Switch to in-place addition for efficiency

Modify the arrays in place.

Author: tompollard

wfdb/io/_signal.py

@@ -2319,11 +2319,10 @@ def wr_dat_file(
 
  if fmt == "80":
  # convert to 8 bit offset binary form
- d_signal = d_signal + 128
- # Concatenate into 1D
- d_signal = d_signal.reshape(-1)
- # Convert to un_signed 8 bit dtype to write
- b_write = d_signal.astype("uint8")
+ d_signal += 128
+
+ # Convert to unsigned 8 bit dtype to write (and flatten if necessary)
+ b_write = d_signal.astype("uint8").reshape(-1)
 
  elif fmt == "212":
  # Each sample is represented by a 12 bit two's complement
@@ -2336,7 +2335,7 @@ def wr_dat_file(
  # repeated for each successive pair of samples.
 
  # convert to 12 bit two's complement
- d_signal[d_signal < 0] = d_signal[d_signal < 0] + 4096
+ d_signal[d_signal < 0] += 4096
 
  # Concatenate into 1D
  d_signal = d_signal.reshape(-1)
@@ -2384,8 +2383,8 @@ def wr_dat_file(
  # Convert to un_signed 8 bit dtype to write
  b_write = b_write.astype("uint8")
  elif fmt == "24":
- # convert to 24 bit two's complement
- d_signal[d_signal < 0] = d_signal[d_signal < 0] + 16777216
+ # convert to 32 bit two's complement (as int24 not an option)
+ d_signal = d_signal.astype(np.uint32)
  # Split samples into separate bytes using binary masks
  b1 = d_signal & [255] * tsamps_per_frame
  b2 = (d_signal & [65280] * tsamps_per_frame) >> 8