Add support for value labels on long string variables.

[pspp-builds.git] / doc / dev / system-file-format.texi

diff --git a/doc/dev/system-file-format.texi b/doc/dev/system-file-format.texi
index 3e764c8ce714099f1becf877c927681911b23a54..0358961bab9aa39426cc2233048ae478b56e86db 100644 (file)
--- a/doc/dev/system-file-format.texi
+++ b/doc/dev/system-file-format.texi
@@ -96,6 +96,8 @@ Each type of record is described separately below.
 * Variable Display Parameter Record::
 * Long Variable Names Record::
 * Very Long String Record::
+* Character Encoding Record::
+* Long String Value Labels Record::
 * Data File and Variable Attributes Records::
 * Miscellaneous Informational Records::
 * Dictionary Termination Record::
@@ -397,6 +399,11 @@ Format types are defined as follows:
 @node Value Labels Records
 @section Value Labels Records
 
+The value label records documented in this section are used for
+numeric and short string variables only.  Long string variables may
+have value labels, but their value labels are recorded using a
+different record type (@pxref{Long String Value Labels Record}).
+
 The value label record has the following format:
 
 @example
@@ -457,7 +464,7 @@ A list of dictionary indexes of variables to which to apply the value
 labels (@pxref{Dictionary Index}).  There are @code{var_count}
 elements.
 
-String variables wider than 8 bytes may not have value labels.
+String variables wider than 8 bytes may not be specified in this list.
 @end table
 
 @node Document Record
@@ -546,9 +553,14 @@ Compression code.  Always set to 1.
 Machine endianness.  1 indicates big-endian, 2 indicates little-endian.
 
 @item int32 character_code;
+@anchor{character-code}
 Character code.  1 indicates EBCDIC, 2 indicates 7-bit ASCII, 3
 indicates 8-bit ASCII, 4 indicates DEC Kanji.
 Windows code page numbers are also valid.
+
+Experience has shown that in many files, this field is ignored or incorrect.
+For a more reliable indication of the file's character encoding
+see @ref{Character Encoding Record}.
 @end table
 
 @node Machine Floating-Point Info Record
@@ -792,6 +804,118 @@ After the last tuple, there may be a single byte 00, or @{00, 09@}.
 The total length is @code{count} bytes.
 @end table
 
+@node Character Encoding Record
+@section Character Encoding Record
+
+This record, if present, indicates the character encoding for string data,
+long variable names, variable labels, value labels and other strings in the
+file.
+
+@example
+/* @r{Header.} */
+int32               rec_type;
+int32               subtype;
+int32               size;
+int32               count;
+
+/* @r{Exactly @code{count} bytes of data.} */
+char                encoding[];
+@end example
+
+@table @code
+@item int32 rec_type;
+Record type.  Always set to 7.
+
+@item int32 subtype;
+Record subtype.  Always set to 20.
+
+@item int32 size;
+The size of each element in the @code{encoding} member. Always set to 1.
+
+@item int32 count;
+The total number of bytes in @code{encoding}.
+
+@item char encoding[];
+The name of the character encoding.  Normally this will be an official IANA characterset name or alias.
+See @url{http://www.iana.org/assignments/character-sets}.
+@end table
+
+This record is not present in files generated by older software.
+See also @ref{character-code}.
+
+@node Long String Value Labels Record
+@section Long String Value Labels Record
+
+This record, if present, specifies value labels for long string
+variables.
+
+@example
+/* @r{Header.} */
+int32               rec_type;
+int32               subtype;
+int32               size;
+int32               count;
+
+/* @r{Repeated up to exactly @code{count} bytes.} */
+int32               var_name_len;
+char                var_name[];
+int32               var_width;
+int32               n_labels;
+long_string_label   labels[];
+@end example
+
+@table @code
+@item int32 rec_type;
+Record type.  Always set to 7.
+
+@item int32 subtype;
+Record subtype.  Always set to 21.
+
+@item int32 size;
+Always set to 1.
+
+@item int32 count;
+The number of bytes following the header until the next header.
+
+@item int32 var_name_len;
+@itemx char var_name[];
+The number of bytes in the name of the variable that has long string
+value labels, plus the variable name itself, which consists of exactly
+@code{var_name_len} bytes.  The variable name is not padded to any
+particular boundary, nor is it null-terminated.
+
+@item int32 var_width;
+The width of the variable, in bytes, which will be between 9 and
+32767.
+
+@item int32 n_labels;
+@itemx long_string_label labels[];
+The long string labels themselves.  The @code{labels} array contains
+exactly @code{n_labels} elements, each of which has the following
+substructure:
+
+@example
+int32               value_len;
+char                value[];
+int32               label_len;
+char                label[];
+@end example
+
+@table @code
+@item int32 value_len;
+@itemx char value[];
+The string value being labeled.  @code{value_len} is the number of
+bytes in @code{value}; it is equal to @code{var_width}.  The
+@code{value} array is not padded or null-terminated.
+
+@item int32 label_len;
+@itemx char label[];
+The label for the string value.  @code{label_len}, which must be
+between 0 and 120, is the number of bytes in @code{label}.  The
+@code{label} array is not padded or null-terminated.
+@end table
+@end table
+
 @node Data File and Variable Attributes Records
 @section Data File and Variable Attributes Records