To work with mixed binary/textual I/O, the following R6RS-compatible procedures are proposed:

• (read-blob <length> [<input-port>])
• (read-blob! <blob> <length> [<input-port>])
• (write-blob <blob> [<output-port>])
• (write-partial-blob <blob> <from> <to> [<output-port>])
• (utf8->string <blob>)
• (string->utf8 <string>)

It's an error to pass invalid bytes to utf8->string. A plausible recovery strategy is to convert each invalid byte into a U+FFFD character.

Write-partial-blob would be merged into write-blob if the same is done for blob copying.