X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fdev%2Fsystem-file-format.texi;h=484fbb43f1eca08fc089bd0f5ec171215f279403;hb=80527716392c066fdf72f37729c42089a2174bae;hp=ff4c60345102e879598d4e26d27915c9910e6735;hpb=f5e337fe69d0ee75e26ffc4b2c571234e73fa6dd;p=pspp

diff --git a/doc/dev/system-file-format.texi b/doc/dev/system-file-format.texi
index ff4c603451..484fbb43f1 100644
--- a/doc/dev/system-file-format.texi
+++ b/doc/dev/system-file-format.texi
@@ -161,6 +161,11 @@ Document record, if present.
 Extension (type 7) records, in ascending numerical order of their
 subtypes.
 
+System files written by SPSS include at most one of each kind of
+extension record.  This is generally true of system files written by
+other software as well, with known exceptions noted below in the
+individual sections about each type of record.
+
 @item
 Dictionary termination record.
 
@@ -217,6 +222,12 @@ pspp 0.1.4 - sparc-sun-solaris2.5.2}.  The string is truncated if it
 would be longer than 60 characters; otherwise it is padded on the right
 with spaces.
 
+The product name field allow readers to behave differently based on
+quirks in the way that particular software writes system files.
+@xref{Value Labels Records}, for the detail of the quirk that the PSPP
+system file reader tolerates in files written by ReadStat, which has
+@code{https://github.com/WizardMac/ReadStat} in @code{prod_name}.
+
 @anchor{layout_code}
 @item int32 layout_code;
 Normally set to 2, although a few system files have been spotted in
@@ -227,8 +238,8 @@ file's integer endianness (@pxref{System File Format}).
 Number of data elements per case.  This is the number of variables,
 except that long string variables add extra data elements (one for every
 8 characters after the first 8).  However, string variables do not
-contribute to this value beyond the first 255 bytes.   Further, system
-files written by some systems set this value to -1.  In general, it is
+contribute to this value beyond the first 255 bytes.   Further, some
+software always writes -1 or 0 in this field.  In general, it is
 unsafe for systems reading system files to rely upon this value.
 
 @item int32 compression;
@@ -519,6 +530,14 @@ 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}).
 
+ReadStat (@pxref{File Header Record}) writes value labels that label a
+single value more than once.  In more detail, it emits value labels
+whose values are longer than string variables' widths, that are
+identical in the actual width of the variable, e.g.@: labels for
+values @code{ABC123} and @code{ABC456} for a string variable with
+width 3.  For files written by this software, PSPP ignores such
+labels.
+
 The value label record has the following format:
 
 @example
@@ -600,7 +619,8 @@ char                lines[][80];
 Record type.  Always set to 6.
 
 @item int32 n_lines;
-Number of lines of documents present.
+Number of lines of documents present.  This should be greater than
+zero, but ReadStats writes system files with zero @code{n_lines}.
 
 @item char lines[][80];
 Document lines.  The number of elements is defined by @code{n_lines}.
@@ -1360,7 +1380,7 @@ The total number of bytes in @code{attributes}.
 @item char attributes[];
 The attributes, in a text-based format.
 
-In record type 17, this field contains a single attribute set.  An
+In record subtype 17, this field contains a single attribute set.  An
 attribute set is a sequence of one or more attributes concatenated
 together.  Each attribute consists of a name, which has the same
 syntax as a variable name, followed by, inside parentheses, a sequence
@@ -1372,13 +1392,17 @@ way to embed a line feed in a value.  There is no distinction between
 an attribute with a single value and an attribute array with one
 element.
 
-In record type 18, this field contains a sequence of one or more
+In record subtype 18, this field contains a sequence of one or more
 variable attribute sets.  If more than one variable attribute set is
 present, each one after the first is delimited from the previous by
 @code{/}.  Each variable attribute set consists of a long
 variable name,
 followed by @code{:}, followed by an attribute set with the same
-syntax as on record type 17.
+syntax as on record subtype 17.
+
+System files written by @code{Stata 14.1/-savespss- 1.77 by
+S.Radyakin} may include multiple records with subtype 18, one per
+variable that has variable attributes.
 
 The total length is @code{count} bytes.
 @end table