6.44.3.4 Extended textual input functions

Function: get-char port

Return the EOF object, the would–block object or a character:

• If a complete character is available before the next end of file: return that character and update the input port to point past the character.
• If an end of file is reached before any character is read: return the EOF object.
• If the underlying device is in non–blocking mode and no full character is available: return the would–block object.

Function: read-char

Function: read-char port

Like get-char.

Function: lookahead-char port

Like get-char, but it does not update port to point past the character.

Function: peek-char

Function: peek-char port

Like lookahead-char.

Function: get-string-n port requested-count

Return the EOF object, the would–block object or a string and update the input port to point past the consumed characters:

• If requested-count characters are available before end of file: return a string consisting of those requested-count characters.
• If fewer than requested-count characters are available before an end of file, but one or more characters can be read: return a string containing those characters.
• If no characters can be read before an end of file: return the EOF object.
• If the underlying device is in non–blocking mode and no characters are available: return the would–block object.

Function: get-string-n! port dst.str dst.start count

Return the EOF object, the would–block object or a string and update the input port to point past the consumed characters:

• If count characters are available before an end of file: they are written into DST.STR starting at index DST.START, and count is returned.
• If fewer than count characters are available before an end of file, but one or more can be read: those characters are written into dst.str starting at index dst.start and the number of characters actually read is returned as an exact integer object.
• If no characters can be read before an end of file: the EOF object is returned.
• If the underlying device is in non–blocking mode and fewer than count characters are available before a would–block condition, but one or more can be read: those characters are written into dst.str starting at index dst.start and the number of characters actually read is returned as an exact integer object.
• If the underlying device is in non–blocking mode and no characters are available: return the would–block object.

Function: get-string-all port

Return the EOF object or a string and update the input port to point past the consumed characters:

• If characters are available before the end of file: a string containing all the characters decoded from that data is returned. Further reading from the port will return the EOF object.
• If no character precedes the end of file: the EOF object is returned.

Even when the underlying device is in non–blocking mode: this function attempts to read input until the EOF is found.

Function: get-string-some port

Return the EOF object, the would–block object or a string and update the input port to point past the consumed characters:

• If characters become available before the end of file: return a freshly allocated string containing the initial available characters (at least one), and update port to point just past these characters.
• If no input characters are available before the end of file: the EOF object is returned.
• If no input characters are available before a would–block condition: the would–block object is returned.