Merge pull request #91 from carlopi/append_extension_metadata_wasm_co…

…mpatible

Add duckdb_signature as a valid Wasm custom section

scripts/append_extension_metadata.py

@@ -1,6 +1,25 @@
 import argparse
 import shutil
 
+def start_signature():
+ # This is needed so that Wasm binaries are valid
+ encoded_string = ''.encode('ascii')
+ # 0 for custom section
+ encoded_string += int(0).to_bytes(1)
+ # 213 in hex = 531 in decimal, total lenght of what follows (1 + 16 + 2 + 8x32 + 256)
+ # [1(continuation) + 0010011(payload) = \x93 -> 147, 0(continuation) + 10(payload) = \x04 -> 4]
+ encoded_string += int(147).to_bytes(1)
+ encoded_string += int(4).to_bytes(1)
+ # 10 in hex = 16 in decimal, lenght of name, 1 byte
+ encoded_string += int(16).to_bytes(1)
+ # the name of the WebAssembly custom section, 16 bytes
+ encoded_string += b'duckdb_signature'
+ # 1000 in hex, 512 in decimal
+ # [1(continuation) + 0000000(payload) = -> 128, 0(continuation) + 100(payload) -> 4],
+ encoded_string += int(128).to_bytes(1)
+ encoded_string += int(4).to_bytes(1)
+ return encoded_string
+
 def padded_byte_string(input):
  encoded_string = input.encode('ascii')
  encoded_string += b'\x00' * (32 - len(encoded_string))
@@ -35,6 +54,7 @@ def main():
  # Then append the metadata to the tmp file
  print(f" - Metadata:")
  with open(OUTPUT_FILE_TMP, 'ab') as file:
+ file.write(start_signature())
  print(f" - FIELD8 (unused) = EMPTY")
  file.write(padded_byte_string(""))
  print(f" - FIELD7 (unused) = EMPTY")