(JsvArrayBufferIterator *it, JsVar *value);
 void   jsvArrayBufferIteratorSetValueAndRewind(JsvArrayBufferIterator *it, JsVar *value);
 void   jsvArrayBufferIteratorSetIntegerValue(JsvArrayBufferIterator *it, JsVarInt value);
+void   jsvArrayBufferIteratorSetByteValue(JsvArrayBufferIterator *it, char c); ///< special case for when we know we're writing to a byte array
 JsVar* jsvArrayBufferIteratorGetIndex(JsvArrayBufferIterator *it);
 bool   jsvArrayBufferIteratorHasElement(JsvArrayBufferIterator *it);
 void   jsvArrayBufferIteratorNext(JsvArrayBufferIterator *it);