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Data formats

Procedures for handling CSV and delimiter-separated values (DSV). For INI file support, see IniFilesCowan. For JSON support, see SRFI 180.

Input ports default to (current-input-port), output ports to (current-output-port).

Comma-separated values.

The external representation of a CSV (comma-separated values) stream is defined by RFC 4180, with the following deviations:

  • CR characters are ignored on input (so LF is a sufficient line break) but generated on output.

  • No special treatment is given to the first line. It is up to applications to decide if it is a header line or not.

  • No attempt is made to ensure that all records have the same number of fields, either on input or on output.

  • Processing is done in terms of characters, not bytes.

The internal representation of each record is a list of strings that represent the fields of that record. There is no representation of whole files.

(make-csv-generator [port])

Returns a SRFI 158 generator which when invoked reads a record from port and returns it in the internal representation. When port returns an end of file object, the generator closes port and returns the object.

(make-csv-accumulator [port])

Returns a SRFI 158 accumulator which when invoked with one argument that is the internal representation of a record writes the corresponding external representation to port, returning an unspecified value. When invoked on an end-of-file object, the generator closes port and returns the end of file object.

Delimiter-separated values

Delimiter-separated values (DSVs) are a variant of comma-separated values, and the internal representation is the same. However, the delimiter may be any character, and the end of a record is always a newline and vice versa. The following characters are escaped by a backslash sequence:

  • The delimiter is escaped by preceding it with a backslash
  • A blackslash is escaped as \\
  • A newline is escaped as \n
  • A tab is escaped as \t

All other backslashes are treated literally.

(make-dsv-generator delim [port])

The semantics are the same as the semantics of make-csv-generator, except that delim when unescaped delimits fields. As a special case, if delim is a single space, any consecutive sequence of either spaces or tabs jointly treated as the delimiter.

(make-dsv-accumulator delim [port])

The semantics are the same as the semantics of make-csv-accumulator, except that delim is used to delimit fields.