Fix #18 - Handle malformed files with incorrect chunk sizes

Detect files that specify chunk sizes that are larger than the actual
file length. Ignore any chunks at the end of the file that are smaller
than the minimum chunk size (of 8 bytes).

src/WAV.jl

@@ -640,11 +640,17 @@ function wavread(io::IO; subrange=None, format="double")
  # Subtract the size of the format field from chunk_size; now it holds the size
  # of all the sub-chunks
  chunk_size -= 4
- while chunk_size > 0
+ # GitHub Issue #18: Check if there is enough data to read another chunk
+ const subchunk_header_size = 4 + sizeof(UInt32)
+ while chunk_size >= subchunk_header_size
  # Read subchunk ID and size
  subchunk_id = read(io, UInt8, 4)
  subchunk_size = read_le(io, UInt32)
- chunk_size -= 8 + subchunk_size
+ if subchunk_size > chunk_size
+ chunk_size = 0
+ break
+ end
+ chunk_size -= subchunk_header_size + subchunk_size
  # check the subchunk ID
  if subchunk_id == b"fmt "
  fmt = read_format(io, subchunk_size)

test/runtests.jl

@@ -43,6 +43,41 @@ let
  @assert nbits == 32
 end
 
+## malformed subchunk header, GitHub Issue #18
+let
+ # Create a malformed WAV file
+ samples = rand(Float32, (10, 1))
+ io = IOBuffer()
+
+ const compression = WAV.get_default_compression(samples)
+ const nbits = WAV.get_default_precision(samples, compression)
+ const ext = WAV.WAVFormatExtension()
+
+ fmt = WAV.WAVFormat()
+ fmt.compression_code = compression
+ fmt.nchannels = size(samples, 2)
+ fmt.sample_rate = 8000
+ fmt.nbits = ceil(Integer, nbits / 8) * 8
+ fmt.block_align = fmt.nbits / 8 * fmt.nchannels
+ fmt.bps = fmt.sample_rate * fmt.block_align
+ fmt.data_length = size(samples, 1) * fmt.block_align
+
+ WAV.write_header(io, fmt, 37) # 37 instead of 36 is the broken part
+ WAV.write_format(io, fmt)
+
+ # write the data subchunk header
+ WAV.write(io, b"data")
+ WAV.write_le(io, fmt.data_length) # UInt32
+ WAV.write_data(io, fmt, ext, samples)
+
+ seek(io, 0)
+ y, fs, nbits, extra = WAV.wavread(io, format="native")
+ @assert fs == 8000
+ @assert nbits == 32
+ @assert extra == None
+ @assert samples == y
+end
+
 let
  tmp=rand(Float64,(10,2))
  io = IOBuffer()