Merge pull request #10 from zroug/16bit-performance

Bug fix in `Decoder::expand_strip` + greatly improved performance for 16 bit images

src/decoder/mod.rs

@@ -416,19 +416,18 @@ impl<R: Read + Seek> Decoder<R> {
             (ColorType:: RGB(8), DecodingBuffer::U8(ref mut buffer)) |
             (ColorType::RGBA(8), DecodingBuffer::U8(ref mut buffer)) |
             (ColorType::CMYK(8), DecodingBuffer::U8(ref mut buffer)) => {
-                try!(reader.read(&mut buffer[..bytes]))
+                try!(reader.read_exact(&mut buffer[..bytes]));
+                bytes
             }
             (ColorType::RGBA(16), DecodingBuffer::U16(ref mut buffer)) |
             (ColorType:: RGB(16), DecodingBuffer::U16(ref mut buffer)) => {
-                for datum in buffer[..bytes/2].iter_mut() {
-                    *datum = try!(reader.read_u16())
-                }
+                try!(reader.read_u16_into(&mut buffer[..bytes/2]));
                 bytes/2
             }
             (ColorType::Gray(16), DecodingBuffer::U16(ref mut buffer)) => {
-                for datum in buffer[..bytes/2].iter_mut() {
-                    *datum = try!(reader.read_u16());
-                    if self.photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                try!(reader.read_u16_into(&mut buffer[..bytes/2]));
+                if self.photometric_interpretation == PhotometricInterpretation::WhiteIsZero {
+                    for datum in buffer[..bytes/2].iter_mut() {
                         *datum = 0xffff - *datum
                     }
                 }
@@ -459,8 +458,8 @@ impl<R: Read + Seek> Decoder<R> {
             * self.height as usize
             * self.bits_per_sample.iter().count();
         let mut result = match self.bits_per_sample.iter().cloned().max().unwrap_or(8) {
-            n if n <= 8 => DecodingResult::U8(Vec::with_capacity(buffer_size)),
-            n if n <= 16 => DecodingResult::U16(Vec::with_capacity(buffer_size)),
+            n if n <= 8 => DecodingResult::U8(vec![0; buffer_size]),
+            n if n <= 16 => DecodingResult::U16(vec![0; buffer_size]),
             n => return Err(TiffError::UnsupportedError(TiffUnsupportedError::UnsupportedBitsPerChannel(n))),
         };
         if let Ok(config) = self.get_tag_u32(ifd::Tag::PlanarConfiguration) {
@@ -469,13 +468,6 @@ impl<R: Read + Seek> Decoder<R> {
                 config => return Err(TiffError::UnsupportedError(TiffUnsupportedError::UnsupportedPlanarConfig(config)))
             }
         }
-        // Safe since the uninitialized values are never read.
-        match result {
-            DecodingResult::U8(ref mut buffer) =>
-                unsafe { buffer.set_len(buffer_size) },
-            DecodingResult::U16(ref mut buffer) =>
-                unsafe { buffer.set_len(buffer_size) },
-        }
         let mut units_read = 0;
         for (i, (&offset, &byte_count)) in try!(self.get_tag_u32_vec(ifd::Tag::StripOffsets))
         .iter().zip(try!(self.get_tag_u32_vec(ifd::Tag::StripByteCounts)).iter()).enumerate() {
@@ -500,14 +492,8 @@ impl<R: Read + Seek> Decoder<R> {
                 break
             }
         }
-        // Shrink length such that the uninitialized memory is not exposed.
         if units_read < buffer_size {
-            match result {
-                DecodingResult::U8(ref mut buffer) =>
-                    unsafe { buffer.set_len(units_read) },
-                DecodingResult::U16(ref mut buffer) =>
-                    unsafe { buffer.set_len(units_read) },
-            }
+            return Err(TiffError::FormatError("Inconsistent sizes encountered.".to_string()));
         }
         if let Ok(predictor) = self.get_tag_u32(ifd::Tag::Predictor) {
             result = match FromPrimitive::from_u32(predictor) {

src/decoder/stream.rs

@@ -28,6 +28,14 @@ pub trait EndianReader: Read {
         }
     }
 
+    #[inline(always)]
+    fn read_u16_into(&mut self, buffer: &mut [u16]) -> Result<(), io::Error> {
+        match self.byte_order() {
+            ByteOrder::LittleEndian => <Self as ReadBytesExt>::read_u16_into::<LittleEndian>(self, buffer),
+            ByteOrder::BigEndian => <Self as ReadBytesExt>::read_u16_into::<BigEndian>(self, buffer)
+        }
+    }
+
     /// Reads an u32
     #[inline(always)]
     fn read_u32(&mut self) -> Result<u32, io::Error> {